What is the primary metabolic action of insulin?

What is the primary metabolic action of insulin?

• A. Lowering blood glucose by promoting cellular uptake of glucose
• B. Increasing hepatic glucose production
• C. Inhibiting glucose transport into cells
• D. Increasing renal excretion of glucose

Answer: (A)

Insulin’s main job is to lower blood glucose by helping glucose move into cells. It signals muscle and fat cells to bring GLUT4 transporters to the cell surface, so glucose enters these cells to be used for energy or stored as glycogen or fat. In the liver, insulin also promotes glycogen synthesis and suppresses glucose production, further reducing circulating glucose after meals. So the key action is promoting cellular glucose uptake, which lowers blood glucose levels. The other ideas describe effects opposite to insulin’s action: increasing hepatic glucose production would raise blood glucose, which insulin does not do; inhibiting glucose transport into cells would prevent uptake, opposite to what insulin accomplishes; and increasing renal glucose excretion isn’t how insulin lowers glucose—in fact, insulin makes more glucose available to cells.

Insulin’s main job is to lower blood glucose by helping glucose move into cells. It signals muscle and fat cells to bring GLUT4 transporters to the cell surface, so glucose enters these cells to be used for energy or stored as glycogen or fat. In the liver, insulin also promotes glycogen synthesis and suppresses glucose production, further reducing circulating glucose after meals. So the key action is promoting cellular glucose uptake, which lowers blood glucose levels.

The other ideas describe effects opposite to insulin’s action: increasing hepatic glucose production would raise blood glucose, which insulin does not do; inhibiting glucose transport into cells would prevent uptake, opposite to what insulin accomplishes; and increasing renal glucose excretion isn’t how insulin lowers glucose—in fact, insulin makes more glucose available to cells.