Racial variation in umbilical cord blood leptin concentration in male babies.

Background: We hypothesize that racial differences in utero contribute to the racial disparity in prostate cancer risk. Leptin is a candidate for evaluating this hypothesis because it influences fetal development and newborn growth.

Methods: We measured leptin concentration by ELISA in venous cord blood collected from 70 African-American and 37 white male full-term babies. We measured sex steroid hormones and insulin-like growth factor (IGF) axis concentrations previously. Separately by race, we calculated the geometric mean leptin concentration and estimated the geometric mean adjusted for birth and placental weights, mother's age and parity, time of day and season of birth, and sex steroid hormone and IGF axis concentrations by linear regression.

Results: Leptin was positively correlated with birth (r = 0.34) and placental (r = 0.25) weights, IGF-1 (r = 0.21), and IGF binding protein-3 (r = 0.29) adjusting for race. Unadjusted geometric mean leptin did not differ (P = 0.92) between African Americans (5,280 pg/mL; 95% CI: 4,322-6,451) and whites (5,187 pg/mL; 95% CI: 3,938-6,832). Adjusted geometric mean leptin was nonstatistically significantly higher (P = 0.15) in African Americans (5,954 pg/mL; 95% CI: 4,725-7,502) than in whites (4,133 pg/mL; 95% CI: 2,890-5,910).

Conclusion: We observed a nonsignificantly higher adjusted cord blood leptin concentration in African-American male babies than in white male babies, although unadjusted levels were similar.

Impact: These findings do not support the hypothesis that leptin level in utero contributes to the racial disparity in prostate cancer risk in adulthood.