Supplementation of suckling rats with cow's milk induces hyperphagia and higher visceral adiposity in females at adulthood, but not in males.

In humans, complementary feeding should be started after 6 months-old; the introduction of any food or water before this time is considered early weaning, which is associated with health problems in adulthood. Cow's milk is a common food introduced to children less than 6 months that has inadequate nutritional composition mainly due to a worse casein: whey protein ratio compared to human milk. We hypothesized that suckling rats fed with cow's milk, rich in bioactive peptides, develop further metabolic dysfunctions. From postnatal day (PN) 14 to 20, Wistar rat pups were divided into 3 groups: rat milk (RM) - pups received rat milk orally in a syringe; cow's milk (CM), pups received cow's milk; CM with high protein (CM-H), CM with twice protein amount of rat milk. Pups were killed on PN21 and PN180. At PN21, CM males had lower visceral fat mass compared with other groups. Serum corticosterone was higher in CM-H males, despite no change in glucocorticoid metabolism in liver and visceral fat. At PN180, CM and CM-H females had greater fat depots and hyperphagia, although no alteration in leptinemia and leptin signaling in hypothalamus. CM-H females had a trend of hypoinsulinemia and significant decrease in HOMA-ß, suggesting lower insulin secretion. Males from CM-H group had only lower total body protein mass. CM males had hypercorticosteronemia associated with lower expression of 11ßHDS1 in visceral fat. In conclusion, early introduction of cow's milk in neonate rats leads to gender-dependent differences in metabolic and endocrine parameters in the short- and long-term.

Effects of cigarette smoke exposure during suckling on food intake, fat mass, hormones, and biochemical profile of young and adult female rats.

PURPOSE: Children from smoking mothers have a higher risk of developing obesity and associated comorbidities later in life. Different experimental models have been used to assess the mechanisms involved with this increased risk. Using a rat model of neonatal nicotine exposure via implantation of osmotic minipumps in lactating dams, we have previously shown marked sexual dimorphisms regarding metabolic and endocrine outcomes in the adult progeny. Considering that more than four thousand substances are found in tobacco smoke besides nicotine, we then studied a rat model of neonatal tobacco smoke exposure: adult male offspring had hyperphagia, obesity, hyperglycemia, hypertriglyceridemia, secondary hyperthyroidism and lower adrenal hormones. Since litters were culled to include only males and since sexual dimorphisms had already been identified in the nicotine exposure model, here we also evaluated the effects of tobacco smoke exposure during lactation on females. METHODS: Wistar rat dams and their pups were separated into two groups of 8 litters each: SMOKE (4 cigarettes per day, from postnatal day 3 to 21) and CONTROL (filtered air). Offspring of both sexes were euthanized at PN21 and PN180. RESULTS: Changes in male offspring corroborated previous data. At weaning, females showed lower body mass gain and serum triglycerides, but no alterations in visceral fat and hormones. At adulthood, females had higher body mass, hyperphagia, central obesity, hyperleptinemia, hypercholesterolemia, hypercorticosteronemia, but no change in serum TSH and T3, and adrenal catecholamine CONCLUSIONS: Sexual dimorphisms were observed in several parameters, thus indicating that metabolic and hormonal changes due to smoke exposure during development are sex-dependent.