Osteoporosis in Glucocorticoid-Dependent Asthmatic Patients: Literature Review and Recommendations

The localization of the functional glucocorticoid receptor alpha in human bone

Glucocorticoids have well-documented effects on the skeleton, although their mechanism of action is still poorly understood. The actions of glucocorticoids on bone cells are mediated, in part, directly via specific receptors. The presence of these receptors has been demonstrated in both rodent and human osteoblastic cells in vitro, but their presence in human bone in vivo has not been reported. In this study, we have used specific affinity purified polyclonal antibodies to the functional glucocorticoid receptor alpha (GRalpha) to investigate its expression in both developing and adult human bone using sections of neonatal rib, calvarial, and vertebral bones, tibial growth plates from adolescents, and iliac crest biopsies from adults who were to undergo liver transplantation. In the tibial growth plates, GRalpha was predominantly expressed in the hypertrophic chondrocytes within the cartilage. In the primary spongiosa, the receptor was highly expressed by osteoblasts at sites of bone modeling. Within the bone marrow, receptors were also detected in mononuclear cells and in endothelial cells of blood vessels. In the neonatal rib and vertebrae, GRalpha was widely distributed at sites of endochondral bone formation in resting, proliferating, mature, and hypertrophic chondrocytes. They were also highly expressed in osteoblasts at sites of bone modeling. At sites of intramembranous ossification in neonatal calvarial bone and rib periosteum, GRa was widely expressed in cells within the fibrous tissue and in osteoblasts at both the bone-forming surface and at modeling sites. In the iliac crests from adults, GRalpha was predominantly expressed in osteocytes. The receptors were not detected in osteoclasts. Our results show for the first time the presence of the functional GRalpha in human bone in situ and suggest that the actions of glucocorticoids on bone may be mediated, in part, directly via the GR at different stages of life. The absence of receptor expression in osteoclasts also suggests that the effects of glucocorticoids on bone resorption may be mediated indirectly.

Safety and efficacy of fluticasone and beclomethasone in moderate to severe asthma. Belgian Multicenter Study Group

There are still some concerns about the safety of high doses of inhaled glucocorticosteroids (ICS). We compared the safety and efficacy of fluticasone propionate (FP) and beclomethasone dipropionate (BDP) in 306 patients with moderate to severe asthma in a double-blind, multicenter, cross-over study of 12 mo duration. During the 1-mo run-in period, bronchodilators were replaced by salmeterol 50 microg twice daily, increasing morning peak expiratory flow rate (PEFR) by 28 L/min (p < 0.001) and FEV1 by 6.2% predicted (p < 0.001). At randomization the current ICS was replaced by 500 microg BDP or 250 microg FP in accordance with previously taken 500 microg BDP or 400 microg budesonide (BUD). No significant differences between the two treatments regarding morning plasma cortisol, urinary excretion of calcium and hydroxyproline, FEV1, and PEFR were observed at any time point during the study. Osteocalcin and bone mineral density (BMD) were improved over baseline in the FP group, resulting in higher serum osteocalcin levels (mean difference 0.28 ng/ml; p < 0.001) and higher BMD in the spine (1.0%; p = 0.05), femoral neck (1.6; p < 0.01), and Ward's triangle (3.6%; p = 0.01) as compared with BDP. We conclude that chronic treatment with FP, at half the dose of BDP, results in a similar antiasthma effect but a more favorable safety profile with respect to bone metabolism and mineral density.