Bile Salt Metabolism in Infants and Children after Protracted Infantile Diarrhea

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Abstract
Summary: Ten infants and children (mean age, 44 months), who had recovered from protracted infantile diarrhea with no sequelae, underwent detailed investigations of cholate metabolism using the isotope dilution technique. Cholate pool size was 1011 ± 73 mg/m2, (x ± S.E.), synthetic rate was 358 ± 58 mg/m2/day, and the fractional turnover rate was 0.359 ± 0.049 days-1. Pool size, unconnected for body surface area differences, was shown to increase directly with body size (r = 0.827; P = 0.002) and age (r = 0.724; P = 0.009). The fractional turnover rate varied inversely with age (r −0.656; P = 0.02), surface area (r = −0.642; P = 0.023), and pool size (r = −0.703; P = 0.012) and directly with synthesis (r = 0.878; P < 0.001). Infants and children have an intact enterohepatic circulation of cholate; the pool size and the mechanisms which regulate synthesis are similar to adults. The progressive enlargement of pool size with age is associated with an age-related increase in intraluminal bile salt concentrations which ensures normal intraluminal fat digestion and solubilization. Speculation: At birth, term and premature infants have contracted primary bile salt pools which contribute to the observed steatorrhea of the newborn. Rapid expansion of the cholic acid pool size in the first months of life demonstrated in the present study increases intraluminal bile salt concentrations which facilitates intraluminal fat digestion, but the mechanisms modulating the expansion in the neonate have been largely unexplored. Pool enlargement and enhanced fecal sterol excretion may be a homeostatic response of the developing organism to rising serum and hepatic cholesterol concentrations.