Association of promoter methylation status of NRF2 and PNPLA3 genes in alcoholic liver disease

Background: Alcoholic liver disease (ALD) is the leading cause of chronic liver disease. In the liver, metabolism of alcohol occurs through multiple mechanisms and it results in the generation of various toxic products. Multiple genetic causes have been identified that are associated with the development and progression of ALD. The present study assessed the promoter site methylation status of nuclear factor erythroid 2-related factor 2 (NRF2) and patatin-like phospholipase domain-containing protein-3 (PNPLA3) genes in different subgroups of ALD.

Methods: The patients recruited were cases of alcohol dependence syndrome with hepatic dysfunction, compensated cirrhosis, decompensated cirrhosis, and acute-on-chronic liver failure due to alcohol as an etiology along with healthy control subjects. Routine biochemical investigations were performed along with methylation-specific polymerase chain reaction (MS-PCR) to qualitatively assess the promoter methylation status of NRF2 and PNPLA3 in all these cases.

Results: There was significant difference in methylation status of NRF2 gene in ALD when compared to healthy controls but there was no such difference in PNPLA3. All biochemical and clinical parameters studied were significantly different in subgroups of ALD except the serum aspartate aminotransferase (AST) level. Subgroups of ALD did not show any significant association with NRF2 or PNPLA3 methylation status. Gamma-glutamyl transferase (GGT) and creatinine levels in serum were significantly associated with the methylation status of NRF2 gene while no such association was seen with PNPLA3 gene. Model for end-stage liver disease (MELD) score varied differentially with NRF2 methylation and PNPLA3 methylation but there was no statistical significance.

Conclusions: The present study showed that methylation status of NRF2 and PNPLA3 genes could not differentiate between subgroups of alcoholic liver diseases. However, the unmethylation of NRF2 promoter is associated with higher serum levels of GGT.