Leptin alters the structural and functional characteristics of adipose tissue before birth

This study aimed to determine for the first time whether leptin can act to alter the structural andfunctional characteristics of adipose tissue before birth. Leptin (0.48 mg/kg/day) or saline wasinfused intravenously into fetal sheep for 4 days from either 136 or 137 days of gestation(term=147±3 days). Circulating leptin concentrations were increased approximately four- tofivefold by leptin infusion. Leptin infusion resulted in a significant increase in the proportion ofsmaller lipid locules present within fetal perirenal adipose tissue (PAT), and this was associatedwith a significant increase in the proportion of multilocular tissue and a significant decrease inthe proportion and relative mass of unilocular tissue in fetal PAT. The relative abundance ofleptin mRNA in fetal PAT was significantly lower in the leptin-infused group, and there was apositive correlation between the relative abundance of leptin mRNA and the proportion ofunilocular adipose tissue in fetal PAT. The amount of uncoupling protein 1 tended to be higher(P=0.06) in leptin-infused compared with saline-infused fetuses. This is the first demonstrationthat leptin can act to regulate the lipid storage characteristics, leptin synthetic capacity, andpotential thermogenic functions of fat before birth.