Background: Although the metabolic effects of the thiazolidinediones have been well studied, there is a lack of comparative data on their effects on certain cardiovascular risk factors, such as elevated plasma levels of lipoprotein (a) (Lp[a]) and homocysteine (Hcy).
Objective: This study compared the effects of pioglitazone or rosiglitazone added to glimepiride on a range of lipid parameters, focusing on Lp(a) and Hcy, in patients with type 2 diabetes mellitus and the metabolic syndrome.
Methods: This was a multicenter, randomized, controlled, double-blind study in patients with type 2 diabetes and the metabolic syndrome (hypertension [>or=130/85 mm Hg]) and triglyceridemia (>or=150 mg/dL). In addition to glimepiride 4 mg/d, patients received pioglitazone 15 mg QD or rosiglitazone 4 mg QD for 1 year. The primary efficacy variables were change from baseline in body mass index (BMI), glycosylated hemoglobin (HbA(1c)), Lp(a), and Hey. Secondary efficacy measures were changes in fasting plasma glucose (FPG) and postprandial plasma glucose (PPG) concentrations, fasting and postprandial insulin concentrations (FPI and PPI, respectively), the Homeostasis Model Assessment index, and the lipid profile (total cholesterol [TC], low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein cholesterol [HDL-C], and triglycerides). All these parameters were measured after a 12-hour fast every 3 months for 1 year. Tolerability was assessed based on reported adverse events and laboratory abnormalities at each study visit.
Results: Ninety-one white patients with type 2 diabetes and the metabolic syndrome were enrolled, and 87 completed the study (43 men, 44 women; mean [SD] age, 53 [6] years; mean weight, 68.4 [3.3] kg). Mean baseline values for BMI and HbA(1c) were 24.3 (0.8) kg/m(2) and 8.1 % (0.8 %), respectively. At the end of 1 year, both treatment groups had significant increases from baseline in BMI (4.9% glimepiride + pio glitazone, 6.2% glimepiride + rosiglitazone; P < 0.05). Glimepiride + pioglitazone was associated with the following percent improvements from baseline in measures of glycemic control: -17.1% in HbA(1c), -19.3% in FPG, -17.8% in PPG, -40.1% in FPI, and -22.6% in PPI (all, P < 0.01). The corresponding percent improvements from baseline with glimepiride + rosiglitazone were -16.3%, -19.9%, -15.0%, -44.8%, and -22.1% (all, P < 0.01). There were no significant differences between treatment groups in any of these parameters. The pioglitazone group had significant improvements from baseline in TC (-11.1%), LDL-C (-12.0%), HDL-C (15.0%), and triglycerides (-22.4%) [corrected] (all, P < 0.05), whereas the rosiglitazone group had significant increases in TC (14.9%), LDL-C (16.5%), and triglycerides (17.9%) (all, P < 0.05); the difference between pioglitazone and rosiglitazone was statistically significant (P < 0.05). The change from baseline in Lp(a) was significant in the pioglitazone group, both relative to baseline and compared with the rosiglitazone group (-19.7% vs 0.5%, respectively; P < 0.05 vs baseline and vs rosiglitazone). Changes from baseline in Hey were significant in both the pioglitazone and rosiglitazone groups (-20.2% and -25.0%, respectively; P < 0.05), with no significant difference between groups. Both treatments were well tolerated, and no patients had significant changes in transaminases.
Conclusions: In these patients with type 2 diabetes and the metabolic syndrome, the combinations of glimepiride with pioglitazone and glimepiride with rosiglitazone produced significant improvements in measures of glycemic control, plasma lipids, and homocysteinemia. One year of treatment with the pioglitazone combination was associated with significantly reduced plasma Lp(a) levels compared with the rosiglitazone combination.