Relationship between circulating tumor necrosis factor system and bone mass before and after estrogen plus progestogen therapy

Comparative Analysis of TNF-alpha, TNF-R1, and TNF-R2 in Patients with Low-impact Fractures Due to Osteoporosis

Objective  To analyze the serum levels of TNF-alpha and its TNF-R1 and TNF-R2 receptors in the blood of patients with low-impact fractures due to osteoporosis, comparing between genders and with healthy patients. Methods  The present study was conducted with a blood sample of 62 patients, divided into patients with osteoporosis and healthy patients. The results were obtained using the ELISA method. Cytokine concentrations were determined based on the absorbance values obtained. Results  Serum TNF-alpha levels were undetectable in female patients, while in males they were found only in one patient, with no significant difference. Similar results were found in the analyses of TNF-R1 and TNF-R2 levels, a significant increase in levels of TNF-alpha receptors in the groups of patients with osteoporosis compared with the control group in both sexes. There was no significant difference between the sexes in the dosage of both receptors within the group with osteoporosis. There was also a positive and significant correlation in the levels of TNF-R1 and TNF-R2 only in women. Conclusion The significant increase in TNF-R1 and TNF-R2 levels in women with osteoporosis suggest that the release and expression of these receptors may be contributing differently to the development of osteoporosis in men and women.

The Pathophysiology of Osteoporosis after Spinal Cord Injury

Spinal cord injury (SCI) affects approximately 300,000 people in the United States. Most individuals who sustain severe SCI also develop subsequent osteoporosis. However, beyond immobilization-related lack of long bone loading, multiple mechanisms of SCI-related bone density loss are incompletely understood. Recent findings suggest neuronal impairment and disability may lead to an upregulation of receptor activator of nuclear factor-κB ligand (RANKL), which promotes bone resorption. Disruption of Wnt signaling and dysregulation of RANKL may also contribute to the pathogenesis of SCI-related osteoporosis. Estrogenic effects may protect bones from resorption by decreasing the upregulation of RANKL. This review will discuss the current proposed physiological and cellular mechanisms explaining osteoporosis associated with SCI. In addition, we will discuss emerging pharmacological and physiological treatment strategies, including the promising effects of estrogen on cellular protection.

Association between circulatory levels of adipokines and bone mineral density in postmenopausal women

OBJECTIVE

Epidemiological evidence indicates that excess fat may be beneficial for bone health, offering protective effects against the onset of postmenopausal osteoporosis. Experimental data suggest that this link might be due to the direct effect of adipokines on bone tissue. Confirmatory evidence of this association, however, remains limited.

METHODS

The levels of a panel of selected adipokines including interleukin (IL)-6, -8, -1β, adipsin, lipocalin-2/neutrophil gelatinase-associated ipocalin, tumor necrosis factor alpha, monocyte chemoattractant protein-1, plasminogen activator inhibitor-1, hepatocyte growth factor, resistin, leptin, and adiponectin in a group of osteopenic and osteoporotic postmenopausal women were compared with those of unaffected women (n = 127).

RESULTS

Univariate analysis revealed that leptin and adiponectin were significantly correlated with bone mineral density (BMD). In particular, leptin was positively associated with BMD of the spine (r = 0.22, P < 0.05), femoral neck (r = 0.23, P < 0.05), trochanter (r = 0.20, P < 0.05), and total hip (r = 0.27, P < 0.01), whereas adiponectin was inversely correlated with BMD at the trochanter (r = -0.21, P < 0.05). No correlations were, however, significant after adjusting for body fat variables. Stratification of the sample according to IL-6 levels revealed that adiponectin remained significantly inversely associated with BMD, regardless of fat levels and age (β=-0.29, P < 0.05; r = 0.198) in the subgroup of participants with low levels of IL-6.

CONCLUSIONS

Our data suggest that circulating adiponectin is inversely associated with markers of bone health in postmenopausal women, and that the interaction is influenced by IL-6 levels.

Association between seven common OPG genetic polymorphisms and osteoporosis risk: a meta-analysis

Functional polymorphisms of the osteoprotegerin (OPG) gene are known to be involved in bone mineral density and the development of osteoporosis; however, some conflicting results have been reported. The aim of this meta-analysis is to provide a relatively comprehensive assessment of the relationship between seven common OPG genetic polymorphisms (T149C, A163G, G209A, T245G, T950C, G1181C, and C1217T) and osteoporosis risk. A literature search for eligible studies published before August 1st, 2013 was conducted in PubMed, Embase, Web of Science, Cochrane Library, and CNKI (China National Knowledge Infrastructure) databases. Pooled odds ratios and their corresponding 95% confidence intervals were used to evaluate the strength of the association under fixed- or random-effect models according to a heterogeneity test. All analyses were performed using the STATA software, version 12.0. Fourteen case-control studies with a total of 2383 osteoporosis cases and 2280 healthy controls were included in this meta-analysis. Among the seven polymorphisms, A163G and G1181C revealed significant associations with osteoporosis risk. For A163G (rs3102735), the combined results showed that the G allele of the A163G polymorphism may be associated with an increased risk of osteoporosis. Stratified analyses showed that the magnitude of the effect was similar in Caucasian and postmenopausal woman subgroups. For G1181C (rs2073618), however, we found that individuals with the C allele of the G1181C polymorphism had a decreased risk of osteoporosis, especially in Asian and postmenopausal woman subgroups. In summary, this meta-analysis indicated that the G allele of the OPG A163G polymorphism might increase osteoporosis risk in Caucasians, whereas individuals with the C allele of the G1181C polymorphism had a decreased risk of osteoporosis, especially in Asians. Both of these effects were observed in postmenopausal women. These polymorphisms could probably be used with other genetic markers together to identify individuals at a high risk of osteoporosis.