Insulin sensitivity and sensory nerve function.

The central and peripheral nervous systems do not require insulin for glucose uptake. However, insulin receptors have been detected in these regions. The aim of this study was to examine peripheral sensory nerve function and its dependence on insulin using healthy non-diabetic control subjects, obese individuals, and diabetic (insulin dependent and non-insulin dependent diabetes mellitus) subjects. The results revealed that the warm and cold perception thresholds, reflecting the functional states of unmyelinated C-fibres and A-delta fibres respectively, increased with reduced insulin sensitivity and with increased fasting insulin concentrations. From such data in non-diabetic subjects with measured insulin sensitivity, it appeared that sensory nerve function was disturbed in normoglycemic but insulin resistant states, suggesting that insulin has an action on nervous tissue in addition to its effects on glucose metabolism. The mechanisms of this action remain to be elucidated.