title: Diabetic osteopenia by decreased β-catenin signaling is partly induced by epigenetic derepression of sFRP-4 gene.
abstract: In diabetics, methylglyoxal (MG), a glucose-derived metabolite, plays a noxious role by inducing oxidative stress, which causes and exacerbates a series of complications including low-turnover osteoporosis. In the present study, while MG treatment of mouse bone marrow stroma-derived ST2 cells rapidly suppressed the expression of osteotrophic Wnt-targeted genes, including that of osteoprotegerin (OPG, a decoy receptor of the receptor activator of NF-kappaB ligand (RANKL)), it significantly enhanced that of secreted Frizzled-related protein 4 (sFRP-4, a soluble inhibitor of Wnts). On the assumption that upregulated sFRP-4 is a trigger that downregulates Wnt-related genes, we sought out the molecular mechanism whereby oxidative stress enhanced the sFRP-4 gene. Sodium bisulfite sequencing revealed that the sFRP-4 gene was highly methylated around the sFRP-4 gene basic promoter region, but was not altered by MG treatment. Electrophoretic gel motility shift assay showed that two continuous CpG loci located five bases upstream of the TATA-box were, when methylated, a target of methyl CpG binding protein 2 (MeCP2) that was sequestered upon induction of 8-hydroxy-2-deoxyguanosine, a biomarker of oxidative damage to DNA. These in vitro data suggest that MG-derived oxidative stress (not CpG demethylation) epigenetically and rapidly derepress sFRP-4 gene expression. We speculate that under persistent oxidative stress, as in diabetes and during aging, osteopenia and ultimately low-turnover osteoporosis become evident partly due to osteoblastic inactivation by suppressed Wnt signaling of mainly canonical pathways through the derepression of sFRP-4 gene expression.
authors.affiliation: Department of Pathology, Division of Diagnostic Molecular Pathology, Kobe University Graduate School of Medicine, Kobe City, Japan; Department of Pathology, National Hospital Organization, Osaka National Hospital, Hoenzaka, Chuo-ku, Osaka City, Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Mori
authors.affiliation: Department of Pathology, Division of Diagnostic Molecular Pathology, Kobe University Graduate School of Medicine, Kobe City, Japan; Department of Molecular Pathology, Ehime University Graduate School of Medicine, Shitsukawa, Toon City, Ehime, Japan; Department of Diagnostic Pathology, Ehime University Hospital, Shitsukawa, Toon City, Ehime, Japan.
authors.forename: Riko
authors.initials: R
authors.lastname: Kitazawa
authors.affiliation: Department of Pathology, Division of Diagnostic Molecular Pathology, Kobe University Graduate School of Medicine, Kobe City, Japan; Department of Legal Medicine, Kobe University Graduate School of Medicine, Kobe City, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kondo
authors.affiliation: Department of Pathology, Division of Diagnostic Molecular Pathology, Kobe University Graduate School of Medicine, Kobe City, Japan.
authors.forename: Michiko
authors.initials: M
authors.lastname: Mori
authors.affiliation: Department of Therapeutic Nutrition, Institute of Health Bioscience, The University of Tokushima, Tokushima City, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Hamada
authors.affiliation: Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe City, Japan.
authors.forename: Michiru
authors.initials: M
authors.lastname: Nishida
authors.affiliation: Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe City, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Minami
authors.affiliation: Department of Diagnostic Pathology, Ehime University Hospital, Shitsukawa, Toon City, Ehime, Japan.
authors.forename: Ryuma
authors.initials: R
authors.lastname: Haraguchi
authors.affiliation: Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe City, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Takahashi
authors.affiliation: Department of Pathology, Division of Diagnostic Molecular Pathology, Kobe University Graduate School of Medicine, Kobe City, Japan; Department of Molecular Pathology, Ehime University Graduate School of Medicine, Shitsukawa, Toon City, Ehime, Japan; Department of Diagnostic Pathology, Ehime University Hospital, Shitsukawa, Toon City, Ehime, Japan.
authors.forename: Sohei
authors.initials: S
authors.lastname: Kitazawa
mesh_terms: D000818:Animals; D001851:Bone Diseases, Metabolic / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D019175:DNA Methylation / Q000235:genetics; D003920:Diabetes Mellitus / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation / Q000235:genetics; D044127:Epigenesis, Genetic / Q000235:genetics*; D057890:Epigenomics / Q000379:methods; D015870:Gene Expression / Q000235:genetics; D059630:Mesenchymal Stem Cells / Q000378:metabolism; D051783:Methyl-CpG-Binding Protein 2 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018384:Oxidative Stress / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics* / Q000378:metabolism; D011765:Pyruvaldehyde / Q000378:metabolism; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics*; D015854:Up-Regulation / Q000235:genetics; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism; D051176:beta Catenin / Q000235:genetics* / Q000378:metabolism; D000094742:Secreted Frizzled-Related Proteins
chemical_list: D051783:Methyl-CpG-Binding Protein 2; D011518:Proto-Oncogene Proteins; D011765:Pyruvaldehyde; D053246:Receptor Activator of Nuclear Factor-kappa B; D051153:Wnt Proteins; D051176:beta Catenin; C497393:Mecp2 protein, mouse; C498454:Sfrp4 protein, mouse; D000094742:Secreted Frizzled-Related Proteins