Exercise increases cutaneous nerve density in diabetic patients without neuropathy

Diabetic Neuropathy: A Guide to Pain Management

PURPOSE OF REVIEW

Diabetic neuropathy is a common complication of diabetes mellitus (DM) and can affect up to 50% of DM patients during their lifetime. Patients typically present with numbness, tingling, pain, and loss of sensation in the extremities. Since there is no treatment targeting the underlying mechanism of neuropathy, strategies focus on preventative care and pain management.

RECENT FINDINGS

Up to 69% of patients with diabetic neuropathy receive pharmacological treatment for neuropathic pain. The United States Food and Drug Administration (FDA) confirmed four drugs for painful diabetic neuropathy (PDN): pregabalin, duloxetine, tapentadol, and the 8% capsaicin patch. Nonpharmacological treatments such as spinal cord stimulation (SCS) and transcutaneous electrical nerve stimulation (TENS) both show promise in reducing pain in DM patients. Despite the high burden associated with PDN, effective management remains challenging. This update covers the background and management of diabetic neuropathy, including its epidemiology, pathogenesis, preventative care, and current therapeutic strategies.

Obesity-related neuropathy: the new epidemic

PURPOSE OF REVIEW

To examine the evidence evaluating the association between obesity and neuropathy as well as potential interventions.

RECENT FINDINGS

Although diabetes has long been associated with neuropathy, additional metabolic syndrome components, including obesity, are increasingly linked to neuropathy development, regardless of glycemic status. Preclinical rodent models as well as clinical studies are shedding light on the mechanisms of obesity-related neuropathy as well as challenges associated with slowing progression. Dietary and surgical weight loss and exercise interventions are promising, but more data is needed.

SUMMARY

High-fat-diet rodent models have shown that obesity-related neuropathy is a product of excess glucose and lipid accumulation leading to inflammation and cell death. Clinical studies consistently demonstrate obesity is independently associated with neuropathy; therefore, likely a causal risk factor. Dietary weight loss improves neuropathy symptoms but not examination scores. Bariatric surgery and exercise are promising interventions, but larger, more rigorous studies are needed. Further research is also needed to determine the utility of weight loss medications and ideal timing for obesity interventions to prevent neuropathy.

A Systematic Guideline by the ASPN Workgroup on the Evidence, Education, and Treatment Algorithm for Painful Diabetic Neuropathy: SWEET

Introduction

Painful diabetic neuropathy (PDN) is a leading cause of pain and disability globally with a lack of consensus on the appropriate treatment of those suffering from this condition. Recent advancements in both pharmacotherapy and interventional approaches have broadened the treatment options for PDN. There exists a need for a comprehensive guideline for the safe and effective treatment of patients suffering from PDN.

Objective

The SWEET Guideline was developed to provide clinicians with the most comprehensive guideline for the safe and appropriate treatment of patients suffering from PDN.

Methods

The American Society of Pain and Neuroscience (ASPN) identified an educational need for a comprehensive clinical guideline to provide evidence-based recommendations for PDN. A multidisciplinary group of international experts developed the SWEET guideline. The world literature in English was searched using Medline, EMBASE, Cochrane CENTRAL, BioMed Central, Web of Science, Google Scholar, PubMed, Current Contents Connect, Meeting Abstracts, and Scopus to identify and compile the evidence for diabetic neuropathy pain treatments (per section as listed in the manuscript) for the treatment of pain. Manuscripts from 2000-present were included in the search process.

Results

After a comprehensive review and analysis of the available evidence, the ASPN SWEET guideline was able to rate the literature and provide therapy grades for most available treatments for PDN utilizing the United States Preventive Services Task Force criteria.

Conclusion

The ASPN SWEET Guideline represents the most comprehensive review of the available treatments for PDN and their appropriate and safe utilization.

Prevalence and characteristics of diabetic symmetric sensorimotor polyneuropathy in Japanese patients with type 2 diabetes: The Japan Diabetes Complication and its Prevention Prospective study (JDCP study 10)

This study aimed to investigate the prevalence and characteristics of diabetic symmetric sensorimotor polyneuropathy (DSPN) in patients with type 2 diabetes registered in the Japan Diabetes Complication and its Prevention Prospective study. In the study, 6,338 patients with diabetes who had been treated by diabetes specialists were registered in 2007-2009. Of these, patients with type 2 diabetes who could be evaluated for DSPN were analyzed using the t-test, χ2 -test and logistic regression analyses. DSPN was diagnosed using the Simple Diagnostic Criteria for Diabetic Polyneuropathy proposed by the Diabetic Neuropathy Study Group in Japan. Of the total participants, 5,451 patients (mean age 61.4 years, duration of diabetes 10.8 years) were analyzed. Based on the criteria, 35.8% of patients were diagnosed with DSPN. The prevalence of sensory symptoms was 25.8%. The following factors increased the risk for DSPN: age (odds ratio [OR] 1.57, 95% confidence interval [CI] 1.42-1.73), duration of diabetes (OR 1.32, 95% CI 1.21-1.43), body mass index (OR 1.19, 95% CI 1.09-1.30), systolic blood pressure (OR 1.06, 95% CI 1.01-1.10), hemoglobin A1c (OR 1.15, 95% CI 1.09-1.22), biguanides (OR 1.22, 95% CI 1.06-1.39) and insulin therapy (OR 1.59, 95% CI 1.36-1.84). The following factors decreased the risk for DSPN: total cholesterol (OR 0.98, 95% CI 0.96-1.00) and exercise therapy (OR 0.85, 95% CI 0.73-0.98). The baseline survey clarified the prevalence and characteristics of DSPN in Japanese patients with type 2 diabetes. The survey also showed the risk factors of DSPN.

Spectrum of Diabetic Neuropathy: New Insights in Diagnosis and Treatment

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.

Prevalence and characteristics of diabetic symmetric sensorimotor polyneuropathy in Japanese patients with type 2 diabetes: the Japan Diabetes Complication and its Prevention Prospective study (JDCP study 10)

Aim/introduction

This study aims to investigate the prevalence and characteristics of diabetic symmetric sensorimotor polyneuropathy (DSPN) in patients with type 2 diabetes registered in the Japan Diabetes Complication and its Prevention Prospective (JDCP) study.

Materials and methods

In the study, 6338 patients with diabetes who had been treated by diabetes specialists were registered in 2007-2009. Of these, patients with type 2 diabetes who could be evaluated for DSPN were analyzed using t test, chi-square test, and logistic regression analyses. DSPN was diagnosed using the Simple Diagnostic Criteria for Diabetic Polyneuropathy proposed by the Diabetic Neuropathy Study Group in Japan.

Results

Of the total participants, 5451 patients (mean age 61.4 years old and duration of diabetes 10.8 years) were analyzed. Based on the criteria, 35.8% of patients were diagnosed with DSPN. The prevalence of sensory symptoms was 25.8%. The following factors increased risk for DSPN: age [odds ratio (OR) 1.57, 95% confidence intervals (CI) 1.42-1.73], duration of diabetes (OR 1.32, 95% CI 1.21-1.43), body mass index (OR 1.19, 95% CI 1.09-1.30), systolic blood pressure (OR 1.06, 95% CI 1.01-1.10), hemoglobin A1c (OR 1.15, 95% CI 1.09-1.22), biguanides (OR 1.22, 95% CI 1.06-1.39), and insulin therapy (OR 1.59, 95% CI 1.36-1.84). The following factors decreased risk for DSPN: total cholesterol (OR 0.98, 95% CI 0.96-1.00) and exercise therapy (OR 0.85, 95% CI 0.73-0.98).

Conclusions

The baseline survey clarified the prevalence and characteristics of DSPN in Japanese patients with type 2 diabetes. The survey also revealed the risk factors of DSPN.

Safety and Efficacy of Topiramate in Individuals With Cryptogenic Sensory Peripheral Neuropathy With Metabolic Syndrome: The TopCSPN Randomized Clinical Trial

Importance

Cryptogenic sensory peripheral neuropathy (CSPN) is highly prevalent and often disabling due to neuropathic pain. Metabolic syndrome and its components increase neuropathy risk. Diet and exercise have shown promise but are limited by poor adherence.

Objective

To determine whether topiramate can slow decline in intraepidermal nerve fiber density (IENFD) and/or neuropathy-specific quality of life measured using the Norfolk Quality of Life-Diabetic Neuropathy (NQOL-DN) scale.

Design, Setting, and Participants

Topiramate as a Disease-Modifying Therapy for CSPN (TopCSPN) was a double-blind, placebo-controlled, randomized clinical trial conducted between February 2018 and October 2021. TopCSPN was performed at 20 sites in the National Institutes of Health-funded Network for Excellence in Neurosciences Clinical Trials (NeuroNEXT). Individuals with CSPN and metabolic syndrome aged 18 to 80 years were screened and randomly assigned by body mass index (<30 vs ≥30), which is calculated as weight in kilograms divided by height in meters squared. Patients were excluded if they had poorly controlled diabetes, prior topiramate treatment, recurrent nephrolithiasis, type 1 diabetes, use of insulin within 3 months before screening, history of foot ulceration, planned bariatric surgery, history of alcohol or drug overuse in the 2 years before screening, family history of a hereditary neuropathy, or an alternative neuropathy cause.

Interventions

Participants received topiramate or matched placebo titrated to a maximum-tolerated dose of 100 mg per day.

Main Outcomes and Measures

IENFD and NQOL-DN score were co-primary outcome measures. A positive study was defined as efficacy in both or efficacy in one and noninferiority in the other.

Results

A total of 211 individuals were screened, and 132 were randomly assigned to treatment groups: 66 in the topiramate group and 66 in the placebo group. Age and sex were similar between groups (topiramate: mean [SD] age, 61 (10) years; 38 male [58%]; placebo: mean [SD] age, 62 (11) years; 44 male [67%]). The difference in change in IENFD and NQOL-DN score was noninferior but not superior in the intention-to-treat (ITT) analysis (IENFD, 0.21 fibers/mm per year; 95% CI, -0.43 to ∞ fibers/mm per year and NQOL-DN score, -1.52 points per year; 95% CI, -∞ to 1.19 points per year). A per-protocol analysis excluding noncompliant participants based on serum topiramate levels and those with major protocol deviations demonstrated superiority in NQOL-DN score (-3.69 points per year; 95% CI, -∞ to -0.73 points per year). Patients treated with topiramate had a mean (SD) annual change in IENFD of 0.56 fibers/mm per year relative to placebo (95% CI, -0.21 to ∞ fibers/mm per year). Although IENFD was stable in the topiramate group compared with a decline consistent with expected natural history, this difference did not demonstrate superiority.

Conclusion and Relevance

Topiramate did not slow IENFD decline or affect NQOL-DN score in the primary ITT analysis. Some participants were intolerant of topiramate. NQOL-DN score was superior among those compliant based on serum levels and without major protocol deviations.

Trial Registration

ClinicalTrials.gov Identifier: NCT02878798.

Pharmacological and Nonpharmacological Treatments for Painful Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) is one of the most prevalent chronic complications of diabetes. The lifetime prevalence of DPN is thought to be >50%, and 15%-25% of patients with diabetes experience neuropathic pain, referred to as "painful DPN." Appropriate treatment of painful DPN is important because this pain contributes to a poor quality of life by causing sleep disturbance, anxiety, and depression. The basic principle for the management of painful DPN is to control hyperglycemia and other modifiable risk factors, but these may be insufficient for preventing or improving DPN. Because there is no promising diseasemodifying medication for DPN, the pain itself needs to be managed when treating painful DPN. Drugs for neuropathic pain, such as gabapentinoids, serotonin-norepinephrine reuptake inhibitors, tricyclic antidepressants, alpha-lipoic acid, sodium channel blockers, and topical capsaicin, are used for the management of painful DPN. The U.S. Food and Drug Administration (FDA) has approved pregabalin, duloxetine, tapentadol, and the 8% capsaicin patch as drugs for the treatment of painful DPN. Recently, spinal cord stimulation using electrical stimulation is approved by the FDA for the treatment for painful DPN. This review describes the currently available pharmacological and nonpharmacological treatments for painful DPN.

THE PREVALENCE OF POLYNEUROPATHY IN THE PRE-DIABETES PERIOD

Objective

This study aims to determine the prevalence of neuropathy in the prediabetic period.

Design Subjects and Method

Informed consent was attained from the patients who volunteered to participate in the study after ethics committee approval was obtained. Patients under the age of 18, having vitamin B12 or folic acid deficiency, history of collagen tissue-rheumatological disease, chronic kidney failure, cirrhosis, ethylism, thyroid disease, autoimmune disease, malignancy, tuberculosis, type 1 or 2 diabetes mellitus and pregnant women were excluded from the study. Patients diagnosed with prediabetes were evaluated by the DN4 neuropathy complaint questionnaire. Neuropathy was diagnosed in patients having a score of four or more. For the statistical analyses Student t-test, Pearson chi-square test, and Fisher's exact test were performed using the NCSS program.

Results

A total of 224 volunteers, 167 women and 57 men, were included in the study. The mean age of the participants was 51 and the mean level of hemoglobin A1C was 5.9. Neuropathy was detected in 45% of the cases. Especially in women, there was a significant increase in the frequency of neuropathy compared to men. The most common complaints found in our study were burning sensation and numbness in the extremities.

Conclusions

Similar to diabetic patients, prediabetic patients also have a high rate of neuropathy. For the early diagnosis of neuropathy and to be treated promptly, screening tests such as DN4 should be performed for all prediabetic patients. According to the test results, advanced examinations such as EMG or biopsy should be performed earlier.

An updated patent review of GPR40/ FFAR1 modulators (2020 - present)

INTRODUCTION

Free fatty acid receptor 1 (FFAR1) is a potential therapeutic target for type 2 diabetes mellitus (T2DM) because it could clinically stimulate insulin release in a glucose-dependent manner without inducing hypoglycemia. In both the pharmaceutical industry and academic community, FFAR1 agonists have attracted considerable attention.

AREAS COVERED

The review presents a patent overview of FFAR1 modulators in 2020-2023, along with chemical structures, the biological activities and therapeutic applications of the representative compounds. Our patent survey used the major electronic databases, namely SciFinder, and Web of Science and Innojoy.

EXPERT OPINION

Although FFAR1 agonists exhibit outstanding advantages, they are also associated with significant challenges. At present, reducing the molecular weight and overall lipophilicity and developing tissue-specific FFAR1 agonists may be the strategies for alleviating hepatotoxicity.

Six-month periodic fasting does not affect somatosensory nerve function in type 2 diabetes patients

Background and aim

Current strategies for preventing diabetic sensorimotor polyneuropathy (DSPN) are limited mainly to glucose control but rapid decrease of glycemia can lead to acute onset or worsening of DSPN. The aim of this study was to examine the effects of periodic fasting on somatosensory nerve function in patients with type 2 diabetes (T2D).

Study design and methods

Somatosensory nerve function was assessed in thirty-one patients with T2D (HbA1c 7.8 ± 1.3% [61.4 ± 14.3 mmol/mol]) before and after a six-month fasting-mimicking diet (FMD; n=14) or a control Mediterranean diet (M-diet; n=17). Neuropathy disability score (NDS), neuropathy symptoms score (NSS), nerve conduction velocity and quantitative sensory testing (QST) were analyzed. 6 participants of the M-Diet group and 7 of the FMD group underwent diffusion-weighted high-resolution magnetic resonance neurography (MRN) of the right leg before and after the diet intervention.

Results

Clinical neuropathy scores did not differ between study groups at baseline (64% in the M-Diet group and 47% in the FMD group had DSPN) and no change was found after intervention. The differences in sensory NCV and sensory nerve action potential (SNAP) of sural nerve were comparable between study groups. Motor NCV of tibial nerve decreased by 12% in the M-Diet group (P=0.04), but did not change in the FMD group (P=0.39). Compound motor action potential (CMAP) of tibial nerve did not change in M-Diet group (P=0.8) and increased in the FMD group by 18% (P=0.02). Motor NCV and CMAP of peroneal nerve remained unchanged in both groups. In QST M-diet-group showed a decrease by 45% in heat pain threshold (P=0.02), FMD group showed no change (P=0.50). Changes in thermal detection, mechanical detection and mechanical pain did not differ between groups. MRN analysis showed stable fascicular nerve lesions irrespective of the degree of structural pathology. Fractional anisotropy and T2-time did not change in both study groups, while a correlation with the clinical degree of DSPN could be confirmed for both.

Conclusions

Our study shows that six-month periodic fasting was safe in preserving nerve function and had no detrimental effects on somatosensory nerve function in T2D patients.

Clinical trial registration

https://drks.de/search/en/trial/DRKS00014287, identifier DRKS00014287.

Emerging Nonpharmacologic Interventions to Treat Diabetic Peripheral Neuropathy

Significance: Diabetic peripheral neuropathy (DPN), a complication of metabolic syndrome, type I and type II diabetes, leads to sensory changes that include slow nerve conduction, nerve degeneration, loss of sensation, pain, and gate disturbances. These complications remain largely untreatable, although tight glycemic control can prevent neuropathy progression. Nonpharmacologic approaches remain the most impactful to date, but additional advances in treatment approaches are needed. Recent Advances: This review highlights several emerging interventions, including a focus on dietary interventions and physical activity, that continue to show promise for treating DPN. We provide an overview of our current understanding of how exercise can improve aspects of DPN. We also highlight new studies in which a ketogenic diet has been used as an intervention to prevent and reverse DPN. Critical Issues: Both exercise and consuming a ketogenic diet induce systemic and cellular changes that collectively improve complications associated with DPN. Both interventions may involve similar signaling pathways and benefits but also impact DPN through unique mechanisms. Future Directions: These lifestyle interventions are critically important as personalized medicine approaches will likely be needed to identify specific subsets of neuropathy symptoms and deficits in patients, and determine the most impactful treatment. Overall, these two interventions have the potential to provide meaningful relief for patients with DPN and provide new avenues to identify new therapeutic targets.

Recent updates in the treatment of diabetic polyneuropathy

Distal symmetric diabetic peripheral polyneuropathy (DPN) is the most common form of neuropathy in the world, affecting 30 to 50% of diabetic individuals and resulting in significant morbidity and socioeconomic costs. This review summarizes updates in the diagnosis and management of DPN. Recently updated clinical criteria facilitate bedside diagnosis, and a number of new technologies are being explored for diagnostic confirmation in specific settings and for use as surrogate measures in clinical trials. Evolving literature indicates that distinct but overlapping mechanisms underlie neuropathy in type 1 versus type 2 diabetes, and there is a growing focus on the role of metabolic factors in the development and progression of DPN. Exercise-based lifestyle interventions have shown therapeutic promise. A variety of potential disease-modifying and symptomatic therapies are in development. Innovations in clinical trial design include the incorporation of detailed pain phenotyping and biomarkers for central sensitization.

American Association of Clinical Endocrinology Clinical Practice Guideline: Developing a Diabetes Mellitus Comprehensive Care Plan-2022 Update

OBJECTIVE

The objective of this clinical practice guideline is to provide updated and new evidence-based recommendations for the comprehensive care of persons with diabetes mellitus to clinicians, diabetes-care teams, other health care professionals and stakeholders, and individuals with diabetes and their caregivers.

METHODS

The American Association of Clinical Endocrinology selected a task force of medical experts and staff who updated and assessed clinical questions and recommendations from the prior 2015 version of this guideline and conducted literature searches for relevant scientific papers published from January 1, 2015, through May 15, 2022. Selected studies from results of literature searches composed the evidence base to update 2015 recommendations as well as to develop new recommendations based on review of clinical evidence, current practice, expertise, and consensus, according to established American Association of Clinical Endocrinology protocol for guideline development.

RESULTS

This guideline includes 170 updated and new evidence-based clinical practice recommendations for the comprehensive care of persons with diabetes. Recommendations are divided into four sections: (1) screening, diagnosis, glycemic targets, and glycemic monitoring; (2) comorbidities and complications, including obesity and management with lifestyle, nutrition, and bariatric surgery, hypertension, dyslipidemia, retinopathy, neuropathy, diabetic kidney disease, and cardiovascular disease; (3) management of prediabetes, type 2 diabetes with antihyperglycemic pharmacotherapy and glycemic targets, type 1 diabetes with insulin therapy, hypoglycemia, hospitalized persons, and women with diabetes in pregnancy; (4) education and new topics regarding diabetes and infertility, nutritional supplements, secondary diabetes, social determinants of health, and virtual care, as well as updated recommendations on cancer risk, nonpharmacologic components of pediatric care plans, depression, education and team approach, occupational risk, role of sleep medicine, and vaccinations in persons with diabetes.

CONCLUSIONS

This updated clinical practice guideline provides evidence-based recommendations to assist with person-centered, team-based clinical decision-making to improve the care of persons with diabetes mellitus.

Obesity-Associated Neuropathy: Recent Preclinical Studies and Proposed Mechanisms

Significance: The prevalence of metabolic syndrome (MetS) and associated obesity has increased in recent years, affecting millions worldwide. One of the most common complications of obesity is damage to the peripheral nerve system, referred to as neuropathy. The lack of disease-modifying therapy for this complication is largely due to a poor understanding of the complex neurobiology underlying neuropathy. Recent preclinical studies suggest that in addition to glucotoxic events, other mechanisms, including lipid signaling, microbiome, or inflammation, may be viable targets to prevent nerve damage and neuropathic pain in obesity. Recent Advances: Clinical and preclinical studies using diet-induced obesity rodent models have identified novel interventions that improve neuropathy. Notably, mechanistic studies suggest that lipid, calcium signaling, and inflammation are converging pathways. Critical Issues: In this review, we focus on interventions and their mechanisms that are shown to ameliorate neuropathy in MetS obese models, including: (i) inhibition of a sensory neuron population, (ii), modification of dietary components, (iii) activation of nuclear and mitochondrial lipid pathways, (iv) exercise, and (v) modulation of gut microbiome composition and their metabolites. Future Directions: These past years, novel research increased our knowledge about neuropathy in obesity and discovered the involvement of nonglucose signaling. More studies are necessary to uncover the interplay between complex metabolic pathways in the peripheral nerve system of obese individuals. Further mechanistic studies in preclinical models and humans are crucial to create single- or multitarget interventions for this complex disease implying complex metabolic phenotyping. Antioxid. Redox Signal. 37, 597-612.

Current and Emerging Pharmacotherapeutic Interventions for the Treatment of Peripheral Nerve Disorders

Peripheral nerve disorders are caused by a range of different aetiologies. The range of causes include metabolic conditions such as diabetes, obesity and chronic kidney disease. Diabetic neuropathy may be associated with severe weakness and the loss of sensation, leading to gangrene and amputation in advanced cases. Recent studies have indicated a high prevalence of neuropathy in patients with chronic kidney disease, also known as uraemic neuropathy. Immune-mediated neuropathies including Guillain-Barré syndrome and chronic inflammatory demyelinating polyradiculoneuropathy may cause significant physical disability. As survival rates continue to improve in cancer, the prevalence of treatment complications, such as chemotherapy-induced peripheral neuropathy, has also increased in treated patients and survivors. Notably, peripheral neuropathy associated with these conditions may be chronic and long-lasting, drastically affecting the quality of life of affected individuals, and leading to a large socioeconomic burden. This review article explores some of the major emerging clinical and experimental therapeutic agents that have been investigated for the treatment of peripheral neuropathy due to metabolic, toxic and immune aetiologies.

Effects of progressive resistance training in individuals with type 2 diabetic polyneuropathy: a randomised assessor-blinded controlled trial

AIMS/HYPOTHESIS

The aim of this study was to evaluate the effects of progressive resistance training (PRT) on muscle strength, intraepidermal nerve fibre density (IENFD) and motor function in individuals with type 2 diabetic polyneuropathy (DPN) and to compare potential adaptations to those of individuals with type 2 diabetes without DPN and healthy controls.

METHODS

This was an assessor-blinded trial conducted at the Neurology department, Aarhus University Hospital. Adults with type 2 diabetes, with and without DPN and healthy control participants were randomised to either supervised PRT or non-PRT for 12 weeks. Allocation was concealed by a central office unrelated to the study. The co-primary outcomes were muscle strength in terms of the peak torque of the knee and ankle extensors and flexors, and IENFD. Secondary outcome measures included the 6 min walk test (6MWT), five-time sit-to-stand test (FTSST) and postural stability index obtained by static posturography.

RESULTS

A total of 109 individuals were enrolled in three groups (type 2 diabetes with DPN [n = 42], type 2 diabetes without DPN [n = 32] and healthy control [n = 35]). PRT resulted in muscle strength gains of the knee extensors and flexors in all three groups using comparative analysis (DPN group, PRT 10.3 ± 9.6 Nm vs non-PRT -0.4 ± 8.2 Nm; non-DPN group, PRT 7.5 ± 5.8 Nm vs non-PRT 0.6 ± 8.8 Nm; healthy control group, PRT 6.3 ± 9.0 Nm vs non-PRT -0.4 ± 8.4 Nm; p<0.05, respectively). Following PRT the DPN group improved the 6MWT (PRT 34.6 ± 40.9 m vs non-PRT 2.7 ± 19.6 m; p=0.001) and the FTSST (PRT -1.5 ± 2.2 s vs non-PRT 1.5 ± 4.6 s; p=0.02). There was no change in IENFD following PRT in any of the groups.

CONCLUSIONS/INTERPRETATION

PRT improved muscle strength of the knee extensors and flexors and motor function in individuals with type 2 diabetic polyneuropathy at levels comparable with those seen in individuals with diabetes without DPN and healthy control individuals, while no effects were observed in IENFD.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03252132 FUNDING: Research reported in this paper is part of the International Diabetic Neuropathy Consortium (IDNC) research programme, supported by a Novo Nordisk Foundation Challenge Program grant (grant no. NNF14OC0011633) and Aarhus University.

Prevention of Peripheral Distal Polyneuropathy in Patients with Diabetes: A Systematic Review

Background: Diabetic peripheral neuropathy (DPN) is the most frequent chronic complication and is that which generates the highest disability and mortality in diabetes mellitus (DM). As it is currently the only microvascular complication of DM without a specific treatment, prevention is essential. The aim of this study was to determine the most effective preventive strategy to avoid or delay the appearance and/or development of DPN in patients with DM. Methods: A systematic search was carried out in the main health science databases (PubMed, Scopus, CINAHL, PEDro and The Cochrane Library) from 1 January 2010 to 31 August 2020. The study selection was conducted by two independent reviewers and data extraction was performed by the author. The eligibility criteria included randomized clinical trials (RCTs) and cohort studies from RCTs. Results: Eleven studies were selected that included 23,595 participants with DM. The interventions evaluated were intensive or standard glycemic control, the use of drugs to achieve glycemic control, and the promotion of a healthy lifestyle and exercise. Intensive glucose control achieved a significant reduction in the development of DPN in TIDM patients, and lifestyle modifications and exercise achieved it moderately in TIIDM patients. Conclusions: The main preventive strategy for DPN is intensive glycemic control with a target HbA1c < 6% in patients with TIDM and standard control of 7.0−7.9 in patients with TIIDM, incorporating lifestyle modifications.

The association between physical activity time and neuropathy in longstanding type 1 diabetes: A cross-sectional analysis of the Canadian study of longevity in type 1 diabetes

AIM

Physical activity (PA) is recommended to improve glycemic control in T1D; however, the effect of PA on distal symmetric polyneuropathy (DSPN) and cardiac autonomic function in longstanding T1D is unknown.

METHODS

Data from 75 participants were collected as part of the Canadian Study of Longevity in T1D. Participants completed a physical exam, medical history, extensive complications phenotyping and reported their daily PA from the preceding 12-months. Pearson and Spearman correlations were used to assess PA time and complications variables. Linear regression was used to test associations between PA time, neurological and electrophysiological measures. Univariable regression was used to indicate the change in the given independent variables associated with a 30-min increase in PA per week.

RESULTS

Participants were 66 ± 8 years old with diabetes duration of 54 [52,58] years, HbA_1c was 7.3 ± 0.8, 65(89%) had DSPN. Weekly PA time was 156 ± 132 min, and 35(47%) reported ≧150 min/week. Participants with DSPN reported lower PA time compared to individuals without DSPN (141 ± 124 min/week vs. 258 ± 129 min/week; p = 0.015). PA time was associated with better cooling detection threshold (r = 0.24; p = 0.043), peroneal and sural amplitude (r = 0.36; p = 0.0017, r_s = 0.26; p = 0.024) and conduction velocity (r_s = 0.28; p = 0.015, r = 0.23; p = 0.050). Linear regression adjusting for age and HbA1c, showed that for each 30-min of PA there was a 0.09mv higher peroneal amplitude (p = 0.032) and 0.048 ms lower peroneal F-wave latency (p = 0.022).

CONCLUSION

In longstanding T1D, PA time is associated with superior large nerve fibre function in the lower limbs and some better measures of small nerve fibre function.

Mechanisms, Mediators, and Moderators of the Effects of Exercise on Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is an adverse effect of neurotoxic antineoplastic agents commonly used to treat cancer. Patients with CIPN experience debilitating signs and symptoms, such as combinations of tingling, numbness, pain, and cramping in the hands and feet that inhibit their daily function. Among the limited prevention and treatment options for CIPN, exercise has emerged as a promising new intervention that has been investigated in approximately two dozen clinical trials to date. As additional studies test and suggest the efficacy of exercise in treating CIPN, it is becoming more critical to develop mechanistic understanding of the effects of exercise in order to tailor it to best treat CIPN symptoms and identify who will benefit most. To address the current lack of clarity around the effect of exercise on CIPN, we reviewed the key potential mechanisms (e.g., neurophysiological and psychosocial factors), mediators (e.g., anti-inflammatory cytokines, self-efficacy, and social support), and moderators (e.g., age, sex, body mass index, physical fitness, exercise dose, exercise adherence, and timing of exercise) that may illuminate the relationship between exercise and CIPN improvement. Our review is based on the studies that tested the use of exercise for patients with CIPN, patients with other types of neuropathies, and healthy adults. The discussion presented herein may be used to (1) guide oncologists in predicting which symptoms are best targeted by specific exercise programs, (2) enable clinicians to tailor exercise prescriptions to patients based on specific characteristics, and (3) inform future research and biomarkers on the relationship between exercise and CIPN.

BOND study: a randomised double-blind, placebo-controlled trial over 12 months to assess the effects of benfotiamine on morphometric, neurophysiological and clinical measures in patients with type 2 diabetes with symptomatic polyneuropathy

INTRODUCTION

Diabetic sensorimotor polyneuropathy (DSPN) affects approximately 30% of people with diabetes, while around half of cases are symptomatic. Currently, there are only few pathogenetically oriented pharmacotherapies for DSPN, one of which is benfotiamine, a prodrug of thiamine with a high bioavailability and favourable safety profile. While benfotiamine has shown positive effects in preclinical and short-term clinical studies, no long-term clinical trials are available to demonstrate disease-modifying effects on DSPN using a comprehensive set of disease-related endpoints.

METHODS AND ANALYSIS

The benfotiamine on morphometric, neurophysiological and clinical measures in patients with type 2 diabetes trial is a randomised double-blind, placebo-controlled parallel group monocentric phase II clinical trial to assess the effects of treatment with benfotiamine compared with placebo in participants with type 2 diabetes and mild to moderate symptomatic DSPN. Sixty participants will be 1:1 randomised to treatment with benfotiamine 300 mg or placebo two times a day over 12 months. The primary endpoint will be the change in corneal nerve fibre length assessed by corneal confocal microscopy (CCM) after 12 months of benfotiamine treatment compared with placebo. Secondary endpoints will include other CCM measures, skin biopsy and function indices, variables from somatic and autonomic nerve function tests, clinical examination and questionnaires, general health, health-related quality of life, cost, safety and blood tests.

ETHICS AND DISSEMINATION

The trial was approved by the competent authority and the local independent ethics committee. Trial results will be published in peer-reviewed journals, conference abstracts, and via online and print media.

TRIAL REGISTRATION NUMBER

DRKS00014832.

Exercise as Treatment for Neuropathy in the Setting of Diabetes and Prediabetic Metabolic Syndrome: A Review of Animal Models and Human Trials

BACKGROUND

Peripheral neuropathy is among the most common complications of diabetes, but a phenotypically identical distal sensory predominant, painful axonopathy afflicts patients with prediabetic metabolic syndrome, exemplifying a spectrum of risk and continuity of pathogenesis. No pharmacological treatment convincingly improves neuropathy in the setting of metabolic syndrome, but evolving data suggest that exercise may be a promising alternative.

OBJECTIVE

The aim of the study was to review in depth the current literature regarding exercise treatment of metabolic syndrome neuropathy in humans and animal models, highlight the diverse mechanisms by which exercise exerts beneficial effects, and examine adherence limitations, safety aspects, modes and dose of exercise.

RESULTS

Rodent models that recapitulate the organismal milieu of prediabetic metabolic syndrome and the phenotype of its neuropathy provide a strong platform to dissect exercise effects on neuropathy pathogenesis. In these models, exercise reverses hyperglycemia and consequent oxidative and nitrosative stress, improves microvascular vasoreactivity, enhances axonal transport, ameliorates the lipotoxicity and inflammatory effects of hyperlipidemia and obesity, supports neuronal survival and regeneration following injury, and enhances mitochondrial bioenergetics at the distal axon. Prospective human studies are limited in scale but suggest exercise to improve cutaneous nerve regenerative capacity, neuropathic pain, and task-specific functional performance measures of gait and balance. Like other heath behavioral interventions, the benefits of exercise are limited by patient adherence.

CONCLUSION

Exercise is an integrative therapy that potently reduces cellular inflammatory state and improves distal axonal oxidative metabolism to ameliorate features of neuropathy in metabolic syndrome. The intensity of exercise need not improve cardinal features of metabolic syndrome, including weight, glucose control, to exert beneficial effects.

Small-Fiber-Neuropathien

Die Small-Fiber-Neuropathie (SFN) ist eine Erkrankung des peripheren Nervensystems aufgrund einer isolierten oder vorwiegenden Schädigung dünn myelinisierter Aδ-Fasern und/oder unmyelinisierter C‑Fasern. Für die sichere Diagnose einer SFN ist neben der klinischen Symptomatik mit Schmerzen und Sensibilitätsstörungen, typischerweise mit distal betonter Ausbreitung, der apparative Nachweis einer Rarefizierung oder einer Funktionsstörung der dünn myelinisierten Aδ-Fasern und/oder der unmyelinisierten C‑Fasern gefordert. Im vorliegenden Beitrag wird eine Übersicht über die diagnostischen Verfahren zum Nachweis einer SFN sowie über mögliche Ursachen und Behandlungsoptionen gegeben.

Recent updates in the treatment of diabetic polyneuropathy

Distal symmetric diabetic peripheral polyneuropathy (DPN) is the most common form of neuropathy in the world, affecting 30 to 50% of diabetic individuals and resulting in significant morbidity and socioeconomic costs. This review summarizes updates in the diagnosis and management of DPN. Recently updated clinical criteria facilitate bedside diagnosis, and a number of new technologies are being explored for diagnostic confirmation in specific settings and for use as surrogate measures in clinical trials. Evolving literature indicates that distinct but overlapping mechanisms underlie neuropathy in type 1 versus type 2 diabetes, and there is a growing focus on the role of metabolic factors in the development and progression of DPN. Exercise-based lifestyle interventions have shown therapeutic promise. A variety of potential disease-modifying and symptomatic therapies are in development. Innovations in clinical trial design include the incorporation of detailed pain phenotyping and biomarkers for central sensitization.

Small Fiber Neuropathy Incidence, Prevalence, Longitudinal Impairments, and Disability

BACKGROUND AND OBJECTIVES

There are limited population-based data on small fiber neuropathy (SFN). We wished to determine SFN incidence, prevalence, comorbid conditions, longitudinal impairments, and disabilities.

METHODS

Test-confirmed patients with SFN in Olmsted, Minnesota, and adjacent counties were compared 3:1 to matched controls (January 1, 1998-December 31, 2017).

RESULTS

Ninety-four patients with SFN were identified, with an incidence of 1.3/100,000/y that increased over the study period and a prevalence of 13.3 per 100,000. Average follow-up was 6.1 years (0.7-43 years), and mean onset age was 54 years (range 14-83 years). Female sex (67%), obesity (body mass index mean 30.4 vs 28.5 kg/m²), insomnia (86% vs 54%), analgesic-opioid prescriptions (72% vs 46%), hypertriglyceridemia (180 mg/dL mean vs 147 mg/dL), and diabetes (51% vs 22%, p < 0.001) were more common (odds ratio 3.8-9.0, all p < 0.03). Patients with SFN did not self-identify as disabled with a median modified Rankin Scale score of 1.0 (range 0-6) vs 0.0 (0-6) for controls (p = 0.04). Higher Charlson comorbid conditions (median 6, range 3-9) occurred vs controls (median 3, range 1-9, p < 0.001). Myocardial infarctions occurred in 46% vs 27% of controls (p < 0.0001). Classifications included idiopathic (70%); diabetes (15%); Sjögren disease (2%); AL-amyloid (1%); transthyretin-amyloid (1%); Fabry disease (1%); lupus (1%); postviral (1%); Lewy body (1%), and multifactorial (5%). Foot ulcers occurred in 17, with 71% having diabetes. Large fiber neuropathy developed in 36%, on average 5.3 years (range 0.2-14.3 years) from SFN onset. Median onset Composite Autonomic Severity Score (CASS) was 3 (change per year 0.08, range 0-2.0). Median Neuropathy Impairment Scale (NIS) score was 2 at onset (range 0-8, change per year 1.0, range -7.9 to +23.3). NIS score and CASS change >1 point per year occurred in only AL-amyloid, hereditary transthyretin-amyloid, Fabry, uncontrolled diabetes, and Lewy body. Death after symptom onset was higher in patients with SFN (19%) vs controls (12%, p < 0.001), 50% secondary to diabetes complications.

DISCUSSION

Isolated SFN is uncommon but increasing in incidence. Most patients do not develop major neurologic impairments and disability but have multiple comorbid conditions, including cardiovascular ischemic events, and increased mortality from SFN onsets. Development of large fiber involvements and diabetes are common over time. Targeted testing facilitates interventional therapies for diabetes but also rheumatologic and rare genetic forms.

Advances About Immunoinflammatory Pathogenesis and Treatment in Diabetic Peripheral Neuropathy

Most diabetic patients develop diabetic peripheral neuropathy (DPN). DPN is related to the increase of inflammatory cells in peripheral nerves, abnormal cytokine expression, oxidative stress, ischemia ,and pro-inflammatory changes in bone marrow. We summarized the progress of immune-inflammatory mechanism and treatment of DPN in recent years. Immune inflammatory mechanisms include TNF-α, HSPs, PARP, other inflammatory factors, and the effect of immune cells on DPN. Treatment includes tricyclic antidepressants and other drug therapy, immune and molecular therapy, and non-drug therapy such as exercise therapy, electrotherapy, acupuncture, and moxibustion. The pathogenesis of DPN is complex. In addition to strictly controlling blood glucose, its treatment should also start from other ways, explore more effective and specific treatment schemes for various causes of DPN, and find new targets for treatment will be the direction of developing DPN therapeutic drugs in the future.

Resistance training improves nerve conduction and arterial stiffness in older adults with diabetic distal symmetrical polyneuropathy: A randomized controlled trial

Diabetes is the main cause of peripheral neuropathy where older patients are at increased risk of diabetic distal symmetrical polyneuropathy (DSPN) due to age-related nerve degeneration and vascular changes. The aim of the study was to investigate the effect of resistance training on nerve conduction, measures of neuropathy and arterial stiffness in older patients with DSPN. In a randomized controlled trial, thirty-four older adults with type-2 diabetes and peripheral neuropathy were enrolled and randomly assigned to experimental and control groups. The experimental group carried out circuit resistance training (1-3 rounds, 11 exercises, 10-15 reps, 50%-60% of 1RM, 3 times per week) for 12 weeks. Measurements were performed at baseline and 48 h after the intervention. Measures of DSPN including Michigan neuropathy screening instrument (MNSI), Michigan diabetic neuropathy score (MDNS), motor nerve action potential amplitude (APA), sensory and motor nerve conduction velocity (NCV) improved following intervention (p < 0.001, p = 0.001, p = 0.034, p = 0.001, and p = 0.001, respectively). Sensory APA did not change after the intervention (p = 0.139). Cardio-ankle vascular index (CAVI) and ankle-brachial index (ABI) improved in the experimental group compared with the control group (p = 0.014 and p = 0.033, respectively). In addition, HbA1C decreased following the 12-week resistance training program (p = 0.002). Older adults with DSPN respond positively to resistance training by improved neuropathy symptoms, nerve conduction, arterial stiffness and glucose regulation. Resistance training offers a positive intervention that can abate the progression of DSPN in older adults.

Impaired dermal microvascular reactivity and implications for diabetic wound formation and healing: an evidence review

Diabetic foot ulcers (DFUs) are among the most consequential and costly complications faced by patients with diabetes and the global healthcare system. Acknowledged risk factors for DFUs include diabetic peripheral neuropathy (DPN), peripheral arterial disease (PAD), microtrauma and foot deformities. Research on additional risk factors for DFUs has recently focused on dysregulated, autonomic vasomotor control in the skin of patients with DPN. In particular, impaired dermal microvascular reactivity (IDMR) with its attendant reduction in nutritive capillary blood flow has been identified as an emerging risk factor. This especially relates to refractory wounds noted in patients without overt PAD signs. In this paper, evidence will be reviewed supporting the evolving understanding of IDMR and its impact on DFU formation and healing. Advances in diagnostic instrumentation driving this research along with the most promising potential therapies aimed at improving microvascular function in the diabetic foot will be discussed in brief.

Exercise and Nutraceuticals: Eminent approach for Diabetic Neuropathy

Diabetic neuropathy is an incapacitating chronic pathological condition that encompasses a large group of diseases and manifestations of nerve damage. It affects approximately 50% of patients with diabetes mellitus. Autonomic, sensory, and motor neurons are affected. Disabilities are severe, along with poor recovery and diverse pathophysiology. Physical exercise and herbal-based therapies have the potential to decrease the disabilities associated with diabetic neuropathy. Aerobic exercises like walking, weight lifting, the use of nutraceuticals and herbal extracts are found to be effective. Literature from the public domain was studied emphasizing various beneficial effects of different exercises, use of herbal and nutraceuticals for their therapeutic action in diabetic neuropathy. Routine exercises and administration of herbal and nutraceuticals, either the extract of plant material containing the active phytoconstituent or isolated phytoconstituent at safe concentration, have been shown to have promising positive action in the treatment of diabetic neuropathy. Exercise has shown promising effects on vascular and neuronal health and has proven to be well effective in the treatment as well as prevention of diabetic neuropathy by various novel mechanisms, including herbal and nutraceuticals therapy is also beneficial for the condition. They primarily show the anti-oxidant effect, secretagogue, anti-inflammatory, analgesic, and neuroprotective action. Severe adverse events are rare with these therapies. The current review investigates the benefits of exercise and nutraceutical therapies in the treatment of diabetic neuropathy.

Phase 2a randomized controlled study investigating the safety and efficacy of PDA-002 in diabetic peripheral neuropathy

Neuropathy is a major cause of morbidity and mortality in individuals with diabetes, with no effective therapy to alter the inevitable progression of nerve damage. We hypothesized that mesenchymal stroma cell-like populations, that are characterized as immune modulators also have the potential of inducing angiogenesis and neurite outgrowth, might be useful in treating diabetic peripheral neuropathy (DPN). The aims of this study were to investigate the efficacy and safety of mesenchymal stem cell-like product (PDA-002) in treating DPN. A phase-2 randomized placebo-controlled trial was conducted in 26 patients with DPN. Treatment consisted of three rounds of intramuscular injections in one lower limb using one of the three randomized treatment arms PDA-002 (low-dose 3 × 10⁶ cells), PDA-002 (high-dose 30 × 10⁶ cells), or placebo. Three treatments per patient occurred on days 1, 29, and 57. Study endpoints included efficacy and safety of PDA-002 in treating DPN in both lower extremities following unilateral local injection. Outcome measures included intra-epidermal nerve fiber density (IENFD) up to 1 year from the day of treatment with 6-month as the primary outcome measurement. In this phase 2 study of DPN, PDA-002 was well tolerated in both doses. No significant changes were noted in IENFD in both the treated and untreated leg in the NIS-LL, NTSS-6, or UENS. Mesenchymal stem cells represent a novel mechanism for treating diabetic neuropathy and are well tolerated. Preliminary results highlight the need of further investigation of PDA-001 as a disease modifying agent for treatment of DPN.

Diabetes and Peripheral Nerve Disease

It is increasingly recognized that diabetic neuropathy is associated with early diabetes, prediabetes, and the metabolic syndrome. Early detection and diagnosis are important to slow progression and prevent complications. Although strict glucose control is an effective treatment in type 1 diabetes, it is less effective in type 2 diabetes. There is a growing body of literature that lifestyle interventions may be able to prevent or slow progression of neuropathy in type 2 diabetes. In addition to the typical distal symmetric polyneuropathy, there are many types of "atypical" diabetic neuropathies that are important to recognize.

Lost in Translation? Measuring Diabetic Neuropathy in Humans and Animals

The worldwide diabetes epidemic is estimated to currently afflict almost 500 million persons. Long-term diabetes damages multiple organ systems with the blood vessels, eyes, kidneys and nervous systems being particularly vulnerable. These complications of diabetes reduce lifespan, impede quality of life and impose a huge social and economic burden on both the individual and society. Peripheral neuropathy is a debilitating complication that will impact over half of all persons with diabetes. There is no treatment for diabetic neuropathy and a disturbingly long history of therapeutic approaches showing promise in preclinical studies but failing to translate to the clinic. These failures have prompted re-examination of both the animal models and clinical trial design. This review focuses on the functional and structural parameters used as indices of peripheral neuropathy in preclinical and clinical studies and the extent to which they share a common pathogenesis and presentation. Nerve conduction studies in large myelinated fibers have long been the mainstay of preclinical efficacy screening programs and clinical trials, supplemented by quantitative sensory tests. However, a more refined approach is emerging that incorporates measures of small fiber density in the skin and cornea alongside these traditional assays at both preclinical and clinical phases.

Relation of exercise and pain in patients with idiopathic distal axonal polyneuropathies

Although exercise is associated with better outcomes in patients with some peripheral neuropathies, data in idiopathic peripheral neuropathies is lacking. This study was completed to do a comprehensive data analysis about the benefits of regular exercise in a well-characterized cohort of patients with idiopathic distal, symmetrical, axonal polyneuropathy enrolled in the Peripheral Neuropathy Research Registry (PNRR) at Johns Hopkins University School of Medicine. From the patient-reported exercise habits, metabolic equivalents (METs) were calculated and the patient information was grouped into four categories. The PNRR data set, including patient reported pain, numbness, and weakness, was analyzed using the METs categories to evaluate for the benefits of exercise. We controlled for the components of metabolic syndrome including Hemoglobin A1c (HbA1c), systolic and diastolic blood pressure (BP), high density lipids (HDL) and triglyceride level, and body mass index (BMI) as defined by the Adult Treatment Panel III Guidelines. Lower METs were associated with neuropathic pain, but not with other peripheral neuropathy symptoms. Patients with IPN who exercised were less likely to have painful neuropathy independent of the average METs per week (P < .01). No significant differences were seen for patient reported numbness, weakness, or balance issues. The data suggests that patients with idiopathic neuropathy benefit from exercises even if performed on a low intensity level or less frequently, and patients are less likely to have severe pain symptoms when exercising on a regular basis.

Diabetes and Metabolic Disorders and the Peripheral Nervous System

PURPOSE OF REVIEW

This article provides an up-to-date review of the manifestations of neuropathy seen in the setting of diabetes and other metabolic disorders.

RECENT FINDINGS

Although a number of metabolic disorders cause or are associated with peripheral neuropathy, the neuropathies associated with glucose dysregulation make up the vast majority of cases. Recent investigations have determined major differences in the neuropathies associated with type 1 and type 2 diabetes. Neuropathy in type 1 diabetes is closely linked to glycemic control, whereas neuropathy in type 2 diabetes is linked to dyslipidemia, central obesity, hypertension, insulin resistance, and glucose control. Although length-dependent axonal distal symmetric polyneuropathy is the most common clinical presentation, diabetes is also associated with acute, asymmetric, painless, and autonomic neuropathies.

SUMMARY

The prevalence of diabetes and metabolic syndrome is increasing across the globe. The need to recognize and treat the wide array of clinical manifestations of neuropathy detected in individuals with metabolic disorders will continue to grow. As a consequence, an increasing number of well-trained physicians who can manage these patients is needed. At present, treatment is largely focused on prevention and symptomatic management. Investments into funding for both basic and clinical science are necessary to bring novel therapeutic interventions into clinical practice.

Microvascular Complications of Type 2 Diabetes Mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) is a chronic, non communicable, multisystem disease that has reached epidemic proportions. Chronic exposure to hyperglycaemia affects the microvasculature, eventually leading to diabetic nephropathy, retinopathy and neuropathy with high impact on the quality of life and overall life expectancy. Sexual dysfunction is an often-overlooked microvascular complication of T2DM, with a complex pathogenesis originating from endothelial dysfunction.

OBJECTIVE

The purpose of this review is to present current definitions, epidemiological data and risk factors for diabetic retinopathy, nephropathy, neuropathy and sexual dysfunction. We also describe the clinical and laboratory evaluation that is mandatory for the diagnosis of these conditions.

METHODS

A comprehensive review of the literature was performed to identify data from clinical studies for the prevalence, risk factors and diagnostic methods of microvascular complications of T2DM.

RESULTS

Diabetic nephropathy and retinopathy affect approximately 25% of patients with T2DM; diabetic neuropathy is encountered in almost 50% of the diabetic population, while the prevalence of erectile dysfunction ranges from 35-90% in diabetic men. The duration of T2DM along with glycemic, blood pressure and lipid control are common risk factors for the development of these complications. Criteria for the diagnosis of these conditions are well established, but exclusion of other causes is mandatory.

CONCLUSION

Early detection of microvascular complications associated with T2DM is important, as early intervention leads to better outcomes. However, this requires awareness of their definition, prevalence and diagnostic modalities.

The Effects of Combined Exercise Training (Resistance-Aerobic) on Serum Kinesin and Physical Function in Type 2 Diabetes Patients with Diabetic Peripheral Neuropathy (Randomized Controlled Trials)

Diabetic peripheral neuropathy is one of the most common chronic complications of diabetics which causes nerve damage and muscle strength decrease in patients. This in turn results in imbalance leading to the diabetic patients' daily activity disparity. The present investigation was conducted to specifically study the effects of combined training (resistance-aerobic) on serum kinesin-1 and physical function in type 2 diabetes patients with diabetic peripheral neuropathy. 24 diabetic neuropathic females were randomly to be selected out and divided into two experimental and control groups. The experimental group received resistance-aerobic training for 3 sessions during eight weeks. The exercise training included resistance exercises with 2-3 sets, 6-7 exercise stations, 8-12 repetitions (reps), and 3-5 minutes of rest in between the exercises, and the aerobic exercises contained 50-65% of heart rate reserve (HRR) for 3 minutes with 30 seconds of rest interval between sets and 5-10 repetitions. Results show that the serum kinesin-1 level and aerobic endurance declined after eight weeks of combined (resistance-aerobic) exercise training, but this decrease was not significant. The upper body strength increased but it was not significant, while the lower body showed a significant strength increase. With regard to the progressive nature of diabetic peripheral neuropathy, it seems that even the little changes resulting from the combined exercise training can be useful. Nevertheless, more research is required in this area.

An Exploratory Randomized Trial of Physical Therapy for the Treatment of Chemotherapy-Induced Peripheral Neuropathy

Background. Chemotherapy-induced peripheral neuropathy (CIPN) is a common side effect of taxane treatment and cannot currently be prevented or adequately treated. Physical therapy is often used for neural rehabilitation following injury but has not been evaluated in this patient population. Methods. Single-blind, randomized controlled exploratory study compared standard care to a physical therapy home program (4 visits) throughout adjuvant taxane chemotherapy for stage I-III patients with breast cancer (n = 48). Patient questionnaires and quantitative sensory testing evaluated the treatment effect throughout chemotherapy to 6 months post treatment. Nonrandomized subgroup analysis observed effect of general exercise on sensory preservation comparing those reporting moderate exercise throughout chemotherapy to those that did not exercise regularly. Clinical Trial Registration. clinicaltrials.gov (NCT02239601). Results. The treatment group showed strong trends toward less pain (odds ratio [OR] 0.41, 95% confidence interval [CI] 0.17-1.01; P = .053) and pain decreased over time (OR 0.85, 95% CI 0.76-0.94; P = .002). Pain pressure thresholds (P = .034) and grip dynamometry (P < .001) were improved in the treatment group. For the nonrandomized subgroup analysis, participants reporting general exercise had preservation of vibration (Left P = .001, Right P = .001) and normal heat pain thresholds (Left P = .021, Right P = .039) compared with more sedentary participants. Conclusion. Physical therapy home program may improve CIPN pain in the upper extremity for patients with breast cancer, and general exercise throughout chemotherapy treatment was observed to have correlated to preservation of sensory function. Further research is required to confirm the impact of a physical therapy home program on CIPN symptoms.

Physical activity and dietary interventions in diabetic neuropathy: a systematic review

PURPOSE

Diabetic neuropathy is a common and disabling disorder, and there are currently no proven effective disease-modifying treatments. Physical activity and dietary interventions in patients with diabetes and diabetic neuropathy have multiple beneficial effects and are generally low risk, which makes lifestyle interventions an attractive treatment option. We reviewed the literature on the effects of physical activity and dietary interventions on length-dependent peripheral neuropathy and cardiac autonomic neuropathy in diabetes.

METHODS

The electronic database PubMed was systematically searched for original human and mouse model studies examining the effect of either dietary or physical activity interventions in subjects with diabetes, prediabetes, or metabolic syndrome.

RESULTS

Twenty studies are included in this review. Fourteen studies were human studies and six were in mice. Studies were generally small with few controlled trials, and there are no widely agreed upon outcome measures.

CONCLUSIONS

Recent research indicates that dietary interventions are effective in modifying diabetic neuropathy in animal models, and there are promising data that they may also ameliorate diabetic neuropathy in humans. It has been known for some time that lifestyle interventions can prevent the development of diabetic neuropathy in type 2 diabetes mellitus subjects. However, there is emerging evidence that lifestyle interventions are effective in individuals with established diabetic neuropathy. In addition to the observed clinical value of lifestyle interventions, there is emerging evidence of effects on biochemical pathways that improve muscle function and affect other organ systems, including the peripheral nerve. However, data from randomized controlled trials are needed.

Diabetic neuropathy

The global epidemic of prediabetes and diabetes has led to a corresponding epidemic of complications of these disorders. The most prevalent complication is neuropathy, of which distal symmetric polyneuropathy (for the purpose of this Primer, referred to as diabetic neuropathy) is very common. Diabetic neuropathy is a loss of sensory function beginning distally in the lower extremities that is also characterized by pain and substantial morbidity. Over time, at least 50% of individuals with diabetes develop diabetic neuropathy. Glucose control effectively halts the progression of diabetic neuropathy in patients with type 1 diabetes mellitus, but the effects are more modest in those with type 2 diabetes mellitus. These findings have led to new efforts to understand the aetiology of diabetic neuropathy, along with new 2017 recommendations on approaches to prevent and treat this disorder that are specific for each type of diabetes. In parallel, new guidelines for the treatment of painful diabetic neuropathy using distinct classes of drugs, with an emphasis on avoiding opioid use, have been issued. Although our understanding of the complexities of diabetic neuropathy has substantially evolved over the past decade, the distinct mechanisms underlying neuropathy in type 1 and type 2 diabetes remains unknown. Future discoveries on disease pathogenesis will be crucial to successfully address all aspects of diabetic neuropathy, from prevention to treatment.

Diabetic neuropathy

The global epidemic of prediabetes and diabetes has led to a corresponding epidemic of complications of these disorders. The most prevalent complication is neuropathy, of which distal symmetric polyneuropathy (for the purpose of this Primer, referred to as diabetic neuropathy) is very common. Diabetic neuropathy is a loss of sensory function beginning distally in the lower extremities that is also characterized by pain and substantial morbidity. Over time, at least 50% of individuals with diabetes develop diabetic neuropathy. Glucose control effectively halts the progression of diabetic neuropathy in patients with type 1 diabetes mellitus, but the effects are more modest in those with type 2 diabetes mellitus. These findings have led to new efforts to understand the aetiology of diabetic neuropathy, along with new 2017 recommendations on approaches to prevent and treat this disorder that are specific for each type of diabetes. In parallel, new guidelines for the treatment of painful diabetic neuropathy using distinct classes of drugs, with an emphasis on avoiding opioid use, have been issued. Although our understanding of the complexities of diabetic neuropathy has substantially evolved over the past decade, the distinct mechanisms underlying neuropathy in type 1 and type 2 diabetes remains unknown. Future discoveries on disease pathogenesis will be crucial to successfully address all aspects of diabetic neuropathy, from prevention to treatment.

Diagnosis and management of sensory polyneuropathy

Sensory polyneuropathies, which are caused by dysfunction of peripheral sensory nerve fibers, are a heterogeneous group of disorders that range from the common diabetic neuropathy to the rare sensory neuronopathies. The presenting symptoms, acuity, time course, severity, and subsequent morbidity vary and depend on the type of fiber that is affected and the underlying cause. Damage to small thinly myelinated and unmyelinated nerve fibers results in neuropathic pain, whereas damage to large myelinated sensory afferents results in proprioceptive deficits and ataxia. The causes of these disorders are diverse and include metabolic, toxic, infectious, inflammatory, autoimmune, and genetic conditions. Idiopathic sensory polyneuropathies are common although they should be considered a diagnosis of exclusion. The diagnostic evaluation involves electrophysiologic testing including nerve conduction studies, histopathologic analysis of nerve tissue, serum studies, and sometimes autonomic testing and cerebrospinal fluid analysis. The treatment of these diseases depends on the underlying cause and may include immunotherapy, mitigation of risk factors, symptomatic treatment, and gene therapy, such as the recently developed RNA interference and antisense oligonucleotide therapies for transthyretin familial amyloid polyneuropathy. Many of these disorders have no directed treatment, in which case management remains symptomatic and supportive. More research is needed into the underlying pathophysiology of nerve damage in these polyneuropathies to guide advances in treatment.

Randomized Controlled Trial of Physical Exercise in Diabetic Veterans With Length-Dependent Distal Symmetric Polyneuropathy

Rationale: Physical exercise is an essential adjunct to the management of patients with type 2 diabetes mellitus. Therapeutic interventions that improve blood flow to peripheral nerves, such as exercise, may slow the progression of neuropathy in the diabetic patient.

Aims: This randomized clinical trial was conducted to determine whether a structured program of aerobic, isokinetic strength, or the combination of aerobic–isokinetic strength exercise intervention alters peripheral nerve function in glycemic-controlled diabetic patients with advanced length-dependent distal symmetric polyneuropathy.

Methods: Forty-five patients with type 2 diabetes mellitus exhibiting tight glycemic control (HbA_1c intergroup range 7.2–8.0%) were randomized by block design across four experimental groups: sedentary controls (n = 12), aerobic exercise (n = 11), isokinetic strength (n = 11), or the combination of aerobic–isokinetic strength training (n = 11). Patients randomized to training groups exercised 3× per week for 12 weeks, whereas patients randomized to the sedentary control group received standard of care. To minimize attention and educational bias, all patients attended a 12-session health promotion educational series. At baseline, immediately following intervention, and again at 12-week post-intervention, detailed nerve conduction studies were conducted as a primary outcome measure. At these same intervals, all patients completed as secondary measures quantitative sensory testing, symptom-limited treadmill stress tests, and a Short-Form 36-Veterans Questionnaire (SF-36V).

Results: Of the 45 patients randomized into this study, 37 (82%) had absent sural nerve responses, 19 (42%) had absent median sensory nerve responses, and 17 (38%) had absent ulnar sensory nerve responses. By comparison, responses from tibial nerves were absent in only three (7%) subjects while responses from peroneal nerves were absent in five (11%) subjects. Eleven (92%) of 12 patients that had volunteered to be biopsied exhibited abnormal levels of epidermal nerve fiber densities. Exercise, regardless of type, did not alter sensory or motor nerve electrodiagnostic findings among those patients exhibiting measurable responses (ANOVA). There was, however, a modest (p = 0.01) beneficial effect of exercise on sensory nerve function (Fisher’s Exact Test). Importantly, the beneficial effect of exercise on sensory nerve function was enhanced (p = 0.03) during the post-intervention interval. In addition, three of six patients that had undergone exercise intervention exhibited a marked 1.9 ± 0.3-fold improvement in epidermal nerve fiber density. By comparison, none of three sedentary patients whom agreed to be biopsied a second time showed improvement in epidermal nerve fiber density. Compared to baseline values within groups, and compared with sedentary values across groups, neither aerobic, isokinetic strength, or the combination of aerobic–isokinetic strength exercise intervention altered peak oxygen uptake. Patients that underwent aerobic or the combined aerobic–isokinetic strength exercise intervention, however, demonstrated an increase in treadmill test duration that was sustained over the 12-week post-intervention period.

Conclusion: A 12-week course of physical exercise, regardless of type, does not alter sensory or motor nerve electrodiagnostic findings. In a subset of patients, a short-term structured program of aerobic exercise may selectively improve sensory nerve fiber function. Large-scale exercise lifestyle intervention trials are warranted to further evaluate the impact of aerobic exercise on sensory nerve fiber function in diabetic neuropathic patients.

Clinical Trial Registration:www.ClinicalTrials.gov, identifier NCT00955201.

Aerobic exercise training may improve nerve function in type 2 diabetes and pre-diabetes: A systematic review

Diabetic neuropathy is a major complication of type 2 diabetes. Emerging evidence also suggests that people with pre-diabetes may develop similar symptoms related to nerve dysfunction. While regular exercise provides many benefits to patients with diabetes, whether exercise influences nerve function has not been established. As such, the aim of this systematic review was to evaluate current evidence regarding the effect of exercise training on the progression and development of diabetic neuropathy. A systematic search of MEDLINE (Ovid), CINAHL, AMED, PEDro, the Cochrane Library, Embase, and Scopus databases identified a total of 12 studies that were eligible for inclusion in this systematic review. Quality rating and data extraction were performed by two independent reviewers. The 12 included studies examined people with pre-diabetes (n = 1) and with type 2 diabetes (n = 11). There was heterogeneity of study quality and exercise type and dosage among these studies. Eleven studies reported that exercise training had a positive influence on nerve function or neuropathy-related symptoms; and only one study reported mild adverse events. Evidence from this systematic review suggests aerobic exercise training may positively influence nerve function among people with type 2 diabetes, with minimal risk of adverse events. Further research will be required to determine the optimal dosage of exercise training and the effect on nerve function in pre-diabetes and in women with previous gestational diabetes. This review is registered on PROSPERO (CRD42018088182).

Update on the Management of Diabetic Neuropathy

IN BRIEF Distal symmetric polyneuropathy (DSPN) and diabetic autonomic neuropathies, particularly cardiovascular autonomic neuropathy (CAN), are prevalent diabetes complications with high morbidity, mortality, and amputation risks. The diagnosis of DSPN is principally a clinical one based on the presence of typical symptoms combined with symmetrical, distal-to-proximal stocking-glove sensory loss. CAN is an independent risk factor for cardiovascular mortality, arrhythmia, silent ischemia, major cardiovascular events, and myocardial dysfunction. Screening for CAN in high-risk patients is recommended. Symptoms of gastroparesis are nonspecific and do not correspond with its severity. Diagnosis of gastroparesis should exclude other factors well documented to affect gastric emptying such as hyperglycemia, hypoglycemia, and certain medications. There is a lack of treatment options targeting the neuropathic disease state. Managing neuropathic pain also remains a challenge. Given the high risk of addiction, abuse, psychosocial issues, and mortality, opioids are not recommended as first-, second-, or third-line agents for treating painful DSPN.

Cardiac autonomic neuropathy: Risk factors, diagnosis and treatment

Cardiac autonomic neuropathy (CAN) is a serious complication of diabetes mellitus (DM) that is strongly associated with approximately five-fold increased risk of cardiovascular mortality. CAN manifests in a spectrum of things, ranging from resting tachycardia and fixed heart rate (HR) to development of "silent" myocardial infarction. Clinical correlates or risk markers for CAN are age, DM duration, glycemic control, hypertension, and dyslipidemia (DLP), development of other microvascular complications. Established risk factors for CAN are poor glycemic control in type 1 DM and a combination of hypertension, DLP, obesity, and unsatisfactory glycemic control in type 2 DM. Symptomatic manifestations of CAN include sinus tachycardia, exercise intolerance, orthostatic hypotension (OH), abnormal blood pressure (BP) regulation, dizziness, presyncope and syncope, intraoperative cardiovascular instability, asymptomatic myocardial ischemia and infarction. Methods of CAN assessment in clinical practice include assessment of symptoms and signs, cardiovascular reflex tests based on HR and BP, short-term electrocardiography (ECG), QT interval prolongation, HR variability (24 h, classic 24 h Holter ECG), ambulatory BP monitoring, HR turbulence, baroreflex sensitivity, muscle sympathetic nerve activity, catecholamine assessment and cardiovascular sympathetic tests, heart sympathetic imaging. Although it is common complication, the significance of CAN has not been fully appreciated and there are no unified treatment algorithms for today. Treatment is based on early diagnosis, life style changes, optimization of glycemic control and management of cardiovascular risk factors. Pathogenetic treatment of CAN includes: Balanced diet and physical activity; optimization of glycemic control; treatment of DLP; antioxidants, first of all α-lipoic acid (ALA), aldose reductase inhibitors, acetyl-L-carnitine; vitamins, first of all fat-soluble vitamin B1; correction of vascular endothelial dysfunction; prevention and treatment of thrombosis; in severe cases-treatment of OH. The promising methods include prescription of prostacyclin analogues, thromboxane A2 blockers and drugs that contribute into strengthening and/or normalization of Na+, K+-ATPase (phosphodiesterase inhibitor), ALA, dihomo-γ-linolenic acid (DGLA), ω-3 polyunsaturated fatty acids (ω-3 PUFAs), and the simultaneous prescription of ALA, ω-3 PUFAs and DGLA, but the future investigations are needed. Development of OH is associated with severe or advanced CAN and prescription of nonpharmacological and pharmacological, in the foreground midodrine and fludrocortisone acetate, treatment methods are necessary.