Published online Oct 8, 2016. doi: 10.4254/wjh.v8.i28.1194
Peer-review started: May 21, 2016
First decision: July 4, 2016
Revised: July 8, 2016
Accepted: August 27, 2016
Article in press: August 29, 2016
Published online: October 8, 2016
To clarify whether Agtr1a methylation is involved in the development of nonalcoholic steatohepatitis (NASH)-related liver fibrosis in adult rats.
A choline-deficient amino acid (CDAA) diet model was employed for methylation analysis of NASH-related liver fibrosis. Agtr1a methylation levels were measured in the livers of CDAA- and control choline-sufficient amino acid (CSAA)-fed rats for 8 and 12 wk using quantitative methylation-specific PCR. Hepatic stellate cells (HSCs) were isolated by collagenase digestion of the liver, followed by centrifugation of the crude cell suspension through a density gradient. Agtr1a methylation and its gene expression were also analyzed during the activation of HSCs.
The mean levels of Agtr1a methylation in the livers of CDAA-fed rats (11.5% and 18.6% at 8 and 12 wk, respectively) tended to be higher (P = 0.06 and 0.09, respectively) than those in the livers of CSAA-fed rats (2.1% and 5.3% at 8 and 12 wk, respectively). Agtr1a was not methylated at all in quiescent HSCs, but was clearly methylated in activated HSCs (13.8%, P < 0.01). Interestingly, although Agtr1a was hypermethylated, the Agtr1a mRNA level increased up to 2.2-fold (P < 0.05) in activated HSCs compared with that in quiescent HSCs, suggesting that Agtr1a methylation did not silence its expression but instead had the potential to upregulate its expression. These findings indicate that Agtr1a methylation and its upregulation of gene expression are associated with the development of NASH-related liver fibrosis.
This is the first study to show that DNA methylation is potentially involved in the regulation of a renin-angiotensin system-related gene expression during liver fibrosis.
Core tip: We report the first study to show that Agtr1a methylation occurred during the development of nonalcoholic steatohepatitis-related liver fibrosis. Interestingly, Agtr1a gene expression was upregulated during liver fibrosis, although Agtr1a was methylated. This study demonstrates for the first time that renin-angiotensin system-related gene expression is regulated by DNA methylation during liver fibrosis. This finding raises expectations about the therapeutic application of demethylating agents for the treatment of liver fibrosis.