Abundance of leptin mRNA in fetal adipose tissue is related to fetal body weight

Leptin mRNA was measured in adipose tissue of fetal sheep by reverse transc ription polymerase chain reaction (RTPCR). Abundance of leptin mRNA relativ e to beta-actin mRNA in fetal perirenal adipose tissue increased (P<0.02) w ith gestation, being higher at 144 d (0.73 +/- 0.10, n=5) than at 90-91 d ( 0.40 +/- 0.08, n=6) or 125 d (0.40 +/- 0.04, n=5) gestation (term similar t o 147-150 d). There was a positive relationship between relative abundance of leptin mRNA (y) and fetal body weight (x) between 90 and 144 d gestation (r(2)=0.27, P<0.01). The slope of the linear dependence of leptin mRNA on fetal weight was 15-fold greater (P<0.001) at 90-91d (y = 2.81x - 1.1, n=6, r(2)=0.71, P<0.025) than between 125-144 d gestation (y = 0.195x - 0.15, n =16, r(2)=0.39, P<0.01). Thus the leptin synthetic capacity of fetal adipos e tissue appears to increase in late gestation but this is accompanied by c onstraint of its sensitivity to fetal body weight. We hypothesise that lept in synthesis in fetal adipose tissue is related to fetal nutrient supply an d growth rate.