Effect And Mechanism Of Palmitoleic Acid On Obesity-Related Insulin Resistance And Non-alcoholic Fatty Liver Disease

Objective:1.To explore the related mechanism of palmitoleic acid on insulin resistance in obese mice induced by high fat diet.2.To explore the effect and mechanism of palmitoleic acid on mice with nonalcoholic steatohepatitis induced by methionine and choline deficient diet.Methods:1.Mechanism of palmitoleic acid on insulin resistance in obese mice:6-weekold C57BL/6J mice were fed with chow diet or high-fat diet respectively for 12 weeks.At the 13^thweek,the mice were given BSA,oleic acid and palmitoleic acid by gavage,respectively,and were continuously maintained on chow diet or high-fat diet for 6 weeks.The glucose tolerance test was performed at the 11th week.At the 18th week,the blood,liver,fat,colon fecal samples of mice were collected.The composition of gut microbiota,macrophage infiltration and inflammatory response in colon,adipose tissue and liver tissue of mice,and diacylglycerol levels in adipose tissue and liver of mice were detected.2.Effects of mechanism of palmitoleic acid on non-alcoholic steatohepatitis mice:8-week-old C57BL/6J mice were fed with chow diet,methionine and choline sufficient diet or methionine and choline deficient diet for 5 weeks,respectively.At the 6th week,those mice fed with methionine and choline deficiency groups were given BSA,oleic acid and palmitoleic acid by gavage,respectively,and continued to be fed and gavaged for 4 weeks.At the 9th week,blood and liver tissue of mice were collected.Serum and liver triglyceride levels,liver injury,inflammation and fibrosis levels were measured.The expression levels of CD36 and NLRP3 and the phosphorylation levels of AMPK in liver were detected.3.The effect of palmitoleic acid on macrophage inflammation:Macrophages were treated with 50 μmol/L palmitoleic acid for 24 h,and then cultured with 125μmol/L palmitic acid（high fatty acid stimulation）for 24 h.RAW 264.7 cells were infected with Ad-GFP and Ad-CD36 adenovirus respectively,and then were treated with 50 μmol/L palmitoleic acid for 24 h,and 125 μmol/L palmitic acid（high fatty acid stimulation）for another 24h.CD36 expression and inflammatory response in macrophages,NLRP3 expression and AMPK phosphorylation in macrophages were detected.Results:（1）Palmitoleic acid can improve the insulin resistance,decrease the abundance of firmicutes and increase the abundance of bacteroides,change the composition of gut microbiota,improve intestinal barrier,and reduce the macrophage infiltration and inflammatory response in colon,fat and liver tissues in obese mice induced by high-fat diet.However,palmitoleic acid does not reduce diacylglycerol（DAG）levels in liver and fat of obese mice induced by high-fat diet.Therefore,palmitoleic acid can improve insulin resistance,alter intestinal flora,and reduce tissue inflammation by an independent-manner of DAG.（2）Palmitoleic acid can improve the liver inflammation and fibrosis in mice with non-alcoholic steatohepatitis induced by methionine and choline deficient diet,decrease the expression of CD36 and NLRP3 in liver tissue,and increase the phosphorylation level of AMPK.（3）Under the stimulation of palmitic acid（high fatty acid stimulation）,the expression of CD36 in macrophages increases significantly,accompanied by increased inflammatory response.Palmitoleic acid can significantly reduce the expression of CD36 in inflammatory macrophages,and reduce the mRNA levels of inflammatory cytokines IL-1β,IL-6 and TNF-α in response to high fatty acid stimulation.The inflammatory response of macrophages to palmitic acid（high fatty acid stimulation）and CD36 expression level are further increased when macrophages overexpressed CD36,and NLRP3 level increases significantly and AMPK phosphorylation levels decreases significantly.Palmitoleic acid pretreatment reduces CD36 and NLRP3 levels and increases AMPK phosphorylation level.Conclusion:1.In this study,palmitoleic acid can improve the insulin resistance,decrease the abundance of firmicutes and increase the abundance of bacteroides,change the composition of gut microbiota,improve intestinal barrier,and reduce the macrophage infiltration and inflammatory response in colon,fat and liver tissues in obese mice induced by high-fat diet.However,palmitoleic acid does not reduce diacylglycerol（DAG）levels in liver and fat of obese mice induced by high-fat diet.Therefore,palmitoleic acid can improve insulin resistance,alter intestinal flora,and reduce tissue inflammation by an independent-manner of DAG.2.Palmitoleic acid may ameliorate nonalcoholic steatohepatitis by altering CD36/NLRP3 and CD36/AMPK signaling pathways in inflammatory macrophages.