Similar to noradrenaline, 5-HT exacerbates insulin resistance by stimulating hepatic glucose output and impairing insulin signaling 197, enhances liver steatosis via 5-HT2A receptors on hepatocytes 198,199, and fibrogenesis (upregulation of α-SMA, TGF-β1, and extracellular matrix components) through activation of 5-HT2A and 5-HT2B receptors on hepatic stellate cells 200. This evidence concerns the gene INS and fatty liver disease.