Patzel Katherine A, Yardeni Tal, Le Poëc-Celic Erell, Leoyklang Petcharat, Dorward Heidi, Alonzi Dominic S, Kukushkin Nikolay V, Xu Bixue, Zhang Yongmin, Sollogoub Matthieu, Blériot Yves, Gahl William A, Huizing Marjan, Butters Terry D
Oxford Glycobiology Institute, Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK.
J Inherit Metab Dis. 2014 Mar;37(2):297-308. doi: 10.1007/s10545-013-9655-6. Epub 2013 Oct 18.
UDP-GlcNAc 2-epimerase/ManNAc 6-kinase (GNE) is a bifunctional enzyme responsible for the first committed steps in the synthesis of sialic acid, a common terminal monosaccharide in both protein and lipid glycosylation. GNE mutations are responsible for a rare autosomal recessive neuromuscular disorder, GNE myopathy (also called hereditary inclusion body myopathy). The connection between the impairment of sialic acid synthesis and muscle pathology in GNE myopathy remains poorly understood.
Glycosphingolipid (GSL) analysis was performed by HPLC in multiple models of GNE myopathy, including patients' fibroblasts and plasma, control fibroblasts with inhibited GNE epimerase activity through a novel imino sugar, and tissues of Gne(M712T/M712T) knock-in mice.
Not only neutral GSLs, but also sialylated GSLs, were significantly increased compared to controls in all tested models of GNE myopathy. Treatment of GNE myopathy fibroblasts with N-acetylmannosamine (ManNAc), a sialic acid precursor downstream of GNE epimerase activity, ameliorated the increased total GSL concentrations.
GNE myopathy models have increased total GSL concentrations. ManNAc supplementation results in decrease of GSL levels, linking abnormal increase of total GSLs in GNE myopathy to defects in the sialic acid biosynthetic pathway. These data advocate for further exploring GSL concentrations as an informative biomarker, not only for GNE myopathy, but also for other disorders of sialic acid metabolism.
UDP-N-乙酰葡糖胺2-表异构酶/甘露糖胺6-激酶（GNE）是一种双功能酶，负责唾液酸合成的首个关键步骤，唾液酸是蛋白质和脂质糖基化中常见的末端单糖。GNE突变导致一种罕见的常染色体隐性神经肌肉疾病，即GNE肌病（也称为遗传性包涵体肌病）。GNE肌病中唾液酸合成受损与肌肉病理之间的联系仍知之甚少。
通过高效液相色谱法对多种GNE肌病模型进行糖鞘脂（GSL）分析，包括患者的成纤维细胞和血浆、通过一种新型亚氨基糖抑制GNE表异构酶活性的对照成纤维细胞，以及Gne（M712T/M712T）基因敲入小鼠的组织。
在所有测试的GNE肌病模型中，与对照相比，不仅中性GSL，而且唾液酸化GSL均显著增加。用N-乙酰甘露糖胺（ManNAc）（GNE表异构酶活性下游的一种唾液酸前体）处理GNE肌病成纤维细胞，可改善总GSL浓度的增加。
GNE肌病模型中总GSL浓度增加。补充ManNAc可降低GSL水平，将GNE肌病中总GSL的异常增加与唾液酸生物合成途径的缺陷联系起来。这些数据支持进一步探索GSL浓度作为一种有价值的生物标志物，不仅用于GNE肌病，也用于其他唾液酸代谢紊乱疾病。
