Supplementary Material for: Circulating metabolites and cardiovascular disease in Asians with chronic kidney disease

Introduction Chronic kidney disease (CKD) is a growing public health problem, with significant burden of cardiovascular disease and mortality. The risk of cardiovascular disease in CKD is elevated beyond that predicted by traditional cardiovascular risk factors, suggesting that other factors may account for this increased risk. Through metabolic profiling, this study aimed to investigate the associations between serum metabolites associated with prevalent cardiovascular disease in Asian patients with CKD to provide insights into the complex interactions between metabolism, cardiovascular disease in CKD. Methods This was a single-center cross-sectional study of 1122 individuals from three ethnic cohorts in the population-based Singapore Epidemiology of Eye Disease (SEED) study (153 Chinese, 707 Malays, and 262 Indians) aged 40-80 years with CKD (estimated glomerular filtration rate <60 mL/min/1.73 m2). Nuclear magnetic resonance (NMR) spectroscopy was used to quantify 228 metabolites from participants’ serum or plasma. Prevalent cardiovascular disease was defined as self-reported myocardial infarction, angina, or stroke. Multivariate logistic regression identified metabolites independently associated with cardiovascular disease in each ethnic cohort. Metabolites with the same direction of association in all three cohorts were selected and those significantly associated with cardiovascular disease after Bonferroni correction were meta-analyzed. Results Cardiovascular disease was present in 275 (24.5%). Participants with cardiovascular disease tend to be male, of older age, with hypertension, hyperlipidemia and diabetes; with lower systolic and diastolic blood pressure (BP), high-density lipoprotein (HDL)- and low-density lipoprotein (LDL)- cholesterol than those without cardiovascular disease. After adjusting for age, sex, systolic blood pressure, diabetes, total cholesterol and HDL-cholesterol, 10 lipoprotein subclass ratios and 6 other metabolites were significantly associated with prevalent cardiovascular disease in at least one cohort. Meta-analysis with Bonferroni correction for multiple comparisons found that lower tyrosine, leucine and valine concentrations and lower cholesteryl esters to total lipid ratio in intermediate-density lipoprotein (IDL) were associated with cardiovascular disease. Discussion/Conclusion In Chinese, Malay and Indian participants with CKD, prevalent cardiovascular disease was associated with tyrosine, leucine, valine and cholesteryl esters to total lipid ratios in IDL. Increased cardiovascular risk in CKD patients may be contributed by altered amino acid and lipoprotein metabolism. The presence of CKD and ethnic differences may affect interactions between metabolites in health and disease, and with greater understanding will allow us to better risk stratify patients, and also individualize care with consideration of ethnic disparities.