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Background: Fibroblast growth factor (FGF23) is a protein that is produced by osteoblasts and osteocytes. Increased serum levels of FGF23 have been associated with increased risks of osteoporotic fractures and cardiovascular disease, particularly in participants with poor renal function. Serum iron (Fe) has been suggested as a regulator of FGF23 homeostasis. Objective: To determine whether Fe and iron status are determinants of the levels of intact FGF23 (iFGF23) in elderly men. Methods: The MrOS study is a population-based study of elderly men (N = 1010; mean age, 75.3 years; range, 69–81 years). The levels of Fe, transferrin saturation (TS), and ferritin were evaluated in relation to the serum concentrations of iFGF23 before and after adjustments for confounders. Results: TS < 15% was found in 3.5% (34/977) of the participants, who had a higher median level iFGF23 compared with the remaining subjects (47.4 μmol/L vs. 41.9 μmol/L, p = 0.008). The levels of iFGF23 correlated negatively (un-adjusted) with the levels of Fe (r = − 0.17, p < 0.001), TS (r = − 0.16, p < 0.001) and serum ferritin (r = − 0.07, p = 0.022). In addition, in participants with estimated glomerular filtration rate eGFRCystatin C > 60 mL/min, the levels of iFGF23 correlated (age-adjusted) negatively with the levels of Fe (r = − 0.15, p < 0.001) and TS (r = − 0.17, p < 0.001). The level of iFGF23 correlated positively (un-adjusted) with lumbar spine bone mineral density (BMD) (r = 0.14, p < 0.001), total body BMD (r = 0.11, p = 0.001), and total hip BMD (r = 0.09, p = 0.004). The corresponding correlations, when adjusted for age, weight, and height were: r = 0.08, p = 0.018; r = 0.05, p = 0.120; and r = 0.02, p = 0.624, respectively. No associations were found between BMD and the levels of Fe or TS. Multiple step-wise linear regression analyses [adjusting for age, body mass index (BMI), comorbidity index, cystatin C, C-reactive protein (hs-CRP), serum vitamin D 25-OH (25OHD), phosphate, calcium, parathyroid hormone (PTH), erythropoietin, hemoglobin, lumbar spine BMD, apolipoprotein B/A1 ratio] were performed in three separate models with Fe, TS or ferritin as potential explanatory variables. Fe and TS, but not ferritin, were independent predictors of iFGF23 level (standardized β-values: − 0.10, p < 0.001; − 0.10, p < 0.001; and − 0.05, p = 0.062, respectively). Conclusion: Low levels of Fe in elderly men are associated with high levels of iFGF23, independently of markers of inflammation and renal function, suggesting an iron-related pathway for FGF23 regulation.

Fracture healing is a complex interplay between endochondral and intramembranous bone formation processes. The canonical Wnt/β-catenin pathway enhances new bone formation and may play a role in fracture healing. Glycogen synthase kinase 3β (GSK3β) is a key regulator of β-catenin degradation. In this study, we investigate the effects of AZD2858, an orally bioactive GSK3 inhibitor, on fracture healing. Femoral fractures were produced in rats after the insertion of a femoral nail. The rats were treated with oral administration of AZD2858 at a dose of 30 μmol/kg (20mg/kg) daily for up to 3 weeks, while control animals were administered vehicle. At 4days, and at 1, 2 and 3 weeks, histological analysis was performed, and at the 2 and 3 week time points, we performed peripheral quantitative computed tomography (pQCT), X-rays, and four-point bending tests. Peripheral QCT showed an increase in both mineral density (of 28% at 2 weeks and 38% at 3weeks) and mineral content (of 81% at 2 weeks and 93% at 3 weeks) in the calluses from AZD2858 treated animals as compared to vehicle treated animals. Histological analysis demonstrated that rats treated with GSK3 inhibitor healed their fractures rapidly, but without the pre-formation of cartilage tissue. Furthermore, four-point bending tests of fractured femora from animals treated for 2 and 3 weeks showed an increase in strength in treated animals compared to their vehicle-treated controls. In conclusion, AZD2858, a potent GSK3 inhibitor, has a substantial impact on fracture healing. The fractures healed with a bony callus without an obvious endochondral component, suggesting that AZD2858 drives mesenchymal cells into the osteoblastic pathway. This leads to direct bone repair in an unstable fracture milieu.

Glycogen synthase kinase 3β (GSK-3β) actions are central in the canonical Wnt pathway, important in many biological processes and a potential drug target for treating several diseases. It is appreciated that a balanced Wnt canonical signaling is crucial for the maintenance of normal bone mass. In this study we investigated the effects of a potent orally active GSK-3 inhibitor, AZD2858, on bone mass in rats. Treatment (1 μM) of human osteoblast cells with AZD2858 in vitro increased β-catenin levels after a short period of time. In rats, oral AZD2858 treatment caused a dose-dependent increase in trabecular bone mass compared to control after a two-week treatment with a maximum effect at a dose of 20 mg/kg once daily (total BMC: 172% of control; p

Sex steroids are important for growth and maintenance of the skeleton. Catechol-O-methyltransferase (COMT) is an estrogen degrading enzyme. The COMT val158met polymorphism results in a 60-75% difference in enzyme activity between the val (high activity=H) and met (low activity=L) variants. We have previously reported that this polymorphism is associated with bone mineral density (BMD) in young men. The aim of this study was to investigate associations between COMT val158met, BMD and fractures in elderly men.Population-based study of Swedish men 75.4, SD 3.2, years of age. Fractures were reported using standardized questionnaires. Fracture and genotype data were available from 2,822 individuals.Total number of individuals with self-reported fracture was 989 (35.0%). Prevalence ofor=1 fracture was 37.2% in COMT(LL), 35.7% in COMT(HL) and 30.4% in COMT(HH) (p0.05). Early fractures (or=50 years of age) were less common in COMT(HH) than in the combined COMT(LL+HL) genotype, OR 0.78 (95% CI 0.63-0.97). No associations were found for late fractures (50 years of age). The OR for fracture of the non-weight bearing skeleton in COMT(HH) compared with COMT(LL+HL) was 0.74 (95% CI 0.59-0.92). No associations between COMT val158met and BMD were found in this cohort of elderly men.The COMT val158met polymorphism is associated with life time fracture prevalence in elderly Swedish men. This association is mainly driven by early fractures (or=50 years of age).

Vertebral fracture risk is a heritable complex trait. The aim of this study was to identify genetic susceptibility factors for osteoporotic vertebral fractures applying a genome-wide association study (GWAS) approach. The GWAS discovery was based on the Rotterdam Study, a population-based study of elderly Dutch individuals aged55 years; and comprising 329 cases and 2666 controls with radiographic scoring (McCloskey–Kanis) and genetic data. Replication of one top-associated SNP was pursued by de-novo genotyping of 15 independent studies across Europe, the United States, and Australia and one Asian study. Radiographic vertebral fracture assessment was performed using McCloskey–Kanis or Genant semi-quantitative definitions. SNPs were analyzed in relation to vertebral fracture using logistic regression models corrected for age and sex. Fixed effects inverse variance and Han–Eskin alternative random effects meta-analyses were applied. Genome-wide significance was set at p5 × 10− 8. In the discovery, a SNP (rs11645938) on chromosome 16q24 was associated with the risk for vertebral fractures at p = 4.6 × 10− 8. However, the association was not significant across 5720 cases and 21,791 controls from 14 studies. Fixed-effects meta-analysis summary estimate was 1.06 (95% CI: 0.98–1.14; p = 0.17), displaying high degree of heterogeneity (I2 = 57%; Qhet p = 0.0006). Under Han–Eskin alternative random effects model the summary effect was significant (p = 0.0005). The SNP maps to a region previously found associated with lumbar spine bone mineral density (LS-BMD) in two large meta-analyses from the GEFOS consortium. A false positive association in the GWAS discovery cannot be excluded, yet, the low-powered setting of the discovery and replication settings (appropriate to identify risk effect size1.25) may still be consistent with an effect size1.10, more of the type expected in complex traits. Larger effort in studies with standardized phenotype definitions is needed to confirm or reject the involvement of this locus on the risk for vertebral fractures.

Interleukin-13 (IL-13) inhibits cell proliferation and stimulates interleukin-6 (IL-6) formation in isolated human osteoblasts (hOBs). Because the related cytokine, interleukin-4 (IL-4), is known to exert effects similar to IL-13 in other tissues, and because IL-4 has been implicated as a regulator of bone metabolism, we compared the effects of IL-13 and IL-4 on cell proliferation, IL-6 synthesis, the expression of osteoblastic phenotypic markers in hOB cultures. Also, the receptor proteins mediating these effects in hOBs have been partly characterized. IL-4 and IL-13 dose-dependently inhibited [(3)H]-thymidine incorporation into the DNA of human osteoblasts and stimulated secretion of IL-6 into culture supernatants. IL-13 and IL-4 also increased the mRNA levels of IL-6, as measured by RNAse protection assay. Furthermore, IL-13 and IL-4 dose-dependently enhanced alkaline phosphatase (ALP) activity, but did not affect osteocalcin or collagen type I synthesis. IL-4 was tenfold more potent than IL-13 in inducing both ALP activity and IL-6 secretion, whereas the cytokines were equipotent as inhibitors of cell proliferation. The expression of mRNA for receptor subunits previously implicated in IL-4 and IL-13 signaling was investigated by reverse transcriptase-polymerase chain reaction. IL-13R, IL-13Ralpha, and IL-4Ralpha mRNA were repeatedly detected in hOBs, whereas mRNA for IL-2Rgamma(C) was not detected. Receptor-blocking antibodies to IL-4Ralpha inhibited the induction of IL-6 formation by both IL-4 and IL-13, indicating that both cytokines utilize this receptor subunit in signaling. However, the antibodies did not affect the IL-4/-13-induced inhibition of [(3)H]-thymidine incorporation or the stimulation of alkaline phosphatase (ALP), suggesting that IL-4Ralpha does not mediate these effects of IL-4/-13 in hOBs. We conclude that the cytokines IL-13 and IL-4, through sharing of receptor components, induce similar effects on hOBs, causing inhibition of cell proliferation, stimulation of IL-6, and enhanced ALP activity.

Objective: We used dual X-ray absorptiometry (DXA) to measure calcaneal bone mineral density (BMD) and estimate the prevalence of osteoporosis in a population with distal forearm fracture and a normative cohort. Methods: Patients 20 to 80 years of age with distal forearm fracture treated at one emergency hospital during two consecutive years were invited to calcaneal BMD measurement; 270 women (81%) and 64 men (73%) participated. A DXA heel scanner estimated BMD (g/cm(2)) and T-scores. Osteoporosis was defined as T-score

Although vitamin D supplementation is a fundamental part of osteoporosis treatment, many patients do not regularly take adequate amounts. A once-weekly (OW) alendronate (ALN) preparation that includes 2800 IU of vitamin D3 in a single combination tablet (ALN+D2800) is available for treating patients and ensuring intake of vitamin D that is consistent with existing guidelines. This randomized, double-blind study extension was conducted to evaluate the safety and tolerability of ALN+D2800 and ALN+D2800 plus an additional 2800 IU vitamin D3 single tablet supplement (ALN+D5600) administered for 24 weeks in men and postmenopausal women with osteoporosis previously treated OW for 15 weeks with either ALN or ALN+D2800. The primary endpoint was the proportion of participants who developed hypercalciuria (defined as a 24-hour urine calcium >300 mg in women or >350 mg in men and an increase of >25% versus randomization baseline) at week 39. The key secondary endpoint was the proportion of participants with vitamin D insufficiency (serum 25(OH)D

Polymorphisms in the Klotho (Kl) gene, which is central for vitamin D regulation by fibroblast growth factor 23 (FGF23), have been associated with longevity, coronary disease and stroke. The CC genotype of the single nucleotide polymorphism (SNP) rs577912 in the Kl-gene is associated with decreased Kl expression, as well as increased mortality in end stage renal disease. We examined if SNP in the Kl-gene was associated with mortality in the community derived cohort of 70 to 80 year old males of MrOS Sweden (N = 3014).High throughput genotyping of the KLOTHO SNPs was achieved by use of SequenomR MassEXTEND/Mass/ARRAY technology. 2738 subjects had a valid result for rs577912: CC 73.1% and CA + AA 26.9%. There were no differences in the serum levels of FGF23, phosphate, parathyroid hormone or renal function between genotypes CC and CA + AA. During a follow-up of a median of 4.5 years there were 337 deaths, 253 (12.6%) in the CC group and 84 (11.4%) in the CA + AA group. With log rank analysis there were no differences in mortality between the genotypes for all cause mortality (P = 0.39) or cardiovascular mortality (P = 0.60). None of the other SNPs in the Kl gene was associated with mortality in this cohort either.Conclusion:There is no association between the SNP rs577912 in the Kl-gene and mortality among elderly men.

We have investigated the effects on bone resorption of two new potent antiproliferative vitamin D3 analogs, EB 1089 and KH 1060, by studying recruitment of osteoclasts in murine bone marrow cultures and 45Ca release from prelabeled neonatal mouse calvarial bones. Binding studies to vitamin D receptor protein, from human osteosarcoma MG-63 cells, demonstrated kd values of 8.5 × 10−11 for 1α,25(OH)2D3, 6.5 × 10−11 for KH 1060, and 2.7 × 10−10 for EB 1089. 1α,25(OH)2D3 and EB 1089 were equipotent stimulators of osteoclast recruitment in murine bone marrow cultures, with EC50 at 10−10 mol/L, whereas KH 1060 was about tenfold more potent with an EC50 at 10−11 mol/L. In serum-free media, 1α,25(OH)2D3 enhanced 45Ca release from neonatal mouse calvarial bones with EC50 at 10−11 mol/L, but in the presence of 10% fetal calf serum (FCS) the stimulatory effect was significantly diminished, with a threshold value at 10−10 mol/L. EB 1089 stimulated bone resorption with an estimated EC50 at 3 × 10−11 mol/L, whereas KH 1060 was about tenfold more potent than 1α,25(OH)2D3, and stimulated bone resorption with an EC50 at 10−12 mol/L. The effects of EB 1089 and KH 1060 on 45Ca release were not significantly affected by the addition of 10% FCS. Addition of vitamin D binding protein to serum-free incubations of neonatal mouse calvarial bones significantly inhibited the bone resorbing effect of 1α,25(OH)2D3, but did not affect EB 1089 and KH 1060 induced 45Ca release. These data show that the kd values for the binding to Vitamin D receptors are similar to the EC50 values for stimulation of bone resorption and osteoclast differentiation, in vitro, for 1α,25(OH)2D3, EB 1089, and KH 1060. The discrepancy in the effect of FCS on 45Ca release between 1α,25(OH)2D3, and the new analogs suggests that EB 1089 and KH 1060 do not bind to vitamin D binding protein, indicating that pharmacokinetic differences may partially explain their less calcemic effects in vivo.

Objective: Osteogenesis imperfecta (OI) is a rare heterogeneous disease of connective tissue leading to varying degrees of bone fragility. The worst form (type II) is peri-natally lethal whereas the mildest form (type I) is compatible with a normal life span. Over 1000 mutations causing OI have been described in the genes encoding collagen type I. As COL1A1 and COL1A2 are large genes, there are still many codon positions where no mutations have been reported and only a fraction of theoretically possible glycine substitutions have been described. In this study the spectrum of mutations causing OI in Sweden will be investigated and genotype–phenotype correlations as well as pharmacogenetics will be studied. Method: All patients with OI cared for at the Uppsala Osteoporosis Unit (Uppsala University Hospital) or Astrid Lindgren's Paediatric Hospital (Karolinska Institutet, Stockholm) were offered to enter the study. Patients from 140 unrelated families with OI accepted participation; 77 type I, 34 type IV, 20 type III, 5 without previous diagnosis and 4 with unclear OI type. Extensive clinical data is currently being collected on enrolled patients. Exons and flanking intron sequences of COL1A1 and COL1A2 are being sequenced in these families. Results: So far 133/140 families have been completely analyzed and in 27 no mutation was found. A total of 120 mutations have been detected, of which 104 are of a typical OI-type. In COL1A1 73 mutations were found and in COL1A2 31 mutations were noted. In 7 families 2 mutations were present, but only one of these was a typical OI-causing mutation. To date 16 amino acid changing mutations that were not of a typical OI-causing type have been noted and the majority of these have an unclear significance. Calculations of delta BMD Z-score response to bisphosphonate treatment did not show a difference in treatment response between groups with different types of OI or between patients with OI type I due to a qualitative vs. a quantitative collagen type I defect. Conclusion: The spectrum of mutations causing OI described in this Swedish cohort is of the expected type, with the exception of the amino acid changing mutations. It is notable that in seven families two separate mutations were identified. Calculations do not support a mutation dependent response to bisphosphonate treatment.