Abstract
Juvenile obesity is a rising epidemic due largely to consumption of caloric dense, fat-enriched foods. Nevertheless, literature on fat-induced neuroendocrine and metabolic disturbances during adolescence, preceding obesity, is limited. This study aimed to examine early events induced by a fat diet (45% calories from saturated fat) in male rats fed the diet during the pre- and post-pubertal period. The neuroendocrine endpoints studied were the levels of circulating leptin, insulin and corticosterone, as well as their receptors in the hypothalamus and hippocampus. Hormonal levels were determined by radioimmunoassay and receptors' levels by western blot analysis. Leptinemia was increased in pubertal rats and in adult rats fed the fat diet from weaning to adulthood, but not in those fed from puberty to adulthood. Modifications in the developmental pattern from puberty to adulthood were observed for most of the brain receptors studied. In adult animals fed the fat diet from weaning onwards, the levels of leptin receptors in the hypothalamus and glucocorticoid receptors in the hippocampus were decreased compared to chow-fed controls. Switching from fat to normal chow at puberty onset restored the diet-induced alterations on circulating leptin, but not on its hypothalamic receptors. These data suggest that when a fat-enriched diet, resembling those consumed by many teenagers, provided in rats during pubertal growth, it can longitudinally influence the actions of leptin and corticosterone in the brain. The observed alterations at a preobese state may constitute early signs of the disturbed energy balance toward overweight and obesity.