Physiological variations of energy metabolism and body fat accumulation are the main energy budgets in small mammals to cope with natural environmental changes. However, the energy mechanisms underpinning the adaptive regulations in different stages of lifespan remain unclear. The present study was aimed to examine the changes in energy metabolism, fat accumulation and the endocrine mechanisms in striped hamsters (Cricetulus barabensis) during lactation and post-lactation. The food intake, fat depots mass, serum leptin levels and the gene expression of leptin receptor (Ob-Rb) and neuropeptides related to food intake regulation in hypothalamus were measured. The results showed that the fat depots were almost decreased to zero at peak lactation, and then were increased significantly during post-lactation. The masses of subcutaneous fat, perirenal fat and abdominal fat were 1.5, 37.1 and 1.9 fold higher in post-lactating females than that in non-reproductive controls. Food intake and serum leptin level of post-lactating females were significantly higher than that of non-reproductive controls, while the gene expression of Ob-Rb was significantly down-regulated in post-lactating females. The gene expression of orexigenic and anorexigenic neuropeptides did not differ between the two groups. The litter size raised during lactation had no significant effects on food intake, resting metabolic rate and body components in post-lactating females. These findings suggest that body fat accumulation is adaptively regulated in the different stages of reproduction.

Leptin resistance may be one of the most important endocrine mechanisms underpinning the fat accumulation during post-lactation. This is of significance for the mothers to restore fat accumulation and to cope with the periods of high energy demands and food shortage, increasing the fitness.