Dipeptidyl peptidase 4 (DPP4), also known as CD26, is a multifunctional serine protease widely expressed on the surface of various cells, including epithelial, endothelial, immune, and pancreatic cells. It is a type II transmembrane glycoprotein that can also exist in a soluble form in body fluids. DPP4 plays a crucial role in regulating the bioactivity of numerous peptides by cleaving N-terminal dipeptides, particularly those with proline or alanine in the penultimate position. This enzyme is best known for its involvement in glucose homeostasis through the degradation of incretin hormones like glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), which are essential for postprandial insulin secretion. Inhibition of DPP4 has thus become a therapeutic target for type 2 diabetes, with DPP4 inhibitors being widely used as antihyperglycemic agents. Beyond glucose metabolism, DPP4 is implicated in various physiological and pathological processes, such as inflammation, immune function, and cancer progression. Additionally, elevated levels of circulating DPP4 have been associated with obesity and cardiovascular diseases, suggesting its potential role in linking metabolic disorders and vascular dysfunction.
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