Figure 3
Skeletal muscle fiber mitochondrial respiratory capacity in male TG/Nrf2-Ko mice. (A) Representative trace of oxygen (O2) concentration (blue line) and O2 flux (red line) during substrate-uncoupler-inhibitor-titration (SUIT) protocol for mitochondrial (mt) respiratory capacity in permeabilized mouse soleus muscle fibers, NADH-linked substrates (N-pathway, N), combined with succinate (NS-pathway, NS) and CI-inhibitor rotenone (S-pathway, S): Oxygen (elevation of O2 levels in respirometry chambers with permeabilized muscle fibers to avoid the development of an artificial hypoxic or anoxic core in the nonperfused fiber bundle), Fibers (1–2 mg saponin-permeabilized fibers), MP (Malate + Pyruvate; LEAK respiration), ADP (N-OXPHOS capacity), Cyt c (cytochrome c, integrity of outer mt-membrane), G (glutamate; N-OXPHOS capacity), S (succinate; NS-OXPHOS capacity), FCCP (NS-ETS capacity, ETSCI&CII), Rot (rotenone; S-ETS capacity, ETSCII), Ama (antimycin A; less than 2% residual oxygen consumption, ROX). (B) Mitochondrial respiratory capacity (JO2) of oxidative soleus skeletal muscle fibers of 40 wks old male animals (n = 4–5) and (C) corresponding flux control ratios and O2 fluxes normalized to ETSCI&CII. (D) NetOXPHOS control ratio (≈(P − L)/E, expresses the OXPHOS capacity (corrected for LEAK respiration) as a fraction of ETS capacity). (D) Representative immunoblots of respiratory chain complexes in soleus muscle of 40 wks old male animals using Mitofusin2 (MFN2) as loading control (2 samples shown out of 4–5 analyzed per group). All absolute values are expressed as box-and-whisker plots, relative or normalized data are expressed as means + SEM; *p < 0.05; **p < 0.01; ***p < 0.001.
