Supplementary Material for: Gut Microbial Product Predicts Cardiovascular Risk in Chronic Kidney Disease Patients

Background: The gut microbiota is altered in patients with chronic kidney disease (CKD), and cardiovascular risk increases with progressive CKD. This study examined the potential link between short chain fatty acids (SCFAs), which are produced by the gut microbiota, and cardiovascular outcomes in patients with CKD. Methods: SCFAs were measured using a targeted liquid chromatography-mass spectrometry platform in baseline plasma samples from 214 patients with CKD enrolled in the Clinical Phenotyping Resource and Biobank Core; 81 patients with coronary artery disease (CAD) and 133 without CAD were randomly assigned to training and validation subsets. The primary outcome was a history of CAD and the secondary outcome was a composite history of cardiovascular disease (CVD) at enrollment. Results: We found significantly higher levels of the SCFA valerate among patients with CAD as compared with patients without CAD in the training set (p < 0.001). The valerate concentrations were also significantly higher among subjects with composite outcomes of CVD compared to those without CVD (p = 0.006). These results were subsequently replicated in the validation set. Logistic regression analysis revealed a strong independent association between plasma valerate levels and CVD in both training and validation sets. When valerate was added to the base clinical model comprising of diabetes, hypertension, urinary protein-creatinine ratio, and estimated glomerular filtration rate, it increased the c-statistics for predicting CVD from 0.68 to 0.79 (p = 0.02) in the training set, an observation which was confirmed in the validation set. ­Conclusion: This study provides evidence for alterations in gut-microbiota-derived SCFAs with advancing CKD, demonstrates the association of higher plasma valerate levels with pre-existing CVD, and reveals areas for future exploration of cardiovascular risk in patients with CKD.