In newborn adipocytes, the oxidation and esterification of [14C]palmitate was increased after addition of L-carnitine and decreased after addition of deoxycarnitine, a carnitine acyltransferase inhibitor. In adult cells, the oxidation of [14C]palmitate was higher and the esterification of [14C]palmitate was lower compared to newborn adipocytes. There was no change in either oxidation or esterification after incubation with L-carnitine or deoxycarnitine. Comparing samples obtained during the first day of life with those from newborns older than 30 hr, there was an increase in acid-soluble and acid-insoluble carnitine content. Acid-insoluble carnitine levels were higher in adults than in newborns. Carnitine palmitoyltransferase activity increased in white adipose tissue mitochondria of normal fullterm infants after 20 yr of age. Longitudinal measurements at different ages showed a constant individual blood level of free carnitine after birth. In human breast milk, the total carnitine content increased during the first week postpartum. After 1 month of lactation, the values declined to those of milk samples obtained during the first 3 days postpartum. Commercial milk formulas with a cow's milk base had a similar or higher carnitine content than human milk. However, formulas with a soybean base had no detectable carnitine. Speculation: Carnitine is accumulated in human newborn adipose tissue shortly after birth and increases the utilization of fatty acids for energy requiring processes. It remains to be established whether reduced oral intake of carnitine will adversely affect energy production or whether carnitine administration will be of benefit, particularly in the low birthweight infant.
ASJC Scopus subject areas
- Pediatrics, Perinatology, and Child Health