Building Competency in Diabetes Education THE ESSENTIALS

PATHOPHYSIOLOGY| 3-7

Figure 1. Glucose homeostasis: Daytime profile

Reprinted with permission from Owens et al (9)

Insulin is secreted by beta cells into the portal venous system (portal vein drains blood from the gastrointestinal (GI) tract and spleen to the liver) and 50% is removed by the liver. Unextracted insulin continues to systemic circulation where it binds to insulin receptors in target organs (5). Insulin has the following functions (4,5): • It allows glucose in the blood to enter body cells and be used as fuel. • It helps circulating FFAs to be stored as triglycerides in fat cells. • It helps convert glucose to glycerol, the basis for stored triglycerides in fat cells. • It stimulates the storage of amino acids as protein in muscle tissue. • It helps liver and muscle tissue store glycogen for future use. As it promotes storage, it suppresses hepatic glucose release. With current insulin therapy, the delivery of exogenous insulin is in the systemic circulation via blood supply of subcutaneous fat tissue bypassing the liver which does not mimic physiologic insulin production. The incretin effect In the fed state, the presence of food in the stomach and intestines leads to an increase in insulin and amylin (co-secreted with insulin from the beta cell) (8). Insulin release is stimulated by the release of incretin hormones such as glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) secreted from the stomach, small and large intestine