Differential Study On Browning Of Visceral Adipose Tissue Induced By HIIT In Obesity-prone/Resistant Rats

Objective:Obesity has a serious impact on human health,and the accumulation of visceral fat is associated with a variety of metabolic diseases,so it is of great significance to explore scientific methods for weight loss.Studies have shown that high intensity interval training（HIIT）is effective for weight loss,but its effectiveness in reducing visceral fat is controversial.There are significant metabolic differences between obesity-prone（OP）and obesity-resistant（OR）individuals,and the effect of weight loss may be significantly different after receiving the same exercise.The Browning of white adipose tissue is an important way to lose weight during exercise.This study aims to explore the difference of visceral fat reduction effect and Browning degree between OP and OR individuals after the same HIIT intervention,so as to provide theoretical guidance for the formulation of scientific exercise prescription for weight loss among different populations.Method:Forty-eight rats fed a high-fat diet for 6 weeks were arranged according to their body weight,with the lower quarter（12 rats）as OR rats and the upper quarter（12 rats）as OP rats.OR and OP rats were then randomly divided into quiet-reared obesity-resistance group（D-OR）,HIIT obesity-resistance group（H-OR）,quiet-reared obesity-susceptibility group（D-OP）and HIIT obesity-susceptibility group（H-OP）,with 6 rats in each group.The D-OR group and D-OP group continued to receive high-fat quiet feeding for 12 weeks,while the H-OR group and H-OP group received HIIT platform running training for 12 weeks,5days/week,while the high-fat diet feeding for 12 weeks.The running speed corresponding to about 50%VO_2max（low intensity）and the running speed corresponding to about 90%～100%VO_2max（high intensity）were obtained by increasing load test.The training adopted a cycle of"high intensity 1 minute-low intensity 2 minutes"interval training,and each running distance was about 45 minutes of the corresponding running speed corresponding to 50%VO2max.The running speed was adjusted by increasing load experiment once every two weeks.Record food intake and body weight of rats during the experiment,based on the weighing epididymal fat weight,tem observation of epididymal fat cells mitochondrial morphology structure and the number of real-time fluorescent quantitative PCR test epididymal adipose tissue TBX1 m RNA expression and protein immunoblot test epididymal fat tyrosine hydroxylase（TH）and Uncoupling Protein-1（UCP contains 1）protein expression.Results:（1）Repeated measures ANOVA showed that there was a significant interaction effect between"exercise"and"time"of body weight in both OP group（D-OP and H-OP group）and OR group（D-OR and H-OR group）（P<0.01）.There was a significant interaction effect between"obesity susceptibility"and"time"in the quiet feeding group（D-OP group and D-OR group）（P<0.01）,while there was no interaction effect between"obesity susceptibility"and"time"in the HIIT group（H-OP group and H-OR group）（P=0.09）.（2）After 12 weeks of exercise intervention,two-way ANOVA was conducted for each index.The results showed that the main effects of"exercise"and"obesity susceptibility"on the body weight of rats were very significant（P<0.01）,but there was no interaction effect（P=0.33）.The body weight of the OP group was higher than that of the OR group,and the body weight of the HIIT group was lower than that of the silent feeding group.（3）The main effect of"exercise"on total food intake during intervention was not significant（P>0.05）,but the main effect of"obesity susceptibility"was very significant（P<0.01）,that is,the total food intake of OP was significantly higher than that of OR.There was no interaction between the two factors on total food intake（P=0.62）.（4）The main effects of"exercise"and"obesity susceptibility"on the epididymal fat mass of rats were very significant（P<0.01）,and there was an interactive effect between the two factors on the epididymal fat mass of rats（P<0.01）.The effect of HIIT in reducing epididymal fat mass was more significant in OP group than in OR group（-68.32%vs.-59.13%）.（5）There were few mitochondria in OP epididymal adipocytes reared quietly.However,the number of mitochondria in the epididymal adipocytes of OR reared quietly was more and the crest structure was clearer than that of OP reared quietly.After 12 weeks of HIIT intervention,the number of mitochondria in epididymal adipocytes of OP and OR rats increased,and the structure of mitochondria was relatively clear,but some of the OP mitochondria were vacuolated.（6）The main effect of"exercise"on the expression of UCP-1 protein in the epididymal adipose tissue of rats was significant（P<0.05）,but the main effect of"obesity susceptibility"was not significant（P>0.05）.There was an interactive effect between the two factors on the expression of UCP-1 protein in the epididymal adipose tissue of rats（P<0.05）.The effect of HIIT on the expression of UCP-1protein in epididymal adipose tissue of rats in OP group was better than that in OR group（P<0.05）.（7）The results of Browning TBX1 m RNA by WAT were tested by Kruskal-Wallis test,and there was no statistical difference between the four groups（P=0.16）.（8）The main effect of"exercise"and"obesity susceptibility"on TH protein expression in rat epididymal adipose tissue was not significant（P>0.05）,and the interaction effect of the two factors was not statistically significant（P=0.94）.Conclusion:The effect of high intensity interval training on the reduction of visceral fat in obesity-prone rats was better than that in obesity-resistant rats,the mechanism of which was related to the fact that high intensity interval training significantly promoted the Browning of visceral adipose tissue in obesity-prone rats.