Genetics of nonalcoholic fatty liver disease in Asian populations

Nonalcoholic fatty liver disease (NAFLD) is characterized by the accumulation of fat in the liver without any history of chronic alcohol consumption. It encompasses a wide spectrum of diseases that range from simple steatosis to nonalcoholic steatohepatitis. NAFLD is strongly associated with obesity, insulin resistance / type-2 diabetes mellitus and the metabolic syndrome. NAFLD is a complex disorder; environmental and genetic factors interact with NAFLD manifestation and determine its progression. In this review, an attempt was made to provide current information on the genetic variants of NAFLD in Asian populations. Literature search was performed by using PubMed, Medline and Google Scholar database. Candidate gene, validation and genomewide association studies (GWASs) were included in this review. A total of 41 studies fulfilled inclusion criteria of which 12 candidate gene studies exclusively focussed on the PNPLA3 gene and 17 other studies on other important candidate genes such as NCAN-CILP2, PPARG, AGTR1, FABP1, APOC3 etc. reported significant association with NAFLD. Eight validation studies identified associations of variants on PNPLA3, LYPLAL1, TM6SF2, ADIPOR2, STAT3, GCKR, SAMM50 etc. with NAFLD. Thus, so far, four GWASs have been conducted in Asian population that reported PNPLA3, SAMM50, PARVB and GATAD2A genes which were significantly associated with NAFLD. Findings indicate that PNPLA3, APOC3, PPARG, NCAN and GCKR genes emerge out to be the important biological markers associated with NAFLD.