Apolipoprotein D in Lipid Metabolism and Its Functional Implication in Atherosclerosis and Aging

Perdomo, German; Dong, H. Henry

There are two lines of evidences suggesting that apoD contributes to HDL remodeling. First, apoD is shown to modulate the activity of lecithin:cholesterol acyltransferase (LCAT), an HDL-bound enzyme that catalyzes the conversion of free cholesterol to cholesterol ester that is sequently recruited into the core of HDL. This effect along with apolipoprotein E (apoE) contributes to HDL core expansion and promotes HDL maturation [59] . Albers et al. report that apoD is a carrier of lysolecithin, a product of the LCAT reaction [60] . This finding is accordance with the observation that apoD interacts with LCAT [61] . However, whether apoD acts as an activator or inhibitor of LCAT activity still remains controversial. Studies by Kostner et al. [62] suggest that apoD is an activator of LCAT, which is at variance with the data of Albers et al. [63] , who show www.impactaging.com that apoD is an inhibitor of LCAT. Steyrer et al. [64] studied the activation of LCAT activity by apoD in comparison to apoA-I and apoC-I in reconstituted proteoliposomes. ApoA-I is the most potent activator of LCAT, followed by apoC-I and apoD. Their studies suggest that apoD modulates LCAT activity presumbly by stabilizing the enzyme on HDL [64] .