Mechanism Of TRF On The Metabolic Remodeling Of Adipose Tissue Of Mice Induced By A High-fat Diet

Objective: Obesity and its complications caused by high-fat diet have become a worldwide public health problem.Time-restricted feeding(TRF)is a dietary pattern that restricts the time window for daily eating,but not the type of diet or total calorie intake.In recent years,more and more studies have shown the health protective effect of TRF on obese people,but its mechanism needs to be further explored.This study investigates the effects of time-restricted eating on the prevention and treatment of obese mice on a highfat diet from the perspective of adipose tissue metabolic remodeling,which is expected to provide new ideas for the prevention and treatment of obesity and its complications.Methods: 14-month-old male C57BL/6 mice were randomly divided into 4 groups after one week of adaptive feeding on normal diet: the AL+Chow group,8h TRF+Chow group,AL+HFD group,and 8h TRF+HFD group.The 8h TRF group was fed during ZT15-ZT23(22:00-6:00)each day and withdrawn for the rest of the day.Body weight was recorded weekly.Micro-CT and magnetic resonance imaging scanners were used to observe the changes in fat content.Energy metabolism monitoring system was used to monitor the changes in food intake,respiratory exchange rate,and activity.Oral glucose tolerance test was used to detect the changes in glucose tolerance of the mice.After 7 months of timerestricted feeding,the mice were sacrificed by cervical vertebra or perfused heart at the age of 21 months,by which epididymal white adipose tissue,inguinal subcutaneous white adipose tissue and brown adipose tissue were collected.HE staining was used to observe the pathological changes in adipose tissue,and biochemical kits were used to detect the changes of TC,TG,LDL,and HDL.Western blot was used to detect the protein expression levels of UCP1,PPARγ,PGC-1α,AMPK,p-AMPK,SIRT1,and SIRT3 in epididymal white adipose tissue and inguinal white adipose tissue.Results:(1)Compared with AL+Chow group,the body weight of mice in AL+HFD group was significantly increased(P<0.01);after the 8h restricted feeding intervention,body weight in 8h TRF+Chow group decreased significantly compared with AL+Chow group(P<0.01),and the similar tendency was also found in 8h TRF+HFD group compared with AL+HFD group(P<0.01);Micro-CT and magnetic resonance imaging scanner results showed that the fat content of mice in the AL+HFD group was significantly increased relative to AL+Chow group(P<0.01);after 8h restricted feeding,there was a trend of decreasing fat content in 8h TRF+Chow group compared with AL+Chow group,and a decrease in fat content in 8h TRF+HFD compared with AL+HFD group(P<0.01);HE staining showed that compared with AL+Chow group,the adipocytes of e WAT and i WAT in AL+HFD group were swollen and deformed,the lipid droplets enlarged,and the mean cross-sectional area of the cells increased(P<0.01);After 8 hours of time-restricted feeding,whereas there was no significant change in the mean cross-sectional area of the cells in8 h TRF+Chow group compared with AL+Chow group,8h TRF+HFD group had less swelling and deformation of adipocytes,less lipid droplets,and less mean cross-sectional area of adipocytes than AL+HFD group(P<0.01);(2)The results of glucose tolerance test showed that the area under the blood glucose curve in AL+HFD group was higher than that in t AL+Chow group(P<0.01);After 8 hours of time-restricted feeding,8h TRF+Chow group had a significant reduction in the area under the blood glucose curve compared with AL+Chow group(P<0.01),and 8h TRF+HFD group had a significant reduction in the area under the curve of blood glucose compared with AL+HFD diet group(P<0.01);The results of four blood lipid tests showed that the levels of TC,TG and LDL were significantly higher in AL+HFD group compared with AL+Chow group(P<0.01),while the level of HDL did not change significantly;After the intervention of 8h time-restricted feeding,the levels of TC,TG,LDL and HDL in 8h TRF+Chow group did not change significantly compared with AL+Chow group,while the levels of TC,TG and LDL in 8h TRF+HFD group decreased significantly compared with AL+HFD group(P<0.01);(3)The results of energy metabolism monitoring system showed that compared with AL+Chow group,the activity level of the mice in AL+HFD group decreased(P<0.05);After the intervention of time-restricted feeding,the activity level of 8h TRF+Chow group was higher than that of AL+Chow group(P<0.01),and the activity level of 8h TRF+HFD group was significantly higher than that of AL+HFD group(P<0.01);Western blot results showed that the expression of thermogenic proteins UCP1,PPARγ and PGC-1α in the white adipose tissue of epididymis group was significantly reduced in AL+HFD group compared with AL+Chow group(P<0.05);After the eight-hour time-restricted feeding intervention,compared with AL+Chow group,PPARγ of the epididymal white adipose tissue in8 h TRF+Chow group had no significant changes,UCP1 and PGC-1α tended to decrease,but the expression of PPARγ in epididymal white adipose tissue had a significant increase in 8h TRF+HFD group compared with AL+HFD group(P<0.01).The expression levels of PGC-1α and UCP1 tended to increase;At the same time,compared with AL+Chow group,the expression of UCP1 and PGC-1α in the subcutaneous white adipose tissue of the mice in AL+HFD group decreased(P<0.05),and there was a trend of reduction in PPARγwithout statistical difference;After the eight-hour time-restricted feeding intervention,there was no significant difference in PPARγ between 8h TRF+Chow group and AL+Chow group,and the expression of UCP1 and PGC-1α was reduced without statistical difference,while the expression of UCP1,PPARγ and PGC-1α in 8h TRF+HFD group increased compared with AL+HFD group;Compared with AL+Chow group,the expression of energy metabolism-related protein p-AMPK/AMPK in inguinal subcutaneous white adipose tissue in AL+HFD group showed a tendency to decrease,SIRT1 showed no significant change,and the expression of mitochondrial biogenesis related protein SIRT3 was decreased(P<0.05);Compared with AL+Chow group,there was a trend of increasing p-AMPK/AMPK,decreasing SIRT1,and no significant change in SIRT3 in 8h TRF+Chow group.The expression of SIRT1 in 8h TRF+HFD group increased compared with AL+HFD group(P<0.05),while SIRT3 and p-AMPK/AMPK showed an increasing trend without statistical difference.Conclusions: The 8-hour TRF can improve obesity,impaired glucose tolerance and lipid metabolism disorders induced by high-fat diet,which may increase the expression of thermogenic protein UCP1 through AMPK/SIRT1-PGC-1α and PPAR signaling pathways,induce metabolic remodeling of white adipocytes,promote the Browning of white adipose tissue,and increase thermogenesis and energy metabolism.