Background

NMOSD is an autoimmune disorder characterized by acute, unpredictable relapses that result in accumulating disability. Satralizumab, a humanized, monoclonal recycling antibody that targets the interleukin-6 receptor, reduced relapse frequency and had a favourable safety profile vs placebo in two randomized, phase 3 clinical trials: SAkuraSky (satralizumab in combination with baseline immunosuppressants; NCT02028884), and SAkuraStar (satralizumab monotherapy; NCT02073279).

Objectives

To assess the impact of satralizumab on relapse severity in patients with NMOSD.

Methods

Patients in the SAkura studies received satralizumab 120mg or placebo at Weeks 0, 2, 4, and Q4W thereafter. This analysis was performed using data from the pooled intention-to-treat population across the double-blind periods of both studies. We assessed the severity of protocol-defined relapses (PDRs) by comparing patients’ Expanded Disability Status Scale (EDSS) score at PDR vs their score prior to relapse (last scheduled study visit). A similar analysis on optic neuritis PDRs was performed using visual Functional Systems Score (FSS). A PDR was categorised as severe if it resulted in a change of ≥2 points on the EDSS or visual FSS (optic neuritis analysis). Kaplan-Meier analyses were performed to assess time to first severe PDR. Additionally, the number of patients receiving acute therapy for any relapse was compared between treatment groups.

Results

Overall, 178 patients were included in the analyses. In the satralizumab group, 27 of 104 patients (26%) experienced a PDR vs 34 of 74 patients (46%) in the placebo group. The proportion of PDRs that were severe was lower in patients receiving satralizumab vs placebo (5 of 27 events [19%] vs 12 of 34 events [35%]). Similarly, the proportion of optic neuritis PDRs that were severe was lower in patients receiving satralizumab vs placebo (2 of 8 events [25%] vs 5 of 13 events [39%]). Across all patients, there was a 79% reduction in severe PDR risk with satralizumab vs placebo (hazard ratio [95% CI]; 0.21 [0.07–0.61]; p=0.002). A lower proportion of patients receiving satralizumab were prescribed acute relapse therapy vs placebo (38% vs 58%; odds ratio [95% CI] 0.46 [0.25–0.86], p=0.015).

Conclusions

Patients treated with satralizumab had a lower risk of severe relapse, and were less likely to receive acute relapse therapy compared with placebo. The number of patients with severe PDRs was low, so results should be interpreted with caution.

Background

In the randomized, double-blind, placebo-controlled, phase 3 PREVENT trial (NCT01892345), eculizumab was well tolerated and significantly reduced relapse risk vs placebo in patients with aquaporin-4 immunoglobulin G-positive (AQP4+) neuromyelitis optica spectrum disorder (NMOSD). The treatment effect observed in a prespecified subgroup of patients who received eculizumab monotherapy vs placebo alone (i.e. without concomitant immunosuppressive therapy [IST]) was consistent with the overall population.

Objectives

To examine the long-term efficacy and safety of eculizumab monotherapy in patients with AQP4+ NMOSD during PREVENT and/or its ongoing open-label extension (OLE; NCT02003144).

Methods

During PREVENT and its OLE, adults with AQP4+ NMOSD received eculizumab (maintenance dose, 1200 mg/2 weeks) or placebo (PREVENT only) with/without concomitant IST. Relapses, hospitalizations, IST changes and adverse events (AEs) with eculizumab monotherapy (PREVENT and its OLE; interim data cut-off, July 31, 2019) or with placebo alone (PREVENT) were descriptively analyzed post hoc.

Results

During PREVENT and/or its OLE, 33 patients received eculizumab monotherapy for a total of 85.3 patient-years (PY). Adjudicated relapses occurred in 1/33 patients (annualized relapse rate [ARR], 0.012; 95% confidence interval [CI]: 0.002–0.082), vs 7/13 with placebo alone in PREVENT. At 192 weeks, 96.2% of patients who received eculizumab monotherapy were relapse-free (95% CI: 0.757–0.994) vs 93.8% of patients who received eculizumab with concomitant IST (95% CI: 0.867–0.972). No patients receiving eculizumab monotherapy required hospitalization for a relapse and none started an IST. The treatment-related AE rate with eculizumab monotherapy in PREVENT and its OLE was similar to that with placebo alone in PREVENT (181.0 and 186.0 events/100 PY, respectively), the infection rate was similar between these groups (174.1 vs 186.0 events/100 PY), and the treatment-related serious AE rate was lower with eculizumab monotherapy than with placebo alone (5.7 vs 23.3 events/100 PY). No meningococcal infections or deaths occurred among these patients.

Conclusions

A very high proportion of patients who had experienced 1–2 relapses in the pre-study year remained relapse-free through 192 weeks of eculizumab monotherapy. Long-term eculizumab monotherapy was well tolerated. These data support the long-term effectiveness of eculizumab monotherapy in reducing relapse risk in AQP4+ NMOSD.

Background

Alemtuzumab is an anti-CD52 monoclonal antibody therapy approved for treating RRMS. Although alemtuzumab is associated with non–MS-related secondary autoimmune events, the role pre-existing non-MS autoimmunity plays in secondary autoimmunity is unclear.

Objectives

To assess the impact of 1) pre-existing non-MS autoimmunity and 2) post-alemtuzumab thyroid autoimmunity on subsequent onset of new autoimmunity up to 9 years after initiating alemtuzumab.

Methods

In clinical trials (NCT00050778, NCT00530348, NCT00548405, NCT00930553, NCT02255656), patients were monitored for autoimmune adverse events (AEs). All patient- and investigator-reported AEs were recorded. An autoimmune event was pre-existing if it occurred prior to initiating alemtuzumab or was in the medical history database.

Results

A total of 1216 patients from the alemtuzumab clinical development program who received alemtuzumab 12 mg were included in the analysis. Ninety-six had pre-existing non-MS autoimmunity. Up to 9 years after alemtuzumab initiation, the percentage of patients with new autoimmune disease was similar in those with (35.4%) versus without (35.3%) pre-existing autoimmunity; similar percentages of patients with versus without pre-existing autoimmunity had ≥2 new autoimmune events (5.2% vs 8.2%, respectively). Most patients with thyroid disorders at baseline did not experience new autoimmunity after alemtuzumab. Treatment-emergent thyroid autoimmunity after alemtuzumab Course 1 was not associated with subsequent nonthyroid autoimmunity after Course 2 (0% of patients with vs 3.0% of patients without thyroid autoimmunity after Course 1). Similarly, thyroid autoimmunity after Course 2 did not predict nonthyroid autoimmunity after Course 3 (1.8% vs 2.0%, respectively). Among 25,292 patients treated with alemtuzumab in the postmarketing setting as of 31 March 2019, additional events (occurring 18–36 months post treatment) included autoimmune hepatitis (10.7 in 10,000) and hemophagocytic lymphohistiocytosis (2.7 in 10,000).

Conclusions

Over 9 years after alemtuzumab initiation, pre-existing non-MS autoimmunity was not associated with subsequent new autoimmune disease. Emergence of thyroid autoimmunity after Courses 1 and 2 does not appear to predict subsequent serious autoimmune disease.

STUDY SUPPORT: Sanofi and Bayer HealthCare Pharmaceuticals.

Background

Ocrelizumab (Ocre) is an anti-CD20 monoclonal antibody with a known major depleting effect on B cells and marginal on T cells. It is approved for clinical use in highly-active naïve multiple sclerosis (MS) patients and those not responder to previous treatment. In MS patients switching from other drugs prolonged dysfunction of adaptive immune system may occur after discontinuation, posing the need to carefully investigate the safety profile of treatment sequencing.

Objectives

To investigate the B and T cells subsets longitudinal dynamic during treatment with Ocre in patients with MS switching from Fingolimod (FTY) and other treatments (Dimetylfumarate, Interferon Beta, Glatiramer Acetate, Natalizumab, Teriflunomide) compared to naïve patients.

Methods

A multicenter observational 2-year study was conducted in patients starting treatment with Ocre grouped in three arms: naïve (naïve), switching from FTY (pre-FTY), switching from other treatments (other). Data about lymphocyte subtype count (CD3+, CD4+, CD8+ and CD20+) were collected at baseline and every 6 months after starting Ocre. Slope of reduction and proportion of patients with lymphocytes count below the normal lower limit was calculated.

Results

A sample of 135 patients was analysed (37 pre-FTY, 64 other, 34 naïve). At baseline pre-FTY compared to naïve showed significant decrease of CD3+ (1204.54+675.37 cells/mm3 vs 1735.53+653.56, p=0.0003), CD4+ (551.91+254.42 vs 997.03+352.79, p<0.0001), CD8+ (430.38+379.73 vs 537.75+254.34, p=0.027) and CD20+ (88.25+90.94 vs 191.32+149.62, p=0.021) cells. During Ocre the slope of reduction of CD3+ in naïve patients was 5.45 cells/mm3/week (p=0.003). Compared to naïve, the rate of decrease in CD3+ was -1.2 cells/mm3/week in pre-FTY (p=0.087) and +0.19 (p=0.012) in other. The slope of reduction of CD4+ was 2.00 cells/mm3/week in naïve (p=0.072). Compared to naïve the rate of reduction in CD4+ was +0.91 cells/mm3/week in pre-FTY (p=0.061) and +1.70 cells/mm3/week (p=0.012) in other. CD8+ and CD20+ cells decrease was similar among groups (p for interaction between time and treatment = 0.184 and 0.108, respectively). In pre-FTY group compared to baseline the proportion of patients with CD3+ and CD4+ cells lymphopenia was unchanged (16.22% versus 17.14% ; 32.35% versus 34.29%), while the proportion of CD8+ cells was increased (8.82% versus 25.71%).

Conclusions

Our study confirms that Ocre may induce depletion of T cell subsets beyond B cells. Nevertheless, in pre-FTY we also observed a prolonged T- lymphocytopenia , as carry-over effect of the previous therapy. FTY-induced immunosenescence or slow immunoreconstitution may explain this finding.

Background

Previously, we used frequency domain near-infrared spectroscopy (fdNIRS), a non-invasive imaging modality, to show that brain hypoxia exists in a subset of MS patients. Currently, there is limited knowledge on the effects of hypoxia in MS. However, some studies suggest that hypoxia may exacerbate inflammation of the central nervous system (CNS). It is important to elucidate the time-course of hypoxia in relation to inflammation to further understand its role in MS.

Objectives

The aim of the present study was to use fdNIRS to determine if hypoxia in MS resolves quickly or if it is a chronic condition.

Methods

We used fdNIRS to quantify cortical microvasculature hemoglobin saturation (S_tO₂) in 55 controls and 85 MS patients. S_tO₂ values that were 2 standard deviations (SD) below the control mean were defined as hypoxic (<55.7%). Arterial oxygen saturation (S_aO₂) was measured using a pulse oximeter to confirm that reduced S_tO₂ was not systemic in origin. To determine whether the temporal pattern of S_tO₂ relates to changes in acute CNS inflammation, we recruited a subset of MS patients (hypoxic: n=12; normoxic: n=7) for a longitudinal study. We measured S_tO₂ once a week for 4 consecutive weeks, and then once a month for 5 subsequent months. Due to COVID-19-related lab closures, we were only able to obtain S_tO₂ data for the first 8 weeks for 13 of these patients (hypoxic: n=8; normoxic: n=5).

Results

S_tO₂ in MS patients was significantly lower compared to controls (57.6±7.6% vs. 62.3±3.6%, respectively, p=0.002), with no differences in S_aO₂. For the longitudinal study, we found that S_tO₂ values for normoxic and hypoxic MS groups did not change significantly over the course of 8 weeks (F (9, 36.9) =1.44, p=0.255).

Conclusions

To our knowledge, we are the first group to use fdNIRS to identify a subset of MS patients who experience persistent brain hypoxia. As hypoxia in MS patients persists beyond 4 weeks, we argue that it can present as a chronic condition. This indicates that, in these patients, physiological responses such as angiogenesis have not occurred or are not sufficient to result in resolution of hypoxia. With such chronic hypoxia we would predict that in these patients, some symptoms may be a result of this chronic hypoxia. Also, we argue that such chronic hypoxia could exacerbate and further stimulate a pathological immune response (a hypoxia inflammation cycle).

Background

Multiple-Sclerosis-Partners-Advancing-Technology-Health-Solutions (MSPATHS) is an international multicentre digital database that collects clinical information provided directly by patients together with standardized MRI and biomarkers.

Objectives

We identify a Benign multiple sclerosis (BMS) population using Patient-Determined-Disease-Steps (PDDS) as a proxy for EDSS. We describe its physical and non-physical characteristics, and explore the features that best discriminate BMS.

Methods

Cross-sectional study of MSPATHS patients (Feb 2019). In patients with disease duration ≥10 years, BMS was considered when PDDS score<2. We compared BMS and non-BMS in terms of (1)socio-demographic and clinical characteristics, (2)physical status (lower and upper extremity function by Neuro-QoL (LUEF-NQ) and neurological performance tests: walking speed test (WST), manual dexterity test (MDT), processing speed test (PST), contrast sensitivity test (CST)) and non-physical symptoms (anxiety, depression, fatigue, among other NQ domains), and (3)MRI (gadolinium enhancement and new T2 lesions). We built a random forest model to estimate the importance of each variable. Cohen’s d was used for descriptive statistics to categorize differences in small (d=0.2-0.5), medium (d=0.5-0.8) and large (d>0.8). A sensitivity analysis with a 1:1 matched cohort by disease duration was performed.

Results

From 15,257 patients included, 8,349 had a disease duration ≥10 years and 3,852 (46.1%) were classified as BMS. (1)BMS and non-BMS patients were similar for gender, age at disease onset and diagnosis, ethnicity, years of education and smoking status. Compared to non-BMS, BMS had small differences in disease duration (median, 17.2 (12,9-23,4) vs. 20.9 (15,1-28,8 years); d=0.39) but medium/large differences in (2)physical status (LUEF-NQ d=2.06 and 1.53, WST d=0.81, MDT d=0.97, PST d=0.82 and CST d=0.56), as well as, in all non-physical symptoms evaluated by NQ (anxiety d=0.53, depression d=0.69, fatigue d=0.84, stigma d=1.32, cognition d=0.69, social role satisfaction (SRS) d=1.11 and participation (SRP) d=1.19). (3)No differences were found on MRI activity. With 0.88 sensitivity and 0.86 specificity, LUEF-NQ was the most contributing variable for the random forest followed by stigma, SRP, WST, and SRS. The sensitivity analysis showed similar results.

Conclusions

PDDS seems to be a useful disability proxy to identify BMS when using digital technology. LUEF-NQ, stigma, SRP and SRS seem to better discriminate BMS.

Background

Postmortem magnetic resonance imaging (MRI) of formalin-fixed healthy and diseased human brains with ultra-high spatial resolution has the great potential to depict tissue architecture in fine detail, allowing a deeper understanding of pathological processes. Whole-brain imaging is important since it provides neuroanatomic relationships, reference points across distant brain regions, and a comprehensive view of pathologies affecting the brain. However, ultra-high-resolution whole-brain postmortem MRI is challenging and has been so far almost exclusively performed at 7T with specialized hardware.

Objectives

To develop a 3D isotropic 160µm ultra-high-resolution imaging (URI) approach for human whole-brain ex vivo acquisitions on a standard clinical 3T MRI system. To explore the sensitivity and specificity of the approach to specific pathological features of multiple sclerosis (MS).

Methods

A fixed whole human brain from a patient with secondary progressive MS was investigated. Acquisitions were performed on a clinical 3T Siemens Prisma^fit MRI system with standard hardware components. URI is based on a gradient echo sequence similar to the 7T approach by Edlow et al. 2019. However, it allows to acquire an isotropic 160µm resolution with low hardware demands and to directly reconstruct the image data on the standard 3T MRI system. URI images display a strong, susceptibility-enhanced tissue contrast.

Results

The reconstructed URI images depicted with remarkable quality the diseased human MS brain at 3T field strength. URI allowed to distinguish fine anatomical details such as the subpial molecular layer, the stria of Gennari as well as some intrathalamic nuclei. Additionally, because of the unprecedented spatial resolution and contrast at 3T, URI permitted to easily identify the presence of subpial lesions, detailed features of intracortical lesions such the presence of incomplete/complete iron rims or patterns of iron accumulation in the entire lesion core in both cortical and white matter lesions (CLs/WMLs), lesions affecting the convoluted layers of the cerebellar cortex and nascent submillimetric CLs/WMLs.

Conclusions

URI provides a comprehensive microscopic insight into the whole-human brain at 3T through the micrometric resolution and a tissue-specific, susceptibility-enhanced contrast. We propose URI as an excellent approach to investigate microscopic brain changes of complex pathologies like MS.

Background

In multiple sclerosis (MS), thalamic integrity is affected both directly by demyelination, neuronal loss and increasing iron concentration, and indirectly by remote gray and white matter lesions affecting neural projections into and out of the thalamus. Thalamic atrophy may therefore reflect a large fraction of MS-related brain damage and thus represent a useful marker of overall damage and therapeutic efficacy.

Objectives

To assess the efficacy of ocrelizumab (OCR) in patients switching to or maintaining OCR therapy on thalamic atrophy in patients with relapsing MS (RMS) and primary progressive MS (PPMS), participating in the OPERA I/II (NCT01247324/NCT01412333) and ORATORIO (NCT01194570) Phase III trials, respectively.

Methods

At the end of the double-blind controlled treatment period in OPERA I/II, patients entered the open‑label extension (OLE), and either continued to receive OCR (OCR-OCR) or switched from interferon β-1a (IFN β-1a) to OCR (IFN β-1a-OCR). In ORATORIO, patients entered the OLE ~3–9 months after the double-blind period cut-off and either continued OCR (OCR-OCR) or switched from placebo (PBO) to OCR (PBO-OCR). Changes in thalamic volume from the core trial baseline were computed using Jacobian integration and analyzed using a mixed-effect repeated measurement model, adjusted for baseline volume, age, baseline gadolinium-enhancing lesions (presence/absence), baseline T2 lesion volume, region (US vs rest of the world), Expanded Disability Status Scale category (<4, ≥4), week, treatment, treatment and time interaction, and treatment and baseline volume interaction.

Results

In the OLE of OPERA I/II, changes (%) in thalamic volume from baseline at OLE Week 46, 94, 142, 190, and 238, were: –2.88/–2.12 (p<0.001), –3.31/–2.36 (p<0.001), –3.61/–2.78 (p<0.001), –3.68/–3.03 (p<0.001), and –4.07/–3.41 (p<0.001), for IFN β-1a-OCR/OCR-OCR patients, respectively. During the OLE of ORATORIO, changes in thalamic volume at OLE Day 1, Week 48, 96, and 144, were: –3.46/–2.44 (p<0.001), –3.93/–2.61 (p<0.001), –4.30/–3.25 (p<0.001), and –4.86/–3.62 (p<0.001), for PBO-OCR/OCR-OCR patients, respectively.

Conclusions

In the OLE, patients with RMS and PPMS who were initially randomized to ocrelizumab experienced less thalamic volume loss compared with those initiating ocrelizumab later.

Background

A deep-learning prototype method, called CVSNet, was recently introduced for the automated detection of the central vein sign (CVS) in brain lesions and demonstrated effective and accurate discrimination of multiple sclerosis (MS) from its mimics. However, this method solely considered focal lesions displaying the central vein sign (CVS+) or not (CVS−), therefore requiring a manual pre-selection of the lesions to be evaluated by eliminating the so-called excluded lesions (CVSe) as defined by the NAIMS criteria. CVSe lesions may however play an important role in differential diagnosis. Moreover, extending the automated CVS classification to these lesions would facilitate the integration of CVSNet with existing MS lesion segmentation algorithms in a fully automated pipeline.

Objectives

To develop an improved version of the CVSNet prototype method able to classify all types of lesions (CVS+, CVS− and CVSe).

Methods

Patients with an established MS or CIS diagnosis (RRMS 29; SPMS 10; PPMS 10; CIS 1; mean ± SD age: 50 ± 11 years; male/female: 23/27), and healthy controls (n=8; mean ± SD age: 41 ± 9 years; male/female: 5/3), underwent 3T brain MRI (MAGNETOM Skyra and MAGNETOM Prisma, Siemens Healthcare, Erlangen, Germany, or Achieva, Philips Healthcare, Best, Netherlands). Brain lesions were automatically segmented and manually corrected by a single rater. CVS assessment was conducted on FLAIR* images by two raters, according to the NAIMS guidelines, yielding 1542 CVS+, 1004 CVS−, and 1131 CVSe lesions. A convolutional neural network (CNN) based on the CVSnet architecture was trained with different configurations using 3021 samples (1261 CVS+, 847 CVS−, and 913 CVSe) and evaluated in 656 unseen samples (281 CVS+, 157 CVS−, and 218 CVSe, from 13 patients) for final testing. The configurations relied on different combinations of the following channels as input: (i) FLAIR*, (ii) T2*, (iii) lesion mask, and (iv) CSF and brain tissue concentration maps obtained from a partial-volume estimation algorithm. Lesion-wise classification performance was evaluated for the different configurations by estimating the sensitivity, specificity, and accuracy for each lesion class.

Results

The results were similar across the different configurations. The best performance in the unseen testing set was obtained when all channels were used as input (sensitivity: 0.71, 0.73; specificity: 0.71, 0.81; and accuracy: 0.71, 0.79 for CVS+, CVS−, respectively). For CVSe, this approach achieved 0.52 sensitivity, 0.94 specificity, and 0.80 accuracy.

Conclusions

We introduced a modified CVSNet prototype method that can analyze the presence of the central vein for all types of brain lesions, enabling its integration with current MS lesion segmentation algorithms. This new feature will allow a fully automated assessment of the CVS in patients’ brains, speeding up the evaluation of CVS as a diagnostic biomarker for differentiating MS from mimicking diseases.

Background

Masitinib (MAS) is a small molecule drug targeting KIT, LYN and CSF1R. Proof-of-concept that MAS slows progressive multiple sclerosis (MS) was previously demonstrated.

Objectives

Assessment of oral MAS as a treatment for progressive MS. Study AB07002 (NCT01433497) evaluated 2 independent parallel groups; 4.5 mg/kg/d vs matched placebo (PBO), and titrated MAS dose of 6.0 mg/kg/d vs PBO.

Methods

Randomized (2:1), double-blinded, placebo-controlled, 2-parallel group trial. Eligible patients (pts) aged 18­–75 years, with baseline Expanded Disability Status Scale (EDSS) 2.0–6.0, regardless of time-from-onset, and diagnosed with primary progressive (PPMS) or non-active secondary progressive (nSPMS) MS, were treated for 96 weeks. Primary endpoint was overall EDSS change from baseline using repeated measures (GEE model, timeframe W12–W96, measured every 12 weeks). Results are expressed as least-squares means difference (δEDSS, positive value indicates worsening), with treatment-effect reported as between-group difference (ΔLSM, negative value favors MAS). A key sensitivity analysis was the 3-level ordinal EDSS model (±1 or 0, repeated measures), which simultaneously measures improved, stable, or worsening outcomes over duration of treatment.

Results

MAS (4.5mg/kg/d) (n=199, median EDSS=5.5, mean age=49.3±9.6 years) showed significant benefit over PBO (n=101) with δEDSS of 0.001 vs 0.098, respectively, and ΔLSM of -0.097(95%CI[-0.192,-0.002]);p=0.0256. This treatment-effect was numerically maintained for the subgroups of nSPMS (MAS n=120 vs 56) and PPMS (MAS n=79 vs 45) with ΔLSM of -0.104(95%CI[-0.198,-0.008]; p=0.032) and -0.128(95%CI [-0.285,0.0282];p=0.108), respectively. All EDSS sensitivity analyses were convergent with the primary outcome, including the conservative jump-to-reference approach with ΔLSM of -0.089 (95%CI[-0.173,-0.006];p=0.0367). Ordinal EDSS analysis showed a significant 39% relative probability of either reduction in EDSS progression or increase in EDSS improvement (hazard ratio (HR) 0.610 (95%CI[0.376,0.988];p=0·0446). Analysis of EDSS time-to-progression showed a significant reduced relative risk of 42% with MAS for first progression (HR 0.58, 95%CI[0.35,0.96];p=0.034), and a reduced relative risk of 37% with MAS for 12-week confirmed (HR 0.63, 95%CI[0.33,1.20];p=0.159). The proportion of pts presenting at least one adverse event (AE) was 94.5% for MAS (4.5 mg/kg/d) vs 87.1% for PBO. Safety was consistent with the known profile for MAS, common treatment-emergent AEs being diarrhea, nausea, rash, and hematological assessments. Efficacy results from the MAS high-dose parallel group (titrated 6.0 mg/kg/d) were inconclusive and no new safety signal was observed.

Conclusions

MAS (4.5 mg/kg/d), a first-in-class TKI targeting the innate immune system via inhibition of mast cell and microglia/macrophage activity, may provide a new treatment option for PPMS and nSPMS

Background

Obesity is increasingly recognized as a risk for multiple sclerosis (MS). While the underlying mechanisms remain undetermined, reduced vitamin D bioavailability and altered levels of the immunomodulatory cytokines adiponectin and leptin have been proposed.

Objectives

To determine the roles of vitamin D, adiponectin and leptin levels in explaining the effect of obesity on MS, using a Mendelian randomization (MR) mediation framework.

Methods

Independent genetic estimates for body mass index (BMI), 25-hydroxyvitamin D (25OHD), adiponectin and leptin levels were obtained from from large-scale genome-wide association studies and the UK Biobank, totalling over 800,000 participants. The effect on MS was measured using summary genetic data on 14,802 MS cases and 26,703 controls from the International MS Genetics Consortium (IMSGC). To avoid bias from population stratification, all participants were of European ancestry. We estimated the odds of MS for each of the exposures, and the proportion of the effect of BMI explained by potential mediators significantly associated with MS, using the product of coefficients method in a two-step MR framework.

Results

Each standard deviation (SD) increase in BMI was associated with a 40% increase in the odds of MS (95% CI 1.16 to 1.67, P=3.1x10^-4). Similarly, a SD increase in standardized log transformed 25OHD levels reduced the odds of MS by 28% (95% CI 0.60-0.87, P=6.2x10^-4). In contrast, we observed no notable effect of adiponectin (OR=1.05, 95% CI 0.74-1.49, P=0.78) or leptin (OR=1.18, 95% CI 0.59-2.36, P=0.64) on the odds of MS. In MR mediation analysis, we estimate that the reduction in 25OHD levels only explains 5.4% of the effect of increased BMI on the risk of MS (95% CI 0.4% to 30.5%). Sensitivity analyses showed that these estimates were robust to potential bias from pleiotropy.

Conclusions

This study found that only a minority of the increased risk of MS conferred by obesity is mediated by lowered vitamin D levels, while leptin and adiponectin had no measurable effect. This suggests that vitamin D supplementation would only modestly reverse the effect of obesity on MS, the majority of which remains unexplained.