Researchers from the University of Almería, the University of Granada, and Leiden University Medical Center (LUMC, Netherlands) have identified a specific intestinal bacterium from the Roseburia genus that is associated with stronger muscles and improved physical condition.
This discovery supports the concept of an intestine-muscle axis, where the identified bacterium appears to positively influence muscle metabolism and strength. This groundbreaking research has been published in the scientific journal Gut.
Key Findings
The study observed that the Roseburia bacterium is less common in older adults compared to young adults. This suggests that its levels may decrease with age, a period often characterized by muscle mass loss. Scientists propose that this bacterium could potentially be developed into a probiotic to help maintain muscle strength during aging.
Study Methodology
To investigate the link between gut microbes and muscle performance, the team analyzed stool samples from 90 healthy young adults (18–25 years old) and 33 older adults (65 years old or older). Participants also underwent various physical fitness assessments, including handgrip strength, leg strength, upper body strength, and maximum oxygen consumption (an indicator of cardiorespiratory capacity).
Among the bacterial groups identified, the Roseburia genus showed a correlation with increased muscle mass and strength. Specifically, several species within the genus were examined:
- Roseburia inulinivorans: This species was directly linked to physical fitness.
- Older adults who had this bacterium present demonstrated 29% greater handgrip strength than those without it.
- In young adults, a higher abundance of Roseburia inulinivorans was associated with both greater handgrip strength and improved cardiorespiratory capacity.
- Roseburia intestinalis: This species was linked to leg and upper body strength in young adults.
- Roseburia faecis and Roseburia hominis: These species did not show significant associations with the measured indicators.
Experimental Validation
To further explore the direct influence of Roseburia on muscle function, researchers conducted experiments with mice. After reducing the mice's gut microbiota with antibiotics, human strains of the bacteria were administered weekly for eight weeks.
The mice receiving the bacteria showed an approximate 30% increase in forelimb grip strength compared to a control group. Additionally, these mice developed larger muscle fibers, specifically a higher proportion of type II (fast-twitch) muscle fibers in the soleus muscle, and exhibited metabolic changes critical for muscle energy production.
Limitations
The researchers noted several limitations in their study. The human strains of Roseburia did not permanently colonize the intestines of the mice in the experiments. The study also did not directly evaluate specific biological mechanisms such as inflammatory pathways or neuromuscular signaling. Further long-term research is required to ascertain whether changes in Roseburia inulinivorans levels directly cause improvements in muscle function or are a consequence of them.
Funding and Collaborating Institutions
This project received funding from the Martín Escudero Foundation, the Health Research Fund of the Carlos III Health Institute, and Leiden University Funds. Participating institutions included the University of Almería, the University of Granada, LUMC, the University of Groningen, and other Spanish institutions.