PLASMA-CHOLESTEROL AND LATHOSTEROL LEVELS IN TERM INFANTS IN THE EARLY NEONATAL-PERIOD

Plasma cholesterol concentrations increase after birth. Whether this is due to increased cholesterol synthesis has not been reported. Additionally, it is not known if formulas, which lack cholesterol, result in higher rates of cholesterol synthesis than feeding breast milk. To address this, plasma lathosterol (quantitated by gas chromatography), a potential indicator of cholesterol synthesis, was measured in term infants at birth (cord) and 4 d of age fed either formula or breast milk (n = 6 each), normal adults (n = 6) at the expected nadir and peak of the diurnal rhythm (1700 h and 0830 h), and cholestyramine-treated hypercholesterolemic adults (n = 6). Plasma cholesterol and apo B increased, and apo AI (measured by immunoprecipitation) did not change over the first 4 d of life. The increase in plasma cholesterol was greater in the formula-fed infants compared within breast-fed infants. The plasma lathosterol concentrations (mu-mol/L) and the lathosterol: cholesterol ratios (10(2) X mmol lathosterol/mol cholesterol) decreased from birth to 4 d of age by 12 and 36%, respectively, in the breast-fed infants and by 20 and 46%, respectively, in formula-fed infants. The infant plasma lathosterol concentrations, however, were not different from normal adult levels [1700 h: 5.50 +/- 1.52 (SD); 0830 h: 6.18 +/- 1.801, but were lower than those of cholestyramine-treated adults (20.48 +/- 13.41). Sterol ratios of infants were higher than those of normal adults (1700 h: 112.5 +/- 26.0; 0830 h: 129.4 +/- 42.2), but not different from those of cholestyramine-treated adults (322.9 +/- 168.4). These data show that the evaluation in plasma cholesterol between birth and d 4 of age is not accompanied by increased plasma lathosterol levels, suggesting no increase in cholesterol synthesis. Further, infants fed formula do not have greater plasma lathosterol levels than breast-fed infants.