Postprandial lipemia and endothelial function in active and sedentary males
Winters, Julie L.
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Cardiovascular diseases (CVD) are one of the leading causes of death in the United States. Well known risk factors for CVD are smoking, family history, high blood pressure, weight, sedentary lifestyle and lipid profile . The CVD risk associated with postprandial lipemia (high circulating levels of plasma lipids after a meal) has not been well documented. We spend most of our day in the postprandial state with high plasma lipids that can cause damage to blood vessels over time. Postprandial lipemia is an emerging risk factor for CVD and the potential impact on CVD can be assessed by measuring endothelial function's response to a meal that is high in fat content. The purpose of this study was to examine the effect of postprandial lipemia on endothelial function in active and sedentary men without the influence of a recent bout of exercise. Male subjects were recruited into two groups based on fitness (VO 2 peak) determined by cycle ergometry (high and low VO 2 peak values). They had to also be healthy, normotensive, normocholesterolemic, non-obese and non-smokers. Nine active and eight sedentary males (18-38 yr old with average VO 2 peaks 64.1 and 39.4 mL/kg/min, respectively) drank a high fat dairy shake after a 12 h fast and 36 h of physical inactivity. Blood was collected to measure the lipemic response and brachial artery flow mediated dilation (FMD) was determined by b-mode ultrasound at 0, 3 and 6h. Serum glucose remained stable (84.7±0.9 mg/dL, mean of all subjects) but non-esterified fatty acids increased in both groups over time by (0.31±0.04, 0.61±0.05, 0.70±0.05 mmol/L at 0, 3 and 6 h respectively). In both groups, triglycerides (TG) were highest at 3 h, TG did decline but not to fasting levels after 6 h. No statistical difference in serum TG was observed (TG: Active 70.1±11.1, 104.2±15.1, 85.9±14.3 mg/dL vs. Sedentary 67.1±7.8, 119.5±10.7, 85.8±11.0 mg/dL at 0, 3 and 6 h respectively p<0.05). Baseline brachial diameter at 0 h was significantly larger in the active group (4.9± 0.1mm Active, 4.1± 0.1 mm Sedentary). Percent FMD increased in both groups after 3 h, the only statistical difference, between groups was at 6 hours the active group percent FMD declined and the sedentary percent FMD increased. However when adjusted for age and baseline diameter there was no statistical difference between percent FMD between the groups over time. Since baseline diameter was significantly larger in the active group, it may be suggested that vessel diameter increases with training. This larger vessel size may be the reason no difference was seen between the active and sedentary groups. It is also possible that there was no significant difference in percent FMD, because the sedentary group was younger age and lacked the known CVD risk factors. Studies on postprandial lipemia and endothelial function may need to control for recent exercise, as differences in fitness level did not alter postprandial lipemia or endothelial function in this study, as has been seen in other studies that did not restrict activity. After 36 h of inactivity and a 12 h fast, no difference was seen in postprandial lipemia or endothelial function between chronically physically active and sedentary individuals when adjusted for age and baseline diameter. Peak TG, measured at 3h, was not different between active and sedentary; and TG levels had no relationship to endothelial function.