The Effects of Aerobic Exercise and Extended-Release Niacin on Fasting and Postprandial Blood Lipids

Abstract

The primary purpose of this investigation was to compare the combined effects of aerobic exercise and extended-release niacin on fasting and postprandial lipemia. Fifteen men with the metabolic syndrome (Age = 46 ± 2; BMI = 34.0 ± 0.8 kg?m-2; Waist circumference = 107.9 ± 2.1 cm; HOMA score = 4.3 ± 0.5; Triglycerides = 286 ± 26; HDL-C = 40 ± 2; Systolic blood pressure = 130 ± 4; Diastolic blood pressure = 84 ± 2) underwent each of four conditions (control: high-fat meal only; exercise: exercise performed one hour prior to a high-fat meal; niacin: high-fat meal consumed after six weeks of extended-release niacin; niacin + exercise: high-fat meal consumed after six weeks of extended-release niacin and a single session of exercise) to determine the effects of niacin and exercise on postprandial lipemia. Blood samples were obtained on each occasion at baseline and at two-hour intervals up to eight hours following the high-fat meal. Fasting blood samples were also obtained before and again at 24 and 48 hours post-exercise during the exercise and niacin + exercise conditions to determine the combined effects of niacin and exercise on fasting triglyceride and glucose metabolism. Blood samples were analyzed for triglyceride, glucose and insulin concentrations. Area under the curve was calculated for triglyceride and insulin during the postprandial period. Differences in blood variables of interest were determined by multiple repeated-measures ANOVAs (p < 0.05 for all). Niacin + exercise lowered the postprandial total triglyceride area under the curve and temporal responses to a greater extent than exercise alone. The incremental triglyceride area under the curve and temporal responses were similar to control in the niacin + exercise condition. Insulin concentrations in the niacin condition were increased by 54% compared to control at the two-hour postprandial timepoint and were reduced by 16% when exercise was combined with niacin. Baseline fasting triglycerides were correlated with the total triglyceride area under the curve for each condition. Fasting triglycerides were reduced by 15% and 27% twenty-four and 48 hours following exercise. Six weeks of niacin lowered fasting triglycerides by 37%; however, fasting triglycerides were not reduced further when an identical exercise session was performed immediately following the niacin intervention. These findings indicate an additive influence of niacin and exercise on postprandial lipemia that may be mediated in similar and distinctly different ways. Furthermore, niacin-mediated reductions in fasting triglycerides may attenuate the triglyceride lowering effect of exercise.