Hyperleptinemia in pregnant bats is characterized by increased placental leptin secretion in vitro

Hyperleptinemia is a common feature of pregnancy in mammals. The source of increased plasma leptin is uncertain. We examined leptin secretory rates in vitro to test the hypothesis that leptin secretion is upregulated during p regnancy, Two species of insectivorous bats were examined, Myotis lucifugus and Eptesicus fuscus, because of their unique reproductive cycle. Body mas s and plasma leptin significantly increased with gestation and decreased du ring lactation. Adiposity increased in midgestation, then decreased in late gestation and lactation and was not significantly correlated with plasma l eptin in pregnant or early lactating individuals. Leptin secretion in vitro per gram of adipose tissue tended to increase with gestation but was not s ignificantly correlated with plasma leptin in the same individuals. Leptin secretion from placentae, however, increased with gestation and was signifi cantly correlated with plasma leptin from the same individuals. In suckling pups, plasma leptin was high shortly after birth, then decreased to low le vels that were not correlated with adiposity thereafter. We conclude that i n bats, the placenta is a major source of circulating leptin during pregnan cy, and that adiposity and plasma leptin levels are decoupled during three different periods of intense metabolic demand (pregnancy, early lactation, and neonatal growth).