University of California San Francisco
Neurology

Author Of 2 Presentations

Epidemiology Oral Presentation

FC04.05 - Understanding the relative contributions of obesity, vitamin D, leptin and adiponectin to MS risk: a Mendelian randomization mediation analysis

Speakers
Presentation Number
FC04.05
Presentation Topic
Epidemiology
Lecture Time
13:48 - 14:00

Abstract

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.

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Microbiome Oral Presentation

PS10.05 - Gut dysbiosis in neuromyelitis optica promotes CNS autoimmunity

Speakers
Presentation Number
PS10.05
Presentation Topic
Microbiome
Lecture Time
10:09 - 10:21

Abstract

Background

Neuromyelitis optica (NMO) is a severe demyelinating disease of the central nervous system (CNS) causing irreversible neurological damage. Initial analyses of gut microbiota in NMO, multiple sclerosis and healthy controls (HHC) revealed dysbiosis in the NMO group, suggesting that the gut microbiome may regulate inflammatory responses

Objectives

We hypothesized that gut microbiota from NMO patients may participate and promote inflammatory responses in NMO pathogenesis.

Methods

Wild-type (WT) C57BL/6 germ-free mice were colonized with fecal samples from one untreated NMO patient (n = 10), one household HC (HHC) (n = 9) or vehicle (n = 13) for five weeks and then examined for susceptibility to MOG p35-55-induced experimental autoimmune encephalomyelitis (EAE) for 30 days post immunization. Upon termination of the study, lymphocytes from spleen, lamina propria of small (LP-SI) and large (LP-LI) intestine, mesenteric lymph nodes (MLN), Peyer’s patches (PP), brain, and spinal cord were examined for the expression of IL-17, IFN-γ, Foxp3, CD25, RORγt and Helios.

Results

In comparison to the mean EAE score of the vehicle group (1.9 ± 0.3), severity was greater (p ≤ 0.01) in mice colonized with fecal microbiota from NMO (3.1 ± 0.8) and HHC (2.7 ± 0.7). The mean clinical score of mice colonized with NMO gut microbiota was significantly greater than mice colonized with gut microbiota from HHC or vehicle (p ≤ 0.001). The frequency of CD4+Foxp3+CD25+ cells was decreased in LP-SI, LP-LI, PP and MLN compartments in NMO and HHC compared with vehicle group (p ≤ 0.01). CD4+Foxp3+Helios+ (another regulatory T cell subpopulation) was significantly decreased in MLN and LP-SI of NMO and HHC compared to vehicle group (P ≤ 0.01).

Conclusions

Our data suggest that NMO fecal microbiota increases EAE susceptibility. Reduction in frequency of Tregs in the gut of mice colonized with NMO fecal material may contribute to EAE exacerbation. Further analysis of microbiota and lymphocyte populations in mice colonized with fecal material from NMO and HHC samples are needed. Results from our ongoing study should provide valuable insight regarding the potential role of gut microbiota in NMO.

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Author Of 2 Presentations

Biomarkers and Bioinformatics Poster Presentation

P0063 - Development of a Custom Multivariate Proteomic Serum Based Assay for Association with Radiographic and Clinical Endpoints in MS (ID 833)

Abstract

Background

Multiple Sclerosis (MS) is a complex and heterogeneous disease. Investigating the biological pathways and cell types involved in MS pathophysiology as represented by protein biomarker expression can help inform the development of tools to monitor disease activity, disease progression, identify early evidence of relapse, and monitor treatment response.

Objectives

To develop a blood based multiplex proteomic assay that associates with clinical and radiographic endpoints in patients with MS. These endpoints include the presence of gadolinium-enhanced (Gd+) lesions, Annualized Relapse Rate (ARR) and clinically defined relapse status (active versus stable).

Methods

Serum samples (n=690 in total) from multiple deeply-phenotyped cohorts (ACP, CLIMB and EPIC) were tested in immunoassays for the measurement of 1196 proteins using Proximity Extension Assays (PEA) from OlinkTM and for 215 proteins using xMAPTM immunoassays from Myriad RBM, Inc. (RBM). Associated radiographic and clinical endpoints at the time of the blood draw were correlated with the protein levels. Twenty-one proteins were selected for inclusion in a custom assay based on their performance in univariate and multivariate statistical models, and replication across independent cohorts. Biological pathway modeling and network analysis were performed to ensure comprehensive representation of MS neurophysiology. Area under the curve (AUC) was selected as the key metric for model performance evaluation.

Results

Multivariate statistical ensembles restricted to the expression levels of the biomarkers selected for the custom assay achieved AUC performance of 0.827 for classification of the presence of Gd+ lesions, 0.802 for classification of clinically defined relapse status, and 0.930 for the classification of patients with Low ARR (≤0.2 relapses) vs High ARR (≥1.0 relapses). A multivariate model utilizing shifts in biomarker expression in longitudinally paired samples achieved the highest observed performance of 0.950 for classification of Gd+ lesion presence. In each case, the multivariate models significantly outperformed (p-value <0.05) the AUC of the highest performing univariate biomarker.

Conclusions

Multivariate models restricted to the 21 selected proteins effectively classified several radiographic and clinical endpoints with stronger performance than any single biomarker. A 21-plex custom assay panel is being developed for further investigation and validation using additional cohorts.

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Microbiome Poster Presentation

P0671 - Exploring the gut microbiome in multiple sclerosis via the international MS Microbiome Study (iMSMS) (ID 1532)

Abstract

Background

The gut microbiota is emerging as a critical regulator of immune responses and appears to play an important role in MS. The International Multiple Sclerosis Microbiome study (iMSMS) is a global collaboration aimed at elucidating the role of commensal gut bacteria in MS by acquiring and analyzing samples from 2000 patients and 2000 household healthy controls.

Objectives

The iMSMS focuses on identifying the microbes, genes and pathways that are involved in MS pathogenesis and on investigating how the microbiome changes response to treatment.

Methods

A total of 576 case and household healthy control pairs were recruited from 7 centers located in the US (West and East coasts), Europe and South America. Stool samples were collected and evaluated by both 16S and shallow whole metagenome shotgun sequencing. Univariate and multivariate linear regression analyses were conducted to understand patterns of variation on gut microbiome.

Results

This is the largest MS microbiome study reported to date. Our results showed a statistically significant difference of beta diversity between MS and healthy controls for the first time in MS. Intriguingly, multiple species of Akkermansia, including the known mucin-degrading bacterium Akkermansia muciniphila, were significantly enriched in untreated MS patients after adjusting for confounding factors, but the difference was not detected in treated MS group versus control. Ruminococcus torques and Eisenbergiella tayi were also among the top significantly enriched bacteria in MS. Inversely, a main butyrate producer, Faecalibacterium prausnitzii, was significantly decreased in the untreated MS group. Functional pathways of L-tryptophan biosynthesis and L-threonine biosynthesis were slightly increased in untreated MS patients, while 5-aminoimidazole ribonucleotide biosynthesis I was increased in the treated group.

Conclusions

Our large household-controlled study allowed us to identify modest but statistically robust MS-associated changes in bacterial composition and functions. It provides the foundation for all future studies of the gut microbiota in MS. The strain-level genomic variation and microbiome-derived molecules need to be further explored for understanding microbial adaptation and pathogenicity.

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