Objective: To compare effects of different oral hypoglycemic drugs as first-line therapy on lipoprotein subfractions in type 2 diabetes.
Research design and methods: Sixty overweight type 2 diabetic patients not on lipid-lowering therapy were randomized to metformin, pioglitazone, or gliclazide after a 3-month dietary run-in. Drug doses were uptitrated for 3 months to optimize glycemia and were kept fixed for a further 3 months. LDL subfractions (LDL(1), LDL(2), and LDL(3)) were prepared by density gradient ultracentrifugation at randomization and study end. Triglycerides, cholesterol, total protein, and phospholipids were measured and mass of subfractions calculated. HDL subfractions were prepared by precipitation. The primary end point was change in proportion of LDL as LDL(3).
Results: HbA(1c), triglycerides, glucose, and cholesterol were comparable across groups at baseline and over time. LDL(3) mass and the LDL(3)-to-LDL ratio fell with pioglitazone (LDL(3) mass 36.2 to 28.0 mg/dl, P < 0.01; LDL(3)-to-LDL 19.2:13.3%, P < 0.01) and metformin (42.7 to 31.5 mg/dl, P < 0.01; 21.3:16.2%, P < 0.01, respectively) with no change on gliclazide. LDL(3) reductions were associated with reciprocal LDL(1) increases. Changes were independent of BMI, glycemic control, and triglycerides. Total HDL cholesterol increased on pioglitazone (1.28 to 1.36 mmol/l, P = 0.02) but not gliclazide (1.39 to 1.37 mmol/l, P = NS) or metformin (1.26 to 1.18 mmol/l, P = NS), largely due to an HDL(2) increase (0.3 to 0.4 mmol/l, P < 0.05). HDL(3) cholesterol fell on metformin (0.9 to 0.85 mmol/l, P < 0.01). On pioglitazone and metformin, the HDL(2)-to-HDL(3) ratio increased compared with no change on gliclazide.
Conclusions: For the same improvement in glycemic control, pioglitazone and metformin produce favorable changes in HDL and LDL subfractions compared with gliclazide in overweight type 2 diabetic patients. Such changes may be associated with reduced atherosclerosis risk and may inform the choice of initial oral hypoglycemic agent.