The rise in expression and activity of 11ß-HSD1 in human mesenchymal progenitor cells induces adipogenesis through increased local cortisol synthesis.

11ß-Hydroxysteroid dehydrogenase 1 (11ß-HSD1) plays an important role in pre-receptor glucocorticoid metabolism. This enzyme is expressed in bone, increases with age, and catalyzes the conversion of the inactive glucocorticoid cortisone into the active glucocorticoid cortisol and vice versa. Here we hypothesized that the physiological activity of 11ß-HSD1 to produce cortisol in human mesenchymal progenitor cells (hMSC) is principally sufficient to shift the differentiation potential in the direction of adipogenic. We thus investigated differentiating hMSCs and the mesenchymal stem cell line SCP-1 cultured under osteogenic conditions and stimulated with supra-physiological cortisone levels. The release of active cortisol into the medium was monitored and the influence on cell differentiation analyzed. We revealed an increase in 11ß-HSD1 expression followed by increased reductive activity of the enzyme, thereby inducing a more adipogenic phenotype of the cell models via cortisol with negative effects on osteogenesis. Through inhibition experiments with the specific inhibitor 10 j, we proved the enzyme specificity for cortisol synthesis and adipogenic differentiation. Increased expression of 11ß-HSD1 followed by higher cortisol levels might thus explain bone marrow adiposity followed by reduced bone quality and stability in old age or in situations of supra-physiological glucocorticoid exposure.

Crohn's disease patient serum changes protein expression in a human mesenchymal stem cell model in a linear relationship to patients' disease stage and to bone mineral density.

BACKGROUND: Crohn's disease (CD) is associated with a higher prevalence of osteoporosis, a complication that is recognized as a significant cause of morbidity. Its pathogenesis is controversial, but the activity of CD is one contributing factor. METHODS: We stimulated SCP-1 cells (mesenchymal stem cell line) under osteogenic conditions with serum from adult patients with CD in the symptomatic phase (SP) and in remission (R) and with control sera. Concentrations of IL-6, IL-1 beta, and TNF alpha in the sera were measured. Patients were classified as normal or osteopenic/osteoporotic based on bone mineral density (BMD) T-score measurements. After 14 days in culture, protein expression and gene ontology (GO) annotation analysis was performed. RESULTS: Cytokine concentrations (IL-6, IL-1 beta, TNF alpha) varied within sera groups. None of the cytokines were significantly increased in the symptomatic phase compared to remission. Protein analysis revealed 17 proteins regulated by the SP versus R phase sera of disease. A linear relationship between CDAI (Crohn's disease activity index) and normalized protein expression of APOA1 and 2, TTR, CDKAL1 and TUBB6 could be determined. Eleven proteins were found to be differentially regulated comparing osteoporosis-positive and osteoporosis-negative sera. Gene annotation and further analysis identified these genes as part of heme and erythrocyte metabolism, as well as involved in hypoxia and in endocytosis. A significant linear relationship between bone mineral density and normalized protein expression could be determined for proteins FABP3 and TTR. CONCLUSION: Our explorative results confirm our hypothesis that factors in serum from patients with CD change the protein expression pattern of human immortalized osteoblast like cells. We suggest, that these short time changes indeed influence factors of bone metabolism.

IL-6, IL-1ß, and TNF-α only in combination influence the osteoporotic phenotype in Crohn's patients via bone formation and bone resorption.

BACKGROUND: Crohn´s disease (CD) is associated with a higher prevalence of osteoporosis. The pathogenesis of bone affliction remains controversial, especially if inflammatory cytokines or glucocorticoid therapy are the main contributors. In postmenopausal osteoporosis, bone resorption is induced by IL-6, IL-1ß and TNF-α. In contrast, in children with CD, IL-6 exclusively decreased bone formation without affecting bone resorption. OBJECTIVES: The objective of this study was to further clarify the pathophysiology of bone affliction in adult patients with CD with the use of an osteoblast and osteoclast cell model. MATERIAL AND METHODS: Inflammatory cytokines IL-6, IL-1ß, and TNF-α were measured in adult CD patients' serum. Mean values of these cytokines were applied with or without dexamethasone to the human cell line SCP-1 (osteoblastic cell model). Also, the effect of cytokines on primary human osteoclast differentiation and activity was determined. RESULTS: The combined cytokine application increased the receptor activator of NF-κB ligand/osteoprotegerin (RANKL/OPG) ratio 2-fold after 2 and 14 days. Additional application of dexamethasone to SCP-1 cells further increased the RANKL/OPG ratio 3-fold, but decreased IL-6 and IL-1ß expression to 10% and 50%, respectively. TNF-α expression was maximally suppressed to 16% by dexamethasone in the presence of cytokines. In osteoclasts, the combined cytokine treatment decreased expression of characteristic genes to approx. 30%, while increasing osteoclast resorption activity to 148%. In addition, a cytokine stimulated osteoblast cell culture-generated supernatant stimulated osteoclast resorption activity by 170%. CONCLUSIONS: Our results suggest that IL-6, IL-1ß, and TNF-α only in combination induced osteoclaststimulating activity represented by the RANKL/OPG ratio in osteoblasts. Dexamethasone further increased this effect in osteoblasts, while decreasing cytokine expression. The results in osteoclasts support a direct and osteoblast-mediated effect on bone resorption. Our in vitro results differentiate for the first time the effect of cytokines on bone turnover as measured in adult CD patients from the additional dexamethasone effect on osteoblasts as part of the pathophysiology of osteoporosis.

Genetic polymorphisms in 11ß-hydroxysteroid dehydrogenase type 1 correlate with the postdexamethasone cortisol levels and bone mineral density in patients evaluated for osteoporosis.

CONTEXT: Higher physiological cortisol levels may increase the risk of age-related osteoporosis. We hypothesized that common polymorphisms in the cortisol synthesis enzyme 11ß-hydroxysteroid dehydrogenase (HSD11B) may cause interindividual variations in cortisol levels and age-related bone loss. STUDY DESIGN AND PATIENTS: We performed a retrospective study in a cohort of 452 ambulatory patients under evaluation for osteoporosis. We investigated the associations of 16 single-nucleotide polymorphisms (in the HSD11B1 and HSD11B2 genes with a postdexamethasone cortisol (PDC) level and bone mineral density (BMD; primary end points) and fracture risk (secondary end point) in a subgroup of 304 patients. The observed associations with BMD were validated in a subgroup of 148 patients. RESULTS: The PDC level increased with age (R = 0.274, P < 10(-5), n = 287) and was negatively correlated with BMD at the femoral neck (R = -0.278, P < 10(-5), n = 258). Three genetically linked single-nucleotide polymorphisms (in intron 5 of HSD11B1), rs1000283, rs932335, and rs11811440, were significantly associated with BMD, with rs11811440 having the strongest association. The presence of the minor rs11811440 A allele was correlated with a lower PDC level (R = -0.128, P = .03, n = 304). The A allele was also consistently correlated with a higher spinal BMD in both patient subgroups (R = 0.17, Bonferroni corrected P = .006, n = 452). The correlation with BMD remained significant after adjustment for age, gender, body mass index, and type of osteoporosis and was stronger in patients older than 65 years. CONCLUSION: Genetic variations in HSD11B1 may affect the physiological cortisol levels and the severity of age-related osteoporosis. Underlying functional mechanisms remain to be elucidated.