Characterization of the metabolic differences between male and female C57BL/6 mice

The present study aims to compare the responses between male and female C57BL/6 mice to multiple metabolic challenges to understand the importance of sex in the control of energy homeostasis. Male and female C57BL/6 mice were subjected to nutritional and hormonal challenges, such as food restriction and refeeding, diet-induced obesity, feeding response to ghrelin and leptin, ghrelin-induced growth hormone secretion, and central responsiveness to ghrelin and leptin. The hypothalamic expression of transcripts that control energy homeostasis was also evaluated. Male mice lost more weight and lean body mass in response to food restriction, compared to females. During refeeding, males accumulated more body fat and exhibited lower energy expenditure and glycemia, as compared to females. Additionally, female mice exhibited a higher protection against diet-induced obesity and related metabolic imbalances in comparison to males. Low dose ghrelin injection elicited higher food intake and growth hormone secretion in male mice, whereas the acute anorexigenic effect of leptin was more robust in females. However, the sex differences in the feeding responses to ghrelin and leptin were not explained by variations in the central responsiveness to these hormones nor by differences in the fiber density from arcuate nucleus neurons. Female, but not male, mice exhibited compensatory increases in hypothalamic Pomc mRNA levels in response to diet-induced obesity. Our findings revealed several sexually differentiated responses to metabolic challenges in C57BL/6 mice, highlighting the importance of taking into account sex differences in metabolic studies. •Male mice loose more weight and lean mass during food restriction than females.•Males gain more fat and have lower energy expenditure and glycemia after refeeding.•Females exhibit higher protection against diet-induced obesity compared to male mice.•Male mice are more ghrelin-sensitive, but less leptin-sensitive, than female mice.•Increased hypothalamic Pomc mRNA levels in diet-induced obese female mice