Association of genetic variation in adaptor protein APPL1/APPL2 loci with non-alcoholic fatty liver disease

PLoS One. 2013 Aug 19;8(8):e71391. doi: 10.1371/journal.pone.0071391. eCollection 2013.

Abstract

The importance of genetics and epigenetic changes in the pathogenesis of non alcoholic fatty liver disease (NAFLD) has been increasingly recognized. Adiponectin has a central role in regulating glucose and lipid metabolism and controlling inflammation in insulin-sensitive tissues and low adiponectin levels have been linked to NAFLD. APPL1 and APPL2 are adaptor proteins that interact with the intracellular region of adiponectin receptors and mediate adiponectin signaling and its effects on metabolism. The aim of our study was the evaluation of a potential association between variants at APPL1 and APPL2 loci and NAFLD occurrence. The impact on liver damage and hepatic steatosis severity has been also evaluated. To this aim allele frequency and genotype distribution of APPL1- rs3806622 and -rs4640525 and APPL2-rs 11112412 variants were evaluated in 223 subjects with clinical diagnosis of NAFLD and compared with 231 healthy subjects. The impact of APPL1 and APPL2 SNPs on liver damage and hepatic steatosis severity has been also evaluated. The minor-allele combination APPL1-C/APPL2-A was associated with an increased risk of NAFLD (OR = 2.50 95% CI 1.45-4.32; p<0.001) even after adjustment for age, sex, body mass index, insulin resistance (HOMA-IR), triglycerides and adiponectin levels. This allele combination carrier had higher plasma alanine aminotransferase levels (Diff = 15.08 [7.60-22.57] p = 0.001) and an increased frequency of severe steatosis compared to the reference allele combination (OR = 3.88; 95% CI 1.582-9.531; p<0.001). In conclusion, C-APPL1/A-APPL2 allele combination is associated with NAFLD occurrence, with a more severe hepatic steatosis grade and with a reduced adiponectin cytoprotective effect on liver.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics*
  • Adaptor Proteins, Signal Transducing / metabolism
  • Adiponectin / genetics
  • Adiponectin / metabolism
  • Adult
  • Aged
  • Alanine Transaminase / blood
  • Alleles
  • Case-Control Studies
  • Fatty Liver / genetics*
  • Fatty Liver / metabolism
  • Fatty Liver / pathology
  • Female
  • Gene Frequency
  • Genetic Loci*
  • Genotype
  • Humans
  • Male
  • Middle Aged
  • Non-alcoholic Fatty Liver Disease
  • Polymorphism, Single Nucleotide*
  • Receptors, Adiponectin / genetics
  • Receptors, Adiponectin / metabolism
  • Severity of Illness Index

Substances

  • ADIPOQ protein, human
  • APPL1 protein, human
  • APPL2 protein, human
  • Adaptor Proteins, Signal Transducing
  • Adiponectin
  • Receptors, Adiponectin
  • Alanine Transaminase

Grants and funding

This work was supported by the Second University of Naples. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.