Impact of the metabolic syndrome on peripheral nerve structure and function in type 2 diabetes

BACKGROUND AND PURPOSE There is a strong association between the metabolic syndrome in diabetes and the development of peripheral neuropathy; however, the pathophysiological mechanisms remain unknown. METHODS Participants with type 2 diabetes and metabolic syndrome (T2DM/MetS, n = 89) and type 2 diabetes alone (T2DM; n = 59) underwent median nerve ultrasound and excitability studies to assess peripheral nerve structure and function. A subset of T2DM/MetS (n = 24) and T2DM (n = 22) participants underwent confocal microscopy to assess central and inferior whorl corneal nerve structure. Neuropathy severity was assessed using the modified Toronto Clinical Neuropathy Score (mTCNS). Diabetes groups were similar for age, sex distribution, diabetes duration, hemoglobin A1c , insulin treatment, and renal function. Sixty healthy controls similar for age and sex distribution were recruited for comparison. RESULTS Participants with T2DM/MetS manifested with a greater mTCNS compared to T2DM (p