Dihydromyricetin Improves Liver Fat Deposition And Mechanism In Obese Mice Induced By High Fat Diet

[Background] Obesity is one of the most rapidly occurring metabolic diseases nowadays.It can induce metabolic disorders,oxidative stress damage,inflammation and many other diseases.The liver is an significant organ of body fat metabolism.The occurrence and development of obesity is closely related to oxidative stress,inflammation and the imbalance of liver lipid metabolism.Increased fat synthesis and reduced lipolysis are important causes of liver fat deposition leading to a range of hepatic metabolic diseases.Dihydromyricetin(DHM)is a phenolic hydroxy dihydroflavonoid extracted from snake grapes and is commonly used to treat diseases associated with inflammation and oxidative stress.Recent studies have shown that DHM can lower serum total cholesterol(TC)and triglyceride(TG)levels and increase high-density lipoprotein cholesterol(HDL-C)in hyperlipidemia rats.Deacetylase(sirtuins,sirt1)and AMP-dependent activated protein kinase(AMPK)are two key energy sensors that maintain the body's metabolic balance.SIRT1 is able to mediate AMPK through LKB1-dependent way.Studies have shown that SIRT1-AMPKexpression is significantly inhibited in obese conditions,and activation of SIRT1-AMPK improves hepatic steatosis.It has also been reported in the literature that DHM is involved in the SIRT1-AMPK signaling pathway in improving liver cell triglyceride accumulation and insulin resistance.Our group also confirmed that DHM can promote white fat browning in obese mice induced by high fat diets,thereby reducing the body weight of obese mice.But whether DHM can improve liver fat deposition in high-fat-induced obese mice is not clear.Thus,this study intends to further observe the effect of DHM on liver fat deposition in obese mice induced by high fat diet,and to explore its possible mechanism.[Objective]To investigate whether DHM can improve liver fat deposition in obese mice induced by high-fat diet,and whether its mechanism is related to oxidative stress injury,inflammation,and lipid metabolism imbalance.[Methods] 78 C57BL/6J mice were randomly divided into 6 groups:1.Normal diet(ND): Normal diet,nutrient distribution ratio: 70%carbohydrate,10% fat,20% protein,double Steamed water intragastric administration,once a day;2.High fat diet(HFD): high fat diet,nutrient distribution ratio: carbohydrate 20%,fat 60%,20% protein,double distilled water intragastric administration,once a day;the normal diet group and the high-fat diet group did or did not use low-dose dihydromyricetin(125mg/kg/d)and high-dose dihydromyricetin(250mg/kg/d)treatment respectively,so increased of four groups: 3.Normal diet+low dose dihydromyricetin group(ND+L-DHM): Normal diet,dihydro myricetin(125mg/ kg / d)intragastric administration,once a day;4.Normal diet+high dose dihydromyricetin group(ND+H-DHM group): Normal diet,dihydromyricetin(250mg/kg/d)intragastric administration,once a day;5.High-fat diet + low-dose dihydromyricetin group(HFD+L-DHM group): High fat diet,dihydromyricetin(125mg/kg/d)intragastric administration,once a day;6.High-fat diet +high-dose dihydromyricetin group(HFD+H-DHM group): High fat diet,dihydromyricetin(250mg/kg/d)intragastric administration.Body weight was measured every two weeks.After 16 weeks,blood was taken from the orbital vein and the animals were sacrificed.Automated biochemical analyzer for biochemical indicators: serum triglyceride(TG),total cholesterol(TC),high-density lipoprotein(HDL),serum low-density lipoprotein(LDL)..The adipose tissue of the subscapularis,inguen and epididymis was weighed,and liver fat deposition was observed by formaldehyde fixation,HE staining and oil red staining.liver MDA and SOD content were measured by colorimetric mothod,The mRNA expression of inflammation related factors in the liver: IL-6,IL-8,TNF?,lipid synthesis related genes: Acetyl-CoA carboxylase(ACC),sterol regulatory element binding Protein(SREBP-1),fatty acid synthase(FAS),lipidolysis related gene: peroxisome(PPAR?),palmitoylpalmitoyltransferase 1(CPT1),and regulating lipid synthesis and catabolism genes: SIRT1 and AMPK,were detected by Realtime PCR.The protein expression of liver SIRT1?AMPK,lipid synthesis related genes(ACC?SREBP-1?FAS)and lipidolysis related gene(PPAR??CPT1)were detected by Western Blot analysis.[Results] Compared with the ND group,the body weight and the body fat weight of the HFD group significantly increased,the TG?TC?LDL level significantly increased,and the HDL decreased.HE staining and oil red staining showed increased lipid droplet quantity and volume and increased fat deposition in the liver,The content of liver MDA significantly increased and the activity of SOD significantly decreased.Realtime PCR results showed that the mRNA expression of inflammatory factors IL-6,IL-8 and TNF? increased,the expression of fat synthesis factors(SREBP-1c,FAS,ACC1)increased,the expression of lipolysis-related factors(PPAR?,CPT1)decreased and the expression of SIRT1 and AMPK genes decreased.The protein expression of SIRT1 and AMPK was significantly decreased,the protein expression of lipid synthesis factors(SREBP-1c,FAS,ACC1)was increased,and lipid breakdown-related factors(PPAR?,CPT1)was decreased.DHM significantly reversed the above changes in the HFD group of mice;however,DHM had no significant effect on the above indicators of ND mice.[Conclusion] DHM can improve liver fat deposition in obese mice induced by high-fat diet,which may be related to inhibition of oxidative stress,inflammation and lipid synthesis,and promotion of lipidolysis.