APOC2 activates the lipoprotein lipase in capillaries, which hydrolyzes triglycerides and thus provides free fatty acids for cells. APOC2 is component of the very low density lipoprotein (VLDL) fraction in plasma. It is also an activator of several triacylglycerol lipases. The association of APOC2 with plasma chylomicrons, VLDL, and HDL is reversible, a function of the secretion and catabolism of triglyceride-rich lipoproteins, and changes rapidly. Defects in APOC2 are the cause of hyperlipoproteinemia type 1B (HLPP1B) which characterized by hypertriglyceridemia, xanthomas, and increased risk of pancreatitis and early atherosclerosis.