The effect of 8 years of strict glycaemic control on peripheral nerve function in IDDM patients: the Oslo Study

A Cross-Sectional Study of Electrophysiological Changes Occurring in Type II Diabetes Mellitus

Background

Diabetes is a long-term metabolic condition that results in high blood sugar levels from either reduced insulin production or diminished tissue sensitivity to insulin. Peripheral neuropathy is the most frequent consequence of diabetes. In this research project, with the aid of neurophysiological measures, we conducted a cross-sectional study to examine the impact of glycemic management on the physiological functioning of nerves, regardless of the duration of diabetes.

Objectives

The main objective of the study was to investigate the association between the degree of glycemic control and the severity of neurological changes. The study also aimed to clarify whether glycemic management, independent of the duration of diabetes, acts as an independent risk factor for the emergence of diabetic neuropathy.

Methodology

A total of 150 type 2 diabetic patients visiting the diabetic outpatient department were included in the study. The patients were divided into two groups: group A consisted of 90 subjects with HbA1c levels <10 and group B comprised 60 subjects with HbA1c levels >10. In the neurophysiology lab, an electrodiagnostic exam was conducted on the sensory (sural nerve) and motor (tibial nerve) parameters. Data on the neurophysiological parameters of the two groups were analyzed and compared.

Results

When the neurophysiological parameters of the two groups (group A having HbA1c <10 and group B having HbA1c >10) were analyzed, it was observed that group B had lower conduction velocity (CV) and amplitude potential than group A, with a significant statistical difference (p<0.05). It was also observed that sensory parameters were more affected than motor parameters.

Conclusion

Based on our findings, glycemic control is related to the severity of neuropathic changes.

Mechanistic approach towards diabetic neuropathy screening techniques and future challenges: A review

Diabetic neuropathy, also called peripheral diabetic neuropathy (PDN), is among the most significant diabetes health consequences, alongside diabetic nephropathy, diabetic cardiomyopathy and diabetic retinopathy. Diabetic neuropathy is the existence of signs and indications of peripheral nerve damage in patients with diabetes after other causes have been governed out. Diabetic neuropathy is a painful and severe complication of diabetes that affects roughly 20% of people. The development of diabetic neuropathy is regulated by blood arteries that nourish the peripheral nerves and metabolic problems such as increased stimulation of polyol pathway, loss of myo-inositol and enhanced non-enzymatic glycation. It's divided into four types based on where neurons are most affected: autonomic, peripheral, proximal, and focal, with each kind presenting different symptoms like numbing, gastrointestinal disorders, and heart concerns. Pharmacotherapy for neuropathic pain is complex and for many patients, effective treatment is lacking; as a result, scientific proof recommendations are crucial. As a result, the current demand is to give the most vital medications or combinations of drugs that work directly on the nerves to help diabetic neuropathy patients feel less pain without causing any adverse effects. In diabetic neuropathy research, animal models are ubiquitous, with rats and mice being the most typically chosen for various reasons. This review covers the epidemiology, clinical features, pathology, clinical symptom, mechanism of diabetic neuropathy development, diagnosis, screening models of animals, diabetic neuropathy pharmacotherapy.

Specialized pro-resolving mediators in diabetes: novel therapeutic strategies

Diabetes mellitus (DM) is an important metabolic disorder characterized by persistent hyperglycemia resulting from inadequate production and secretion of insulin, impaired insulin action, or a combination of both. Genetic disorders and insulin receptor disorders, environmental factors, lifestyle choices and toxins are key factors that contribute to DM. While it is often referred to as a metabolic disorder, modern lifestyle choices and nutrient excess induce a state of systemic chronic inflammation that results in the increased production and secretion of inflammatory cytokines that contribute to DM. It is chronic hyperglycemia and the low-grade chronic-inflammation that underlies the development of microvascular and macrovascular complications leading to damage in a number of tissues and organs, including eyes, vasculature, heart, nerves, and kidneys. Improvements in the management of risk factors have been beneficial, including focus on intensified glycemic control, but most current approaches only slow disease progression. Even with recent studies employing SGLT2 inhibitors demonstrating protection against cardiovascular and kidney diseases, kidney function continues to decline in people with established diabetic kidney disease (DKD). Despite the many advances and a greatly improved understanding of the pathobiology of diabetes and its complications, there remains a major unmet need for more effective therapeutics to prevent and reverse the chronic complications of diabetes. More recently, there has been growing interest in the use of specialised pro-resolving mediators (SPMs) as an exciting therapeutic strategy to target diabetes and the chronic complications of diabetes.

A comparative double-blind randomized study on the effectiveness of Duloxetine and Gabapentin on painful diabetic peripheral polyneuropathy

Background: The most common cause of polyneuropathy is diabetes mellitus. Neuropathic pain is seen in 26% of diabetic population. Therapeutic techniques for this disease can become challenging. Method: This study was a prospective comparative double-blind randomized study which was conducted during an eight-week period. Totally, 104 painful diabetic peripheral polyneuropathy (PDPP) patients who had a minimum Visual Analog Scale (VAS) of 40 millimeters, received no pain-controlling medication, and had no other severe disease at its final stage were randomly assigned to two groups (n=52) through the four block method. One group received Duloxetine and the other received Gabapentin. The effectiveness was measured through primary effectiveness (VAS scale) and secondary effectiveness (Sleep Interference Score, and Clinical Global Impression of Change (CGIC)). Medication compliance was assessed by enumerating the number of patients who refused treatment because of side effects. The Fisher's exact T-test and ANOVA were used for data analysis. This study was approved by the Ethics Committee of Jundishapur, University of Medical sciences Ahvaz, Iran, under reference number: IR.AJUMS.REC.1395.78. In addition, this study was registered and approved in the Iranian Registry of Clinical Trials (IRCT ID: IRCT20161023030455N2) (http://irct.ir/). Results: VAS, Sleep Interference Score, and CGIC were significantly improved (P<0.05) through time in both groups, [For GBP: VAS^Baseline=64±20.03, VAS^week1=55.32±18.76, VAS^week4=44.68±15.82, VAS^week8=39.43±14.32; For DLX: VAS^Base-line=62±21.18, VAS^week1=58.76±20.37, VAS^week4=45.84±16.21, VAS^week8=36.78±15.62] while a significant difference between the two groups was not observed (P<0.05). However, such significant improvements were not observed in the Duloxetine group at the end of the first week (P=674). Improvement in Sleep Interference Score and CGIC were similar to the results for the VAS scale. Side effects in the Duloxetine group (n=2) compared to the Gabapentin group (n=9) were significantly less (P<0.001). As a result, medication acceptance in the Duloxetine group (n=47) was significantly better than the Gabapentin (n=41) group (P<0.001). Conclusion: Both Duloxetine and Gabapentin are effective for the treatment of PDPP. On the one hand, Gabapentin shows the effect earlier while has more side effects. Conversely, Duloxetine has better medication compliance. Trial registration: The method of this study was approved by the Ethics Committee of Jundishapur University of Medical Sciences, Ahvaz, Iran, under reference number: IR.AJUMS.REC.1395.78. In addition, this study was registered and approved in the Iranian Registry of Clinical Trials (IRCT ID: IRCT20161023030455N2) (http://irct.ir/).

[Diabetic neuropathy and diabetic foot syndrome (Update 2019)]

These are the guidelines for diagnosis and treatment of diabetic neuropathy and diabetic foot. Diabetic neuropathy comprises a number of mono- and polyneuropathies, plexopathies, radiculopathies and autonomic neuropathy.The position statement summarizes characteristic clinical symptoms and techniques for diagnostic assessment of diabetic neuropathy, including the complex situation of the diabetic foot syndrome. Recommendations for the therapeutic management of diabetic neuropathy, especially for the control of pain in sensorimotor neuropathy, are provided. The needs to prevent and treat diabetic foot syndrome are summarized.

HbA1C Variability Is Strongly Associated With the Severity of Peripheral Neuropathy in Patients With Type 2 Diabetes

Variability in HbA1c is associated with a higher risk of cardiovascular disease and microvascular complications in patients with type 2 diabetes. The present study evaluated the severity of somatic nerve dysfunction at different stages of chronic glycemic impairment, and its correlation with different cardio-metabolic parameters. The study was conducted on 223 patients with type 2 diabetes. We calculated the intrapersonal mean, standard deviation (SD), and coefficient of variation of HbA1c for each patient using all measurements obtained for 3 years prior to the study. Patients were divided into quartiles according to the SD of HbA1c, and we constructed composite scores of nerve conduction as the severity of peripheral neuropathy. Linear regression analysis was performed to evaluate the influence of independent variables on mean composite scores. Those with higher SD-HbA1c had a higher body mass index, mean and index HbA1c, triglyceride and uric acid level, urinary albumin excretion and albumin-creatinine ratio, proportion of insulin therapy, and prevalence of hypertension as the underlying diseases, but lower estimate glomerular filtration rate (eGFR). In addition, those with higher SD-HbA1c showed lower amplitudes and reduced motor nerve conduction velocity in tested nerves, and lower sensory nerve conduction velocity in the sural nerve. Furthermore, those with higher SD-HbA1c had higher composite scores of low extremities. Multiple linear regression analysis revealed that diabetes duration, SD-HbA1c, and eGFR were independently associated with mean composite scores. Based on our results, HbA1c variability plus chronic glycemic impairment is strongly associated with the severity of peripheral neuropathy in patients with type 2 diabetes. Aggressively control blood glucose to an acceptable range and avoid blood glucose fluctuations by individualized treatment to prevent further nerve damage.

Explanations for less small fibre neuropathy in South Asian versus European subjects with type 2 diabetes in the UK

BACKGROUND

Low foot ulcer risk in South Asian, compared with European, people with type 2 diabetes in the UK has been attributed to their lower levels of neuropathy. We have undertaken a detailed study of corneal nerve morphology and neuropathy risk factors, to establish the basis of preserved small nerve fibre function in South Asians versus Europeans.

METHODS

In a cross-sectional, population-based study, age- and sex-matched South Asians (n = 77) and Europeans (n = 78) with type 2 diabetes underwent neuropathy assessment using corneal confocal microscopy, symptoms, signs, quantitative sensory testing, electrophysiology and autonomic function testing. Multivariable linear regression analyses determined factors accounting for ethnic differences in small fibre damage.

RESULTS

Corneal nerve fibre length (22.0 ± 7.9 vs. 19.3 ± 6.3 mm/mm2 ; P = 0.037), corneal nerve branch density (geometric mean (range): 60.0 (4.7-246.2) vs. 46.0 (3.1-129.2) no./mm2 ; P = 0.021) and heart rate variability (geometric mean (range): 7.9 (1.4-27.7) vs. 6.5 (1.5-22.0); P = 0.044), were significantly higher in South Asians vs. Europeans. All other neuropathy measures did not differ, except for better sural nerve amplitude in South Asians (geometric mean (range): 10.0 (1.3-43.0) vs. 7.2 (1.0-30.0); P = 0.006). Variables with the greatest impact on attenuating the P value for age- and HbA1C -adjusted ethnic difference in corneal nerve fibre length (P = 0.032) were pack-years smoked (P = 0.13), BMI (P = 0.062) and triglyceride levels (P = 0.062).

CONCLUSIONS

South Asians have better preserved small nerve fibre integrity than equivalent Europeans; furthermore, classic, modifiable risk factors for coronary heart disease are the main contributors to these ethnic differences. We suggest that improved autonomic neurogenic control of cutaneous blood flow in Asians may contribute to their protection against foot ulcers.

Mediators of diabetic neuropathy: is hyperglycemia the only culprit?

PURPOSE OF REVIEW

Diabetic peripheral neuropathy (DPN) is a disabling, highly prevalent complication of both type 1 and type 2 diabetes mellitus (T1DM and T2DM). Large clinical studies support the concept that, in addition to hyperglycemia, components of the metabolic syndrome (MetS) may underlie the pathogenesis of DPN, especially in T2DM. This review will present the evidence supporting the MetS and its individual components as potential causal factors for the development of neuropathy.

RECENT FINDINGS

In addition to poor glycemic control and duration of diabetes, components of MetS such as dyslipidemia, obesity, and hypertension may have an important impact on the prevalence of DPN. Obesity and prediabetes have the most data to support their role in neuropathy, whereas hypertension and dyslipidemia have more mixed results. Nonmetabolic factors, such as genetic susceptibility, age, height, sex, smoking, and alcohol, have also been highlighted as potential risk factors in peripheral neuropathy, although the exact contribution of these factors to DPN remains unknown.

SUMMARY

DPN is a chronic and disabling disease, and the accurate identification and modification of DPN risk factors is important for clinical management. Recent data support a role for components of the MetS and other risk factors in the development of DPN, offering novel targets beyond hyperglycemia for therapeutic development.

Small and large fiber neuropathy in those with type 1 and type 2 diabetes: a 5-year follow-up study

The purpose of this study was to evaluate progression of diabetic polyneuropathy and differences in the spectrum and evolution of large- and small-fiber involvement in patients with diabetes type 1 and 2 over 5 years. Fifty-nine patients (35 type 1 and 24 type 2) were included. Nerve conduction studies (NCS), quantitative sensory testing, skin biopsy for quantification of intraepidermal nerve fiber density (IENFD), symptom scoring and clinical evaluations were performed. Z-scores were calculated to adjust for the physiologic effects of age and height/gender. Neuropathic symptoms were not significantly more frequent in type 2 than in type 1 diabetic patients at follow-up (54% vs. 37%). The overall mean NCS Z-score remained within the normal range, but there was a small significant decline after 5 years in both groups: type 1 (p = 0.004) and type 2 (p = 0.02). Mean IENFD Z-scores changed from normal to abnormal in both groups, but only significantly in those with type 2 diabetes (reduction from 7.9 ± 4.8 to 4.3 ± 2.8 fibers/mm, p = 0.006). Cold perception threshold became more abnormal only in those with type 2 diabetes (p = 0.049). There was a minimal progression of large fiber neuropathy in both groups. Reduction of small fibers predominated and progressed more rapidly in those with type 2 diabetes.

Principles and frequency of self-adjustment of insulin dose in people with diabetes mellitus type 1 and correlation with markers of metabolic control

OBJECTIVE

Insulin dose self-adjustment (ISA) to different blood glucose levels, carbohydrate intake, exercise or illness is a core element of structured education programmes for people with diabetes mellitus type 1 (DM1). The aim of this study was to register the patients' current principles and frequency of ISA and to check the ability for correct adjustments.

RESEARCH DESIGN AND METHODS

117 people with DM1 (mean HbA1c 7.1%, diabetes duration 24y) were interviewed in a tertiary care centre. The number of ISA was drawn from the last 28days of the patients' diary. The ability to find the correct insulin dose was assessed using five different calculation examples. All patients had participated in a structured education programme.

RESULTS

Mean frequency of ISA was 72.1±29.4 per 28days. ISA by adjustment rules was used in 48% (56/117) and by personal experience or feeling in 44% (52/117). Patients adjusting by feeling were older, did less ISA and had lower social status. There were no differences in HbA1c (feeling 7.2±0.8 vs. rules 7.0±0.9, p=0.403), non severe hypoglycaemia (feeling 1.7±1.8 vs. rules 1.9±1.9, p=0.132) and comprehensibility of ISA between both groups. Overall, the participants answered on average 2.8±2.3 of the five calculation examples correctly.

CONCLUSIONS

Although all people were trained to use a factor for correction for ISA in case of high premeal blood glucose levels, only half of the patients adjusted their insulin dosage using the complex rules from the treatment and education programme. Patients, who performed their ISA based upon feeling, did not show worse metabolic control.

Targeting intensive versus conventional glycaemic control for type 1 diabetes mellitus: a systematic review with meta-analyses and trial sequential analyses of randomised clinical trials

OBJECTIVE

To assess the benefits and harms of targeting intensive versus conventional glycaemic control in patients with type 1 diabetes mellitus.

DESIGN

A systematic review with meta-analyses and trial sequential analyses of randomised clinical trials.

DATA SOURCES

The Cochrane Library, MEDLINE, EMBASE, Science Citation Index Expanded and LILACS to January 2013.

STUDY SELECTION

Randomised clinical trials that prespecified different targets of glycaemic control in participants at any age with type 1 diabetes mellitus were included.

DATA EXTRACTION

Two authors independently assessed studies for inclusion and extracted data.

RESULTS

18 randomised clinical trials included 2254 participants with type 1 diabetes mellitus. All trials had high risk of bias. There was no statistically significant effect of targeting intensive glycaemic control on all-cause mortality (risk ratio 1.16, 95% CI 0.65 to 2.08) or cardiovascular mortality (0.49, 0.19 to 1.24). Targeting intensive glycaemic control reduced the relative risks for the composite macrovascular outcome (0.63, 0.41 to 0.96; p=0.03), and nephropathy (0.37, 0.27 to 0.50; p<0.00001. The effect estimates of retinopathy, ketoacidosis and retinal photocoagulation were not consistently statistically significant between random and fixed effects models. The risk of severe hypoglycaemia was significantly increased with intensive glycaemic targets (1.40, 1.01 to 1.94). Trial sequential analyses showed that the amount of data needed to demonstrate a relative risk reduction of 10% were, in general, inadequate.

CONCLUSIONS

There was no significant effect towards improved all-cause mortality when targeting intensive glycaemic control compared with conventional glycaemic control. However, there may be beneficial effects of targeting intensive glycaemic control on the composite macrovascular outcome and on nephropathy, and detrimental effects on severe hypoglycaemia. Notably, the data for retinopathy and ketoacidosis were inconsistent. There was a severe lack of reporting on patient relevant outcomes, and all trials had poor bias control.

Intensive glucose control versus conventional glucose control for type 1 diabetes mellitus

BACKGROUND

Clinical guidelines differ regarding their recommended blood glucose targets for patients with type 1 diabetes and recent studies on patients with type 2 diabetes suggest that aiming at very low targets can increase the risk of mortality.

OBJECTIVES

To assess the effects of intensive versus conventional glycaemic targets in patients with type 1 diabetes in terms of long-term complications and determine whether very low, near normoglycaemic values are of additional benefit.

SEARCH METHODS

A systematic literature search was performed in the databases The Cochrane Library, MEDLINE and EMBASE. The date of the last search was December 2012 for all databases.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) that had defined different glycaemic targets in the treatment arms, studied patients with type 1 diabetes, and had a follow-up duration of at least one year.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data, assessed studies for risk of bias, with differences resolved by consensus. Overall study quality was evaluated by the 'Grading of Recommendations Assessment, Development, and Evaluation' (GRADE) system. Random-effects models were used for the main analyses and the results are presented as risk ratios (RR) with 95% confidence intervals (CI) for dichotomous outcomes.

MAIN RESULTS

We identified 12 trials that fulfilled the inclusion criteria, including a total of 2230 patients. The patient populations varied widely across studies with one study only including children, one study only including patients after a kidney transplant, one study with newly diagnosed adult patients, and several studies where patients had retinopathy or microalbuminuria at baseline. The mean follow-up duration across studies varied between one and 6.5 years. The majority of the studies were carried out in the 1980s and all trials took place in Europe or North America. Due to the nature of the intervention, none of the studies could be carried out in a blinded fashion so that the risk of performance bias, especially for subjective outcomes such as hypoglycaemia, was present in all of the studies. Fifty per cent of the studies were judged to have a high risk of bias in at least one other category.Under intensive glucose control, the risk of developing microvascular complications was reduced compared to conventional treatment for a) retinopathy: 23/371 (6.2%) versus 92/397 (23.2%); RR 0.27 (95% CI 0.18 to 0.42); P < 0.00001; 768 participants; 2 trials; high quality evidence; b) nephropathy: 119/732 (16.3%) versus 211/743 (28.4%); RR 0.56 (95% CI 0.46 to 0.68); P < 0.00001; 1475 participants; 3 trials; moderate quality evidence; c) neuropathy: 29/586 (4.9%) versus 86/617 (13.9%); RR 0.35 (95% CI 0.23 to 0.53); P < 0.00001; 1203 participants; 3 trials; high quality evidence. Regarding the progression of these complications after manifestation, the effect was weaker (retinopathy) or possibly not existent (nephropathy: RR 0.79 (95% CI 0.37 to 1.70); P = 0.55; 179 participants with microalbuminuria; 3 trials; very low quality evidence); no adequate data were available regarding the progression of neuropathy. For retinopathy, intensive glucose control reduced the risk of progression in studies with a follow-up duration of at least two years (85/366 (23.2%) versus 154/398 (38.7%); RR 0.61 (95% CI 0.49 to 0.76); P < 0.0001; 764 participants; 2 trials; moderate quality evidence), while we found evidence for an initial worsening of retinopathy after only one year of intensive glucose control (17/49 (34.7%) versus 7/47 (14.9%); RR 2.32 (95% CI 1.16 to 4.63); P = 0.02; 96 participants; 2 trials; low quality evidence).Major macrovascular outcomes (stroke and myocardial infarction) occurred very rarely, and no firm evidence could be established regarding these outcome measures (low quality evidence).We found that intensive glucose control increased the risk for severe hypoglycaemia, however the results were heterogeneous and only the 'Diabetes Complications Clinical Trial' (DCCT) showed a clear increase in severe hypoglycaemic episodes under intensive treatment. A subgroup analysis according to the baseline haemoglobin A1c (HbA1c) of participants in the trials (low quality evidence) suggests that the risk of hypoglycaemia is possibly only increased for patients who started with relatively low HbA1c values (< 9.0%). Several of the included studies also showed a greater weight gain under intensive glucose control, and the risk of ketoacidosis was only increased in studies using insulin pumps in the intensive treatment group (very low quality evidence).Overall, all-cause mortality was very low in all studies (moderate quality evidence) except in one study investigating renal allograft as treatment for end-stage diabetic nephropathy. Health-related quality of life was only reported in the DCCT trial, showing no statistically significant differences between the intervention and comparator groups (moderate quality evidence). In addition, only the DCCT published data on costs, indicating that intensive glucose therapy control was highly cost-effective considering the reduction of potential diabetes complications (moderate quality evidence).

AUTHORS' CONCLUSIONS

Tight blood sugar control reduces the risk of developing microvascular diabetes complications. The evidence of benefit is mainly from studies in younger patients at early stages of the disease. Benefits need to be weighed against risks including severe hypoglycaemia, and patient training is an important aspect in practice. The effects of tight blood sugar control seem to become weaker once complications have been manifested. However, further research is needed on this issue. Furthermore, there is a lack of evidence from RCTs on the effects of tight blood sugar control in older patient populations or patients with macrovascular disease. There is no firm evidence for specific blood glucose targets and treatment goals need to be individualised taking into account age, disease progression, macrovascular risk, as well as the patient's lifestyle and disease management capabilities.

Glucose control and diabetic neuropathy: lessons from recent large clinical trials

Diabetic peripheral and autonomic neuropathies are common complications of diabetes with broad spectrums of clinical manifestations and high morbidity. Studies using various agents to target the pathways implicated in the development and progression of diabetic neuropathy were promising in animal models. In humans, however, randomized controlled studies have failed to show efficacy on objective measures of neuropathy. The complex anatomy of the peripheral and autonomic nervous systems, the multitude of pathogenic mechanisms involved, and the lack of uniformity of neuropathy measures have likely contributed to these failures. To date, tight glycemic control is the only strategy convincingly shown to prevent or delay the development of neuropathy in patients with type 1 diabetes and to slow the progression of neuropathy in some patients with type 2 diabetes. Lessons learned about the role of glycemic control on distal symmetrical polyneuropathy and cardiovascular autonomic neuropathy are discussed in this review.

Small- and large-fiber neuropathy after 40 years of type 1 diabetes: associations with glycemic control and advanced protein glycation: the Oslo Study

OBJECTIVE

To study large- and small-nerve fiber function in type 1 diabetes of long duration and associations with HbA1c and the advanced glycation end products (AGEs) N-ε-(carboxymethyl)lysine (CML) and methylglyoxal-derived hydroimidazolone.

RESEARCH DESIGN AND METHODS

In a long-term follow-up study, 27 persons with type 1 diabetes of 40 ± 3 years duration underwent large-nerve fiber examinations, with nerve conduction studies at baseline and years 8, 17, and 27. Small-fiber functions were assessed by quantitative sensory thresholds (QST) and intraepidermal nerve fiber density (IENFD) at year 27. HbA1c was measured prospectively through 27 years. Serum CML was measured at year 17 by immunoassay. Serum hydroimidazolone was measured at year 27 with liquid chromatography-mass spectrometry.

RESULTS

Sixteen patients (59%) had large-fiber neuropathy. Twenty-two (81%) had small-fiber dysfunction by QST. Heat pain thresholds in the foot were associated with hydroimidazolone and HbA1c. IENFD was abnormal in 19 (70%) and significantly lower in diabetic patients than in age-matched control subjects (4.3 ± 2.3 vs. 11.2 ± 3.5 mm, P < 0.001). IENFD correlated negatively with HbA1c over 27 years (r = -0.4, P = 0.04) and CML (r = -0.5, P = 0.01). After adjustment for age, height, and BMI in a multiple linear regression model, CML was still independently associated with IENFD.

CONCLUSIONS

Small-fiber sensory neuropathy is a major manifestation in type 1 diabetes of 40 years duration and more prevalent than large-fiber neuropathy. HbA1c and the AGEs CML and hydroimidazolone are important risk factors in the development of large- and small-fiber dysfunction in long-term type 1 diabetes.

Early electrophysiological abnormalities and clinical neuropathy: a prospective study in patients with type 1 diabetes

OBJECTIVE

The aim of this study was to elucidate whether subclinical nerve dysfunction as reflected by neurophysiological testing predicts the development of clinical neuropathy in patients with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Fifty-nine patients were studied twice with neurophysiological measurements at baseline and at follow-up. At baseline, patients were 15.5±3.22 years (range 7-22 years) of age, and duration of diabetes was 6.8±3.3 years. At follow-up, patients were 20-35 years of age, and disease duration was 20±5.3 years (range 10-31 years).

RESULTS

At baseline, patients showed modestly reduced nerve conduction velocities and amplitudes compared with healthy subjects, but all were free of clinical neuropathy. At follow-up, clinical neuropathy was present in nine (15%) patients. These patients had a more pronounced reduction in peroneal motor nerve conduction velocity (MCV), median MCV, and sural sensory nerve action potential at baseline (P<0.010-0.003). In simple logistic regression analyses, the predictor with the strongest association with clinical neuropathy was baseline HbA1c (R2=48%, odds ratio 7.9, P<0.002) followed by peroneal MCV at baseline (R2=38%, odds ratio 0.6, P<0.006). With the use of a stepwise forward analysis that included all predictors, first baseline HbA1c and then only peroneal MCV at baseline entered significantly (R2=61%). Neuropathy impairment assessment showed a stronger correlation with baseline HbA1c (ρ=0.40, P<0.002) than with follow-up HbA1c (ρ=0.034, P<0.007).

CONCLUSIONS

Early defects in nerve conduction velocity predict the development of diabetic neuropathy. However, the strongest predictor was HbA1c during the first years of the disease.

[Diabetic neuropathy]

These are the guidelines for diagnosis and treatment of diabetic neuropathy. This diabetic late complication comprises a number of mono- and polyneuropathies, plexopathies, radiculopathies and autonomic neuropathy. The position statement summarizes characteristic clinical symptoms and techniques for diagnostic assessment of diabetic neuropathy. Recommendations for the therapeutic management of diabetic neuropathy, especially for the control of pain in sensomotoric neuropathy, are provided.

Enhanced glucose control for preventing and treating diabetic neuropathy

BACKGROUND

There are two types of diabetes. Type 1 diabetes affects younger people and needs treatment with insulin injections. Type 2 diabetes affects older people and can usually be treated by diet and oral drugs. Diabetic neuropathy affects 10% of patients with diabetes mellitus at diagnosis and 40% to 50% after 10 years. Enhanced glucose control is the best studied intervention for the prevention of this disabling condition but there have been no systematic reviews of the evidence.

OBJECTIVES

To examine the evidence for enhanced glucose control in the prevention of distal symmetric polyneuropathy in people with type 1 and type 2 diabetes.

SEARCH METHODS

We searched the Cochrane Neuromuscular Disease Group Specialized Register (30 January 2012), CENTRAL (2012, Issue 1), MEDLINE (1966 to January 2012) and EMBASE (1980 to January 2012) for randomized controlled trials of enhanced glucose control in diabetes mellitus.

SELECTION CRITERIA

We included all randomized, controlled studies investigating enhanced glycemic control that reported neuropathy outcomes after at least one year of intervention. Our primary outcome measure was annual development of clinical neuropathy defined by a clinical scale. Secondary outcomes included motor nerve conduction velocity and quantitative vibration testing. 

DATA COLLECTION AND ANALYSIS

Two authors independently reviewed all titles and abstracts identified by the database searches for inclusion. Two authors abstracted data from all included studies with a standardized form. A third author mediated conflicts. We analyzed the presence of clinical neuropathy with annualized risk differences (RDs), and conduction velocity and quantitative velocity measurements with mean differences per year. 

MAIN RESULTS

This review identified 17 randomized studies that addressed whether enhanced glucose control prevents the development of neuropathy. Seven of these studies were conducted in people with type 1 diabetes, eight in type 2 diabetes, and two in both types. A meta-analysis of the two studies that reported the primary outcome (incidence of clinical neuropathy) with a total of 1228 participants with type 1 diabetes revealed a significantly reduced risk of developing clinical neuropathy in those with enhanced glucose control, an annualized RD of -1.84% (95% confidence interval (CI) -1.11 to -2.56). In a similar analysis of four studies that reported the primary outcome, involving 6669 participants with type 2 diabetes, the annualized RD of developing clinical neuropathy was -0.58% (95% CI 0.01 to -1.17). Most secondary outcomes were significantly in favor of intensive treatment in both populations. However, both types of diabetic participants also had a significant increase in severe adverse events including hypoglycemic events.

AUTHORS' CONCLUSIONS

According to high-quality evidence, enhanced glucose control significantly prevents the development of clinical neuropathy and reduces nerve conduction and vibration threshold abnormalities in type 1 diabetes mellitus. In type 2 diabetes mellitus, enhanced glucose control reduces the incidence of clinical neuropathy, although this was not formally statistically significant (P = 0.06). However, enhanced glucose control does significantly reduce nerve conduction and vibration threshold abnormalities. Importantly, enhanced glucose control significantly increases the risk of severe hypoglycemic episodes, which needs to be taken into account when evaluating its risk/benefit ratio.

Diabetic polyneuropathies: update on research definition, diagnostic criteria and estimation of severity

Prior to a joint meeting of the Neurodiab Association and International Symposium on Diabetic Neuropathy held in Toronto, Ontario, Canada, 13-18 October 2009, Solomon Tesfaye, Sheffield, UK, convened a panel of neuromuscular experts to provide an update on polyneuropathies associated with diabetes (Toronto Consensus Panels on DPNs, 2009). Herein, we provide definitions of typical and atypical diabetic polyneuropathies (DPNs), diagnostic criteria, and approaches to diagnose sensorimotor polyneuropathy as well as to estimate severity. Diabetic sensorimotor polyneuropathy (DSPN), or typical DPN, usually develops on long-standing hyperglycaemia, consequent metabolic derangements and microvessel alterations. It is frequently associated with microvessel retinal and kidney disease-but other causes must be excluded. By contrast, atypical DPNs are intercurrent painful and autonomic small-fibre polyneuropathies. Recognizing that there is a need to detect and estimate severity of DSPN validly and reproducibly, we define subclinical DSPN using nerve conduction criteria and define possible, probable, and confirmed clinical levels of DSPN. For conduct of epidemiologic surveys and randomized controlled trials, it is necessary to pre-specify which attributes of nerve conduction are to be used, the criterion for diagnosis, reference values, correction for applicable variables, and the specific criterion for DSPN. Herein, we provide the performance characteristics of several criteria for the diagnosis of sensorimotor polyneuropathy in healthy subject- and diabetic subject cohorts. Also outlined here are staged and continuous approaches to estimate severity of DSPN.

Critical appraisal of the use of alpha lipoic acid (thioctic acid) in the treatment of symptomatic diabetic polyneuropathy

BACKGROUND

The most common of the neuropathies associated with diabetes mellitus, diabetic sensorimotor polyneuropathy (DSPN) is a syndrome of diffuse, length-dependent, symmetric nerve dysfunction. The condition is linked with substantial morbidity, frequent healthcare utilization, and compromised quality of life due to related discomfort. Correspondingly, antidepressants, anticonvulsants, and opioids are regularly prescribed with the goal of pain control. However, the agents rarely provide complete pain relief and fail to address progression of the disorder. Whereas strict blood glucose control can slow the onset and worsening of DSPN, near-normoglycemia is not easily attainable. Evidence implicating oxidative processes in the pathogenesis of DSPN offers one potentially important therapeutic avenue. Due to its properties as a potent antioxidant, alpha lipoic acid (ALA) could mitigate the development of DSPN and attenuate resultant symptoms and signs. Approved for treatment of DSPN in Germany, the agent is not more widely used due to uncertainty about its efficacy and reported adverse effects. Here we review the effectiveness and tolerability of ALA in the treatment of symptomatic DSPN.

METHODS

The MEDLINE, EMBASE, and Cochrane Library databases were searched for English-language literature on the topic. Randomized, blinded studies comparing parenteral and oral ALA with placebo in the treatment of peripheral neuropathy in diabetic adults were selected. Analysis included studies with a level of evidence of at least 2b.

RESULTS

The current appraisal summarizes data from 1160 participants in the ALADIN, SYDNEY, ORPIL, SYDNEY 2, and ALADIN III trials. In four of the studies, ALA provided significant improvement in manifestations of DSPN.

CONCLUSION

Treatment with ALA 600 mg iv daily for 3 weeks represents a well-tolerated and effective therapy for DSPN. An oral dose of 600 mg daily administered for up to 5 weeks could offer benefits in symptoms and signs of DSPN without significant side effects.

Duloxetine in the management of diabetic peripheral neuropathic pain

Diabetic neuropathy affects up to 70% of diabetics, and diabetic peripheral neuropathic pain (DPNP) is the most common and debilitating of the diabetic neuropathies. DPNP significantly reduces quality of life and increases management costs in affected patients. Despite the impact of DPNP, management is poor with one-quarter of patients receiving no treatment and many treated with medications having little or no efficacy in managing DPNP. Duloxetine is one of two drugs approved by the United States Food and Drug Administration for DPNP management. Duloxetine is a serotonin and norepinephrine reuptake inhibitor (SNRI) proven safe, effective, and cost-saving in reducing DPNP symptoms at a dose of 60 mg/day. Duloxetine doses greater than 60 mg/day for DPNP management are not recommended since they are no more efficacious and associated with more side effects; addition of pregabalin or gabapentin for these patients may be beneficial. Side effects of duloxetine are generally mild and typical for the SNRI class including nausea, dizziness, somnolence, fatigue, sweating, dry mouth, constipation, and diarrhea. Given its other indications, duloxetine is a particularly good choice for DPNP treatment in patients with coexisting depression, anxiety, fibromyalgia, or chronic musculoskeletal pain. Duloxetine treatment had no clinically significant effect on glycemic control and did not increase the risk of cardiovascular events in diabetes patients. However, duloxetine use should be avoided in patients with hepatic disease or severe renal impairment. Given its safety, efficacy, and tolerability, duloxetine is an excellent choice for DPNP treatment in many patients.

Pancreas transplantation

Diabetes mellitus is generally treated with oral diabetic drugs and/or insulin. However, the morbidity and mortality associated with this condition increases over time, even in patients receiving intensive insulin treatment, and this is largely attributable to diabetic complications or the insulin therapy itself. Pancreas transplantation in humans was first conducted in 1966, since when there has been much debate regarding the legitimacy of this procedure. Technical refinements and the development of better immunosuppressants and better postoperative care have brought about marked improvements in patient and graft survival and a reduction in postoperative morbidity. Consequently, pancreas transplantation has become the curative treatment modality for diabetes, particularly for type I diabetes. An overview of pancreas transplantation is provided herein, covering the history of pancreas transplantation, indications for transplantation, cadaveric and living donors, surgical techniques, immunosuppressants, and outcome following pancreas transplantation. The impact of successful pancreas transplantation on the complications of diabetes will also be reviewed briefly.

Painful diabetic neuropathy: epidemiology, natural history, early diagnosis, and treatment options

OBJECTIVE

To facilitate the clinician's understanding of the basis and treatment of painful diabetic neuropathy (PDN).

BACKGROUND

PDN is one of several clinical syndromes in patients with diabetic peripheral neuropathy (DPN) and presents a major challenge for optimal management.

METHODS

A systematic review of the literature was undertaken for articles specific to PDN, using Medline databases between 1966 and 2007.

RESULTS

The epidemiology of PDN has not been well established and on the basis of available data the prevalence of pain is 10% to 20% in patients with diabetes and from 40% to 50% in those with diabetic neuropathy. It has a significant impact on the quality of life and health care costs. Pathophysiologic mechanisms underlying PDN are similar to other neuropathic pain disorders and are broadly characterized as peripheral and central sensitization. The natural course of PDN is variable, with many patients experiencing spontaneous improvement and resolution of pain. Hyperglycemia-induced pathways result in nerve dysfunction and damage, which lead to hyperexcitable peripheral and central pathways of pain. Glycemic control may prevent or partially reverse DPN and modulate PDN. Quantifying neuropathic pain is difficult, especially for clinical trials, although this has improved recently with the development of neuropathic pain-specific tools, such as the Neuropathic Pain Questionnaire and the Neuropathic Pain Symptom Inventory. Current therapeutic options are limited to symptomatic treatment and are similar to other types of neuropathic pain.

CONCLUSIONS

A better understanding of the peripheral and central mechanisms resulting in PDN is likely to promote the development of more targeted and effective treatment.

[Cardiovascular impact of the autonomic neuropathy of diabetes mellitus]

The neuropathic complications related to Diabetes may affect the somatic, sympathetic and parasympathetic nervous system. As a result, there are several clinical manifestations of diabetic neuropathy. They can be related to nervous system lesions of the genital, urinary, gastro-intestinal, skin and cardiovascular tissues. The results of these alterations are loss in the quality of life as well as increase of mortality indexes related to sudden death with cardiac arrhythmias and other causes. The cardiovascular autonomic neuropathy probably contributes to the bad prognosis of the coronary heart disease and of the heart failure in type 1 and type 2 diabetic patients. For diabetologists, the nervous complications of diabetes are the result of an increase influx of glucose to the neuronal and endothelial cells. Evidences show that, with the aim of preventing these complications, the diabetic patients should receive a precocious diagnosis and be instructed for having a good metabolic and blood pressure control. Use of angiotensin converting enzyme inhibitors and beta adrenergic blockers are probably of impact in the prevention of the cardiac autonomic complications of diabetes.

Slower conduction velocity and motor unit discharge frequency are associated with muscle fatigue during isometric exercise in type 1 diabetes mellitus

Type 1 diabetes mellitus (T1DM) is associated with a peripheral neuropathy that reduces nerve conduction velocity. This may impair high motor-unit discharge frequencies (MUDF), decrease muscle activation, and curtail the ability to sustain repetitive contractile tasks. We examined (1) whether MUDF, the contractile properties of the knee extensors, and the conduction velocity of persons with T1DM differed from controls; (2) whether persons with T1DM can maintain adequate MUDF during a fatigue protocol; and (3) the relationship between these parameters and impaired glycemic control. We studied male and female subjects with T1DM and controls matched for age, height, weight, and gender. Single motor unit recordings were made from vastus lateralis during maximal and submaximal contractions and during a fatigue protocol. Glycemic control was assessed from blood glucose concentration and glycosylated hemoglobin (HbA1c). Control femoral conduction velocities were comparable to literature values and those of the T1DM subjects were slower. These values correlated with plasma glucose and HbA1c. T1DM subjects fatigued 45% sooner than controls, and time to fatigue and conduction velocity were correlated (r = 0.54, P < 0.05). Discharge frequencies tended to be slower during 50% maximal voluntary contractile force in the T1DM subjects at task failure. Persons with T1DM had slower conduction velocities and lower MUDF than their controls, which apparently leads to impaired activation of muscle and decreased endurance during isometric fatigue.

Involvement of advanced glycation end products in the pathogenesis of diabetic complications: the protective role of regular physical activity

Advanced glycation end products (AGEs) may play an important role in the pathogenesis of chronic diabetic complications and in the natural process of biological aging. In fact, maintained hyperglycaemia favours the formation of AGEs at the tissue level in diabetic patients, which may influence the triggering of different chronic pathologies of diabetes such as retinopathy, nephropathy, neuropathy and macro- and micro-vascular diseases. Moreover, the literature has also demonstrated the involvement of AGEs in biological aging, which may explain the accelerated process of aging in diabetic patients. The practice of regular physical activity appears to positively influence glycaemic control, particularly in type 2 diabetes mellitus patients. This occurs through the diminution of fasting glycaemia, with a consequent reduction of glycation of plasmatic components suggested by the normalisation of HbA1c plasmatic levels. This exercise-induced positive effect is evident in the blood of diabetic patients and may also reach the endothelium and connective tissues of different organs, such as the kidneys and eyes, and systems, such as the cardiovascular and nervous systems, with a local reduction of AGEs production and further deceleration of organ dysfunction. The aim of this paper was to review the literature concerning this topic to coherently describe the harmful effects of AGEs in organ dysfunction induced by diabetes in advanced age as well as the mechanisms behind the apparent protection given by the practice of regular physical activity.

Does impaired glucose metabolism cause polyneuropathy? Review of previous studies and design of a prospective controlled population-based study

In spite of extensive studies it is unclear whether impaired fasting glucose (IFG) or impaired glucose tolerance (IGT), i.e., impaired glucose metabolism (IGM), causes diabetic sensorimotor polyneuropathy (DSPN) or chronic idiopathic axonal polyneuropathy (CIAP); the results and conclusions vary considerably in different studies. Some studies suggest that IGM is a common and important cause of CIAP, whereas others do not. On reviewing these data, we judge that a considerable degree of this disparity may relate to differences in selection of patients, choice of controls, assessment of chronic glycemic exposure and of diabetic complications, and statistical power. Here we review previous studies, list the reasons that the issue needs further study, and outline a study now in progress to address the question more definitively.

Challenges in design of multicenter trials: end points assessed longitudinally for change and monotonicity

OBJECTIVE

Assessing clinimetric performance of diabetic sensorimotor polyneuropathy (DSPN) end points in single and multicenter trials.

RESEARCH DESIGN AND METHODS

Assessed were placebo-treated patients with DSPN in the Viatris and Eli Lilly trials and an epidemiologic cohort.

RESULTS

Test reproducibility in clinical trial cohorts (r(I) approximately 0.7-0.85) approached that in the epidemiologic cohort (r(I) approximately 0.85-0.95). Associations between pairs of end points explained <10% of the variability of data (sometimes 15-35%), being higher in the epidemiologic cohort and the Viatris trial than in the Lilly trial. Most end points did not show monotonic worsening over 4 years. However, sural nerve amplitude and peroneal motor conduction velocity did. A nerve conduction score (Sigma 5 NC nds [5 attributes of nerve conduction expressed as normal deviates]) did not show monotonic worsening in established DSPN. In the epidemiologic cohort followed for 9.5 years, monotonic worsening of small magnitude occurred for sural amplitude, vibration detection threshold, and especially for composite quantitative sensation.

CONCLUSIONS

The main reason why it is difficult to demonstrate monotonic worsening of neuropathic end points appears to be a very slow worsening of DSPN, a placebo effect for symptoms and signs, and measurement noise. Demonstrating disease progression in controlled trials of DSPN is more likely when 1) patients with developing rather than established DSPN are selected, 2) type 1 diabetic patients are preferentially recruited, 3) patients are selected who cannot or will not achieve ideal glycemic control, 4) end points chosen are known to show monotonic worsening, and 5) a restricted number of centers and expert examiners (trained, certified, using standard approaches, and reference values and interactive surveillance of tests) are used.

Incipient cardiovascular autonomic imbalance revealed by wavelet analysis of heart rate variability in Type 2 diabetic patients

AIM

Incipient cardiovascular autonomic imbalance is not readily diagnosed by conventional methods. Spectral analysis of heart rate variability (HRV) by wavelet transform (WT) was used to measure cardiovascular autonomic function in patients with Type 2 diabetes.

METHODS

Thirty-two diabetic patients without (D), 26 with cardiovascular autonomic neuropathy (DAN) and 72 control subjects (C) participated. A 30-min HRV time series was analysed by wavelet transformation and four characteristic frequency intervals were defined: I (0.0095-0.021 Hz), II (0.021-0.052 Hz), III (0.052-0.145 Hz) and IV (0.145-0.6 Hz).

RESULTS

When compared with C, in both D and DAN the normalized power and amplitude of interval II were increased and of interval IV decreased, resulting in a significantly higher II/IV ratio. Furthermore, in DAN the normalized power and amplitude of interval I were increased and of interval III decreased when compared with the D and C groups. The diabetic patients were divided in two equal subgroups according to HbA(1c) < 8.0% and >or= 8.0%. In the subgroup with HbA(1c) >or= 8.0%, normalized power in interval II was significantly higher and in interval IV significantly lower than in the subgroup with HbA(1c) < 8.0%. In D, but not in DAN patients prescribed ACE inhibitors, the absolute amplitude and power of oscillations were significantly higher than in patients not taking ACE inhibitor therapy.

CONCLUSIONS

Patients with diabetes have increased sympathetic and decreased parasympathetic cardiac activity regardless of the presence of autonomic neuropathy. Glycaemic control and treatment with ACE inhibitors may favourably influence HRV in diabetic patients without autonomic neuropathy.

Modeling chronic glycemic exposure variables as correlates and predictors of microvascular complications of diabetes

OBJECTIVE

The degree to which chronic glycemic exposure (CGE) (fasting plasma glucose [FPG], HbA1c [A1C], duration of diabetes, age at onset of diabetes, or combinations of these) is associated with or predicts the severity of microvessel complications is unsettled. Specifically, we test whether combinations of components correlate and predict complications better than individual components.

RESEARCH DESIGN AND METHODS

Correlations and predictions of CGE and complications were assessed in the Rochester Diabetic Neuropathy Study, a population-based, cross-sectional, and longitudinal epidemiologic survey of 504 patients with diabetes followed for up to 20 years.

RESULTS

In multivariate analysis, A1C and duration of diabetes (and to a lesser degree age at onset of diabetes but not FPG) were the main significant CGE risk covariates for complications. A derived glycemic exposure index (GE(i)) correlated with and predicted complications better than did individual components. Composite or staged measures of polyneuropathy provided higher correlations and better predictions than did dichotomous measures of whether polyneuropathy was present or not. Generally, the mean GE(i) was significantly higher with increasing stages of severity of complications.

CONCLUSIONS

A combination of A1C, duration of diabetes, and age at onset of diabetes (a mathematical index, GE(i)) correlates significantly with complications and predicts later complications better than single components of CGE. Serial measures of A1C improved the correlations and predictions. For polyneuropathy, continuous or staged measurements performed better than dichotomous judgments. Even with intensive assessment of CGE and complications over long times, only about one-third of the variability of the severity of complications is explained, emphasizing the role of other putative risk covariates.

Recent developments in the assessment of efficacy in clinical trials of diabetic neuropathy

A large number of measures may be employed in clinical practice and for epidemiologic studies to quantify and risk stratify diabetic patients with neuropathy. However, not all measures are suitable for assessing the benefits of therapeutic intervention. Therefore, for the purpose of this review we focus on measures that may be employed to define the efficacy of interventions in clinical trials of human diabetic neuropathy. Two major types of end points are used: 1) those that assess symptoms for defining efficacy in painful diabetic neuropathy, and 2) those that assess neurologic deficits that assess the effects of treatments that may prevent further degeneration or promote repair.

Foot ulcer risk is lower in South-Asian and african-Caribbean compared with European diabetic patients in the U.K.: the North-West diabetes foot care study

OBJECTIVE

To determine 1) foot ulcer rates for European, South-Asian, and African-Caribbean diabetic patients in the U.K and 2) the contribution of neuropathy and peripheral arterial disease (PAD) differences to altered ulcer risk between the groups.

RESEARCH DESIGN AND METHODS

In this U.K. population-based study, we screened 15,692 type 1 and type 2 diabetic patients in the community health care setting for foot ulcers, foot deformities, neuropathy, and PAD plus other characteristics. In total, 13,409 were European (85.5%), 1,866 were South Asian (11.9%), and 371 were African Caribbean (2.4%).

RESULTS

The age-adjusted prevalence of diabetic foot ulcers (past or present) for Europeans, South Asians, and African Caribbeans was 5.5, 1.8, and 2.7%, respectively (P < 0.0001). Asians and African Caribbeans had less neuropathy, PAD, and foot deformities than Europeans (P = 0.003). The unadjusted risk of ulcer (odds ratio [OR]) for Asians versus Europeans was 0.29 (95% CI 0.20-0.41) (P < 0.0001). PAD, neuropathy, foot deformities, and insulin use attenuated the age-adjusted OR from 0.32 to 0.52 (0.35-0.76) (P < 0.0001). African-Caribbean versus European ulcer risk in males was attenuated from 0.60 to 0.71 by vibration sensation.

CONCLUSIONS

South Asians with diabetes in the U.K. have about one-third the risk of foot ulcers of Europeans. The lower levels of PAD, neuropathy, insulin usage, and foot deformities of the Asians account for approximately half of this reduced foot ulcer risk. Lower neuropathy is the main contributor to the reduced African-Caribbean ulcer rate, particularly in men. The reasons for these ethnic differences warrant further investigation.

Effect of Glycemic Control on Electrophysiologic Changes of Diabetic Neuropathy in Type 2 Diabetic Patients

Diabetic neuropathy is a common complication of diabetes mellitus. Effective blood glucose control retards changes in nerve conduction velocity in type 1 diabetes. This study examined the relationship between glycemic control and electrophysiologic changes in diabetic neuropathy in 57 type 2 diabetic patients. Nerve conduction in the peroneal motor nerve, tibial motor nerve, and sural nerve were measured at study entry and at follow-up 24+/-3.12 months later. Changes in individual nerves are expressed as a percentage change (PC) and overall electrophysiologic changes are expressed as the sum of individual PCs. The PCs for peroneal motor nerve velocity, tibial motor nerve velocity, and sural nerve velocity were all lower in patients with a mean HbA1c of 8.5% or less compared with those in patients with a mean HbA1c of more than 8.5%, and SPCV (sum of PC in velocity) was significantly inversely correlated with mean HbA1c. However, there was no significant difference in SPCV in subjects with or without hypertension, hypertriglyceridemia, or low high-density lipoprotein cholesterol concentration. In conclusion, hyperglycemia is the most important etiology for electrophysiologic progression in type 2 diabetic patients. Furthermore, a mean HbA1c of more than 8.5% will result in significant deterioration in electrophysiology.

Diabetic neuropathies

Diabetic neuropathy (DN) is a common complication of diabetes that often is associated with considerable morbidity and mortality. The epidemiology and natural history of DN is clouded with uncertainty because of confusion regarding the definition and measurement of this disorder. The recent resurgence of interest in the vascular hypothesis, oxidative stress, the neurotrophic hypothesis,and the possibility of the role of autoimmunity has opened up new avenues of investigation for therapeutic intervention. The ability to manage successfully the many different manifestations of diabetic neuropathy depends ultimately on success in uncovering the pathogenic processes underlying this disorder.

Eighteen years of fair glycemic control preserves cardiac autonomic function in type 1 diabetes

OBJECTIVE

To study the association between 18 years of mean HbA(1c) and cardiac autonomic function in type 1 diabetic patients having used intensive insulin treatment.

RESEARCH DESIGN AND METHODS

A total of 39 patients with type 1 diabetes were followed during 18 years, and HbA(1c) was measured yearly. At 18 years follow-up heart rate variability (HRV) measurements were used to assess cardiac autonomic function. Standard cardiac autonomic tests during normal breathing, deep breathing, the Valsalva maneuver, and the tilt test were performed. Maximal heart rate increase during exercise electrocardiogram and minimal heart rate during sleep were also used to describe cardiac autonomic function.

RESULTS

We present the results for patients with mean HbA(1c) <8.4% (two lowest HbA(1c) tertiles) compared with those with HbA(1c) > or = 8.4% (highest HbA(1c) tertile). All of the cardiac autonomic tests were significantly different in the high- and the low-HbA(1c) groups, and the most favorable scores for all tests were seen in the low-HbA(1c) group. In the low-HbA(1c) group, the HRV was 40% during deep breathing, and in the high-HbA(1c) group, the HRV was 19.9% (P = 0.005). Minimal heart rate at night was significantly lower in the low-HbA(1c) groups than in the high-HbA(1c) group (P = 0.039). With maximal exercise, the increase in heart rate was significantly higher in the low-HbA(1c) group compared with the high-HbA(1c) group (P = 0.001).

CONCLUSIONS

Mean HbA(1c) during 18 years was associated with cardiac autonomic function. Cardiac autonomic function was preserved with HbA(1c) <8.4%, whereas cardiac autonomic dysfunction was impaired in the group with HbA(1c) > or = 8.4%.

Nerve conduction in children suffering insulin dependent diabetes mellitus

OBJECTIVE

To determine the incidence of peripheral neuropathy in children suffering Insulin Dependent Diabetes Mellitus (IDDM) as well as to determine the relationship between other criteria of the disease and neuropathy.

METHODS

40 children (17 males, mean age 11.9 years) suffering IDDM and receiving insulin therapy involving two injections a day and 30 healthy children (17 males, mean age 11.7 years) were included in the study. They were inquired about their demographical characteristics as well as the presence of neurological symptoms. Their detailed neurological examinations were conducted. Their glycemic control values (Hb A1C) were recorded, and their nerve conduction studies were performed from right upper and lower extremities.

RESULTS

All nerve conduction values of children with IDDM were found to be significantly lower (p<0.0001) as compared to the control group. 60% of diabetic children (n=24) were found to suffer peripheral neuropathy. Statistically significant relationships were found between the glycemic control values and the peroneal, sural, tibial, ulnar and median nerve conduction velocities, and also between the duration of disease and the peroneal, sural, tibial and median nerve conduction velocities.

CONCLUSION

The peripheral neuropathy is rather a frequently observed complication in diabetic children. The duration of disease and impaired glycemic control play an important role in the development of neuropathy. The introduction of new methods designed to ensure better glycemic control will reduce the incidence of the complication.

Optimal blood glucose control during 18 years preserves peripheral nerve function in patients with 30 years' duration of type 1 diabetes

OBJECTIVE

To assess the association between 18 years of mean HbA(1c) and nerve conduction parameters of the lower limb in patients with type 1 diabetes of 30 years' duration.

RESEARCH DESIGN AND METHODS

HbA(1c) has been examined prospectively since 1982 in a group of 39 patients with type 1 diabetes. Mean age at baseline was 25 years (range 18-40) with 12 years' disease duration. The mean age at diagnosis of diabetes was 12.5 years. Nerve function of lower limbs was assessed at baseline, after 8 years, and after 18 years.

RESULTS

A total of 23 men and 16 women were studied. Mean age was 43 years. Mean HbA(1c) was 8.2% (range 6.6-11.3) during 18-year follow-up. Nerve conduction velocity (NCV) and nerve action potential amplitude (NAPA) at the last examination were significantly associated with mean HbA(1c) (P < 0. 05). From 1982 to 1999, there was a significant reduction in nerve function in patients with mean HbA(1c) >or=8.4% (highest tertile). For example, the mean NCV in the tibial nerve was reduced from 47 to 31 m/s (P < 0.01). The number of nerves with NCV (P < 0.01) and NAPA (P = 0.01) reduced to below the reference level in each patient was also significantly associated to mean HbA(1c). No significant associations were found between nerve function parameters, sex, disease duration, blood pressure, serum cholesterol, microalbuminuria, or smoking.

CONCLUSIONS

The present study shows that mean HbA(1c) is a strong predictor of nerve function. Mean HbA(1c) <8.4% over 18 years was associated with near-normal nerve function.

The sensory symptoms of diabetic polyneuropathy are improved with alpha-lipoic acid: the SYDNEY trial

OBJECTIVE

Because alpha-lipoic acid (ALA), a potent antioxidant, prevents or improves nerve conduction attributes, endoneurial blood flow, and nerve (Na(+) K(+) ATPase activity in experimental diabetes and in humans and may improve positive neuropathic sensory symptoms, in this report we further assess the safety and efficacy of ALA on the Total Symptom Score (TSS), a measure of positive neuropathic sensory symptoms.

RESEARCH DESIGN AND METHODS

Metabolically stable diabetic patients with symptomatic (stage 2) diabetic sensorimotor polyneuropathy (DSPN) were randomized to a parallel, double-blind study of ALA (600 mg) (n = 60) or placebo (n = 60) infused daily intravenously for 5 days/week for 14 treatments. The primary end point was change of the sum score of daily assessments of severity and duration of TSS. Secondary end points were sum scores of neuropathy signs (NIS), symptoms (NSC), attributes of nerve conduction, quantitative sensation tests (QSTs), and an autonomic test.

RESULTS

At randomization, the groups were not significantly different by the criteria of metabolic control or neuropathic end points. After 14 treatments, the TSS of the ALA group had improved from baseline by an average of 5.7 points and the placebo group by an average of 1.8 points (P < 0.001). Statistically significant improvement from baseline of the ALA, as compared with the placebo group, was also found for each item of the TSS (lancinating and burning pain, asleep numbness and prickling), NIS, one attribute of nerve conduction, and global assessment of efficacy.

CONCLUSIONS

Intravenous racemic ALA, a potent antioxidant, rapidly and to a significant and meaningful degree, improved such positive neuropathic sensory symptoms as pain and several other neuropathic end points. This improvement of symptoms was attributed to improved nerve pathophysiology, not to increased nerve fiber degeneration. Because of its safety profile and its effect on positive neuropathic sensory symptoms and other neuropathic end points, this drug appears to be a useful ancillary treatment for the symptoms of diabetic polyneuropathy.

Clinical trials for drugs against diabetic neuropathy: can we combine scientific needs with clinical practicalities?

Diabetic neuropathy is a chronic progressive disease accounting for considerable morbidity and reduced quality of life among patients with diabetes. Accumulating evidence suggests that the clinical and neurophysiological markers used to assess neuropathy not only predict the development of neuropathic foot ulceration, one of the most common causes for hospital admission and lower limb amputations, but are also predictors of increased mortality in diabetic patients. In addition to metabolic control, drug treatment of both incipient and clinically manifest diabetic neuropathy will be necessary for the years to come. Because 1-2% of the whole population in western societies may be affected, the search for effective drug treatment is not only a very important goal for the patient suffering from diabetic neuropathy and for the practicing physician, but also an economic task for both the health care systems and pharmaceutical companies. The validity of inferences about the clinical consequences of the use of any given agent to induce a specific pharmacologic effect will depend not only on the extent to which it affects the targeted biological phenomenon, but also on the extent to which all of the actions of the agent have been defined and the extent to which all affect the entire organism, alone and in concert. The ultimate test of the usefulness of a drug or device depends on the determination of outcomes, ideally in randomized clinical trials (RCTs) of sufficient scope and duration. The efficacy and safety of a variety of drugs based on the different pathogenetic hypotheses proposed have been evaluated in RCTs since the 1970s. However, the quality of RCTs published between 1981 and 1992 that evaluated the effects of medical treatment in diabetic polneuropathy was poor. Adequate designs for RCTs in diabetic neuropathy must consider the following criteria: type and stage of neuropathy, homogeneity of the study population, outcome measures (neurophysiological markers, intermediate clinical end points, ultimate clinical outcomes, quality of life), natural history, sample size, study duration, reproducibility of neurophysiological and intermediate end points, nonspecific effects of treatment, measures of treatment effect, the extent to which the overall trail result applies to individual patients (external validity), and the reporting of the RCTs. Trials focusing preferentially on patients with mild or moderate early stages of neuropathy over long periods of 3-5 years aimed at slowing or prevention, rather than reversal, using end point measures that have clinical and prognostic significance are most likely to produce meaningful results.

Dual effect of glucose on LDL oxidation: dependence on vitamin E

The aim of the present study was to determine the direct effect of glucose on LDL oxidation, a key step in the development of atherosclerosis. Purified human LDL were incubated with glucose (500 mg/dl) and LDL oxidation was started by adding CuCl(2) to the media. Glucose delayed the vitamin E consumption, but accelerated the formation of conjugated dienes and increased both the formation of thiobarbituric acid reacting substances (TBARS) and LDL electrophoretic mobility. When LDL were incubated with increasing concentrations of glucose and submitted to oxidation, the formation of conjugated dienes, TBARS, and the electrophoretic mobility increased in a concentration-dependent manner. When LDL was enriched with vitamin E, it showed a delay in the formation of conjugated dienes, even in the presence of glucose. To determine whether glucose had any effect on LDL oxidation, once the process was started and vitamin E consumed, LDL were submitted to oxidation and, at different times thereafter, glucose was added into the media. Under these conditions glucose also accelerated the LDL oxidation. In summary, present results show that in LDL submitted to oxidation, glucose delays the early phases of the oxidation, slowing the vitamin E consumption, but it accelerates the rate of LDL oxidation once LDL vitamin E has been consumed; the effect being concentration-dependent.

Silent coronary atheromatosis in type 1 diabetic patients and its relation to long-term glycemic control

Type 1 diabetic patients have a pronounced risk of premature coronary artery disease and death. We sought to evaluate the prevalence of silent coronary atheromatosis and to evaluate the relation between coronary atheromatosis and glycemic control. Coronary atheromatosis was evaluated in type 1 diabetic patients with no symptoms of coronary artery disease by exercise electrocardiogram (ECG) in 39 patients and quantitative coronary angiography and by intravascular ultrasound (IVUS) examinations in 29 patients. The findings from the IVUS examinations were related to mean HbA(1c) collected prospectively over 18 years. Abnormal exercise ECGs were found in 15% of patients, and angiographic diameter stenosis of >50% in one or more of the main coronary arteries was found in 34% of patients. All patients examined with intracoronary ultrasound had developed atherosclerotic plaques with an increased intimal thickness (>0.5 mm) in one or more of the coronary arteries. Coronary artery plaque formation, as judged by ultrasound, was significantly related to mean HbA(1c) during 18 years (P < 0.05) after adjustment for total cholesterol and age. This study demonstrates a high prevalence of silent coronary atheromatosis in type 1 diabetic patients with no symptoms of coronary heart disease. Long-term glycemic control was shown to be associated with coronary atheromatosis.

Diabetic neuropathy--a continuing enigma

In this article we will review the clinical signs and symptoms of diabetic somatic polyneuropathy (DPN), its prevalence and clinical management. Staging and classification of DPN will be exemplified by various staging paradigms of varied sophistication. The results of therapeutic clinical trials will be summarized. The pathogenesis of diabetic neuropathy reviews an extremely complex issue that is still not fully understood. Various recent advances in the understanding of the disease will be discussed, particularly with respect to the differences between neuropathy in the two major types of diabetes. The neuropathology and natural history of diabetic neuropathy will be discussed pointing out the heterogeneities of the disease. Finally, the various prospective therapeutic avenues will be dealt with and discussed.

Motor function in diabetic neuropathy

In contrast to sensory and autonomic disturbances motor function has seldomly been studied in diabetic neuropathy. Recently quantitative studies of long-term type 1 diabetic patients have shown that the strength of the ankle and knee extensors and flexors are moderately impaired. The weakness is closely related to the severity of neuropathy. Applying quantitative electromyography the degree of reinnervation is related to the muscle strength in diabetic patients suggesting the reinnervation to be insufficient. Magnetic resonance imaging of the distal part of the leg has revealed substantial muscular atrophy closely related to the degree of muscle weakness. The present findings indicate that diabetic neuropathy often is a mixed sensory-motor neuropathy.