Effect of Long-term Physical Exercise on Bile Sterols, Fecal Fat and Fatty Acid Metabolism in Rats

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Abstract
Food consumption and fecal fat excretion do not explain the lower liver cholesterol repeatedly observed in exercising rats. Rats swimming 1 hour daily for 105 days were subjected to cannulation of the bile duct. After 24 hours' bile collection there was a significant drop in liver cholesterol in the trained animals only. These had a lower concentration and output of cholesterol in the bile, but the concentration of bile deoxycholic acid was higher than in controls. The amount of bile excreted in 24 hours, the concentration of cholic and the output of cholic and deoxycholic acid were not different. Fatty acid (FA) composition of epididymal fat triglycerides, liver triglycerides and liver cholesterol esters was studied in rats subjected to 118 days of swimming. Exercise had a pronounced effect on depot fat triglycerides FA, with higher levels of saturated FA, palmitate and stearate, with lower monoenes and polyenes. Liver triglyceride FA presented in exercising rats an inverse picture: lower saturated FA and palmitate, higher monoenes, oleate and polyenes. In liver cholesterol esters the exercised animals had higher proportions of linoleate and palmitate, lower oleate. A higher release of unsaturated FA from the depot fat in exercising animals is suggested, with higher levels of unsaturated FA in blood and liver. These may promote the transport and catabolism of cholesterol and so explain the lower liver cholesterol in exercising animals.