The Effect Of Berberine On Nonalcoholic Fatty Liver Induced By A High-fat Diet In SD Rats

Aims/hypothesis Berberine can alleviate fatty liver in obese db/db and ob/ob mice, which is accompanied by mRNA levels of hepatic and muscular genes that enhance fatty acid oxidation and reduce lipogenesis. There is an undisputed link between high calories food and the development of nonalcoholic fatty liver disease(NAFLD), but the mechanisms of fat accumulation in hepatocytes resulted from food inhibits (environmental factor) and berberine altering mRNA expression of some genes still remain unclear. Epigenetic factors such as DNA methylation, are involved in the interaction between genes and environment. So it is proposed that DNA methylation play a role in the pathogenesis of NAFLD and berberine reduce hepatic fat content by affecting DNA methylation of key genes involved in lipid metabolism. Therefore we investigated 1) whether berberine has the same beneficial effect on NAFLD induced by a high-fat diet,2) downregulation of theses genes involved in hepatic lipid metabolism is affected by epigenetic (DNA methylation) factors, and 3) whether BBR improves fatty liver through demethylation of promoters of key genes.Methods After 8 weeks of high-fat-diet, SD rats were divided randomly into two groups, one of which were treated with berberine (BBR) orally at 200mg-kg-l-d-l) (n=8) and the other with placebo (n=8), for sixteen weeks. SD rats were fed by normal diet as normal control. mRNA level of candidate genes in liver were analyzed and hepatic triglyceride (TG) content were measured in three groups. The CpGs methylation status was determined by bisulphite direct sequencing of the PCR amplificates of genes promoter and the classic clone/sequencing methods. We also examined the triglyceride content of lipoproteins that were fractionated by fast protein liquid chromatography (FPLC).Results Treatment of high-fat feeding rats with BBR for 16 weeks reduced body weight by 14.2%, liver weight by 21% and visceral fat mass by 42.8%. BBR treatment for 16 weeks significantly improved hepatic fat accumulation in NAFLD rats, as indicated by a reduced hepatic triglyceride (by 14%). A high-fat-diet greatly decreased mRNA levels of CPT-la, MTTP and LDLR in liver, and berberine significantly increased the expression of these genes. TG-rich VLDL particles were significantly higher in BBR-treatment group than in control group fed with a high-fat diet according to area under the curve (AUC). DNA methylation level of MTTP promoter (the mean methylation level and three out of five CpG islands) of rats with NAFLD was elevated in liver compared with normal group, while BBR treatment resulted in lower mean methylation levels and lower levels of DNA methylation at-174,-113 and-20 CpG sites within the MTTP promoter in the liver of HFD-fed rats with NAFLD. Of particular note, an inverse correlation was found between the expression level of MTTP mRNA and the degrees of DNA methylation at-113 and-20 CpG sites (site-113, r=-0.636,p=0.026; site-20, r=-0.726,p=0.008). However, DNA methylation was not found in LDLR and CPT-la promoter.Conclusions/interpretation BBR can alleviate HFD-elicited NAFLD in SD rat. DNA methylation of MTTP promoter is likely to be involved in the pathogenesis of NAFLD induced by high-fat-diet and BBR reduces hepatic fat content, at least partially by reversing the methylation of MTTP promoter.