Age-related fat deposition in multifidus muscle could be a marker for nonalcoholic fatty liver disease

Although nonalcoholic fatty liver disease (NAFLD) is associated with visceral obesity, the relationship between visceral fat accumulation and skeletal muscle steatosis in patients with NAFLD has not been established. We evaluated: (1) the relationship between multifidus muscular tissue steatosis, visceral fat accumulation, and biochemical data in a cross-sectional study, and (2) the influence of weight reduction on multifidus muscular tissue steatosis in a longitudinal study. Three hundred thirty-three NAFLD patients were enrolled. Hepatic steatosis, visceral fat area, and the multifidus muscle/subcutaneous fat attenuation ratio (MM/F ratio) were evaluated by computed tomography. To evaluate how weight reduction produced by diet and exercise affected the MM/F ratio, changes in the MM/F ratio were compared between weight reduction and non-weight reduction groups. There was a gender difference in MM/F ratios. The MM/F ratio was significantly correlated with age (male r = 0.613, P < 0.01; female r = 0.440, P < 0.01). The MM/F ratio was positively correlated with visceral fat area (male: r = 0.262, P < 0.01; female: r = 0.214, P < 0.01). A decrease in the MM/F ratio, concomitant with reduced visceral fat accumulation, led to alleviation of hepatic steatosis in 20 patients with weight reduction, but not in 22 patients without weight reduction. The MM/F ratio was closely related to aging and visceral fat accumulation. The MM/F ratio was improved by weight reduction, indicating that fat accumulation in the multifidus muscle evaluated by computed tomography might be a therapeutic indicator of NAFLD.