Neuropathy and impaired glucose tolerance: an updated review of the evidence

Asprosin, a novel therapeutic candidate for painful neuropathy: an experimental study in mice

Recent studies indicate presence of a strong link between adipokines and neuropathic pain. However, the effects of asprosin, a novel adipokine, on neuropathic pain have not been studied in animal models.Mouse models were employed to investigate the antinociceptive effectiveness of asprosin in the treatment of three types of neuropathic pain, with metabolic (streptozocin/STZ), toxic (oxaliplatin/OXA), and traumatic (sciatic nerve ligation/CCI [chronic constriction nerve injury]) etiologies, respectively. Changes in nociceptive behaviors were assessed relative to controls using thermal (the hot plate and cold plate tests, at 50 °C and 4 °C respectively) and mechanical pain (von Frey test) tests after intraperitoneal (i.p.) administration of asprosin (10 µg/kg) and gabapentin (50 mg/kg) in several times intervals. Besides, possible effect of asprosin on the motor coordination of mice was assessed with a rotarod test. Serum level of asprosin was quantified by ELISA.In neuropathic pain models (STZ, OXA, and CCI), asprosin administration significantly reduced both mechanical and thermal hypersensitivity, indicating that it exhibits a clear-cut antihypersensitivity effect in the analyzed neuropathic pain models. The most effective time of asprosin on pain threshold was observed 60 min after its injection. Also, asprosin displayed no notable effect on the motor activity. Asprosin levels were significantly lower in neuropathic pain compared to healthy group (p < 0.05).The results yielded by the present study suggest that asprosin exhibits an analgesic effect in the neuropathic pain models and may have clinical utility in alleviating chronic pain associated with disease and injury originating from peripheral structures.

Inflammatory Mechanisms in the Pathophysiology of Diabetic Peripheral Neuropathy (DN)-New Aspects

The pathogenesis of diabetic neuropathy is complex, and various pathogenic pathways have been proposed. A better understanding of the pathophysiology is warranted for developing novel therapeutic strategies. Here, we summarize recent evidence from experiments using animal models of type 1 and type 2 diabetes showing that low-grade intraneural inflammation is a facet of diabetic neuropathy. Our experimental data suggest that these mild inflammatory processes are a likely common terminal pathway in diabetic neuropathy associated with the degeneration of intraepidermal nerve fibers. In contrast to earlier reports claiming toxic effects of high-iron content, we found the opposite, i.e., nutritional iron deficiency caused low-grade inflammation and fiber degeneration while in normal or high non-heme iron nutrition no or only extremely mild inflammatory signs were identified in nerve tissue. Obesity and dyslipidemia also appear to trigger mild inflammation of peripheral nerves, associated with neuropathy even in the absence of overt diabetes mellitus. Our finding may be the experimental analog of recent observations identifying systemic proinflammatory activity in human sensorimotor diabetic neuropathy. In a rat model of type 1 diabetes, a mild neuropathy with inflammatory components could be induced by insulin treatment causing an abrupt reduction in HbA1c. This is in line with observations in patients with severe diabetes developing a small fiber neuropathy upon treatment-induced rapid HbA1c reduction. If the inflammatory pathogenesis could be further substantiated by data from human tissues and intervention studies, anti-inflammatory compounds with different modes of action may become candidates for the treatment or prevention of diabetic neuropathy.

Prevalence of peripheral neuropathy in pre-diabetes: a systematic review

There is growing evidence of excess peripheral neuropathy in pre-diabetes. We aimed to determine its prevalence, including the impact of diagnostic methodology on prevalence rates, through a systematic review conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. A comprehensive electronic bibliographic search was performed in MEDLINE, EMBASE, PubMed, Web of Science and the Cochrane Central Register of Controlled Trials from inception to June 1, 2020. Two reviewers independently selected studies, extracted data and assessed risk of bias. An evaluation was undertaken by method of neuropathy assessment. After screening 1784 abstracts and reviewing 84 full-text records, 29 studies (9351 participants) were included. There was a wide range of prevalence estimates (2%-77%, IQR: 6%-34%), but the majority of studies (n=21, 72%) reported a prevalence ≥10%. The three highest prevalence estimates of 77% (95% CI: 54% to 100%), 71% (95% CI: 55% to 88%) and 66% (95% CI: 53% to 78%) were reported using plantar thermography, multimodal quantitative sensory testing and nerve conduction tests, respectively. In general, studies evaluating small nerve fiber parameters yielded a higher prevalence of peripheral neuropathy. Due to a variety of study populations and methods of assessing neuropathy, there was marked heterogeneity in the prevalence estimates. Most studies reported a higher prevalence of peripheral neuropathy in pre-diabetes, primarily of a small nerve fiber origin, than would be expected in the background population. Given the marked rise in pre-diabetes, further consideration of targeting screening in this population is required. Development of risk-stratification tools may facilitate earlier interventions.

Statins and Neuropathic Pain: A Narrative Review

The frequently prescribed drug class of statins have pleiotropic effects and have been implicated in neuropathic pain syndromes. This narrative review examines studies of statin-induced neuropathic pain which to date have been conducted only in animal models. However, the pathophysiology of diabetic neuropathy in humans may shed some light on the etiology of neuropathic pain. Statins have exhibited a paradoxical effect in that statins appear to reduce neuropathic pain in animals but have been associated with neuropathic pain in humans. While there are certain postulated mechanisms offering elucidation as to how statins might be associated with neuropathic pain, there is, as the American Heart Association stated, to date no definitive association between statins and neuropathic pain. Statins are important drugs that reduce cardiovascular risk factors and should be prescribed to appropriate patients with these risk factors but some of this population is also at elevated risk for neuropathic pain from other causes.

Improvement in Neuropathy Outcomes With Normalizing HbA1c in Patients With Type 2 Diabetes

OBJECTIVE

To investigate the impact of normalizing HbA_1c by extensive HbA_1c control (EHC) on neuropathy outcome measures (NOMs), nephropathy, and retinopathy in type 2 diabetes.

RESEARCH DESIGN AND METHODS

Detailed clinical and neurological examinations were performed in two cohorts of 38 patients with uncontrolled type 2 diabetes (HbA_1c 9.6% [81.4 mmol/mol]) at baseline and after glycemic control (GC) with or without EHC by diet restriction and hypoglycemic agents over 4 years along with 48 control subjects with normal glucose tolerance (NGT) and 34 subjects with impaired glucose tolerance (IGT) only at baseline. EHC patients, control subjects, and subjects with IGT underwent oral glucose tolerance tests. Glycemic variability (GV) was evaluated by SD and coefficient of variation of monthly measured HbA_1c levels and casual plasma glucose.

RESULTS

In the EHC cohort, HbA_1c levels over 4.3 years and the last 2 years improved to 6.1% (43.2 mmol/mol) and 5.8% (39.9 mmol/mol) with 7.3 kg body wt reduction, and 50% and 28.9% of patients returned to IGT and NGT, respectively, at end point. Baseline neurophysiological and corneal nerve fiber (CNF) measures were impaired in patients. Normalized HbA_1c with EHC improved neurophysiological and CNF measures to be similar for those for IGT, while GC without EHC (mean HbA_1c level 7.0% [53.5 mmol/mol]) improved only vibration perception. The mean normalized HbA_1c levels by EHC determined NOM improvements. The high GV and baseline HbA_1c levels compromised NOMs. Albumin excretion rate significantly decreased, while retinopathy severity and frequency insignificantly worsened on EHC.

CONCLUSIONS

Normalizing HbA_1c in type 2 diabetes of short duration improves microvascular complications including neuropathy and nephropathy more effectively than standard GC but not retinopathy.

Cutaneous sensitivity in unilateral trans-tibial amputees

Aim

To examine tactile sensitivity in the leg and foot sole of below-knee amputees (diabetic n = 3, traumatic n = 1), and healthy control subjects (n = 4), and examine the association between sensation and balance.

Method

Vibration perception threshold (VPT; 3, 40, 250Hz) and monofilaments (MF) were used to examine vibration and light touch sensitivity on the intact limb, residual limb, and homologous locations on controls. A functional reach test was performed to assess functional balance.

Results

Tactile sensitivity was lower for diabetic amputee subjects compared to age matched controls for both VPT and MF; which was expected due to presence of diabetic peripheral neuropathy. In contrast, the traumatic amputee participant showed increased sensitivity for VPT at 40Hz and 250Hz vibration in both the intact and residual limbs compared to controls. Amputees with lower tactile sensitivity had shorter reach distances compared to those with higher sensitivity.

Conclusion

Changes in tactile sensitivity in the residual limb of trans-tibial amputees may have implications for the interaction between the amputee and the prosthetic device. The decreased skin sensitivity observed in the residual limb of subjects with diabetes is of concern as changes in skin sensitivity may be important in 1) identification/prevention of excessive pressure and 2) for functional stability. Interestingly, we saw increased residual limb skin sensitivity in the individual with the traumatic amputation. Although not measured directly in the present study, this increase in tactile sensitivity may be related to cortical reorganisation, which is known to occur following amputation, and would support similar findings observed in upper limb amputees.

Drug therapy for chronic idiopathic axonal polyneuropathy

BACKGROUND

Chronic idiopathic axonal polyneuropathy (CIAP) is an insidiously progressive sensory or sensorimotor polyneuropathy that affects elderly people. Although severe disability or handicap does not occur, CIAP reduces quality of life. CIAP is diagnosed in 10% to 25% of people referred for evaluation of polyneuropathy. There is a need to gather and review emerging evidence on treatments, as the number of people affected is likely to increase in ageing populations. This is an update of a review first published in 2004 and previously updated in 2006, 2008, 2011 and 2013.

OBJECTIVES

To assess the effects of drug therapy for chronic idiopathic axonal polyneuropathy for reducing disability and ameliorating neurological symptoms and associated impairments, and to assess any adverse effects of treatment.

SEARCH METHODS

In July 2016, we searched Cochrane Central Register of Controlled Trials and the Cochrane Database of Systematic Reviews in the Cochrane Library, MEDLINE, Embase, and the Web of Science. We searched two trials registries for ongoing trials. We also handsearched the reference lists of relevant articles, reviews and textbooks identified electronically, and we would have contacted authors and other experts in the field to identify additional studies if this seemed useful.

SELECTION CRITERIA

We sought all randomised or quasi-randomised (alternate or other systematic treatment allocation) trials that examined the effects of any drug therapy in people with CIAP at least one year after the onset of treatment. People with CIAP had to fulfil the following criteria: age 40 years or older, distal sensory or sensorimotor polyneuropathy, absence of systemic or other neurological disease, chronic clinical course not reaching a nadir in less than two months, exclusion of any recognised cause of the polyneuropathy by medical history taking, clinical or laboratory investigations, and electrophysiological studies in agreement with axonal polyneuropathy, without evidence of demyelinating features. The primary outcome was the proportion of participants with a significant improvement in disability. Secondary outcomes were change in the mean disability score, change in the proportion of participants who make use of walking aids, change in the mean Medical Research Council sum score, degree of pain relief and/or reduction of other positive sensory symptoms, change in the proportion of participants with pain or other positive sensory symptoms, and frequency of adverse effects.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed the results of the literature search and extracted details of trial methodology and outcome data of all potentially relevant trials.

MAIN RESULTS

We identified 39 studies and assessed them for possible inclusion in the review, but we excluded all of them because of insufficient quality or lack of relevance. We summarised evidence from non-randomised studies in the Discussion.

AUTHORS' CONCLUSIONS

Even though CIAP has been clearly described and delineated, no adequate randomised or quasi-randomised controlled clinical treatment trials have been performed. In their absence there is no proven efficacious drug therapy.

Corneal Confocal Microscopy Identifies Small-Fiber Neuropathy in Subjects With Impaired Glucose Tolerance Who Develop Type 2 Diabetes

OBJECTIVE

Impaired glucose tolerance (IGT) through to type 2 diabetes is thought to confer a continuum of risk for neuropathy. Identification of subjects at high risk of developing type 2 diabetes and, hence, worsening neuropathy would allow identification and risk stratification for more aggressive management.

RESEARCH DESIGN AND METHODS

Thirty subjects with IGT and 17 age-matched control subjects underwent an oral glucose tolerance test, assessment of neuropathic symptoms and deficits, quantitative sensory testing, neurophysiology, skin biopsy, and corneal confocal microscopy (CCM) to quantify corneal nerve fiber density (CNFD), branch density (CNBD), and fiber length (CNFL) at baseline and annually for 3 years.

RESULTS

Ten subjects who developed type 2 diabetes had a significantly lower CNFD (P = 0.003), CNBD (P = 0.04), and CNFL (P = 0.04) compared with control subjects at baseline and a further reduction in CNFL (P = 0.006), intraepidermal nerve fiber density (IENFD) (P = 0.02), and mean dendritic length (MDL) (P = 0.02) over 3 years. Fifteen subjects who remained IGT and 5 subjects who returned to normal glucose tolerance had no significant baseline abnormality on CCM or IENFD but had a lower MDL (P < 0.0001) compared with control subjects. The IGT subjects showed a significant decrease in IENFD (P = 0.02) but no change in MDL or CCM over 3 years. Those who returned to NGT showed an increase in CNFD (P = 0.05), CNBD (P = 0.04), and CNFL (P = 0.05), but a decrease in IENFD (P = 0.02), over 3 years.

CONCLUSIONS

CCM and skin biopsy detect a small-fiber neuropathy in subjects with IGT who develop type 2 diabetes and also show a dynamic worsening or improvement in corneal and intraepidermal nerve morphology in relation to change in glucose tolerance status.

Hyperglycemia is associated with relatively lower lean body mass in older adults

BACKGROUND/OBJECTIVES

Older adults with known diabetes are vulnerable to accelerated loss of lean body mass. However, the relationship of hyperglycemia per se with lean body mass is not fully understood. We sought to examine the independent relationship of hyperglycemia with relative lean body mass in older persons without a reported history of diabetes.

DESIGN

Cross-sectional nationally representative survey.

SETTING

United States.

PARTICIPANTS

We studied U.S. adults >50 years without known diabetes (n=5434) in the National Health and Nutrition Examination Survey (1999-2004).

MEASUREMENTS

In linear regression models, we studied the relationship of measured HbA1c (<5.0%, 5.0-5.4%, 5.5-5.9%, 6.0-6.4%, ≥6.5%) with percent lean body mass, measured by dual-energy x-ray absorptiometry, after accounting for potential confounders.

RESULTS

Among older U.S. men and women, progressively higher HbA1c was associated with relatively lower total, appendicular, and trunk percent lean mass, independent of demographics and height (all p<0.05). Accounting for physical activity, C-reactive protein, and diabetes-related comorbidities (heart disease, peripheral arterial disease, arthritis, neuropathy, hip fracture, amputation, cancer, pulmonary disease), undiagnosed diabetes (i.e. HbA1c ≥6.5%) versus reference (<5.0%) in both men and women was associated with lower total (-3.5±0.8% and -2.9±0.8%), appendicular (-1.8±0.5% and -1.2±0.4%), and trunk percent lean mass (-1.2±0.4% and -1.3±0.5%), respectively (all p<0.05). Persons at increased risk for diabetes (i.e. HbA1c 6.0-6.4%) also had significant decrements at these sites versus reference.

CONCLUSIONS

Hyperglycemia is associated with relatively lower lean mass in a nationally representative population of older adults without history of diabetes. Future longitudinal studies are needed to investigate the relationship of hyperglycemia with the accelerated decline of skeletal muscle mass in older persons.

Hyperglycemia predicts persistently lower muscle strength with aging

OBJECTIVE

Persons with diabetes have accelerated muscle loss compared with their counterparts. The relationship of hyperglycemia per se to declines in muscle function has not been explored yet has implications for developing appropriate intervention strategies to prevent muscle loss.

RESEARCH DESIGN AND METHODS

We examined 984 participants aged 25-96 years in the Baltimore Longitudinal Study of Aging (2003-2011) with HbA1c, knee extensor strength (isokinetic dynamometer), and lean body mass (DEXA) measured at baseline. Participants had repeated measurements up to 7.5 years later. Muscle quality was defined as knee extensor strength/leg lean mass. Participants were categorized by HbA1c quartile (<5.5, 5.5-5.79, 5.8-6.09, and ≥6.1% or <37, 37-40, 40-43, and ≥43 mmol/mol). Mixed-effects regression models were used to examine the regression of muscle outcomes on HbA1c.

RESULTS

Muscle strength and quality were significantly lower across HbA1c quartiles (both P < 0.001), without differences in muscle mass at baseline. Comparing highest versus lowest HbA1c quartiles and adjusting for age, race, sex, weight, and height, strength was significantly lower (-4.70 ± 2.30 N · m; P value trend = 0.02) and results were unchanged after adjustment for physical activity (P value trend = 0.045) but of borderline significance after additional adjustment for peripheral neuropathy (P value trend = 0.05). Adjusting for demographics, muscle quality was significantly lower (-0.32 ± 0.15 N · m/kg; P value trend = 0.02) in the highest versus lowest HbA1c quartiles, but differences were attenuated after adjusting for weight and height (-0.25 ± 0.15 N · m/kg; P value trend = 0.07). Muscle mass measures were similar across HbA1c quartiles.

CONCLUSIONS

Hyperglycemia is associated with persistently lower muscle strength with aging, but this effect may be mediated, at least in part, by peripheral neuropathy. Future studies should explore if better glycemic control can preserve muscle function in diabetes.

Elevated neurofilament light chain (NFL) mRNA levels in prediabetic peripheral neuropathy

Evidence suggests that peripheral nerve injury occurs during the early stages of disease with mild glycemic dysregulation. Two proteins, neuron-specific enolase (NSE) and neurofilament light chain (NFL), have been examined previously as possible markers of neuronal damage in the pathophysiology of neuropathies. Herein, we aimed to determine the potential value of circulatory NSE and NFL mRNA levels in prediabetic patients and in those with peripheral neuropathy. This prospective clinical study included 45 prediabetic patients and 30 age- and sex-matched controls. All prediabetic patients were assessed with respect to diabetes-related microvascular complications, such as peripheral neuropathy, retinopathy and nephropathy. mRNA levels of NSE and NFL were determined in the blood by real-time polymerase chain reaction. NSE mRNA levels were similar between prediabetic and control groups (p > 0.05), whereas NFL mRNA levels were significantly higher in prediabetics than in controls (p < 0.001). NSE mRNA levels did not significantly differ between prediabetic patients with and without peripheral neuropathy (p > 0.05), while NFL mRNA levels were significantly higher in prediabetics with peripheral neuropathy than in those without (p = 0.038). According to correlation analysis, NFL mRNA levels were positively correlated with the Douleur Neuropathique 4 questionnaire score in prediabetic patients (r = 0.302, p = 0.044). This is the first study to suggest blood NFL mRNA as a surrogate marker for early prediction of prediabetic peripheral neuropathy, while NSE mRNA levels may be of no diagnostic value in prediabetic patients.

Longitudinal changes in health-related quality of life in normal glucose tolerance, prediabetes and type 2 diabetes: results from the KORA S4/F4 cohort study

PURPOSE

The aim of this study was to examine how transition between normal glucose tolerance, prediabetes and diabetes over a 7 year period is associated with change in health-related quality of life (HRQL) in an elder German population-based cohort.

METHODS

We used data from 1,046 participants of the KORA S4/F4 cohort study aged 55-74 years at baseline. Based on an oral glucose tolerance test, prediabetes was defined as impaired fasting glucose and/or impaired glucose tolerance. HRQL was assessed with the SF-12 questionnaire. Using linear regression, we estimated mean change in HRQL over time, depending on glucose status at baseline and follow-up, adjusted by demographic and lifestyle variables.

RESULTS

Individuals progressing to prediabetes or diabetes experienced a greater loss in the physical component score than patients with persistent normal glucose tolerance (-2.31 and -7.44 vs. -1.08), but the difference was only significant for subjects converting to diabetes. Subjects with prediabetes at baseline and diabetes at follow-up had a significant loss in mental health compared to subjects with persistent prediabetes.

CONCLUSIONS

There is first evidence that worsening of glucose metabolism over time is associated with deteriorating HRQL, however, further and larger longitudinal studies are needed to confirm these findings.

Resveratrol protects DAergic PC12 cells from high glucose-induced oxidative stress and apoptosis: effect on p53 and GRP75 localization

Resveratrol (RESV), a polyphenolic natural compound, has long been acknowledged to have cardioprotective and antiinflammatory actions. Evidence suggests that RESV has antioxidant properties that reduce the formation of reactive oxygen species leading to oxidative stress and apoptotic death of dopaminergic (DAergic) neurons in Parkinson’s disease (PD). Recent literature has recognized hyperglycemia as a cause of oxidative stress reported to be harmful for the nervous system. In this context, our study aimed (a) to evaluate the effect of RESV against high glucose (HG)-induced oxidative stress in DAergic neurons, (b) to study the antiapoptotic properties of RESV in HG condition, and c) to analyze RESV’s ability to modulate p53 and GRP75, a p53 inactivator found to be under expressed in postmortem PD brains. Our results suggest that RESV protects DAergic neurons against HG-induced oxidative stress by diminishing cellular levels of superoxide anion. Moreover, RESV significantly reduces HG-induced apoptosis in DAergic cells by modulating DNA fragmentation and the expression of several genes implicated in the apoptotic cascade, such as Bax, Bcl-2, cleaved caspase-3, and cleaved PARP-1. RESV also prevents the pro-apoptotic increase of p53 in the nucleus induced by HG. Such data strengthens the correlation between hyperglycemia and neurodegeneration, while providing new insight on the high occurrence of PD in patients with diabetes. This study enlightens potent neuroprotective roles for RESV that should be considered as a nutritional recommendation for preventive and/or complementary therapies in controlling neurodegenerative complications in diabetes.

Phrenic neuropathy in diabetic and prediabetic patients without neuromuscular complaint

Neuropathy, one of the major reasons of morbidity in diabetes mellitus (DM), is associated with prediabetic conditions as well as DM. The present study aims to compare phrenic and peripheral nerves in prediabetic, diabetic patients and healthy controls. A total of 37 diabetic, 40 prediabetic patients and 18 healthy controls were enrolled in the study. All subjects underwent conventional sensory and motor nerve conduction studies. Bilateral phrenic and peripheric nerve conduction studies were performed. In both right and left phrenic nerves, the amplitudes were lower in prediabetic and diabetic patients than control subjects, respectively (p: 0.005 and p: 0.001). Both of the phrenic nerve conductions were altered similarly. The results of our study demonstrate that phrenic nerves are affected like peripheric nerves in prediabetic and diabetic patients. We suggest reminding phrenic neuropathy in newly onset respiratory failure in diabetic and prediabetic patients.

Chronic idiopathic axonal polyneuropathy is associated with the metabolic syndrome

OBJECTIVE

This study aims to investigate the association between chronic idiopathic axonal polyneuropathy (CIAP) and the metabolic syndrome or its individual components.

RESEARCH DESIGN AND METHODS

A total of 249 patients with CIAP and 709 controls underwent fasting laboratory studies, and blood pressure and waist circumference were measured. The metabolic syndrome was diagnosed if three or more of the following Adult Treatment Panel III criteria were present: impaired fasting glucose, hypertension, abdominal obesity, reduced HDL cholesterol, and hypertriglyceridemia. Subgroup analysis was performed for patients with a painful predominantly sensory CIAP, because this phenotype is most similar to diabetic polyneuropathy. Statistical analysis was performed with adjustment for age and gender.

RESULTS

Fifty-five percent of all patients fulfilled the metabolic syndrome criteria compared with 34% of controls (odds ratio 2.2 [95% CI 1.7-3.0]). Multivariate analysis shows hypertension (2.9 [1.7-4.9]) and abdominal obesity (3.3 [2.4-4.6]) to be significantly more prevalent in patients than in controls. Of the patients classified as having a painful predominantly sensory CIAP, 62% fulfilled the metabolic syndrome criteria (3.1 [2.0-4.8]). In this subgroup, hypertension and abdominal obesity also were significantly more prevalent compared with controls.

CONCLUSIONS

Abdominal obesity and hypertension seem to be the most consistent contributing components of the metabolic syndrome in patients with CIAP. Evaluation and appropriate treatment of these risk factors in patients with CIAP would be advocated.

Autonomic test by EZSCAN in the screening for prediabetes and diabetes

BACKGROUND

Autonomic neuropathy is common in diabetics and may occur in prediabetes. A new and noninvasive autonomic test-EZSCAN evaluates sudomotor function precisely. No generally accepted EZSCAN thresholds to screen for prediabetes and diabetes have been defined.

METHODOLOGY AND PRINCIPAL FINDINGS

Cross-sectional study of 5, 824 Chinese adults aged 40 and older was conducted in Shanghai, China. We used EZSCAN to evaluate autonomic function in different glucose status and screen for prediabetes and diabetes. The prevalence of prediabetes and diabetes were 21.9% and 17.5% respectively. Compared with the lowest quintile, the highest quintile of EZSCAN value had odds ratios for having dysglycemia (prediabetes or diabetes) of 2.08 (95% CI 1.67-2.58) in total population, 2.89 (95% CI 2.06-4.05) in men and 1.70 (95% CI 1.28-2.25) in women after adjustment for confounding factors. EZSCAN value improved the areas under ROC curve for detection of dysglycemia or diabetes beyond the contribution of conventional risk factors by 0.8% and 12.9%. The cut-off point of EZSCAN value higher than 30% provided reasonable sensitivities (70.3-83.7%) to detect dysglycemia not only in total population regardless of sex but also in individuals with high risk of developing diabetes.

CONCLUSIONS AND SIGNIFICANCE

EZSCAN value higher than 30% indicate an increased risk of prevalent prediabetes and diabetes, suggesting that subjects with EZSCAN ≥30% should be further evaluated by oral glucose tolerance test. The improvement of EZSCAN for diabetes detection was still of limited clinical relevance. Thus the clinical application value of EZSCAN is needed to be explored in future studies.

Pre-diabetes, metabolic syndrome, and cardiovascular risk

Pre-diabetes represents an elevation of plasma glucose above the normal range but below that of clinical diabetes. Pre-diabetes can be identified as either impaired fasting glucose (IFG) or impaired glucose tolerance (IGT). The latter is detected by oral glucose tolerance testing. Both IFG and IGT are risk factors for type 2 diabetes, and risk is even greater when IFG and IGT occur together. Pre-diabetes commonly associates with the metabolic syndrome. Both in turn are closely associated with obesity. The mechanisms whereby obesity predisposes to pre-diabetes and metabolic syndrome are incompletely understood but likely have a common metabolic soil. Insulin resistance is a common factor; systemic inflammation engendered by obesity may be another. Pre-diabetes has only a minor impact on microvascular disease; glucose-lowering drugs can delay conversion to diabetes, but whether in the long run the drug approach will delay development of microvascular disease is in dispute. To date, the drug approach to prevention of microvascular disease starting with pre-diabetes has not been evaluated. Pre-diabetes carries some predictive power for macrovascular disease, but most of this association appears to be mediated through the metabolic syndrome. The preferred clinical approach to cardiovascular prevention is to treat all the metabolic risk factors. For both pre-diabetes and metabolic syndrome, the desirable approach is lifestyle intervention, especially weight reduction and physical activity. When drug therapy is contemplated and when the metabolic syndrome is present, the primary consideration is prevention of cardiovascular disease. The major targets are elevations of cholesterol and blood pressure.

Impaired glycemia and diabetic polyneuropathy: the OC IG Survey

OBJECTIVE

To test whether diabetic polyneuropathies (DPNs), retinopathy, or nephropathy is more prevalent in subjects with impaired glycemia (IG) (abnormality of impaired fasting glucose [IFG], impaired glucose tolerance [IGT], or impaired HbA(1c) [IA1C]) than in healthy subjects (non-IG).

RESEARCH DESIGN AND METHODS

Matched IG and non-IG volunteers were randomly identified from population-based diagnostic and laboratory registries, restudied, and reclassified as non-IG (n = 150), IG (n = 174), or new diabetes (n = 218).

RESULTS

Frequency (%) of DPN in non-IG, IG, and new diabetes was 3 (2.0%), 3 (1.7%), and 17 (7.8%) narrowly defined (no other cause for polyneuropathy) and 19 (12.7%), 22 (12.6%), and 38 (17.4%) broadly defined. Mean and frequency distribution of composite scores of nerve conduction and quantitative sensation tests were not significantly different between IG and non-IG but were worse in new diabetes. Frequency of retinopathy and nephropathy was significantly increased only in new diabetes. In secondary analysis, small but significant increases in retinopathy and nephropathy were found in IGT, IFG, and IGT combined groups.

CONCLUSIONS

In population studies of Olmsted County, Minnesota, inhabitants, prevalence of typical DPN, retinopathy, and nephropathy was significantly increased only in subjects with new diabetes-not in subjects with IG as defined by American Diabetes Association (ADA) criteria of abnormality of IFG, IGT, or IA1C. For atypical DPN, such an increase was not observed even in subjects with new diabetes. In medical practice, explanations other than IG should be sought for patients with atypical DPN (chronic idiopathic axonal polyneuropathy) who have IG.

Electrodiagnosis of peripheral neuropathy

Electrodiagnostic studies are an important component of the evaluation of patients with suspected peripheral nerve disorders. The pattern of findings and the features that are seen on the motor and sensory nerve conduction studies and needle electromyography can help to identify the type of neuropathy, define the underlying pathophysiology (axonal or demyelinating), and ultimately help to narrow the list of possible causes. This article reviews the electrodiagnostic approach to and interpretation of findings in patients with peripheral neuropathies.

Glucose and insulin measurements from the oral glucose tolerance test and relationship to muscle mass

BACKGROUND

Diabetes is associated with decreased muscle mass. The effect of higher levels of glucose and insulin on muscle mass has not been studied in individuals without diabetes. We sought to determine the relationship of insulin and glucose measurements from the oral glucose tolerance test (OGTT) with muscle mass in persons without diabetes.

METHODS

We analyzed data from 587 participants in the Baltimore Longitudinal Study of Aging (mean age 67.3 years, range 26-95 years) without diabetes who underwent a 2-hour OGTT, including glucose and insulin measurements taken every 20 minutes and assessment of midthigh muscle cross-sectional area by computed tomography, taken as a proxy measure of muscle mass. Linear regression models and Bayesian model averaging were used to explore the independent cross-sectional association of various OGTT-derived measures and midthigh muscle cross-sectional area, independent of confounders.

RESULTS

Individually, fasting glucose, fasting insulin, OGTT glucose (40, 60, 80, 100, and 120 minutes), OGTT insulin (20, 60, 80, 100, and 120 minutes), homeostasis model assessment of insulin resistance, integrated glucose area, and integrated insulin area were inversely associated, and the Matsuda index was positively associated, with the midthigh muscle cross-sectional area (standardized to body weight) after adjustment for age, sex, race, height, physical activity, and peroneal motor nerve conduction velocity (all ps <.05). When considered together, the Matsuda index and fasting glucose were the strongest predictors of lower midthigh muscle cross-sectional area after covariate adjustment.

CONCLUSIONS

Higher fasting and OGTT values of both glucose and insulin are associated with lower muscle mass. Longitudinal studies are needed to verify whether individuals free of diabetes that have higher glucose and insulin during an OGTT are at risk for accelerated muscle mass decline with aging.

Dyslipidaemia in chronic acquired distal axonal polyneuropathy

The link between hypertriglyceridaemia (HTG) and/or hypercholesterolaemia (HCL) and neuropathy is uncertain. We retrospectively reviewed records of 100 consecutive patients investigated for acquired chronic axonal distal polyneuropathy of unknown cause. Findings were compared with those of 102 consecutive controls. Patients with idiopathic neuropathy were subsequently compared with age- and gender-matched controls. There were more neuropathy patients than controls with HCL, defined as cholesterol levels >5 mmol/L (63 vs. 45.1%; p = 0.011). Neuropathy patients also had higher cholesterol levels than controls (p = 0.04). Cholesterol-lowering drug usage was similar in both groups. HTG (defined as >2 mmol/L) and triglyceride levels were comparable in both groups. HTG ranged from 2.1-4.2 mmol/L in neuropathy patients. A cause for neuropathy was identified in 59 patients. Thirty-one had impaired glucose metabolism. Forty-one had idiopathic neuropathy. No link was demonstrated between idiopathic neuropathy or painful idiopathic neuropathy, and HTG/HCL. Mean triglyceride and cholesterol levels in patients with idiopathic neuropathy were comparable to those of controls. HTG was significantly more common (p = 0.027), and triglyceride levels significantly higher (p = 0.005) in patients with neuropathy due to diabetes/impaired glucose tolerance (IGT)/alcoholism, than in patients with neuropathy of any other cause. These results suggest HCL >5 mmol/L may represent a cofactor contributing to presence of neuropathy irrespective of the underlying cause. They on the other hand do not support mild/moderate HTG as an independent cause of neuropathy. HTG is common in patients with neuropathy associated with diabetes/IGT/chronic alcoholism, where it may play a role in peripheral nerve damage. As previously reported, IGT was in our cohort frequent, present in one case in three, in the absence of another identifiable aetiology.