The Changes Of Lipid Metabolism And Regulation By Insulin During Fattening Period And Around Hibernation In Daurian Ground Squirrels(spermophilus Dauricus)

Daurian Ground Squirrels is a typical hibernating species that lives through winter depending upon stored fat. Body fat is the main sources of energy in hibernating animals. In this paper, Daurian ground squirrels(Spermophilus dauricus) was used as the experimental animals. Blood glucose levels before and after hibernation, insulin and adiponectin levels in serum, and insulin receptor levels of white adipose tissue were measured. The differential expression of enzyme genes related to the insulin signaling pathway in white adipose tissue were measured by the high throughput sequencing RNA-Seq to explore the regulated mechanism of insulin on lipid metabolism. Here are the results and conclusions: 1. The blood glucose levels tended to increase from the beginning of the fattening period due to the hyperphagia and achieved the highest level at the period of maximum body mass, then began to drop with the decrease in food intake, and got the lowest during the hibernation period. The food intake was less and the blood glucose level was higher suggested that the function of insulin had reduced during the period of the maximum of body mass. 2. Insulin levels significantly increased from the fattening period to the maximum of body mass period in Daurian ground squirrel. There was no significant change in insulin levels from the maximum of body mass period to the hibernation. Higher level of insulin and the highest level of blood glucose suggested that the insulin resistance had occurred during the maximum of body mass period. 3. The content of insulin receptor had not changed significantly, it remained at a stable level during the annual cycle, suggested that cascade effects of insulin signal transduction were regulated on the post receptor rather than receptor. 4. Insulin molecules binding to the receptors activate insulin signal pathway, and regulate glucose metabolism, lipid metabolism and protein metabolism. The expression of genes related to the upstream signal transduction tended to increase during the fattening period and decreased in the hibernation period, including phosphatidylinositol 3-kinase, 3-phosphoinositide dependent protein kinase, serine/threonine protein kinase, and so on. It suggests that the body fat accumulation during fattening and lipolysis during hibernation was regulated by insulin, and there was not insulin resistance at these two periods. 5. Adiponectin levels decreased significantly from the fattening period to the maximum of body mass period, and maintained at a low level from the maximum of body mass period to hibernation. The opposite variation trends of adiponectin and insulin suggested that there is a negative correlation between adiponectin and insulin may coordinately regulate energy metabolism during fattening and around hibernation in Daurian Ground Squirrels.