Key points• Perinatal maternal high-fat diet changes milk composition, resulting in obesity and hyperglycaemia in male offspring at weaning.• Offspring obesity is associated with hyperleptinaemia and changes in the central leptin signalling pathway in the hypothalamic arcuate nucleus.• Maternal high-fat diet increased adrenal catecholamines in offspring but reduced liver and adipose tissue adrenoreceptors, thereby contributing to increased adiposity in these animals.• Early obesity and hyperleptinaemia in offspring may have a stimulatory effect on the hypothalamus-pituitary-thyroid axis as an adaptive response to the positive energy balance.• Both catecholamines and thyroid hormones may impact cardiovascular function, thereby contributing to the development of hypertension.Abstract Maternal nutritional status affects the future development of offspring. Both undernutrition and overnutrition in critical periods of life (gestation or lactation) may cause several hormonal changes in the pups and programme obesity in the adult offspring. We have shown that hyperleptinaemia during lactation results in central leptin resistance, higher adrenal catecholamine secretion, hyperthyroidism, and higher blood pressure and heart rate in the adult rats. Here, we evaluated the effect of a maternal isocaloric high-fat diet on breast milk composition and its impact on leptinaemia, energy metabolism, and adrenal and thyroid function of the offspring at weaning. We hypothesised that the altered source of fat in the maternal diet even under normal calorie intake would disturb the metabolism of the offspring. Female Wistar rats were fed a normal (9% fat; C group) or high-fat diet (29% fat as lard; HF group) for 8 weeks before mating and during pregnancy and lactation. HF mothers presented increased total body fat content after 8 weeks (+27%, P < 0.05) and a similar fat content at the end of lactation. In consequence, the breast milk from the HF group had higher concentration of protein (+18%, P < 0.05), cholesterol (+52%, P < 0.05) and triglycerides (+86%, P < 0.05). At weaning, HF offspring had increased body weight (+53%, P < 0.05) and adiposity (2 fold, P < 0.05), which was associated with lower β3-adrenoreceptor content in adipose tissue (−40%, P < 0.05). The offspring also presented hyperglycaemia (+30%, P < 0.05) and hyperleptinaemia (+62%, P < 0.05). In the leptin signalling pathway in the hypothalamus, we found lower p-STAT3/STAT3 (−40%, P < 0.05) and SOCS3 (−55%, P < 0.05) content in the arcuate nucleus, suggesting leptin resistance. HF offspring also had higher adrenal catecholamine content (+17%, P < 0.05), liver glycogen content (+50%, P < 0.05) and hyperactivity of the thyroid axis at weaning. Our results suggest that a high fat diet increases maternal body fat and this additional energy is transferred to the offspring during lactation, since at weaning the dams had normal fat and the pups were obese.

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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.

Leptin has been shown to regulate the hypothalamuspituitary-thyroid axis, acting primarily through the STAT3 pathway triggered through the binding of leptin to the longchain isoform of the leptin receptor, ObRb. We previously demonstrated that although hyperthyroid rats presented leptin effects on TSH secretion, those effects were abolished in hypothyroid rats. We addressed the hypothesis that changes in the STAT3 pathway might explain the lack of TSH response to leptin in hypothyroidism by evaluating the protein content of components of leptin signalling via the STAT3 pathway in the hypothalamus and pituitary of hypothyroid (0 . 03% methimazole in the drinking water/21 days) and hyperthyroid (thyroxine 5 mg/100 g body weight /5 days) rats.Hypothyroid rats exhibited decreased ObRb and phosphorylated STAT3 (pSTAT3) protein in the hypothalamus, and in the pituitary gland they exhibited decreased ObRb, total STAT3, pSTAT3 and SOCS3 (P!0 . 05). Except for a modest decrease in pituitary STAT3, no other alterations were observed in hyperthyroid rats. Moreover, unlike euthyroid rats, the hypothyroid rats did not exhibit a reduction in food ingestion after a single injection of leptin (0 . 5 mg/kg body weight). Therefore, hypothyroidism decreased ObRb-STAT3 signalling in the hypothalamus and pituitary gland, which likely contributes to the loss of leptin action on food intake and TSH secretion, as previously observed in hypothyroid rats.

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