This elevation in TPH1 activity, as well as the subsequent elevation in 5-HT reaching liver, is likely implicated in the pathogenesis of metabolic liver diseases, as pharmacological inhibition of TPH1 reduces weight gain and adiposity, improves insulin sensitivity, and ameliorates liver steatosis in mice fed a HFD 199,219,224,225,275,276. This evidence concerns the gene INS and fatty liver disease.