Aim: Thiazolidinediones (TZDs) are insulin sensitizers used to improve glycaemic control in diabetic patients. TZDs have also been reported to improve endothelial function in obese patients with insulin resistance and in diabetic patients on oral treatment. However, little is known about the vascular effects of TZDs in patients with type 2 diabetes treated with insulin. The aim of this study was to assess the effect of rosiglitazone on endothelial function in type 2 diabetic patients treated with insulin.

Methods: Thirty-one diabetic patients without known coronary artery, cerebrovascular or peripheral arterial disease, who were already on an insulin regime, were randomized into 2 groups; no treatment was added in group A (n = 14), while rosiglitazone (4 mg od) was added in group B (n = 17) for 6 months. Flow-mediated dilation (FMD) in the brachial artery was assessed in all patients, at baseline and at follow-up.

Results: At baseline, the 2 groups did not differ in age (mean±SD, 67.3±6.4 vs 64.7±7.6 years, respectively, p=ns), or any measured variable. In group A there were no significant changes at 6 months in any variable except for diastolic blood pressure that dropped from 79±7 to 72±12 mmHg (p < 0.05). In group B, a significant reduction in glycated hemoglobin (from 8.8±1.1 to 7.8±1.0%, p < 0.0005) and in fasting plasma glucose (from 186±64 to 144±61 mg/dl, p < 0.05) was observed at 6 months, while FMD significantly improved (from 1.43±1.46 to 2.98±1.80%, p < 0.005).

Conclusions: In insulin-treated type 2 diabetic patients, treatment with rosiglitazone for 6 months has a beneficial effect on glycaemic control and endothelial function.