Fasting blood lipid responses to aerobic exercise and niacin therapy in men with metabolic syndrome

Abstract

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.