Summary: Lower serum levels of the sugar metabolite GlcNAc was associated with progressive disability and neurodegeneration in patients with multiple sclerosis.

Source: UC Irvine

A new University of California, Irvine-led study finds low serum levels of the sugar N-acetylglucosamine (GlcNAc), is associated with progressive disability and neurodegeneration in multiple sclerosis (MS).

The study, done in collaboration with researchers from Charité – Universitätsmedizin Berlin, Germany, and the University of Toronto, Canada, is titled, “Association of a Marker of N-Acetylglucosamine With Progressive Multiple Sclerosis and Neurodegeneration,” The study was published this week in JAMA Neurology.

The study suggests that GlcNAc, which has been previously shown to promote re-myelination and suppress neurodegeneration in animal models of MS, is reduced in serum of progressive MS patients and those with worse clinical disability and neurodegeneration.

“We found the serum levels of a marker of GlcNAc was markedly reduced in progressive MS patients compared to healthy controls and patients with relapsing-remitting multiple sclerosis” explained Michael Demetriou, MD, PhD, FRCP(C), professor of neurology, microbiology and molecular genetics at UCI School of Medicine, and senior author on the paper.

First author of the study, Alexander Brandt, MD, adjunct associate professor of neurology at the UCI School of Medicine and previously associated with the Experimental and Clinical Research Center, Charité – Universitätsmedizin Berlin and Max Delbrueck Center for Molecular Medicine, Germany, added, “Lower GlcNAc serum marker levels correlated with multiple measures of neurodegeneration in MS, namely worse expanded disability status scale scores, lower thalamic volume, and thinner retinal nerve fiber layer. Also, low baseline serum levels correlated with a greater percentage of brain volume loss at 18 months,” he said.

GlcNAc regulates protein glycosylation, a fundamental process that decorates the surface of all cells with complex sugars. Previous preclinical, human genetic and ex vivo human mechanistic studies revealed that GlcNAc reduces proinflammatory immune responses, promotes myelin repair, and decreases neurodegeneration.

GlcNAc regulates protein glycosylation, a fundamental process that decorates the surface of all cells with complex sugars. Image is in the public domain

Combined with the new findings, the data suggest that GlcNAc deficiency may promote progressive disease and neurodegeneration in patients with MS. However, additional human clinical studies are required to confirm this hypothesis.

“Our findings open new potential avenues to identify patients at risk of disease progression and neurodegeneration, so clinicians can develop and adjust therapies accordingly,” said Michael Sy, MD, PhD, assistant professor in residence in the Department of Neurology at UCI and a co-author of the study.

MS is characterized by recurrent episodes of neurologic dysfunction resulting from acute inflammatory demyelination. Progressive MS is distinguished by continuous inflammation, failure to remyelinate, and progressive neurodegeneration, causing accrual of irreversible neurologic disability.

Neurodegeneration is the major contributor to progressive neurological disability in MS patients, yet mechanisms are poorly understood and there are no current treatments for neurodegeneration.

Funding: This study was funded in part by a grant from the National Institute of Allergy and Infectious Disease and the National Center for Complimentary and Integrative Health as well as the Excellence Initiative and the Excellence Strategy of the German Federal and State Governments.

About this multiple sclerosis research news

Source: UC Irvine
Contact: Anne Warde – UC Irvine
Image: The image is in the public domain

Original Research: Open access.
“Association of a Marker of N-Acetylglucosamine With Progressive Multiple Sclerosis and Neurodegeneration” by Michael Demetriou et al. JAMA Neurology


Abstract

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Association of a Marker of N-Acetylglucosamine With Progressive Multiple Sclerosis and Neurodegeneration

Importance  N-glycan branching modulates cell surface receptor availability, and its deficiency in mice promotes inflammatory demyelination, reduced myelination, and neurodegeneration. N-acetylglucosamine (GlcNAc) is a rate-limiting substrate for N-glycan branching, but, to our knowledge, endogenous serum levels in patients with multiple sclerosis (MS) are unknown.

Objective  To investigate a marker of endogenous serum GlcNAc levels in patients with MS.

Design, Setting, and Participants  A cross-sectional discovery study and cross-sectional confirmatory study were conducted at 2 academic MS centers in the US and Germany. The discovery study recruited 54 patients with MS from an outpatient clinic as well as 66 healthy controls between April 20, 2010, and June 21, 2013. The confirmatory study recruited 180 patients with MS from screening visits at an academic MS study center between April 9, 2007, and February 29, 2016. Serum samples were analyzed from December 2, 2013, to March 2, 2015. Statistical analysis was performed from February 23, 2020, to March 18, 2021.

Main Outcomes and Measures  Serum levels of GlcNAc plus its stereoisomers, termed N-acetylhexosamine (HexNAc), were assessed using targeted tandem mass spectroscopy. Secondary outcomes (confirmatory study) comprised imaging and clinical disease markers.

Results  The discovery cohort included 66 healthy controls (38 women; mean [SD] age, 42 [20] years), 33 patients with relapsing-remitting MS (RRMS; 25 women; mean [SD] age, 50 [11] years), and 21 patients with progressive MS (PMS; 14 women; mean [SD] age, 55 [7] years). The confirmatory cohort included 125 patients with RRMS (83 women; mean [SD] age, 40 [9] years) and 55 patients with PMS (22 women; mean [SD] age, 49 [80] years). In the discovery cohort, the mean (SD) serum level of GlcNAc plus its stereoisomers (HexNAc) was 710 (174) nM in healthy controls and marginally reduced in patients with RRMS (mean [SD] level, 682 [173] nM; P = .04), whereas patients with PMS displayed markedly reduced levels compared with healthy controls (mean [SD] level, 548 [101] nM; P = 9.55 × 10−9) and patients with RRMS (P = 1.83 × 10−4). The difference between patients with RRMS (mean [SD] level, 709 [193] nM) and those with PMS (mean [SD] level, 405 [161] nM; P = 7.6 × 10−18) was confirmed in the independent confirmatory cohort. Lower HexNAc serum levels correlated with worse expanded disability status scale scores (ρ = –0.485; P = 4.73 × 10−12), lower thalamic volume (t = 1.7; P = .04), and thinner retinal nerve fiber layer (B = 0.012 [SE = 7.5 × 10−11]; P = .008). Low baseline serum HexNAc levels correlated with a greater percentage of brain volume loss at 18 months (t = 1.8; P = .04).

Conclusions and Relevance  This study suggests that deficiency of GlcNAc plus its stereoisomers (HexNAc) may be a biomarker for PMS. Previous preclinical, human genetic, and ex vivo human mechanistic studies revealed that N-glycan branching and/or GlcNAc may reduce proinflammatory responses, promote myelin repair, and decrease neurodegeneration. Combined, the data suggest that GlcNAc deficiency may be associated with progressive disease and neurodegeneration in patients with MS.



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