MC4R and metabolic dysfunction-associated steatohepatitis: MC4R mutations are associated with early-onset obesity and NAFLD in humans, and MC4RKO mice show the nonalcoholic steatohepatitis (NASH)-like hepatic phenotype by exhibiting an increased appetite when fed with a HFD (Vella et al., 2011; Arens et al., 2003; Itoh et al., 2011; Miyamura et al., 2011).