Leptin levels in preterm human breast milk and infant formula

Objective. Leptin, a hormone present in breast milk, is involved in energy regulation and metabolism. The purpose of this investigation was to determi ne whether leptin is present in either preterm breast milk (PBM) or preterm formula (PF). The effects of delivery methods and pasteurization on leptin levels also were evaluated. Methods. PBM samples were obtained from 29 mothers who delivered infants at between 23 and 34 weeks' gestation. Leptin levels were measured in PBM and PF with the use of a radioimmunoassay specific for human and bovine leptin , respectively. Milk samples were pasteurized by fast- and slow-heating met hods. PBM and PF spiked with human leptin were delivered through catheters by bolus and continuous administration to determine the effects of delivery method on recoverable leptin levels. Results. Median PBM leptin concentration was 5.28 ng/mL (intraquartile rang e: 24.79). Birth gestational age, birth weight, and gender of the infant di d not significantly influence PBM leptin levels. Neither bolus nor continuo us feeding practices affected leptin levels in PBM or spiked PF. However, p asteurization significantly reduced the amount of detectable leptin in PBM. Conclusions. PBM leptin levels were highly variable and similar to levels r eported for term breast milk. There was no effect of postnatal age on PBM l eptin concentrations. Sterilization decreased detectable leptin levels, whe reas feeding practices had no adverse effect on the quantity of leptin deli vered. Although no infant formula contained leptin, leptin could be added t o formula and delivered through various feeding methods without loss.