Pioglitazone vs glimepiride: Differential effects on vascular endothelial function in patients with type 2 diabetes

ObjectiveThe aim of this study was to compare the effect of glimepiride and pioglitazone on endothelial function in patients with type 2 diabetes already on metformin.MethodsTwenty-eight patients with type 2 diabetes already on metformin, without known cardiovascular disease, were randomized in 2 groups; glimepiride (4 mg od) was added in group A (n = 14) and pioglitazone (30 mg od) in group B (n = 14) for 6 months. Flow-mediated dilation (FMD) in the brachial artery was assessed in all patients, at baseline and at follow-up.ResultsThe 2 groups did not differ in age (mean ± S.D., 63.6 ± 7.3 years vs 62.8 ± 7.2 years respectively), or any measured variable at baseline. Fasting glucose and glycated haemoglobin improved similarly in both groups. There were significant differences between the 2 groups in the absolute changes observed at follow-up in waist circumference, +1.86 ± 3.11 cm vs −1.86 ± 1.88 cm in groups A and B respectively; fasting insulin levels, +14.79 ± 12.56 pmol/L vs −25.84 ± 28.09 pmol/L; homeostasis model assessment (HOMA), +0.66 ± 1.01 vs −1.83 ± 1.38; HDL cholesterol levels, −0.07 ± 0.22 mmol/L vs +0.14 ± 0.20 mmol/L and FMD, +0.14 ± 1.09% vs +2.02 ± 2.05% (p < 0.05 for all). The only independent predictor factor of the FMD improvement was treatment-induced changes in HOMA (R2: 0.488, slope: −0.782, [95% CI: −1.128, −0.436], p = 0.0001).ConclusionsIn patients with type 2 diabetes already on metformin, addition of pioglitazone as compared to glimepiride, improved endothelial function despite similar glycemic control. The improvement in endothelial function was mainly due to a reduction in insulin resistance.