Insulin therapy improves endothelial function in type 2 diabetes

Abstract

A total of 75 in vivo endothelial function tests (intrabrachial artery infusions of endothelium-dependent [acetylcholine] and -independent [sodium nitroprusside] vasoactive agents) were performed in 18 type 2 diabetic patients (aged 58±2 years, body mass index 28.5±0.6 kg/m2, and fasting plasma glucose 229±11 mg/dL) and 27 matched normal subjects. These tests were performed before and 6 months after combination therapy with insulin and metformin and before and 6 months after metformin therapy only. Before insulin therapy, blood flow responses to acetylcholine (15 μg/min) were significantly blunted in type 2 diabetic patients (7.5±0.7 mL·dL-1 min-1) compared with normal subjects (11.6±0.9 mL·dL-1·min-1, P<0.01). During insulin therapy, the acetylcholine response increased by 44% to 10.8± 1.6 mL·dL-1·min-1 (P<0.05). Insulin therapy also significantly increased the blood flow responses to both low and high doses of sodium nitroprusside. We conclude that insulin therapy improves endothelium- dependent and -independent vasodilatation. These data support the idea that insulin therapy has beneficial rather than harmful effects on vascular function.