ORM1

ORM1 was first discovered over a century ago and has since been the subject of extensive research due to its diverse biological functions . It is synthesized mainly by hepatocytes, but extrahepatic tissues can also produce ORM1 under various physiological and pathological conditions .

ORM1 is characterized by its low isoelectric point (pI) of 2.8–3.8 and high carbohydrate content, which constitutes about 45% of its structure . The normal plasma concentration of ORM1 in humans ranges from 0.6 to 1.2 mg/mL, accounting for 1–3% of plasma proteins . Its levels can be significantly altered by factors such as pregnancy, burns, certain drugs, and diseases like HIV .

ORM1 plays a crucial role in the body’s acute-phase response to inflammation and injury. It is involved in modulating the immune system, binding and transporting various drugs, and regulating angiogenesis . ORM1 can both inhibit and stimulate angiogenesis depending on the context, demonstrating its bimodal regulatory properties .

The expression of the ORM1 gene is regulated by several mediators, including glucocorticoids, interleukin (IL)-1, TNF-α, and IL-6 . ORM1 is encoded by two polymorphic genes, which contribute to its structural diversity . Research has identified specific receptors for ORM1 in macrophages, neutrophils, and liver parenchymal cells, highlighting its role in immune modulation .

Due to its involvement in various physiological processes, ORM1 is a valuable biomarker for several conditions, including liver diseases, cancer, and HIV . Its ability to bind and transport drugs also makes it a critical factor in pharmacokinetics and drug delivery systems .