Oral Fusobacterium nucleatum aggravates heart injury in mice

Myocardial ischemia-reperfusion injury (MIRI) remains a major complication. Fusobacterium nucleatum (F. nucleatum), an oral pathobiont associated with cardiometabolic disease, may influence host physiology by reshaping gut microbial function through an oral-gut axis. Whether such microbial interactions contribute to MIRI remains unclear. An oral F. nucleatum gavage mouse model and cohorts were established to investigate the effect of oral F. nucleatum on MIRI, gut microbial histidine metabolism including imidazole propionate (ImP) production, the association of ImP with coronary heart disease (CHD), and its microbial sources. MIRI was induced with or without antibiotic-mediated microbiota depletion and/or ImP administration, and p62 dependence was examined by knockdown approaches in vitro and in vivo. Plasma metabolites, cardiac injury, ultrastructure, and p62/mTOR signaling were assessed. F. nucleatum aggravated MIRI despite the absence of persistent colonic colonization. Instead, F. nucleatum altered gut microbial composition, including Lactobacillus abundance, and was associated with elevated circulating ImP. Antibiotic-mediated microbiota depletion reduced ImP and attenuated myocardial injury. Plasma ImP was elevated in patients with CHD, and ImP-producing capacity was supported primarily by gut microbiota urocanate reductase (UAR)-associated functions. In H9c2 cells, ImP exacerbated hypoxia/reoxygenation injury, and increased the autophagy adaptor p62 together with downstream mTOR/S6K1 signaling. p62 knockdown attenuated the mTOR/S6K1 response and injury-associated changes, whereas IRS1 suppression persisted. F. nucleatum reshapes gut microbial metabolism, thereby amplifying MIRI via ImP. ImP emerges as a functional mediator linking oral dysbiosis to MIRI, and reducing microbiota-derived ImP may represent a more mechanistically grounded strategy to mitigate MIRI.