Integrated metagenomic and metabolomic analyses reveal tenacissoside G as a potential non-antimicrobial treatment for bovine endometritis

<h4>Background</h4>Bovine endometritis is a prevalent uterine disease that directly curtails reproductive performance and indirectly reduces milk production by increasing calving intervals. Postpartum uterine bacterial infection is the primary cause of bovine endometritis, which is typically treated with prostaglandin F2α and antimicrobials. However, abuse of antimicrobials has led to the emergence of multidrug-resistant bacteria, threatening both human and animal health. To explore alternatives to antimicrobial therapy for bovine endometritis, we integrated uterine metagenomic and metabolomic analyses and identified a novel bioactive metabolite with therapeutic potential. The potential antibacterial and anti-inflammatory effects of this metabolite against bovine endometritis were evaluated by assessing its inhibitory effect on the growth of F. necrophorum in vitro, and by quantifying histopathological scores and inflammatory cytokine expression levels in an in vivo mouse model of endometritis, respectively.<h4>Results</h4>A total of 40 Holstein dairy cows at 21 days to 30 days postpartum were assigned into heathy cows (n = 15), subclinical endometritis cows (n = 12) and clinical endometritis cows (n = 13) according to clinical signs and laboratory tests for bovine endometritis. The uterine fluid was collected aseptically for metagenomics and metabolomics sequencing to identify bacterial species associated with bovine endometritis and metabolites that could potentially be used for treatment of bovine endometritis. A total of 17 bacterial species were significantly associated with bovine endometritis, with Fusobacterium necrophorum as the most significantly enriched in cows with clinical endometritis compared to healthy counterparts. In total, 391 metabolites were significantly differentially abundant between healthy and clinical endometritis cows. Among these, a plant-derived compound, tenacissoside G was significantly enriched in healthy cows. Notably, the abundance of F. necrophorum was significantly negatively associated with the concentration of tenacissoside G in clinical endometritis cows. Moreover, tenacissoside G significantly inhibited the growth of F. necrophorum in vitro and ameliorated inflammation in endometritis caused by F. necrophorum in a mice model.<h4>Conclusion</h4>This study provides new insights into the relationship between uterine microbiome and metabolites in bovine endometritis, potentially leading to novel strategies for treating bovine endometritis. Furthermore, tenacissoside G exhibits therapeutic effects against endometritis induced by F. necrophorum, and could serve as a potential alternative to antimicrobials for treating endometritis. Video Abstract.