| Hibernation patterns have been extensively studied because of their relevance to longevity, low extinction rate, delayed development, low metabolic rate, and low water loss, resistance to muscle atrophy and osteoporosis. We studied mammal hibernation in this article, especially focused on inducing Hipposideros armiger into hibernation under laboratory condition during non-hibernation season, the regulatory mechanism of Leptin conducted on hibernation and cold-induced white adipose tissue browning using bat as a model.Natural conditions restrict hibernation studies because sampling could only be conducted during winter, which hinders development in hibernation research. In the present study, we induced eight Great Roundleaf bats(Hipposideros armiger) into hibernation in winter, spring, and summer under laboratory conditions. Body temperature and heart rate were recorded as index parameters of hibernation. All bats entered a state of hibernation. Body temperature decreased from the normal38℃to10℃, and heart rate decreased from the highest at600beats per min to the lowest at6beats per min when the bats were placed inside the artificial climate incubator with ambient temperature of9℃. In addition, no significant difference in heart rate of torpid bats during the hibernation season and non-hibernation season (spring and summer) was observed (F1=2.850, P=0.102). In summary, hibernation in bats could be induced outside the hibernation season, which provides significant convenience for further research on hibernation in this species.Previous studies have shown that the hormone Leptin has a key function in mammalian heterothermy by regulating metabolism and food intake via lipolysis, as well as selected pressure, which results in the increase in Leptin lipolysis activity in mammals. However, the mechanism by which Leptin functions in heterothermic regulation in mammals is unknown. By combining previous results, we speculated that the answer may lie in the Leptin signaling pathway in the hypothalamus. OB-R1(Leptin receptor long form) is mainly distributed in the hypothalamus, and has a key function in mediating Leptin function, In this study, we used OB-R1as a molecular marker to explore the mechanisms of Leptin in heterothermic regulation. We used RNA interference technology and physiological/molecular analyses with Hipposideros armiger as an animal model. Results of in situ hybridization proved that anti-OB-R1shRNA lentivirus could significantly decreased OB-R1expression in the hypothalamus, especially in the arcuate nucleus, ventromedial hypothalamic nucleus and dorsomedial nucleus. Physiological analysis demonstrated that the thermological ability of bats (e.g., low core body temperature and heart rate) was significantly depressed after OB-RL gene silencing in the hypothalamus. Thus, animals could not enter a state of hibernation. Our study first proved that Leptin pathway blocking via OB-R1silencing inhibited heterothermic regulation. Leptin may be provided a signal of "fat were enough" for inducing mammals into hibernation.We described two species-Hipposideros armiger and Myotis ricketti, belonged to the second largest group model to study cold-induced response in morphology and molecular expression in WAT and BAT. After Exposed to10℃or15℃for7days, Harmiger showed an obvious change in morphology, with increasing multilocular adipocytes and vascular density, and the remarkably high expression of UCP1and PGC-1α in WAT, but that did not happen in M.ricketti. What is more, it was contrary to what happened in mice, the abdominal adipose tissue showed a rapid and significant browning compared to the subcutaneous adipose tissue in H.armiger. These data offer a novel strategy to research the abdominal adipose tissue for disease, such as steatohepatitis, mesenteric diseases and atheroma, as well as an unusual insight into exploration applications on human beings based on the study of this H.armiger model. |
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