Intensive Training and Sex Influence Intestinal Microbiota Composition: A Preclinical Approach

Lifestyle, including regular physical activity and dietary habits, influences microbiota composition. Although some studies have demonstrated changes in microbiota composition due to moderate or high intensity training in athletes, the relationship between physical activity and changes in the intestinal bacteria is still a matter of discussion. In addition, as most studies are performed on males, the role of sexual dimorphism deserves to be explored. Therefore, the aim of this preliminary study was to ascertain the influence of an intensive training and the rat’s sex on caecal microbiota composition. For this purpose, female and male 4-week-old Wistar rats were submitted to a 4-week running training program. At the end, caecal samples were collected immediately after performing an exhaustion test to characterize the microbiota composition by 16S rRNA sequencing technique. Parallel groups of female and male sedentary (SED) rats (age matched) were included. The results showed that young female rats had a higher ability to run than males but no sex- or training-associated changes were observed on microbiota diversity and richness indexes among groups. However, the Actinobacteria, Bifidobacteriaceae and Bifidobacterium spp. proportions were significantly higher in male than in female rats when comparing SED groups (p < 0.05), whose proportions in males were decreased by the training program (p < 0.05 vs. SED). On the contrary, female SED rats showed a higher proportion of Odoribacteraceae (belonging to Bacteroidetes), Clostridiaceae and Eubacteriaceae (both Firmicutes) than in the respective male group (p < 0.05), although Eubacteriaceae proportion decreased by running (p < 0.05 vs. SED). However, training increased the proportion of the Paraeggerthella genus (Actinobacteria) in female rats with respect to its sedentary counterpart (p < 0.05). Overall, caecal microbiota composition is modified by intensive training in young rats but there are also sex-based differences that should be considered for interventional studies.