Evaluation of apolipoprotein E secretion by macrophages in type 2 diabetic patients: role of HDL and apolipoprotein A-I.

It has been shown that apolipoprotein A-I (ApoA-I) stimulates the secretion of apolipoprotein E (ApoE) from human macrophages. ApoA-I is a major protein constituent of HDL which because of its role in reverse cholesterol transport, has been implicated in the prevention of atherosclerosis. We herein investigated the ability of monocyte-derived macrophages (MDMs) in 42 patients with type 2 diabetes to secrete ApoE; these patients commonly have low plasma HDL and ApoA-I levels. Our data showed that ApoE secretion from these cells was reduced in patients with low plasma HDL and ApoA-I levels; there were positive correlation between ApoE secretion from MDMs and plasma HDL (r2=0.33, p=0.03) and ApoA-I (r2=0.31, p=0.03). Furthermore, we found that ApoE secretion increased concomitantly with an increase in HDL or ApoA-I in treated diabetics (n=24) from 1.99+/-1.86 to 3.40+/-1.77 ng/mg cell protein. These findings suggest another possible link between HDL and ApoA-I metabolism and atherosclerosis in patients with type 2 diabetes.