Background & Aims
The pathogenesis of non-alcoholic fatty liver disease (NAFLD) is affected by epigenetic
factors as well as by genetic variation.
Methods
We performed targeted-bisulfite sequencing to determine the levels of DNA methylation
of 4 CpG islands (CpG99, CpG71, CpG26, and CpG101) in the regulatory regions of PNPLA3, SAMM50, PARVB variant 1, and PARVB variant 2, respectively. We compared the levels of methylation of DNA in the livers
of the first and second sets of patients with mild (fibrosis stages 0 and 1) or advanced
(fibrosis stages 2 to 4) NAFLD and in those of patients with mild (F0 to F2) or advanced
(F3 and F4) chronic hepatitis C infection. The hepatic mRNA levels of PNPLA3, SAMM50, and PARVB were measured using qPCR.
Results
CpG26, which resides in the regulatory region of PARVB variant 1, was markedly hypomethylated in the livers of patients with advanced NAFLD.
Conversely, CpG99 in the regulatory region of PNPLA3 was substantially hypermethylated in these patients. These differences in DNA methylation
were replicated in a second set of patients with NAFLD or chronic hepatitis C. PNPLA3 mRNA levels in the liver of the same section of a biopsy specimen used for genomic
DNA preparation were lower in patients with advanced NAFLD compared with those with
mild NAFLD and correlated inversely with CpG99 methylation in liver DNA. Moreover,
the levels of CpG99 methylation and PNPLA3 mRNA were affected by the rs738409 genotype.
Conclusions
Hypomethylation of CpG26 and hypermethylation of CpG99 may contribute to the severity
of fibrosis in patients with NAFLD or chronic hepatitis C infection.
Graphical abstract
Graphical Abstract
Abbreviations:
NAFLD (non-alcoholic fatty liver disease), NASH (non-alcoholic steatohepatitis), GWAS (genome-wide association study), SNP (single-nucleotide polymorphism), PNPLA3 (patatin-like phospholipase domain containing 3), LD (linkage disequilibrium), SAMM50 (SAMM50 sorting and assembly machinery component), PARVB (parvin β), PCR (polymerase chain reaction), NAS (NAFLD activity score), HDL (high-density lipoprotein), SBP (systolic blood pressure), DBP (diastolic blood pressure), BMI (body mass index), qPCR (quantitative PCR), GAPDH (glyceraldehyde-3-phosphate dehydrogenase), bp (base position), HbA1c (hemoglobin A1c), AST (aspartate aminotransferase), ALT (alanine aminotransferase)Keywords
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Article info
Publication history
Published online: March 14, 2015
Accepted:
February 26,
2015
Received in revised form:
February 25,
2015
Received:
September 3,
2014
Identification
Copyright
© 2015 European Association for the Study of the Liver. Published by Elsevier Inc. All rights reserved.
