Effects of Exercise on Gut Microbiome and Serum Metabolomics in Post-Traumatic Osteoarthritis Rats

<b>Objective:</b> The aim of this work is to investigate the impact of exercise on gut microbiome composition, serum metabolites, and their correlation with osteoarthritis (OA) severity. <b>Methods:</b> Thirty-six Sprague-Dawley (SD) rats were randomly divided into four groups: Sham rats without treadmill walking (Sham/Sed group, <i>n</i> = 9), Sham rats with treadmill walking 2 months (Sham/TW2M group, <i>n</i> = 9), PTOA rats without treadmill walking (PTOA/Sed group, <i>n</i> = 9), and PTOA rats with treadmill walking 2 months (PTOA/TW2M group, <i>n</i> = 9). The PTOA model was induced by transection of the anterior cruciate ligament (ACLT) and destabilization of the medial meniscus (DMM). Histological evaluation and micro-CT analysis were performed to observe the pathological changes in cartilage and subchondral bone, respectively. Additionally, we conducted 16S rDNA sequencing of fecal samples and untargeted metabolomic analysis using liquid chromatography-mass spectrometry (LC-MS) of serum samples to detect the alteration of gut microbiota composition and metabolites. <b>Results:</b> Exercise effectively mitigated OA-related pathological changes, including articular cartilage degeneration and subchondral bone loss. Moreover, 16S rDNA sequencing analysis of gut microbiome revealed a decreased abundance of <i>Bacteroidetes</i> (<i>p</i> < 0.01), <i>Bacteroidia</i> (<i>p</i> < 0.01), <i>Rikenellaceae</i> (<i>p</i> < 0.01), [<i>Paraprevotellaceae</i>] (<i>p</i> < 0.01), and <i>Paraprevotella</i> (<i>p</i> < 0.01) but an increase in <i>Firmicutes</i> (<i>p</i> < 0.01) in PTOA/TW2M group rats compared with PTOA/Sed group as a response to exercise. In addition, the results of metabolomics analysis showed that exercise treatment contributed to the upregulation of Daidzein and Anthranilic acid and downregulation of 1-Palmitoyllysophosphatidylcholine. Moreover, the correlation analysis showed that <i>Rikenellaceae</i> significantly positively correlated with both OARSI (r = 0.81, <i>p</i> < 0.01) and Mankin score (r = 0.83, <i>p</i> < 0.01) and negatively correlated with the serum level of Anthranilic acid (r = -0.56, <i>p</i> < 0.01) and Daidzein (r = -0.46, <i>p</i> < 0.01). <b>Conclusions:</b> Exercise can effectively mitigate OA through slowing down articular cartilage degeneration and subchondral bone loss, modulating gut microbiota composition, and increasing beneficial metabolites.