Effects of prescription niacin and omega-3 fatty acids on lipids and vascular function in metabolic syndrome: a randomized controlled trial.

The metabolic syndrome includes both dyslipidemia and impaired vascular function. Because extended-release niacin (ERN) and prescription omega-3 acid ethyl-esters (P-OM3) independently improve these characteristics, we tested their effects in combination. Sixty metabolic syndrome subjects were randomized to 16 weeks of treatment on dual placebo, P-OM3 (4 g/day), ERN (2 g/day), or combination in a double-blind trial. Lipoprotein subfractions and vascular endpoints were measured and tested using ANCOVA. ERN increased HDL cholesterol by 5.4 mg/dl from baseline (P = 0.04), decreased triglycerides (TG) by 39 mg/dl (-21%, P = 0.003), and decreased the augmentation index, which is a measure of vascular stiffness, by 3.5 units (P = 0.04). P-OM3 reduced TG by 26 mg/dl (-13%, P = 0.04). Combination treatment increased HDL cholesterol by 7.8 mg/dl (P = 002) and decreased TG by 72 mg/dl (-34%) but there was no improvement in vascular stiffness. Detailed analysis of lipoprotein subfractions revealed increased large, bouyant HDL(2) (3.3 mg/dl; P = 0.002) and decreased VLDL(1+2) (-32%; P < 0.0001), among subjects treated with combination therapy, that were not present with either therapy alone. ERN and P-OM3 alone improved characteristics of metabolic syndrome; however, whereas subjects on combination therapy did not have improved vascular stiffness, TG and HDL levels improved as did certain lipoprotein subfractions.