Effects Of High-suger/Restricted-calorie Diet On Glucose And Lipid Metabolism In CTRP6^-/- Mice

Obesity is one of the worldwide public health problem and the main cause of many chronic metabolic diseases.The manifestations of obesity include excessive accumulation of white fat,disorder of endocrinic function of adipose tissue,imbalance of glucose and lipid metabolism and so on.Identifying the key regulatory factors affecting lipid metabolism and understanding the regulatory network of lipid metabolism is a necessary basis for the treatment of obesity and its related diseases.Complement-C1q tumor necrosis factor-associated protein 6（CTRP6）is a adipokine,which plays an important role in glucose and lipid metabolism,adipocyte differentiation and adipogenesis,but the mechanism of the effect of CTRP6 on metabolism has not been fully elucidated.In this study,two batches of feedinged experiments with diets,high-sugar diet（cola as only drinking liquid）and calorie-restricted diet（alternate-day fasting）,were carried out with CTRP6^-/-（KO）mice as the model and wild type（WT）mice as the control.Under each feeding condition,the body weight,food intake,behavior,insulin sensitivity,glucose tolerance and fat accumulation of the two genotypic mice were compared to determine the effects of CTRP6 on glucose and lipid metabolism in mice with different calorie intake.Then the expression of lipid metabolism related genes and the activity of related signal pathways were detected by cellular molecular biology techniques such as real-time PCR and Western blot,which provided new evidence for analyzing the mechanism of CTRP6 affecting glucose and lipid metabolism.The results are as follows:In the high-sugar diet experiment,mice were fed with cola instead of drinking water for 11 weeks.Compared with the drinking water group,the body weight,body fat and serum triglyceride content of WT and KO mice in the cola group were significantly lower than those in the drinking water group,which was contrary to the expectation of the study.Further analysis of feed intake showed that the average daily feed intake of mice in the cola group was significantly lower than that in the drinking water group.The analysis of the expression levels of appetite regulation genes（POMC and Ag RP）in the hypothalamus also confirmed the loss of appetite in the cola group.Therefore,it is inferred that it may be because the intake of cola suppresses the appetite of mice,resulting in a decrease in food intake,which in turn reduces body weight,body fat and blood lipids.Based on the analysis of lipid metabolism marker genes and related signal pathways,it was found that the expression levels of lipid synthesis marker genes（PPARγ,a P2,FAS）and lipid decomposition marker genes（ATGL,LPL,HSL）increased and the activity of p38signal pathway decreased in cola group.It is inferred that long-term drinking cola can reduce lipid accumulation by inhibiting the activity of p38 signal pathway.Behavioral analysis found that cola as only drinking liquid made mice more nervous in unfamiliar environments and more likely to give up under stress.Comparing the two genotypes of mice,it was found that compared with WT mice,the average daily feed intake of KO mice had no significant change,but the body weight gain slowed down;the glucose tolerance increased,and the serum triglyceride content was lower;the accumulation of white fat decreased and brown fat accumulation increased.It was inferred that under the condition of long-term drinking cola,the lipid metabolism balance of CTRP6^-/-mice was better than that of wild-type mice.In the caloric restriction experiment,WT and KO mice were fed with alternate-day fasting for 14 weeks,and the ad libitum group was used as the control group.The study found that in the alternate day fasting group,the cumulative feed intake of the mice was significantly reduced,and the weight gain decreased,body fat accumulation is reduced,glucose tolerance is increased,blood lipids are reduced,and metabolism is improved.The expression of m RNA and protein abundance of brown fat marker genes UCP1 and PGC1αgenes increased in white adipose tissue after alternate day fasting.The level of PKA phosphorylation was significantly increased in alternate day fasting group by Western blot analysis.It is inferred that alternate day fasting promotes browning of white fat by activating PKA pathway.Behavioral analysis showed that alternate day fasting had no effect on the vitality and health of mice.Comparing the two genotypes of mice,it was found that compared with WT mice,the brown fat marker genes and PKA phosphorylation in the white adipose tissue of KO mice increased more greatly,which verified that CTRP6 gene deletion has the effect of promoting the browning of white adipose tissue.The effect of improving the metabolism of mice is more obvious under alternate day fasting.In summary,whether under high sugar or calorie restriction feed,CTRP6 gene deletion helps to maintain the balance of glucose and lipid metabolism,which is a potential target for the treatment of obesity and metabolic diseases.