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

OBJECTIVE - 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). RESEARCH DESIGN AND METHODS - The axon reflex-elicited flare areas (LDI-flares) 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). RESULTS - The flare area was reduced in the IGT group compared with the control (2.78 ± 1.1 vs. 5.23 ± 1.7 cm², P = 0.0001) and type 1 diabetic (5.16 ± 2.3 cm², P = 0.002) groups, whereas the flare area was similar in the type 1 diabetic and control groups. CONCLUSIONS - 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.