Superior Intrinsic Mitochondrial Respiration in Women Than in Men

Figures

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  FIGURE 1. Mean ± SD of mitochondrial respiration rates normalized by protein levels of mitochondrial suspension (pmol s-1 μg protein-1; intrinsic mitochondrial oxidative respiration) and by the initial muscle wet weight (pmol s-1 mg-1; mass-specific mitochondrial respiration) in women, men, and trained men groups for: A,F, leak respiration is the respiratory rate in the presence of substrates without addition of adenylates; B,G, state 4 is the respiratory rate when ADP is phosphorylated maximally to ATP; C,H, complex IP is the maximum ADP stimulated respiration rate in the presence of complex I substrates; D,I, complex I+IIP is similar to C,H but with added convergent electron flux through complex II by adding succinate (CI+IIP); E, maximal oxidative phosphorylation capacity (OXPHOS) control ratio (CI+IIP/Leak) indicates the limitation of OXPHOS by the phosphorylation system; J, CI+IIP/CIP indicates the contribution of CII respiration to maximal respiration. ∗p < 0.05 between groups.

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  FIGURE 2. (A) Individual and mean ± SD values of ex vivo mitochondrial p50 (p50mito; kPa) at maximal ADP-induced activation measured in isolated mitochondria when activating complex I (CIP) for women, men, and trained men groups. (B) Individual and mean ± SD values of ex vivo p50mito as shown in A, but with complex I+II-linked substrate state (CI+IIP) for women, men, and trained men groups. ∗p < 0.05 between groups. (C) Hyperbolic curves showing the relation between PO2 (kPa) and mitochondrial O2 flux [pmol s-1 mL-1]. Curves were obtained inserting into the following equation [VO2 = (CI+IIP PO2)⋅(PO2 + p50mito)-1] continuous PO2 values, the ex vivo p50mito (graphically indicated with a dot) and CI+IIP (graphically indicated with a dashed lines) mean values measured in this study in women, men, and trained men groups. This figure shows the role of mitochondrial p50 for muscle oxygen consumption since for a given intracellular PO2, a lower p50mito would result in a higher tissue O2 consumption [VO2 = CI+IIP⋅PO2 (PO2 + p50mito)-1] and vice versa. The superior intrinsic mitochondrial respiration in women compared to men with similar VO2max shown in this study may be an important physiological…

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  FIGURE 3. Mean ± SD values of maximal cycling power output (Wmax; W kg-1) achieved on a gradual incremental exercise test for women, men, and trained men groups. ∗p < 0.05 between groups.

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  FIGURE 4. Correlation between the maximal mitochondrial oxidative phosphorylation (State 3 complex I+IIP), maximal cycling power output (Wmax) achieved on a gradual incremental exercise test and maximal oxygen consumption (VO2max) for the whole group of subjects. Maximal mitochondrial oxidative phosphorylation was normalized for mitochondrial protein content (intrinsic mitochondrial respiration; A,B) and for initial wet weight (mass-specific mitochondrial respiration; C,D).