Rationale Diabetes increases cardiovascular disease risk in humans and remains elevated despite cholesterol-lowering therapy with statins. Consistent with this, in mouse models diabetes impairs atherosclerosis plaque regression after aggressive cholesterol-lowering. miR33 is a key negative regulator of the reverse cholesterol transport factors, ABCA1 and HDL, which suggested that its inhibition may overcome this impairment. Objective To assess the effects of miR33 inhibition on atherosclerosis regression in diabetic mice. Methods and Results Reversa mice, which are deficient in the LDL receptor and in which hypercholesterolemia is reversed by conditional inactivation of the microsomal triglyceride transfer protein (Mttp) gene, were placed on an atherogenic diet for 16 weeks, then either made diabetic by STZ injection or kept normoglycemic. Lipid-lowering was induced by Mttp inactivation and mice were treated with anti-miR33 or control oligonucleotides. Whereas regression was impaired in diabetic mice treated with control oligonucleotides, anti-miR33 treatment decreased plaque macrophage content and inflammatory gene expression in these mice. The decreased macrophage content in anti-miR33-treated diabetic mice was associated with a blunting of hyperglycemia-induced monocytosis and reduced monocyte recruitment to the plaque, which was traced to an inhibition of the proliferation of bone marrow monocyte precursors associated with the upregulation of their Abca1. Conclusions miR33 inhibition overcomes deleterious effects of diabetes in atherosclerosis regression in mice, which suggests a therapeutic strategy in diabetic patients, who remain at elevated cardiovascular disease risk despite plasma cholesterol lowering.

Niacin therapy, used either alone or in combination with another agent to reduced the risk of coronary heart disease, is effective in raising and lowering, respectively, HDL‐c and apoB/VLDL triglyceride (TG) levels in dyslipidemia. To further understand if part of the mechanism is by reducing the secretion of apoB‐containing lipoproteins through autophagy, we did a series of niacin studies in isolated primary hepatocytes or in intact mice. Metabolic labeling and pulse‐chase results showed niacin increased intracellular apoB degradation by 30%, and decreased apoB/VLDL TG secretions by 40%. These effects were lost in autophagy‐deficient cells. Mice fed with diet containing 3% niacin had 40% increases in plasma HDL‐c. Feeding high fat diet (HFD) with niacin lowered LDL‐c by 50%. Niacin was able to suppress postprandial plasma triglyceride by 30%. Niacin reduced hepatic triglyceride and cholesterol concentrations by 40% and 50%, respectively, in mice fed with HFD. These data suggest niacin decreases hepatic lipid concentrations, apoB/VLDL secretion, and modifies plasma cholesterol levels. Some of the effects required niacin metabolism and autophagy degradation. Supported by grants from the NIH (HL58541) and Merck & Co., Inc.Grant Funding Source: NIH (HL58541) and Merck & Co., Inc.

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.