RESUMO
Osteoporosis is a complex multi-factorial disease where environment, diet and genetics play a role in determining susceptibility. Patients with existing vertebral fracture have a heightened risk of further recurrent vertebral fracture. The efficacy of new osteoporosis therapies is often compared to calcium supplementation. 1,25-dihydroxyvitamin D3 (calcitriol) acts through the vitamin D receptor (VDR) and is effective at reducing recurrent vertebral fracture risk. Because the VDR controls calcium metabolism, we hypothesized that genetic variation at the VDR locus may influence response to both calcium and calcitriol therapy. Postmenopausal women with osteoporosis from a 3-year study comparing calcitriol versus calcium for prevention of vertebral fractures were genotyped for VDR alleles detected by FokI, BsmI, ApaI and TaqI. Data were analysed by hierarchical log-linear analysis and robust analysis of variance for relationships to fracture outcomes. Significant differences in the vertebral fracture rate in response to calcium therapy were observed between VDR genotypes (P<0.001). Calcium appeared to be equally effective as calcitriol in particular genotypes. The response to calcitriol therapy was most pronounced in patients carrying the TaqI t allele in combination with the FokI f initiation codon variant: f+t+ carriers were 11.3-fold less likely to sustain recurrent vertebral fracture in the last 2 years of the trial while on calcitriol therapy compared to calcium (P=1.4x10(-5)). Response to both calcium and calcitriol therapy is dependent on genetic variation at the VDR locus and two loci in the VDR gene may contribute to this effect.
Assuntos
Calcitriol/farmacologia , Genótipo , Osteoporose/tratamento farmacológico , Osteoporose/genética , Receptores de Calcitriol/genética , Alelos , Cálcio/metabolismo , Ensaios Clínicos como Assunto , Códon , Feminino , Fraturas Ósseas , Marcadores Genéticos , Variação Genética , Heterozigoto , Humanos , Osteoporose Pós-Menopausa/tratamento farmacológico , Pós-Menopausa , Resultado do TratamentoRESUMO
UNLABELLED: Differential expression of TBP-2 and Trx-1 occurs during osteoclastogenesis. Adenoviral overexpression of TBP-2 in osteoclast precursors inhibits Trx-1 expression, osteoclast formation, and AP-1 binding activity. TBP-2 and Trx-1 are key regulators of osteoclastogenesis. INTRODUCTION: Thioredoxin binding protein-2 (TBP-2) negatively regulates thioredoxin-1 (Trx-1), a key endogenous modulator of cellular redox and signaling. In gene array analysis, we found that TBP-2 expression was reduced during human osteoclast differentiation compared with macrophage differentiation. Our aim was to determine the roles of TBP-2 and Trx-1 in human osteoclastogenesis and RANKL signaling. MATERIALS AND METHODS: Osteoclasts or macrophages were generated from colony-forming unit-granulocyte macrophage (CFU-GM) precursors treated with sRANKL and macrophage-colony-stimulating factor (M-CSF), or M-CSF alone, respectively. Expression of TBP-2 and Trx-1 was quantified by real-time PCR and Western analysis. Adenoviral gene transfer was used to overexpress TBP-2 in precursors. NF-kappaB and activator protein 1 (AP-1) signaling was assessed with EMSA. RESULTS: In the presence of sRANKL, expression of TBP-2 was decreased, whereas Trx-1 expression was increased. The antioxidant N-acetylcysteine reversed this pattern and markedly inhibited osteoclastogenesis. Adenoviral overexpression of human TBP-2 in precursors inhibited osteoclastogenesis and Trx-1 expression, inhibited sRANKL-induced DNA binding of AP-1, but enhanced sRANKL-induced DNA binding of NF-kappaB. CONCLUSIONS: These data support significant roles for TBP-2 and the Trx system in osteoclast differentiation that are mediated by redox regulation of AP-1 transcription. A likely mechanism of stress signal induction of bone resorption is provided. Modulators of the Trx system such as antioxidants have potential as antiresorptive therapies.
Assuntos
Proteínas de Transporte/fisiologia , Regulação da Expressão Gênica , Osteoclastos/citologia , Adenoviridae/genética , Antioxidantes/química , Antioxidantes/farmacologia , Western Blotting , Proteínas de Transporte/metabolismo , Diferenciação Celular , Relação Dose-Resposta a Droga , Técnicas de Transferência de Genes , Humanos , Receptores de Lipopolissacarídeos/biossíntese , Macrófagos/citologia , Macrófagos/metabolismo , Glicoproteínas de Membrana/metabolismo , NF-kappa B/metabolismo , Análise de Sequência com Séries de Oligonucleotídeos , Osteoclastos/metabolismo , Oxirredução , Ligação Proteica , Ligante RANK , RNA Mensageiro/metabolismo , Receptor Ativador de Fator Nuclear kappa-B , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais , Tiorredoxinas/metabolismo , Fatores de Tempo , Fator de Transcrição AP-1/metabolismoRESUMO
Bone mineral density (BMD) is influenced by both environmental and genetic factors. We previously reported the association of the RUNX2 A allele with increased bone mineral density (BMD) and protection against a common form of osteoporotic fracture within a Geelong population. We genotyped 991 women from a Scottish cohort to decipher the role of RUNX2 alleles in regulating BMD. The alleles of RUNX2 within the glutamine-alanine repeat were determined by MspA1I restriction digest. Allele frequencies estimated from Scottish cohort were G allele, 0.87 +/- 0.01; A allele, 0.08 +/- 0.01; and 11Ala alanine deletion allele, 0.05 +/- 0.01. Analysis of covariance (ANCOVA) was used to adjust for the covariates weight and age for BMD at the femoral neck (FN). The A allele was associated with higher FN BMD (P = 0.035) within a postmenopausal subgroup of the population (n = 312). The effect of RUNX2 A alleles increased with increasing weight; A alleles were associated with FN BMD in those above the median BMI (BMI > 25), while no association was observed in thin/normal (BMI
Assuntos
Índice de Massa Corporal , Densidade Óssea/genética , Proteínas de Ligação a DNA/genética , Frequência do Gene/genética , Menopausa/genética , Fatores de Transcrição/genética , Análise de Variância , Sequência de Bases/genética , Estudos de Coortes , Subunidade alfa 1 de Fator de Ligação ao Core , Feminino , Genótipo , Humanos , Pessoa de Meia-Idade , Dados de Sequência Molecular , Escócia , Fator de Transcrição AP-2RESUMO
The aim of this study was to determine if DNA polymorphism within runt-related gene 2 (RUNX2)/core binding factor A1 (CBFA1) is related to bone mineral density (BMD). RUNX2 contains a glutamine-alanine repeat where mutations causing cleidocranial dysplasia (CCD) have been observed. Two common variants were detected within the alanine repeat: an 18-bp deletion and a synonymous alanine codon polymorphism with alleles GCA and GCG (noted as A and G alleles, respectively). In addition, rare mutations that may be related to low BMD were observed within the glutamine repeat. In 495 randomly selected women of the Geelong Osteoporosis Study (GOS), the A allele was associated with higher BMD at all sites tested. The effect was maximal at the ultradistal (UD) radius (p = 0.001). In a separate fracture study, the A allele was significantly protective against Colles' fracture in elderly women but not spine and hip fracture. The A allele was associated with increased BMD and was protective against a common form of osteoporotic fracture, suggesting that RUNX2 variants may be related to genetic effects on BMD and osteoporosis.
