Abstract 18676: Anti-miR33 Therapy Induces PGC1a Expression to Regulate Immunometabolic Pathways in Atherosclerosis and Obesity
Atherosclerosis and obesity are epidemic causes of morbidity and mortality, and immunometabolic mechanisms are at the intersection of both diseases. Recently, microRNA 33 (miR33) was identified as a novel and critical regulator of lipid metabolism and a therapeutic target for reducing atherosclerosis. However, the exact mechanism(s) by which anti-miR33 exerts these beneficial effects are unclear. Comprehensive microarray profiling of mRNA from atherosclerotic plaque macrophages of anti-miR33 treated mice identified PPARγ coactivator 1α (PGC1α) as a novel miR33 target gene that is markedly de-repressed. PGC1α is a key regulator of mitochondrial function and energy metabolism, and promoting its activity improves metabolic syndrome (e.g. insulin resistance, obesity, inflammation). Here, we determine if anti-miR33 therapy upregulates PGC1α and affects energy metabolism in atherosclerosis.
Results: miR33 overexpression reduced the 3’UTR activity of PGC1α by 40% (p≤0.05), confirming it was a direct and specific target of miR33. Transfection of macrophages with either miR33 mimics or anti-miR33 in vitro resulted in a decrease or increase of Pgc1α mRNA and protein respectively. Using the Seahorse XF Flux Analyzer, we showed that anti-miR33 treatment boosted maximal mitochondrial oxygen consumption rate, confirming that anti-miR33 impacts positively on mitochondrial respiration. Anti-miR33 treated macrophages also increased the expression of known functional mitochondrial genes (e.g. Slc25a25, Nrf1, Bid and Mtch2), implying miR33 controls several genes in the mitochondrial metabolic pathway. Inhibition of miR33 in vivo in Ldlr-/- mice upregulated Pgc1α mRNA expression in adipose tissue, liver and macrophages. Adipose tissue from anti-miR33 treated obese mice also showed upregulation of so-called “browning” genes (e.g. Ucp-1, Elovl3) that contribute to increased energy utilization of white adipose tissue, possibly improving whole-body metabolism.
Conclusion: Anti-miR33 therapy specifically targets PGC1α in macrophages and adipose tissue and improves mitochondrial function, all of which can positively regulate inflammatory and energy utilization processes in cardiometabolic diseases (eg. atherosclerosis and obesity).
- © 2013 by American Heart Association, Inc.