Energetic Characteristics And Molecular Mechanisms Of Daurian Ground Squirrels(Spermophilus Dauricus) During The Preparation Of Hibernation

Fat-storing hibernators accumulate body fat before hibernation. Fat is not only an energy storage but also an endocrine organ, which synthesize and secrete cytokines to regulate feeding, metabolism, energy storage and energy consumption.To explore the physiological changes and their molecular mechanism during fattening and entering into hibernation, we used Daurian ground squirrels as experimental animals in this study. The animals were divided into four phases according to their body mass and body temperature(Tb) changes, Fattenning phase(F), Maximum of body mass(BMmax), Post-fattening phase(P-F) and Test drop(TD).Tb was recorded continuously. Behaviours of feeding, lying in nest ect. were recodrded at the four phases; resting metabolic rate(RMR), respiratory quotient(Q),energy intake, blood indicators and levels of macromolecules associated with lipid metabolism in blood were measured at the four phases. White adipose tissue(WAT)was used to detect the differential expression of enzyme genes related to lipid metabolism by the method of high-throughput sequencing. In addition, to understand the influence of photoperiod on hibernation in fat-storing hibernators, Daurian ground squirrels(Spermophilus dauricus) were acclimatized in 5℃ with 12 h light:12h dark(12L:12D) after reaching the maximum body mass, the hibernation pattern and energy consumption were compared with that in darkness(0h light:24h dark, 0L:24D). The main results and conclusions were that:1. Behavior of Daurian ground squirrels: feeding time and frequency was significantly reduced in P-F period, while nest lying time during daytime was significant increase. Energy intake reached the maximum before BMmax period, then decreased. The dorp in body temperature(Tb) bengan on 13-34 days before the first heterothermy. Regulation of Tb was more accurate in BMmax, than before and after, Tb decreased after BMmax. Metabolic rate reached the maximum in BMmax, then decreased. Respiratory quotient turned in BMmax. Conclusion: Preparation of hibernation in Daurian ground squirrels was a gradual process, physiological re-established of hibernation happened in BMmax, long before hibernation.2. The concentration of FFA in serum significantly decreased in P-F period and hibernation. High-density lipoprotein, cholesterol and ketone significantly increased in hibernation period. In P-F period, m RNA of enzymes in fatty acid synthesis process decreased and m RNA in fatty acid catabolism increased. m RNA of ketone synthesis enzyme increased significantly in P-F period and hibernation, and m RNA of ketones degradation fell in Finished-fattening period, lowest in hibernation. Conclusion: With the preparation of hibernation, carbohydrate catabolism for energy decreased and lipolysis for energy increased in Daurian ground squirrels.3. Compared with the dark condition, applying light in hibernation reduced the expression of deep hibernation, and more animals did not hibernate in winter, energy consumption increased in Daurian ground squirrels. Sleep occurs in the dark phase, awakening occurred in the light phase, hibernating most occurred in the dark phase, and awakening in the light phase. Conclusion: Duration of hibernation in Daurian ground squirrels was reduced under light-dark cycle conditions and energy consumption was increased. Hibernating and awakening time showed obvious light-dark rhythm.