title: Betaine supplement alleviates hepatic triglyceride accumulation of apolipoprotein E deficient mice via reducing methylation of peroxisomal proliferator-activated receptor alpha promoter.
abstract: BACKGROUND
  Betaine is a methyl donor and has been considered as a lipotropic effect substance. But its mechanism remains unclear. Hepatic steatosis is associated with abnormal expression of genes involved in hepatic lipid metabolism. DNA methylation contributes to the disregulation of gene expression. Here we hypothesized that betaine supplement and subsequent DNA methylation modifications alter the expression of genes that are involved in hepatic lipid metabolism and hence alleviate hepatic triglyceride accumulation.
  
  
  METHODS
  Male wild-type (WT) C57BL/6 mice (n = 6) were fed with the AIN-93 G diet. ApoE-/- mice (n = 12), weight-matched with the WT mice, were divided into two groups (n = 6 per group), and fed with the AIN-93 G diet and AIN-93 G supplemented with 2% betaine/100 g diet. Seven weeks after the intervention, mice were sacrificed. Liver betaine, choline, homocysteine concentration were measured by HPLC. Liver oxidants activity and triglyceride level were assessed by ultraviolet spectrophotometry. Finally, hepatic PPAR alpha gene and its target genes expression levels and the methylation status of the PPAR alpha gene were determined.
  
  
  RESULTS
  ApoE-/- mice had higher hepatic triglyceride and lower GSH-Px activity when compared with the WT mice. Betaine intervention reversed triglyceride deposit, enhanced SOD and GSH-Px activity in the liver. Interestingly, mice fed on betaine-supplemented diet showed a dramatic increase of hepatic choline concentration and a decrease of betaine and homocysteine concentration relative to the WT mice and the ApoE-/- mice absent with betaine intervention. Expression of PPAR alpha and CPT1 were decreased and expression of FAS was markedly increased in ApoE-/- mice. In parallel, PPAR alpha promoter methylation level were slightly increased in ApoE-/- mice though without significance. Betaine supplement upregulated expression of PPAR alpha and its target genes (CPT1, CYP2E1) and reversed hypermethylation of PPAR alpha promoter of ApoE-/- mice. Furthermore, PPAR alpha methylation was positively correlated with hepatic betaine concentration.
  
  
  CONCLUSIONS
  Our findings indicate that betaine supplement could alleviate hepatic triglyceride accumulation and improve antioxidant capacity by decreasing PPAR alpha promoter methylation and upregulating PPAR alpha and its target genes mRNA expression.
authors.affiliation: Guangdong Provincial Key Laboratory of Food, Nutrition and Health, Sun Yat-Sen University, Guangzhou, People's Republic of China.
authors.forename: Lijun
authors.initials: L
authors.lastname: Wang
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.forename: Yaozong
authors.initials: Y
authors.lastname: Tan
authors.forename: Jun
authors.initials: J
authors.lastname: Wei
authors.forename: Ying
authors.initials: Y
authors.lastname: Chang
authors.forename: Tianru
authors.initials: T
authors.lastname: Jin
authors.forename: Huilian
authors.initials: H
authors.lastname: Zhu
mesh_terms: D000818:Animals; D001057:Apolipoproteins E / Q000172:deficiency / Q000235:genetics; D001622:Betaine / Q000494:pharmacology*; D002334:Carnitine O-Palmitoyltransferase / Q000235:genetics / Q000378:metabolism; D002794:Choline / Q000378:metabolism; D019392:Cytochrome P-450 CYP2E1 / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation / Q000187:drug effects*; D054890:Fatty Acid Synthase, Type I / Q000235:genetics / Q000378:metabolism; D005526:Food, Formulated; D005786:Gene Expression Regulation / Q000187:drug effects; D005979:Glutathione Peroxidase / Q000235:genetics / Q000378:metabolism; D006710:Homocysteine / Q000378:metabolism; D050356:Lipid Metabolism / Q000235:genetics*; D008082:Lipotropic Agents / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D047493:PPAR alpha / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000187:drug effects; D015398:Signal Transduction; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D014280:Triglycerides / Q000378:metabolism*
chemical_list: D001057:Apolipoproteins E; D008082:Lipotropic Agents; D047493:PPAR alpha; D014280:Triglycerides; D006710:Homocysteine; D001622:Betaine; D005979:Glutathione Peroxidase; D019392:Cytochrome P-450 CYP2E1; D013482:Superoxide Dismutase; D002334:Carnitine O-Palmitoyltransferase; C518729:FASN protein, human; D054890:Fatty Acid Synthase, Type I; D002794:Choline