Although rachitic/osteomalacic myopathy caused by impaired vitamin D actions has long been described, the molecular pathogenesis remains elusive. To determine physiological roles of vitamin D actions through vitamin D receptor (VDR) in skeletal muscle development, we examined skeletal muscle in VDR gene deleted (VDR -/-) mice, an animal model of vitamin D-dependent rickets type II, for morphological changes and expression of myoregulatory transcription factors and myosin heavy chain isoforms. We found that each muscle fiber was small and variable in size in hindlimb skeletal muscle from VDR -/- mice, although overall myocyte differentiation occurred normally. These abnormalities were independent of secondary metabolic changes such as hypocalcemia and hypophosphatemia, and were accompanied by aberrantly high and persistent expression of myf5, myogenin, E2A, and early myosin heavy chain isoforms, which are normally down-regulated at earlier stages. Moreover, treatment of VDR-positive myoblastic cells with 1,25(OH)2D3 in vitro caused down-regulation of these factors. These results suggest that VDR plays a physiological role in skeletal muscle development, participating in temporally strict down-regulation of myoregulatory transcription factors. The present study can form a molecular basis of VDR actions on muscle and should help further establish the physiological roles of VDR in muscle development as well as pharmacological effects of vitamin D on muscle functions.

No abstract

Bone marrow stromal cells (BMSCs) and osteoclasts (OCs) confer multiple myeloma (MM) cell survival through elaborating factors. We demonstrate herein that IL-6 and TNF family cytokines, TNFa, BAFF and APRIL, but not IGF-1 cooperatively enhance the expression of the serine/threonine kinase Pim-2 in MM cells. BMSCs and OCs upregulate Pim-2 expression in MM cells largely via the IL-6/STAT3 and NF-jB pathway, respectively. Pim-2 short interfering RNA reduces MM cell viability in cocultures with BMSCs or OCs. Thus, upregulation of Pim-2 appears to be a novel anti-apoptotic mechanism for MM cell survival. Interestingly, the mammalian target of rapamycin inhibitor rapamycin further suppresses the MM cell viability in combination with the Pim-2 silencing. The Pim inhibitor (Z)-5-(4-propoxybenzylidene) thiazolidine-2, 4-dione and the PI3K inhibitor LY294002 cooperatively enhance MM cell death. The Pim inhibitor suppresses 4E-BP1 phosphorylation along with the reduction of Mcl-1 and c-Myc. Pim-2 may therefore become a new target for MM treatment.

FIBROBLAST GROWTH FACTOR 23 (FGF23) is a hormone produced by bone and reduces serum phosphate by inhibiting proximal tubular phosphate reabsorption and intestinal phosphate absorption through decreasing serum 1,25-dihydroxyvitamin D [1]. It has been shown that excessive actions of FGF23 cause several kinds of FGF23-related hypophosphatemic Abstract. A nationwide epidemiologic survey of fibroblast growth factor 23 (FGF23)-related hypophosphatemic diseases was conducted in 2010 to clarify the prevalence and the clinical presentations of the disorders. A questionnaire inquiring the experience of patients with these diseases was sent to randomly selected hospitals throughout Japan. The estimated annual incidence of the diseases was 117 cases (95% CI 75 -160), 55 males (95% CI 30 -81) and 62 females (95% CI 40 -84). Tumor-induced osteomalacia (TIO) and X-linked hypophosphatemic rickets (XLH) were the most prevalent causes of acquired and genetic FGF23-related hypophosphatemic diseases, respectively. The estimated incidence of XLH was about 1 in 20,000. We have also collected clinical data of the patients by a secondary survey. These patients showed FGF23 levels of above 30 pg/mL by intact assay in the presence of hypophosphatemia. While complete resection of responsible tumors improved biochemical abnormalities in patients with TIO, treatment with phosphate and/or active vitamin D 3 did not normalize serum phosphate and tubular maximum transport of phosphate in patients with XLH. Our results suggest that there is no racial difference in the incidence of XLH. While FGF23 measurement is useful for the diagnosis of FGF23-related hypophosphatemic diseases, the better management is necessary especially for patients with genetic hypophosphatemic rickets caused by excessive actions of FGF23.

Aims/Introduction Advanced glycation end‐products (AGEs), which are a major cause of diabetic vascular complications, accumulate in various tissues under chronic hyperglycemic conditions, as well as with aging in patients with diabetes. The loss of muscle mass and strength, so‐called sarcopenia and dynapenia, has recently been recognized as a diabetic complication. However, the influence of accumulated AGEs on muscle mass and strength remains unclear. The present study aimed to evaluate the association of sarcopenia and dynapenia with accumulated AGEs in patients with type 2 diabetes. Materials and Methods We recruited 166 patients with type 2 diabetes aged ≥30 years (mean age 63.2 ± 12.3 years; body mass index 26.3 ± 4.9 kg/m2; glycated hemoglobin 7.1 ± 1.1%). Skin autofluorescence as a marker of AGEs, limb skeletal muscle mass index, grip strength, knee extension strength and gait speed were assessed. Results Sarcopenia and dynapenia were observed in 7.2 and 13.9% of participants, respectively. Skin autofluorescence was significantly higher in patients with sarcopenia and dynapenia. Skin autofluorescence was the independent determinant for skeletal muscle mass index, grip strength, knee extension strength, sarcopenia and dynapenia. Conclusions Accumulated AGEs could contribute to reduced muscle mass and strength, leading to sarcopenia and dynapenia in patients with type 2 diabetes.

Pim-2 kinase is overexpressed in multiple myeloma (MM) cells to enhance their growth and survival, and regarded as a novel therapeutic target in MM. However, the impact of Pim-2 inhibition on bone disease in MM remains unknown. We demonstrated here that Pim-2 expression was also upregulated in bone marrow stromal cells and MC3T3-E1 preosteoblastic cells in the presence of cytokines known as the inhibitors of osteoblastogenesis in MM, including interleukin-3 (IL-3), IL-7, tumor necrosis factor-α, transforming growth factor-β (TGF-β) and activin A, as well as MM cell conditioned media. The enforced expression of Pim-2 abrogated in vitro osteoblastogenesis by BMP-2, which suggested Pim-2 as a negative regulator for osteoblastogenesis. Treatment with Pim-2 short-interference RNA as well as the Pim inhibitor SMI-16a successfully restored osteoblastogenesis suppressed by all the above inhibitory factors and MM cells. The SMI-16a treatment potentiated BMP-2-mediated anabolic signaling while suppressing TGF-β signaling. Furthermore, treatment with the newly synthesized thiazolidine-2,4-dione congener, 12a-OH, as well as its prototypic SMI-16a effectively prevented bone destruction while suppressing MM tumor growth in MM animal models. Thus, Pim-2 may have a pivotal role in tumor progression and bone loss in MM, and Pim-2 inhibition may become an important therapeutic strategy to target the MM cell-bone marrow interaction.

Activating mutations of calcium-sensing receptor (CaSR) cause autosomal dominant hypocalcemia (ADH). ADH patients develop hypocalcemia, hyperphosphatemia, and hypercalciuria, similar to the clinical features of hypoparathyroidism. The current treatment of ADH is similar to the other forms of hypoparathyroidism, using active vitamin D 3 or parathyroid hormone (PTH). However, these treatments aggravate hypercalciuria and renal calcification. Thus, new therapeutic strategies for ADH are needed. Calcilytics are allosteric antagonists of CaSR, and may be effective for the treatment of ADH caused by activating mutations of CaSR. In order to examine the effect of calcilytic JTT-305/MK-5442 on CaSR harboring activating mutations in the extracellular and transmembrane domains in vitro, we first transfected a mutated CaSR gene into HEK cells. JTT-305/MK-5442 suppressed the hypersensitivity to extracellular Ca 2þ of HEK cells transfected with the CaSR gene with activating mutations in the extracellular and transmembrane domains. We then selected two activating mutations locating in the extracellular (C129S) and transmembrane (A843E) domains, and generated two strains of CaSR knock-in mice to build an ADH mouse model. Both mutant mice mimicked almost all the clinical features of human ADH. JTT-305/MK-5442 treatment in vivo increased urinary cAMP excretion, improved serum and urinary calcium and phosphate levels by stimulating endogenous PTH secretion, and prevented renal calcification. In contrast, PTH(1-34) treatment normalized serum calcium and phosphate but could not reduce hypercalciuria or renal calcification. CaSR knock-in mice exhibited low bone turnover due to the deficiency of PTH, and JTT-305/MK-5442 as well as PTH(1-34) increased bone turnover and bone mineral density (BMD) in these mice. These results demonstrate that calcilytics can reverse almost all the phenotypes of ADH including hypercalciuria and renal calcification, and suggest that calcilytics can become a novel therapeutic agent for ADH.

A case of POEMSsyndrome in a 49-year-old Japanese womanis reported. The patient exhibited prominent edema in her legs at night, but her edema usually improved by the following morning. The plasma concentrations of VEGFin the patient showed diurnal fluctuations; plasma VEGFlevels peaked at night and decreased in the daytime. Immunocytochemical study demonstrated the expression of VEGF in IgA-and^-positive plasma cells in bone marrow. The results indicate that VEGFwas produced at least by plasma cells and that VEGFproduction was regulated by circadian rhythm in synchronization with the developmentof edema.