Exercise as Therapy for Diabetic and Prediabetic Neuropathy

Prediabetes is an independent risk factor for sarcopenia in older men, but not in older women: the Bunkyo Health Study

BACKGROUND

Sarcopenia is a major cause of disability in the elderly. Although type 2 diabetes is a risk factor for increased sarcopenia, the relationship between prediabetes and sarcopenia has not been elucidated. We aimed to examine the relationship between sarcopenia and prediabetes.

METHODS

The design of this study is a cross-sectional study. We evaluated glucose metabolism using the 75-g oral glucose tolerance test and glycated haemoglobin, appendicular skeletal muscle mass, and hand grip strength in 1629 older adults living in an urban area of Tokyo, Japan. We investigated the frequency of sarcopenia in participants with normal glucose tolerance (NGT), prediabetes and diabetes. A multivariable logistic regression model was used to analyse the association between glucose tolerance and the prevalence of sarcopenia.

RESULTS

The mean age of participants was 73.1 ± 5.4 years. In men, 44.3% had NGT, 26.6% had prediabetes, and 29.1% had diabetes. In women, the distribution was 56.1%, 28.8% and 15.2%. The prevalence of sarcopenia was 12.7% in men and 11.9% in women. Logistic regression revealed that prediabetes and diabetes are independent risk factors for sarcopenia in men (prediabetes, odds ratio [OR] = 2.081 [95% confidence interval {CI}: 1.031-4.199]; diabetes, OR = 2.614 [95% CI: 1.362-5.018]) and diabetes, but not prediabetes, is an independent risk factor for sarcopenia in women (prediabetes, OR = 1.036 [95% CI: 0.611-1.757]; diabetes, OR = 2.099 [95% CI: 1.146-3.844]). In both sexes, higher age (men, OR = 1.086 [95% CI: 1.028-1.146]; women, OR = 1.195 [95% CI: 1.142-1.251]), higher body fat percentage (men, OR = 1.346 [95% CI: 1.240-1.461]; women, OR = 1.218 [95% CI: 1.138-1.303]) and lower body mass index (men, OR = 0.371 [95% CI: 0.299-0.461]; women, OR = 0.498 [95% CI: 0.419-0.593]) were independent risk factors for sarcopenia.

CONCLUSIONS

Although we confirmed that diabetes mellitus is associated with sarcopenia in both sexes, prediabetes is associated with sarcopenia in men, but not in women.

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.

High-intensity interval training for 12 weeks improves cardiovascular autonomic function but not somatosensory nerve function and structure in overweight men with type 2 diabetes

AIMS/HYPOTHESIS

It remains unclear whether and which modality of exercise training as a component of lifestyle intervention may exert favourable effects on somatosensory and autonomic nerve tests in people with type 2 diabetes.

METHODS

Cardiovascular autonomic and somatosensory nerve function as well as intraepidermal nerve fibre density (IENFD) were assessed in overweight men with type 2 diabetes (type 2 diabetes, n = 20) and male glucose-tolerant individuals (normal glucose tolerance [NGT], n = 23), comparable in age and BMI and serving as a control group, before and after a supervised high-intensity interval training (HIIT) intervention programme over 12 weeks. Study endpoints included clinical scores, nerve conduction studies, quantitative sensory testing, IENFD, heart rate variability, postural change in systolic blood pressure and spontaneous baroreflex sensitivity (BRS).

RESULTS

After 12 weeks of HIIT, resting heart rate decreased in both groups ([mean ± SD] baseline/12 weeks: NGT: 65.1 ± 8.2/60.2 ± 9.0 beats per min; type 2 diabetes: 68.8 ± 10.1/63.4 ± 7.8 beats per min), while three BRS indices increased (sequence analysis BRS: 8.82 ± 4.89/14.6 ± 11.7 ms²/mmHg; positive sequences BRS: 7.19 ± 5.43/15.4 ± 15.9 ms²/mmHg; negative sequences BRS: 12.8 ± 5.4/14.6 ± 8.7 ms²/mmHg) and postural change in systolic blood pressure decreased (-13.9 ± 11.6/-9.35 ± 9.76 mmHg) in participants with type 2 diabetes, and two heart rate variability indices increased in the NGT group (standard deviation of R-R intervals: 36.1 ± 11.8/55.3 ± 41.3 ms; coefficient of R-R interval variation: 3.84 ± 1.21/5.17 ± 3.28) (all p<0.05). In contrast, BMI, clinical scores, nerve conduction studies, quantitative sensory testing, IENFD and the prevalence rates of diabetic sensorimotor polyneuropathy and cardiovascular autonomic neuropathy remained unchanged in both groups. In the entire cohort, correlations between the changes in two BRS indices and changes in [Formula: see text] over 12 weeks of HIIT (e.g. sequence analysis BRS: r = 0.528, p=0.017) were observed.

CONCLUSIONS/INTERPRETATION

In male overweight individuals with type 2 diabetes, BRS, resting heart rate and orthostatic blood pressure regulation improved in the absence of weight loss after 12 weeks of supervised HIIT. Since no favourable effects on somatic nerve function and structure were observed, cardiovascular autonomic function appears to be more amenable to this short-term intervention, possibly due to improved cardiorespiratory fitness.

Effect of lower body positive pressure aerobic training on fall risk in patients with diabetic polyneuropathy: randomized controlled trial

BACKGROUND

Retarded task-oriented gait, balance performance and increased fall risk are among the most debilitating problems in patients with diabetic polyneuropathy (DPN). The lower body positive pressure (LBPP) training was recently introduced in the field of rehabilitation, but evaluating the effects of the LBPP on gait, balance and fall risk in patients with DPN has not been thoroughly investigated.

AIM

The aim of this study was to evaluate the effect of LBPP treadmill training program on task-oriented gait, balance performance and fall risk in patients with DPN.

DESIGN

Single-blinded, randomized-controlled trial.

SETTING

Rehabilitative outpatient unit.

POPULATION

Sixty-two patients with DPN were randomly assigned into 5-groups; group-A (100% weight-bearing; N.=12), group-B (75% weight-bearing; N.=13), group-C (50% weight-bearing; N.=13), group-D (25% weight-bearing; N.=12) and group-E (control group; N.=12).

METHODS

The intervention groups (A, B, C, D) received moderate intensity aerobic exercise training (AET) program (30-45 minutes, 50-70% heart rate reserve) on the AlterG (AlterG, Inc., Fremont, CA, USA) treadmill for 12-weeks. Task-oriented gait, balance performance and the fall risk were evaluated at baseline (evaluation-1), after 12-weeks (evaluation-2) and 12-weeks poststudy cessation (evaluation-3; follow-up) for all groups using the Tinetti balance assessment tool.

RESULTS

At evaluation-2, there were significant "within-groups" increases in the balance, gait and fall risk scores. There were significant "between-groups" differences in the same evaluated variables, with the highest increases were in group-B (P<0.05). At evaluation-3, there was a decline in the mean values of the evaluated variables, but still significant increases in the mean values of balance, gait and fall risk compared to the baseline mean values. There were significant "between-groups" differences in all variables, with the highest increases were in group-B (P<0.05).

CONCLUSIONS

Moderate intensity LBPP treadmill training program can effectively improve task-oriented gait, balance performance, and fall risk scores in patients with DPN. The 25% off-loading weight percentage during the LBPP treadmill training program yielded the most favorable short and long-term improvements compared to the other weight off-loading percentages in patients with DPN.

CLINICAL REHABILITATION IMPACT

The LBPP aerobic training program is an effective rehabilitation procedure in patients with DPN especially when utilizing the 25% off-loading weight percentage during the LBPP treadmill training program.

Treatment for Diabetic Peripheral Neuropathy: What have we Learned from Animal Models?

INTRODUCTION

Animal models have been widely used to investigate the etiology and potential treatments for diabetic peripheral neuropathy. What we have learned from these studies and the extent to which this information has been adapted for the human condition will be the subject of this review article.

METHODS

A comprehensive search of the PubMed database was performed, and relevant articles on the topic were included in this review.

RESULTS

Extensive study of diabetic animal models has shown that the etiology of diabetic peripheral neuropathy is complex, with multiple mechanisms affecting neurons, Schwann cells, and the microvasculature, which contribute to the phenotypic nature of this most common complication of diabetes. Moreover, animal studies have demonstrated that the mechanisms related to peripheral neuropathy occurring in type 1 and type 2 diabetes are likely different, with hyperglycemia being the primary factor for neuropathology in type 1 diabetes, which contributes to a lesser extent in type 2 diabetes, whereas insulin resistance, hyperlipidemia, and other factors may have a greater role. Two of the earliest mechanisms described from animal studies as a cause for diabetic peripheral neuropathy were the activation of the aldose reductase pathway and increased non-enzymatic glycation. However, continuing research has identified numerous other potential factors that may contribute to diabetic peripheral neuropathy, including oxidative and inflammatory stress, dysregulation of protein kinase C and hexosamine pathways, and decreased neurotrophic support. In addition, recent studies have demonstrated that peripheral neuropathy-like symptoms are present in animal models, representing pre-diabetes in the absence of hyperglycemia.

CONCLUSION

This complexity complicates the successful treatment of diabetic peripheral neuropathy, and results in the poor outcome of translating successful treatments from animal studies to human clinical trials.

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.

Weight Reduction as an Adjunctive Management Strategy for Diabetic Retinopathy

As rates of global obesity and diabetes increase, diabetic retinopathy continues to grow as a frequent cause of visual impairment. Despite tremendous recent strides in therapy, a significant fraction of patients remain poorly responsive to modern interventions. Adjunctive therapy in such settings could be widely beneficial. A growing body of evidence suggests that weight reduction strategies for obesity-related diabetes have the potential to serve as important supplements to modern ophthalmic care for preservation of vision.

Cardiac Autonomic Modulation in Response to Three Types of Exercise in Patients with Type 2 Diabetic Neuropathy

Purpose

Physical exercise is necessary in the handling DM, but it is not distinct which kind of physical exercise can improve cardiac autonomic modulation in T2DM. The purpose of this study was to compare the effects of three different modalities of exercise (aerobic, resistant, and combined) on cardiac autonomic modulation as measured by HRV in patients with type 2 diabetic neuropathy.

Methods

The participants were 45 men (age: 55.24 ± 8.11 years, weight: 89.5 ± 13.4 kg, height: 171.85 ± 6.98 cm, duration of diabetes: 12.51 ± 6.46 years) with type 2 diabetic neuropathy who were clinically free from signs and symptoms of cardiovascular disease. Participants were randomly assigned to one of four groups: aerobic-training (n = 11), dynamic resistant-training (n = 11), Combined-training (n = 11), or a non-exercise control group (n = 12). The exercise groups performed aerobic and resistant exercise for 25-45 min per day, 3-5 times per week for 12 weeks. Anthropometrics, biochemical markers (FBS, HbA1c, Lipid Profile, and Insulin), and heart rate variability in the exercise laboratory and under ambulatory conditions by 3-channel ECG digital Holter recorder were examined.

Results

All time and frequency-domain HRV parameters (except LF power) were significantly improved in the exercise groups, compared with the control group (p < 0.05). SDNN, rMSSD, and HF power were boosted, LF power was not different, and the LF/HF ratio decreased after versus before exercise training, independent of exercise modality. HbA1c in aerobic and resistant-training groups, and insulin and LDL in the resistant-training group were decreased after exercise training (p < 0.05).

Conclusions

Exercise training, independent of modality, in patients with type 2 diabetic neuropathy who were clinically free of the cardiovascular disease cause to significant progress in cardiovascular autonomic function assessed by HRV via enhancing cardio-vagal and reducing cardio-sympathetic tone.

Lower extremity MRI following 10-week supervised exercise intervention in patients with diabetic peripheral neuropathy

INTRODUCTION

The purpose of this study was to characterize using MRI the effects of a 10-week supervised exercise program on lower extremity skeletal muscle composition, nerve microarchitecture, and metabolic function in individuals with diabetic peripheral neuropathy (DPN).

RESEARCH DESIGN AND METHODS

Twenty participants with DPN completed a longitudinal trial consisting of a 30-day control period, during which subjects made no change to their lifestyle, followed by a 10-week intervention program that included three supervised aerobic and resistance exercise sessions per week targeting the upper and lower extremities. The participants' midcalves were scanned with multinuclear MRI two times prior to intervention (baseline₁ and baseline₂) and once following intervention to measure relaxation times (T1, T1ρ, and T2), phosphocreatine recovery, fat fraction, and diffusion parameters.

RESULTS

There were no changes between baseline₁ and baseline₂ MRI metrics (p>0.2). Significant changes (p<0.05) between baseline₂ and postintervention MRI metrics were: gastrocnemius medialis (GM) T1 -2.3%±3.0% and soleus T2 -3.2%±3.1%. Trends toward significant changes (0.05<p<0.1) between baseline₂ and postintervention MRI metrics were: calf adipose infiltration -2.6%±6.4%, GM T1ρ -4.1%±7.7%, GM T2 -3.5%±6.4%, and gastrocnemius lateral T2 -4.6±7.4%. Insignificant changes were observed in gastrocnemius phosphocreatine recovery rate constant (p>0.3) and tibial nerve fractional anisotropy (p>0.6) and apparent diffusion coefficient (p>0.4).

CONCLUSIONS

The 10-week supervised exercise intervention program successfully reduced adiposity and altered resting tissue properties in the lower leg in DPN. Gastrocnemius mitochondrial oxidative capacity and tibial nerve microarchitecture changes were not observed, either due to lack of response to therapy or to lack of measurement sensitivity.

Ethoxyquin is neuroprotective and partially prevents somatic and autonomic neuropathy in db/db mouse model of type 2 diabetes

Ethoxyquin (EQ), a quinolone-based antioxidant, has demonstrated neuroprotective properties against several neurotoxic drugs in a phenotypic screening and is shown to protect axons in animal models of chemotherapy-induced peripheral neuropathy. We assessed the effects of EQ on peripheral nerve function in the db/db mouse model of type II diabetes. After a 7 week treatment period, 12-week-old db/db-vehicle, db/+ -vehicle and db/db-EQ treated animals were evaluated by nerve conduction, paw withdrawal against a hotplate, and fiber density in hindlimb footpads. We found that the EQ group had shorter paw withdrawal latency compared to vehicle db/db group. The EQ group scored higher in nerve conduction studies, compared to vehicle-treated db/db group. Morphology studies yielded similar results. To investigate the potential role of mitochondrial DNA (mtDNA) deletions in the observed effects of EQ, we measured total mtDNA deletion burden in the distal sciatic nerve. We observed an increase in total mtDNA deletion burden in vehicle-treated db/db mice compared to db/+ mice that was partially prevented in db/db-EQ treated animals. These results suggest that EQ treatment may exert a neuroprotective effect in diabetic neuropathy. The prevention of diabetes-induced mtDNA deletions may be a potential mechanism of the neuroprotective effects of EQ in diabetic neuropathy.

Management of Neuropathic Pain in Polyneuropathy

PURPOSE OF REVIEW

Many polyneuropathies cause significant neuropathic pain, resulting in substantial morbidity and reduced quality of life. Appropriate management is crucial for maintaining quality of life for patients with painful polyneuropathies. The US Food and Drug Administration (FDA) has only approved one new drug for painful diabetic neuropathy in the past decade, a topical capsaicin patch that was initially approved for the treatment of postherpetic neuralgia in 2009. Gabapentinoids and serotonin norepinephrine reuptake inhibitors (SNRIs) continue to have an advantage in safety profiles and efficacy. Other antiepileptic medications remain second-line agents because of fewer studies documenting efficacy.

RECENT FINDINGS

This article reviews recent literature on complementary and pharmacologic therapies for the management of painful polyneuropathies. Exercise has emerged as an important therapeutic tool and may also improve the underlying polyneuropathy in the setting of obesity, metabolic syndrome, and diabetes.

SUMMARY

The approach to management of painful polyneuropathies is multifactorial, using both pharmacologic and nonpharmacologic measures to improve pain severity and patient quality of life.

Metabolic Factors, Lifestyle Habits, and Possible Polyneuropathy in Early Type 2 Diabetes: A Nationwide Study of 5,249 Patients in the Danish Centre for Strategic Research in Type 2 Diabetes (DD2) Cohort

OBJECTIVE

To investigate the association of metabolic and lifestyle factors with possible diabetic polyneuropathy (DPN) and neuropathic pain in patients with early type 2 diabetes.

RESEARCH DESIGN AND METHODS

We thoroughly characterized 6,726 patients with recently diagnosed diabetes. After a median of 2.8 years, we sent a detailed questionnaire on neuropathy, including the Michigan Neuropathy Screening Instrument questionnaire (MNSIq), to identify possible DPN (score ≥4) and the Douleur Neuropathique en 4 Questions (DN4) questionnaire for possible associated neuropathic pain (MNSIq ≥4 + pain in both feet + DN4 score ≥3).

RESULTS

Among 5,249 patients with data on both DPN and pain, 17.9% (n = 938) had possible DPN, including 7.4% (n = 386) with possible neuropathic pain. In regression analyses, central obesity (waist circumference, waist-to-hip ratio, and waist-to-height ratio) was markedly associated with DPN. Other important metabolic factors associated with DPN included hypertriglyceridemia ≥1.7 mmol/L, adjusted prevalence ratio (aPR) 1.36 (95% CI 1.17; 1.59); decreased HDL cholesterol <1.0/1.2 mmol/L (male/female), aPR 1.35 (95% CI 1.12; 1.62); hs-CRP ≥3.0 mg/L, aPR 1.66 (95% CI 1.42; 1.94); C-peptide ≥1,550 pmol/L, aPR 1.72 (95% CI 1.43; 2.07); HbA_1c ≥78 mmol/mol, aPR 1.42 (95% CI 1.06; 1.88); and antihypertensive drug use, aPR 1.34 (95% CI 1.16; 1.55). Smoking, aPR 1.50 (95% CI 1.24; 1.81), and lack of physical activity (0 vs. ≥3 days/week), aPR 1.61 (95% CI 1.39; 1.85), were also associated with DPN. Smoking, high alcohol intake, and failure to increase activity after diabetes diagnosis associated with neuropathic pain.

CONCLUSIONS

Possible DPN was associated with metabolic syndrome factors, insulin resistance, inflammation, and modifiable lifestyle habits in early type 2 diabetes.

Berendschot T, S.A.G. Schouten J, Kroon AA, van der Kallen CJ, Henry RM, van Dongen MC, J.P.M. Eussen S, H.C.M. Savelberg H, van der Berg JD, Schaper NC, Schram MT, Stehouwer CD. Higher levels of daily physical activity are associated with better skin microvascular function in type 2 diabetes-The Maastricht Study

OBJECTIVE

Physical activity may provide a means for the prevention of cardiovascular disease via improving microvascular function. Therefore, this study investigated whether physical activity is associated with skin and retinal microvascular function.

METHODS

In The Maastricht Study, a population-based cohort study enriched with type 2 diabetes (n = 1298, 47.3% women, aged 60.2 ± 8.1 years, 29.5% type 2 diabetes), we studied whether accelerometer-assessed physical activity and sedentary time associate with skin and retinal microvascular function. Associations were studied by linear regression and adjusted for major cardiovascular risk factors. In addition, we investigated whether associations were stronger in type 2 diabetes.

RESULTS

In individuals with type 2 diabetes, total physical activity and higher-intensity physical activity were independently associated with greater heat-induced skin hyperemia (regression coefficients per hour), respectively, 10 (95% CI: 1; 18) and 36 perfusion units (14; 58). In individuals without type 2 diabetes, total physical activity and higher-intensity physical activity were not associated with heat-induced skin hyperemia. No associations with retinal arteriolar %-dilation were identified.

CONCLUSION

Higher levels of total and higher-intensity physical activity were associated with greater skin microvascular vasodilation in individuals with, but not in those without, type 2 diabetes.

Systematic review of the effectiveness of self-initiated interventions to decrease pain and sensory disturbances associated with peripheral neuropathy

PURPOSE

A small number of studies report that patients with peripheral neuropathy (PN) who engage in activities that promote a sense of personal well-being and provide physical, emotional, or spiritual comfort have a better quality of life and higher levels of adjustment to the changes generated by their illness and accompanying symptoms. This systematic review sought to evaluate the effectiveness of self-management activities that patients with PN initiate themselves to relieve PN symptoms and improve quality of life.

METHODS

Search terms were limited to include self-management activities initiated by patients (i.e., activities with no or minimal involvement from clinicians) that aim to provide relief of PN symptoms. Outcomes included in searches were pain, numbness, and tingling, associated with PN and quality of life.

RESULTS

The database searches identified 2979 records, of which 1620 were duplicates. A total of 1322 papers were excluded on the basis of screening the abstract. An additional 21 full text articles were excluded because they did not meet the eligibility criteria. A total of 16 papers were included in the review.

CONCLUSION

This review identified that a number of self-management strategies that were initiated by patients, including heat, exercise, meditation, and transcutaneous electrical nerve stimulation (TENS) therapy, may reduce self-reported PN symptoms. As the available studies were of low quality, these strategies warrant further investigation with more homogeneous samples, using more rigorously designed trials and larger samples.

IMPLICATIONS FOR CANCER SURVIVORS

Patients experiencing PN may find a range of self-initiated strategies beneficial in reducing PN symptoms and improving quality of life. However, because of the low quality of the available studies, clinicians need to monitor patients' responses to determine the effectiveness of these interventions as adjuncts to clinician-initiated interventions.

Effects of 8-Week Whole-Body Vibration Training on the HbA1c, Quality of Life, Physical Fitness, Body Composition and Foot Health Status in People with T2DM: A Double-Blinded Randomized Controlled Trial

The aim of this study was to analyze the effects of an 8-week whole-body vibration (WBV) on the quality of life, physical fitness, body composition, glycosylate hemoglobin (HbA1c), lipid profile, and foot health status in people with type II diabetes mellitus (T2DM). It was performed as a double-blinded randomized controlled trial of 90 people with T2DM. Primary care facilities were used. The 8-week WBV training consisted of maintaining a knee flexion at 45° during five to nine series of 30-60 s in a vibration frequency that oscillated between 12.5-18.5 and 30 s of recovery between series. The placebo group had to perform the same protocol but without vibration. Participants performed the protocol three times per week. The WBV training significantly reduced the fat mass (%) of people with T2DM. However, significant effects of WBV training were not found in the quality of life, physical fitness, foot health status, lipid profile, blood pressure, fasting blood glucose, or HbA1c. Nevertheless, within groups enhances were found in HbA1c, blood pressure, fasting blood glucose, foot health status, health-related quality of life, timed-up and go test, and chair-stand test in both WBV and placebo groups. WBV was shown to be beneficial for reducing the fat mass and lipid profile of people with T2DM. The improvements of the placebo group could be due to both the social benefits of enrolling in an intervention and the physical fitness benefits of isometric contractions. Further studies are needed to clarify the effects of WBV and to establish a dose-response relationship in people with T2DM.

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.

The Effects of Diabetes and High-Fat Diet on Polymodal Nociceptor and Cold Thermoreceptor Nerve Terminal Endings in the Corneal Epithelium

Purpose

There is a substantial body of evidence indicating that corneal sensory innervation is affected by pathology in a range of diseases. However, there are no published studies that have directly assessed whether the nerve fiber density of the different subpopulations of corneal sensory neurons are differentially affected. The present study explored the possibility that the intraepithelial nerve fiber density of corneal polymodal nociceptors and cold thermoreceptors are differentially affected in mice fed with a high-fat high cholesterol (HFHC; 21% fat, 2% cholesterol) diet and in those that also have diabetes.

Methods

The mice were fed the HFHC diet for the duration of the experiment (up to 40 weeks). Mice in the diabetes group had hyperglycaemia induced with streptozotocin after 15 weeks on the HFHC diet. Age-matched control animals were fed a standard diet. All corneal nerve fibers were labeled with a pan neuronal antibody (antiprotein gene product 9.5), and polymodal nociceptors and cold thermoreceptors were labeled with antibodies directed against transient receptor potential cation channel, subfamily V, member 1 and transient receptor potential cation channel subfamily M member 8, respectively.

Results

The mice fed a HFHC diet and those that in addition have hyperglycemia have similar reductions in corneal nerve fiber density consistent with small fiber neuropathy. Importantly, both treatments more markedly affected the intraepithelial axons of cold thermoreceptors than those of polymodal nociceptors.

Conclusions

The results provide evidence that distinct subpopulations of corneal sensory neurons can be differentially affected by pathology.

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.

Emerging Biomarkers, Tools, and Treatments for Diabetic Polyneuropathy

Diabetic neuropathy, with its major clinical sequels, notably neuropathic pain, foot ulcers, and autonomic dysfunction, is associated with substantial morbidity, increased risk of mortality, and reduced quality of life. Despite its major clinical impact, diabetic neuropathy remains underdiagnosed and undertreated. Moreover, the evidence supporting a benefit for causal treatment is weak at least in patients with type 2 diabetes, and current pharmacotherapy is largely limited to symptomatic treatment options. Thus, a better understanding of the underlying pathophysiology is mandatory for translation into new diagnostic and treatment approaches. Improved knowledge about pathogenic pathways implicated in the development of diabetic neuropathy could lead to novel diagnostic techniques that have the potential of improving the early detection of neuropathy in diabetes and prediabetes to eventually embark on new treatment strategies. In this review, we first provide an overview on the current clinical aspects and illustrate the pathogenetic concepts of (pre)diabetic neuropathy. We then describe the biomarkers emerging from these concepts and novel diagnostic tools and appraise their utility in the early detection and prediction of predominantly distal sensorimotor polyneuropathy. Finally, we discuss the evidence for and limitations of the current and novel therapy options with particular emphasis on lifestyle modification and pathogenesis-derived treatment approaches. Altogether, recent years have brought forth a multitude of emerging biomarkers reflecting different pathogenic pathways such as oxidative stress and inflammation and diagnostic tools for an early detection and prediction of (pre)diabetic neuropathy. Ultimately, these insights should culminate in improving our therapeutic armamentarium against this common and debilitating or even life-threatening condition.

Is there an overlooked “window of opportunity” in MS exercise therapy? Perspectives for early MS rehabilitation

While early medical treatment has proven effective in MS, early-phase MS rehabilitation has not gained much attention in MS research and clinical practice. Exercise therapy is one of the most promising treatment strategies in MS rehabilitation. Here, we provide a topical review investigating when exercise therapy is initiated in existing MS studies, showing that exercise is initiated at a rather late disease stage, where it predominantly serves as a symptomatic treatment. Recent findings in MS suggest that exercise may have neuroprotective and disease-modifying effects. Such findings along with the findings from medical trials that an early-stage “window of opportunity” exists leads to the proposal that early exercise therapy should be an increased focus in research and clinical practice for persons with MS. A further perspective relates to other rehabilitation interventions that are also initiated at a later disease stage, as these may also take advantage of an early-phase approach.

Upper limb robotics applied to neurorehabilitation: An overview of clinical practice

BACKGROUND

During the last two decades, extensive interaction between clinicians and engineers has led to the development of systems that stimulate neural plasticity to optimize motor recovery after neurological lesions. This has resulted in the expansion of the field of robotics for rehabilitation. Studies in patients with stroke-related upper-limb paresis have shown that robotic rehabilitation can improve motor capacity. However, few other applications have been evaluated (e.g. tremor, peripheral nerve injuries or other neurological diseases).

PURPOSE

This paper presents an overview of the current use of upper limb robotic systems for neurorehabilitation, and highlights the rationale behind their use for the assessment and treatment of common neurological disorders.

CONCLUSIONS

Rehabilitation robots are little integrated in clinical practice, except after stroke. Although few studies have been carried out to evaluate their effectiveness, evidence from the neurosciences and indications from pilot studies suggests that upper limb robotic rehabilitation can be applied safely in various other neurological conditions. Rehabilitation robots provide an intensity, quality and dose of treatment that exceeds therapist-mediated rehabilitation. Moreover, the use of force fields, multi-sensory environments, feedback etc. renders such rehabilitation engaging and motivating. Future studies should evaluate the effectiveness of rehabilitation robots in neurological pathologies other than stroke.

Peripheral nerve disease

Polyneuropathies are common neurologic disorders affecting the peripheral nerves. There are a number of causes of damage to these structures, such as genetic and metabolic factors, autoimmune disorders, infection, drug or environmental toxicity, and malignancy. Motor and sensory impairments are commonly encountered in these conditions, leading to altered balance and gait with increased risk of falling. Diabetic neuropathy is the most common cause of peripheral nerve disease and extensive investigation of balance and walking function revealed greater postural instability and delayed activation of distal muscles during walking. Although classically thought to be due to sensory impairment, it is now recognized that a motor contribution to balance and gait impairment cannot be ruled out in diabetic neuropathy. Inflammatory and inherited neuropathies have had less investigation. Variations in static and dynamic balance and depend on the sensory afferents affected and the degree of motor impairment. Motor impairment is a major contributor to alterations in gait pattern. Exercise is an effective rehabilitation approach that can improve muscle strength and postural responses. The gains can carry over into improved functional balance and walking. Orthotic interventions are also promising in supporting joints where there is significant muscle weakness, but newer devices are being developed that provide sensory feedback, e.g., vibration, which may be effective where sensory impairment is a key contributor to postural instability.

Physical Exercise Improves Heart Rate Variability in Patients with Type 2 Diabetes: A Systematic Review

PURPOSE OF REVIEW

The aim of the present systematic review is to provide an up-to-date analysis of the research on the effects of exercise programs on heart rate variability (HRV) in individuals with type 2 diabetes mellitus (T2DM). An electronic search of the literature (PubMed, PEDro and Web of Science) was performed. "HRV", "heart rate variability", "exercise", "physical" and "diabetes" were the terms used for article retrieval. Lastly, 15 articles were selected. PRISMA methodology was employed and data were extracted according to the PICOS approach.

RECENT FINDINGS

Although HRV is not routinely measured in the management of T2DM, it is an important measure due to its relation with mortality and diabetic neuropathy. Physical exercise has become a therapy for T2DM, because it improves physical fitness and functional capacity, enhances metabolic control and insulin sensitivity, reduces inflammatory markers and neuropathy symptoms and can increase the regenerative capacity of cutaneous axons, slowing or preventing neuropathy progression. However, it is not clear to what extent physical exercise can improve HRV in this population. Participation in the 15 selected studies was similar in men and women (48.01% men and 51.99% women). All the intervention programs included aerobic training, and it was complemented by strength training in four studies. Duration of physical exercise sessions ranged between 30 and 75 min, the frequency being between 2 and 7 days/week. Statistically significant improvements in groups with diabetes, relative to baseline, were observed in nine studies. More than 3 days per week of aerobic training, complemented by strength training, during at least 3 months seems to improve HRV in T2DM. Weekly frequency might be the most important factor to improve HRV. These aspects could help to design better programs based in scientific evidence, incorporating HRV as an important variable associated with diabetic neuropathy and mortality.

The Quest for more Research on Painful Diabetic Neuropathy

A 62-year-old diabetologist diagnosed himself to have diabetes type-2, with an HbA1c of 9.5. Five months after lifestyle intervention and a multi-drug approach, HbA1c was 6.3, systolic blood pressure was below 135mmHg and BMI reduced to 27. But he suffered from severe painful diabetic neuropathy. Therefore he decided to visit his friend, a famous neuroscientist at an even more famous university. He asked him several plain questions: 1. What is the natural course of painful diabetic neuropathy? 2. Why do I have, despite almost normalizing HbA1c, more problems than before? 3. Are you sure my problems are due to diabetes or should we do a nerve biopsy? 4. Are there imaging techniques helpful for the diagnosis of this diabetic complication, starting in the distal nerve endings of the foot and slowly moving ahead? 5. Can you suggest any drug, specific and effective, for relieving painful diabetic neuropathy? This review will use the experts' answers to the questions of the diabetologist, not only to give a summary of the current knowledge, but even more to highlight areas of research needed for improving the fate of patients with painful diabetic neuropathy. Based on the unknowns, which exceed the knowns in diabetic neuropathy, a quest for more public support of research is made.

Effects of Exercise on Neuropathy in Streptozotocin-Induced Diabetic Rats

Objective

To evaluate the effects of early regular exercise and to assess the electrophysiological and histopathological findings of the rat tail nerve in relation to the timing of exercise training for swimming exercise in rats with diabetic neuropathy.

Methods

We used 70 Sprague-Dawley male rats, and the experimental group comprised 60 rats, and the control group comprised 10 rats. Diabetes was induced by intraperitoneal injection of streptozotocin. Blood glucose concentrations were measured in tail vein blood samples. The experimental group was divided into 6 subgroups according to insulin treatment and swimming exercise: group 1, diabetic control; group 2, insulin treated; group 3, insulin untreated with early swimming exercise; group 4, insulin treated and early swimming exercise; group 5, insulin treated and late swimming exercise; and group 6, insulin untreated with late swimming exercise. Sensory and motor nerve conduction studies were performed weekly up to the 13th week using rat tail nerves. The effect on structural diabetic neuropathy was assessed by morphometry and ultrastructural examination of the rat tail nerve fiber at the 14th week.

Results

An exercise effect was observed in the insulin treated groups, but it was not observed in the insulin untreated groups. The sensory nerve conduction study in the rat tail revealed significantly prolonged latency and decreased amplitude in groups 1 and 6, and a further delay was observed in group 5 when compared to group 4. Decreased thickness of myelin was found in groups 1 and 6 through morphometry.

Conclusion

Early regular exercise programs in addition to conventional insulin treatment may retard the progression of diabetic peripheral neuropathy.

Dietary reversal of neuropathy in a murine model of prediabetes and metabolic syndrome

Patients with metabolic syndrome, which is defined as obesity, dyslipidemia, hypertension and impaired glucose tolerance (IGT), can develop the same macro- and microvascular complications as patients with type 2 diabetes, including peripheral neuropathy. In type 2 diabetes, glycemic control has little effect on the development and progression of peripheral neuropathy, suggesting that other metabolic syndrome components may contribute to the presence of neuropathy. A parallel phenomenon is observed in patients with prediabetes and metabolic syndrome, where improvement in weight and dyslipidemia more closely correlates with restoration of nerve function than improvement in glycemic status. The goal of the current study was to develop a murine model that resembles the human condition. We examined longitudinal parameters of metabolic syndrome and neuropathy development in six mouse strains/genotypes (BKS-wt, BKS-Leprdb/+ , B6-wt, B6-Leprdb/+ , BTBR-wt, and BTBR-Lepob/+ ) fed a 54% high-fat diet (HFD; from lard). All mice fed a HFD developed large-fiber neuropathy and IGT. Changes appeared early and consistently in B6-wt mice, and paralleled the onset of neuropathy. At 36 weeks, B6-wt mice displayed all components of the metabolic syndrome, including obesity, IGT, hyperinsulinemia, dyslipidemia and oxidized low density lipoproteins (oxLDLs). Dietary reversal, whereby B6-wt mice fed a HFD from 4-20 weeks of age were switched to standard chow for 4 weeks, completely normalized neuropathy, promoted weight loss, improved insulin sensitivity, and restored LDL cholesterol and oxLDL by 50% compared with levels in HFD control mice. This dietary reversal model provides the basis for mechanistic studies investigating peripheral nerve damage in the setting of metabolic syndrome, and ultimately the development of mechanism-based therapies for neuropathy.

Low-Dose Pulsatile Interleukin-6 As a Treatment Option for Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) remains one of the most common and serious complications of diabetes. Currently, pharmacological agents are limited to treating the pain associated with DPN, and do not address the underlying pathological mechanisms driving nerve damage, thus leaving a significant unmet medical need. Interestingly, research conducted using exercise as a treatment for DPN has revealed interleukin-6 (IL-6) signaling to be associated with many positive benefits such as enhanced blood flow and lipid metabolism, decreased chronic inflammation, and peripheral nerve fiber regeneration. IL-6, once known solely as a pro-inflammatory cytokine, is now understood to signal as a multifunctional cytokine, capable of eliciting both pro- and anti-inflammatory responses in a context-dependent fashion. IL-6 released from muscle in response to exercise signals as a myokine and as such has a unique kinetic profile, whereby levels are transiently elevated up to 100-fold and return to baseline levels within 4 h. Importantly, this kinetic profile is in stark contrast to long-term IL-6 elevation that is associated with pro-inflammatory states. Given exercise induces IL-6 myokine signaling, and exercise has been shown to elicit numerous beneficial effects for the treatment of DPN, a causal link has been suggested. Here, we discuss both the clinical and preclinical literature related to the application of IL-6 as a treatment strategy for DPN. In addition, we discuss how IL-6 may directly modulate Schwann and nerve cells to explore a mechanistic understanding of how this treatment elicits a neuroprotective and/or regenerative response. Collectively, studies suggest that IL-6, when administered in a low-dose pulsatile strategy to mimic the body's natural response to exercise, may prove to be an effective treatment for the protection and/or restoration of peripheral nerve function in DPN. This review highlights the studies supporting this assertion and provides rationale for continued investigation of IL-6 for the treatment of DPN.

Physical Training and Activity in People With Diabetic Peripheral Neuropathy: Paradigm Shift

Diabetic peripheral neuropathy (DPN) occurs in more than 50% of people with diabetes and is an important risk factor for skin breakdown, amputation, and reduced physical mobility (ie, walking and stair climbing). Although many beneficial effects of exercise for people with diabetes have been well established, few studies have examined whether exercise provides comparable benefits to people with DPN. Until recently, DPN was considered to be a contraindication for walking or any weight-bearing exercise because of concerns about injuring a person's insensitive feet. These guidelines were recently adjusted, however, after research demonstrated that weight-bearing activities do not increase the risk of foot ulcers in people who have DPN but do not have severe foot deformity. Emerging research has revealed positive adaptations in response to overload stress in these people, including evidence for peripheral neuroplasticity in animal models and early clinical trials. This perspective article reviews the evidence for peripheral neuroplasticity in animal models and early clinical trials, as well as adaptations of the integumentary system and the musculoskeletal system in response to overload stress. These positive adaptations are proposed to promote improved function in people with DPN and to foster the paradigm shift to including weight-bearing exercise for people with DPN. This perspective article also provides specific assessment and treatment recommendations for this important, high-risk group.