Effect of physical exercise on bile and red blood cell lipids in humans

Abstract

Eleven young healthy men exercised on a bicycle ergometer for one hour with a duodenal collection tube in situ (workload 200 kilopond m/min, equivalent to walking one hour at 5.5 km/h). The duodenal fluid output and the biliary lipid output into duodenum were quantitated with a non-absorbable marker during 9 collection periods (30 min each). The sequence of control day (C) and exercise day (E) was randomly assigned. Compared with C, in the first 30 min of exercise the bile acid output (BA) and the cholesterol output (CH) significantly increased. BA: 242 ± 74 (C), 2,204 ± 913 (E), P < 0.05. CH: 19 ± 6 (C), 124 ± 48 (E), P < 0.05 (all values in μmol/30 min). This increase in bile acid output and in cholesterol output is probably caused primarily by a rise in BA and CH concentration in the bile. Cholesterol saturation of the bile showed a non-significant trend to a decrease during exercise. At the time when BA and CH in the bile were elevated, exercise reduced the red blood cell cholesterol: 8.68 ± 0.20 (C), 8.17 ± 0.32 (E), P < 0.03. Red blood cell phospholipids were also decreased: 8.81 ± 0.36 (C), 7.63 ± 0.50 (E), P < 0.02 (all values in μmol/g dry cell). Plasma cholesterol and phospholipids were not affected by exercise, even when expressed per unit protein. The exercise load used in this experiment did not induce emptying of the gallbladder visualized by oral ingestion of tyropanoate. Exercise required to promote changes in bile cholesterol, bile acids and peripheral cell lipids need not be strenuous. It probably acts by promoting the transport of lipids from the peripheral cells into the liver and by increasing hepatic secretion of bile. Exercise may be an important factor affecting the bile composition.