miR-195 Regulates Metabolism in Failing Myocardium via Alterations in SIRT3 Expression and Mitochondrial Protein Acetylation
Background—Heart failure (HF) leads to mitochondrial dysfunction and metabolic abnormalities of the failing myocardium coupled with an energy-depleted state and cardiac remodeling. The mitochondrial deacetylase sirtuin 3 (SIRT3) plays a pivotal role in the maintenance of mitochondrial function through regulating the mitochondrial acetylome. Interestingly, unique cardiac and systemic miRNAs have been shown to play an important role in cardiac remodeling by modulating key signaling elements in the myocardium.
Methods—Cellular signaling was analyzed in human cardiomyocyte-like AC16 cells and acetylation levels in rodent models of SIRT3-/- and transgenic miR-195 overexpression were compared to WT. Luciferase assays, western blotting, immunoprecipitation assays and echocardiographic analysis were performed. Enzymatic activities of pyruvate dehydrogenase (PDH) and ATP synthase were measured.
Results—In failing human myocardium, we observed induction of miR-195 along with decreased expression of the mitochondrial deacetylase SIRT3 that was associated with increased global protein acetylation. We further investigated the role of miR-195 in SIRT3-mediated metabolic processes and its impact on regulating enzymes involved in deacetylation. Proteomic analysis of the total acetylome showed increased overall acetylation, as well as specific lysine acetylation of two central mitochondrial metabolic enzymes: PDH and ATP synthase. miR-195 downregulates SIRT3 expression through direct 3'UTR targeting. Treatments with either sirtuin inhibitor nicotinamide, siRNA-mediated SIRT3 knockdown or miR-195 overexpression enhanced acetylation of PDH complex and ATP synthase. This effect diminished PDH and ATP synthase activity and impaired mitochondrial respiration. Consistently, SIRT3-/- and miR-195 transgenic mice showed enhanced global protein acetylation, including PDH complex and ATP synthase, associated with decreased enzymatic activity.
Conclusions—Altogether, these data suggest that increased levels of miR-195 in failing myocardium regulate a novel pathway that involves direct SIRT3 suppression and enzymatic inhibition via increased acetylation of PDH and ATP synthase that are essential for cardiac energy metabolism.
- Received July 24, 2017.
- Revision received November 29, 2017.
- Accepted December 11, 2017.