Vitamin B-12 deficiency stimulates osteoclastogenesis via increased homocysteine and methylmalonic acid

The risk of nutrient deficiencies increases with age in our modern Western society, and vitamin B(12) deficiency is especially prevalent in the elderly and causes increased homocysteine (Hcy) and methylmalonic acid (MMA) levels. These three factors have been recognized as risk factors for reduced bone mineral density and increased fracture risk, though mechanistic evidence is still lacking. In the present study, we investigated the influence of B(12), Hcy, and MMA on differentiation and activity of bone cells. B(12) deficiency did not affect the onset of osteoblast differentiation, maturation, matrix mineralization, or adipocyte differentiation from human mesenchymal stem cells (hMSCs). B(12) deficiency caused an increase in the secretion of Hcy and MMA into the culture medium by osteoblasts, but Hcy and MMA appeared to have no effect on hMSC osteoblast differentiation. We further studied the effect of B(12), Hcy, and MMA on the formation of multinucleated tartrate-resistant acid phosphatase-positive osteoclasts from mouse bone marrow. We observed that B(12) did not show an effect on osteoclastogenesis. However, Hcy as well as MMA were found to induce osteoclastogenesis in a dose-dependent manner. On the basis of these results, we conclude that B(12) deficiency may lead to decreased bone mass by increased osteoclast formation due to increased MMA and Hcy levels

Identification of novel regulators associated with early-phase osteoblast differentiation.

Item does not contain fulltextKey regulatory components of the BMP-induced osteoblast differentiation cascade remain to be established. Microarray and subsequent expression analyses in mice identified two transcription factors, Hey1 and Tcf7, with in vitro and in vivo expression characteristics very similar to Cbfa1. Transfection studies suggest that Tcf7 modulates BMP2-induced osteoblast differentiation. This study contributes to a better definition of the onset of BMP-induced osteoblast differentiation. INTRODUCTION: Elucidation of the genetic cascade guiding mesenchymal stem cells to become osteoblasts is of extreme importance for improving the treatment of bone-related diseases such as osteoporosis. The aim of this study was to identify regulators of the early phases of bone morphogenetic protein (BMP)2-induced osteoblast differentiation. MATERIALS AND METHODS: Osteoblast differentiation of mouse C2C12 cells was induced by treatment with BMP2, and regulation of gene expression was studied during the subsequent 24 h using high-density microarrays. The regulated genes were grouped by means of model-based clustering, and protein functions were assigned. Real-time quantitative RT-PCR analysis was used to validate BMP2-induced gene expression patterns in C2C12 cells. Osteoblast specificity was studied by comparing these expression patterns with those in C3H10T1/2 and NIH3T3 cells under similar conditions. In situ hybridization of mRNA in embryos at embryonic day (E)14.5 and E16.5 of gestation and on newborn mouse tails were used to study in vivo expression patterns. Cells constitutively expressing the regulated gene Tcf7 were used to investigate its influence on BMP-induced osteoblast differentiation. RESULTS AND CONCLUSIONS: A total of 184 genes and expressed sequence tags (ESTs) were differentially expressed in the first 24 h after BMP2 treatment and grouped in subsets of immediate early, intermediate early, and late early response genes. Signal transduction regulatory factors mainly represented the subset of immediate early genes. Regulation of expression of these genes was direct, independent of de novo protein synthesis and independent of the cell type studied. The intermediate early and late early genes consisted primarily of genes related to processes that modulate morphology, basement membrane formation, and synthesis of extracellular calcified matrix. The late early genes require de novo protein synthesis and show osteoblast specificity. In vivo and in vitro experiments showed that the transcription factors Hey1 and Tcf7 exhibited expression characteristics and cell type specificity very similar to those of the osteoblast specific transcription factor Cbfa1, and constitutive expression of Tcf7 in C2C12 cells differentially regulated osteoblast differentiation marker genes

Recovery from COVID-19:a sprint or marathon? 6-month follow-up data from online long COVID-19 support group members

Background: It remains unknown whether and to what extent members of online "long COVID" peer support groups remain symptomatic and limited over time. Therefore, we aimed to evaluate symptoms in members of online long COVID peer support groups up to 6 months after the onset of coronavirus disease 2019 (COVID-19)-related symptoms.Methods: Demographics, symptoms, health status, work productivity, functional status and health-related quality of life were assessed about 3 and 6 months after the onset of COVID-19-related symptoms in members of online long COVID peer support groups.Results: Data from 239 patients with a confirmed COVID-19 diagnosis (83% women; median (interquartile range) age 50 (39-56) years) were analysed. During the infection, a median (interquartile range) of 15 (11-18) symptoms was reported, which was significantly lower 3 and 6 months later: 6 (4-9) and 6 (3-8), respectively (p&lt;0.05). From 3 to 6 months follow-up, the proportion of patients without symptoms increased from 1.3% to only 5.4% (p&lt;0.001). Patients also reported a significantly improved work productivity (work absenteeism and presenteeism: 73% versus 52% and 66% versus 60%, respectively), self-reported good health (9.2% versus 16.7%), functional status (mean±sd Post-COVID-19 Functional Status scale: 2.4±0.9 versus 2.2±1.0) and health-related quality of life (all p&lt;0.05).Conclusion: Although patients with confirmed COVID-19, who were all members of online long COVID peer support groups, reported significant improvements in work productivity, functional status and quality of life between 3 and 6 months follow-up, these data clearly highlight the long-term impact of COVID-19, as approximately 6 months after the onset of COVID-19-related symptoms a large proportion still experienced persistent symptoms, a moderate-to-poor health, moderate-to-severe functional limitations, considerable loss in work productivity, and/or an impaired quality of life. Action is needed to improve the management and healthcare of these patients.</p