Peripheral nerve dysfunction is reflected by loss of ankle reflexes but not by autonomic neuropathy in diabetic patients

Temporal trend of small nerve fibre degeneration in people with and without type 2 diabetes mellitus

AIMS

We investigated the long-term temporal trend of intraepidermal nerve fibre density (IENFD) and the association between changes in IENFD and metabolic factors in individuals with and without type 2 diabetes.

METHODS

A total of 66 participants were enrolled in this longitudinal population-based study, at baseline consisting of 35 individuals (median 61 years) without diabetes and 31 individuals with type 2 diabetes mellitus. Participants underwent clinical and electrophysiological examinations, as well as a skin biopsy both at baseline and at the follow-up visit (mean 8.1 ± 0.5 years). IENFD was assessed in thin sections of 5 μm, stained with the protein gene product 9.5-antibody and compared between the groups.

RESULTS

IENFD decreased during the period in both groups, with a greater decline in the group without diabetes than in type 2 diabetes (-2.3 and -0.6 fibres/mm respectively; p < 0.001). While IENFD at baseline was significantly reduced in type 2 diabetes relative to people without (p < 0.001), no difference in IENFD was found between groups at the follow-up (p = 0.183). Linear mixed model analysis indicated that age, weight and HbA_1c were associated with decrease in IENFD in the total population (p < 0.007). IENFD also decreased with increasing age and weight, but not with HbA_1c , in the separate groups (p < 0.049).

CONCLUSIONS

Despite lower IENFD levels at baseline in type 2 diabetes, IENFD was equal between the groups at follow-up. A decrease in IENFD is to a limited extent affected by body weight, and HbA_1c , but age seems to be the long-term determinant of IENFD in an elderly population.

Evaluation of small nerve fiber dysfunction in type 2 diabetes

OBJECTIVES

To assess potential correlations between intraepidermal nerve fiber densities (IENFD), graded with light microscopy, and clinical measures of peripheral neuropathy in elderly male subjects with normal glucose tolerance (NGT), impaired glucose tolerance (IGT), and type 2 diabetes (T2DM), respectively.

MATERIALS AND METHODS

IENFD was assessed in thin sections of skin biopsies from distal leg in 86 men (71-77 years); 24 NGT, 15 IGT, and 47 T2DM. Biopsies were immunohistochemically stained for protein gene product (PGP) 9.5, and intraepidermal nerve fibers (IENF) were quantified manually by light microscopy. IENFD was compared between groups with different glucose tolerance and related to neurophysiological tests, including nerve conduction study (NCS; sural and peroneal nerve), quantitative sensory testing (QST), and clinical examination (Total Neuropathy Score; Neuropathy Symptom Score and Neuropathy Disability Score).

RESULTS

Absent IENF was seen in subjects with T2DM (n = 10; 21%) and IGT (n = 1; 7%) but not in NGT. IENFD correlated weakly negatively with HbA1c (r = -.268, P = .013) and Total Neuropathy Score (r = -.219, P = .042). Positive correlations were found between IENFD and sural nerve amplitude (r = .371, P = .001) as well as conduction velocity of both the sural (r = .241, P = .029) and peroneal nerve (r = .258, P = .018). Proportions of abnormal sural nerve amplitude became significantly higher with decreasing IENFD. No correlation was found with QST. Inter-rater reliability of IENFD assessment was good (ICC = 0.887).

CONCLUSIONS

Signs of neuropathy are becoming more prevalent with decreasing IENFD. IENFD can be meaningfully evaluated in thin histopathological sections using the presented technique to detect neuropathy.

Disturbed vibrotactile sense in finger pulps in patients with Type 1 diabetes--correlations with glycaemic level, clinical examination and electrophysiology

AIMS

In a cohort of men and women with Type 1 diabetes, prospectively followed for > 20 years, vibrotactile sense in fingers was investigated and related to neurophysiological tests, glycaemic level and clinical score.

METHODS

Out of 58 patients, diagnosed at the age of 15-25 years and recruited 1984-1985, 32 patients (13 women, median age 52 years, range 44-75 years; 19 men, median age 52 years, range 39-69 years; median duration 33.5 years, range 21-52 years) accepted follow-up in 2006. Vibration thresholds were measured in finger pulps of index and little fingers bilaterally at seven frequencies and related to results of touch (monofilaments), tactile discrimination (two-point discrimination test), electrophysiology (median nerve function), glycaemic level (HbA(1c) levels since 1984-1985) and a clinical score.

RESULTS

Vibrotactile sense was reduced in finger pulps, mainly in men, compared with an age- and gender-matched healthy control group with normal HbA(1c) . Vibration thresholds were increased, particularly at 250 and 500 Hz, in both index and little finger pulps. Touch and tactile discrimination correlated with vibration thresholds, but not with each other or with electrophysiology. HbA(1c) levels (at follow-up or mean values from five follow-ups since recruitment) did not correlate with any nerve function variables. Clinical scores correlated with vibrotactile sense, particularly at higher frequencies (> 125 Hz), but not with total Z-scores of electrophysiology. Duration of disease did not correlate with any variables.

CONCLUSIONS

Examination of vibration thresholds in index and little finger pulps may be valuable to detect neuropathy, where thresholds correlate with symptoms and tests.

Sural nerve biopsy may predict future nerve dysfunction

OBJECTIVE

Sural nerve pathology in peripheral neuropathy shows correlation with clinical findings and neurophysiological tests. The aim was to investigate progression of nerve dysfunction over time in relation to a baseline nerve biopsy.

METHODS

Baseline myelinated nerve fiber density (MNFD) was assessed in sural nerve biopsies from 10 men with type 2 diabetes, 10 with impaired and 10 with normal glucose tolerance. Nerve conduction and quantitative perception thresholds were estimated at baseline and follow-up (7-10 years later).

RESULTS

Subjects with low MNFD (< or = 4700 fibers/mm(2)) showed decline of peroneal amplitude (P < 0.02) and conduction velocity (P < 0.04), as well as median nerve sensory amplitude (P < 0.05) and motor conduction velocity (P < 0.04) from baseline to follow-up. In linear regression analyses, diabetes influenced decline of nerve conduction. MNFD correlated negatively with body mass index (r = -0.469; P < 0.02).

CONCLUSION

Low MNFD may predict progression of neurophysiological dysfunction and links obesity to myelinated nerve fiber loss.

Sorbitol and myo-inositol levels and morphology of sural nerve in relation to peripheral nerve function and clinical neuropathy in men with diabetic, impaired, and normal glucose tolerance

AIMS

Sorbitol and myo-inositol levels and morphology of sural nerve were compared with nerve function and clinical neuropathy in men with diabetic, impaired (IGT), and normal glucose tolerance.

METHODS

After neurography of sural nerve and determinations of sensory thresholds for vibration, warm and cold on the foot, whole nerve sural nerve biopsy was performed in 10 men with Type 1 diabetes mellitus, 10 with IGT, and 10 with normal glucose tolerance. Polyol levels were assessed by gas-liquid chromatography/mass spectrometry.

RESULTS

Sural nerve amplitudes were significantly lower and sorbitol levels significantly higher in diabetic patients (median (interquartile range)) (3.7 (3.5) microV and 643 (412) pmol/mg protein, respectively) both compared with IGT (11.3 (10.6)microV; P = 0.04 and 286 (83) pmol/mg protein; P = 0.0032, respectively) and normally glucose tolerant (10.0 (11.6); P = 0.0142 and 296 (250) pmol/mg protein; P = 0.0191, respectively) subjects. There were no differences in nerve morphology between the three groups. Nerve myo-inositol levels correlated, however, positively with cluster density (rs = 0.56; P = 0.0054). In diabetic and IGT subjects, sural nerve amplitudes (2.6 (3.8) vs. 12.1 (10.6) microV; P = 0.0246) and myelinated nerve fibre density (MNFD; 4,076 (1091) vs. 5,219 (668) nerve fibres/mm2; P = 0.0021) were significantly lower in nine subjects with clinical neuropathy than in 10 without.

CONCLUSIONS

Nerve degeneration (i.e. MNFD) correlated with clinical neuropathy but not with glucose tolerance status whereas nerve myo-inositol levels positively correlated with signs of nerve regeneration (i.e. increased cluster density).

Autonomic neuropathy in Type 2 diabetic patients is associated with hyperinsulinaemia and hypertriglyceridaemia

AIMS

To clarify whether parasympathetic neuropathy in Type 2 diabetic patients is associated with features of the insulin resistance syndrome.

METHODS

Blood pressures, glycaemic control (HbA1c), plasma lipids, residual beta-cell function (fasting plasma C-peptide), autonomic nerve function, urinary albumin excretion and glomerular filtration rate (Cr-EDTA clearance) were evaluated in 82 Type 2 diabetic patients (age 63+/-years) 5 years after diagnosis of diabetes.

RESULTS

Parasympathetic neuropathy (an abnormal age corrected E/I ratio) was found in 24/82 (29%) patients. After adjustment for body mass index (BMI), patients with parasympathetic neuropathy had elevated fasting plasma C-peptide (P < 0.001) and triglyceride (Tg) (P < 0.05) levels compared with patients without parasympathetic neuropathy. In addition, the age corrected E/I ratio correlated inversely with Tg (r=-0.31; P<0.01) and fasting plasma C-peptide (r=-0.32; P < 0.01) in the Type 2 diabetic patients.

CONCLUSION

Autonomic neuropathy 5 years after diagnosis of Type 2 diabetes is associated with an unfavourable metabolic risk profile.

Metabolic neuropathies

A large epidemiological study has documented that one-third of diabetic patients have peripheral neuropathy. Diabetes duration, poor glycaemic control, smoking and hypertension are all independent predictors of the incidence of diabetic polyneuropathy. High prevalence of autonomic dysfunctions, both sympathetic and parasympathetic, has been found in patients with nonalcoholic chronic liver disease. The pathogenesis of metabolic neuropathy is unclear; even immunologic factors might play a role in the development of diabetic autonomic neuropathy. No specific treatments are available for these neuropathies. Correction of metabolic derangement is fundamental, as shown by the amelioration of peripheral nerve function obtained after successful simultaneous pancreas-kidney transplantation. The therapeuthic potentials of neurotrophins for the prevention and treatment of diabetic neuropathy have to be confirmed in future studies.