abstract
Background: Multiple Sclerosis (MS) results from genetic predisposition and environmental variables, including elevated Body Mass Index (BMI) in early life. This study addresses the effect ofBMI on the epigenome ofmono- cytesand diseasecourseinMS. Methods: Fifty-four therapy-naive Relapsing Remitting (RR)MS patientswith high and normal BMI received clin- ical andMRI evaluation. Blood samples were immunophenotyped, and processed for unbiased plasma lipidomic profiling and genome-wide DNA methylation analysis of circulating monocytes. The main findings at baseline were validated in an independent cohort of 91 therapy-naïve RRMS patients. Disease course was evaluated by a two-year longitudinal follow up and mechanistic hypotheses tested in human cell cultures and in animal models ofMS. Findings: Higher monocytic counts and plasma ceramides, and hypermethylation of genes involved in negative regulation ofcell proliferationwere detected in the high BMI group ofMSpatients compared to normal BMI. Cer- amide treatment of monocytic cell cultures increased proliferation in a dose-dependent manner and was prevented by DNA methylation inhibitors. The high BMI group ofMS patients showed a negative correlation be- tween monocytic counts and brain volume. Those subjects at a two-year follow-up showed increased T1 lesion load, increased disease activity, and worsened clinical disability. Lastly, the relationship between body weight, monocytic infiltration, DNA methylation and disease course was validated in mouse models ofMS. Interpretation: High BMI negatively impacts disease course in Multiple Sclerosis by modulating monocyte cell number through ceramide-induced DNA methylation of anti-proliferative genes
