Abstract 1713 Poster Session I, Saturday, 5/1 (poster 126)

Leptin, the protein product of the ob gene, is integral in the body's system of energy regulation. Leptin has been found to be produced in the placenta, and to vary with newborn adiposity (Hassink et al, Pediatrics 100:e1-6, 1997). The premature infants may be leptin-deficient, due to early separation from the placenta, at a time when they have inadequate adipose tissue. Studies of the premature infant and the relationship of leptin concentrations and growth have not been performed in a longitudinal fashion. We measured leptin concentrations at semi-weekly intervals from birth through discharge (range 1-77 days) in 11 premature infants requiring mechanical ventilation (gestational age=28±2 weeks, birth wt=986±189 gms,mean±standard deviation). At the time of leptin sampling, anthropormetric measurements were obtained, and calculations of mid arm circumference/head circumference ratio, and upper arm fat were made. One hundred fifty six measurements of leptin concentrations were obtained in this patient population (mean ± standard deviation = 1.24±63(ngm/ml), range = 0-3). Using a multiple linear regression model including all the variables measured, we determined the best variables in this sample population to predict leptin values. The values that best predicted leptin, in descending order of variance, were: mid arm/head circumference ratio, lower arm circumference, calf circumference, postnatal age, upper arm fat, mid thigh circumference, daily weight, birth weight, and abdominal girth (r value=.71, r-squared=.51, p < .00001. We also performed a multiple linear regression using the variables measured in the investigation and the ratio of mid arm/head circumference as the dependent variable to reflect adequacy of growth in the premature infant (Georgieff et al, J Pediatr 114:288-92, 1989). In this model, the best predictors of the mid arm/head circumference ratio, in descending ratio or variance, were: the mid thigh circumference, leptin, post-conceptional age, triceps skin fold, upper arm circumference, intake, calf circumference, crown rump length, and total body length(r=.9, r-squared = .81, p <.00001). Of most importance, leptin itself accounted for 27% of the variance in mid arm/head circumference ratio. Leptin values in this group of premature infants were both affected by and predictive of neonatal growth. This expands the potential role of leptin as both an intrauterine and neonatal growth factor. This is the first investigation, albeit with preliminary data, linking leptin with somatic growth in the premature infant population.