Effect of decreased gallbladder stimulation on enterohepatic cycling and kinetics of bile acids.

The effect of diet on the rate of enterohepatic recycling and bile acid kinetics was studied in groups of human subjects by reducing dietary protein and fat. The effect on enterohepatic cycling was assessed indirectly in control subjects, in patients with cholesterol cholelithiasis, and in patients with cholecystectomy by comparing output of breath 14-CO2 after the administration of a trace of cholyl [1-14-C]glycine during two periods: a control period when three meals containing protein and fat were eaten daily and a diet period, when protein and fat were excluded from the diet. Breath 14-CO2 output was not altered by diet in the patients with cholecystectomy. In the healthy subjects and in the patients with cholesterol cholelithiasis breath 14-CO2 output fell by approximately 50%, indicating that decreased endogenous cholecystokinin-pancreozymin stimulation had reduced but not eliminated enterohepatic recycling. Bile acid kinetics after administration of [2,4-3-H]cholic acid and [24-14-C]chenodeoxycholic acid were measured in 6 healthy subjects during a control period, when they ate a diet containing three daily meals containing fat and protein, and again not less than 4 months later during the 4th week of a diet during which they ate only one meal containing fat and protein every other day. tthe pool size of cholic and chenodeoxycholic acid rose significantly during the diet as did the total bile acid pool size. The daily fractional turnover rate of both primary bile acids fell significantly during the diet, but their synthesis rate was not significantly changed. It is concluded that (1) significant enterohepatic circulation of bile acids occurs even in the absence of dietary stimuli for gallbladder contraction; and (2) diet may significantly affect bile acid pool size and fractional turnover, while bile acid synthesis remains essentially unchanged.