Hepatic Fat Fraction is Independently Associated with Myosteatosis: Insights from Chemical Shift MRI

Metabolic dysfunction–associated steatotic liver disease (MASLD) is prevalent, but its relationship with skeletal muscle quantity and quality remains unclear. To examine the association between hepatic fat fraction (HFF) and lumbar skeletal muscle fat content and cross-sectional area (CSA) using dual-echo Dixon chemical shift–encoded MRI (dual-echo CSE-MRI). This retrospective study included adults aged 18–65. Patients with excessive alcohol use, viral hepatitis, hepatic surgery or malignancy, or poor image quality were excluded. HFF was quantified using dual-echo CSE-MRI. Bilateral psoas major and paravertebral muscles were segmented at L3 to obtain CSA (cm2) and fat fraction (PMM FF, PVM FF). Subcutaneous adipose tissue thickness (SATT) was also recorded. Correlation and multivariate regression analyses were performed. A total of 520 participants were included (mean age 45.3 ± 11.3 years; 69.8% women). Increasing HFF severity was associated with higher PMM FF, PVM FF, fasting glucose, triglycerides, ALT, AST, and FIB-4 index (all p < 0.05). HFF correlated positively with PMM FF (r = 0.20), PVM FF (r = 0.19), and SATT (r = 0.11). In multivariate analysis, triglycerides (β = 0.227, p < 0.001), blood glucose (β = 0.233, p < 0.001), PMM FF (β = 0.181, p < 0.001), PVM CSA (β = 0.207, p < 0.001), and SATT (β = 0.118, p = 0.002) were independently associated with HFF. Hepatic fat accumulation is associated with intramuscular fat infiltration in non-elderly adults. The independent contribution of PMM FF highlights the potential association between myosteatosis and imaging-defined hepatic steatosis.