ApoAI is a major protein component in high-density lipoproteins -HDL). It acts as an acceptor for sequential transfers of phospholipids and free cholesterol from peripheral tissues and transports cholesterol to the liver and other tissues for excretion and steroidogenesis. Serum ApoAI levels are inversely related to the risk of developing atherosclerosis. Loss-of-function mutations in ApoAI are causes of diseases such as HDL deficiency type 1 -or Tangier disease) and type 2 -familial hypoalphalipoproteinemia), and systemic non-neuropathic amyloidosis. Liver and small intestine are two main sources of the protein.