Exploring the Role of Plasma Lipids and Statins Interventions on Multiple Sclerosis Risk and Severity: A Mendelian Randomization Study

BackgroundThere has been considerable interest in statins due to their pleiotropic effects beyond their lipid-lowering properties. Many of these pleiotropic effects are predominantly ascribed to their capacity to inhibit the isoprenylation of Rho small guanosine triphosphatases (Rho GTPases). We aimed to genetically investigate the role of lipids and statin interventions on multiple sclerosis (MS) risk and severity. MethodWe employed two-sample Mendelian randomization (MR) to: (1) investigate the causal role of lipids (high-density lipoprotein cholesterol (HDL-C) and triglycerides (TG)) levels in MS risk and severity, (2) genetically mimic both cholesterol-dependent (via low-density lipoprotein cholesterol (LDL-C) and cholesterol biosynthesis pathway) and cholesterol-independent (via Rho GTPases) effects of statins on MS risk and MS severity. ResultsThe results of MR using the inverse variance weighted method show that lifelong higher HDL-C (OR 1.14 (95% CI 1.04 to1.26), p-value 7.94E-03) increase MS risk, but LDL-C and TG were not. MR results also show that genetically predicted RAC2 (OR 0.86 (95% CI 0.78 to 0.95), p-value 3.80E-03) is implicated causally in reducing MS risk. Furthermore, we found no evidence for the causal role of lipids and genetically mimicked statins on MS severity. There is no evidence of reverse causation between MS risk and lipids. ConclusionsEvidence from this study suggests that HDL-C is a risk factor for MS development. The MR findings suggest that RAC2 (a member of Rho GTPases) is a potent genetic modifier of MS risk. Since RAC2 has been reported to mediate some of the pleiotropic effects of statins, we suggest that statins reduce MS risk via a RAC2-related mechanism(s) (i.e., cholesterol-independent pathway).