Pathogenesis and Molecular Treatment Strategies of Diabetic Neuropathy Collateral Glucose-Utilizing Pathways in Diabetic Polyneuropathy

Pathological evaluation of the pathogenesis of diabetes mellitus and diabetic peripheral neuropathy

Currently, there are more than 10 million patients with diabetes mellitus in Japan. Therefore, the need to explore the pathogenesis of diabetes and the complications leading to its cure is becoming increasingly urgent. Pathological examination of pancreatic tissues from patients with type 2 diabetes reveals a decrease in the volume of beta cells because of a combination of various stresses. In human type 2 diabetes, islet amyloid deposition is a unique pathological change characterized by proinflammatory macrophage (M1) infiltration into the islets. The pathological changes in the pancreas with islet amyloid were different according to clinical factors, which suggests that type 2 diabetes can be further subclassified based on islet pathology. On the other hand, diabetic peripheral neuropathy is the most frequent diabetic complication. In early diabetic peripheral neuropathy, M1 infiltration in the sciatic nerve evokes oxidative stress or attenuates retrograde axonal transport, as clearly demonstrated by in vitro live imaging. Furthermore, islet parasympathetic nerve density and beta cell volume were inversely correlated in type 2 diabetic Goto-Kakizaki rats, suggesting that diabetic peripheral neuropathy itself may contribute to the decrease in beta cell volume. These findings suggest that the pathogenesis of diabetes mellitus and diabetic peripheral neuropathy may be interrelated.

Moderate cryptoxanthin intake correlates with maintenance of a proper PINT index in a general Japanese population

INTRODUCTION

Small fibre neuropathy (SFN) is an early manifestation of diabetic polyneuropathy. Although oxidative stress, inflammation and change of intestinal bacterial population are assumed to be their pathogenesis, the effects of dietary nutrition have not been evaluated. The relationship between dietary nutrition intake and pain sensation was evaluated in the Japanese population.

METHODS

We conducted the Iwaki project, a population-based study recruiting 1,028 individuals, in 2018. The relationships between the pain threshold from intraepidermal electrical stimulation (PINT) and the amount of dietary nutrition evaluated by a brief-type self-administered diet history questionnaire were examined. The odds ratio was further explored after categorizing subjects based on low (< 63.7 μg/day), intermediate (63.7-159.2 μg/day), and high cryptoxanthin levels (> 159.2 μg/day).

RESULTS

Univariate linear regression analyses showed significant correlations between PINT and cryptoxanthin intake even after adjustments for other nutritional intakes (ß = 0.107, p < 0.01). Multivariate logistic regression analysis revealed low and high cryptoxanthin intake as significant risk factors for abnormal PINT (≥ 0.20 mA). Multivariate linear regression analyses showed significant correlations between PINT and cryptoxanthin intake levels after adjustment for other clinically PINT-related factors (ß = 0.09, p < 0.01).

CONCLUSIONS

Adequate intake of cryptoxanthin is recommended to maintain the pain threshold in the Japanese population.

Different Types of Cell Death in Diabetic Neuropathy: A Focus on Mechanisms and Therapeutic Strategies

Diabetic neuropathy (DN) is a common complication of diabetes, affecting over 50% of patients, leading to significant pain and a burden. Currently, there are no effective treatments available. Cell death is considered a key factor in promoting the progression of DN. This article reviews how cell death is initiated in DN, emphasizing the critical roles of oxidative stress, mitochondrial dysfunction, inflammation, endoplasmic reticulum stress, and autophagy. Additionally, we thoroughly summarize the mechanisms of cell death that may be involved in the pathogenesis of DN, including apoptosis, autophagy, pyroptosis, and ferroptosis, among others, as well as potential therapeutic targets offered by these death mechanisms. This provides potential pathways for the prevention and treatment of diabetic neuropathy in the future.

Recent Advances in Biomolecular Patho-Mechanistic Pathways behind the Development and Progression of Diabetic Neuropathy

Diabetic neuropathy (DN) is a neurodegenerative disorder that is primarily characterized by distal sensory loss, reduced mobility, and foot ulcers that may potentially lead to amputation. The multifaceted etiology of DN is linked to a range of inflammatory, vascular, metabolic, and other neurodegenerative factors. Chronic inflammation, endothelial dysfunction, and oxidative stress are the three basic biological changes that contribute to the development of DN. Although our understanding of the intricacies of DN has advanced significantly over the past decade, the distinctive mechanisms underlying the condition are still poorly understood, which may be the reason behind the lack of an effective treatment and cure for DN. The present study delivers a comprehensive understanding and highlights the potential role of the several pathways and molecular mechanisms underlying the etiopathogenesis of DN. Moreover, Schwann cells and satellite glial cells, as integral factors in the pathogenesis of DN, have been enlightened. This work will motivate allied research disciplines to gain a better understanding and analysis of the current state of the biomolecular mechanisms behind the pathogenesis of DN, which will be essential to effectively address every facet of DN, from prevention to treatment.

Pectin as a biofunctional food: comprehensive overview of its therapeutic effects and antidiabetic-associated mechanisms

Pectin is a complex polysaccharide found in a variety of fruits and vegetables. It has been shown to have potential antidiabetic activity along with other biological activities, including cholesterol-lowering properties, antioxidant activity, anti-inflammatory and immune-modulatory effects, augmented healing of diabetic foot ulcers and other health benefits. There are several pectin-associated antidiabetic mechanisms, such as the regulation of glucose metabolism, reduction of oxidative stress, increased insulin sensitivity, appetite suppression and modulation of the gut microbiome. Studies have shown that pectin supplementation has antidiabetic effects in different animal models and in vitro. In human studies, pectin has been found to have a positive effect on blood glucose control, particularly in individuals with type 2 diabetes. Pectin also shows synergistic effects by enhancing the potency and efficacy of antidiabetic drugs when taken together. In conclusion, pectin has the potential to be an effective antidiabetic agent. However, further research is needed to fully understand its detailed molecular mechanisms in various animal models, functional food formulations and safety profiles for the treatment and management of diabetes and associated complications in humans. The current study was carried out to provide the critical approach towards therapeutical potential, anti-diabetic potential and underlying molecular mechanisms on the basis of existing knowledge.

How inflammation dictates diabetic peripheral neuropathy: An enlightening review

BACKGROUND

Diabetic peripheral neuropathy (DPN) constitutes a debilitating complication associated with diabetes. Although, the past decade has seen rapid developments in understanding the complex etiology of DPN, there are no approved therapies that can halt the development of DPN, or target the damaged nerve. Therefore, clarifying the pathogenesis of DPN and finding effective treatment are the crucial issues for the clinical management of DPN.

AIMS

This review is aiming to summary the current knowledge on the pathogenesis of DPN, especially the mechanism and application of inflammatory response.

METHODS

We systematically summarized the latest studies on the pathogenesis and therapeutic strategies of diabetic neuropathy in PubMed.

RESULTS

In this seminal review, the underappreciated role of immune activation in the progression of DPN is scrutinized. Novel insights into the inflammatory regulatory mechanisms of DPN have been unearthed, illuminating potential therapeutic strategies of notable clinical significance. Additionally, a nuanced examination of DPN's complex etiology, including aberrations in glycemic control and insulin signaling pathways, is presented. Crucially, an emphasis has been placed on translating these novel understandings into tangible clinical interventions to ameliorate patient outcomes.

CONCLUSIONS

This review is distinguished by synthesizing cutting-edge mechanisms linking inflammation to DPN and identifying innovative, inflammation-targeted therapeutic approaches.

Tryptophan metabolism and small fibre neuropathy: a correlation study

Small nerve fibres located in the epidermis sense pain. Dysfunction of these fibres decreases the pain threshold known as small fibre neuropathy. Diabetes mellitus is accompanied by metabolic changes other than glucose, synergistically eliciting small fibre neuropathy. These findings suggest that various metabolic changes may be involved in small fibre neuropathy. Herein, we explored the correlation between pain sensation and changes in plasma metabolites in healthy Japanese subjects. The pain threshold evaluated from the intraepidermal electrical stimulation was used to quantify pain sensation in a total of 1021 individuals in the 2017 Iwaki Health Promotion Project. Participants with a pain threshold evaluated from the intraepidermal electrical stimulation index <0.20 mA were categorized into the pain threshold evaluated from the intraepidermal electrical stimulation index-low group (n = 751); otherwise, they were categorized into the pain threshold evaluated from the intraepidermal electrical stimulation index-high group (n = 270). Metabolome analysis of plasma was conducted using capillary electrophoresis time-of-flight mass spectrometry. The metabolite set enrichment analysis revealed that the metabolism of tryptophan was significantly correlated with the pain threshold evaluated from the intraepidermal electrical stimulation index in all participants (P < 0.05). The normalized level of tryptophan was significantly decreased in participants with a high pain threshold evaluated from the intraepidermal electrical stimulation index. In addition to univariate linear regression analyses, the correlation between tryptophan concentration and the pain threshold evaluated from the intraepidermal electrical stimulation index remained significant after adjustment for multiple factors (β = -0.07615, P < 0.05). These findings indicate that specific metabolic changes are involved in the deterioration of pain thresholds. Here, we show that abnormal tryptophan metabolism is significantly correlated with an elevated pain threshold evaluated from the intraepidermal electrical stimulation index in the Japanese population. This correlation provides insight into the pathology and clinical application of small fibre neuropathy.

Cell metabolism pathways involved in the pathophysiological changes of diabetic peripheral neuropathy

Diabetic peripheral neuropathy is a common complication of diabetes mellitus. Elucidating the pathophysiological metabolic mechanism impels the generation of ideal therapies. However, existing limited treatments for diabetic peripheral neuropathy expose the urgent need for cell metabolism research. Given the lack of comprehensive understanding of energy metabolism changes and related signaling pathways in diabetic peripheral neuropathy, it is essential to explore energy changes and metabolic changes in diabetic peripheral neuropathy to develop suitable treatment methods. This review summarizes the pathophysiological mechanism of diabetic peripheral neuropathy from the perspective of cellular metabolism and the specific interventions for different metabolic pathways to develop effective treatment methods. Various metabolic mechanisms (e.g., polyol, hexosamine, protein kinase C pathway) are associated with diabetic peripheral neuropathy, and researchers are looking for more effective treatments through these pathways.

Diabetic peripheral neuropathy: pathogenetic mechanisms and treatment

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.

Painful Diabetic Neuropathy: The Need for New Approaches

Painful diabetic neuropathy is a common vexing problem for people with diabetes and a costly problem for society. The pathophysiology is not well understood, and no safe and effective mechanistically-based treatment has been identified. Poor glycemic control is a risk factor for painful diabetic neuropathy. Excessive intraneuronal glucose in people with diabetes can be shunted away from physiological glycolysis into multiple pathological pathways associated with neuropathy and pain. The first three treatments that are traditionally offered consist of risk factor reduction, lifestyle modifications, and pharmacological therapy, which includes only three drugs that are approved for this indication by the United States Food and Drug Administration. All of these traditional treatments are often inadequate for relieving neuropathic pain, and thus, new approaches are needed. Modern devices based on neuromodulation technology, which act directly on the nervous system, have been recently cleared by the United States Food and Drug Administration for painful diabetic neuropathy and offer promise as next-in-line therapy when traditional therapies fail.

Metabolite profiles of diabetes mellitus and response to intervention in anti-hyperglycemic drugs

Type 2 diabetes mellitus (T2DM) has become a major health problem, threatening the quality of life of nearly 500 million patients worldwide. As a typical multifactorial metabolic disease, T2DM involves the changes and interactions of various metabolic pathways such as carbohydrates, amino acid, and lipids. It has been suggested that metabolites are not only the endpoints of upstream biochemical processes, but also play a critical role as regulators of disease progression. For example, excess free fatty acids can lead to reduced glucose utilization in skeletal muscle and induce insulin resistance; metabolism disorder of branched-chain amino acids contributes to the accumulation of toxic metabolic intermediates, and promotes the dysfunction of β-cell mitochondria, stress signal transduction, and apoptosis. In this paper, we discuss the role of metabolites in the pathogenesis of T2DM and their potential as biomarkers. Finally, we list the effects of anti-hyperglycemic drugs on serum/plasma metabolic profiles.

New perspectives in diabetic neuropathy

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.

Understanding the role of hyperglycemia and the molecular mechanism associated with diabetic neuropathy and possible therapeutic strategies

Diabetic neuropathy is a neuro-degenerative disorder that encompasses numerous factors that impact peripheral nerves in the context of diabetes mellitus (DM). Diabetic peripheral neuropathy (DPN) is very prevalent and impacts 50% of diabetic patients. DPN is a length-dependent peripheral nerve lesion that primarily causes distal sensory loss, discomfort, and foot ulceration that may lead to amputation. The pathophysiology is yet to be fully understood, but current literature on the pathophysiology of DPN revolves around understanding various signaling cascades involving the polyol, hexosamine, protein-kinase C, AGE, oxidative stress, and poly (ADP ribose) polymerase pathways. The results of research have suggested that hyperglycemia target Schwann cells and in severe cases, demyelination resulting in central and peripheral sensitization is evident in diabetic patients. Various diagnostic approaches are available, but detection at an early stage remains a challenge. Traditional analgesics and opioids that can be used "as required" have not been the mainstay of treatment thus far. Instead, anticonvulsants and antidepressants that must be taken routinely over time have been the most common treatments. For now, prolonging life and preserving the quality of life are the ultimate goals of diabetes treatment. Furthermore, the rising prevalence of DPN has substantial consequences for occupational therapy because such therapy is necessary for supporting wellness, warding off other chronic-diseases, and avoiding the development of a disability; this is accomplished by engaging in fulfilling activities like yoga, meditation, and physical exercise. Therefore, occupational therapy, along with palliative therapy, may prove to be crucial in halting the onset of neuropathic-symptoms and in lessening those symptoms once they have occurred.

Dual epigenetic changes in diabetes mellitus-associated pancreatic ductal adenocarcinoma correlate with downregulation of E-cadherin and worsened prognosis

Diabetes mellitus (DM) is a risk factor for pancreatic ductal adenocarcinoma (PDAC) that promotes the promoter methylation of CDH1. It is still unclear whether DM can exert other epigenetic effects, such as altering microRNA (miR) expression, in PDAC. The expression of miR-100-5p is known to be changed in DM patients and can suppress the expression of E-cadherin. In this study, the correlation between DM status and dual epigenetic changes was evaluated in PDAC specimens from patients who underwent radical surgical resection. A total of 132 consecutive patients with PDAC were clinicopathologically evaluated. E-cadherin and nuclear β-catenin expression was measured using immunohistochemistry. DNA and miRs were extracted from the main tumor site on formalin-fixed paraffin-embedded tissue sections. TaqMan miR assays were applied to assess miR-100-5p expression. Bisulfite modification was conducted on the extracted DNA, which was then subjected to methylation-specific polymerase chain reaction. Immunohistochemistry revealed that decreased E-cadherin expression and increased nuclear β-catenin expression were significantly associated with DM and poor tumor cell differentiation. The presence of long-duration DM (≥3 years)  was a significant factor contributing to CDH1 promoter methylation (p < 0.01), while miR-100-5p expression was proportionally correlated with the preoperative HbA1c level (R = 0.34, p < 0.01), but not the duration of DM. The subjects with high miR-100-5p expression and CDH1 promoter methylation showed the highest level of vessel invasion and prevalence of tumor size ≥30 mm. PDAC subjects with dual epigenetic changes showed poorer overall survival (OS) than those with a single epigenetic change. miR-100-5p expression ≥4.13 and CDH1 promoter methylation independently predicted poor OS and disease-free survival (DFS) in the multivariate analysis. OS and DFS worsened in DM subjects with both HbA1c ≥ 6.5% and DM duration ≥3 years. Thus, DM is associated with two modes of epigenetic change by independent mechanisms and worsens prognosis.

Issues and challenges in diabetic neuropathy management: A narrative review

Diabetic neuropathy (DN) is a devastating disorder with an increasing prevalence globally. This epidemic can pose a critical burden on individuals and com-munities, subsequently affecting the productivity and economic output of a country. With more people living a sedentary lifestyle, the incidence of DN is escalating worldwide. Many researchers have relentlessly worked on ways to combat this devastating disease. Their efforts have given rise to a number of commercially available therapies that can alleviate the symptoms of DN. Unfortunately, most of these therapies are only partially effective. Worse still, some are associated with unfavorable side effects. This narrative review aims to highlight current issues and challenges in the management of DN, especially from the perspective of molecular mechanisms that lead to its progression, with the hope of providing future direction in the management of DN. To improve the approaches to diabetic management, the suggested resolutions in the literature are also discussed in this review. This review will provide an in-depth understanding of the causative mechanisms of DN, apart from the insights to improve the quality and strategic approaches to DN management.

Molecular Insights of Plant Phytochemicals Against Diabetic Neuropathy

Diabetes and its associated complications including diabetic neuropathy have become a menacing headache for health workers and scientists all over the world. The number of diabetic individuals has been growing exponentially every day while the entire medical fraternity feels crippled and unable to handle such an enormous and anarchical scenario. The disease also demonstrates itself in the patients in numerous ways ranging from a little discomfort to death. Diabetic neuropathy has a poor prognosis since it might go unnoticed for years after the onset of diabetes. The etiology of the disease has been linked to oxidative stress caused by increased free radical production. Hyperglycemia causes multiple metabolic pathways to be activated, as well as significant oxidative stress, which becomes the major cause of cell death, culminating in Diabetic Neuropathy. So, it is the need of the hour to find out permanent treatment for this life-threatening disease. The primary goal of this study is to emphasize the potential importance of numerous processes and pathways in the development of diabetic neuropathy as well as the possible role of plant metabolites to control the disease at a molecular level. A possible mechanism was also summarized in the study about scavenging the reactive oxygen species by a flavonoid component. The study also covered the in vivo data of various plants and some of the flavonoid compounds actively studied against Diabetic Neuropathy by inhibiting or reducing the contributing factors such as proinflammatory cytokines, ROS, RNS inhibition, and upregulating the various cellular antioxidants such as GSH, SOD, and CAT.

RAGE activation in macrophages and development of experimental diabetic polyneuropathy

It is suggested that activation of receptor for advanced glycation end products (RAGE) induces proinflammatory response in diabetic nerve tissues. Macrophage infiltration is invoked in the pathogenesis of diabetic polyneuropathy (DPN), while the association between macrophage and RAGE activation and the downstream effects of macrophages remain to be fully clarified in DPN. This study explored the role of RAGE in the pathogenesis of DPN through the modified macrophages. Infiltrating proinflammatory macrophages impaired insulin sensitivity, atrophied the neurons in dorsal root ganglion, and slowed retrograde axonal transport (RAT) in the sciatic nerve of type 1 diabetic mice. RAGE-null mice showed an increase in the population of antiinflammatory macrophages, accompanied by intact insulin sensitivity, normalized ganglion cells, and RAT. BM transplantation from RAGE-null mice to diabetic mice protected the peripheral nerve deficits, suggesting that RAGE is a major determinant for the polarity of macrophages in DPN. In vitro coculture analyses revealed proinflammatory macrophage-elicited insulin resistance in the primary neuronal cells isolated from dorsal root ganglia. Applying time-lapse recording disclosed a direct impact of proinflammatory macrophage and insulin resistance on the RAT deficits in primary neuronal cultures. These results provide a potentially novel insight into the development of RAGE-related DPN.

Aspalathin and Other Rooibos Flavonoids Trapped α-Dicarbonyls and Inhibited Formation of Advanced Glycation End Products In Vitro

The excessive dietary intake of simple sugars and abnormal metabolism in certain diseases contribute to the increased production of α-dicarbonyls (α-DCs), such as methylglyoxal (MGO) and glyoxal (GO), the main precursors of the formation of advanced glycation end products (AGEs). AGEs play a vital role, for example, in the development of cardiovascular diseases and diabetes. Aspalathus linearis (Burman f.) R. Dahlgren (known as rooibos tea) exhibits a wide range of activities beneficial for cardio-metabolic health. Thus, the present study aims to investigate unfermented and fermented rooibos extracts and their constituents for the ability to trap MGO and GO. The individual compounds identified in extracts were tested for the capability to inhibit AGEs (with MGO or GO as a glycation agent). Ultra-high-performance liquid chromatography coupled with an electrospray ionization mass spectrometer (UHPLC-ESI-MS) was used to investigate α-DCs' trapping capacities. To evaluate the antiglycation activity, fluorescence measurement was used. The extract from the unfermented rooibos showed a higher ability to capture MGO/GO and inhibit AGE formation than did the extract from fermented rooibos, and this effect was attributed to a higher content of dihydrochalcones. The compounds detected in the extracts, such as aspalathin, nothofagin, vitexin, isovitexin, and eriodictyol, as well as structurally related phloretin and phloroglucinol (formed by the biotransformation of certain flavonoids), trapped MGO, and some also trapped GO. AGE formation was inhibited the most by isovitexin. However, it was the high content of aspalathin and its higher efficiency than that of metformin that determined the antiglycation and trapping properties of green rooibos. Therefore, A. linearis, in addition to other health benefits, could potentially be used as an α-DC trapping agent and AGE inhibitor.

GC × GC-TOFMS metabolomics analysis identifies elevated levels of plasma sugars and sugar alcohols in diabetic mellitus patients with kidney failure

Two dimensional GC (GC × GC)-time-of-flight mass spectrometry (TOFMS) has been used to improve accurate metabolite identification in the chemical industry, but this method has not been applied as readily in biomedical research. Here, we evaluated and validated the performance of high resolution GC × GC-TOFMS against that of GC-TOFMS for metabolomics analysis of two different plasma matrices, from healthy controls (CON) and diabetes mellitus (DM) patients with kidney failure (DM with KF). We found GC × GC-TOFMS outperformed traditional GC-TOFMS in terms of separation performance and metabolite coverage. Several metabolites from both the CON and DM with KF matrices, such as carbohydrates and carbohydrate-conjugate metabolites, were exclusively detected using GC × GC-TOFMS. Additionally, we applied this method to characterize significant metabolites in the DM with KF group, with focused analysis of four metabolite groups: sugars, sugar alcohols, amino acids, and free fatty acids. Our plasma metabolomics results revealed 35 significant metabolites (12 unique and 23 concentration-dependent metabolites) in the DM with KF group, as compared with those in the CON and DM groups (N = 20 for each group). Interestingly, we determined 17 of the 35 (14/17 verified with reference standards) significant metabolites identified from both the analyses were metabolites from the sugar and sugar alcohol groups, with significantly higher concentrations in the DM with KF group than in the CON and DM groups. Enrichment analysis of these 14 metabolites also revealed that alterations in galactose metabolism and the polyol pathway are related to DM with KF. Overall, our application of GC × GC-TOFMS identified key metabolites in complex plasma matrices.

Use of Ferulic Acid in the Management of Diabetes Mellitus and Its Complications

Diabetes mellitus, a metabolic disease mainly characterized by hyperglycemia, is becoming a serious social health problem worldwide with growing prevalence. Many natural compounds have been found to be effective in the prevention and treatment of diabetes, with negligible toxic effects. Ferulic acid (FA), a phenolic compound commonly found in medicinal herbs and the daily diet, was proved to have several pharmacological effects such as antihyperglycemic, antihyperlipidemic and antioxidant actions, which are beneficial to the management of diabetes and its complications. Data from PubMed, EM-BASE, Web of Science and CNKI were searched with the keywords ferulic acid and diabetes mellitus. Finally, 28 articles were identified after literature screening, and the research progress of FA for the management of DM and its complications was summarized in the review, in order to provide references for further research and medical applications of FA.

Beyond Wrapping: Canonical and Noncanonical Functions of Schwann Cells

Schwann cells in the peripheral nervous system (PNS) are essential for the support and myelination of axons, ensuring fast and accurate communication between the central nervous system and the periphery. Schwann cells and related glia accompany innervating axons in virtually all tissues in the body, where they exhibit remarkable plasticity and the ability to modulate pathology in extraordinary, and sometimes surprising, ways. Here, we provide a brief overview of the various glial cell types in the PNS and describe the cornerstone cellular and molecular processes that enable Schwann cells to perform their canonical functions. We then dive into discussing exciting noncanonical functions of Schwann cells and related PNS glia, which include their role in organizing the PNS, in regulating synaptic activity and pain, in modulating immunity, in providing a pool of stem cells for different organs, and, finally, in influencing cancer.

Plasma C1q/tumor necrosis factor-related protein-3 concentrations are associated with diabetic peripheral neuropathy

INTRODUCTION

To analyze the associations of circulating C1q/tumor necrosis factor-related protein-3 (CTRP3) concentrations with several metabolic parameters and to investigate the possible role of CTRP3 in subjects with diabetic peripheral neuropathy (DPN).

RESEARCH DESIGN AND METHODS

A total of 347 participants were recruited in this study, and plasma CTRP3 concentrations were analyzed in subjects with DPN (n=172) and without DPN (non-DPN, n=175). The nerve conduction test and oral glucose tolerance test were performed, and Neuropathy Symptom Score (NSS)/Neuropathy Disability Score (NDS) and biochemical parameters were measured in all participants.

RESULTS

Plasma CTRP3 concentrations were significantly lower in patients with DPN compared with those in patients with diabetes without DPN (p<0.01), despite the comparable glucose and lipid metabolism levels in both groups. Groups with a higher plasma CTRP3 level had a faster nerve conduction velocity. In addition, plasma CTRP3 concentrations were negatively correlated with hemoglobin A1c (HbA1c), urea acid (UA), triglyceride, NSS and NDS (p<0.05) after being adjusted for age and sex. Multivariate logistic regression analysis revealed that plasma CTRP3 concentrations were significantly correlated with DPN after being controlled for age, sex, body mass index, HbA1c, blood pressure, lipid profiles, and renal function.

CONCLUSIONS

Plasma CTRP3 concentrations were significantly lower in patients with DPM and positively correlated with nerve conduction velocity. The relationship between CTRP3 levels and DPN is independent of the glucose and lipid status. Therefore, circulating CTRP3 might serve as a predictor of impairment of nerve conduction in patients with DPN.

miR-27b-3p Improved High Glucose-Induced Spermatogenic Cell Damage via Regulating Gfpt1/HBP Signaling

INTRODUCTION

Diabetes mellitus (DM)-induced testicular damage is characterized by abnormal apoptosis of spermatogenic cells. Here, we clarified the roles and the molecular mechanism of microRNA (miR)-27b-3p in high glucose (HG)-induced spermatogenic cell damage.

METHODS

GC-1 spg cells were treated with 30 mmol/L glucose for 24 h. Cell viability was assessed by 2.3 3-(4, 5-dimethylthiazolyl2)-2, 5-diphenyltetrazolium bromide (MTT) assay. And, levels of O-linked N-acetylglucosamine (OGT), apoptosis-related proteins, and autophagy-related proteins were evaluated using Western blot. Levels of tumor necrosis factor-α (TNF-α), IL-1β, IL-6, and UDP-N-acetylglucosamine (UDP-GlcNAc) were assessed by enzyme linked immunosorbent (ELISA) assay. Levels of reactive oxygen species (ROS), malonic dialdehyde (MDA) and activity of superoxide dismutase (SOD) in cells were determined using kits. Cell apoptosis was determined using flow cytometry assay. Besides, dual luciferase reporter assay was employed to verify the binding relationship between miR-27b-3p and glutamine-fructose-6-phosphate transaminase 1 (Gfpt1).

RESULTS

miR-27b-3p was markedly downregulated in HG-treated GC-1 spg cells. HG treatment caused decreased cell viability, increased oxidative stress and inflammation, and induced autophagy and apoptosis, which were abolished by miR-27b-3p overexpression. miR-27b-3p suppressed the activation of hexosamine biosynthetic pathway (HBP) signaling in HG-treated spermatogenic cells. miR-27b-3p directly bound to Gfpt1 and negatively regulated its expression.

CONCLUSION

miR-27b-3p could improve HG-induced spermatogenic cell damage via regulating Gfpt1/HBP signaling, providing a new treatment strategy for the treatment of DM-induced testicular damage.

Pharmacotherapy of Painful Diabetic Neuropathy: A Clinical Update

The rising prevalence of diabetes mellitus (DM) leads on to an increase in chronic diabetic complications. Diabetic peripheral neuropathies (DPNs) are common chronic complications of diabetes. Distal symmetric polyneuropathy is the most prevalent form. Most patients with DPN will remain pain-free; however, painful DPN (PDPN) occurs in 6-34% of all DM patients and is associated with reduced health-related-quality-of-life and substantial economic burden. Symptomatic treatment of PDPN and diabetic autonomic neuropathy is the key treatment goals. Using certain patient related characteristics, subjects with PDPN can be stratified and assigned targeted therapies to produce better pain outcomes. The aim of this review is to discuss the various pathogenetic mechanisms of DPN with special reference to the mechanisms leading to PDPN and the various pharmacological and non-pharmacological therapies available for its management. Recommended pharmacological therapies include anticonvulsants, antidepressants, opioid analgesics, and topical medications.

The role of gel wound dressings loaded with stem cells in the treatment of diabetic foot ulcers

Diabetic foot ulcers (DFUs) are a serious complication of diabetes and the main cause of nontraumatic lower limb amputations, resulting in a serious economic burden on society. The main causes of DFUs include peripheral neuropathy, foot deformity, chronic inflammation, and peripheral artery disease. There are many clinical approaches for the treatment of DFUs, but they are all aimed at addressing a single aetiological factor. Stem cells (SCs), which express many cytokines and a variety of nerve growth factors and modulate immunological function in the wound, may accelerate DFU healing by promoting angiogenesis, cell proliferation, and nerve growth and regulating the inflammatory response. However, the survival time of SCs without scaffold support in the wound is short. Multifunctional gel wound dressings play a critical role in skin wound healing due to their ability to maintain SC survival for a long time, provide moisture and prevent electrolyte and water loss in DFUs. Among the many methods for clinical treatment of DFUs, the most successful one is therapy with gel dressings loaded with SCs. To accelerate DFU healing, gel wound dressings loaded with SCs are needed to promote the survival and migration of SCs and increase wound contraction. This review summarizes the research advancements regarding multifunctional gel wound dressings and SCs in the treatment of DFU to demonstrate the effectiveness and safety of this combinational therapeutic strategy.

Physiological and Pathological Roles of Aldose Reductase

Aldose reductase (AR) is an aldo-keto reductase that catalyzes the first step in the polyol pathway which converts glucose to sorbitol. Under normal glucose homeostasis the pathway represents a minor route of glucose metabolism that operates in parallel with glycolysis. However, during hyperglycemia the flux of glucose via the polyol pathway increases significantly, leading to excessive formation of sorbitol. The polyol pathway-driven accumulation of osmotically active sorbitol has been implicated in the development of secondary diabetic complications such as retinopathy, nephropathy, and neuropathy. Based on the notion that inhibition of AR could prevent these complications a range of AR inhibitors have been developed and tested; however, their clinical efficacy has been found to be marginal at best. Moreover, recent work has shown that AR participates in the detoxification of aldehydes that are derived from lipid peroxidation and their glutathione conjugates. Although in some contexts this antioxidant function of AR helps protect against tissue injury and dysfunction, the metabolic transformation of the glutathione conjugates of lipid peroxidation-derived aldehydes could also lead to the generation of reactive metabolites that can stimulate mitogenic or inflammatory signaling events. Thus, inhibition of AR could have both salutary and injurious outcomes. Nevertheless, accumulating evidence suggests that inhibition of AR could modify the effects of cardiovascular disease, asthma, neuropathy, sepsis, and cancer; therefore, additional work is required to selectively target AR inhibitors to specific disease states. Despite past challenges, we opine that a more gainful consideration of therapeutic modulation of AR activity awaits clearer identification of the specific role(s) of the AR enzyme in health and disease.

Diversity of pathophysiology in type 2 diabetes shown by islet pathology

The etiology of type 2 diabetes is multifactorial, in which environmental and genetic factors are involved to varying degrees. This suggests that its pathophysiology might vary depending on the individuals. Knowledge of the differences is critical, because these differences are directly linked to the care and treatment of the patients. Recent studies have attempted to carry out subclassifications of type 2 diabetes based on clinical and genetic differences. However, there is no pathological evidence to support these subclassifications. The pathophysiology of type 2 diabetes is generally divided into insulin resistance in peripheral tissues and pancreatic islet dysfunction. Among them, islet dysfunction causes a deficit in insulin secretion from β-cells. In particular, a deficit in insulin secretion is ascribed to a combination of disruption of the insulin secretory machinery and a decrease in β-cell volume in type 2 diabetes. Recent research has suggested that transdifferentiation and dedifferentiation are involved in the decrease in β-cell volume, and that it might change dynamically depending on the glucose metabolic state. However, it is possible that the numbers of islet cells are decreased in type 2 diabetes. In particular, the loss of endocrine cells due to islet amyloid deposits is an important pathological change in type 2 diabetes in humans. These results show that pathological changes of the islets can be different in each individuals with type 2 diabetes and reflect each pathophysiology, which is useful in establishing further subclassifications and developing tailor-made therapies for type 2 diabetes.

Interventional Clinical Trials on Diabetic Peripheral Neuropathy: A Retrospective Analysis

AIMS/INTRODUCTION

Diabetic peripheral neuropathy (DPN) is the most common complication of diabetes. At present, there is no comprehensive summary of the clinical trials related to DPN. In this article, we summarized the basic characteristics of the interventional clinical trials pertaining to DPN to determine the current status of research in this field and the existing issues.

MATERIALS AND METHODS

We searched the World Health Organization International Clinical Trial Registration Platform (ICTRP), PubMed and Web of Science for clinical trials from 2005 to April 2021 and extracted 149 registered and 459 published clinical trials on DPN. We summarized the characteristics of the clinical trials, including the source registration, recruitment status, stage, age group, allocation method, intervention, end point classification, funding source, and treatment.

RESULTS

After excluding noninterventional and nontreatment trials, 149 registered clinical trials out of 292 records from 12 registration centers and 459 published articles were included in this study. Among the registered trials, 43% had been completed, and 34.4% had been published in peer-reviewed journals. Among these trials, more than half used random allocation and blinded placebo-controlled methodologies. A total of 40.3% of the trials were multicenter studies, 63.8% of the treatments were drug therapies, and the endpoint classifications of 49% were efficacy and safety. Of the 459 published interventional clinical trials on DPN, 69.7% of the trials used drug treatments; more than half were randomized, double-blind, placebo-controlled clinical trials; 94.1% had positive outcomes; 46.4% had a target size of 50; and 22.9% were multicenter.

CONCLUSION

This paper systematically summarizes the current status of interventional trials on DPN registered in the ICTRP and published clinical trials and provides a reference for the development of high-quality intervention strategies for DPN in the future.

Essential Oil of Croton zehntneri Prevents Conduction Alterations Produced by Diabetes Mellitus on Vagus Nerve

Autonomic diabetic neuropathy (ADN) is a complication of diabetes mellitus (DM), to which there is no specific treatment. In this study, the efficacy of the essential oil of Croton zehntneri (EOCz) in preventing ADN was evaluated in the rat vagus nerve. For the two fastest conducting myelinated types of axons of the vagus nerve, the conduction velocities and rheobase decreased, whilst the duration of the components of the compound action potential of these fibers increased. EOCz completely prevented these DM-induced alterations of the vagus nerve. Unmyelinated fibers were not affected. In conclusion, this investigation demonstrated that EOCz is a potential therapeutic agent for the treatment of ADN.

Diabetic heart disease: A clinical update

Diabetes mellitus (DM) significantly increases the risk of heart disease, and DM-related healthcare expenditure is predominantly for the management of cardiovascular complications. Diabetic heart disease is a conglomeration of coronary artery disease (CAD), cardiac autonomic neuropathy (CAN), and diabetic cardiomyopathy (DCM). The Framingham study clearly showed a 2 to 4-fold excess risk of CAD in patients with DM. Pathogenic mechanisms, clinical presentation, and management options for DM-associated CAD are somewhat different from CAD among nondiabetics. Higher prevalence at a lower age and more aggressive disease in DM-associated CAD make diabetic individuals more vulnerable to premature death. Although common among diabetic individuals, CAN and DCM are often under-recognised and undiagnosed cardiac complications. Structural and functional alterations in the myocardial innervation related to uncontrolled diabetes result in damage to cardiac autonomic nerves, causing CAN. Similarly, damage to the cardiomyocytes from complex pathophysiological processes of uncontrolled DM results in DCM, a form of cardiomyopathy diagnosed in the absence of other causes for structural heart disease. Though optimal management of DM from early stages of the disease can reduce the risk of diabetic heart disease, it is often impractical in the real world due to many reasons. Therefore, it is imperative for every clinician involved in diabetes care to have a good understanding of the pathophysiology, clinical picture, diagnostic methods, and management of diabetes-related cardiac illness, to reduce morbidity and mortality among patients. This clinical review is to empower the global scientific fraternity with up-to-date knowledge on diabetic heart disease.