HTR5A and metabolic dysfunction-associated steatotic liver disease: Furthermore, previous results from our laboratory, which demonstrate that reduced 5-HT expression in the SI due to capsaicin-induced blockade of nerve signals is related to milder hepatic steatosis (Ko et al., 2021; Inoue et al., 2018; Kamimura et al., 2018; Nagoya et al., 2020), also support the conclusion that the 5-HT-liver-HTR2A axis is a key factor in NAFLD progression.