Redistribution of sudomotor responses is an early sign of sympathetic dysfunction in type 1 diabetes

Patients with diabetic neuropathy typically have decreased sweating in the feet but excessive sweating in the upper body. Previous studies of sudomoto r function in diabetes ha ce included patients with longstanding disease. T he present study was designed to test for the early presence of sudomotor d ysfunction and to characterize its relation to glycemic control and other a spects of peripheral nerve function. A total of 37 patients (10 males, 27 f emales) enrolled in a longitudinal study in which autonomic function was ev aluated annually for 3 years. Patients enrolled 2-22 months after the diagn osis of type 1 diabetes. Forty-one age- and sex-matched healthy control sub jects were also studied. Sweat production in response to acetylcholine stim ulation was dramatically increased in the forearm at the time of the first evaluation (1.67 +/- 0.24 mul/cm(2) in the diabetic patients vs. 1.04 +/- 0 .14 mul/cm(2) in the control subjects, P < 0.05). Likewise, the ratio of sw eating in the forearm to sweating below the waist was higher in the diabeti c patients (0.553 +/- 0.07 <mu>l/cm(2)) than in the control subjects (0.385 +/- 0.04 mul/cm(2), P < 0.05). Forearm sweat was negatively associated wit h the renin-to-prorenin ratio and vanillylmandelic acid (VMA) excretion (P < 0.025), tests of sympathetic nerve function. The ratio of sweating in the forearm to sweating in the foot was likewise increased in diabetic patient s with poor glycemic control. We interpret this redistribution of sudomotor responses to be indicative of sympathetic nerve injury and conclude 1) tha t the sympathetic nervous system is especially vulnerable to the adverse ef fects of chronic hyperglycemia and 2) that sympathetic dysfunction can be d etected very early in type 1 diabetes.