Menstrual cycle influence on skeletal muscle mitochondrial respiration in humans

Abstract

The menstrual cycle influences function in various tissues in the body. We sought to determine if menstrual cycle phase could influence mitochondrial function in skeletal muscle in females. Twenty-nine females with regular menstrual cycles were randomized to have a vastus lateralis muscle biopsy during either the early follicular or luteal phase. High-resolution respirometry was used to determine mitochondrial respiration on permeabilized muscle fibers. Glutamate/malate LEAK respiration was significantly higher during the luteal phase compared to the early follicular phase. Glutamate/malate/succinate LEAK respiration was the same during both menstrual cycle phases, as was maximal coupled and uncoupled respiration. There were no differences in fatty acid-supported respiration. The fatty acid-supported coupling efficiency ratios of 1-OcM (octanoylcarnitine/malate) LEAK over maximal coupled respiration and 1-OcM LEAK over maximal uncoupled respiration were both significantly higher in mitochondria from the early follicular phase than in the luteal phase. Mitochondrial H₂O₂ emission (glutamate/malate/succinate supported) was significantly increased in muscle from the early follicular phase. We detected no differences in mitochondrial content using citrate synthase activity between phases of the menstrual cycle. Collectively, our observations demonstrate a limited influence of the menstrual cycle on certain measures of submaximal respiration, coupling efficiencies, and H₂O₂ emission.

Keywords: menstrual cycle phase; mitochondrial respiration; skeletal muscle.

FIGURE 1

Mitochondrial respiration using NADH‐linked substrates and succinate. G, glutamate; M, malate; S, succinate; _P, ADP; _E, FCCP; E. Follicular, early follicular. Bars represent mean ± standard deviation, dots represent individual data points; early follicular n = 10, luteal n = 15 (GMS and GMS_E), luteal n = 16 (GM and GMS_P). Means were tested using unpaired t‐tests. Values above bars indicate p value when significantly different (p < 0.05).

FIGURE 2

Mitochondrial coupling efficiency ratios for respiration using NADH‐linked substrates and succinate. G, glutamate; M, malate; S, succinate; _P, ADP; _E, FCCP; E. Follicular, early follicular. Bars represent mean ± standard deviation; dots represent individual data points: early follicular n = 10; luteal n = 14 (1‐GMS·GMS_E ⁻¹), luteal n = 15 (1‐GM·GMS_E ⁻¹, 1‐GMS·GMS_P ⁻¹, and 1‐GMS_P·GMS_E ⁻¹), and luteal n = 16 (1‐GM·GMS_P ⁻¹). Means were tested using unpaired t‐tests except for 1‐GM·GMS_E ⁻¹, 1‐GM·GMS_P ⁻¹, and 1‐GMS·GMS_E ⁻¹, which were tested with Mann–Whitney U tests.

FIGURE 3

Mitochondrial respiration using fatty acid oxidation with NADH‐linked substrates and succinate. Oc, octanoylcarnitine; M, malate; S, succinate; _P, ADP; _E, FCCP; E. Follicular, early follicular. Bars represent mean ± standard deviation; dots represent individual data points: early follicular n = 9 (OcMS_P and OcMS_E), early follicular n = 10 (OcM and OcM_P), luteal n = 15(OcM_P, OcMS_P, and OcMS_E), and luteal n = 16(OcM). Means were tested using unpaired t‐tests. Values above bars indicate p value.

FIGURE 4

Mitochondrial coupling efficiency ratios for respiration using fatty acid oxidation, NADH‐linked substrates, and succinate. Oc, octanoylcarnitine; M, malate; S, succinate; _P, ADP; _E, FCCP; E. Follicular, early follicular. Bars represent mean ± standard deviation; dots represent individual data points; early follicular n = 9, luteal n = 15. Means were tested using unpaired t‐tests. Values above bars indicate p value when significantly different (p < 0.05).

FIGURE 5

Mitochondrial H₂O₂ production. (a) absolute JH₂O₂. (b) JH₂O₂·JO₂ ⁻¹. G, glutamate; M, malate; S, succinate; _P, ADP; E. Follicular, early follicular. Bars represent mean ± standard deviation; dots represent individual data points; early follicular n = 10, luteal n = 16 for all comparisons except GMS JH₂O₂·JO₂ ⁻¹ luteal n = 15. Means for absolute H₂O₂, GM JH₂O₂·JO₂‐1, and GMS_P JH₂O₂·JO₂‐1 were tested using unpaired t‐tests; means for GMS JH₂O₂·JO₂ ⁻¹ were tested with a Mann–Whitney U test. Values above bars indicate p value when significantly different (p < 0.05).

FIGURE 6

(a) Citrate synthase activity. E. Follicular, early follicular. Bars represent mean ± standard deviation, dots represent individual data points; early follicular n = 12, luteal n = 17. Means were tested using an unpaired t‐test. (b) Correlation between maximal uncoupled respiration supported by NADH‐linked substrates and succinate (GMS_E) and citrate synthase activity. E. Follicular: r = −0.17, 95% CI [−0.72, 0.52], p = 0.6547, n = 10 pairs; Luteal: r = 0.29, 95% CI [−0.26, 0.7], p = 0.2998, n = 15 pairs. (c) Correlation between maximal uncoupled respiration supported by fatty acid oxidation with NADH‐linked substrates and succinate (OcMS_E) and citrate synthase activity. E. Follicular: r = 0.42, 95% CI [−0.34, 0.85], p = 0.2643, n = 9 pairs; Luteal: r = −0.17, 95% CI [−0.63, 0.38], p = 0.5497, n = 15 pairs. Trend lines represent best fits; correlations were tested using the Pearson product–moment correlation test.