Osteoprotegerin and the receptor activator of NF-kappa B ligand in the serum and synovial fluid. A comparison of patients with longstanding rheumatoid arthritis and osteoarthritis

We examined OPG and soluble RANKL in the serum (sOPG, sRANKL) and synovial fluid (synOPG, synRANKL) in patients with rheumatoid arthritis (RA) and osteoarthritis (OA). OPG and RANKL were measured in 85 patients (44 with RA, 41 patients with OA) in serum and synovial fluid as well. For measuring of OPG and RANKL ELISA tests were used. The results of OPG and RANKL were compared with clinical and radiological scores. We found a negative correlation for OPG and RANKL in synovial fluids: not only for the whole group of patients (P< 0.003, r=–0.32), but also for the subgroups (RA: P<0.04, r=–0.28, OA: P<0.002, r=–0.54). SRANKL and synRANKL were positively correlated in the whole group (P<0.01, r=0.25) and in the OA group (P<0.02, r=0.35); the RA group was showing a trend (P<0.063, r=0.24), however. Serum OPG was lower in RA, synOPG higher in OA. The difference between the two patient groups was only significant for synOPG (P<0.03, r=0.056), but not for sOPG (P<0.09, r=0.19), sRANKL (P<0.43, r=0.85) or synRANKL (P<0.11, r=0.22). The synOPG:synRANKL ratio was significantly correlated with the Larsen score (P<0.004, r=0.38). Synovial OPG is significantly decreased in rheumatoid joints, whereby synovial RANKL is increased. Lower synOPG could reflect a lower protective effect on bone, thus leading to an earlier and more pronounced bone destruction in RA. However, the effect of different mediators for joint destruction in RA and OA seems not to be important to the pathophysiological changes in the joints. The upregulation of serum OPG might be the result of the inflammation; in contrast, an upregulation of RANKL could not be found in the serum of patients with RA and OA.     

sRANKL and OPG in serum and synovial fluid of patients with rheumatoid arthritis in comparison to non-destructive chronic arthritis

The aim of this study was to investigate sRANKL and OPG levels in serum and synovial fluid (SF) and to evaluate their relations in patients with RA in comparison to those with non-erosive arthritis (NEA). The study included 45 unselected RA patients with knee joint effusions and 27 patients with knee joint effusions because of NEA. Serum and SF samples were investigated isochronously. OPG and sRANKL were measured by ELISA assays. In RA, sRANKL levels were higher in serum than in SF (P = 0.007). In contrast, the NEA revealed higher sRANKL in SF compared to the serum (P = 0.001). Though in RA the average levels of sRANKL_ser were 5.6 times and of sRANKL_syn 1.5 times higher than in NEA, the differences were not significant. The free (unbound) OPG in SF was not significantly different in RA compared to NEA. Also in serum, the measured free OPG was only slightly higher in RA. There were no significant differences between RA and NEA concerning ESR and CRP. Significant correlations could be found between sRANKL_syn and CRP (r = 0.453; P = 0.005) as well as ESR (r = 0.362; P = 0.033) in RA. Nearly a positive correlation was evident also between sRANKL_syn and CRP in NEA (r = 0.520; P = 0.08). RA and NEA differ in particular concerning their power and intensity to destruct the juxtaarticular bone. This is the most remarkable finding of this study, that in RA a high part of sRANKL seems to be OPG bound and cleared by the blood stream, but the sRANKL neutralizing capacity of produced OPG in opposite to NEA is not sufficient to prevent osteoclast activation and bone destruction in the RA joint.     

The imbalance between osteoprotegerin and cathepsin K in the serum of patients with longstanding rheumatoid arthritis

Osteoprotegerin (OPG) and soluble receptor activator of NF-kappa B ligand (sRANKL) together regulate the bone metabolism among other cytokines, whereby cathepsin K has a potent collagen-degrading activity. An imbalance of this system may be partly responsible for the skeletal complications of RA. Expanding on a previous study, we investigated the relationship between OPG, sRANKL and cathepsin K levels in the serum of patients with longstanding RA. We measured serum levels of OPG, sRANKL and cathepsin K of 100 patients with active, longstanding RA. We detected elevated serum levels of cathepsin K (median 54.8 pmol/l) and OPG (median 4.8 pmol/l), but normal sRANKL levels (median 0.2 pmol/l). Cathepsin K did not show a correlation with the overexpressed OPG (P = 0.64) and sRANKL (P = 0.81). The radiological destruction correlates significantly with cathepsin K (P = 0.004) and OPG (P = 0.007). We speculate that the increased levels of OPG are effective in compensating the action of sRANKL, but do not directly prevent bone degradation, as reflected by the elevated serum levels of cathepsin K.     

Circulating osteoprotegerin and soluble RANK ligand in systemic sclerosis

OBJECTIVE: .Microvascular damage is an early pathogenetic event in systemic sclerosis (SSc). The receptor activator of nuclear factor-kappaB ligand (RANKL)/RANK/osteoprotegerin (OPG) system is involved in vascular biology. Our aim was to assess OPG and soluble RANKL (sRANKL) serum levels in patients with SSc and healthy controls. METHODS: Sixty patients with SSc (median age 58, range 31-72 yrs) and 60 healthy subjects matched for age, sex, and menopausal status were recruited. Serum OPG, sRANKL, soluble vascular cell adhesion molecule (sVCAM; marker of endothelial activation/injury), and bone turnover markers were measured. Bone mineral density in patients was assessed and cardiovascular/coronary risk was estimated. RESULTS: OPG was similar in the 2 groups, while sRANKL and sRANKL/OPG ratio was higher in patients (p = 0.01 for both). sVCAM was markedly higher in patients (p < 0.001). OPG levels correlated positively with age in both patients (Spearman R = 0.50, p < 0.001) and controls (R = 0.56, p < 0.001). In patients, OPG was lower in men and higher in those with active ulcers or calcinosis. sRANKL levels were higher in patients treated with platelet aggregation inhibitors, and correlated negatively with densitometric measures. 25-hydroxyvitamin D levels were significantly lower in patients (p < 0.001). In patients, OPG levels correlated positively with cardiovascular and coronary risk (R = 0.28, p = 0.05 and R = 0.34, p < 0.01, respectively) and were higher in patients with hypertension and left ventricular hypertrophy. sVCAM levels correlated positively with cardiovascular and coronary risk (R = 0.27, p = 0.06, and R = 0.38, p < 0.01, respectively). CONCLUSION: Higher sRANKL levels and sRANKL/OPG ratio in patients with SSc are likely to be a consequence of altered bone microenvironment. We show a dissociation between the well established marker of endothelial activation/injury, sVCAM, and the alleged marker of vascular damage, OPG, in patients with SSc. Further studies are needed to better ascertain the relationships of the RANKL/RANK/OPG system with the progression of macro- and microvascular damage.     

血液透析患者骨保护素细胞核因子кB受体活化因子配体与动脉僵硬度的关系

目的探讨血液透析患者颈-股脉搏波速度(CFPWV)和颈-桡脉搏波速度(CRPWV)的变化及与骨保护素(OPG)、细胞核因子кB受体活化因子配体(sRANKL)系统的关系。方法对北京大学人民医院血液净化中心2006年6—10月40例血液透析患者采用酶联免疫吸附法测定血清OPG、sRANKL,PWV测定仪测定外周动脉僵硬度,X线平片检测腹主动脉、股动脉及桡动脉部位血管钙化,计算血管钙化积分。结果 25例(64.1%)患者存在不同程度的血管钙化,中重度钙化者较轻度钙化者血清OPG高[(342.50±171.53)ng/L对(206.21±137.88)ng/L,P=0.025]、OPG/sRANKL比值高(454.65±455.63比135.31±136.81,P=0.035),sRANKL比较差异无统计学意义[(0.10±0.08)pmol/L对(0.12±0.08)pmol/L]。血液透析患者CRPWV及CFPWV均较对照组增高,差异有统计学意义[(9.48±1.80)m/s对(8.58±1.29)m/s,P=0.043]和[(13.42±3.26)m/s对(10.07±1.76)m/s,P<0.01]。血OPG较对照组高[(235.12±154.33)ng/L对(93.00±44.10)ng/L,P=0.01],sRANKL两组比较,差异无统计学意义[(0.12±0.08)pmol/L对(0.16±0.08)pmol/L]。相关分析发现CRPWV与舒张压、sRANKL呈正相关(r=0.389、0.349,P=0.025、0.040),控制年龄、血压因素后CRPWV仍然与sRANKL呈正相关(r=0.381,P=0.029)。多元线性回归分析显示血磷、sRANKL及钙磷乘积是CRPWV的独立影响因素,年龄是CFPWV的独立影响因素。结论血液透析患者外周动脉僵硬度增加,sRANKL独立于年龄和血压影响血液透析患者动脉僵硬度。     

The RANKL/OPG system and bone mineral density in patients with chronic liver disease

BACKGROUND/AIMS: Osteopenia and osteoporosis are common complications of chronic liver disease (CLD). Receptor activator of nuclear factor kappaB ligand (RANKL) and osteoprotegerin (OPG) regulate osteoclastogenesis and bone remodelling, and are involved in several inflammatory diseases. This study investigated the activation state of the RANKL/OPG system and its association with bone loss in CLD. METHODS: Serum levels of OPG and sRANKL were determined in 193 patients with CLD and 56 age- and gender-matched healthy controls. Cellular sources of OPG and RANKL were determined immunohistochemically. Dual-energy x-ray absorptiometry was performed to determine bone mineral density (BMD) of lumbar spine and femoral neck. RESULTS: sRANKL serum levels were significantly elevated in non-cirrhotic, but not cirrhotic patients compared to healthy controls. OPG serum levels were elevated 1.6-fold in non-cirrhotic and 2.8-fold in cirrhotic CLD patients. RANKL+ cells were mainly confined to portal fields, while OPG was broadly expressed. In the cirrhotic subgroup (87 patients) we observed a significantly higher OPG/sRANKL ratio in patients with osteopenia or osteoporosis of the lumbar spine and femoral neck region (T-score < -1) compared to those with normal BMD (T-score > or = -1). CONCLUSIONS: CLD is associated with alterations in RANKL/OPG serum levels, which could modulate bone loss in CLD.     

Serum osteoprotegerin is increased in Crohn's disease: a population-based case control study

BACKGROUND: There is a potential interface between osteoporosis and the chronic inflammation of inflammatory bowel disease (IBD), and the osteoprotegerin (OPG)/receptor for activated nuclear factor-kappaB (RANK)/RANK ligand (RANKL) signaling pathway may be an important mediator, although data are limited. METHODS: We conducted a population-based case-control seroassay study to look for alterations in serum OPG and soluble RANKL (sRANKL). The study population included IBD patients who were 18 to 50 years old with Crohn's disease (CD; n = 287) or ulcerative colitis (UC; n = 166), age-matched healthy controls (n = 368), and nonaffected siblings of IBD patients (n = 146). Serum OPG and sRANKL were measured by enzyme-linked immunoassay. Sex-specific reference ranges were derived from the healthy controls. RESULTS: Analysis of variance (ANOVA) confirmed significant group differences in women for mean serum OPG (P = 0.018). CD women had higher values of OPG than UC women (P = 0.028) or healthy controls (P = 0.045), whereas the other groups were similar. OPG levels were above the reference range in 13/173 (8%) of CD women, exceeding the expected proportion (P = 0.032). In contrast, no differences in OPG were seen in men between controls, CD, or UC. Estrogen use in women (P = 0.000002) and corticosteroid use in men (P = 0.026) were associated with higher OPG levels. In multivariate analysis, CD diagnosis (P = 0.031) and estrogen use (P = 0.000002) were independently associated with higher OPG levels. No group differences were seen in mean serum sRANKL measurements. CONCLUSIONS: An OPG:sRANKL imbalance with OPG exceeding sRANKL should inhibit osteoclastogenesis and promote bone formation. CD is associated with increased fracture risk, and possibly, the paradoxically higher OPG is a counterregulatory response to factors such as inflammatory cytokines, promoting high bone turnover. Alternatively, elevated OPG in CD may reflect T-cell activation.     

Effects of oral contraceptives on circulating osteoprotegerin and soluble RANK ligand serum levels in healthy young women

OBJECTIVE: Osteoprotegerin (OPG) represents a secreted cytokine which regulates bone mass by blocking receptor activator of nuclear factor-kappaB ligand (RANKL), the principal regulator of osteoclast function. In vitro, OPG production is upregulated by oestrogens in osteoblastic lineage cells, a mechanism that has been discussed as a protective paracrine mechanism of oestrogens on the skeleton. To define the effects of oestrogens on the RANKL/OPG system in vivo, we evaluated OPG and both free and total soluble RANKL (sRANKL) serum levels in healthy young women with or without oral contraceptives. DESIGN AND PATIENTS: Serum levels of OPG and sRANKL were prospectively assessed in a cohort of healthy young women with (n = 30) or without (n = 25) combined oestrogen-progestin-based oral contraceptives. MEASUREMENTS: OPG, total and free sRANKL serum levels were determined by enzyme-linked immunosorbent assays (ELISA). RESULTS: In women using oral contraceptives, OPG serum levels were significantly higher (2.71 +/- 1.42 pmol/l) compared to nonusers (1.35 +/- 1.02 pmol/l; P = 0.0003), whereas free (P = 0.55) and total (P = 0.24) sRANKL serum levels did not differ between both groups. This resulted in an increased OPG/free sRANKL ratio (P = 0.02) in women on oral contraceptives. During the ovarian cycle, OPG (P = 0.22) and free sRANKL (P = 0.99) serum levels remained unchanged in women without oral contraceptives (n = 19), while total sRANKL levels were higher in the follicular than in the luteal phase (P = 0.02). CONCLUSIONS: Intake of oral contraceptives is associated with increased OPG serum levels, but not sRANKL levels, resulting in a higher OPG/sRANKL ratio. This may contribute to the positive effects of oral contraceptives on the skeleton.     

Serum sRANKL/OPG predict recurrence after radiofrequency catheter ablation of lone atrial fibrillation

Background

Radiofrequency catheter ablation (RFCA) is a widely accepted strategy for eliminating atrial fibrillation (AF). A considerable recurrence rate has partly been ascribed to atrial remodeling. Osteoprotegerin (OPG)/receptor activator of nuclear factor-κB (RANK)/RANK ligand (RANKL) axis may contribute to the development and progression of AF by regulating atrial structural remodeling. This study aimed to determine the relationship between serum soluble RANKL (sRANKL)/OPG and the risk of recurrent arrhythmia after ablation of lone AF.

Methods

We enrolled 527 lone AF patients undergoing first-time RFCA with complete follow-up data. Pre-ablation venous blood samples were obtained for measurement of serum sRANKL and OPG.

Results

During the follow-up period of 15 (3–64) months, AF recurred in 187 patients (35.5%). Recurrence was associated with an elevation of serum sRANKL level and sRANKL/OPG ratio. In multivariate survival regression, persistent AF, AF duration, left atrial diameter, amiodarone after ablation, particularly serum sRANKL level and sRANKL/OPG ratio independently predicted AF recurrence. According to ROC curve analysis, the best diagnostic values of serum sRANKL level and sRANKL/OPG ratio for predicting recurrence were 4.89 pmol/l and 0.76, respectively.

Conclusions

Baseline serum high sRANKL level and sRANKL/OPG ratio are associated with AF recurrence after primary ablation procedure in lone AF patients, and may be used in the prediction of AF recurrence in these patients.     

The role of the receptor activator of nuclear factor-kappaB ligand/osteoprotegerin cytokine system in primary hyperparathyroidism

CONTEXT: The mechanisms of action of PTH on bone in vivo remain incompletely understood. The objective of this investigation was to examine changes in serum levels of receptor activator of nuclear factor-kappaB ligand and osteoprotegerin (OPG) in primary hyperparathyroidism and their relationship to bone loss. PATIENTS AND METHODS: Twenty-nine patients with primary hyperparathyroidism had baseline circulating soluble receptor activator of nuclear factor-kappaB ligand (sRANKL) and OPG measured. The relationship to biochemical markers of bone turnover and changes in bone mineral density over 2 yr was examined. RESULTS: Baseline sRANKL levels were elevated (1.7+/-0.1 pmol/liter), whereas OPG remained in the normal range (5.6+/-0.4 pmol/liter). Circulating sRANKL did not correlate with PTH but did correlate with markers of bone resorption (urine deoxypyridinoline cross-links: r=0.51, P<0.01; serum N-telopeptide of type I collagen: r=0.37, P<0.05). Furthermore, sRANKL correlated with both IL-6 and IL-6 soluble receptor (IL-6sR) (r=0.47, P<0.05 and r=0.55, P<0.005, respectively). Serum sRANKL levels also correlated with bone loss at the total femur (r=-0.53, P<0.01). Lastly, a high value of sRANKL in combination with values of IL-6 and IL-6sR in the upper quartile (sRANKL>or=1.81 pg/ml, IL -6>or=11.8 pg/ml, and IL-6sR>or=45.6 ng/ml) defined a group of four women with significantly greater rates of bone loss at the total femur than the remaining patients (-2.7+/-1.7% vs. +0.5+/-0.3%; n=4 vs. n=19, P<0.05). CONCLUSION: Determination of circulating levels of sRANKL may be useful in identifying patients with mild primary hyperparathyroidism at greater risk for bone loss. The fact that circulating sRANKL did not correlate with PTH but did correlate with markers of bone resorption suggests that skeletal responsiveness to PTH may differ in this disease.     

强直性脊柱炎继发骨质疏松及相关因素分析

目的 测定强直性脊柱炎(AS)患者骨密度(BMD)、血清骨保护素(OPG)、可溶性核因子κB受体活化因子配体(sRANKL)等骨代谢指标及外周血T细胞表面RANKL表达情况,研究RANKI/RANK/OPG系统在AS骨代谢中的作用.方法 双能X线吸收法(DEXA)测定AS患者BMD;酶联免疫吸附试验(ELISA)法检测血清OPG、sRANKL、抗酒石酸酸性磷酸酶异构体5b(TRACP-5b)、骨特异性碱性磷酸酶(BALP)水平;分析BMD、上述骨代谢指标及临床指标间相关性;流式细胞术(FC)检测外周血CD4+/RANKL+及CD8+/RANKL+细胞表达率;分析它们与红细胞沉降率(ESR)、C反应蛋白(CRP)相关性.计量资料采用成组设计的t检验,计数资料采用x2检验,相关性采用直线相关分析.结果 ①AS患者骨量减少、骨质疏松(OP)发生率分别为47%、37%.②AS组血清sRANKL、TRACP-5b水平及sRANKL/OPG比值均高于对照组(P<0.05);2组血清OPG、BALP水平差异无统计学意义.③AS组血清sRANKL水平与OPG呈正相关,两者均与TRACP-5b呈正相关(P<0.01.④AS组外周血CD4+/RANKL+细胞表达率高于对照组(P<0.05).结论 AS存在较高的骨量丢失率,其骨代谢特点以骨吸收增强为主,RANKL/RANK/OPG系统在其中起着重要作用,该系统失衡可能是AS骨量丢失机制之一;CD4+T细胞可能通过上调RANKL表达参与AS破骨细胞分化成熟及骨吸收机制.     

Effects of the phytoestrogen genistein on the circulating soluble receptor activator of nuclear factor kappaB ligand-osteoprotegerin system in early postmenopausal women

We investigated the serum levels of both receptor activator of nuclear factor kappaB ligand (RANKL) and its decoy receptor osteoprotegerin (OPG) in postmenopausal healthy women after a 1-yr therapy with genistein, (n = 30; 54 mg/d), hormone replacement therapy (n = 30; 1 mg/d 17beta-estradiol combined with norethisterone acetate) and placebo (n = 30). By comparison with placebo, the soluble RANKL (sRANKL)/OPG ratio was lower in the genistein group (-69 +/- 7%; P < 0.01 vs. placebo 81 +/- 24%) and in hormone replacement therapy-treated women (-11 +/- 2%; P < 0.01 vs. placebo). A positive correlation (r = 0.63; P < 0.01) was found between 1-yr percentage change in sRANKL/OPG ratio and 1-yr change in urinary deoxypyridinoline, a bone resorption marker. A negative correlation was observed between 1-yr percentage change in sRANKL/OPG ratio and 1-yr change in femoral neck bone mineral density (r = -0.7; P < 0.01). Our findings suggest that the sRANKL-OPG system may mediate the beneficial effects of genistein on bone remodeling in postmenopausal women.     

Serum osteoprotegerin and its ligand in cirrhotic patients referred for orthotopic liver transplantation: relationship with metabolic bone disease.

AIMS: A prospective study was carried out in 22 cirrhotic patients referred for orthotopic liver transplantation, in order to analyze serum osteoprotegerin (OPG) and RANKL levels and their relationship with metabolic bone disease. METHODS: Serum levels of OPG and RANKL were measured in all patients as well as bone markers, serum parathyroid hormone and 25-hydroxyvitamin D levels. OPG and RANKL values were compared with those obtained in 29 healthy controls. Bone mineral density (BMD) of the lumbar spine and proximal femur was measured by dual X-ray absorptiometry and spinal X-rays were obtained to assess vertebral fractures. RESULTS: Serum OPG levels were higher in cirrhotic patients than in controls (6.4+/-2 vs 2.7+/-0.7 pmol/l; P=0.001) and RANKL serum levels were lower in cirrhotic patients (0.215+/-0.6 vs 1.012+/-1.2 pmol/l; P=0.002), with an increased OPG:RANKL ratio when compared with the control group (280.3+/-334.5 vs 113+/-137.6; P=0.04). Ten patients had osteoporosis (45%) and up to 45% skeletal fractures. No differences were found in OPG levels between patients with and without osteoporosis by densitometric criteria or fractures. Negative correlations were found between OPG levels and femoral neck (R-0.46; P=0.03) and total hip BMD (R-0.48; P=0.025). By contrast, OPG values were not related to markers of bone turnover. CONCLUSIONS: OPG values are elevated in cirrhotic patients before liver transplantation, particularly in those with low bone mass at the proximal femur.     

Circulating RANKL/OPG in polymyalgia rheumatica

OBJECTIVE: To evaluate whether RANKL/OPG balance is modified in PMR patients, either in the active phase of the disease or during corticosteroid treatment. METHODS: Circulating levels of RANKL and OPG were assayed by enzyme-linked immunosorbent assay in PMR patients with active untreated disease and in patients treated by corticosteroids over a 12-month follow-up period. RESULTS: We found no statistically significant differences in circulating levels of OPG between PMR patients either in the active phase of the disease or during all follow-up period compared to normal controls. On the other hand, systemic production of sRANKL is increased and is not modulated by corticosteroid treatment. CONCLUSION: In PMR increased levels of sRANKL may be related to bone osteoporosis. Further investigations are necessary to evaluate the relationship between the RANK/RANKL/OPG system and bone turnover in PMR patients.     

Osteoprotegrin interacts with biomarkers and cytokines that have roles in osteoporosis,skin fibrosis,and vasculopathy in systemic sclerosis: A potential multifaceted relationship between OPG/RANKL/TRAIL and Wnt inhibitors

Abstract

Objectives: We explored the interactions of osteoprotegerin (OPG) with biomarkers of bone turnover and cytokines, including soluble receptor activator for nuclear factor kappa beta ligand (sRANKL), tumor necrosis factor-related apoptosis-induced ligand (TRAIL), and Wnt inhibitors in osteoporosis, vasculopathy and fibrosis related to systemic sclerosis (SSc).

Methods: The study included 46 SSc patients and 30 healthy controls. Skin thickness, pulmonary fibrosis and/or hypertension, digital ulcers, and calcinosis cutis of SSc patients were assessed. We determined bone mineral density (BMD), and OPG, sRANKL, TRAIL, secreted frizzled-related protein 1 (sFRP-1), Dickkopf-related protein 1 (DKK-1), sclerostin in the serum of both patients and controls.

Results: OPG, sclerostin, and sFRP-1 levels were similar between patients and controls (P?>?0.05). Femoral neck and lumbar spine BMD and vitamin D levels were lower, and the OC, NTX, sRANKL, DKK1 and TRAIL levels were significantly higher, in patients than in controls (p?<?0.05). In subgroup analysis, patients with higher modified Rodnan skin score (mRodnan) had higher DKK-1, sclerostin, and TRAIL levels (p?<?0.05); those with diffuse SSc subtype had lower BMD values than those with limited SSc (p?<?0.05). Skin and pulmonary fibrosis linked negatively with BMD measures.

Conclusion: we showed that sRANKL levels were higher and correlated with bone turnover markers. It may be related to osteoporosis in SSc. The OPG level was unaltered in SSc patients. Higher TRAIL levels associated with skin thickness may indicate vascular dysfunction or injury. Higher DKK-1 and sclerostin levels may be related to a reactive increase in cells and be prominently linked to fibrosis in SSc.     

The RANKL/OPG system is activated in inflammatory bowel disease and relates to the state of bone loss

BACKGROUND AND AIMS: A substantial proportion of patients with inflammatory bowel disease (IBD) develops osteopenia and osteoporosis in the course of disease. Recent data from a mouse model of colitis suggest that the receptor activator of nuclear factor kappa B (RANKL)/osteoprotegerin (OPG) system may be responsible for bone loss. METHODS: We investigated the activation state of the RANKL/OPG system and its association with bone loss in human IBD. Plasma levels of OPG and RANKL were correlated with bone mineral density and current IBD therapy. Colonic secretion of OPG and RANKL and cell types responsible for such secretion were determined. RESULTS: OPG plasma levels were elevated 2.4-fold in Crohn's disease (CD) and 1.9-fold in ulcerative colitis (UC) whereas soluble RANKL (sRANKL) levels were not significantly different in IBD patients compared with healthy controls. High levels of OPG were released from colonic explant cultures (CEC) derived from inflamed IBD specimens, and colonic macrophages and dendritic cells costained for OPG. sRANKL levels from CEC were low both in IBD patients and healthy controls. Interestingly, increased expression of RANKL was mainly confined to cells in the lamina muscularis. A significant negative correlation was found between OPG plasma levels and femoral neck/lumbar spine bone mineral density. CONCLUSIONS: We have demonstrated that IBD is associated with alterations in the RANKL/OPG system. Applying results from a murine model of colitis associated bone loss, the constellation of OPG and sRANKL regulation observed in our study raises the possibility that RANKL/OPG may contribute to the development of bone loss in IBD.     

Relationship between RANKL and neuroendocrine activation in elderly males with heart failure

The main cytokines regulating bone remodeling are the receptor activator of nuclear factor-κB ligand (RANKL) and its decoy receptor, osteoprotegerin (OPG). Recent data have linked RANKL and OPG to cardiovascular disease as well. NT-pro-BNP and adiponectin are well-established biomarkers of heart failure reflecting neuroendocrine activation in this multi-complex disorder. The objective of this article was to investigate whether RANKL is associated with neuroendocrine activation in 75 elderly males with mild to moderate congestive heart failure (CHF) and left ventricular ejection fraction <40%. The control group consisted of 20 healthy male volunteers with matching age and body mass index (BMI). Serum RANKL (sRANKL), OPG, NT-pro-BNP, adiponectin, leptin, clinical, and echocardiography parameters were evaluated. In comparison to the control group, the CHF patients showed significantly increased sRANKL levels [126.8 (122.6) vs. 47.8 (44.4) pg/ml, P < 0.0001]. There was a significant relative risk of systolic CHF in elderly males associated with increased sRANKL above the calculated cut-off of 83 pg/ml [OR = 10.286 (95%CI 3.079-34.356), P < 0.0001; RR = 3.600 (95%CI = 1.482-8.747)]. In the CHF patients, the log-transformed values of sRANKL levels correlated positively with the log-transformed values of the serum NT-pro-BNP and adiponectin levels (P = 0.004, r = 0.326 and P = 0.037, r = 0. 241, respectively), while inversely correlated with the BMI and creatinine clearance (P = 0.015, r = -0.281 and P = 0.042, r = -0.236, respectively). In multivariate regression model, sRANKL was a significant determinant of NT-pro-BNP independent of age, BMI and creatinine clearance (P = 0.002, R (2) = 0.546). In conclusion, our study suggests that in elderly males with systolic heart failure sRANKL was significantly associated with parameters of neuroendocrine activation such as NT-pro-BNP and adiponectin. Further studies are needed to elucidate the potential role of sRANKL in the complex pathogenesis of heart failure.     

Circulating levels of receptor activator of nuclear factor-kappaB ligand/osteoprotegerin/macrophage-colony stimulating factor in a presumably healthy human population

OBJECTIVES: To determine the ranges of variation of circulating receptor activator of nuclear factor-kappaB ligand (RANKL)/osteoprotegerin (OPG)/macrophage-colony stimulating factor(M-CSF) and to ascertain their potential relationships with age, sex and menopausal status in women, and with sex hormones in a population-based healthy cohort. SUBJECTS AND METHODS: Blood samples were collected with EDTA after an overnight fast. The plasma levels of each of the above biochemical indices were measured by ELISA in a total of 566 apparently healthy individuals aged 18-75 years. RESULTS: The plasma concentrations of cytokine molecules in the entire sample ranged from 674 to 4929 pg/ml for OPG, from 105 to 4468 pg/ml for soluble RANKL (sRANKL), and from 187 to 7604 pg/ml for M-CSF. The OPG levels demonstrated a clear positive correlation with age in both sexes (r=0.42 and 0.43, P<0.001, for men and women respectively). Application of the two-interval mathematical model revealed that in females OPG levels were age-independent until age 42, but then showed clear and significant correlation with age (r=0.48, P<0.001). As a result, young females (before 42 years) had a substantially lower average OPG level, 1377.8+/-327.68 pg/ml, in comparison with older women, 1666.02+/-397.14 pg/ml. The M-CSF correlation with age was significantly greater in women (r=0.29, P<0.001) compared with men (r=0.17, P<0.01). Significant negative correlations between plasma levels of both OPG and M-CSF with estradiol concentrations were observed in women (r=-0.39, P<0.01; r=-0.25, P<0.001 respectively). sRANKL did not correlate with either age or sex hormones in either women or men. CONCLUSION: Age and sex affect differently the interindividual variation of OPG, RANKL and M-CSF. Our observations could form the basis for further research to establish provisional reference limits for OPG and RANKL, which are potential markers for benign and malignant processes in bone.     

Association Between Indoxyl Sulfate and Skeletal Resistance in Hemodialysis Patients

Skeletal resistance to parathyroid hormone (PTH) in uremia is known, although the mechanism of resistance is not fully elucidated. To clarify the roles of indoxyl sulfate, which is a uremic toxin, in skeletal resistance, we examined the relationship between indoxyl sulfate and biochemical markers of bone turnover in hemodialysis patients. We obtained blood samples from 47 hemodialysis patients and measured serum indoxyl sulfate, intact PTH, oxidative stress marker 8-hydroxy-2′-deoxyguanosine (8-OHdG), and various biochemical markers. The serum concentrations of alkaline phosphatase (ALP) and bone-specific alkaline phosphatase (BAP) were used as bone formation markers, and the concentration of tartrate-resistant acid phosphatase 5b (TRACP-5b) was used as a bone resorption marker. Serum indoxyl sulfate levels were much higher in hemodialysis patients than healthy subjects. Multiple regression analysis shows that indoxyl sulfate correlated negatively with ALP (β = −1.897, P = 0.042) and BAP (β = −0.310, P = 0.029), independent of intact PTH; however, indoxyl sulfate did not correlate with TRACP-5b or 8-OHdG. These findings suggest that indoxyl sulfate may relate skeletal resistance to PTH in uremia.     

Role of receptor activator of nuclear factor-kappa B ligand (RANKL), osteoprotegerin and macrophage protein 1-alpha (MIP-1a) in monoclonal gammopathy of undetermined significance (MGUS)

The aim of this study was to evaluate the role of markers of bone remodelling, and osteoclast activation/function in patients with monoclonal gammopathy of undetermined significance (MGUS). We have measured serum levels of soluble RANKL (sRANKL), osteoprotegerin (OPG), macrophage inflammatory protein-1alpha (MIP-1alpha), markers of bone resorption [N-telopeptide of collagen type-I (NTX), and tartrate-resistant acid phosphatase isoform-5b (TRACP-5b)] and bone formation [bone-alkaline phosphatase (bALP)] in 40 MGUS patients. These parameters were compared with those of 42 newly diagnosed myeloma patients, and 45 healthy, gender- and age-matched controls. MGUS patients had elevated levels of NTX, sRANKL, and sRANKL/OPG ratio compared with controls (P < 0.0001). Furthermore, TRACP-5b, MIP-1alpha and NTX were decreased in patients with MGUS compared with myeloma patients (P < 0.001), while OPG and bALP were increased (P < 0.001). Serum levels of MIP-1alpha, as well as TRACP-5b, and sRANKL/OPG ratio were reduced, while bALP was increased in MGUS patients, even when compared with myeloma patients who had stage I/II disease. These results demonstrate that increased osteoclastogenesis leading to increased bone resorption is present in MGUS but seems to be compensated for by normal bone formation, which is absent in MM. Furthermore MIP-1alpha, bALP, and sRANKL/OPG may be useful tools for distinguishing between cases of MGUS and early myeloma.