Impaired pressure-induced vasodilation at the foot in young adults with type 1 diabetes.
Vascular and neurological mechanisms are both likely to be involved in foot ulcer. We recently reported a pressure-induced vasodilation (PIV), relying on unmyelinated afferent excitation. We previously found that cutaneous blood flow in response to locally applied pressure might be impaired in diabetic patients because of the combined effects of low cutaneous temperature and alterations in microcirculatory function. Therefore, we aimed to analyze whether, at a relatively high cutaneous temperature, PIV is present in type 1 diabetes and to assess endothelial-dependent vasodilation and endothelium-independent vasodilation. We measured cutaneous blood flow using laser Doppler flowmetry on the head of the first metatarsus in response to applied pressure at 5.0 mmHg/min in warm conditions (29.5 +/- 0.2 degrees C). Responses to iontophoresis of acetylcholine (endothelium dependent) and sodium nitroprusside (endothelium independent) were measured using laser Doppler flowmetry in the forearm. The data indicate that PIV exists at the foot level in normal subjects, whereas it was not found in diabetic patients. In diabetic patients, the nonendothelial-mediated response to sodium nitroprusside was preserved, whereas the endothelial-mediated response to acetylcholine was impaired. These findings might be relevant to the high prevalence of foot ulcer that occurs in diabetic patients.