Progress on haptoglobin and metabolic diseases.

Haptoglobin (Hp) is an acidic glycoprotein, existing in the serum and other body fluids of human beings and a variety of mammals. Hp is produced in the liver, white adipose tissue, and the kidney. The genetic polymorphisms and different phenotypes of Hp have different biological functions. Hp has antibacterial, antioxidant, and angiogenic effects and is associated with multiple diseases including simple obesity, vascular complications of diabetes mellitus, nonalcoholic fatty liver disease, hypertension, blood diseases, autoimmune diseases, and malignant tumors. Hp also participates in many life activities, indicating the importance of Hp in further studies. Previously, we found that the expression of serum Hp changed after treatment of simple obesity patients in clinical trials. However, the specific mechanism of Hp in patients with simple obesity is still unclear. The purpose of this article is to introduce recent research progress on Hp, emphasizing the relationship between Hp and the development of metabolic disease, which will improve the understanding of the functions of Hp underlying metabolic diseases and discuss future research directions.