Oral antibiotics reduce voluntary exercise behavior in athletic mice

Abstract

The gut microbiome can affect various aspects of both behavior and physiology, including exercise ability, but effects on voluntary exercise have rarely been studied. We studied females from a selection experiment in which 4 replicate High Runner (HR) lines of mice are bred for voluntary exercise and compared with 4 non-selected control (C) lines. HR and C mice differ in several traits that likely interact with the gut microbiome, including higher daily running distance, body temperatures when running, spontaneous physical activity when housed without wheels, and food consumption. After two weeks of wheel access to reach a stable plateau in daily running, mice were administered broad-spectrum antibiotics for 10 days. Antibiotic treatment caused a significant reduction in daily wheel-running distance in the HR mice (-21%) but not in the C mice. Antibiotics did not affect body mass or food consumption in either HR or C mice, and we did not observe sickness behavior. Wheel running by HR mice did not recover during the 12 days following cessation of antibiotics. The decreased wheel-running in HR but not C mice, with no apparent negative side effects of antibiotics, suggests that the HR microbiome is an important component of their high-running phenotype.

Keywords: Antibiotics; Behavior; Exercise; Gut microbiota; Host-microbe interaction; Wheel running.

Figure 1.

Experimental Timeline.

Figure 2.

Average daily wheel running (revolutions per 23 hours) across the course of the experiment. Values were calculated by taking the simple means of the 4 HR lines and the 4 C lines for each individual day, and then averaging those values to obtain the average for the HR and C lines. Data were truncated on days 8, 14, and 25 (~20 hours) when the water bottles were being changed. Brackets indicate days that were used in statistical analyses. See Supplemental Figure 2 for wheel running mean revolutions per day for each of the 4 HR and 4 C lines. A. N=99 mice, through day 24 of the experiment. Days 11–13 before antibiotics were compared with days 22–24 during antibiotics. B. N=76 mice, excluding a random subset that were removed on day 28 for a separate experiment. The microbiome was allowed to naturally recover after antibiotic treatment (days 25–36). Days 34–36 were used to indicate wheel running in recovery.

Figure 3.

Wheel running before (averages for days 11–13) and during (averages for days 22–24) antibiotics (ABX; see Figure 2). Data are presented as least squares means ± standard errors and type 3 tests of fixed effects from repeated-measures analyses using values for individual days in SAS Procedure Mixed. N=92 mice and 543 observations after removal of statistical outliers (see Methods). Pearson’s r is a measure of effect size (see Methods). A. Revolutions per day. Antibiotic treatment reduced the revolutions per day (days 22–24) in only the HR mice (linetype × antibiotic treatment interaction, p=0.0075; differences of least squares means p=0.0023 for HR mice and p=0.2071 for C mice). B. Number of 1-minute intervals with at least one revolution. Antibiotic treatment reduced the number of minutes mice run per day for both linetypes (p=0.0002; differences of least squares means p=0.0018 for HR mice and p=0.0012 for C mice). C. Revolutions per minute. Antibiotics had no statistical effect on average speed. D. Maximum revolutions per minute. Antibiotics had no statistical effect on maximum running speed.

Figure 4.

Wheel running before antibiotics (averages for days 11–13), during antibiotics (averages for days 22–24), and after recovery (days 34–36) (see Figure 2). Data are presented as least squares means ± standard error from repeated-measures analyses using values for individual days in SAS Procedure Mixed. N=73 mice and 639 observations after removal of statistical outliers (see Methods). Pearson’s r is a measure of effect size (see Methods). A. Revolution per day. B. Number of 1-minute intervals with at least one revolution. C. Revolutions per minute. D. Maximum revolutions per minute. Overall, mice did not recover to pre-treatment levels of running (see Figures 2 and 3) within the time frame of this experiment.

Figure 5.

Body mass measured at various timepoints. Analyses were first done separately for each time point (not repeated-measures) and values in the figure are least squares means ± standard errors from those analyses. p-values above each pair of bars are for the linetype comparison at each time point. In addition, separate repeated-measures analysis of mass before versus after 10 days of antibiotics indicated mice were larger after antibiotic treatment (treatment p=0.0031, linetype p=0.4646, interaction p=0.8329). A similar analysis of mass after antibiotics versus after 12 days of recovery indicated no effect of recovery (treatment p=0.9321, linetype p=0.4780, interaction p=0.6612).

Figure 6.

Average daily food consumption during the baseline period (days 8–14) compared to during the antibiotic (ABX) treatment period (days 15–24), with body mass as a covariate. Data are presented as least squares mean ± standard errors from repeated-measures analyses in SAS Procedure Mixed. Pearson’s r is a measure of effect size (see Methods). A. Antibiotics decreased food consumption in the HR mice (repeated-measures analysis interaction p=0.0467). B. Food consumption with wheel running as an additional covariate. The interaction between linetype and antibiotics is no longer significant.

Figure 7.

Average daily water consumption during the baseline period (days 8–14) compared to during the antibiotic (ABX) treatment period (days 15–24), with body mass as a covariate. Data are presented as least squares means ± standard errors from repeated-measures analyses in SAS Procedure Mixed. Pearson’s r is a measure of effect size (see Methods). A. Water consumption increased while on antibiotics. B. When included as an additional covariate, wheel running was a significant positive predictor, but water consumption was still higher while on antibiotics. This result differs from food consumption (Figure 6).