Ontogeny and insulin regulation of fetal ovine white adipose tissue leptin expression

Leptin, an adipocyte-derived factor, has multiple biological roles including mitogenesis. We investigated the effect of normal development, acute and chronic hyperglycemia and hypoglycemia, and selective acute hyperglycemia, or hyperinsulinemia, on fetal ovine white adipose tissue (WAT) leptin mRNA concentrations. Leptin mRNA amounts expressed as a ratio to the internal control ribosomal S2 mRNA decreased threefold with advancing gestational age (P < 0.05). This gestational decrease was opposite to the 10-fold increase in fetal body weight during the same developmental period. Chronic hyperglycemia with hyperinsulinemia led to no change in WAT leptin mRNA concentrations over a 1- to 10-day duration, but it caused a 40% increase over a 14- to 20-day duration (P < 0.05) along with an increase in fetal body weight (P < 0.05). In contrast, hypoglycemia with hypoinsulinemia, while not affecting WAT leptin mRNA from 1 to 34 days, resulted in a 50% decline over a 36- to 76-day duration along with a decline in fetal body weight (P < 0.05). Acute 24-h studies of selective hyperglycemia with euinsulinemia showed no significant change in WAT leptin mRNA, but in response to selective hyperinsulinemia with euglycemia at 24 h, a twofold increase was observed (P < 0.05). We conclude that fetal WAT leptin mRNA amounts are regulated by fetal development and circulating insulin concentrations. We speculate that chronic in utero metabolic perturbations that alter circulating insulin concentrations affect fetal leptin production that may mediate insulin's influence on fetal growth.