Influence of dietary cholesterol on vitamin d metabolism in formula-fed preterm neonates.

OBJECTIVES: Supplementation of preterm formulas with cholesterol could help to mimic the fat composition of human milk. However, this could possibly influence vitamin D 25-hydroxylation because this reaction is catalyzed in part by the mitochondrial cytochrome P-450, the enzyme responsible for the 27-hydroxylation of cholesterol. The purpose of this study was to verify whether the addition of cholesterol to preterm formulas could interfere with vitamin D metabolism in preterm neonates. METHODS: In a prospective study, 30 preterm neonates were randomly assigned to a low (< 0.03 g/L), medium (0.15 g/L), or high (0.30 g/L) cholesterol-content preterm formula until theoretical term (i.e., 40 weeks post-conceptional age). Anthropometric data and serum hydroxy-vitamin D and 1,25 dihydroxy-vitamin D concentrations were measured at study entry and theoretical term. In a subgroup of 14 subjects, serum cholesterol and lymphocyte 3-hydroxy-3-methylglutaryl coenzyme A reductase mRNA were also assessed. RESULTS: (median [25, 75 centiles]): At theoretical term, there were no significant differences in serum hydroxy-vitamin D concentrations among the three groups, even after adjustment for confounding variables (65 [50, 78] nmol/L, 79 [59, 86] nmol/L, and 67 [43, 103] nmol/L, respectively, = 0.65) or 1,25 dihydroxy-vitamin D ( = 0.88). Furthermore, there were no significant differences in 3-hydroxy-3-methylglutaryl coenzyme A reductase mRNA copy numbers. CONCLUSIONS: In preterm neonates fed formulas with a cholesterol content similar to or higher than that of human milk, we did not observe deleterious effects on vitamin D metabolism. However, long-term effects of cholesterol supplementation require further studies.

Nitrogen utilization and bone mineralization in very low birth weight infants fed partially hydrolyzed preterm formula.

Partialy hydrolyzed formulas have been proposed for term and preterm infants, but decreased nitrogen and calcium intestinal absorption rates, together with plasma amino acid imbalances have been reported in preterm infants. We evaluated a new formula with modified nitrogen and calcium sources (glycerophosphate). During their second week of life, 16 preterm infants were randomly assigned to 1 of 2 groups: 9 were fed the new partially hydrolyzed formula and 7 a conventional formula. A nutrient balance was performed at the end of the first month of life. Amino acid concentrations and whole-body mineralization were measured at the end of study period (theoretical term). Birth weight and gestational age (mean +/- SD) were similar in the 2 groups (28.9 +/- 7.0 wks and 1,183 +/- 242 g v 27.7 +/- 1.0 wks and 1,139 +/- 162 g). Median nitrogen absorption rate (85% v 89%; P = .03) was lower in infants fed the new formula than in those fed the conventional one. After correction for difference in nitrogen intake, there was no significant difference in N retained between the 2 groups (P = .11). Plasma amino acid concentrations were also similar in the 2 groups. At theoretical term, median bone mineral content was not significantly different between the 2 groups (50 g/kg v 55 g/kg; P = .17) and it was close to the reference values obtained in term neonates just after birth. As long as nitrogen content is 10% higher in protein hydrolyzed formula than in entire protein formula, appropriate nitrogen retention, plasma amino acid profile can be achieved with the new partially hydrolyzed formula. In both groups, bone mineralization at theoretical term was close to the mineralization observed term neonates just after birth.