However, when hepatic steatosis was induced with 8 weeks of HFD feeding, hepatic lipid droplet accumulation, NAFLD activity score (NAS), and hepatic TG levels were dramatically reduced in the liver of HFD-fed Tph1 GKO mice (Fig. 1f–h)28, indicating that reduced GDS production inhibits the progression of NAFLD. Here, TPH1 is linked to fatty liver disease.