Circadian and circannual aspects of leptin chronome in cord blood

A transverse (cross-sectional) approach on a population of newborns shows that leptin concentrations are higher in babies born before vs. after 12:00 noon and are higher in spring and summer than in fall. Cord blood leptin concentration is elevated in the presence of a family history of obesity on the paternal side, but not on the maternal side. In keeping with earlier work, leptin concentration in cord blood correlates positively with birth weight (P < 0.001) and height (P < 0.001) and is higher in babies appropriate for or large for gestational age than in babies small for gestational age or born prematurely. The association of cord blood leptin concentration with obesity on the paternal side may help clarify the role of leptin in parental contributions to human obesity and may prompt focus upon cholesterol metabolism. Transverse rhythms established on groups, such as the circannual component and the within-day difference demonstrated herein, should prompt longitudinal studies on individuals, notably when they can be done non-invasively, as is the case of growth.