Late-in-life treadmill training mitigates gut microbiome imbalances and cardiovascular disease risk in mice

Primary aging associates with an imbalanced gut microbiome and cardiovascular disease (CVD) risk in mice and humans. Strong evidence from clinical and preclinical studies supports that habitual physical exercise improves cardiovascular function and intestinal health in adults. Here we tested the hypothesis that exercise training, even when initiated late-in-life, reestablishes a beneficial and cooperative intestinal microbiome to an extent that associates with reduced risk for CVD. At 21 mo of age, male C57BL/6 mice started a progressive resistance treadmill training program 6 days per week (Old + ETR) for 12 wk. Twenty-one-month-old (Old) and 4-mo-old (Adult) male mice remained sedentary. First, reductions in exercise capacity and soleus muscle citrate synthase activity displayed by Old vs. Adult mice were restored in Old + ETR animals. Next, systolic function [fractional shortening (FS)], diastolic function (E/A ratio), and overall left-ventricular function [myocardial performance index (MPI)] otherwise depressed in Old vs. Adult mice were normalized in Old + ETR animals. Third, elevated trimethylamine (TMA) and TMA <i>N</i>-oxide (TMAO), and heightened inflammatory markers [e.g., interferon (IFN)-γ and keratinocyte-derived chemokine (KC)], observed in Old vs. Adult mice were lowered in Old + ETR animals. Importantly, the abundance of beneficial microbial features, including <i>Bacteroides</i>, Muribaculaceae, <i>Parabacteroides</i>, and the <i>Rikenellaceae RC9</i> gut group, otherwise depressed by aging, was normalized in Old + ETR mice. Finally, the <i>Rikenellaceae RC9</i> gut group was positively correlated with FS, and Parabacteroides was negatively correlated with IFN-γ. These findings support that late-in-life exercise training beneficially remodels the gut microbiome to an extent that associates with reduced CVD risk in male mice.<b>NEW & NOTEWORTHY</b> It is unknown whether exercise training, if started late-in-life, reestablishes a beneficial and cooperative intestinal microbiome. Here we demonstrate that a 12-wk treadmill running program in older mice rejuvenates the gut microbiome and attenuates markers of cardiovascular disease (CVD) risk. Notably, specific microbial taxa correlate with activity-induced improvements in overall myocardial performance and inflammation, highlighting the importance of gut health on CVD and illustrating the restorative benefits that can be attained from a low-cost lifestyle intervention.