Category: 8. Health

Introduction

Uridine is a pyrimidine nucleoside composed of uracil and ribose, which can be used not only to synthesize genetic material such as RNA and DNA, but also to provide a material basis for various metabolic processes.¹ In the human body, uridine is present in the blood and cerebrospinal fluid. Since most tissues are unable to synthesize uridine independently, they rely on the circulatory system to uptake exogenous uridine to maintain basal cellular functions. Therefore, blood uridine homeostasis has a great impact on systemic metabolism, and the appropriate uridine level is crucial for health maintenance, while the abnormal uridine concentration can lead to the occurrence and development of various diseases.² Uridine, as an endogenous metabolite, is considered safe. For the aforementioned reasons, uridine is also widely used in clinical settings. Uridine, as an important biomolecule, holds great potential in maintaining health and treating diseases. Here, we focus on the vital role of uridine in health, disease, and therapy, as well as the innovative advancements in related research, with the aim of providing insights into the current state of research and future perspectives on relevant topics.

The Synthesis and Catabolism of Uridine

De novo synthesis, salvage synthesis, and catabolism are the three metabolic pathways of pyrimidine nucleotide metabolism. Uridine is part of the pyrimidine nucleotide family and can be synthesized intracellularly through de novo synthesis. The de novo synthesis of uridine originates from glutamine and aspartate, with the first step catalyzed by CAD. CAD is a multi-domain enzyme composed of carbamoyl-phosphate synthase 2 (CPSII), aspartate tran-scarbamoylase (ATC) and dihydroorotase (DHO). In the de novo synthesis pathway, CAD catalyzes glutamine and aspartate to produce intermediate metabolites, namely carbamoyl phosphate, aspartyl carbamoyl phosphate, and dihydroorotate. This process leads to the formation of the pyrimidine ring. Subsequently, under the catalysis of dihydroorotate dehydrogenase (DHODH), dihydroorotate is converted into the important intermediate, orotate. Then, orotate phosphoribosyltransferase and orotidine 5’-phosphate decarboxylase sequentially transform orotate into orotidine monophosphate (OMP) and uridine monophosphate (UMP). UMP is dephosphorylated by a nucleotidase to uridine (Figure 1A).

Figure 1 The synthesis and catabolism of uridine. (A) De novo synthesis; (B) salvage pathway, ENTs: the SLC29 family balanced nucleoside transporters; CNTs: the SLC28 family concentrated nucleoside transporters; (C) catabolism. Abbreviation: TCA, tricarboxylic acid.

In addition to the de novo synthesis pathway, the pyrimidine salvage synthesis pathway is also an important way to obtain uridine. This pathway utilizes free pyrimidine bases or pyrimidine nucleosides and converts them into uridine nucleotides through fewer steps.This pathway is particularly important in certain tissues, such as the brain and bone marrow, which may lack the capacity of the de novo synthetic pathway. Uridine can be obtained directly from the decomposition of UTP, CTP, and this process is reversible. When the endogenous synthesis supply is insufficient, uridine is mainly used through exogenous ingestion to maintain its homeostasis to ensure normal cell growth and function. The SLC28 family concentrated nucleoside transporter (CNT) and the SLC29 family balanced nucleoside transporter (ENT) are two types of nucleoside transport family proteins currently known.³ The CNT family includes three transporters: hCNT1, hCNT2, and hCNT3 (corresponding to SLC28A1, SLC28A2, and SLC28A3, respectively). These transporters are sodium ion-dependent, and they use an electrochemical gradient of sodium ions across the membrane to drive nucleoside transport. The ENT family consists of four transporters: hENT1, hENT2, hENT3, and hENT4 (corresponding to SLC29A1, SLC29A2, SLC29A3, and SLC29A4, respectively). These transporters are of the sodium-independent type and they undergo energy-independent nucleoside transport independent of the sodium gradient. CNT and ENT are two important families of nucleoside transporters that play key roles in nucleoside transport both inside and outside of the cell.^4,5 In the salvage synthesis pathway, uridine-cytidine kinase 2 (UCK2) plays a key role in phosphorylation pyrimidine nucleosides (uridine and cytidine) into the corresponding nucleoside monophosphates (UMP and CMP) for the subsequent generation of UDP/UTP, CDP/CTP, etc (Figure 1B).

Notably, the maintenance of uridine homeostasis also requires the proper catabolic involvement of uridine. During uridine catabolism, uridine phosphorylase (UPase) plays a leading role.⁶ There are two homologous forms of UPase in vertebrates, namely UPase1 (encoded by the UPP1 gene) and UPase2 (encoded by the UPP2 gene). Among both enzymes, UPase1 appears to play a more important role in maintaining uridine homeostasis, being ubiquitously expressed, and knockout of the UPP1 gene or weakening of UPase1 enzyme activity increases uridine levels in plasma and tissues. The UPase2 is considered as a liver-specific protein, and the UPase2 enzyme activity can also significantly affect the level of endogenous uridine in the liver, which is also indispensable for the pyrimidine salvage pathway. Uridine can be degraded by UPase to uracil, while the latter can be further decomposed into dihydrouracil and N-carbamyl-β-alanine by dihydropyrimidine dehydrogenase and dihydropyrimidine enzyme, and then converted to β-alanine and acetyl-CoA by β-urea alanase (Figure 1C). β-Alanine can enter other tissues or be excreted, while acetyl-Coenzyme A can increase the acetylation level of intracellular proteins, so uridine can mediate cellular pathophysiological processes at the post-translational modification level of proteins.

The Role of Uridine in Health Maintenance

Antioxidant Properties of Uridine

Uridine is a nucleoside in an RNA structure that consists of a uracil base and a ribose. It not only plays an important role in nucleic acid synthesis, but also shows a potential importance in maintaining the cellular redox balance and antioxidant protection. Uridine has been reported to induce changes in the ratios of NAD/NADH and NADP/NADPH. These are essential coenzymes for cellular metabolism, redox and antioxidant processes, and are key factors in maintaining the cellular redox state.^7,8 In addition, uridine also regulates antioxidant enzyme activity and mitochondrial function to maintain its antioxidant properties. Uridine was found to enhance the activity of antioxidant enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GPX), thus enhancing cellular defense against ROS.^9–11 Mitochondria are the main ROS producing sites in cells, and uridine is thought to regulate the mitochondrial respiratory chain through DHODH to normalize mitochondrial structure and function. Additionally, the uridine derivative UDP, acting as an activator of the mitochondrial ATP-dependent potassium channel (mitoK_ATP), can activate potassium cycling in mitochondria, resulting in mild uncoupling of mitochondria and inhibition of ROS production.^10,12–14 Uridine is also able to affect multiple signal transduction pathways including NF- κB and MAPKs, Nrf 2, which are closely involved in the cellular response to oxidative stress. By regulating these pathways, uridine helps to maintain the antioxidant state within the cells.^11,15–17 Moreover, although uridine is relatively weak in its direct free radical scavenging ability, it can indirectly participate in ROS clearance through conversion to other antioxidant molecules.¹⁸

The Role of Uridine in Immune Regulation

Uridine has an important role in immune regulation. Uridine is involved in the regulation of immune signaling pathways, which can affect the production and release of inflammatory cytokines, such as TNF-α and IL-1β, thereby alleviating the inflammatory response and hyperactivation of the immune system.¹⁷ Increasing evidence suggests that uridine is critical for maintaining cellular function and energy metabolism.⁷ Uridine also has a regulatory effect on the energy metabolism of immune cells, which is crucial for maintaining the metabolic activity of immune cells and enhancing their energy supply and functional performance.¹⁹

Uridine can modulate the function of the immune system and enhance the body’s immunity,²⁰ which may be related to the important role of uridine in maintaining the normalization of mitochondrial structure and function. Mitochondria occupy a critical position in immunobiology, not only in terms of bioenergetic function, but also in the metabolism and signaling of immune cells.²¹ Mitochondria are regarded as the main metabolic regulators of T cells because they can regulate different stages of the adaptive response of T cells.²² The immune system, and especially the T cells, requires a functional mitochondrial respiratory chain.²³ Uridine is thought to regulate the mitochondrial respiratory chain through DHODH to normalize the mitochondrial structure and function. The study by Battaglia S et al²⁴ found that uridine supplementation protected the proliferative ability of T cells from mitochondrial toxic antibiotics.

In addition to the classical role of genetic material synthesis, uridine can also be converted into a variety of other bioactive molecules to play multitarget roles. A number of studies have shown that extracellular nucleotides (ATP, UDP, etc.) can act as immunomodulatory mediators during inflammatory responses by binding to P2 purinergic receptors (such as P2Y6), which can be released by damaged cells to activate the immune response under inflammatory conditions.^25–27 Several studies^28,29 also demonstrated that uridine abolished mitochondrial toxicity caused by antiretroviral therapy in HIV infected patients. These findings undoubtedly suggest a close association between uridine and immunity.

Neuroprotective Effects of Uridine

The protective effect of uridine on the nervous system is multifaceted. First, the anti-inflammatory and antioxidant properties of uridine can protect a variety of cells, including nerve cells, from inflammation and oxidative damage.³⁰ Secondly, uridine is the precursor of CDP-choline synthesis.³¹ In the nervous system, CDP-choline is not only involved in the construction and maintenance of cell membranes, but is also associated with the synthesis of neurotransmitters.^32,33 For example, choline is the precursor for the synthesis of acetylcholine (ACh), which is a key neurotransmitter in the central and peripheral nervous systems, involving various cognitive functions such as learning, memory, and attention. Moreover, CDP-choline may also have effects on neurodegenerative diseases and repair processes after nerve injury by affecting biological lipid metabolism and cell signaling in nerve cells.^34–36 CDP-choline, in animal models of demyelinating diseases, such as multiple sclerosis, shows the potential to promote remyelination and nerve repair.³⁷

In addition, a study³⁸ noted that uridine protects cortical neurons from death caused by glucose deprivation, which may involve the role of uridine phosphorylase. This suggests that uridine may exert neuroprotective effects through specific enzymatic action. Uridine was also able to mitigate morphine-induced conditioned place preference and to modulate glutamate/γ-aminobutyric acid levels in the mouse prefrontal cortex.³⁹ Uridine can also have antiepileptic effects on seizures by regulating dopamine release and receptor expression.^40,41 Alternatively, the neuroprotective effects of uridine is reflected in the role of uridine in energy metabolism and cellular repair processes. It enhances energy supply by enhancing mitochondrial function and protects neurons from metabolic stress.¹⁵ The neuroprotective effect of uridine was also correlated with reduced apoptosis.^30,42 Overall, the neuroprotective effect of uridine is a multi-faceted, multi-level process involving multiple links, including antioxidant defense, immune regulation, energy metabolism and cellular repair, and anti-apoptosis. The role of uridine in health maintenance were shown in Figure 2.

Figure 2 The role of uridine in health maintenance.

The Crosstalk Between Uridine and Substance Metabolism

Uridine can play a role in various biosynthetic processes by being converted into other bioactive molecules, thus possessing multiple biological functions.¹⁸ On the one hand, uridine can participate in protein glycosylation through the formation of uridine diphosphate N-acetylglucosamine (UDP-GlcNAc).⁴³ On the other hand, uridine can also promote the biosynthesis of cell membrane phospholipids by converting it to cytidine triphosphate (CTP).⁴⁴ In addition, uridine also regulates biological rhythm, including body temperature rhythm and circadian rhythm.⁴⁵ As an important intermediate material in the biological network of the body, uridine is mutually interactive and complex (Figure 3).

Figure 3 The crosstalk between uridine and substance metabolism.

Uridine and Protein Metabolism

O-acetylglucosamine (O-GlcNAc) can modify proteins in various metabolic pathways. Uridine can be converted into UDP-GlcNAc (a protein O-GlcNAc substrate), which is then attached to the hydroxyl group on the serine or threonine residues of the protein chain to form the O-GlcNAc modification.^46,47 This is a highly dynamic and ubiquitous mode of protein modification that is rapidly emerging as a key regulator of key biological processes. The role of uridine in O-GlcNAc modification is closely related to protein phosphorylation.⁴⁸ The interaction between these two modifications can affect protein function and lead to the occurrence and development of related diseases.

In addition to UDP-GlcNAc, the synthetic product of uridine, its degradation product acetyl-coenzyme A also plays an important role in protein metabolism.⁷ In addition to the synthesis and degradation products that can link to protein metabolism, uridine itself can also induce the changes in NAD/NADH and NADP/NADPH ratios.^7,8 This may activate the NAD-regulated deacetylases, leading to increased protein deacetylation. It should also be noted that the catabolic amino acids of proteins can also provide a carbon or nitrogen source for uridine synthesis, and influence uridine concentration through different metabolic pathways.

Uridine and Lipid Metabolism

The relationship between uridine as a pyrimidine metabolism intermediate and lipid metabolism is also widely confirmed. DHODH is a mitochondrial membrane-bound respiratory chain coupling enzyme that plays an important role in the process of pyrimidine metabolism.⁴⁹ Weakening of the DHODH enzymatic activity can cause microvesicular fat deformation, and this condition can be relieved after uridine supplementation.⁵⁰ Notably, uridine did not have any effect on DHODH enzyme activity, which most likely reversed lactate-induced intracellular lipid accumulation in a way other than regulating DHODH enzyme activity.⁷

Uridine and fat are closely related, and both are metabolized through the hepatic-biliary pathway. Uridine is synthesized in adipose tissue during fasting and its levels affect the stability of blood lipids. Short-term uridine supplementation prevents drug-induced hepatic fat accumulation, while long-term exogenous uridine supplementation causes fatty liver disease.² It has been reported that long-term uridine supply suppresses the expression of liver-specific fatty acid binding protein 1 (FABP1), which may be an important cause of fatty liver, namely, long-term uridine supply may be a driver of fatty liver.⁵¹ Additionally, the X box-binding protein 1 (Xbp1) plays a role in uridine metabolism and is activated in response to ER stress in adipose tissue. Its overexpression can increase uridine synthesis and inhibit fat accumulation.^52,53 Another example of uridine levels affecting lipid stability is that inhibition of UPase2 suppresses hepatic lipid accumulation caused by drugs by increasing the concentration of endogenous hepatic uridine.²

In addition, it has been shown that uridine can alter the ratio of NAD⁺/NADH and NADP ⁺ / NADPH in the liver, and regulate the protein acetylation profile to regulate lipid metabolism.⁷ In conclusion, uridine is closely related to lipid metabolism, and the specific mechanism is complex and still needs further study.

Uridine and Glucose Metabolism

Uridine as a UTP and UDP-glucose precursor can activate glycogen synthesis.^15,54 Leptin is a protein hormone secreted by adipose tissue. Its main function is to regulate energy balance, inhibit appetite, and reduce fat storage in adipocytes. Uridine has been reported to influence glucose metabolism through leptin. Namely, uridine supplementation improved glucose tolerance in mice on a high-fat diet. While in the absence of leptin, uridine supplementation worsened glucose tolerance.¹ Uridine has also been reported to affect insulin signaling and glucose tolerance profiles.³¹ Furthermore, prolonged uridine supplementation leads to elevated blood glucose levels and insulin resistance. However, under high-fat diet conditions, uridine supplementation reduces blood glucose levels. This suggests that the regulation of glucose metabolism by uridine is influenced by the calorie levels in the diet.⁵⁵ The increased leptin levels associated with a high-fat diet may contribute to the dual effects of uridine on glucose tolerance. In addition, it has been shown that high-dose uridine supplementation may reduce rodent body temperature,⁵⁶ and uridine is likely a driving force of thermoregulation during fasting and refeeding,¹ which is undoubtedly another strong evidence of the association of uridine and glucose metabolism.

The Role of Uridine in the Disease

The continuous and stable circulating uridine level is the basis of the normal operation of various biological processes of the body, and the destruction of uridine homeostasis is bound to affect this, and then lead to disease.⁵⁷ The association of uridines with the disease is presented in Table 1.

Table 1 Urine in Disease

Metabolic Diseases

Fatty Liver Disease and Diabetes Mellitus

The liver is the organ most affected by ectopic lipid accumulation.⁵⁸ Disruption of uridine homeostasis is closely associated with the accumulation of hepatic lipids.⁷ Exogenous uridine supplementation inhibited hepatic steatosis induced by several drugs, such as tacacitabine, fenofibrate, and tamoxifen.^2,31 Alternatively, in a mouse model, uridine supplementation alleviated high-fat diet-induced obesity and non-alcoholic fatty liver disease by regulating the gut microbiota.⁵⁹

The development of diabetes is closely associated with decreased sensitivity to insulin signaling, and studies have shown that uridine can increase insulin sensitivity by inhibiting inflammatory responses and oxidative stress.⁶⁰ At the same time, uridine reduced blood glucose levels and improved glucose tolerance and diabetes-induced myocardial injury in diabetic mice. Mechanistically, uridine is protective against diabetes-mediated damage to cardiac mitochondrial function and structure, and against disruption of the mitochondrial quality control system in the diabetic heart.⁶¹

Diabetic vasculopathy is one of the main complications of diabetes. Its cause is that long-term hyperglycemia leads to abnormal expression of cytokines that maintain vascular homeostasis, resulting in adverse reactions such as inflammation and oxidative stress, causing vascular endothelial structural changes, and then dysfunction. According to the occurrence mechanism of vascular lesions, the effect of uridine on diabetic vascular complications is closely related to the endothelial cell disorders. Endothelial cell dysfunction is a pathophysiological feature leading to large and microvascular complications of diabetes.⁵⁵ Uridine participates in protein O-GlcNAc modification through the formation of UDP-GlcNAc. O-GlcNAcylation is involved in the regulation of various biological processes, including nuclear transport, translation, transcription, signal transduction, cytoskeletal reorganization, proteasomal degradation, and apoptosis.^62,63 While increased O-GlcNAc levels are thought to be a pathological contributor to glucose toxicity and insulin resistance, a major hallmark of diabetes and diabetes-related cardiovascular complications.^64,65

Diabetic neuropathy is one of the common chronic complications of diabetes mellitus. It is due to the damage to the nervous system caused by prolonged hyperglycemia. This lesion can affect the nerves in many parts of the body, including the limbs, autonomic nerves and so on. Cytidine triphosphate (CTP), a derivative of uridine, promotes the resynthesis of phosphatidylinositol, an important neurocell membrane component. Thus uridine can restore nerve fiber function in diabetic patients through a mechanism of CTP synthesis. On the other hand, in the presence of glucose accumulation in the nerves of diabetic patients, exogenous uridine supplementation can reactivate the mechanism of glucose to glycogen to improve neurometabolism.

Obesity

Obesity is a metabolic disease caused by excessive fat accumulation. It has been shown that the rhythm of uridine after meals is disrupted in mice fed with a high-fat diet or that are obese, and uridine supplementation can relieve abnormal uridine levels in states of obesity or high-fat diets, thereby mitigating obesity.^1,66 Deng et al¹ found that the increase and maintenance of plasma uridine levels caused by fasting were critically dependent on adipocytes. A significant increase in uridine levels was observed in fat biopsies from HIV infected patients with lipodystrophy,⁶⁷ indicating that excessive production of uridine may contribute to the loss of adipose tissue. The elevation of plasma uridine in fasting depends on pyrimidine biosynthesis in adipocytes, which occurs concurrently with high levels of lipolysis.⁵² However, it is unclear whether these two processes are mechanistically linked in adipocytes. The elevation of plasma uridine is essential for the decrease in body temperature during fasting. When fasting, adipocytes are responsible for synthesizing uridine. On one hand, when uridine synthesis increases, heat loss increases, body temperature drops, and fat mass decreases.¹ On the other hand, the activation of uridine synthesis in adipocytes during fasting is also a potential mechanism for triggering triacylglycerol mobilization, a process that can reduce fat mass.⁶⁸

In addition to energy storage, adipose tissue secretes leptin, which is closely related to the occurrence and development of obesity. Xbp1 is a transcription factor involved in the ER stress response, and its overexpression increases leptin and uridine synthesis and suppresses fat accumulation.^52,69 While adiposolysis induces the expression of Xbp1 in adipocytes, which forms a circulatory mechanism that accelerates the loss of fat mass.⁵² CAD, as the rate-limiting enzyme in uridine biosynthesis, was reported to be efficiently activated by Xbp1, suggesting that the loss of fat mass triggered by Xbp1 is dependent on pyrimidine biosynthesis.⁵² These findings suggest that stimulation of the adipocyte uridine synthesis pathway may be a promising potential therapeutic target in obesity.

Acute Lung Injury in Sepsis

Sepsis is a systemic inflammatory response syndrome caused by an infection, which presents in the lungs as acute lung injury (ALI)/acute respiratory distress syndrome(ARDS).⁷⁰ In the lipopolysaccharide (LPS)-induced sepsis model, uridine supplementation can significantly reduce the systemic inflammatory response. This is thought to be related to inhibiting the expression of HSP72 and the activity of NF-KB pathway, thus inhibiting the overactivation of inflammatory factors.¹⁵ Similarly, the investigators also found that exogenous uridine supplementation inhibited oxidative stress, inflammatory response as well as ferroptosis to alleviate acute lung injury induced by LPS.⁷¹ In this model, the investigators found significant elevation of the uridine derivative UDP and increased expression of the P2Y6 in lung tissue, and knockdown of P2Y6 attenuated LPS-induced inflammatory response and acute lung injury.⁷² As reported,⁷³ P2Y6 is over-expressed in acute lung injury-related immune cells (including macrophages, neutrophils and T cells), which helps to mediate pro-inflammatory responses. UDP binding to P2Y6 acts as an immunoregulatory mediator during the inflammatory response, triggering the release of cytokines and chemokines, thereby promoting the recruitment of immune cells to sites of inflammation or infection.^74–76 And the disruption of lung homeostasis by inflammatory cell infiltration is considered a key factor in the progression of ALI / ARDS.⁷⁷ However, it is noteworthy that the P2Y6 receptor was also reported to exert inhibitory leukotriene-dependent type 2 allergic pulmonary inflammatory response effects in alveolar macrophages.⁷⁸ Together, these studies suggest that uridine can inhibit acute inflammatory response and lung injury through multiple routes, and can also be converted into other metabolites such as UDP to exert corresponding cell-determined anti-inflammatory or pro-inflammatory effects.

Osteoarthritis and Rheumatoid Arthritis

Osteoarthritis is a joint degenerative disease with an extremely high incidence in the elderly, and inflammation plays an important role in the manifestation of clinical events in osteoarthritis.⁷⁹ Specifically, certain cytokines exhibit proinflammatory properties that are clearly activated during the course of the disease and significantly alter the homeostasis of the joint environment.⁸⁰ A previous study reported⁹ that uridine improved osteoarthritis by reducing the aging of chondrocytes and mesenchymal stem cells. Another study⁸¹ showed that the expression of UPP1 was increased during the development of osteoarthritis. The level of IL-1β in the articular effusion of osteoarthritis patients was inversely correlated with the uridine concentration, and exogenous uridine supplementation significantly alleviated the damage of cartilage and inflammation in the synovium, and promoted the homeostasis of cartilage, suggesting that the UPP1/uridine axis is involved in the development and development of osteoarthritis. In addition, it was reported that UDP is highly expressed in rheumatoid arthritis and promotes its progression by increasing IL-6 production by promoting P2Y6 activity.⁸² These studies suggest that uridine can inhibit the development of osteoarthritis / rheumatoid arthritis by inhibiting inflammatory responses.

Acute Myocardial Infarction and Its Related Complications

Acute myocardial infarction (AMI) is a process of acute myocardial necrosis caused by persistent and severe myocardial ischemia. Myocardial ischemia-reperfusion injury is involved in the pathological processes of myocardial infarction and post-infarction myocardial remodeling. Inflammatory response of acute myocardial infarction plays a key role in determining the area size of myocardial infarction, and a sustained pro-inflammatory reaction can lead to adverse ventricular remodeling after myocardial infarction, making inflammation an important therapeutic target to improve the prognosis of AMI.⁸³

A previous study⁸⁴ examined the effects of uridine and its nucleotide derivatives (UMP, UDP, UTP) on the cardiac contractility of the left ventricle in isolated perfused rat hearts subjected to one hour of regional ischemia. It was found that uridine and its derivative UMP could prevent the inhibition of the contractile function of the ischemic myocardium in the isolated heart. Meanwhile, uridine and UMP were also reported to prevent myocardial shock during ischemic reperfusion in the isolated rat heart.⁸⁵ Additionally, Irina B. Krylova et al¹⁰ showed that the administration of uridine to mice five minutes prior to the ligation of the left coronary artery completely prevented the increase in lipid peroxide production and the decline in GSH levels and SOD activity. This suggests that uridine alleviates the oxidative metabolic disorder in the ischemic myocardium and restores the balance between the lipid peroxidation process and the activity of the antioxidant system, which is important for maintaining intracellular redox homeostasis during ischemia. The study also found faster clearance of intravenous uridine from the blood in acute ischemic animals compared with normal animals, suggesting that uridine is involved in the activation of intracellular anti-ischemic defense mechanisms.¹⁰ In fact, the cardioprotective effect of uridine is associated with the activation of the mitochondrial ATP-dependent K⁺ (mitoK_ATP) channels. UDP is a potent metabolic activator of the mitoK_ATP channels,⁸⁶ uridine administration significantly increased UDP content, thereby activating mitoK_ATP channels. It should be noted that UDP is unstable and unable to penetrate the cell membrane, and the supply of exogenous uridine is required for UDP and UTP synthesis in the ischemic myocardium. Notably, the protective effect of uridine on lipid peroxidation and antioxidant activity could be attenuated by the concurrent use of 5-HD (mitoK_ATP channel inhibitor). These results suggest that mitoK_ATP channels are involved in the myocardial protective effects of uridine. In summary, the aforementioned studies demonstrate that uridine can ameliorate myocardial ischemia and ischemia-reperfusion injury through the maintenance of energy homeostasis and by acting on the mitoK_ATP channels.

Organ Fibrosis

Organ fibrosis is a pathological process of stromal hyperplasia caused by chronic inflammation. In a carbon tetrachloride-induced liver fibrosis model, uridine alleviated the level of hepatic inflammation and suppressed the expression of hepatic fibrosis markers by inhibiting NF-KB activation. Moreover, uridine also alleviates carbon tetrachloride-induced liver toxicity by inhibiting oxidative stress-induced apoptosis in hepatocytes.⁸⁷ In addition, CPBMF65 (a UPP1 inhibitor) was reported to increase the levels of endogenous uridine and inhibit the progression of carbon tetrachloride-induced liver fibrosis in mice.⁸⁸

Pulmonary fibrosis is a chronic and progressive lung disease. A previous study⁸⁹ has indicated that in a bleomycin-induced pulmonary fibrosis mouse model, uridine can alleviate pulmonary inflammation, as evidenced by a reduction in white blood cells and pro-inflammatory cytokines in the bronchoalveolar lavage fluid. Additionally, exogenous supplementation of uridine can decrease collagen deposition in the lung interstitium. In cellular models, uridine can inhibit the expression of collagen and TGF-β in primary lung fibroblasts, suppress the release of pro-inflammatory cytokines from human lung epithelial cells, and reduce the production of reactive oxygen species in human neutrophils. Overall, uridine can improve the progression of fibrosis by inhibiting the inflammatory response process.

Nervous System Diseases

Alzheimer’s Disease

Alzheimer’s disease (AD), a neurodegenerative disease with progressive cognitive dysfunction, is the leading cause of cognitive impairment in the elderly population.⁹⁰ Recent studies^91–93 have noted lower uridine levels in the blood of patients with AD dementia, suggesting that uridine may be associated with clinical progression in AD. This low level may be related to lower nutrient intake in AD or increased demand for uridine in the regenerative synaptic membrane.^93,94 Uridine is a precursor for the synthesis of CDP-choline, which is a key intermediate in the production of cell membrane phospholipids, particularly playing an indispensable role in the synthesis of phosphatidylcholine (lecithin). Phosphatidylcholine is one of the main components of the cell membrane, essential for maintaining the integrity and function of the cell membrane, and is required for the formation of neuronal cell membranes. Uridine supplementation was reported to have positive effects on synaptic membrane formation and synaptic function,^93,95,96 which may alleviate synaptic dysfunction in AD.

Hypoxic-Ischemic Encephalopathy (HIE) and Hyperoxide Brain Injury

Hypoxic-Ischemic Encephalopathy (HIE) in neonates refers to a clinical syndrome characterized by ischemia and hypoxia of brain tissue due to insufficient blood flow and/or oxygen supply during the perinatal period, resulting in brain dysfunction or injury. This condition is one of the severe neurological disorders in the neonatal period and may lead to long-term neurological sequelae, including cognitive impairments, epilepsy, cerebral palsy, and others. Several studies have reported on the neuroprotective manipulation of uridine in HIE. For example, Cansev M et al found that uridine dose-dependently reduced brain damage in a neonatal HIE rat model by reducing apoptosis.⁹⁷ Goren B et al also observed that exogenous uridine supplementation may improve the cognitive effects of rats with brain injury by reducing apoptotic cell death in the early neonatal period.⁹⁸ In addition, uridine could also provide neuroprotection in a neonatal rat model of HIE by reducing apoptosis and inhibiting histone deacetylase (HDAC) activity.⁹⁹ It is evident from these research findings that the neuroprotective role of uridine in HIE is associated with the reduction of apoptosis. It was reported³⁰ that uridine nucleotides (UTP and UDP) can stimulate P2Y receptors (P2Y2, P2Y4, and P2Y6) to provide neuroprotection by reducing apoptosis. In the hyperoxic brain injury model, uridine was also observed to provide benefits to neonatal brain injury and long-term cognitive deficits through inhibition of apoptosis¹⁰⁰ and oxidative damage.¹⁰¹

Sciatic Nerve Injury

Sciatic nerve injury refers to damage to the longest nerve in the body, the sciatic nerve, which can be caused by compression, traction, laceration, or other forms of injury. Based on current data, the protective effect of uridine in sciatic nerve injury is primarily associated with its conversion to CDP-choline and its anti-apoptotic and antioxidant properties. Uridine administration can elevate levels of CDP-choline in the brains of rodents.¹⁰² Several previous studies^34,35,103 have indicated that CDP-choline can improve neural regeneration and functional recovery in models of sciatic nerve injury. Uridine may also provide benefits for sciatic nerve injury through its anti-apoptotic and antioxidant properties,⁴² as well as by enhancing neural adhesion and increasing the number of myelinated axons.¹⁰⁴

Tumors

The presence of uridine in the tumor microenvironment is important for the metabolism and survival of cancer cells. Uridine and its derivatives play a role in various biological processes in tumor cells, including nucleic acid synthesis, energy metabolism, and signaling.¹⁰⁵ In a range of mammals, including humans, plasma uridine concentrations are tightly controlled in the appropriate range.^45,106 However, disruption of this rigid homeostasis has pathophysiological consequences. A previous study¹⁰⁷ has reported that disruption of uridine homeostasis promotes DNA damage and tumorigenesis, demonstrating the crucial regulatory role that uridine and its derivatives play in tumorigenesis and development.

Under glucose-limited conditions, cancer cells can utilize uridine as an alternative source of nutrients and energy. Uridine phosphorylase 1 (UPP1) plays a crucial role in this process by releasing uridine-derived ribose, which promotes central carbon metabolism as well as supports redox homeostasis, survival, and proliferation of cancer cells.¹⁰⁸

Concentrations of uridine are high in the tumor microenvironment. Cancer cells adapt to nutrient deficiencies by sensing the concentrations of glucose and uridine in their environment. Uridine utilization is also considered to be an important compensatory metabolic process in cancer cells under conditions of nutrient deprivation.^108,109 In addition, it has been reported¹¹⁰ that uridine diphosphate glucose (UDP-Glc), a uridine derivative, plays an inhibitory role in lung cancer metastasis. UDP-Glc interacts with the RNA-binding protein HuR and competitively inhibits the stabilizing effect of HuR on SNAI1 mRNA, thereby inhibiting lung cancer metastasis. This ambiguous relationship between uridine and tumors is also associated with key enzymes involved in uridine metabolism. UCK2 is the rate-limiting enzyme in the pyrimidine nucleotide salvage pathway, and its overexpression has been found to promote malignant phenotypes in various tumors.^111,112 In addition, down-regulation of UCK2 can alter the tumor microenvironment. Inducing cell cycle arrest and activating a secretory phenotype associated with senescence may improve the tumor immune microenvironment and enhance the sensitivity of tumor cells to T-cell-mediated killing.¹¹³ UPP1 plays an integral role in pyrimidine salvage and uridine homeostasis, and it is upregulated in various cancers including lung adenocarcinoma. UPP1 drives glycolytic metabolism both in vitro and in vivo, and it significantly modulates tumor sensitivity to glycolytic inhibitors.¹¹⁴ In lung adenocarcinoma, UPP1 also enhances PD-L1 expression through the PI3K/AKT/mTOR pathway, inducing an immunosuppressive microenvironment that promotes tumor progression.¹¹⁵ These findings suggest that targeting the uridine metabolic pathway may contribute to the treatment of cancer as well as metabolic disorders, and also the regulation of immune responses.

In summary, uridine and its metabolic pathways play vital roles in tumor metabolism, metastasis, immune microenvironment regulation, and as therapeutic targets. These findings provide new perspectives and potential strategies for cancer diagnosis, treatment and drug development.

Other Diseases

Caused by mitochondrial dysfunction, Primary Mitochondrial Diseases (PMDs) are a group of inherited metabolic disorders that are highly heterogeneous and can involve multiple systems and organs of the body, especially those tissues with high energy demands, such as the heart, muscles, and brain. These disorders may manifest as muscle weakness, cardiomyopathy, epilepsy, retinopathy, hearing loss, neurodegenerative symptoms, etc.^116,117 Currently, uridine supplementation can rescue impaired oxidative phosphorylation in PMDs.¹¹⁸

In addition, the beneficial effects of uridine have been demonstrated in skeletal muscle diseases. Duchenne Muscular Dystrophy is caused by the loss of functional dystrophin proteins secondary to a systemic metabolic disorder in skeletal muscle and cardiac myocytes. Uridine slowed the development of destructive processes in skeletal muscle and partially rescued mitochondrial dysfunction in skeletal muscle in Duchenne Muscular Dystrophy.¹¹⁹ Also, uridine has been reported to be used in the treatment of patients with pyrimidine nucleotide carrier defects¹²⁰ and congenital dyserythropoietic anemia,¹²¹ which may be related to the fact that uridine enhances the proliferative capacity of human hematopoietic stem cells and promotes tissue regeneration and repair.

Uridine has been used as a therapeutic drug for orotic aciduria, a hereditary disorder characterized by excessive excretion of orotic acid in the urine.¹²² Besides, uridine has also been reported to be used for the amelioration of colitis and arthritis.^123,124

Exploration and Application of Uridine in Therapy

Having important physiological and pharmacological effects on multiple systems throughout the body, uridine has great potential as a candidate target for drug development. Several studies^28,29 have demonstrated that uridine eliminates mitochondrial toxicity induced by antiretroviral therapy in HIV-infected patients. Uridine analogs can have potent antiviral activity against HIV, hepatitis B and C, and herpesviruses by inhibiting key steps in the viral replication pathway.^125,126 The importance of uridine and its derivatives as targets in drug discovery is also reflected in the structural modification and drug design of uridine. Via chemical modification of its structure, the pharmacological and pharmacokinetic properties of uridine can be improved, including enhanced bioactivity, selectivity, metabolic stability, and absorption, as well as reduced toxicity.¹²⁷ 4-thiouridine (4SU), a uridine analog, differs from uridine by the substitution of a thiol group. It shows potent anti-inflammatory properties and has been reported to prevent experimental colitis and arthritis.¹²⁸ In addition, uridine derivatives such as 5-fluorouracil (5-FU)¹²⁹ and uramustine¹²⁷ are early-developed compounds with pharmacological activity, which have been shown to have significant antimetabolic effects in tumor therapy due to their ability to inhibit tumor cell proliferation by interfering with nucleic acid metabolism and DNA synthesis.

Uridine and its derivatives can directly act on cell surface P2Y receptors, such as P2Y2, P2Y4, and P2Y6, which are G-protein-coupled receptors. When activated, they can participate in the corresponding pathophysiological processes by initiating downstream pathways.¹³⁰ Therefore, the specific pyrimidine receptors that can be targeted by uridine and its derivatives are undoubtedly significant reference targets in drug development. In addition, human condensed nucleoside transporter protein 3 (hCNT3) is a transmembrane protein that transports uridine. By studying the molecular recognition and release mechanism between hCNT3 and uridine, uridine derivatives with high inhibitory activity can be designed.¹³¹

Therapeutic strategies for uridine are innovative. First, uridine can be delivered via multiple pathways, such as oral, injection, or topical application, which provides more options for disease treatment. Second, uridine-based mRNA modification technology also provides important support for the clinical application of uridine. In 2005, a study¹³² by Katalin Karikó et al found that replacing uridine by introducing pseudouridine into mRNA can indeed reduce the immunogenicity of mRNA, thus solving a key challenge in the clinical application of mRNA technology. This technological breakthrough provides important technical support for the subsequent development of mRNA vaccines. A study¹³³ demonstrated that mRNA vaccines containing unmodified uridine induced potent type I interferon-dependent anti-tumor immunity in a melanoma model, suggesting that uridine has a great potential for mRNA vaccine development.

Additionally, uridine can serve as a source of nutrients and energy for cells under glucose-limited conditions, especially in pancreatic cancer cells.¹⁰⁸ This suggests that blocking the utilization of uridine by drugs in specific environments may lead to new options for cancer therapy. These innovative therapeutic strategies, which may improve therapeutic efficacy while reducing side effects, provide new directions for future drug development and disease treatment.

Summary and Prospects

As an endogenous metabolite, uridine not only provides the material basis for the synthesis and modification of intracellular macromolecular organic matter as well as the overall metabolic function of the organism, but also regulates various pathophysiological processes through multiple ways. Therefore, a stable uridine supply is crucial for maintaining cellular function and organismal homeostasis.¹ Currently, uridine and its derivatives are employed in treating various diseases, but some challenges and limitations persist, including resistance and side effect problems in tumors. In addition, further attention is needed on the optimal dosage and cycle of uridine use in treating various diseases.

Since uridine is crucial in health, disease, and therapy, further exploration of uridine-based drug development and therapeutic programs is essential moving forward. On the one hand, the structure of uridine can be modified and altered appropriately to develop more efficient and less toxic derivatives. On the other hand, trying to combine other therapeutic means, such as immunotherapy and targeted therapy, may improve the anti-tumor effect of uridine. Meanwhile, through an intensive investigation of uridine’s mechanism of action, we can enhance our understanding of its role and potential risks in disease treatment. This will give clinicians precise dosing guidance and support personalized treatment.

Overall, uridine is a bioactive molecule with potential for various applications, playing a crucial role in maintaining health and treating diseases. A deeper understanding of uridine’s biological functions, disease associations, and novel therapeutic approaches will hopefully result in significant advancements in the prevention and treatment of human diseases.

Data Availability Statement

Data sharing is not applicable to this article as no new data were created or analyzed in this study.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Funding

This work was supported by grants from the Zhongnan Hospital of Wuhan University Translational Medicine and Interdisciplinary Research Joint Fund (ZNJC202015).

Disclosure

The authors report no conflicts of interest in this work.

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Dear editor

The study investigating dynamic immune indicator changes as predictors of ARDS in septic ICU patients, published in the International Journal of General Medicine,¹ merits commendation for its ambition to advance predictive biomarkers. However, its conclusions warrant critical re-evaluation due to methodological shortcomings, biological oversimplifications, and unresolved barriers to clinical implementation.

Methodological Limitations: Overfitting and Narrow Generalizability

External validation of sepsis-related ARDS predictive models using the MIMIC-IV database consistently demonstrates AUC reduction to 0.7–0.8,² underscoring the biological implausibility of Lu et al’s reported nomogram (AUC 0.998) in heterogeneous sepsis populations. Such extreme performance likely reflects overfitting to the single-center Chinese cohort (n=1836), given regional variations in sepsis etiology, treatment protocols, and demographic profiles. Critical omissions include external validation, calibration testing (eg, Hosmer–Lemeshow statistics), and early timepoint analysis (eg, 24-hour cytokine surges). Excluding days 1–2 immune dynamics ignores IL-6/TNF-α-driven endothelial injury, which precedes 60–70% of sepsis-related ARDS cases within 48–72 hours.³ Temporal myopia compromises predictive relevance for time-sensitive interventions like lung-protective ventilation.

Biological Paradoxes: Immunosuppression Misinterpretation

The assertion that immune suppression (eg, reduced CD4⁺, CD8+, T_reg counts) protects against ARDS contradicts established pathophysiology. ARDS patients exhibit immunosuppressive states marked by lymphopenia and hypogammaglobulinemia, reflecting compensatory anti-inflammatory response syndrome (CARS) rather than adaptive protection. Immunomodulatory therapies (eg, corticosteroids, tocilizumab) further confound associations, as these agents suppress lymphocyte counts by 30–50% independent of ARDS risk.⁴ Framing immune paralysis as “protective” ignores its role in secondary infection susceptibility and unresolved alveolar inflammation.

Clinical Barriers: Timing, Feasibility, and Confounding

Practical implementation faces three obstacles: 1) delayed biomarker sampling (days 3–7) postdates critical intervention windows; 2) resource-intensive flow cytometry/immunoglobulin panels limit usability in low-resource settings; and 3) unaddressed confounders (eg, survivorship bias, hospital-acquired pneumonia) risk misclassification. The model’s exclusion of ventilator-induced biases (eg, stroke volume variation inaccuracy under ≤6 mL/kg tidal volumes) further reduces applicability to modern ICUs. Without prospective validation incorporating early timepoints, cost-effectiveness analyses, and confounder adjustment, clinical utility remains unproven.

Discussion

To transition from academic novelty to clinical impact, ARDS prediction frameworks must undergo fundamental redesign prioritizing three pillars: temporal urgency, biological dynamism, and contextual generalizability.

Firstly, predictive algorithms must incorporate point-of-care biomarkers (eg, CRP/PCT ratios, lactate clearance) that provide actionable data within the critical 6-hour therapeutic window for ARDS prevention. Delays inherent in batch immune profiling render current models retrospective rather than prospective tools.

Secondly, statistical approaches must evolve from static snapshots to kinetic analyses – tracking cytokine trajectories (eg, IL-6 doubling time) and lymphocyte subset slopes that better reflect the dynamic interplay between pro-inflammatory and compensatory anti-inflammatory responses.⁵ This shift acknowledges that immune exhaustion in sepsis follows predictable temporal phases rather than discrete day-specific measurements.

Finally, validation strategies must encompass multicenter cohorts reflecting global sepsis heterogeneity, including viral/bacterial etiologies, varying antimicrobial stewardship practices, and resource availability gradients. Until models demonstrate portability across high-income and low-resource settings while integrating real-time data streams, they will remain laboratory curiosities rather than bedside necessities.

Until these gaps are addressed, this work remains a proof-of-concept – not a paradigm shift.

Disclosure

The author declares no conflicts of interest in this communication.

References

1. Lu X, Chen Y, Zhang G, Zeng X, Lai L, Qu C. Dynamic immune indicator changes as predictors of ARDS in ICU patients with sepsis: a retrospective study. Int J Gen Med. 2025;18:1163–1172. PMID: 40051893; PMCID: PMC11882469. doi:10.2147/IJGM.S501252

2. Chen Y, Zong C, Zou L, et al. A novel clinical prediction model for in-hospital mortality in sepsis patients complicated by ARDS: a MIMIC IV database and external validation study. Heliyon. 2024;10(13):e33337. PMID: 39027620; PMCID: PMC467048. doi:10.1016/j.heliyon.2024.e33337

3. Villar J, Herrán-Monge R, González-Higueras E, et al. Genetics of Sepsis (GEN-SEP) network. Clinical and biological markers for predicting ARDS and outcome in septic patients. Sci Rep. 2021;11(1):22702. PMID: 34811434; PMCID: PMC8608812. doi:10.1038/s41598-021-02100-w

4. Cui Z, Wang L, Li H, Feng M. Study on immune status alterations in patients with sepsis. Int Immunopharmacol. 2023;118:110048. PMID: 36989895. doi:10.1016/j.intimp.2023.110048

5. Yang AC, Ma WM, Chiang DH, et al. Early prediction of sepsis using an XGBoost model with single time-point non-invasive vital signs and its correlation with C-reactive protein and procalcitonin: a multi-center study. Intellig Med. 2025;11:100242. doi:10.1016/j.ibmed.2025.100242

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What is gonorrhoea?

Introduction

Sodium-glucose cotransporter-2 inhibitors (SGLT-2is) were initially introduced as treatments for type 2 diabetes but have since shown utility in various areas, such as preventing and improving renal and heart failure.^1–4 Consequently, the use of SGLT-2is has expanded across multiple fields. Recently, studies have highlighted their efficacy in addressing fatty liver disease.^5–7 Approximately 65% of patients with type 2 diabetes are estimated to have metabolic dysfunction-associated steatotic liver disease (MASLD).^8,9 Moreover, the prevalence of metabolic dysfunction-associated steatohepatitis (MASH) in these patients can be as high as 66.44%,⁸ indicating that a considerable portion of MASLD in these patients corresponds to MASH. If left untreated, MASH can lead to progressive fibrosis, increasing the risk of severe liver failure and cardiovascular events.^10–12 Therefore, improving liver function is as critical a therapeutic goal as glycemic control in patients with diabetes.

However, SGLT-2is are associated with several side effects, and frequent urination is one of the most common, affecting approximately 5% of patients who are prescribed these drugs.¹³

In particular, nocturia in older adults can lead to sleep disturbances because of nighttime awakenings, reduced quality of life,^14,15 and even increased risks of depression and dementia,¹⁶ as well as falls and fractures.^17,18 Therefore, addressing this issue is a critical challenge.

In this study, we investigated whether the fatty liver improvement effects of SGLT-2i differ by individual drugs or represent a class effect (a common effect across all drugs in this group), using three different SGLT-2is for evaluation. In addition, we focused on the fact that tofogliflozin has the shortest half-life in the blood and the shortest duration of action among SGLT-2is,¹⁹ and investigated whether its effect on nocturia differs from that of other SGLT-2is.

Materials and Methods

Study Design and Participants

The participants in this study were adults aged 30 years or older who were diagnosed with type 2 diabetes and fatty liver and were classified as having MASLD. Type 2 diabetes is diagnosed when at least two of the following criteria are fulfilled: a fasting plasma glucose level of 126 mg/dL (7.0 mmol/L) or higher, a 2-hour plasma glucose level of 200 mg/dL (11.1 mmol/L) or higher during a 75-g oral glucose tolerance test, a random plasma glucose of 200 mg/dL (11.1 mmol/L) or higher, and a hemoglobin A1c level of 6.5% (48 mmol/mol) or higher.²⁰ Alternatively, patients who have already been diagnosed with type 2 diabetes based on the above tests. In addition, lipid droplets in more than 5% of hepatocytes, using ultrasonography, are defined as steatosis, referred to as fatty liver.²¹ Currently, hepatic steatosis involving more than 5% of the liver parenchyma can be diagnosed using B-mode ultrasonography.^22,23

SGLT-2is were initiated or added to the treatment regimen for patients with HbA1c levels ≥7.5% (58 mmol/mol). MASLD was diagnosed according to the presence of fatty liver and at least one of the following five criteria:²⁴ 1. a BMI of ≥23.0 kg/m² or a waist circumference ≥94 cm for men and ≥80 cm for women; 2. prediabetes or diabetes treated with anti-diabetic medication; 3. blood pressure ≥130/85 mmHg or treatment with antihypertensive medication; 4. triglyceride (TG) levels ≥150 mg/dL or treatment with lipid-lowering medication; and 5. high-density lipoprotein cholesterol (HDL-C) levels ≤40 mg/dL for men or ≤50 mg/dL for women, or treatment for low HDL-C levels.

The exclusion criteria included patients already receiving SGLT-2is, those using insulin, and individuals with severe liver cirrhosis, severe renal dysfunction, pregnancy, or severe mental illness. In addition, patients with conditions known to cause nocturia, such as prostatic disorders or uterine prolapse, were excluded from the study.

Randomization

Eligible participants were randomized using a permuted block method stratified by age (≥65 years or <65 years), sex (male or female), HbA1c levels (≥9.0% or <9.0% [≥75 mmol/mol or <75 mmol/mol]), body weight (BMI ≥25.0 or <25.0 kg/m²), and duration of diabetes (≥10 years or <10 years). The participants were assigned to one of the following three groups in a 1:1:1 ratio: tofogliflozin group (Tofo group), empagliflozin group (Empa group), or dapagliflozin group (Dapa group). This trial is a prospective, randomized, open-label, blinded endpoint (PROBE) study conducted at a single center. The evaluation of liver fibrosis markers and nocturia frequency was independently performed by physicians and research staff from the adjudication committee, both of whom were blinded to treatment allocation.

Study Treatment

In the Tofo group, the participants received tofogliflozin at a dose of 20 mg. In the Empa group, the participants received empagliflozin at a dose of 10 mg. In the Dapa group, the participants received dapagliflozin at a dose of 5 mg. All these SGLT-2is were administered orally after breakfast.

During the study period, discontinuation of these SGLT-2is or the addition of other medications was not permitted unless adverse events occurred. The participants were followed up at outpatient visits initially after 1 month and subsequently every 2 months for a total of 6 months, resulting in a 7-month observation period. At each visit, measurements of height, weight, BMI, waist circumference, blood pressure, blood tests, body composition, and ultrasound elastography were conducted.

Outcomes

The primary endpoints were changes in the frequency of nocturia and liver function markers, namely aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyl transpeptidase (γ-GPT), fibrosis-4 (FIB-4) index, and mac-2 binding protein glycan isomer (M2BPGi). In addition, liver fibrosis was evaluated using ultrasound elastography (Aplio i700, Canon Medical Systems, Tokyo). Shear wave speed measurements were interpreted as follows: values between 1.00 and 1.66 m/sec were classified as fibrosis grade (F) 0–1 (normal to mild fibrosis), with higher values indicating progression of fibrosis, ie, increased F score.^25–27

Nocturia was defined as waking to urinate at least once during the night,²⁸ with “nighttime” defined as the time between 11:00 pm and 5:00 am in this study.

Secondary endpoints included changes in HbA1c levels, fasting blood glucose, body weight, waist circumference, the lipid profile, and blood pressure. This study was conducted with the approval of the Institutional Review Board (IRB) of Shinkomonji Hospital. Written informed consent was obtained from all of the participants before enrollment. In addition, we confirmed that all research was performed following relevant guidelines/regulations.

This study has been performed in compliance with the Declaration of Helsinki. The trial protocol was registered with the UMIN Clinical Trial Registry (https://www.umin.ac.jp/ctr/) under the number UMIN000054278, with an initial registration date of 28/04/2024. The trial protocol is available in the Supplementary Material accompanying this manuscript.

Statistical Analyses

The sample size was calculated on the basis of the assumption that nighttime was defined as from 11:00 pm to 5:00 am, with the frequency of nighttime urination (nocturia) estimated to be 0.8 times in the Tofo group and 2.1 times in the Empa and Dapa groups. Nocturia frequency was calculated using a method based on the results of a pilot study (data not shown). Assuming a standard deviation of 2, an α error of 0.05, a statistical power of 0.8, and a 10% dropout rate over the 7-month follow-up, a 1:1:1 allocation required 43 participants in each group, resulting in a total sample size of 129 participants. Regarding the baseline characteristics, continuous variables are expressed as the mean ± standard deviation for descriptive analysis, and categorical variables are expressed as frequencies (%). To examine whether there were any variations in the samples between the groups at baseline, a test of homogeneity of variance (F-test) was conducted. Comparisons of continuous variables between the three groups at baseline and at each time point (1, 3, 5, and 7 months) were performed using an analysis of variance (ANOVA) with Dunnett’s test, and the Tofo group was set as the control. Temporal changes in continuous variables within each group were assessed using an ANOVA with Dunnett’s test, setting the baseline values as the control. In all cases, comparisons of categorical variables were performed using an m×n chi-square test. In this study, a p-value <0.05 was not considered significant. Instead, p-values adjusted using the Bonferroni correction (ie, 0.05 divided by the total number of pairwise comparisons) were considered significant under the concept of multiple comparisons. Statistical analyses were performed using SPSS ver. 17.0 (SPSS Inc., Chicago, IL, USA) and R software (version 4.1.1).

Results

Baseline Characteristics

The participants were recruited between April and the end of September 2024. A total of 135 participants were randomly assigned to the three groups (Figure 1). The participants had a mean age of 61 years and 43% were female. The mean BMI was 24.5 kg/m², the mean HbA1c level was 8.7%, the mean FIB-4 index was 1.84, the mean shear wave speed was 1.51 m/sec, and the mean number of nocturia episodes was 0.6 times. No significant differences in these variables were observed between the groups (Table 1).

Table 1 Baseline Characteristics

Figure 1 Screening, randomization, and follow-up. A total of 135 participants were randomly assigned to three groups of 45, each receiving a prescribed drug: the Tofo group received 20 mg of tofogliflozin, the Dapa group received 5–10 mg of dapagliflozin, and the Empa group received 10–25 mg of empagliflozin. All participants were followed for seven months. During the study, there were dropouts: 4 in the Tofo group, 5 in the Dapa group, and 4 in the Empa group. However, all participants were included in the analysis according to the intention-to-treat and per-protocol set criteria.

Primary Outcome of MASLD

All groups showed significant reductions in AST, ALT, and γ-GTP levels and the FIB-4 index compared with baseline (all p-values <0.05). In addition, a gradual reduction in shear wave speed-based fibrosis grade was observed compared with baseline across all groups (all p-values <0.05). However, no significant differences in these variables were found between the three groups. Furthermore, no significant changes in M2BPGi levels were observed in any group compared with baseline (Figure 2).

Figure 2 Changes in liver function and nocturia frequency with SGLT-2i treatment. Blue square, tofogliflozin group; purple diamond, dapagliflozin group; sky-blue circle, empagliflozin group. T-bars showed the standard deviations. * To assess time effects using analysis of variance followed by Dunnett’s test, baseline measurements (0 months) were compared with those at 1, 3, 5, and 7 months, in each of the three groups. † Comparisons between the Tofo group and the Dapa and Empa groups were conducted at each time point (0, 1, 3, 5, 7 months). The Bonferroni correction defined statistical significance as p<0.05/([4×3] + [2×5]) = 0.00227. Therefore, * and † denote p <0.00227. Abbreviations: AST, aspartate aminotransferase; ALT, alanine aminotransferase; γ-GPT, gamma-glutamyl transpeptidase; FIB-4, fibrosis-4; M2BPGi, mac-2 binding protein glycan isomer.

Primary Outcome of the Frequency of Nocturia

In the Empa and Dapa groups, the frequency of nocturia significantly increased to 1.7 and 1.9 times, respectively, 1 month after starting medication compared with baseline. In contrast, the Tofo group showed an increase in the frequency of nocturia by only 0.8 times, which was not statistically significant. Consequently, the Tofo group showed a significantly lower frequency of nocturia than the other two groups (p<0.001). This difference persisted until 3 months after the initiation of treatment; however, the frequencies were 1.3, 1.2, and 0.7 times, respectively, with a p-value of 0.010, which did not meet the significance threshold after Bonferroni correction (p < 0.00227). In addition, the difference diminished after the fifth month. Over time, the frequency of nocturia decreased in all three groups, with no significant changes from baseline or differences between the groups (Figure 2).

Secondary Outcomes

All three groups showed a significant reduction in weight and waist circumference compared with baseline, with no significant differences between the groups. No significant changes in systolic or diastolic blood pressure were observed in any group compared with baseline. Fasting plasma glucose and HbA1c levels were significantly decreased in all three groups compared with baseline. While the Dapa and Empa groups showed a slight trend of a greater reduction in these variables than the Tofo group, no significant differences were observed between the groups. A significant reduction in TG levels was observed in all three groups, with no significant intergroup differences. In females, no significant changes in HDL-C levels were observed in any group. In contrast, in males, all three groups showed a significant increase in HDL-C levels at 1 month compared with baseline, with no differences between the groups (Figure 3). Low-density lipoprotein-cholesterol levels remained unchanged in all groups compared with baseline, with no difference between the sexes (data not shown).

Figure 3 Changes in body weight, blood pressure, blood glucose, and lipid levels with SGLT-2i treatment. Blue square, tofogliflozin group; purple diamond, dapagliflozin group; sky-blue circle, empagliflozin group. T-bars showed standard deviations. *To assess time effects using analysis of variance followed by Dunnett’s test, baseline measurements (0 month) were compared with those at 1, 3, 5, and 7 months in each of the three groups. Comparisons between the Tofo group and the Dapa and Empa groups were conducted at each time point (0, 1, 3, 5, 7 months). The Bonferroni correction defined statistical significance as p<0.05/([4×3] + [2×5]) = 0.00227. Therefore, *denotes p <0.00227. Abbreviations: BMI, body mass index; BP, blood pressure; HbA1c, glycated hemoglobin; FPG, fasting blood glucose; TG, triglycerides; HDL-C, high-density lipoprotein-cholesterol; LDL, low-density lipoprotein-cholesterol.

Sub-Analysis

A sub-analysis was conducted by stratifying the participants according to diabetes duration, age, baseline HbA1c levels, and sex. Based on the baseline distributions, participants were categorized into tertiles: 33–59, 60–71, and 72–89 years for age, and 7.5–8.9%, 9.0–10.3%, and 10.4–12.4% for HbA1c levels.

This analysis revealed that older age and higher baseline HbA1c levels were associated with greater effectiveness of tofogliflozin in reducing the frequency of nocturia (Table 2). No significant differences in these variables according to sex were observed. In addition, the frequency of daytime (5:00 a.m. to 11:00 p.m.) urinations increased to 7.9 times in the Tofo group, 7.1 times in the Dapa group, and 6.9 times in the Empa group after one month, with a significant difference among the three groups (p = 0.0014). Subsequently, urinary frequency gradually declined, and no significant differences were observed among the groups after three months (Figure 4).

Table 2 Frequency of Nocturia

Figure 4 Frequency of daytime urination. The daytime urinary frequency increased after one month to an average of 7.9 times in the Tofo group, 6.9 times in the Dapa group, and 7.1 times in the Empa group, with a statistically significant difference among the three groups (p = 0.0014). Subsequently, urinary frequency gradually declined, and no significant differences were observed among the groups after three months. * To assess time effects using analysis of variance followed by Dunnett’s test, baseline measurements (0 month) were compared with those at 1, 3, 5, and 7 months in each of the three groups. † Comparisons between the Tofo group and the Dapa and Empa groups were conducted at each time point (0, 1, 3, 5, 7 months). The Bonferroni correction defined statistical significance as p <0.05/([4×3] + [2×5]) = 0.00227. Therefore, * and † denote p < 0.00227.

Adverse Events

Genital mycotic infections and urinary tract infections were observed in all three groups (Table 3). No significant differences in the incidence rates of these events were observed between the three groups.

Table 3 Frequency of Adverse Events

Discussion

In this study, tofogliflozin, dapagliflozin, and empagliflozin showed reduced and improved liver function and fibrosis markers associated with MASLD. However, no significant differences in these markers were detected between the three groups. Notably, tofogliflozin significantly reduced the frequency of nocturia 1 month after initiating treatment compared with the other two drugs. However, the difference disappeared after three months. There was no significant difference in weight loss, an improvement in blood glucose levels, or a change in lipid profile between the groups.

Effect of SGLT-2is on MASLD

Recently, there has been an increase in reports showing the efficacy of SGLT-2is in improving MASLD.^5–7 However, whether this effect represents a class effect of SGLT-2is remains unclear. Our findings suggest that SGLT-2is have a class effect in improving fatty liver or, at least, that the three drugs used in this study have beneficial effects on MASLD.

A total of 68.8% of patients with type 2 diabetes have been reported to have coexisting MASLD,⁸ which is associated with an increased risk of liver fibrosis.²⁹ However, randomized controlled trials on SGLT-2is have shown a reduction in hepatic fat content as measured by magnetic resonance imaging.^30,31

SGLT-2is lower blood glucose levels by inhibiting SGLT-2, a protein predominantly expressed in the renal tubules, thereby reducing glucose reabsorption in the kidneys. This mechanism is associated with an improvement in insulin resistance, a reduction in free fatty acids, decreased hepatic fat deposition, and amelioration of intrahepatic inflammation and fibrosis.³² In our study as well, significant improvement in liver fibrosis was observed at five months after the initiation of treatment. Furthermore, SGLT-2is have been shown to enhance insulin sensitivity by increasing adiponectin levels³³ and to promote glucagon-like peptide 1 secretion,^34,35 both of which may contribute to the improvement of MASLD. Notably, SGLT-2 expression is not limited to the kidneys; it has also been detected in hepatocytes and bile duct epithelial cells.³⁶ This finding suggests that SGLT-2is exert direct effects on the liver or affect hepatic function indirectly through bile acids and the gut microbiota, resulting in reduced hepatic fat deposition and inflammation. The use of SGLT-2is in the treatment of type 2 diabetes has shown potential therapeutic benefits in MASLD, possibly through mechanisms that may indirectly influence the progression of liver disease.^37,38 In addition, as discussed later, although tofogliflozin has a shorter half-life compared to the other two agents, no significant differences in liver function improvement, including antifibrotic effects, were observed among the three groups. These findings suggest that, similar to its glucose-lowering effects, the improvement in liver function may be independent of the drug’s half-life duration.

Effect of SGLT-2is on Nocturia Frequency

Nocturia is defined as the need to urinate during the night, interrupting sleep at least once.²⁸ Nocturia is associated with sleep disturbances,¹⁵ an increased risk of falls and fractures,^17,18,39 and an elevated risk of depression and dementia.¹⁶ These effects can greatly reduce quality of life, especially in older adults,^40–42 highlighting the importance of preventing and treating nocturia.

Frequent urination is a common side effect of SGLT-2is, leading to increased urination during the day and at night, which may contribute to nocturia. A randomized controlled trial reported that approximately 5% of individuals experience this side effect.¹³ However, other studies have shown that empagliflozin increases daily urine volume by 500 mL,⁴³ and nearly all individuals taking SGLT-2is exhibit some increase in urinary frequency.⁴⁴ The change in frequency of urination can vary according to the type of SGLT-2i used and the patients’ underlying conditions. However, SGLT-2is contribute to the development of frequent urination. This effect is particularly prominent in patients with poor glycemic control at the time of prescription, because osmotic diuresis and nephropathy are thought to further increase the frequency of urination.¹³ On the contrary, several studies have noted that while polyuria is a frequent early complaint, it often subsides within weeks of treatment initiation.^1,45,46 This timeline coincides with the period in which blood glucose begins to normalize, suggesting a strong correlation between the resolution of polyuria and improved glycemic control. The EMPA-REG and CANVAS studies involving SGLT-2is demonstrated the greatest improvement in glycemic control at 12 to 13 weeks (approximately 3 months) following drug initiation,^1,46 aligning with the 3-month time point observed in the present study. Frequent urination caused by SGLT-2is is largely due to osmotic diuresis driven by glucosuria. As blood glucose control improves, the filtered load of glucose decreases, leading to reduced glucosuria and, consequently, decreased urinary frequency.⁴⁷

The blood half-life of tofogliflozin is 5–6 hours,¹⁹ which is shorter than that of empagliflozin (9.88–13.1 hours)⁴⁸ and dapagliflozin (12.9 hours).⁴⁹ Therefore, when tofogliflozin is taken in the morning, its effects are likely to diminish by nighttime. In this study, the frequency of nocturia in the Tofo group did not significantly increase (0.8 times), and this small increase was notably less than that in the other two groups (1.7 and 1.9 times, respectively).

This trend was particularly evident in patients with higher baseline HbA1c levels or older age. Therefore, when initiating SGLT-2i therapy, tofogliflozin may be a more appropriate option for patients with baseline HbA1c levels ≥ 9.0% or those aged ≥ 72 years, given its potential benefit in reducing nocturia frequency. Conversely, the nocturia-reducing effect of tofogliflozin may be limited in patients with baseline HbA1c levels ≤ 8.9% or age ≤ 59 years.

In addition, we did not find any significant differences in the daytime urination frequency or a reduction in HbA1c levels among the three groups.

Adverse Events of SGLT-2is

Regarding adverse events, urinary tract infections and genital infections were observed in all SGLT-2i groups. However, the incidence of these events is comparable to previously reported rates,¹³ with no significant differences between the groups.

Study Limitation

This study has several limitations, such as its single-center design, the fact that only Japanese participants were included, and the 7-month study duration. Liver function may continue to change beyond 7 months. While a significant difference in the frequency of nocturia was observed at 1 and 3 months, this difference diminished over time, suggesting that additional long-term studies may not be required.

Conclusion

All three SGLT-2is led to a reduction in MASLD-related parameters, but no significant differences in these parameters were observed between the groups. These findings suggest that the improvement in fatty liver associated with SGLT-2is may be a class effect. SGLT-2 is are now widely recognized not only for their glucose-lowering effects in patients with diabetes but also for their cardioprotective and renoprotective effects. The findings of this study may contribute to the growing body of evidence supporting the potential hepatoprotective effects of SGLT-2 is. Tofogliflozin significantly reduced the frequency of nocturia compared with the other two SGLT-2is. This finding suggests that the shorter half-life in the blood of tofogliflozin may be particularly beneficial for patients with baseline HbA1c levels ≥ 9.0% or age ≥ 72 years.

Data Sharing Statement

Some or all datasets generated during and/or analyzed during the current study are not publicly available but are available from the corresponding author on reasonable request.

Ethics Approval and Consent to Participate

This study was conducted with the approval of the Institutional Review Board (IRB) of Shinkomonji Hospital. Written informed consent was obtained from all of the participants before enrollment. In addition, we confirmed that all research was performed following relevant guidelines/regulations.

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Funding

This study was supported by a grant from the Fukuoka Medical Association (T.K.). The sponsor did not contribute to the design, collection, management, analysis, interpretation of data, writing of the manuscript, or the decision to submit the manuscript for publication.

Disclosure

All the authors declare no competing interests in this work.

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Scientists at The Pirbright Institute have made a new breakthrough in the fight against Nipah virus – a highly dangerous zoonotic pathogen – by evaluating vaccine candidates specifically designed for pigs. This progress targets a crucial step in cutting off transmission routes and protecting both animal and human health.

Understanding the threat of Nipah virus

Nipah virus is a zoonotic pathogen, meaning it can be transmitted from animals to humans. It originates in Old World fruit bats and primarily affects pigs and humans. The virus first emerged during a major outbreak in Malaysia in 1998-99, which forced the culling of nearly half the country’s pig population and caused huge economic losses.

Since that first outbreak, Nipah virus has repeatedly surfaced across South and Southeast Asia, particularly in Bangladesh and India. In these regions, human-to-human transmission and consumption of contaminated food, such as date palm sap, have contributed to high fatality rates.

Infected individuals can develop encephalitis (brain inflammation) and respiratory complications. The disease usually begins with flu-like symptoms but can rapidly worsen to coma and death. Unfortunately, there are currently no licensed vaccines or treatments available for either pigs or humans – despite the virus posing a significant threat to public and animal health.

Because of its severity and epidemic potential, Nipah is designated a priority disease by the World Health Organization (WHO) and a priority pathogen by the UK Health Security Agency – highlighting the urgent need for research and development.

Vaccine development targets a key transmission route

A collaborative team of researchers from the UK, Australia and Bangladesh -led by The Pirbright Institute – has tested experimental Nipah virus vaccines in pigs to help prevent transmission through one of its primary routes.

Published in npj Vaccines, the study details the creation of three vaccine candidates using different viral surface proteins. One candidate even employed the same viral vector platform as the Oxford/AstraZeneca COVID-19 vaccine.

The researchers evaluated the vaccines’ immunogenicity – the ability to trigger an immune response – in mice and pigs. They also tested the vaccines’ protective potential in pigs. Further trials were conducted in ‘backyard’ pigs living under field conditions in the ‘Nipah belt’ region of Bangladesh.

All three vaccine candidates successfully protected pigs from Nipah virus infection. While the strength of the immune response varied among candidates, all demonstrated effective immunity in pigs vaccinated under real-world conditions in Nipah-endemic areas

Impact and next steps

Professor Simon Graham, Group Leader of the Porcine Reproductive and Respiratory Syndrome (PRRS) Immunology Group at The Pirbright Institute, emphasised the significance of this progress:

“By preventing Nipah outbreaks in pig populations, we can in turn mitigate human infections, protect economies, public health and food security. Our research moves us one major step closer to achieving this goal.”

The team is now collaborating with partners in Germany to develop a cost-effective dual vaccine that could protect pigs against both Nipah virus and a common swine disease. This approach aims to combine pandemic preparedness with practical benefits for farmers.

The importance of a ‘One Health’ approach

As scientists work urgently to stay ahead of emerging high-threat diseases, this research highlights the critical need for a ‘One Health’ strategy. This is an integrated approach that recognises the interconnection between the health of animals, humans and ecosystems. Addressing these areas collectively, rather than in isolation, is essential for safeguarding global health.  

An international study reveals that boosting greenery could be a powerful tool that protects the brain from the harmful effects of polluted air linked to Alzheimer’s and dementia worldwide.

Study: Greenness modified the association of PM_2.5 and ozone with global disease burden of Alzheimer’s disease and other dementias. Image credit: AMINSEN/Shutterstock.com

A recent study in Scientific Reports investigated whether greenness influences the association between particulate matter (PM) with a diameter of less than 2.5 micrometers (PM_2.5) and ozone, and whether this relationship affects the disease burden linked to Alzheimer’s disease (AD) and other dementias.

The association between dementia and air pollution

Dementia is a collection of symptoms associated with a decline in cognitive ability, such as memory loss, difficulty with thinking, and reduced problem-solving ability, impacting daily life. AD is a type of dementia, which has been identified as the seventh leading cause of death worldwide. Approximately 55 million people worldwide have been diagnosed with AD, and this number has been predicted to rise as high as 79 million by 2030 and 139 million by 2050.

Global healthcare costs have significantly increased due to the high prevalence of dementia. Considering the increased prevalence, it is crucial to identify modifiable risk factors, particularly to prevent AD and other dementias and reduce the economic burden of the disease. The World Health Organization (WHO) and the Lancet Commission have independently identified air pollution as an emerging risk factor of AD.

Air pollutants trigger oxidative stress and neuroinflammation in the brain, thereby increasing the risk of multiple diseases, including metabolic disorders, cardiovascular conditions, and dementia. Previous studies have established an association between PM_2.5 and AD. In 2015, approximately 28% of deaths and 30% of disability-adjusted life years (DALY) were linked to dementia caused by ambient PM_2.5 pollution.

Interestingly, a large-scale US-based study highlighted that higher neighbourhood greenness lowers the risk of AD and related dementias. This occurrence has been attributed to a greener environment, reducing stress by promoting physical activity and alleviating the adverse effects of air pollution. Not many studies have explored how much a greener environment impacts the association between air pollution and the global disease burden of AD and other dementias.

About the study

The current ecological study aimed to examine the relationship between air pollutants and AD burden worldwide and assess the potential to modify this association through a greener environment.

All relevant data on the incidence of AD and other dementias, related deaths, and DALY were obtained from the Global Burden of Disease (GBD) database. The current study’s data were sourced from 162 countries, spanning 2010, 2011, 2014, 2015, 2016, and 2017.

PM2.5 and ozone, the two most extensively studied air pollutants in the GBD database, were considered. To evaluate the greenness exposure, this study used enhanced vegetation index (EVI) and country-level normalized difference vegetation index (NDVI) data from the Terra Moderate Resolution Imaging Spectroradiometer (MODIS). The NDVI and EVI values range from -0.2 to 1.0, where higher values approaching 1.0 represent greater greenness, while any negative values highlight cloud cover, snow, or water bodies.

Study findings

The current study estimated the global incidence rate of AD and other dementias, death rate, and DALY to be 55.52, 12.48, and 206.94 per 100,000 population, respectively. Global spatial distribution analysis revealed that the highest prevalence of AD, death, and DALY due to AD and other dementias occurred in Japan in 2017, followed by Italy. In contrast, Qatar and the United Arab Emirates exhibited the lowest incidence of these diseases.

During the study periods, the values of NDVI and EVI were estimated to be 0.56 and 0.33, respectively. Furthermore, PM_2.5 and ozone were estimated to be 23.13 μg/m³ and 39.96 ppb, respectively. Compared to the rest of the world, a higher greenness density was observed in America and Oceania.  

As per the global landscape, the average levels of PM_2.5 and ozone were higher in Asia and Africa, and lower in Europe, Oceania, and America. The Spearman correlations between air pollutants and greenness ranged between -0.36 and -0.40, indicating negative and moderate correlations.

A statistically significant association was observed between PM_2.5 and ozone and the disease burden of AD and other dementias. In a fully adjusted model, a 10-unit increment in PM_2.5 and ozone was associated with a 2.0% and 1.9% increase in the incidence rate of AD and other dementias, respectively. The same exposure levels were associated with a 2.8% and 9.5% increase in death rate, and a 2.2% and 6.7% increase in the DALY rate, respectively.

A robust negative association was observed between greenness and dementia, particularly at moderate levels of greenness, with weaker or non-significant associations at very high greenness levels, suggesting a non-linear relationship. The disease burden was significantly higher in countries with a low socio-demographic index (SDI) compared to middle or high SDI categories. Similarly, a higher AD and other dementia rate ratio was associated with countries with low gross national income (GNI).

The current study demonstrated that both PM_2.5 and ozone were associated with reduced harmful impacts on dementia burden (rather than an actual “protective” effect) in areas with high levels of greenness, and that in some of the highest greenness quartiles, the pollutant-disease associations became insignificant or even reversed.

Conclusions

The findings here showed a positive association between annual average concentrations of PM_2.5 and ozone exposure and the incidence, deaths, and DALYs of AD and other dementias. A greener environment could mitigate this association, particularly at moderate-to-high greenness levels. Therefore, increasing green space worldwide would positively impact health, although the protective effects of greenness may not increase linearly at the highest levels of vegetation.

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Adults born preterm were significantly more likely to have cardiometabolic risk factors and internalized mental health issues than full-term peers, according to an ongoing preterm birth cohort study in the US.

“This study addresses a significant gap in understanding the long-term health effects of preterm birth in the US,” said lead author Amy D’Agata, PhD, of the College of Nursing, The University of Rhode Island, Kingston, Rhode Island, in an interview.

Although the annual preterm birth rate in the US has held at a relatively stable 10%-12% for decades, since the 1970s, more preterm infants are surviving because of advances in neonatal intensive care, D’Agata said. Millions of individuals born preterm are aging into adulthood, but few data are available on their long-term health outcomes, she noted.

In the new study, published in JAMA Network Open, D’Agata and colleagues reviewed data from a cohort of individuals who received level III neonatal intensive care at a single center between 1985 and 1989. The study population included 158 preterm-born and 55 full-term born adult control individuals.

Preterm was defined as weighing under 1850 g at birth with various neonatal diagnoses; critically ill infants and those with major congenital abnormalities were excluded. The mean age across the groups was 35 years; 50% were women. The researchers used latent growth curve models to show changes over time.

Overall, the preterm individuals who had higher medical risk in early life were significantly more likely to have a range of health problems at 35 years of age, notably, higher triglycerides than control individuals (beta value, 53.97; P = .03).

Measures of systolic blood pressure and central adiposity also were significantly higher in the preterm birth group (beta values of 7.15 and 0.22, respectively), whereas bone density and high-density lipoprotein cholesterol were lower (beta values of -1.14 and -13.07, respectively).

In addition, internalizing mental health problems were significantly more common in the preterm cohort than in the control individuals (beta value, 0.85; P = .01) but no difference in externalizing mental health problems was noted between the groups.

The researchers also reviewed the impact of social protection and childhood socioeconomic status and found no association between these and physical or psychological health risks in adults born preterm.

The Long View of Preterm Birth

The population of adults born preterm remains largely invisible to the US healthcare system and its clinicians, highlighting critical issues of health equity and quality of care, D’Agata told Medscape Medical News.

“Much of the existing research in this area has focused on international, homogeneous populations, creating a need for rigorous, US-based longitudinal data to guide healthcare policy and clinical practice,” she added.

“These findings generally confirmed what has been observed internationally, that there is a link between higher early life medical risk and increased likelihood of mental health issues, elevated systolic blood pressure, unfavorable cholesterol and triglyceride levels, body fat distribution, and lower bone density among adults born preterm, and it was notable to see these clear and consistent associations replicated in a US cohort using a prospective, longitudinal design,” said D’Agata.

The study findings emphasized the need to inquire about birth history in adult care settings and suggest that those born preterm and their families must be their own health advocates, if necessary, said D’Agata. “Even if a patient isn’t asked about their birth history, they should share it,” she noted. Clinicians work hard to provide the best care, but it takes time for evidence-based research to inform clinical practice, she said.

“Although our birth cohort is small and comes from a single geographic region, the results generally align with international findings,” D’Agata told Medscape Medical News. However, future studies should include more racially and ethnically diverse cohorts from multiple clinical settings, she said. Research is needed not only to examine which subgroups of preterm individuals are most at risk but also to differentiate between those with varying degrees of early life complications, she added.

Long Follow-Up Strengthens Findings

The 35-year duration of the preterm birth cohort study was impressive and valuable, said Tim Joos, MD, a clinician with a combination internal medicine/pediatrics practice at Neighborcare Health in Seattle. “We don’t often have the long game in mind, in healthcare as well as in other parts of our society,” said Joos, who was not involved in the study. “We don’t tend to follow pediatric conditions into adulthood,” he noted.

The current study findings demonstrated a long-term psychological and physical impact of prematurity on adult health that was humbling, Joos told Medscape Medical News. Looking ahead, the results highlight not only the need to continue to prevent preterm birth but also to the importance of asking older patients about preterm birth as part of their health history, he said.

This study was funded by the National Institute of Nursing Research of the National Institutes of Health. D’Agata disclosed no financial conflicts of interest. Joos disclosed no financial conflicts of interest.

Researchers have demonstrated a novel vaccine delivery method in an animal model, using dental floss to introduce vaccine via the tissue between the teeth and gums. The testing found that the new technique stimulates the production of antibodies in mucosal surfaces, such as the lining of the nose and lungs.

“Mucosal surfaces are important, because they are a source of entry for pathogens, such as influenza and COVID,” says Harvinder Singh Gill, corresponding author of a paper on the work. “However, if a vaccine is given by injection, antibodies are primarily produced in the bloodstream throughout the body, and relatively few antibodies are produced on mucosal surfaces.

“But we know that when a vaccine is given via the mucosal surface, antibodies are stimulated not only in the bloodstream, but also on mucosal surfaces,” says Gill, who is the Ronald B. and Cynthia J. McNeill Term Professor in Nanomedicine at North Carolina State University. “This improves the body’s ability to prevent infection, because there is an additional line of antibody defense before a pathogen enters the body.”

This is where the junctional epithelium comes in. The term epithelium applies to the tissue that lines the surface of your body parts, such as the lining of your lungs, stomach and intestines. Most epithelial tissues include robust barriers that are designed to keep bad things – from viruses to dirt – from entering your blood stream. But the junctional epithelium is different.

The junctional epithelium is a thin layer of tissue located in the deepest part of the pocket between the tooth and the gum, and it lacks the barrier features found in other epithelial tissues. The lack of a barrier allows the junctional epithelium to release immune cells to fight bacteria – you find these immune cells in your saliva, as well as between your teeth and gums.

“Because the junctional epithelium is more permeable than other epithelial tissues – and is a mucosal layer – it presents a unique opportunity for introducing vaccines to the body in a way that will stimulate enhanced antibody production across the body’s mucosal layers,” says Gill.

To determine the viability of delivering vaccines via the junctional epithelium, the researchers applied vaccine to unwaxed dental floss and then flossed the teeth of lab mice. Specifically, the researchers compared antibody production in mice that received a peptide flu vaccine via flossing the junctional epithelium; via the nasal epithelium; or via placing vaccine on the mucosal tissue under the tongue.

“We found that applying vaccine via the junctional epithelium produces far superior antibody response on mucosal surfaces than the current gold standard for vaccinating via the oral cavity, which involves placing vaccine under the tongue,” says Rohan Ingrole, first author of the paper, who was a Ph.D. student under Gill at Texas Tech University. “The flossing technique also provides comparable protection against flu virus as compared to the vaccine being given via the nasal epithelium.”

“This is extremely promising, because most vaccine formulations cannot be given via the nasal epithelium – the barrier features in that mucosal surface prevent efficient uptake of the vaccine,” Gill says. “Intranasal delivery also has the potential to cause the vaccine to reach the brain, which can pose safety concerns. However, vaccination via the junctional epithelium offers no such risk. For this experiment, we chose one of the few vaccine formulations that actually works for nasal delivery because we wanted to see how junctional epithelium delivery compared to the best-case scenario for nasal delivery.”

The researchers also tested whether the junctional epithelium delivery method worked for three other prominent classes of vaccines: proteins, inactivated viruses and mRNA. In all three cases, the epithelial junction delivery technique produced robust antibody responses in the bloodstream and across mucosal surfaces.

The researchers also found that, at least in the animal model, it didn’t matter whether food and water were consumed immediately after flossing with the vaccine – the immune response was the same.

But while regular floss serves as an adequate vaccine delivery method for lab mice, the researchers know it’s not practical to ask people to hold vaccine-coated floss in their fingers. To address that challenge the researchers used a floss pick. A floss pick consists of a piece of floss stretched between two prongs that can be held by a handle.

Specifically, the researchers coated the floss in floss picks with fluorescent food dye. The researchers then recruited 27 study participants, explained the concept of applying vaccine via floss, and asked the participants to try to deposit the food dye in their epithelial junction with a floss pick.

“We found that approximately 60% of the dye was deposited in the gum pocket, which suggests that floss picks may be a practical vaccine delivery method to the epithelial junction,” Ingrole says.

“We’re optimistic about that work and – depending on our findings – may then move toward clinical trials,” Gill says.

While there are still many questions that need to be answered before the floss technique can be considered for clinical use, the researchers think there could be significant advantages beyond the improved antibody response on mucosal surfaces.

“For example, it would be easy to administer, and it addresses concerns many people have about being vaccinated with needles,” Gill says. “And we think this technique should be comparable in price to other vaccine delivery techniques.

There are also some drawbacks. For example, this technique would not work on infants and toddlers who do not yet have teeth.

“In addition, we would need to know more about how or whether this approach would work for people who have gum disease or other oral infections,” Gill says.

Reference: Ingrole RSJ, Shakya AK, Joshi G, et al. Floss-based vaccination targets the gingival sulcus for mucosal and systemic immunization. Nat Biomed Eng. 2025. doi: 10.1038/s41551-025-01451-3

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The Hey Geraldine chatbot helps social care staff tackle complex daily questions using AI trained by Geraldine Jinks herself.

Peterborough City Council has turned the knowledge of veteran therapy practitioner Geraldine Jinks into an AI chatbot to support adult social care workers.

After 35 years of experience, colleagues frequently approached Jinks seeking advice, leading to time pressures despite her willingness to help.

In response, the council developed a digital assistant called Hey Geraldine, which mimics her direct and friendly communication style to provide instant support to staff.

Developed in 2023, the chatbot offers practical answers to everyday care-related questions, such as how to support patients with memory issues or discharge planning. Jinks collaborated with the tech team to train the AI, writing all the responses herself to ensure consistency and clarity.

Thanks to its natural tone and humanlike advice, some colleagues even mistook the chatbot for the honest Geraldine.

The council hopes Hey Geraldine will reduce hospital discharge delays and improve patient access to assistive technology. Councillor Shabina Qayyum, who also works as a GP, said the tool empowers staff to help patients regain independence instead of facing unnecessary delays.

The chatbot is seen as preserving valuable institutional knowledge while improving frontline efficiency.

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