Experimental and Clinical Research Center, Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, and Max Delbrück Center for Molecular Medicine, Berlin, Germany.
Department of Neurology, University of California, Irvine, Irvine.
JAMA Neurol. 2021 Jul 1;78(7):842-852. doi: 10.1001/jamaneurol.2021.1116.
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.
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.
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.
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).
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.
重要性：N-糖基化分支调节细胞表面受体的可用性，其在小鼠中的缺乏会促进炎症性脱髓鞘、髓鞘形成减少和神经退行性变。N-乙酰葡萄糖胺（GlcNAc）是 N-糖基化分支的限速底物，但据我们所知，多发性硬化症（MS）患者的内源性血清水平尚不清楚。
目的：研究多发性硬化症患者内源性血清 GlcNAc 水平的标志物。
设计、地点和参与者：本研究在美国和德国的 2 个学术 MS 中心进行了一项横断面发现研究和一项横断面验证性研究。发现研究招募了 54 名门诊多发性硬化症患者和 66 名健康对照者，时间为 2010 年 4 月 20 日至 6 月 21 日。验证性研究招募了 180 名来自学术 MS 研究中心筛查就诊的多发性硬化症患者，时间为 2007 年 4 月 9 日至 2016 年 2 月 29 日。血清样本于 2013 年 12 月 2 日至 2015 年 3 月 2 日进行分析。统计分析于 2021 年 3 月 18 日进行。
主要结果和措施：使用靶向串联质谱法评估 GlcNAc 及其立体异构体（N-乙酰己糖胺（HexNAc））的血清水平。次要结果（验证性研究）包括成像和临床疾病标志物。
结果：发现队列包括 66 名健康对照者（38 名女性；平均[标准差]年龄 42[20]岁）、33 名复发缓解型多发性硬化症（RRMS；25 名女性；平均[标准差]年龄 50[11]岁）和 21 名进展型多发性硬化症（PMS；14 名女性；平均[标准差]年龄 55[7]岁）。验证性队列包括 125 名 RRMS 患者（83 名女性；平均[标准差]年龄 40[9]岁）和 55 名 PMS 患者（22 名女性；平均[标准差]年龄 49[80]岁）。在发现队列中，健康对照组的血清 GlcNAc 及其立体异构体（HexNAc）平均（标准差）水平为 710（174）nM，RRMS 患者的水平略有降低（平均[标准差]水平 682[173]nM；P=0.04），而 PMS 患者的水平明显降低，与健康对照组相比（平均[标准差]水平 548[101]nM；P=9.55×10-9）和 RRMS 患者相比（P=1.83×10-4）。RRMS 患者（平均[标准差]水平 709[193]nM）和 PMS 患者（平均[标准差]水平 405[161]nM；P=7.6×10-18）之间的差异在独立的验证性队列中得到了证实。较低的 HexNAc 血清水平与扩展残疾状况量表评分较差相关（ρ=-0.485；P=4.73×10-12）、丘脑体积较小（t=1.7；P=0.04）和视网膜神经纤维层较薄（B=0.012[SE=7.5×10-11]；P=0.008）。基线血清 HexNAc 水平较低与 18 个月时脑容量损失百分比增加相关（t=1.8；P=0.04）。
结论和相关性：本研究表明，GlcNAc 及其立体异构体（HexNAc）的缺乏可能是 PMS 的生物标志物。先前的临床前、人类遗传学和体外人类机制研究表明，N-糖基化分支和/或 GlcNAc 可能减少促炎反应，促进髓鞘修复，并减少神经退行性变。综合来看，这些数据表明 GlcNAc 缺乏可能与 MS 患者的进行性疾病和神经退行性变有关。
