Discovery of intestinal microorganisms that affect the improvement of muscle strength

Abstract This study explores a new method to investigate how gut bacteria influence the host, specifically focusing on muscle strength, independent of the host's genetic background. Fecal transplants from humans (FMT) into mice revealed a dramatic impact of gut bacteria on muscle strength, with some mice experiencing increases, no change, or decreases. Analysis of the gut bacterial communities showed distinct compositions between mice with different muscle strength outcomes. Further investigation identified two bacterial species, Lactobacillus johnsonii (L. johnsonii) and Limosilactobacillus reuteri (L. reuteri), whose abundance correlated with improved muscle strength. Supplementation with these bacteria in healthy mice confirmed their ability to enhance muscle strength. Interestingly, the bacteria appear to work by increasing the production of follistatin (FST) and insulin-like growth factor-1 (IGF1), proteins crucial for muscle growth. This study provides the first evidence that specific gut bacteria can directly improve muscle strength and introduces a novel approach to studying the gut microbiome's influence on complex traits.