Abstract 78: Inhibition of Mir-33 Overcomes the Deleterious Effects of Diabetes on Atherosclerosis Regression.

Objective Diabetes increases the risk of cardiovascular morbidity and mortality which remains elevated with conventional therapies, such as statins. We have shown that diabetes also impairs plaque regression following LDL reduction in mice, as evidenced by a higher macrophage (CD68+ cells) plaque content and a higher inflammatory state of these cells compared to non-diabetic mice. Type-2 diabetics have dyslipidemia characterized by elevated triglyceride levels and low HDL, the latter is thought to contribute to their risk, based on epidemiologic studies. In non-diabetic atherosclerotic mice, inhibition of miR-33, an intronic micro-RNA located within the SREBF2 gene, increases the plasma level of apoAI and HDL-cholesterol (HDL-C) and promotes plaque regression. We hypothesize that elevation of HDL through the inhibition of miR-33 will overcome the deleterious effect of diabetes on macrophage content and inflammatory phenotype in plaques in a regression evironment. Methods and Results Diabetic (STZ-injected) and non-diabetic Reversa (LdLr-/-Apob100/100Mttpfl/flMx1-Cre+/+) mice, a model in which diet-induced hypercholesterolemia can be quickly and efficiently reversed, were fed a western diet for 16 weeks and then treated with anti-miR-33 oligonucleotide or control anti-miR for 4 weeks. Treatment with anti-miR-33 increased HDL-cholesterol in both diabetic (17%) and non-diabetic mice (30%). Anti-miR-33 treated diabetic mice showed an improvement in plaque regression as evidenced by a 26% reduction in CD68 content compared to diabetic mice receiving control anti-miR, and an enrichment in anti-inflammatory M2 macrophages (assessed by MR 1 and YM1). Monocyte tracking with latex beads suggests that the reduction of macrophage content is due to a decrease in monocyte recruitment to the plaque, rather than an increase in macrophage egress. This reduction in recruitment correlated with a decrease in the monocytosis associated with diabetes in the anti-miR-33 treated diabetic mice. Conclusion These findings suggest that miR-33 inhibition is able to overcome the deleterious effects of diabetes on atherosclerosis regression, by decreasing monocytosis, monocyte recruitment and improving the inflammatory status of plaque macrophages.