Human liver biopsy of different phases from control to NASH

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disorder in industrialized countries. Liver samples from morbidly obese patients (N=45) with all stages of NAFLD and controls (N=18) were analysed by array-based DNA methylation and mRNA expression profiling. NAFLD-specific expression and methylation differences were seen for nine genes coding for key enzymes in intermediate metabolism (including PC, ACLY, PLCG1) and insulin/insulin-like signalling (including IGF1, IGFBP2, PRKCE) and replicated by bisulfite pyrosequening (independent N=39). Transcription factor binding sites at NAFLD-specific CpG sites were >1000-fold enriched for ZNF274, PGC1A and SREBP2. Intra-individual comparison of liver biopsies before and after bariatric surgery showed NAFLD-associated methylation changes to be partially reversible. Post-bariatric and NAFLD-specific methylation signatures were clearly distinct both in gene-ontology and transcription factor binding site analyses, with >400-fold enrichment of NRF1, HSF1 and ESRRA sites. Our findings provide one of the first examples of treatment-induced epigenetic organ remodelling in humans.