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−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.