The Characteristic Of Plasticity Regulation Of Fat And Energy Mechanism In Striped Hamsters In Response To Food Restriction

The seasonal changes of food availability,the one of the main environment factor,have important effects on physiology and behavior of animals.The adaptive regulation of energy metabolism is a key strategy of small mammals to cope with environment changes.An animal usually mobilizes fat storage during the food shortage periods,resulting in significant reduction of body mass and body fat.However,the animals increase fat storage when food provision is plentiful,resulting in significant accumulation of body fat and rapid regain of body mass.So far,a number of researches have focused on the effect of food restriction on body mass and fat metabolism.However,it is still unclear that the energy metabolic mechanism related to accumulation of body fat and regain of body mass in the animals refed ad libitum.This study was performed in order to explore the plastic regulations of energy metabolism,body mass and body fat in the animals under food restriction and refeeding.The neuroendocrine mechanism associated with energy metabolism during food restriction and refeeding was also examined.Two experiments were designed in adult male striped hamsters in the present study.In experiment 1,the plastic regulation of body fat and energy mechanism was examined in striped hamsters?Cricetulus barabensis?subjected to food restriction and refeeding.Animals were randomly assigned into one of four groups:one control group,animals were fed ad libitum?Ad?and three food restriction and refeeding groups?FR-Re?,animals were restricted by 15%,30%and 40%of ad libitum food intake for two weeks,followed by high-fat diet refeeding for 6weeks?FR15%-Re,FR30%-Re and FR40%-Re?.In experiment 2,the energy budget and its mechanism were examined in striped hamsters to cope with food availability changes at different temperatures.Animals were randomly assigned into three groups:5?,21?and 33?groups,the animals were exposed to 5?,21?and 33?for 8 weeks,within which animals were subjected to food restriction for one day per week,i.e.animals were experiencing four cycles of food restriction and refeeding?cycle 1-4 FR-Re?.During the period of the experiments,body mass,food intake,gross energy intake,digestive energy intake and digestibility,resting metabolic rate?RMR?,the levels of serum leptin and thyroid hormones,as well as the gene expression of neuropeptides in the hypothalamus,the gene expression related to fat?oxidation in subcutaneous white adipose tissue,brown adipose tissue and liver.The main results were listed as follows,1)the striped hamsters mobilized fat storage to cope with food restriction period and increased fat accumulation when food was plentiful,which were employed to meet the unpredictable food shortage periods.The plasticity of fat metabolism regulation was of significance for the animals to cope with the changes of food availability,and therefore enhanced the survival capacity.2)The significant regain of body mass and body fat accumulation were observed in the condition of food plenty in the striped hamsters subjected to mild food restriction.This might be because that the significant down regulations of Lep Rb,POMC and CART impaired the role of leptin inhibitory effect on food intake.The significant decrease of fat?oxidation might lead to the significant regain of body mass and fat accumulation.3)The food restricted striped hamsters mobilized more fat to cope with cold temperature related to the hamsters exposed to the warm temperature,resulting in the notable reduction of fat content.4)Resting metabolic rate significantly increased at cold in the food-restricted animals when refed ad libitum,indicating that metabolic thermogenesis played a key role in fat mobilization.5)The gene expression of hormone sensitive lipidase?HSL?and the serum T₃ levels and the ratio of T₃/T₄ increased significantly at the cold,indicating that thyroid hormones induced fat?oxidation might be involved in fat mobilization.These results suggest that the plasticity regulations of energy metabolism are important energy strategy to meet the changes of food availability,within which leptin resistance may underline the regain of body mass and fat accumulation in the animals under food restriction and refeeding.The thyroid hormones induced the increases of metabolic thermogenesis and fat?oxidation likely play important roles in the inhibition of fat accumulation at the cold.