Fasting Blood Lipid Responses to Aerobic Exercise and Niacin Therapy in Men with Metabolic Syndrome

Abstract

Both aerobic exercise and niacin therapy have been shown to be effective means for reducing triglyceride concentrations. Because these lipid lowering interventions appear to work through similar and separate biochemical pathways, their combination may potentiate or dampen the independent lipid lowering effects of either strategy alone. PURPOSE: Our purpose was to compare the fasting blood lipid response to aerobic exercise before and after 6 wks of niacin therapy in men with metabolic syndrome. METHODS: Fifteen men with the metabolic syndrome (46 + 2 yrs of age; BMI = 34.0 + 0.8 kg/m2; waist circumference = 107.9 + 2.1 cm; HOMA score = 4.3 + 0.5; triglycerides = 286 + 26 and HDL-C =40 + 2 mg/dL; % fat =35 + 5; VO2max = 27.7 +5.1 mL.min-1.kg-1) expended 500 kcals by walking on a treadmill at 65% of VO2max before and after a 6-wk regimen of prescription niacin. Niacin doses were titrated by 500 mg/wk from 500 to 1500 mg/dy and maintained at 1500 mg/dy for the last 4 wks. Fasting blood samples were obtained prior to, 24 and 48 hrs after exercise. Differences in serum triglyceride, glucose and insulin concentrations and clinical indices of insulin sensitivity (HOMA and glucose/insulin ratio) were determined by multiple 2 (condition) by 3 (time) repeated-measures ANOVAs (p < 0.05 for all significant differences). RESULTS: Body weights remained stable over the experimental period. Triglyceride concentrations were reduced by 15% and 27% at 24 and 48 hrs post-exercise. Niacin lowered baseline triglycerides by 34% but attenuated the triglyceride-lowering effect of exercise. Glucose concentrations did not change with exercise alone but after 6-wks of niacin increased 10% above baseline values 24 and 48 hrs post-exercise. Insulin concentrations and the HOMA scores were 21 and 23% higher and the glucose/insulin ratio was 21% lower after niacin; however, these variables were not altered by exercise. CONCLUSIONS: A single session of aerobic exercise transiently reduced fasting triglycerides to the same degree as 6 wks of niacin therapy. However, the niacin-mediated reductions in fasting triglycerides and clinical markers of insulin sensitivity appear to attenuate the short-term triglyceride lowering effect of a single exercise session in physic ally-inactive men with metabolic syndrome.