Orosomucoid (ORM) or alpha-1-acid glycoprotein (α1AGp,[1]AGP or AAG) is an acute phase protein found in plasma. It is an alpha-globulinglycoprotein and is modulated by two polymorphic genes. It is synthesized primarily in hepatocytes and has a normal plasma concentration between 0.6–1.2 mg/mL (1–3% plasma protein).[2] Plasma levels are affected by pregnancy, burns, certain drugs, and certain diseases, particularly HIV.[2]
The only established function of ORM is to act as a carrier of basic and neutrally charged lipophilic compounds. In medicine, it is known as the primary carrier of basic (positively charged) drugs (whereas albumin carries acidic (negatively charged) and neutral drugs), steroids, and protease inhibitors.[2][3] Aging causes a small decrease in plasma albumin levels; if anything, there is a small increase in alpha-1-acid glycoprotein. The effect of these changes on drug protein binding and drug delivery, however, appear to be minimal.[4] AGP shows a complex interaction with thyroid homeostasis: AGP in low concentrations was observed to stimulate the thyrotropin (TSH) receptor and intracellular accumulation of cyclic AMP. High AGP concentrations, however, inhibited TSH signalling.[5][6]
Alpha-1-acid glycoprotein has been identified as one of four potentially useful circulating biomarkers for estimating the five-year risk of all-cause mortality (the other three are albumin, very low-density lipoprotein particle size, and citrate).[7]
^Rooke GA (2009). "Anesthesia for the Older Patient". In Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC (eds.). Clinical Anesthesia. Lippincott Williams & Wilkins. p. 879. ISBN978-0-7817-8763-5.
^Zimmermann-Belsing T, Rasmussen AK, Feldt-Rasmussen U, Bøg-Hansen TC (February 2002). "The influence of alpha1-acid glycoprotein (orosomucoid) and its glycoforms on the function of human thyrocytes and CHO cells transfected with the human TSH receptor". Molecular and Cellular Endocrinology. 188 (1–2): 241–51. doi:10.1016/s0303-7207(01)00650-5. PMID11911961. S2CID22815279.
