Genetic factors contribute to variation in serum alanine aminotransferase activity independent of obesity and alcohol: A study in monozygotic and dizygotic twins

Background/Aims: This study aimed to determine the heritability of serum alanine aminotransferase (S-ALT) and fasting serum insulin (fS-insulin) concentration as well as determine the association of these measures with liver fat content in young adult monozygotic (MZ) and dizygotic (DZ) twins. Methods: Three hundred and thirteen individual twins were recruited from a population-based cohort (n = 4929). The study subjects represented a wide range of body mass indexes (BMI), were free of any diseases or regular medications and had an intake of less than two drinks of alcohol/day. To verify that S-ALT is a marker of liver fat, it was measured by proton magnetic resonance spectroscopy ((1)H MRS) in 66 subjects. Heritability estimations were performed using BMI-and gender-adjusted values. Results: Intro-pair correlations were significantly higher in the MZ twins than the DZ twins for both S-ALT (0.65 for MZ and 0.04 for DZ) and tS-insulin (0.58 and 0.34, respectively). Heritability of S-ALT was 55%, and that of IS-insulin 61%. In the 66 subjects S-ALT (r = 0.70 for women and r = 0.50 for men, p <= 0.01 for both) and fS-insulin (r = 0.58 and r = 0.59, respectively, p <= 0.01 for both) concentrations correlated significantly with liver fat content. Conclusions: These twin data suggest that approximately 60%, of the variation in S-ALT, a marker of liver fat content, is genetically determined. (c) 2009 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.