Beneficial Effect of Troglitazone, an Insulin-Sensitizing Antidiabetic Agent, on Coronary Circulation in Patients With Non-Insulin-Dependent Diabetes Mellitus

Evidence is increasing for small vessel remodeling and disturbance of endothelium-dependent vasodilation in diabetic patients. Insulin increases vascular wall thickening and produces endothelial dysfunction. Troglitazone, a new insulin-sensitizer antidiabetic agent, is considered to reduce plasma insulin level and the present study assessed its effect on the coronary circulation of the patients with non-insulin-dependent diabetes mellitus (NIDDM). Analysis of the myocardial washout rate with adenosine triphosphate-stress thallium-201 scintigraphy was used to estimate coronary circulation, and for estimation of insulin sensitivity, the homeostasis model insulin resistance index (HOMA-R) was calculated. Patients were treated with monotherapy of either troglitazone (200 mg bid, n=12) or glibenclamide (2.5 mg daily, n=12) for 3 months. Age-, sex- and risk factors-matched subjects without NIDDM were employed as a control. Fasting plasma glucose and hemoglobin A1c were similarly decreased by troglitazone or glibenclamide. Plasma insulin level (pmol/L) decreased from 66.6+/-10.8 to 39.0+/-7.2 with troglitazone, but was unchanged by glibenclamide (58.8+/-7.2 to 66.0+/-10.8). The diabetic groups had a significantly lower washout rate than controls, which was improved by troglitazone, but not by glibenclamide. In addition, the increase in washout rate correlated significantly with the decrease in HOMA-R in the troglitazone group. In conclusion, troglitazone can restore coronary circulation by improving insulin resistance in patients with NIDDM.