Improvement Effect And Mechanisms Of T10c12-CLA On Non-alcoholic Fatty Liver Disease(NAFLD)Mice

Non-alcoholic fatty liver disease(NAFLD)is a common chronic metabolic disease.There is no cure for NAFLD.Therefore,it is very important to intervene in the occurrence and development of NAFLD.Conjugated linoleic acid(CLA)are fatty acids widely found in animal foods,of which trans 10,cis 12-conjugated linoleic acid(t10c12-CLA)is one of its main isomers,which has the effect of improving fat deposition and reducing body fat synthesis and presumably may have some therapeutic effects on NAFLD.However,commercial CLAs are mainly a mixture of multiple isomers,and feeding methods differ in feeding experiments,resulting in controversial effects of t10c12-CLA on NAFLD in mice.To eliminate the interference of the above factors,this study intends to take Rosa26pai/pai transgenic mice constructed in our laboratory,which can synthesize t10c12-CLA itself,as the research object,and construct the mice NAFLD model through high-fat diet(HFD),to explore the effect of t10c12-CLA on mice NAFLD and its mechanism.Firstly,5-week-old male wild-type(wt)and Rosa26pai/pai mice with similar body weight were selected and divided into four groups:wt group and Rosa26pai/pai group fed ordinary diet,wt+HFD group and Rosa26pai/pai+HFD group fed HFD diet.The body weight of mice was monitored weekly,and the mice were fed for 10 weeks(w)and 16 weeks,and the physiological and biochemical indexes and liver pathological changes of mice were detected.The results showed that there were no significant differences in body weight,serum alanine transaminase(ALT)and aspartate transaminase(AST)levels,and liver histopathology analysis between the wt group and Rosa26pai/pai group fed with normal diet,indicating that t10c12-CLA had no significant effect on mice fed with normal diet.However,compared with the wt group,the wt+HFD group showed a significant increase in body weight after 2 weeks of feeding,significant increases in serum ALT and AST levels at 10 and 16 weeks,and significant aggravation of liver lipid accumulation,inflammatory infiltration,and fibrosis,indicating that the HFD-induced NAFLD mice model was successfully established and reached Nonalcoholic steatohepatitis at 16 weeks.Meanwhile,compared with the wt+HFD group,the Rosa26pai/pai+HFD group showed a significant decrease in body weight after 2 weeks of feeding,significant decreases in serum ALT and AST levels at the same time point,and significant alleviation of liver lipid accumulation,inflammatory infiltration,and fibrosis,but still significantly higher than the Rosa26pai/pai group,indicating that t10c12-CLA had a significant improvement effect on the liver lipid accumulation,inflammatory infiltration,and fibrosis of HFD-induced NAFLD mice.The above results indicate that t10c12-CLA can significantly alleviate the liver pathology of NAFLD mice.Subsequently,to investigate the molecular mechanism by which t10c12-CLA improves hepatic lipid accumulation in NAFLD mice,this study examined the expression of biochemical indicators,lipid metabolism key factors,and signaling pathway-related proteins in the mice liver.The results showed no significant differences in the factors in the liver of wt and Rosa26pai/pai mice at 10 and 16 weeks.Compared to the wt group,the wt+HFD group of mice showed significant increases in liver TC and TG levels,Atgl,Hsl,Ppary,Fas,and Srebp1c transcription levels,and SREBP-lc protein expression at both time points,and a significant decrease in AMPK phosphorylation levels.Compared to the Rosa26pai/pai group,the Rosa26pai/pai+HFD group of mice showed significant increases in liver TC and TG levels,Atgl,Hsl,Fas,and Srebp-1c transcription levels,and SREBP-1c protein expression at both time points,and no significant differences in the rest.Compared to the wt+HFD group at 10 and 16 weeks,the Rosa26pai/pai+HFD group of mice at the same time points showed significant reductions in liver TC and TG levels,significant increases in Atgl and Hsl transcription levels,significant decreases in Ppary,Fas,and Srebp-1c transcription levels,significant increases in AMPK phosphorylation levels,and significant decreases in SREBP-lc protein expression.These results suggest that t10c12-CLA can alleviate hepatic lipid accumulation in NAFLD mice by reducing liver TC and TG levels,promoting triglyceride decomposition and metabolism,inhibiting fatty acid synthesis and metabolism,and regulating the AMPK/SREBP-1c signaling pathway.Furthermore,to investigate the potential therapeutic effects of t10c12-CLA on inflammation and fibrosis in NAFLD mice,this study further examined the expression of serum inflammatory biomarkers and liver inflammation and fibrosis-related factors.The results showed no significant differences in the levels of the examined factors between the wt and Rosa26pai/pai groups in both 10 and 16 weeks.Compared to the wt group,the levels of serum IL-6 and IL-1β,liver Il-6,Tnf-α and Il-1β transcription levels,α-SMA transcription levels,and protein expression were significantly increased in the wt+HFD group at both time points,while Il-10 transcription levels were significantly decreased.Compared to the Rosa26pai/pai group,the levels of serum IL-6 and IL-1β,liver Il-6 and Tnf-α transcription levels,and α-SMA protein expression were significantly increased in the Rosa26pai/pai+HFD group at both time points,while I1-10 transcription levels were significantly decreased,and no significant differences were observed in other examined factors.Compared to the wt+HFD group at both time points,the levels of serum IL-6 and IL-1β were significantly decreased in the Rosa26pai/pai+HFD group,and the levels of liver 11-6,Tnf-α and Il-1β transcription levels,α-SMA transcription levels,and protein expression were significantly decreased,while Il-10 transcription levels showed no significant differences.These results suggest that t10c12-CLA may alleviate the degree of liver inflammation and fibrosis in NAFLD mice by suppressing the expression of inflammatory and fibrosis-related factors.In conclusion,in HFD-induced NAFLD mice model,t10c12-CLA can promote triglyceride catabolism,inhibit fatty acid anabolism,regulate AMPK/SREBP-1c signaling pathway,reduce the expression levels of pro-inflammatory factors,fibrosis factors and proteins,and alleviate the degree of NAFLD liver lesions in mice.This study provides a solid theoretical basis for the application of10c12-CLA in the prevention and treatment of NAFLD.