Seasonal Variations Of Adipose Tissue In Tupaia Belangeri

Animals employ respective strategies to adapt different natural environments,and small mammals can increase thermogenic capacity to improve their ability to resist cold temperature.The main way of thermogenesis for animals exposed to cold for a long time is nonshivering thermogenesis?NST?,and the main site of its occurrence site is brown adipose tissue?BAT?.In recent years,it has been found that white adipose tissue?WAT?can induce the production of beige adipocytes,which expresses the thermogenic gene of uncoupling protein-1?UCP1?under cold conditions.Based on the previous studies,we explored the changes of adipose tissue of Tupaia belangeri in natural environment from individual,tissue and molecular levels,and laid a foundation for the establishment of energy homeostasis maintenance mechanism and survival adaptation model of T.belangeri in different seasons.This paper mainly studies the following four parts:1.Seasonal variation of body mass and thermogenic capacity in tree shrewsSignificant seasonal differences of tree shrews were showed in body mass,food in-take,resting metabolic rate?RMR?,NST,and UCP1 content of tree shrews.Body mass,food intake,RMR,and UCP1 content were significantly higher in winter than that of in summer,but there had no significant differences in spring and autumn.Body mass,food intake,RMR,NST and UCP1 content of tree shrews in winter increased by 23.67%,36.74%,22.65%,28.69%,and 44.34%compared with that in summer,respectively.The results showed that tree shrews increased their body mass by increasing their food intake,and promoting NST to adapt to cold environment by increasing the content of UCP1 in winter.The weight gain of tree shrews in winter may be related to their habitats.Tree shrews often live in the tropics,subtropics and plateau areas.Even in winter,the food resources were relatively abundant,and the energy consumption can be satisfied by increasing the food feeding.Therefore,food intake of tree shrews in winter was higher than that in summer.The increase of body mass in tree shrews in winter may be partly due to the increasing of mass of adipose tissue.2.Seasonal variation in PET/CT scan and adipose tissue morphology of tree shrew?1?PET/CT scanning:In the present study,PET/CT was used to scan tree shrews in different seasons to explore the metabolic activity of adipose tissue.The results showed that:?1?white adipose tissue:after absorption of ¹⁸F-fluorodeoxyglucose(¹⁸F-FDG)in WAT of tree shrew in winter,the average radiation value?SUV?was the highest;Which was the smallest in summer,and the spring and autumn were between winter and summer.?2?Brown adipose tissue:In winter,the SUV of tree shrew was the highest after the18F-FDG absorption of BAT;the SUV in summer was the smallest,and the spring and autumn were between the winter and summer.The results showed that the metabolic activity of WAT and BAT in tree shrews was increased in winter.?2?Study on adipose histomorphology?hematoxylin and eosin,HE?:?1?White adipose tissue:The white adipocytes in summer were larger,and they were single chamber fat droplets.In winter,the multichamber adipocytes with small lipid droplets were differentiated,and the intercellular space increased and the color darkened.?2?Brown adipose tissue:the cell diameter was the largest and the arrangement was loose in summer,but the cell diameter was the smallest,the number of cells was the largest and the arrangement was tight in winter.The results showed that In winter,fat droplets of beige adipocytes were significantly smaller,and color became darker than those in summer.Similar morphology to BAT was observed,possibly because of an increase in mitochondria.BAT increased the amount of brown adipose cell by differentiation to increase the mass of adipose tissue,thereby increasing the content of UCP1 and promoting NST.3.Seasonal variation of flow analysis of adipose tissue in tree shrews?1?White adipose tissue:The UCP1 antibody of tree shrew was labeled with WAT.The positive expression of UCP1 in white fat cells was the lowest in summer,which was 8.98%,and the highest in UCP1 was 60.91%in winter.Further,the beige fat cell-specific antibody CD137 was used to label the WAT of the abdomen of tree shrew,and the change trend was the same as that of the UCP1:with the cold climate,the cells positive for CD137 increased.?2?Brown adipose tissue:BAT was labeled with UCP1 antibody 22.38%of cells in BAT showed positive expression in summer,and 83.78%of them showed UCP1positive expression in winter.The results showed that the positive expression of UCP1 and CD137 in white adipose tissue increased in winter,and induced"browning"of white adipose tissue,which may produce beige adipocytes.The positive expression of UCP1 in brown adipose tissue was increased,which indicated that the heat production activity of brown adipose tissue was increased.4.Seasonal variation of PPAR??COX-2?PGC-1?gene expressions of tree shrews?1?White adipose tissue:Expression of COX-2 in WAT of tree shrew in winter was significantly higher than that in spring,summer and autumn;the expression of PGC-1?was the highest in winter,significantly higher than that in summer;and the expression of PGC-1?showed significant differences during four seasons;the expression of PPAR?showed no significant seasonal variations.?2?Brown adipose tissue:Expression of COX-2 in BAT of tree threw in autumn and winter was significantly higher than that in spring and summer;the expression of PGC-1?was not significantly different in seasonal variations;and the expression of PPAR?in spring and winter were significantly higher than that in summer.The expressions of COX-2 and PGC-1?in the WAT of tree shrews were higher in winter than in summer,indicating that“browning”may occurred in the WAT.In winter,the expression of PGC-1?in WAT and BAT of tree shrews were higher,which suggest that the beige adipocytes and brown adipocytes in adipose tissue might be coexistence.In conclusion,tree shrews could produce beige adipocytes by inducing“browning”of WAT,and increase the expression of UCP1 to compensate for the deficiency of thermogenesis of NST induced by BAT in winter.While BAT could differentiate more brown adipocytes to increase the activity of UCP1 and enhance thermogenesis of NST to resist cold temperature.It is proved for the first time that WAT can also browning and producing thermogenic cells under natural conditions,and that BAT differentiates to increase thermogenesis in tree shrews.