Nox4 reprograms cardiac substrate metabolism via protein O-GlcNAcylation to enhance stress adaptation
Adam A. Nabeebaccus, … , Manuel Mayr, Ajay M. Shah
Adam A. Nabeebaccus, … , Manuel Mayr, Ajay M. Shah
Published December 21, 2017
Citation Information: JCI Insight. 2017;2(24):e96184. https://doi.org/10.1172/jci.insight.96184.
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Research Article Cardiology Metabolism

Nox4 reprograms cardiac substrate metabolism via protein O-GlcNAcylation to enhance stress adaptation

Abstract

Cardiac hypertrophic remodeling during chronic hemodynamic stress is associated with a switch in preferred energy substrate from fatty acids to glucose, usually considered to be energetically favorable. The mechanistic interrelationship between altered energy metabolism, remodeling, and function remains unclear. The ROS-generating NADPH oxidase-4 (Nox4) is upregulated in the overloaded heart, where it ameliorates adverse remodeling. Here, we show that Nox4 redirects glucose metabolism away from oxidation but increases fatty acid oxidation, thereby maintaining cardiac energetics during acute or chronic stresses. The changes in glucose and fatty acid metabolism are interlinked via a Nox4-ATF4–dependent increase in the hexosamine biosynthetic pathway, which mediates the attachment of O-linked N-acetylglucosamine (O-GlcNAcylation) to the fatty acid transporter CD36 and enhances fatty acid utilization. These data uncover a potentially novel redox pathway that regulates protein O-GlcNAcylation and reprograms cardiac substrate metabolism to favorably modify adaptation to chronic stress. Our results also suggest that increased fatty acid oxidation in the chronically stressed heart may be beneficial.

Authors

Adam A. Nabeebaccus, Anna Zoccarato, Anne D. Hafstad, Celio X.C. Santos, Ellen Aasum, Alison C. Brewer, Min Zhang, Matteo Beretta, Xiaoke Yin, James A. West, Katrin Schröder, Julian L. Griffin, Thomas R. Eykyn, E. Dale Abel, Manuel Mayr, Ajay M. Shah

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Figure 5

Nox4 modulates fatty acid oxidation via protein O-GlcNAcylation.

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Nox4 modulates fatty acid oxidation via protein O-GlcNAcylation. (A) Nox...
(A) Nox4 overexpression increased protein O-GlcNAcylation in cultured cardiomyocytes. Tubulin was used as a loading control. (B) Inhibition of protein O-GlcNAcylation with an HBP inhibitor (Ac-5SGlcNAc, 50 μM) reversed the effect of Nox4 overexpression on oxygen consumption rate (OCR) for palmitate in cardiomyocytes. *P < 0.05, 2-tailed t test, n = 9. (C) In cardiomyocytes in which Nox4 was knocked down, supplementation with GlcNAc (40mM) partially increased the OCR for palmitate. *P < 0.05, 2-tailed t test, n = 12. (D) IP of CD36 in protein lysates (membrane fractions) from cardiomyocytes overexpressing Nox4 or β-Gal control was followed by IB for CD36 and for O-GlcNAcylation (O-GlcNAc). A representative immunoblot is shown to the left. To the right are mean data from 4 independent experiments. **P < 0.01, ***P < 0.001, 2-tailed t test. (E) IP of CD36 followed by IB for CD36 and O-GlcNAc in cardiomyocytes with siRNA-mediated knockdown of Nox4, with and without supplementation of GlcNAc (100 μM), or in cells treated with a control siRNA. A representative immunoblot is shown to the left. To the right are mean data from 4 independent experiments. *P < 0.05, ***P < 0.001, 1-way ANOVA using Tukey’s multiple comparison test. (F) IP of CD36 followed by IB for CD36 and O-GlcNAc in membrane fractions from WT and Nox4 TG hearts. A representative immunoblot is shown to the left. To the right are mean data from 4 independent experiments. **P < 0.01, ****P < 0.0001, 2-tailed t test. See also Supplemental Figure 4.