Altered C-fiber function as an indicator of early peripheral neuropathy in individuals with impaired glucose tolerance.

Abstract

This study explored the importance of glycemic burden compared with features of the metabolic syndrome in the pathogenesis of diabetic neuropathy by comparing C-fiber function in people with type 1 diabetes to that in people with impaired glucose tolerance (IGT). The axon reflex-elicited flare areas (LDIflares) were measured with a laser Doppler imager (LDI) in age-, height-, and BMI-matched groups with IGT (n = 14) and type 1 diabetes (n = 16) and in healthy control subjects (n = 16). The flare area was reduced in the IGT group compared with the control (2.78 +/- 1.1 vs. 5.23 +/- 1.7 cm(2), P = 0.0001) and type 1 diabetic (5.16 +/- 2.3 cm(2), P = 0.002) groups, whereas the flare area was similar in the type 1 diabetic and control groups. This technique suggests that small-fiber neuropathy is a feature of IGT. The absence of similar small-fiber neuropathy in those with longstanding type 1 diabetes suggests that glycemia may not be the major determinant of small-fiber neuropathy in IGT.