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Muscle fat content is strongly associated with NASH: A longitudinal study in patients with morbid obesity
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April 14 2021
Taken together, our data support that a high muscle fat content, rather than a low muscle mass, is strongly and independently associated with NASH in patients with obesity and NAFLD. After a therapeutic intervention, the lowering of muscle fat content was robustly associated with histological improvement. These data pave the way for the exploration of muscle fat content as a potential marker and perhaps a pathophysiological contributor or a therapeutic target for NASH in NAFLD.
"initiation of ART among HIV-infected persons was associated with an increase in truncal skeletal muscle area, which is likely a reflection of increased fat within the muscle rather than an increase in high-quality skeletal muscle.....Increased fatty muscle has been associated with weakness, falls, and a decline in physical activity among older adults; similar clinical significance should be established among HIV-infected middle-aged and older adults. Last, interventions such as diet and exercise should be investigated as potential therapies to limit fat accumulation within skeletal muscle and prevent long-term functional and metabolic complications."
Highlights
• Muscle fat content is higher in patients with obesity and NASH than in those with obesity and NAFL.
• There is no low muscle mass in patients with obesity-associated NASH.
• Muscle fat content is strongly associated with cardinal histological features of NASH.
• NASH improvement is associated with a significant decrease of muscle fat content.
Background & Aims
Studies exploring the relationship between muscle fat content and non-alcoholic fatty liver disease (NAFLD) are scarce. Herein, we aimed to evaluate the association of muscle mass and fatty infiltration with biopsy-assessed NAFLD in patients with obesity.
Methods
At inclusion (n = 184) and 12 months after a dietary intervention (n = 15) or bariatric surgery (n = 24), we evaluated NAFLD by liver biopsy, and skeletal muscle mass index (SMI) by CT (CT-SMI) or bioelectrical impedance analysis (BIA-SMI). We developed an index to evaluate absolute fat content in muscle (skeletal muscle fat index [SMFI]) from CT-based psoas muscle density (SMFIPsoas).
Results
Muscle mass was higher in patients with NAFLD than in those without (CT-SMI 56.8 ± 9.9 vs. 47.4 ± 6.5 cm2/m2, p <0.0001). There was no association between sarcopenia and non-alcoholic steatohepatitis (NASH). SMFIPsoas was higher in NASH ≥F2 and early NASH F0-1 than in NAFL (78.5 ± 23.6 and 73.1 ± 15.6 vs. 61.2 ± 12.6, p <0.001). A 1-point change in the score for any of the individual cardinal NASH features (i.e. steatosis, inflammation or ballooning) was associated with an increase in SMFIPsoas (all p <0.05). The association between SMFIPsoas and NASH was highly significant even after adjustment for multiple confounders (all p <0.025). After intervention (n = 39), NASH improvement, defined by NAFLD activity score <3 or a 2-point score reduction, was achieved in more than 75% of patients (n = 25 or n = 27, respectively) that had pre-established NASH at inclusion (n = 32) and was associated with a significant decrease in SMFIPsoas (p <0.001). Strikingly, all patients who had ≥11% reduction in SMFIPsoas achieved NASH improvement (14/14, p <0.05).
Conclusions
Muscle fat content, but not muscle mass, is strongly and independently associated with NASH. All individuals who achieved a ≥11% decrease in SMFIPsoas after intervention improved their NASH. These data indicate that muscle fatty infiltration could be a potential marker for (and perhaps a pathophysiological contributor to) NASH.
Lay summary
The fat content in skeletal muscles is highly reflective of the severity of non-alcoholic fatty liver disease (NAFLD) in patients with morbid obesity. In particular, muscle fat content is strongly associated with non-alcoholic steatohepatitis (NASH) and decreases upon NASH improvement. These data indicate that muscle fatty infiltration could be a marker and possible pathophysiological contributor to NASH.
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