Sorbitol and myo-inositol levels and morphology of sural nerve in relationto 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 co mpared with nerve function and clinical neuropathy in men with diabetic, im paired (IGT), and normal glucose tolerance. Methods After neurography of sural nerve and determinations of sensory thre sholds for vibration, warm and cold on the foot, whole nerve sural nerve bi opsy was performed in 10 men with Type 1 diabetes mellitus, 10 with IGT, an d 10 with normal glucose tolerance. Polyol levels were assessed by gas-liqu id 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) mu V and 643 (412) pmol/mg protein, respectively) both compared w ith IGT (11.3 (10.6) mu V; P = 0.04 and 286 (83) pmol/mg protein; P = 0.003 2, 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-inos itol levels correlated, however, positively with cluster density (r(s) = 0. 56; P = 0.0054). In diabetic and IGT subjects, sural nerve amplitudes (2.6 (3.8) vs. 12.1 (10.6) mu V; P = 0.0246) and myelinated nerve fibre density (MNFD; 4076 (1091) vs. 5219 (668) nerve fibres/mm(2); P = 0.0021) were sign ificantly lower in nine subjects with clinical neuropathy than in 10 withou t. Conclusions Nerve degeneration (i.e. MNFD) correlated with clinical neuropa thy but not with glucose tolerance status whereas nerve myo-inositol levels positively correlated with signs of nerve regeneration (i.e. increased clu ster density).