Serum amyloid A

Serum Amyloid A (SAA) is a family of apolipoproteins that are produced and secreted by the liver in response to systemic inflammation. It is a major acute-phase reactant and an important component of the body's immune response.

Function

The primary role of SAA is to transport cholesterol from the liver to the adrenal gland for the synthesis of corticosteroids. It also plays a role in the recruitment of immune cells to inflammatory sites, and the induction of enzymes that degrade extracellular matrix.

In addition to these functions, SAA has been implicated in several disease processes, including atherosclerosis, rheumatoid arthritis, and amyloidosis. In these conditions, the persistent overproduction of SAA leads to its deposition in various tissues, causing inflammation and damage.

Structure

SAA is a small protein of about 104 amino acids. It has a highly conserved sequence and is characterized by a four-helix bundle structure. The protein exists in several isoforms, which are produced by different genes and have slightly different functions.

Clinical significance

The level of SAA in the blood can increase up to 1000-fold during inflammation, making it a useful marker for disease activity in conditions such as rheumatoid arthritis and systemic lupus erythematosus.

In amyloidosis, the overproduction and deposition of SAA can lead to serious complications, including kidney failure, heart failure, and neuropathy.

Research

Research is ongoing to better understand the role of SAA in health and disease, and to develop new treatments for conditions associated with its overproduction.

See also

• Acute-phase protein
• Inflammation
• Amyloidosis
• Rheumatoid arthritis