Peracetylated N-Acetylmannosamine, a Synthetic Sugar Molecule, Efficiently Rescues Muscle Phenotype and Biochemical Defects in Mouse Model of Sialic Acid-deficient Myopathy

May Christine V Malicdan,Satoru Noguchi,Tomoharu Tokutomi,Yu-Ichi Goto,Ikuya Nonaka,Yukiko K Hayashi,Ichizo Nishino

doi:10.1074/jbc.m111.297051

Abstract

Distal myopathy with rimmed vacuoles/hereditary inclusion body myopathy (DMRV/hIBM), characterized by progressive muscle atrophy, weakness, and degeneration, is due to mutations in GNE, a gene encoding a bifunctional enzyme critical in sialic acid biosynthesis. In the DMRV/hIBM mouse model, which exhibits hyposialylation in various tissues in addition to muscle atrophy, weakness, and degeneration, we recently have demonstrated that the myopathic phenotype was prevented by oral administration of N-acetylneuraminic acid, N-acetylmannosamine, and sialyllactose, underscoring the crucial role of hyposialylation in the disease pathomechanism. The choice for the preferred molecule, however, was limited probably by the complex pharmacokinetics of sialic acids and the lack of biomarkers that could clearly show dose response. To address these issues, we screened several synthetic sugar compounds that could increase sialylation more remarkably and allow demonstration of measurable effects in the DMRV/hIBM mice. In this study, we found that tetra-O-acetylated N-acetylmannosamine increased cell sialylation most efficiently, and in vivo evaluation in DMRV/hIBM mice revealed a more dramatic, measurable effect and improvement in muscle phenotype, enabling us to establish analysis of protein biomarkers that can be used for assessing response to treatment. Our results provide a proof of concept in sialic acid-related molecular therapy with synthetic monosaccharides.

Highlights

Distal myopathy with rimmed vacuoles/hereditary inclusion body myopathy (DMRV)/hIBM is a sialic aciddeficient myopathy
Screening of Peracetylated Monosaccharides to Increase Cellular Sialylation in DMRV/hIBM Myocytes—We examined the effect of three synthetic peracetylated ManNAc and N-acetylneuraminic acid (NeuAc) analogs, Ac4ManNAc, Ac5NeuAc, and Ac5NeuAc-Me, on cellular sialylation in DMRV/hIBM patient myocytes
Myotubes obtained from the DMRV/hIBM and that were given GlcNAc as control were strongly stained with soy bean agglutinin lectin, which recognizes peripheral ␤-N-acetylgalactosaminide structure, and faintly stained with wheat germ agglutinin lectin, which recognizes a cluster of sialic acids; this pattern of staining reflects hyposialylation of cells

Summary

Background

Distal myopathy with rimmed vacuoles/hereditary inclusion body myopathy (DMRV)/hIBM is a sialic aciddeficient myopathy. The choice for the preferred molecule, was limited probably by the complex pharmacokinetics of sialic acids and the lack of biomarkers that could clearly show dose response To address these issues, we screened several synthetic sugar compounds that could increase sialylation more remarkably and allow demonstration of measurable effects in the DMRV/hIBM mice. We could not clearly define the dose effect with ManNAc, which should be expected in establishing therapeutic protocols As related to this finding, we have shown that the sialic acid levels in plasma and the organs were not fully recovered, giving rise to some speculations that these results may reflect a limitation in the incorporation of such compounds into mouse tissues because of the rapid excretion of sialic acid metabolites or the absence of definitive markers that could show dose response. When applied in vivo to DMRV/hIBM mice, this compound can prevent the myopathic phenotype in a dosedependent fashion, providing evidence that synthetic sugar compounds may be a good option to consider in designing therapeutic trials pending complete toxicology studies

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION