Apolipoproteins are a family of fatty-acid binding proteins that transport fat through the bloodstream in the form of lipoproteins. ApoF (apolipoprotein F), also known as LTIP (lipid transfer inhibitor protein), is a 308 amino acid secreted protein that belongs to the apolipoprotein family. Expressed in liver tissues and also existing in plasma, ApoF inhibits the activity of CETP (cholesteryl ester transfer protein) and, via this inhibition, functions to regulate cholesterol transport.