WP1 – Cardiac Fibrosis
During the first reporting period, efforts focused primarily on the cardiac effects of imidazole propionate (ImP). Circulating ImP levels were quantified in large cohorts of patients with coronary artery disease (CAD) and heart failure (HF). High ImP concentrations were independently associated with major adverse cardiovascular events (MACE), mortality, and cardiac fibrosis, identifying ImP as a novel prognostic biomarker for cardiovascular risk.
In experimental models, kinetic studies revealed that 8 weeks of ImP treatment induces robust myocardial fibrosis, establishing this as the optimal duration for mechanistic studies. Functional experiments demonstrated that ImP activates cardiac fibroblasts via p38γ-dependent signalling, promoting proliferation and fibrotic remodelling. This mechanism was confirmed in vitro, where a p38γ inhibitor completely blocked ImP-induced fibroblast activation. Preliminary single-cell RNA sequencing identified distinct fibroblast subpopulations emerging after ImP exposure, supporting cellular heterogeneity in the fibrotic response.
Together, these studies provide compelling evidence that the ImP–p38γ axis links gut microbial metabolism to cardiac fibrosis. The findings have generated multiple manuscripts (submitted and published) and form a strong mechanistic basis for subsequent translational studies.
WP2 – Liver Fibrosis
In parallel, the hepatic arm of the project progressed as planned. Preliminary clinical data show a trend toward elevated ImP levels in patients with metabolic dysfunction–associated steatohepatitis (MASH), and cohort expansion is ongoing. Experimental work demonstrated that 8 weeks of ImP exposure similarly induces hepatic fibrosis in western diet–fed mice, mirroring cardiac findings. Transcriptomic profiling experiments are completed, with sequencing analyses pending. These results establish robust conditions for upcoming tissue-specific studies on ImP-driven liver fibrosis.
WP3 – Microbial Inhibitor Development
Significant progress has been made in developing inhibitors of urocanate reductase (UrdA), the bacterial enzyme responsible for ImP synthesis. A nanomolar-range inhibitor was identified and shown to effectively suppress ImP production across several bacterial species expressing functional UrdA. In bioreactor systems modelling the gut microbiota, the inhibitor markedly reduced ImP generation without affecting overall microbial growth, indicating strong selectivity and safety. Preparations are underway to test these inhibitors in vivo.
Summary of Outcomes
After 24 months, IMPACT has:
Identified ImP as an independent biomarker and causal mediator of cardiac fibrosis and cardiovascular events.
Defined the p38γ signalling pathway as central to ImP-induced fibrotic remodelling.
Established 8-week treatment protocols as optimal for fibrosis induction in both cardiac and hepatic models.
Discovered a potent, selective UrdA inhibitor that blocks microbial ImP production in vitro and ex vivo.
Collectively, these results provide the first experimental evidence linking gut microbial metabolism to fibrotic disease and lay the groundwork for microbiome-targeted therapeutic strategies in heart failure and MASH.
