| Background: NNMT can methylate nicotinamide(a form of Vitamin B3)to produce 1-methylnicotinamide(MNAM).Some studies have shown that a single exercise,such as swimming for 90 minutes,can increase the liver NNMT activity by about 2-3 times.GEO database showed that the expression of NNMT in human skeletal muscle increased significantly after exercises.NNMT is mainly expressed in the liver,but its role in the liver remains largely unknown.It has been found that inhibiting the expression of NNMT in liver in vivo can change the metabolism of glucose and cholesterol,suggesting that NNMT plays an important role in regulating glucose and lipid metabolism.PPAR? is a transcription factor that regulates the metabolism of lipids,carbohydrates and amino acids.When activated by ligands(such as polyunsaturated fatty acids and drugs for the treatment of dyslipidemia,PPAR? promotes the catabolism of lipid.Exercise can regulate the expression of PPAR ? in the liver and improve the disorder of lipid metabolism in fatty liver.therefore,the role of NNMT in the liver is worthy of further study.Objective: The purpose of this study is to explore the effect of Nnmt in liver on lipid metabolism in mice,and to use specific agonists for PPAR?? to explore whether NNMTPPAR? could regulate the process of fatty acids oxidation in mice.It will also provide new ideas on how exercise would affect liver metabolism.Methods: Forty 8-week-old SPF grade C57BL/6J male mice were purchased and acclimated for one week.Then they were randomly divided into control group(sh Control,n=20)and liver NNMT knockdown group(sh NNMT,n=20).The knock-down efficiency of Nnmt by sh RNA delivered by adeno-virus injected through tail weins,was verified by Q-PCR and Western blot.These virus injected mice were then divided into two groups respectively for injection of WY14643(PPAR? agonist)at the dose of 10 mg/kg.In addition,the control mice without virus injection were intervened for 2 to 3 weeks.At the end of the intervention,the liver and serum of mice were collectedand blood lipids,cholesterol and the expression of lipid metabolism-related genes and PPAR target genes after intervention were assessed.Statistical methods: Independent sample t-test was used for comparison between the two groups,and one-way analysis of variance(one-way ANOVA)was used for comparison between groups.The data is analyzed using Graphpad Prism 5,and the result is displayed as Mean ± SEM.p < 0.05 means that there is a statistically significant difference between the two groups.Results: 1.There was no significant difference in body weight and food intake before and after the adenovirus injection.2.The expression of m RNA(p < 0.001)and the content of protein(p < 0.001)in the liver of sh NNMT group were significantly lower than those of sh Control group.3.Compared with sh Control group,sh NNMT group had signicantly higher serum cholesterol(p < 0.01)and free fatty acid(p < 0.05)but lower fasting blood glucose(p < 0.01).4.Compared with sh Control group,sh NNMT group had signicantly lower expression of PPAR ?(p < 0.05),CYP4A10(p < 0.05),CYP4A14(p < 0.05),PGC-1?(p < 0.05),Acox1(p < 0.01),G6P(p < 0.05)and FBP1(p < 0.01)PEPCK gene expression is slightly higher in sh NNMT group,but the difference did not reach statistical significance.5.After injection of PPAR ? agonist(WY14643).Compared with sh Control+ WY group,the gene expression of PPAR(p < 0.05)was significantly higher than that of(sh Control)in placebo group.Compared with sh NNMT group,cyp4A10(p < 0.01)gene expression increased significantly in sh NNMT+WY group after injection of PPAR ? agonist,and decreased significantly compared with sh Control+WY group(p < 0.01).Compared with sh NNMT group,cyp4A14(p < 0.01)gene expression increased significantly in sh NNMT+WY group after injection of PPAR ? agonist,and decreased significantly compared with sh Control+WY group(p < 0.01).Compared with sh NNMT group,ACOX1(p < 0.01)gene expression in sh NNMT+WY group increased significantly after injection of PPAR ? agonist,and decreased compared with sh Control+WY group,but there was no significant difference.Conclusion: 1.Down-regulation of NNMT expression decreased the expression of PPAR ? and its target genes,and increased serum and liver cholesterol.2.Using PPAR agonists(WY14643),our data verified that NNMT affects fatty acid oxidation by affecting PPAR? activity,which provides a theoretical basis for further study of the function of NNMT. |
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