Abstract
The microbiota enhances exercise performance and regulates host physiology and energy metabolism by producing beneficial metabolites via bacterial fermentation. In this study, we discovered that germ-free (GF) mice had a reduced capacity for aerobic exercise as well as low oxygen consumption rates and glucose availability. Surprisingly, GF mice showed lower body weight gain and lower fat mass than specific pathogen-free (SPF) mice. Therefore, we hypothesized that these paradoxical phenotypes could be mediated by a compensatory increase in lipolysis in adipose tissues owing to impaired glucose utilization in skeletal muscle. Our data revealed that gut microbiota depletion impairs host aerobic exercise capacity via the deterioration of glucose storage and utilization. The improved browning ability of GF mice may have contributed to the lean phenotype and negatively affected energy generation. These adaptations limit obesity in GF mice but impede their immediate fuel supply during exercise, resulting in decreased exercise performance.