INSIG1 and fatty liver disease: Additionally, downregulation of 3 hydroxysterol Δ14-reductase Tm7sf2 (an endoplasmic reticulum enzyme involved with cholesterol biosynthesis) and insulin induced gene 1 Insig1 (whose overexpression attenuates hepatic steatosis and plasma cholesterol levels induced by an atherogenic diet15) was noted (Fig. 1C).