An assessment of genetic markers as predictors of bone turnover in healthy adults

Polymorphism in vitamin D receptor and osteoprotegerin genes in Egyptian rheumatoid arthritis patients with and without osteoporosis

1α,25-Dihydroxyvitamin D3 upregulates the expression of the receptor activator of nuclear factor kB ligand (RANKL), and downregulates osteoprotegerin (OPG) expression. We tested the effects of polymorphisms in the vitamin D receptor gene (VDR), and OPG gene in rheumatoid arthritis (RA) patients and healthy controls and their relationship to bone mineral density (BMD) and development of osteoporosis. Three hundred and fifty women were evaluated, 200 women having RA and 150 healthy control. The subjects were genotyped for polymorphism at BsmI in VDR and A163G in OPG genes by polymerase chain reaction followed by restriction fragment length polymorphism analysis. BMD was also measured. In A163G, the G allele increased the risk for RA and for the development of osteoporosis. We found a significant association between lower hip (BMD-h) and genotype variants of VDR (BsmI) and OPG A163G in RA patients with osteoporosis. Our results suggested that OPG A163G polymorphism was associated with RA susceptibility and with the development of osteoporosis in these patients. Also, VDR and OPG genes are important candidates for osteoporosis in RA patients.

Estrogen receptor alpha gene analysis in osteoporosis and familial osteoporosis

Estrogens are important determinants of bone mineral density (BMD) mediating their effects via estrogen receptor alpha (ERalpha) and beta (ERbeta). The strong genetic predisposition to osteoporosis, and the fact that alterations in the aminoterminal region of ERalpha have been linked to bone disturbances, prompted us to identify genetic alterations in exon 1 and exon 2 of ERalpha in osteoporotic individuals. Sixty-two unrelated normal subjects (age 46.1+/-9.5 years) and 72 unrelated osteoporotic subjects (age 52.3+/-7.9 years) were studied. Their menopausal status was pre- and perimenopausal. We also included 30 related osteoporotic individuals (mother-daughter or sister-sister relationship) (age 46.2+/-12.8 years) belonging to 14 families who where also pre- and perimenopausal. DNA was extracted from peripheral blood, exons 1 and 2 were amplified by polymerase chain reaction (PCR) and were further submitted to denaturing gradient gel electrophoresis (DGGE), single stranded conformational polymorphism (SSCP), restriction fragment length polymorphism (RFLP) and sequence analysis. Bone turnover markers were also determined. Two polymorphisms were identified in exon 1 (codons 10 and 87) in both normal and osteoporotic women. Statistical analysis revealed no difference (P>0.05) in the ERalpha genotype frequencies within osteoporotic families as compared with the same genotypes in the unrelated normal or osteoporotic subjects. Codon 10, codon 87 polymorphisms were not related to BMD or bone turnover markers. No other mutations were found in exons 1 and 2 in all subjects studied. Genetic alterations in exons 1 and 2 of ERalpha are not associated to osteoporosis and familial osteoporosis. Moreover, the codon 10 and codon 87 polymorphisms do not seem to be correlated with BMD and bone turnover markers.