Cardoso 2023 MiP2023

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MiPschool 2023

Cardoso 2023 MiP2023

Cardoso Luiza HD
Electron transfer from beta-oxidation and TCA cycle and impact of OXPHOS coupling on NADH and coenzyme Q redox states.

Link: MiP2023 Obergurgl AT

Cardoso Luiza HD (2023)

Event: MiP2023 Obergurgl AT

Authors: Cardoso Luiza HD, Donnelly Chris, Komlodi Timea, Doerrier Carolina, Gnaiger Erich

Introduction: Multiple mt-matrix dehydrogenases reduce NAD+ to NADH+H+, which is oxidized by CI (N-junction). Convergent electron flow through several mt-Complexes (CI, CII, CETF, etc) reduces electron transfer system (ETS)-reactive ubiquinone (UQ) to ubiquinol (UQH2), which is oxidized by CIII (Q-junction). The aim of our study was to analyze the relationships between the N- and Q-redox states and electron transfer rates.
Methods: Respiration and N- or Q-redox fractions were measured simultaneously with the Oroboros NextGen-O2k. Multiple protocols were used with sequential titrations of substrates, inhibitors, and uncouplers [1, 2]: N-pool with pyruvate&glutamate&malate, mouse liver mitochondria; Q-pool with succinate&rotenone, octanoylcarnitine&malate or palmitoylcarnitine&malate, permeabilized HEK 293T. After substrates, ADP, CCCP and antimycin A were titrated.
Results and discussion: Varying energy supply upstream of the Q-junction by using combinations of substrates and ETS-inhibitors in the noncoupled state, the Q-pool became reduced in direct proportion to respiration. In contrast, varying downstream energy demand in the absence of ADP (LEAK), by ADP activation (OXPHOS), and by uncoupler titrations (ET capacity), the N- and Q-pools were reduced in indirect proportion to respiration. The opposite correlations between redox state and respiratory rate were explained by the contrasting effects of varying electron push from different fuel substrates of the ETS or electron pull modulated by coupling and corresponding energy demand. Special emphasis on the interaction between fatty acid oxidation, CI, and CII – all involving separate electron entries into the Q-junction [3] – is particularly relevant in the context of obesity and bioenergetics studies.

  1. KomlΓ³di T, Cardoso LHD, Doerrier C, Moore AL, Rich PR, Gnaiger E (2021) Coupling and pathway control of coenzyme Q redox state and respiration in isolated mitochondria.
  2. Gnaiger E (2020) Mitochondrial pathways and respiratory control. An introduction to OXPHOS analysis. 5th ed.
  3. Gnaiger E (2023) Complex II ambiguities ― FADH2 in the electron transfer system.

β€’ Keywords: coenzyme Q, NADH, electron transfer system, OXPHOS, respirometry

β€’ O2k-Network Lab: AT Innsbruck Oroboros

Affiliations and contributions

Cardoso Luiza HD1, Donnelly C1,2, KomlΓ³di T1,3, Doerrier C1, Gnaiger E1
  1. Oroboros Instruments, AT
  2. Inst Sport Sciences, Univ Lausanne, CH
  3. Current address: Dept Medical Biochemistry, Semmelweis Univ, Budapest, HU
Corresponding author: [email protected]
Author contributions: The experiments were designed by LHDC, CDoerrier, and EG; performed by LHDC, CDonnelly, CDoerrier, and TK; analyzed by LHDC, CDoerrier, and CDonnely. The abstract was prepared by LHDC and EG.

Labels: MiParea: Respiration 

Coupling state: OXPHOS 

HRR: NextGen-O2k  Event: Oral 

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