Effect of Propionic Acid Supplementation on Endothelial Function

Coronary Artery Disease (CAD) remains a leading cause of morbidity and mortality worldwide despite improved mitigation of traditional risk factors. Large association studies have linked the gut microbiome alterations with inflammation, CAD, and traditional CAD risk factors. Subsequent studies have shown concomitant improvements in gut dysbiosis, inflammation, and cardiometabolic diseases using probiotics and other gut-modulating therapies. To date, many studies have shown a correlative relationship between intestinal bacteria composition and the presence of CAD, or severity of heart attacks, but few have begun to elucidate potential metabolic and immunologic mechanisms.

The investigator's recently supplemented Lactobacillus plantarum 299v in men with stable CAD, which improved systemic inflammation and brachial artery flow-mediated dilation (BA-FMD) - a measure of endothelial function and a predictive CAD precursor. Improvement in BA-FMD positively correlated with increased serum propionic acid (PA) concentrations. PA is a gut microbiome-derived short chain fatty acid (SCFA) with known human vascular receptors and implicated in endothelial function, innate immunity, and glucose homeostasis.

Whether PA is mediating improvement in endothelial dysfunction or inflammation in the investigator's prior experiment remains unknown. The investigator's objective is to determine whether endothelial cell function is improved by dietary supplementation of sodium propionate in patients with established coronary artery disease. Furthermore, the investigators wish to elucidate to what extent inflammation is reduced by this therapy, by both measuring serum inflammatory markers and by seeing if plasma from treated patients induces anti-inflammatory transcriptomic responses from cultured endothelial cells and peripheral blood mononuclear cells, both of which are involved in atherosclerosis.

Specific Aim 1 will determine the impact of dietary PA supplementation on endothelial function and traditional CAD risk factors in patients with CAD. The investigators will utilize ultrasound to assess the percent change in BA-FMD before and after dietary PA supplementation. The extent of endothelium-dependency of these responses will be tested by measuring BA-FMD following nitroglycerin administration. The investigators will also measure markers representative of traditional CAD risk factors, such as lipid levels and HgbA1C.

Specific Aim 2 will determine anti-inflammatory changes in vivo and in transcriptomic signatures of cultured EC and PBMCs induced by dietary PA. The investigators will measure changes to systemic serum inflammatory markers involved in atherosclerotic processes using a targeted metabolomics approach, using plasma from the investigator's cohort before and after PA supplementation. Plasma samples will be used to incubate aforementioned cells to compare transcriptomic signatures of cells subjected to pre-supplementation plasma versus post-supplementation plasma. The investigators will use Ingenuity Pathway Analysis to determine changes to inflammatory pathways and i.i.com to determine whether more anti-inflammatory signatures were induced.

Specific Aim 3 will determine the impact of PA supplementation on gut microbiome taxonomy and diversity. As an optional additional clinical study activity, the investigators will collect stool samples before and after dietary PA supplementation, subject samples to multiplex 16S RNA sequencing, and calculate the Shannon Diversity Index. This will help us determine changes in individual gut microbiome constituents and diversity of the entire population.