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