Microbiota Mediate Enhanced Exercise Capacity Induced by Exercise Training

Abstract

Purpose: We investigated the effects of gut microbes, and the mechanisms mediating the enhanced exercise performance induced by exercise training, i.e., skeletal muscle blood flow, and mitochondrial biogenesis and oxidative function in male mice.

Methods: All mice received a graded exercise test before (PRE) and after exercise training via forced treadmill running at 60% to 70% of maximal running capacity 5 d·wk -1 for 5 wk (POST). To examine the role of the gut microbes, the graded exercise was repeated after 7 d of access to antibiotic (ABX)-treated water, used to eliminate gut microbes. Peripheral blood flow, mitochondrial oxidative capacity, and markers of mitochondrial biogenesis were collected at each time point.

Results: Exercise training led to increases of 60% ± 13% in maximal running distance and 63% ± 11% work to exhaustion ( P < 0.001). These increases were abolished after ABX ( P < 0.001). Exercise training increased hindlimb blood flow and markers of mitochondrial biogenesis and oxidative function, including AMP-activated protein kinase, sirtuin-1, PGC-1α citrate synthase, complex IV, and nitric oxide, all of which were also abolished by ABX treatment.

Conclusions: Our results support the concept that gut microbiota mediate enhanced exercise capacity after exercise training and the mechanisms responsible, i.e., hindlimb blood flow, mitochondrial biogenesis, and metabolic profile. Finally, results of this study emphasize the need to fully examine the impact of prescribing ABX to athletes during their training regimens and how this may affect their performance.

FIGURE 1 –

Study design. Sedentary (PRE) C57BL/6J male mice were exercise trained for 60 min/d, 5d/wk for 5-weeks via forced treadmill running set at a constant 10° incline (POST). Graded exercise tests (GXTs) were performed on the same treadmill PRE, POST and after one-week of ad libitum access to antibiotic treated water (ABX). Mitochondrial biogenesis, oxidative phosphorylation and blood flow were evaluated at each time point.

FIGURE 2 –

(A) ABX treatment significantly decreased body weight compared to –POST (p<0.001). (B) Exercise training did not alter, where ABX treatment significantly increased cecal weight compared to –PRE (p<0.001) and –POST (p<0.0001). ABX significantly decreased liver (2C, p<0.0001) and skeletal muscle (quadriceps, 2D, p<0.0001) weight compared to POST. Significantly reduced skeletal muscle weight was persistent even after correcting for cecal weight (2E, p<0.05)

FIGURE 3 –

5 weeks of exercise training (POST) significantly increased maximal running distance and work to exhaustion in mice. Ad libitum access to ABX was used to eliminate the gut microbiota resulting in abolition of the increases in maximal running distance (A) and work to exhaustion (B) induced by exercise training. Values represent mean ± SEM. A one-way ANOVA with a Tukey post hoc test was used to show significance at *** p<0.001 and **** p<0.0001.

FIGURE 4 –

Exercise training significantly increased hindlimb blood flow (gastrocnemius) in mice and ABX abolished these increases (A). Representative figures showing levels of blood flow measured ultrasonically in the mice hindlimb (B). A one-way ANOVA with a Tukey post hoc test was used to show significance at * p<0.05, ** p<0.01.

FIGURE 5 –

Markers of mitochondrial biogenesis (A) SIRT1, (B) AMPK, and (C) PGC-1α were increased (p<0.05) in mice following 5-weeks of exercise training. These increases were abolished following ABX administration. Values represent mean ± SEM. A one-way ANOVA with a Tukey post hoc was used to show significance at * p<0.05, *** p<0.001 and **** p<0.0001.

FIGURE 6 –

Exercise training improved mitochondrial function and skeletal muscle nitric oxide activity. Markers of mitochondrial function (A) citrate synthase and (B) Complex IV activity were both increased in mice following exercise training. This effect was abolished following ABX administration. (C) Skeletal muscle nitric oxide activity increased following exercise training (p<0.05) and was also abolished following ABX. Values represent mean ± SEM. A one-way ANOVA with a Tukey post hoc was used to show significance at * p<0.05, *** p<0.001, **** p<0.0001.

FIGURE 7 –

Mechanisms Mediating Enhanced Exercise Capacity Induced by Exercise Training. Exercise capacity is increased due to increased hindlimb blood flow mediated by increases nitric oxide and increased mitochondrial oxidative phosphorylation (citrate synthase, complex IV) providing the stimulus to increased mitochondrial biogenesis (AMPK, SIRT1, and PGC-1α). ABX in drinking water abolished the increases in the markers of mitochondrial oxidative function (citrate synthase, complex IV, and nitric oxide) and the increases in mitochondrial biogenesis (AMPK, SIRT1, and PCG-1α). Thus, the elimination of the gut microbiota, using ABX, eliminated the increased running distance and work to exhaustion induced by exercise training and the mechanisms mediating the improved exercise capacity induced by exercise training.