Identification of causal plasma metabolite biomarkers for ischemic stroke using Mendelian randomization and mediation analysis

The Global Burden of Disease Study 2021 reports that stroke remains a leading cause of death, with ischemic stroke (IS) presenting significant challenges in screening, prevention, and treatment. We explored the causal effects of 1,400 plasma metabolites on IS outcomes using a two-sample Mendelian randomization (MR) framework. We assessed causal relationships between IS and 11 common clinical risk factors and further examined these relationships for metabolites. Mediation analysis identified mechanisms for metabolites affecting both IS and its risk factors. Finally, a phenome-wide association study (PheWAS) MR analysis evaluated the side effects and additional indications of IS-associated metabolites across 3,948 phenotypes from the UKBB GWAS. Nineteen metabolites showed a causal relationship with IS. MR analysis confirmed body mass index (BMI), high-density lipoprotein (HDL), systolic blood pressure (SBP), diastolic blood pressure (DBP), and type 2 diabetes (T2D) as risk factors for IS. Among 136 metabolites associated with at least one IS risk factor, 132 were linked to risk factors but not directly to IS. BMI, DBP, and coffee intake mediated the causal relationship between IS and the levels of 1-stearoyl-GPG (18:0), 1-oleoyl-2-linoleoyl-GPE (18:1/18:2), Octadecadienedioate (C18:2-DC), and X-24,951. Phe-MR analysis indicated that these metabolites were protective and affected other indications similarly to IS. Our findings reveal causal pathways and identify four potential biomarkers for IS, providing new insights for its screening, prevention, and treatment.