The unique gut bacteria Roseboria has been linked to stronger muscles and better fitness

Scientists from the University of Almeria and the University of Granada, together with researchers from the Leiden University Medical Center (LUMC, Netherlands), have identified gut bacteria of the genus Roseboria that are associated with strong muscles and good physical condition.

The results support the gut-muscle axis concept. Jonathan Ruiz, professor in the Department of Physical Education and Sport at UGR and researcher at the Joint University Institute for Sport and Health (iMUDS), says: “Taken together, our findings provide strong evidence that the gut-muscle axis exists in which identified bacteria positively alter muscle metabolism and muscle strength.”

In addition, scientists have observed that the bacterium is lower in older adults than in younger adults, suggesting that its levels may decrease with age, when muscle mass is lost.

This opens up the possibility that the bacteria under investigation could be used as a probiotic to help maintain muscle strength during aging.

Borja Martinez Tells, Researcher, University of Almeria

The relationship between gut bacteria and muscle function

The team analyzed whether certain gut microbes are related to muscle strength and physical condition. To do this, they studied the bathing patterns of 90 healthy young adults (ages 18-25) and 33 adults (age 65 or older).

Participants in the experiments also performed several tests of physical fitness, including arm strength, leg strength, and upper body strength (chest muscles), and their maximal oxygen consumption, an index of cardiorespiratory capacity, was measured.

Among the numerous groups of bacteria that have been discovered, the genus Roseboria stands out, as its abundance is associated with increased muscle mass and strength. In particular, one species – Roseburia inulinivorans – shows a correlation with physical fitness.

In the experiment, older adults who had this bacteria showed 29% greater grip strength than those who did not have the bacteria. In young adults, greater abundance of these bacteria is associated with both higher hand-grip strength and higher cardiorespiratory capacity.

Other species of the Roseburia genus show different patterns: Roseburia intestinalis is associated with leg and upper body strength in young adults, while Roseburia faecis and Roseburia hominis are not significantly associated with the studied indicators.

Assessment of gut-muscle connectivity

To determine whether Roseburia can directly affect muscle function, researchers conducted experiments with mice. After temporarily reducing the gut microbiota with antibiotics, the animals were given a human strain of the bacteria once a week for eight weeks.

Mice that were treated with the bacteria showed a nearly 30% increase in grip strength on their faces compared to animals that did not receive it.

In addition, the mice developed larger muscle fibers and a higher proportion of type II muscle fibers, which are fast-twitch fibers, which are important for strength and power, in the soleus muscle of the calf. These changes were also accompanied by metabolic changes in proteins and enzymes that are key to muscle energy production.

Limitations

The researchers point out a number of limitations. In experiments with mice, human strains of Roseburia did not permanently colonize the intestine, and the study did not directly evaluate certain biological mechanisms such as inflammatory pathways or neuromuscular signaling. Therefore, long-term research will be necessary to determine whether changes in R. inulinivorans levels lead to improvements in muscle function or are a result of them.

The study was led by Ramon and Cajal researcher Borja Martínez Telles from the Department of Nursing, Physiotherapy and Medicine of the University of Almeria, in collaboration with UGR Professor Jonathan Ruiz and researcher Patrick CN Renson (LUMC). Scientists from the University of Groningen (Netherlands) and other Spanish institutions in Valencia and Cádiz also participated in the work. This project was funded by the Martin Escudero Foundation, the Health Research Fund of the Carlos III Health Institute, and Leiden University funds.