Diabetic neuropathy (DN) is a debilitating complication of diabetes mellitus (DM), characterized by progressive neuronal damage, sensory dysfunction, and impaired quality of life. Recent advances in exosome research have elucidated their crucial role in DN's pathogenesis, diagnosis, and treatment. Exosomes-nanoscale extracellular vesicles-function as vehicles for molecular cargo, including microRNAs (miRNAs), proteins, and lipids, which mediate intercellular communication and regulate key biological processes. Pathologically, hyperglycemia and hyperlipidemia induce the release of exosomes enriched with pathogenic miRNAs, such as miR-130a and miR-20b-3p, which disrupt neuronal function, axonal regeneration, and inflammatory pathways. Conversely, diagnostic studies highlight the utility of exosomal biomarkers like miR-7 and miR-221 in the early detection and monitoring of DN. Therapeutically, Schwann cell-derived and mesenchymal stromal cell (MSC)-derived exosomes demonstrate neuroprotective and reparative effects by enhancing mitochondrial function, modulating inflammation, and promoting axonal repair. Emerging approaches, including engineered exosomes and miRNA-enriched vesicles, further expand their therapeutic potential. Despite these advances, challenges such as standardization, large-scale production, and clinical validation remain in translating these findings into clinical practice. This review underscores the multifaceted roles of exosomes in DN and highlights their potential as innovative tools for precision diagnostics and targeted therapies, paving the way for future research and clinical applications.

: Diabetic sensorimotor polyneuropathy (DSP) is a common chronic diabetic complication. Traditionally, DSP was once considered irreversible with a typical loss of axon. However, the superimpose of acquired demyelination on axonal loss in DSP patients has been observed, implying that DSP may be preventable or reversible, particularly within a subgroup of patients exhibiting early-stage acquired demyelination, underscoring the critical importance of identifying early prognostic markers. : We systemically review the literature on the roles of biomarkers in predicting DSP and monitoring the progress. The underlying mechanisms of biomarkers were also discussed. : The pathogenesis of DSP is multifaceted, with various pathological mechanisms contributing to its development. Key mechanisms include aberrant glucose metabolism and induction of oxidative stress and inflammation. Several pathological processes, such as disrupted glucose metabolism, nerve damage, impaired microcirculation, genetic variants, and microRNA dysregulation, lead to molecular and protein changes that may be detectable in blood and other biological compartments, thus serving as potential biomarkers for DSP progression. However, the utility of a biomarker depends on its predictive accuracy, practicality, and ease of measurement. : Most biomarkers for predicting DSP have demonstrated suboptimal predictive value, and many lack established accuracy in forecasting DSP progression. Consequently, the diagnostic utility of any single biomarker remains limited. A comprehensive combination of biomarkers from various categories may hold incredible promise for accurate detection. As artificial intelligence (AI) techniques, especially machine learning, rapidly advance, these technologies may offer significant potential for developing diagnostic platforms to integrate and interpret complex biomarker data for DSP.

Diabetic neuropathy (DN) is a prevalent and debilitating complication of diabetes mellitus, significantly impacting patient quality of life and contributing to morbidity and mortality. Affecting approximately 50% of patients with diabetes, DN is predominantly characterized by distal symmetric polyneuropathy, leading to sensory loss, pain, and motor dysfunction, often resulting in diabetic foot ulcers and lower-limb amputations. The pathogenesis of DN is multifaceted, involving hyperglycemia, dyslipidemia, oxidative stress, mitochondrial dysfunction, and inflammation, which collectively damage peripheral nerves. Despite extensive research, disease-modifying treatments remain elusive, with current management primarily focusing on symptom control. This review explores the complex mechanisms underlying DN and highlights recent advances in diagnostic and therapeutic strategies. Emerging insights into the molecular and cellular pathways have unveiled potential targets for intervention, including neuroprotective agents, gene and stem cell therapies, and innovative pharmacological approaches. Additionally, novel diagnostic tools, such as corneal confocal microscopy and biomarker-based tests, have improved early detection and intervention. Lifestyle modifications and multidisciplinary care strategies can enhance patient outcomes. While significant progress has been made, further research is required to develop therapies that can effectively halt or reverse disease progression, ultimately improving the lives of individuals with DN. This review provides a comprehensive overview of current understanding and future directions in DN research and management.

PURPOSE OF REVIEW:Diabetic neuropathy is a debilitating complication of diabetes mellitus that affects millions of individuals worldwide. It is characterized by nerve damage resulting from prolonged exposure to high blood glucose levels. Diabetic neuropathy may cause a range of symptoms, including pain, numbness, muscle weakness, autonomic dysfunction, and foot ulcers, potentially causing significant impairment to the quality of life for those affected. This review article aims to provide a comprehensive overview of the pathophysiology of diabetic neuropathy. The etiology of diabetic neuropathy will be discussed, including risk factors, predisposing conditions, and an overview of the complex interplay between hyperglycemia, metabolic dysregulation, and nerve damage. Additionally, we will explore the molecular mechanisms and pathways of diabetic neuropathy, including the impact of hyperglycemia on nerve function, abnormalities in glucose metabolism, the role of advanced glycation end products (AGEs), and inflammatory and immune-mediated processes. We will provide an overview of the various nerve fibers affected by diabetic neuropathy and explore the common symptoms and complications associated with diabetic neuropathy in the pain medicine field. RECENT FINDINGS:This review highlights advances in understanding the pathophysiology of diabetic neuropathy as well as reviews potential novel therapeutic strategies and promising areas for future research. In conclusion, this review article aims to shed light on the pathophysiology of diabetic neuropathy, its far-reaching consequences, and the evolving strategies for prevention and management. In understanding the mechanisms of diabetic neuropathy and the ongoing research in this area, healthcare professionals can better serve patients with diabetes, ultimately improving well-being and reducing complications.

Diabetic peripheral neuropathy (DPN) refers to the development of peripheral nerve dysfunction in patients with diabetes when other causes are excluded. Diabetic distal symmetric polyneuropathy (DSPN) is the most representative form of DPN. As one of the most common complications of diabetes, its prevalence increases with the duration of diabetes. 10-15% of newly diagnosed T2DM patients have DSPN, and the prevalence can exceed 50% in patients with diabetes for more than 10 years. Bilateral limb pain, numbness, and paresthesia are the most common clinical manifestations in patients with DPN, and in severe cases, foot ulcers can occur, even leading to amputation. The etiology and pathogenesis of diabetic neuropathy are not yet completely clarified, but hyperglycemia, disorders of lipid metabolism, and abnormalities in insulin signaling pathways are currently considered to be the initiating factors for a range of pathophysiological changes in DPN. In the presence of abnormal metabolic factors, the normal structure and function of the entire peripheral nervous system are disrupted, including myelinated and unmyelinated nerve axons, perikaryon, neurovascular, and glial cells. In addition, abnormalities in the insulin signaling pathway will inhibit neural axon repair and promote apoptosis of damaged cells. Here, we will discuss recent advances in the study of DPN mechanisms, including oxidative stress pathways, mechanisms of microvascular damage, mechanisms of damage to insulin receptor signaling pathways, and other potential mechanisms associated with neuroinflammation, mitochondrial dysfunction, and cellular oxidative damage. Identifying the contributions from each pathway to neuropathy and the associations between them may help us to further explore more targeted screening and treatment interventions.

Diabetic neuropathy is a highly prevalent complication of diabetes. It consists of a broad range of neuropathic conditions, such as distal symmetric polyneuropathy and various forms of autonomic neuropathies involving the cardiovascular, gastrointestinal, and urogenital systems. Prevention or diagnosis in early stages of disease is crucial to prevent symptomatic onset and progression, particularly in the absence of current disease-modifying therapies. In this review, we describe the four main types of diabetic neuropathy. We review current understanding with respect to diagnosis and treatment while highlighting knowledge gaps and future directions.

BACKGROUND:Type 2 diabetes mellitus (T2DM) is a worldwide socioeconomic burden, and is accompanied by a variety of metabolic disorders, as well as nerve dysfunction referred to as diabetic neuropathy (DN). Despite a tremendous body of research, the pathogenesis of DN remains largely elusive. Currently, two schools of thought exist regarding the pathogenesis of diabetic neuropathy: a) mitochondrial-induced toxicity, and b) microvascular damage. Both mechanisms signify DN as an intractable disease and, as a consequence, therapeutic approaches treat symptoms with limited efficacy and risk of side effects. OBJECTIVE:Here, we propose that the human body exclusively employs mechanisms of adaptation to protect itself during an adverse event. For this purpose, two control systems are defined, namely the autonomic and the neural control systems. The autonomic control system responds via inflammatory and immune responses, while the neural control system regulates neural signaling, via plastic adaptation. Both systems are proposed to regulate a network of temporal and causative connections which unravel the complex nature of diabetic complications. RESULTS:A significant result of this approach infers that both systems make DN reversible, thus opening the door to novel therapeutic applications.

Type 2 diabetes is associated with many complications, including skeletal muscle atrophy. Ketogenic diets and low-carbohydrate diets (LCD) have recently been introduced as dietary interventions in patients with diabetes, but their effects on glucose and lipid metabolism in skeletal muscle have not been studied. In the current study, we compared the effects of LCD and ketogenic diet on glucose and lipid metabolism in skeletal muscle of diabetic mice. C57BL/6J mice with type 2 diabetes, constructed by a high-fat diet combined with streptozotocin, were fed a standard diet, a high-fat diet, an LCD, or a ketogenic diet for 14 weeks, respectively. Here, we found that the LCD, rather than the ketogenic diet, retained skeletal muscle weight and suppressed the expression of atrophy-related genes in diabetic mice. In addition, the LCD had more glycolytic/type IIb myofiber content and inhibited forkhead box O1 and pyruvate dehydrogenase kinase 4 expression, leading to improved glucose utilization. However, the ketogenic diet maintained more oxidative/type I myofibers. Moreover, compared with the ketogenic diet, the LCD decreased intramuscular triglycerides content and muscle lipolysis, suggesting improvement in lipid metabolism. Taken together, these data suggested that the LCD improved glucose utilization, and inhibited lipolysis and atrophy in skeletal muscle of diabetic mice, while the ketogenic diet showed metabolic disorders in skeletal muscle.

Diabetic peripheral neuropathy (DPN) is a major complication of diabetes mellitus with a high incidence. Oxidative stress, which is a crucial pathophysiological pathway of DPN, has attracted much attention. The distortion in the redox balance due to the overproduction of reactive oxygen species (ROS) and the deregulation of antioxidant defense systems promotes oxidative damage in DPN. Therefore, we have focused on the role of oxidative stress in the pathogenesis of DPN and elucidated its interaction with other physiological pathways, such as the glycolytic pathway, polyol pathway, advanced glycosylation end products, protein kinase C pathway, inflammation, and non-coding RNAs. These interactions provide novel therapeutic options targeting oxidative stress for DPN. Furthermore, our review addresses the latest therapeutic strategies targeting oxidative stress for the rehabilitation of DPN. Antioxidant supplements and exercise have been proposed as fundamental therapeutic strategies for diabetic patients through ROS-mediated mechanisms. In addition, several novel drug delivery systems can improve the bioavailability of antioxidants and the efficacy of DPN.

Diabetes prevalence continues to climb with the aging population. Type 2 diabetes (T2D), which constitutes most cases, is metabolically acquired. Diabetic peripheral neuropathy (DPN), the most common microvascular complication, is length-dependent damage to peripheral nerves. DPN pathogenesis is complex, but, at its core, it can be viewed as a state of impaired metabolism and bioenergetics failure operating against the backdrop of long peripheral nerve axons supported by glia. This unique peripheral nerve anatomy and the injury consequent to T2D underpins the distal-to-proximal symptomatology of DPN. Earlier work focused on the impact of hyperglycemia on nerve damage and bioenergetics failure, but recent evidence additionally implicates contributions from obesity and dyslipidemia. This review will cover peripheral nerve anatomy, bioenergetics, and glia-axon interactions, building the framework for understanding how hyperglycemia and dyslipidemia induce bioenergetics failure in DPN. DPN and painful DPN still lack disease-modifying therapies, and research on novel mechanism-based approaches is also covered.

Painful diabetic peripheral neuropathy (PDPN) is present in nearly a quarter of people with diabetes. It is estimated to affect over 100 million people worldwide. PDPN is associated with impaired daily functioning, depression, sleep disturbance, financial instability, and a decreased quality of life. Despite its high prevalence and significant health burden, it remains an underdiagnosed and undertreated condition. PDPN is a complex pain phenomenon with the experience of pain associated with and exacerbated by poor sleep and low mood. A holistic approach to patient-centred care alongside the pharmacological therapy is required to maximise benefit. A key treatment challenge is managing patient expectation, as a good outcome from treatment is defined as a reduction in pain of 30-50%, with a complete pain-free outcome being rare. The future for the treatment of PDPN holds promise, despite a 20-year void in the licensing of new analgesic agents for neuropathic pain. There are over 50 new molecular entities reaching clinical development and several demonstrating benefit in early-stage clinical trials. We review the current approaches to its diagnosis, the tools, and questionnaires available to clinicians, international guidance on PDPN management, and existing pharmacological and non-pharmacological treatment options. We synthesise evidence and the guidance from the American Association of Clinical Endocrinology, American Academy of Neurology, American Diabetes Association, Diabetes Canada, German Diabetes Association, and the International Diabetes Federation into a practical guide to the treatment of PDPN and highlight the need for future research into mechanistic-based treatments in order to prioritise the development of personalised medicine.

BACKGROUND AND OBJECTIVES:Damage to small nerve fibers is common in diabetic polyneuropathy (DPN), and the diagnosis of DPN relies on subjective symptoms and signs in a combination with objective confirmatory tests, typically electrophysiology or intraepidermal nerve fiber density (IENFD) from skin biopsy. Corneal confocal microscopy (CCM) has been introduced as a tool to detect DPN. However, it is unclear if CCM can reliably be used to diagnose DPN and how the technique compares with other commonly used measures of small fiber damage, such as IENFD, cold detection threshold (CDT), and warm detection threshold (WDT). Therefore, we assessed and compared the use of CCM, IENFD, CDT, and WDT in the diagnosis of DPN in patients with type 2 diabetes. METHODS:In this cohort study, the participants underwent detailed neurologic examination, electrophysiology, quantification of IENFD, CCM, and quantitative sensory testing. Definition of DPN was made in accordance with the Toronto criteria for diabetic neuropathy (without relying on IENFD and thermal thresholds). RESULTS:A total of 214 patients with at least probable DPN, 63 patients without DPN, and 97 controls without diabetes were included. Patients with DPN had lower CCM measures (corneal nerve fiber length [CNFL], nerve fiber density, and branch density), IENFD, CDT, and WDT compared with patients without DPN ( 0.001, <0.001, 0.002, < 0.001, = 0.003, and <0.005, respectively), whereas there was no difference between controls and patients with diabetes without DPN. All 3 CCM measures showed a very low diagnostic sensitivity with CNFL showing the highest (14.4% [95% CI 9.8-18.4]) and a specificity of 95.7% (88.0-99.1). In comparison, the sensitivity of abnormal CDT and/or WDT was 30.5% (24.4-37.0) with a specificity of 84.9% (74.6-92.2). The sensitivity of abnormal IENFD was highest among all measures with a value of 51.1% (43.7-58.5) and a specificity of 90% (79.5-96.2). CCM measures did not correlate with IENFD, CDT/WDT, or neuropathy severity in the group of patients with DPN. DISCUSSION:CCM measures showed the lowest sensitivity compared with other small fiber measures in the diagnosis of DPN. This indicates that CCM is not a sensitive method to detect DPN in recently diagnosed type 2 diabetes. CLASSIFICATION OF EVIDENCE:This study provides Class III evidence that CCM measures aid in the detection of DPN in recently diagnosed type 2 diabetics but with a low sensitivity when compared with other small fiber measures.

Diabetes represents a spectrum of disease in which metabolic dysfunction damages multiple organ systems including liver, kidneys and peripheral nerves. Although the onset and progression of these co-morbidities are linked with insulin resistance, hyperglycaemia and dyslipidaemia, aberrant non-essential amino acid (NEAA) metabolism also contributes to the pathogenesis of diabetes. Serine and glycine are closely related NEAAs whose levels are consistently reduced in patients with metabolic syndrome, but the mechanistic drivers and downstream consequences of this metabotype remain unclear. Low systemic serine and glycine are also emerging as a hallmark of macular and peripheral nerve disorders, correlating with impaired visual acuity and peripheral neuropathy. Here we demonstrate that aberrant serine homeostasis drives serine and glycine deficiencies in diabetic mice, which can be diagnosed with a serine tolerance test that quantifies serine uptake and disposal. Mimicking these metabolic alterations in young mice by dietary serine or glycine restriction together with high fat intake markedly accelerates the onset of small fibre neuropathy while reducing adiposity. Normalization of serine by dietary supplementation and mitigation of dyslipidaemia with myriocin both alleviate neuropathy in diabetic mice, linking serine-associated peripheral neuropathy to sphingolipid metabolism. These findings identify systemic serine deficiency and dyslipidaemia as novel risk factors for peripheral neuropathy that may be exploited therapeutically.

BACKGROUND AND PURPOSE:In Asian countries, herbal medicines have been used to treat diabetic peripheral neuropathy (DPN) as an adjunctive therapy. This review aims to assess the effectiveness and safety of herbal medicines for the treatment of DPN. METHODS:A literature search was conducted on PubMed, Embase, CENTRAL, Scopus, CINAHL, CNKI, DBPIA, and OASIS for randomized controlled trials that evaluated the effects of herbal medicines on DPN. The oral methylcobalamin administered group was selected as the control. The primary outcome measure was nerve conduction velocity (NCV), and the secondary outcome measure was the total efficacy rate (TER). The methodological quality of the included studies was assessed using the Cochrane risk of bias tool. A meta-analysis was conducted using Review Manager 5.4.1 software. RESULTS:Seventy-two RCTs with a total of 6260 patients were included. The meta-analysis showed that herbal medicine and co-administration of herbal medicine and methylcobalamin (CHM) treatment for DPN significantly increased the sensory nerve conduction velocity (SNCV) and motor nerve conduction velocity (MNCV) of the median and common peroneal nerves than methylcobalamin treatment alone. Herbal medicine and CHM treatment for DPN also significantly improved the TER compared to the control group. Herbal medicine and CHM treatment was found to be relatively safe. CONCLUSION:Our study suggests that herbal medicine and CHM might be more effective than methylcobalamin alone in the management of DPN. Further rigorous studies should be conducted to make more definite conclusions.

Diabetic peripheral neuropathy (DPN) occurs in up to half of individuals with type 1 or type 2 diabetes. DPN results from the distal-to-proximal loss of peripheral nerve function, leading to physical disability and sometimes pain, with the consequent lowering of quality of life. Early diagnosis improves clinical outcomes, but many patients still develop neuropathy. Hyperglycaemia is a risk factor and glycaemic control prevents DPN development in type 1 diabetes. However, glycaemic control has modest or no benefit in individuals with type 2 diabetes, probably because they usually have comorbidities. Among them, the metabolic syndrome is a major risk factor for DPN. The pathophysiology of DPN is complex, but mechanisms converge on a unifying theme of bioenergetic failure in the peripheral nerves due to their unique anatomy. Current clinical management focuses on controlling diabetes, the metabolic syndrome, and pain, but remains suboptimal for most patients. Thus, research is ongoing to improve early diagnosis and prognosis, to identify molecular mechanisms that could lead to therapeutic targets, and to investigate lifestyle interventions to improve clinical outcomes.