PREWEANING DIET AFFECTS BILE LIPID-COMPOSITION AND BILE-ACID KINETICSIN INFANT BABOONS

We tested, with 14-wk-old baboons before weaning, the hypothesis that bile acid metabolism is differentially affected by breast feeding or b y feeding formulas with a high polyunsaturated:saturated fatty acid ra tio or with a low ratio, similar to that of breast milk. Bile lipid co ntent, bile acid pool size, fractional turnover rate, synthetic rate a nd conjugate composition were measured in a single bile sample 9 d aft er an injection on d 1 of a mixture of [C-14]cholic and [C-14]chenodeo xycholic acids and an injection of a mixture of [H-3]cholic acid and [ H-3]chenodeoxycholic acid on d 8. The principal biliary bile acid was chenodeoxycholic acid. The only difference in chenodeoxycholic acid me tabolism among the infant diet groups was a lower chenodeoxycholic aci d synthetic rate in baboons fed the low polyunsaturated:saturated form ula compared with those fed the high polyunsaturated: saturated formul a or breast-fed. Cholic acid metabolism was significantly affected by infant diet: breast-fed infants had a smaller cholic acid pool size, l ower cholic acid percentage of total bile acids. higher cholic acid gl ycine:taurine conjugate ratio and larger cholic acid fractional turnov er rate than formula-fed animals. The polyunsaturated:saturated fatty acid ratio in the formulas did not significantly affect these variable s. These results show that differences in bile acid metabolism between breast- and formula-fed infant baboons are limited principally to cho lic acid. These differences likely are due to factors other than fatty acid saturation.