The PNPLA3 rs738409 C>G variant influences the association between low skeletal muscle mass and NAFLD: the Shanghai Changfeng Study

BACKGROUND Age-related skeletal muscle loss and patatin-like phospholipase domain-containing 3 (PNPLA3) polymorphisms are both associated with increased liver steatosis and fibrosis in the absence of obesity. AIM To investigate the influence of PNPLA3 polymorphism on the relationship between skeletal muscle loss and non-alcoholic fatty liver disease (NAFLD). METHODS Liver fat content was measured using a quantitative ultrasound method, and liver fibrosis was assessed by NAFLD fibrosis, BARD and FIB-4 scores in 3969 Chinese adults. The degree of sarcopenia was measured by weight-adjusted appendicular skeletal muscle mass (ASM% = appendicular skeletal muscle mass(kg)/body weight(kg)  100%). RESULTS The NAFLD proportion increased from 19.9% to 41.2% in men and 26.3% to 42.3% in women with decreasing ASM% quartiles (P < 0.001). Low ASM% was inversely associated with NAFLD in PNPLA3 CC (odds ratio [OR]: men, 0.735 [0.610-0.885] and women, 0.812 [0.718-0.918], both P = 0.001) and CG (OR: men, 0.673 [0.573-0.790] and women, 0.798 [0.713-0.893], both P < 0.001) but not GG genotype carriers. The association remained significant after adjustment for age, cigarette smoking, fat mass, interaction between fat mass and ASM%, obesity, diabetes and all components of metabolic syndrome. Subgroup analyses found that PNPLA3 GG gene variant did not increase the risk for NAFLD in individuals with low ASM% regardless of obesity status. Low ASM% also increased risk for liver fibrosis (all P < 0.05), which became insignificant after multiple adjustments. CONCLUSIONS Low ASM% is associated with NAFLD and liver fibrosis. Dissociation of sarcopenia and NAFLD was found in PNPLA3 GG genotype carriers. A stratification based on PNPLA3 genotypes might facilitate personalised treatment for NAFLD.