Liraglutide Induces Browning Of White Fat And Related MiRNAs Expression In Obese Mice

ObjectiveObesity has become a global epidemic,increasing the risk of diseases such as type2 diabetes,fatty liver disease,hypertension and so on.Liraglutide is a potential drug for management of obesity,which can not only reduce appetite,but also increase body energy expenditure by promoting the white fat browning,resulting in improving lipid metabolism and reducing weight.micro RNAs(miRNAs)constitute a class of short noncoding RNAs,which regulate gene expression by repressing post-transcriptional translation and promoting messenger RNA degradation,and have the functions of regulating browning remodeling of white fat and enhancing the heat production of brown fat.At present,there are few reports on the regulation of white fat Browning related miRNA by liraglutide.Therefore,our study aimed to analyze the effect of liraglutide on browning of white fat and its effect on browning related miRNAs in obese mice.Methods4-week-old C57BL/6 mice were randomly divided into normal diet group and high fat diet group after adaptive feeding for 1 week,and were fed with normal diet and 45%high-fat diet for 20 weeks respectively to establish obesity model.Mice conforming to the obesity model were further divided into two groups: high-fat group(HFD+NS)and liraglutide group(HFD+ LIRA).The mice were continued to be fed with 45% high fat diet with intervention.Normal diet group was set as normal control group(ND+NS).The HFD+ LIRA group was received daily subcutaneous injections with 0.2mg/kg liraglutide,and the ND+NS group and the HFD+NS group were subcutaneously injected with the same volume of saline once a day,respectively,for 12 weeks.During the intervention,the body weight of mice was measured every two weeks.After 12-week treatment,intraperitoneal glucose tolerance test and insulin tolerance test were performed to evaluate glucose metabolism.All mice were examined by CT for abdominal fat distribution.Serum of mice were collected to detect triglyceride(TG),total cholesterol(TC)and low density lipoprotein cholesterol(LDL-C).The adipose tissue of epididymis was stained with HE to observe the morphological changes of adipose tissue.The m RNA levels of uncoupled protein-1(UCP-1),peroxisome proliferator-activated receptor-coactivator-1α(PGC-1α/PPARGC1A),PR domain containing 16(PRDM16),and cell death-inducing DFFA-like effector A(CIDEA)in white fat were detected by real-time quantitative PCR.The protein expression level of UCP1 in white adipose tissue was detected by Western blot and immunohistochemical staining.Real-time fluorescence quantitative PCR was used to detect miRNAs expression levels associated with brown white fat in white adipose tissue.Target gene prediction databases Target Scan was used to predict the target genes of differentially expressed miRNAs.Results(1)After 12 weeks of liraglutide intervention,the body weight of mice in the HFD+LIRA group was significantly lower than that in the HFD+NS group,insulin resistance was improved,the difference was statistically significant(P< 0.05).(2)After 12 weeks of liraglutide intervention,the abdominal CT results of mice showed that the abdominal fat area of mice in the HFD+ LIRA group was significantly lower than that in the HFD+NS group at different lumbar plane(P<0.05).(3)After 12 weeks of liraglutide intervention,TG、TC and LDL-C levels in HFD+LIRA group were decreased compared with HFD+NS group(P < 0.05).(4)After 12 weeks of liraglutide administration,epidydimal white adipose tissue of mice was taken for HE staining to observe the cell morphology.The results showed that the volume of adipose cells in the epididymis of mice in the HFD+LIRA group decreased in the high-fat group.(5)After 12 weeks of liraglutide intervention,the m RNA expression levels of browning related genes PRDM16,UCP1,PGC-1α and CIDEA in epidydimal white adipose tissue of mice in HFD+LIRA group were significantly increased when compared with HFD+NS group,with statistical significance(P<0.05).Western blot and immunohistochemical staining results showed that the expression level of UCP1 in white adipose tissue of epididymis of mice in HFD+LIRA group was increased.(6)After 12 weeks of liraglutide intervention,the expression level of miRNAs associate with browning of white fat in the mice epididymal white adipose tissue was detected,the results showed that miR-196 a and miR-378 a which were positively with browning of white fat were increased,miR-155,miR-199 a and miR-382 which were negatively with browning of white fat were decreased(P<0.05).The target genes of differentially expressed miRNAs were predicted by target gene prediction databases Target Scan,the results showed that PRDM16 is a common target gene of miR-378 a,miR-155,miR-199 a and miR-382;PGC-1α is a common target gene of miR-196 a,miR-199 a and miR-382.Conclusion(1)Liraglutide significantly reduced body weight and improved insulin resistance in high-fat fed C57BL/6 mice.(2)Liraglutide administration can reduce the volume of white adipocytes.(3)Liraglutide can increase the Browning of white adipocytes and enhance the thermogenic function of adipose tissue in mice fed with high fat.(4)Liraglutide can induces Browning of epididymal white fat by regulating the expression of browning-related miRNAs.