Body mass, index, body composition, and leptin at onset of puberty in maleand female rats after intrauterine growth retardation and after early postnatal food restriction

In this study we examined the body composition at onset of puberty in intra uterine growth retarded (IUGR), postnatal food restricted (FR), and control male and female rats. IUGR was induced by ligation of the uterine artery o n d 17 of gestation and FR by litter enlargement to 20 pups per mother from d 2 after birth until weaning (d 24). We defined onset of puberty as balan opreputial separation in male rats and vaginal opening in female rats. We c alculated body mass index, measured body composition with dual-energy x-ray absorptiometry, and measured leptin concentrations in serum. It was report ed previously that early malnutrition, either during late gestation or imme diately postnatally, results in a delayed onset of puberty in IUGR and FR m ale rats and in IUGR female rats, but not in FR female rats. In IUGR male r ats at balanopreputial separation and in IUGR female rats at vaginal openin g no differences were found in body mass index, body composition, and lepti n levels compared with controls. FR male rats had a significantly lower per centage of fat and serum leptin concentrations at balanopreputial separatio n. FR female rats had a significantly lower body mass index, percentage of fat, and serum leptin concentrations at vaginal opening. We conclude that t he onset of puberty in the rat is not dependent on a certain percentage of body fat or a certain threshold of circulating levels of leptin and that fo od deprivation during different "critical" time periods around birth result s in different effects in later life.