A metabolome-wide Mendelian randomization study prioritizes causal circulating metabolites for multiple sclerosis

ObjectiveTo prioritize circulating metabolites that likely play causal roles in the development of multiple sclerosis (MS). MethodsTwo-sample Mendelian randomization analysis was performed to estimate the causal effects of 571 circulating metabolites on the risk of MS. Genetic instruments for circulating metabolites were obtained from three previous genome-wide association studies (GWAS) of the blood metabolome, while genetic associations with MS were from a large GWAS by the International Multiple Sclerosis Genetics Consortium. The primary analysis was performed with the multiplicative random-effect inverse variance-weighted method, while multiple sensitivity analyses were conducted with the weighted median, weighted mode, MR-Egger, and MR-PRESSO. ResultsA total of 29 metabolites had suggestive evidence of causal associations with MS. Genetically instrumented levels of serine (OR = 1.56, 95% CI = 1.25 - 1.95), lysine (OR = 1.18, 95% CI = 1.01 - 1.38), acetone (OR = 2.45, 95% CI = 1.02 - 5.90), and acetoacetate (OR = 2.47, 95% CI = 1.14 - 5.34) were associated with a higher MS risk. Total cholesterol and phospholipids in large very-low-density lipoprotein were associated with a lower MS risk (OR = 0.83, 95% CI = 0.69 - 1.00; OR = 0.80, 95% CI = 0.68 - 0.95), but risk-increasing associations (OR = 1.20, 95% CI = 1.04 - 1.40; OR = 1.13, 95% CI = 1.00 - 1.28) were observed for the same two lipids in very large high-density lipoprotein. ConclusionsOur metabolome-wide Mendelian randomization study prioritized a short list of circulating metabolites, such as serine, lysine, acetone, acetoacetate, and lipids, that likely have causal associations with MS.