Biliary lipid composition in healthy and diseased infants, children, and young adults

Biliary lipid composition and cholesterol saturation were measured in 17 infants and children (age, 4 mo to 9 yr) who had recovered from chronic diarrhea (control subjects), 9 infants and children (age, 4 mo to 9 yr) with interruption of the enterohepatic circulation of bile salts from birth, and in 20 healthy young adults (age, 21-35 yr). The cholesterol molar fraction in pediatric controls was 3.7 ± 0.2% (mean ± SE), and in patients with ileal dysfunction or resection was 3.4 ± 0.4%. Both values were significantly lower than that found in adults (5.7 ± 0.5%, p < 0.01). Cholesterol saturation, calculated using the method of Thomas and Hofmann, was significantly reduced in patients with ileal dysfunction or resection (0.60 ± 0.10; p < 0.01) and juvenile controls (0.72 ± 0.04; p < 0.05) compared with adults (1.08 ± 0.09). It appears that proportionately larger bile salt pools (adjusted to body size) in both pediatric groups compared with their normal and diseased adult counterparts contribute to the observed reduction in the biliary molar fraction of cholesterol and reduced cholesterol saturation. However, both normal and diseased infants and children primarily have reduced biliary cholesterol/bile salt excretion ratios such that, even at low rates of secretion, bile is not saturated with cholesterol. Therefore, age-related differences in biliary lipid secretory rates seem to produce unsaturated bile in both normal and diseased prepubertal humans.