Visceral Adipose Tissue Area as an Independent Risk Factor for Elevated Liver Enzyme in Nonalcoholic Fatty Liver Disease

Chronic elevations in alanine aminotransferase (ALT) levels are associated with body composition. The aim of this study was to evaluate the relationship between elevated liver enzyme levels and the visceral tissue area in subjects with and without nonalcoholic fatty liver disease (NAFLD). An observational cohort study was conducted with subjects undergoing general health examinations. To evaluate the visceral and subcutaneous abdominal adipose tissue area, a computed tomography scan was performed. NAFLD was diagnosed if a person demonstrated fatty liver on ultrasonography without a history of significant alcohol consumption or chronic liver disease. Abnormal liver enzyme levels were based on ALT elevations according to the updated Asian definition. Of the 5100 subjects, 3712 (72.8%) met the inclusion criteria, and NAFLD was found in 1185 subjects. Elevated ALT values were positively correlated with body mass index, waist circumference, and subcutaneous and visceral adipose tissue area. These relationships were attenuated, although they remained significant in a dose-dependent manner, after adjusting for multiple liver injury risk factors. In addition, when body mass index and subcutaneous and visceral tissue areas were finally considered in combination, only visceral adipose tissue remained independently associated with elevated ALT levels in the ultrasonographically diagnosed NAFLD group (P for trend <0.001 for men and women). Elevated ALT levels were independently and dose-dependently associated with visceral fat accumulation in the healthy general population, especially in ultrasonographically diagnosed NAFLD patients. These results reemphasize the importance of visceral fat in the pathogenesis of NAFLD.