Background and aims: Non-alcoholic fatty liver disease (NAFLD) increases cardiovascular
morbidity and mortality, and carries poor long-term hepatic prognosis. Data about the role of
genetic and environmental factors in the hepatic lipid accumulation are limited. The aim of the
study was to evaluate the genetic and environmental impact on the hepatic lipid accumulation
within a cohort of adult twin pairs.
Patients and methods: We investigated 182 twin subjects [monozygotic (MZ, n 5 114) and
dizygotic (DZ, n 5 68) same-gender twins (age 56.0 ± 9.6 years; BMI 27.5 ± 5.0 kg/m2
; females
65.9%)] who underwent computed tomography (CT) with a 256-slice scanner. Using nonenhanced CT-images, we calculated the average value of hepatic attenuation [expressed in
Hounsfield unit (HU)] suggesting hepatic lipid content. Crude data were adjusted to age, sex, BMI
and HbA1c values. Intra-pair correlations were established, and structural equation models were
used for quantifying the contribution of additive genetic (A), common environmental (C) and
unique environmental (E) components to the investigated phenotype.
Results: The study cohort represented a moderately overweight, middle-aged Caucasian population. There was no significant difference between MZ and DZ twin subjects regarding hepatic
CT-attenuation (57.9 ± 12.6 HU and 59.3 ± 11.7 HU, respectively; p 5 0.747). Age, sex, BMI and
HbA1c adjusted co-twin correlations between the siblings showed that MZ twins have stronger
correlations of HU values than DZ twins (rMZ 5 0.592, p < 0.001; rDZ 5 0.047, p 5 0.690,
respectively). Using the structural equation model, a moderate additive genetic dependence (A:
38%, 95% CI 15–58%) and a greater unique environmental influence (E: 62%, 95% CI 42–85%) was
found. Common environmental influence was not identified (C: 0%).
Conclusion: The results of our classical CT-based twin study revealed moderate genetic and
greater environmental influences on the phenotypic appearance of hepatic steatosis, commonly
referred to as NAFLD. Favorable changes of modifiable environmental factors are of great
importance in preventing or treating NAFLD