Serum levels of unbound free fatty acids. I: Normative data in term newborn infants.
BACKGROUND: Free fatty acids (FFA) play essential roles in maintaining physiologic homeostasis in the newborn infant. Most of the FFA in serum is carried in complex with albumin, but a small fraction remains unbound in the aqueous phase. OBJECTIVE: This study's goal is to report the values of serum levels of unbound free fatty acids (FFAu) in pregnant women and their newborn infants at term gestation. METHODS: The measurements were made possible by the availability of the fluorescent probe for unbound FFA, acrylodated intestinal fatty acid binding protein (ADIFAB). Twenty-two mother-infant pairs were enrolled in the study. Maternal levels were obtained immediately before delivery, cord levels at the time of delivery, and infant levels after 24 hours of age. RESULTS: The level of FFAu measured in maternal samples was 11.8 +/- 4 nM, in cord samples 9.2 +/- 4 nM, and in infants 13.9 +/- 3 nM. These population averages are considerably greater than those observed in healthy adults (7.5 +/- 2.5 nM). No correlation was found between cord levels and birthweight, gestational age, labor duration, mode of deliver, and infant or maternal temperature. CONCLUSIONS: This investigation is the first to measure FFAu in a group of mothers and their infants and provides the technique for future investigations of the biologic activity of free fatty acids.