Plasma bacterial metabolites as biomarkers for atherosclerosis
Cardiovascular diseases, which are a major cause of death, are most often caused by atherosclerosis. To deal with this issue, an American study on the microbiota provides additional data to better understand this disease. Objective: to better identify its underlying mechanisms in order to improve follow-up and minimize postoperative risk.
Current treatments (statins) are considered to be the most effective ones to fight atherosclerosis. Making progress in this field is becoming necessary to improve patient care. That is why, a team of American researchers tried to determine whether the microbiota, and more precisely plasma metabolites, could serve as a new predictive biomarker not only for atherosclerosis but also for vascular surgery outcomes.
Some metabolites are already known atherosclerosis biomarkers, but their interactions in connection with the clinical course of the disease and the postoperative monitoring have never been examined. Indole- and phenyl-derived metabolites are two types of microbial metabolism derivatives which have been found in patients with advanced atherosclerosis following a carotid endarterectomy procedure, open leg revascularization or amputation in leg ischemia. Follow-up was carried out during one year, including a register of deaths and postoperative cardiac complications. The control group included no cases of peripheral artery disease, stroke or myocardial infarction.
Potential novel biomarkers
Results: concentrations of indole- and phenyl-derived microbial metabolites are biomarkers for advanced atherosclerosis and predictive factors of postoperative complications. Tryptophan, indole-3-propionic acid and indole-3-aldehyde concentrations are negatively associated with advanced atherosclerosis, whereas the kynurenine/tryptophan ratio is positively associated. Furthermore, the kynurenine/tryptophan ratio and hippuric acid concentration were able to identify patients with a high postoperative complication risk. Since we know that tryptophan depletion activates stress pathways and that the kynurenine/tryptophan ratio is high in case of overstimulation of the immune system (infections, autoimmune diseases), it is not surprising that derivatives of these metabolites are associated with atherosclerosis, which is a chronic inflammatory disease. These results need to be confirmed with wider parameters such as the analysis of microbiota, diet, concomitant treatments , and a more precise patient stratification. According to the study authors, measuring these metabolites is a promising lead that needs to be further investigated.
Cason, C. A. et al. Plasma microbiome-modulated indole- and phenyl-derived metabolites associate with advanced atherosclerosis and postoperative outcomes. J. Vasc. Surg. (2017). doi:10.1016/j.jvs.2017.09.029