Nonassociation of interleukin-1 receptor antagonist genotypes with bone mineral density, bone turnover status, and estrogen responsiveness in Korean postmenopausal women

Deficiency of interleukin-1 receptor antagonist in mice differentially affects bone properties under different genomic backgrounds

When IL-1 receptor antagonist (IL-1rn) is knocked out, mice have shown strain background dependent and major QTL regulated susceptibility to spontaneously inflammatory arthritis disease (SAD). The impact on bone properties resulting from the interactions of IL-1rn, genomic background strains, and the QTL locus, is unknown. Bone properties in the four specifically bred mouse strains with mutation of IL-1rn and variations in genomic components were investigated with high-resolution MicroCT and genomic analytical tools. Two congenic mouse strains were also measured to evaluate the influence on bone properties by a QTL in the region in chromosome 1. Our results reveal that several bone phenotypes, including bone mineral density (BMD), bone volume, tibial length, and cortical thickness of the tibia are different between wild type and IL-1rn knockout mice in both Balb/c and DBA/1 backgrounds, but IL-1rn knockout affects BMD differently between the two mouse strains. The absence of IL-1rn decreases BMD in Balb/c mice but increases BMD in DBA/1-/- mice compared to their respective wild type counterparts. A QTL transferred from the Balb/c genetic background which affects arthritis in congenic strains appears to also regulate BMD. While several genes, including Ctsg and Prg2, may affect BMD, Ifi202b is the most favored candidate gene for regulating BMD as well as SAD. In conclusion, the previously mentioned bone phenotypes are each influenced in different ways by the loss of IL-1ra when considered in mice from varying genomic backgrounds.

Polymorphisms of the human IL-1 receptor antagonist gene and forearm bone mineral density in postmenopausal women

CONTEXT

Studies on the human interleukin 1 receptor antagonist (IL-1RA) gene polymorphism have provided conflicting data regarding the bone mass and quality.

AIM AND DESIGN

The objective of this case-control study was to investigate the association between the forearm bone mineral density (BMD) and the IL1RA gene polymorphisms.

MATERIALS AND METHODS

A total of 400 postmenopausal Bulgarian women participated in this study. BMD was measured at the forearm by X-ray absorptiometry on a DTX-100 device (Osteometer Meditech, USA). A PCR product was isolated. The alleles were scored according to their length: A1 - 410 bp - 4 repeats; A2 - 240 bp - 2 repeats; A3 - 500 bp - 5 repeats; A4 - 325 bp - 3 repeats; A5 - 595 bp - 6 repeats. All analyses were evaluated for statistical significance (χ(2)-test and T-test).

RESULTS

Four alleles were observed - A1, A2, A3, and A4. The A1A1 genotype was more common in cases with low BMD than in controls with normal BMD (95% vs. 90%, χ(2)P < 0.01). The A2A2 genotype was equally distributed among cases and controls (both 5%). The other two genotypes (A3A3 and A4A4) as well as A1A3 were present only in controls with normal BMD. The A2A2 genotype was associated with higher BMD and the A1A1 - with lower BMD at both forearm sites. The odds ratio for low BMD in the presence of the A1A1 genotype was 2.11. The etiological factor reflecting the association between the polymorphism and the disease was 0.50. In our study sample the IL1RA genetic polymorphisms were associated with the forearm BMD.

CONCLUSION

This genetic polymorphism may become a useful genetic marker for the study of osteoporosis.

Systemic bone effects of biologic therapies in rheumatoid arthritis and ankylosing spondylitis

Inflammatory joint diseases are responsible of chronic systemic inflammation, joint degradations, deformities, and altered quality of life. Patients suffering from chronic rheumatic diseases also present increased bone fragility and increased fracture risk. Registration of biologic therapies has deeply modified care in rheumatic diseases, especially in rheumatoid arthritis and ankylosing spondylitis. The available biologics are the anti proinflammatory cytokine therapies (TNFα blockers, anakinra and tocilizumab) and the biologics active on T cell activation (abatacept and rituximab). These drugs succeeded in blocking disease activity and joint degradation. They are also able to stop systemic bone loss among patients with inflammatory rheumatic diseases. In this review, we present the current understanding of the inflammatory-induced bone loss and the skeletal effects of biologic therapies in inflammatory joint diseases.

Vitamin D and bone health: potential mechanisms

Osteoporosis is associated with increased morbidity, mortality and significant economic and health costs. Vitamin D is a secosteriod hormone essential for calcium absorption and bone mineralization which is positively associated with bone mineral density [BMD]. It is well-established that prolonged and severe vitamin D deficiency leads to rickets in children and osteomalacia in adults. Sub-optimal vitamin D status has been reported in many populations but it is a particular concern in older people; thus there is clearly a need for effective strategies to optimise bone health. A number of recent studies have suggested that the role of vitamin D in preventing fractures may be via its mediating effects on muscle function (a defect in muscle function is one of the classical signs of rickets) and inflammation. Studies have demonstrated that vitamin D supplementation can improve muscle strength which in turn contributes to a decrease in incidence of falls, one of the largest contributors to fracture incidence. Osteoporosis is often considered to be an inflammatory condition and pro-inflammatory cytokines have been associated with increased bone metabolism. The immunoregulatory mechanisms of vitamin D may thus modulate the effect of these cytokines on bone health and subsequent fracture risk. Vitamin D, therefore, may influence fracture risk via a number of different mechanisms.

Molecular genetic studies of gene identification for osteoporosis: a 2004 update

This review summarizes comprehensively the most important and representative molecular genetics studies of gene identification for osteoporosis published up to the end of December 2004. It is intended to constitute a sequential update of our previously published review covering the available data up to the end of 2002. Evidence from candidate gene association studies and genome-wide linkage studies in humans, as well as quantitative trait locus mapping animal models are reviewed separately. Studies of transgenic and knockout mice models relevant to osteoporosis are summarized. An important extension of this update is incorporation of functional genomic studies (including DNA microarrays and proteomics) on osteogenesis and osteoporosis, in light of the rapid advances and the promising prospects of the field. Comments are made on the most notable findings and representative studies for their potential influence and implications on our present understanding of genetics of osteoporosis. The format adopted by this review should be ideal for accommodating future new advances and studies.