INSIG1 (Insulin-Induced Gene 1): INSIG1 is a protein encoded by the INSIG1 gene that plays a crucial role in regulating lipid metabolism and cholesterol balance within cells. INSIG1 functions as a vital mediator of the feedback mechanism controlling cholesterol synthesis and uptake. It works by binding to and inhibiting sterol regulatory element-binding proteins (SREBPs), which are transcription factors essential for expressing genes involved in cholesterol and fatty acid production. By regulating SREBP activity, INSIG1 helps maintain proper cellular lipid levels and prevents excessive cholesterol accumulation.