Background and aims: 
Accumulating evidence suggest a critical role of distinct gut microbiota-related metabolites in the development of cardiometabolic and -vascular diseases. The amino-acid derived metabolite imidazole propionate (ImP) is increased in patients with type II diabetes. However, its role in coronary heart disease has not been examined, so far. Here we investigated ImP plasma levels in patients with coronary artery disease (CAD) as compared to patients without CAD (control). Moreover, we assessed the effects of ImP on endothelial cell functions and activation as well as on vascular regeneration in a murine model of carotid injury.

Methods and results: 
Plasma ImP levels were investigated in a cohort of patients (n = 837) undergoing elective invasive cardiac evaluation due to suspected CAD or progression of CAD. Significantly higher levels of ImP were observed in CAD patients as compared to controls. In experimental settings, cell migration and angiogenic ability of primary human aortic endothelial cells (HAECs) were examined upon treatment with ImP at different concentrations (10 nM and 100 nM) using wound scratch or matrigel tube formation assays. ImP significantly reduced endothelial cell migration and the formation of tube-like structures on extracellular matrix compared to control treatment. Transcriptomic profiling, western blotting and immunostaining of HAECs revealed altered regulation of a number of genes involved in angiogenesis in ImP treated cells.  In particular, we found disturbed PI3K/Akt/FoxO1 signaling upon ImP treatment. Moreover, ImP significantly enhanced the expression of cellular adhesion-molecules ICAM-1, VCAM-1 and E-Selectin leading to increased adhesion of monocytes (THP-1) to HAECs under flow condition indicating increased endothelial inflammation upon ImP. Vascular regeneration was analyzed in vivo using a carotid artery injury model in C57BL/6N mice treated with ImP (400 µg) or vehicle for three weeks via drinking water. Re-endothelialization was determined by Evans blue staining 3 days post injury. Our results showed that treatment with ImP significantly impaired wound healing and endothelial repair as compared to control animals.

Conclusion: 
For the first time, we demonstrate elevated plasma ImP levels in patients with CAD as compared to patients without CAD. ImP exerts anti-angiogenic functions in the endothelium and impairs endothelial repair after injury via dysregulation of PI3K/Akt/FoxO1 signaling. Our findings may contribute to the development of novel gut microbiota-related strategies targeting intestinal production of ImP to prevent or treat CAD.