Influence of exercise on chylomicron triacylglycerol metabolism

Triacylglycerides (TG), circulating in chylomicrons, represent a potentially rich source of plasma substrates available for tissue uptake. Chylomicron TG are first hydrolyzed by the action of lipoprotein lipase prior to tissue uptake of the TG-derived fatty acids. Although the removal of these TG by fat cells appears to favor a storage function, uptake by skeletal muscle accounts for a significant portion of the TG removed from plasma. Further, uptake of TG-derived fatty acids by skeletal muscle is increased during exercise. This could contribute to an increased rate constant for TG removal from the plasma during exercise. A significant portion of the TG-derived fatty acids that enter muscle during exercise remain in the non-esterified fatty acid pool of the muscle where they could provide a substrate for beta-oxidation. Indirect estimates of the contribution that TG-derived fatty acids may make to the total energy costs during exercise in a fasting condition may be minor. However, appropriate direct measurements during a postprandial condition, where total plasma TG turnover is very large, have not been made.