title: Heritability of Hepatic Fibrosis and Steatosis Based on a Prospective Twin Study.
abstract: OBJECTIVE
  Little is known about the heritability of hepatic fibrosis, and the heritability of hepatic steatosis has not been assessed systematically in adults. We investigated the heritability of hepatic fibrosis and steatosis in a community-dwelling twin cohort.
  
  
  METHODS
  We performed a cross-sectional analysis of a cohort of well-characterized twins residing in Southern California including 60 pairs of twins (42 monozygotic and 18 dizygotic; average age, 45.7 ± 22.1 y; average body mass index, 26.4 ± 5.7 kg/m(2)). We collected data on medical history, physical examinations, fasting laboratory test results, and liver health; all participants underwent an advanced magnetic resonance imaging (MRI) examination of the liver from January 2012 through January 2015. Hepatic steatosis was quantified noninvasively by MRI and determined based on the proton-density fat fraction (MRI-PDFF); liver fibrosis was measured based on stiffness measured by magnetic resonance elastography.
  
  
  RESULTS
  Twenty-six of the 120 subjects (21.7%) had nonalcoholic fatty liver disease (defined as MRI-PDFF ≥ 5% after exclusion of other causes of hepatic steatosis). The presence of hepatic steatosis correlated between monozygotic twins (r(2) = 0.70; P < .0001) but not between dizygotic twins (r(2) = 0.36; P = .2). The level of liver fibrosis also correlated between monozygotic twins (r(2) = 0.48; P < .002) but not between dizygotic twins (r(2) = 0.12; P = .7). In multivariable models adjusted for age, sex, and ethnicity, the heritability of hepatic steatosis (based on MRI-PDFF) was 0.52 (95% confidence interval, 0.31-0.73; P < 1.1 × 10(-11)) and the heritability of hepatic fibrosis (based on liver stiffness) was 0.5 (95% confidence interval, 0.28-0.72; P <6.1 × 10(-11)).
  
  
  CONCLUSIONS
  A study of twins provides evidence that hepatic steatosis and hepatic fibrosis are heritable traits.
authors: NAFLD Translational Research Unit, University of California, San Diego, La Jolla, California; Division of Gastroenterology, Department of Medicine, University of California, San Diego, La Jolla, California; Division of Epidemiology, Department of Family Medicine and Public Health, University of California, San Diego, La Jolla, California. Electronic address: roloomba@ucsd.edu.
authors: Rohit
authors: R
authors: Loomba
authors: Human Biology, J. Craig Venter Institute, La Jolla, California.
authors: Nicholas
authors: N
authors: Schork
authors: Department of Radiology, University of California, San Diego, La Jolla, California.
authors: Chi-Hua
authors: CH
authors: Chen
authors: NAFLD Translational Research Unit, University of California, San Diego, La Jolla, California.
authors: Ricki
authors: R
authors: Bettencourt
authors: NAFLD Translational Research Unit, University of California, San Diego, La Jolla, California.
authors: Ana
authors: A
authors: Bhatt
authors: NAFLD Translational Research Unit, University of California, San Diego, La Jolla, California.
authors: Brandon
authors: B
authors: Ang
authors: NAFLD Translational Research Unit, University of California, San Diego, La Jolla, California.
authors: Phirum
authors: P
authors: Nguyen
authors: NAFLD Translational Research Unit, University of California, San Diego, La Jolla, California.
authors: Carolyn
authors: C
authors: Hernandez
authors: NAFLD Translational Research Unit, University of California, San Diego, La Jolla, California.
authors: Lisa
authors: L
authors: Richards
authors: NAFLD Translational Research Unit, University of California, San Diego, La Jolla, California.
authors: Joanie
authors: J
authors: Salotti
authors: NAFLD Translational Research Unit, University of California, San Diego, La Jolla, California.
authors: Steven
authors: S
authors: Lin
authors: Division of Gastroenterology, Department of Medicine, University of California, San Diego, La Jolla, California.
authors: Ekihiro
authors: E
authors: Seki
authors: Human Biology, J. Craig Venter Institute, La Jolla, California.
authors: Karen E
authors: KE
authors: Nelson
authors: Liver Imaging Group, University of California, San Diego, La Jolla, California.
authors: Claude B
authors: CB
authors: Sirlin
authors: Division of Gastroenterology, Department of Medicine, University of California, San Diego, La Jolla, California.
authors: David
authors: D
authors: Brenner
mesh_terms: D000328:Adult; D000368:Aged; D002140:California; D016009:Chi-Square Distribution; D003430:Cross-Sectional Studies; D054459:Elasticity Imaging Techniques; D005260:Female; D020022:Genetic Predisposition to Disease; D040941:Heredity; D006801:Humans; D008103:Liver Cirrhosis / Q000175:diagnosis / Q000235:genetics*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D065626:Non-alcoholic Fatty Liver Disease / Q000175:diagnosis / Q000235:genetics*; D010641:Phenotype; D011446:Prospective Studies; D012307:Risk Factors; D014429:Twins, Dizygotic / Q000235:genetics*; D014430:Twins, Monozygotic / Q000235:genetics*
keywords: Fatty Liver; Genetic Factors; NAFLD; NASH