Insulin Therapy Improves Endothelial Function in Type 2 Diabetes

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 5862 years, body mass index 28.560.6 kg/m 2 , and fasting plasma glucose 229611 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 mg/min) were significantly blunted in type 2 diabetic patients (7.5 60.7 mL z dL 21 z min 21 ) compared with normal subjects (11.660.9 mL z dL 21 z min 21 , P,0.01). During insulin therapy, the acetylcholine response increased by 44% to 10.861.6 mL z dL 21 z min 21 (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. (Arterioscler Thromb Vasc Biol. 2000;20:545-550.)