Abstract Body: Background: Numerous gut microbial metabolites including phenylacetylglutamine (PAGln) are associated with increased cardiovascular disease risk and mortality. However, little is known about the cellular-specific perturbations by which PAGln may drive cardiovascular dysfunction.

Aims: To understand if elevated PAGln leads to cardiovascular dysfunction and what direct cardiac- and vascular-specific pathophysiology is occurring.

Methods: Herein, we subject C57Bl/6N male mice to pharmacological increases in circulating PAGln (50mg/kg) or vehicle twice daily for 20 days. We performed echocardiography, invasive hemodynamics, and vascular reactivity assays. We also performed ex vivo cardiomyocyte cell physiology experiments in the presence or absence of PAGln. Moreover, to understand vascular effects we subjected endothelial cells to PAGln and looked at expression of proinflammatory and cell adhesion molecules.

Results: We first performed LC-MS/MS analysis demonstrating significant elevation in PAGln levels in multiple tissues compared to vehicle. There was no significant alteration in cardiac structure and function through echocardiographic analysis. Invasive hemodynamic assessment of systemic blood pressure showed no change, however left ventricular filling pressures were significantly elevated in PAGln group. Aortic rings subjected to varying concentrations of acetylcholine in the PAGln-treated animals were significantly impaired compared to vehicle controls. Given the elevated filling pressures and aberrant vascular endothelial relaxation we measured nitrite levels. Nitrite was significantly reduced in the plasma, cardiac, and liver tissue in PAGln group. Cardiomyocyte fractional shortening was significantly increased compared to baseline and equivalent to b-adrenergic agonism. PAGln hypercontractility was not inhibited with adrenergic antagonism. Vascular endothelial cells which were exposed to PAGln had an increase in expression of proinflammatory and cell adhesion molecules versus vehicle.

Conclusion: Our data demonstrates that PAGln drives cardiovascular dysfunction through cardiomyocyte hypercontractility and inducing vascular coronary endothelial cell activation in vitro.