Glucose Metabolism Regulates Mitochondrial Supercomplex Abundance in Murine Heart

Abstract

BackgroundMitochondrial electron transport chain (ETC) complexes assemble to form supercomplexes, which are thought to optimize ATP production via electron channelling. Supercomplexes appear to be more abundant in organs with a large energy demand, such as the heart. Nevertheless, the mechanisms that regulate supercomplex abundance in the heart remain unclear.ObjectiveThe purpose of this study was to determine how glycolytic activity regulates the abundance and activity of mitochondrial supercomplexes in the adult mouse heart.MethodsMitochondria isolated from adult, male FVB/NJ mouse hearts were solubilized with 2% digitonin. Mitochondrial supercomplexes (>1 MDa) were then resolved by electrophoresis on 3–12% blue native‐polyacrylamide (BN‐PAGE) gradient gels, and the protein constituents of each supercomplex were identified by mass spectrometry and Western blotting. To determine how glycolysis affects mitochondrial supercomplex abundance in the heart, we assessed mitochondrial supercomplexes in cardiac mitochondria isolated from mice that express cardiac‐specific, dominant‐negative (GlycoLo) or dominant‐positive (GlycoHi) forms of 6‐phosphofructo‐2‐kinase/fructose‐2,6‐bisphosphatase, which constitutively lower or augment glycolytic rate, respectively. The enzymatic activities of supercomplex components were assessed using in‐gel activity assays. Differences in supercomplex abundances and activities were calculated using one‐way ANOVA, followed by Tukey post‐hoc tests.ResultsCardiac mitochondria contained at least six distinct supercomplexes, with each supercomplex comprising NADH dehydrogenase, cytochrome bc1 complex, cytochrome c oxidase, and ATP synthase. In Coomassie‐stained BN‐PAGE gels and in Western blots, mitochondria from GlycoLo hearts showed higher supercomplex abundance than mitochondria from WT and GlycoHi mice. Furthermore, we found that mitochondria from GlycoLo hearts had a higher abundance of NADH dehydrogenase and cytochrome bc1 complex. Furthermore, the enzymatic activities of supercomplex‐associated NADH dehydrogenase and cytochrome c oxidase were higher in GlycoLo hearts than in GlycoHi and WT hearts.ConclusionLow glycolytic activity in the heart increases mitochondrial supercomplex abundance and activity. These findings could provide new insights into the metabolic mechanisms that regulate cardiac health and remodeling.Support or Funding InformationNIH (HL122580, HL130174, ES028268, HL78825, and GM103492) and from the American Diabetes Association (1‐16‐JDF‐041)This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.