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

The role of fecal biomarkers in individuals with inflammatory bowel disease

INTRODUCTION

Inflammatory bowel disease (IBD), encompassing Crohn's disease (CD) and Ulcerative Colitis (UC), is a relapsing and remitting condition. Noninvasive biomarkers have an increasingly important role in the diagnosis of IBD and in the prediction of future disease course in individuals with IBD. Strategies for the management of IBD increasingly rely upon close monitoring of gastrointestinal inflammation.

AREAS COVERED

This review provides an update on the current understanding of established and novel stool-based biomarkers in the diagnosis and management of IBD. It also highlights key gaps, identifies limitations, and advantages of current markers, and examines aspects that require further study and analysis.

EXPERT OPINION

Current noninvasive inflammatory markers play an important role in the diagnosis and management of IBD; however, limitations exist. Future work is required to further characterize and validate current and novel markers of inflammation. In addition, it is essential to better understand the roles and characteristics of noninvasive markers to enable the appropriate selection to accurately determine the condition of the intestinal mucosa.

Bone health in inflammatory bowel disease

INTRODUCTION

Inflammatory bowel disease (IBD) is a chronic disease characterized by the presence of systemic inflammation, manifesting not only as gastrointestinal symptoms but also as extraintestinal bone complications, including osteopenia and osteoporosis. However, the association between IBD and osteoporosis is complex, and the presence of multifactorial participants in the development of osteoporosis is increasingly recognized. Unlike in adults, delayed puberty and growth hormone/insulin-like growth factor-1 axis abnormalities are essential risk factors for osteoporosis in pediatric patients with IBD.

AREAS COVERED

This article reviews the potential pathophysiological mechanisms contributing to osteoporosis in adult and pediatric patients with IBD and provides evidence for effective prevention and treatment, focusing on pediatric patients with IBD. A search was performed from PubMed and Web of Science inception to February 2023 to identify articles on IBD, osteoporosis, pediatric, and fracture risk.

EXPERT OPINION

A comprehensive treatment pattern based on individualized principles can be used to manage pediatric IBD-related osteoporosis.

Bone Alterations in Inflammatory Bowel Diseases: Role of Osteoprotegerin

Metabolic bone disorders are one of the most frequent extra-intestinal manifestations in patients with inflammatory bowel diseases (IBD) that might result in an increase of skeletal fragility and risk of fracture. These disorders are a consequence of bone−gut crosstalk alterations, particularly due to inflammation, which involves the RANK-RANKL-Osteoprotegerin (OPG) pathway. This cross-sectional study investigates the role of serum OPG on bone health in IBD patients. In all patients, we carried out BMD measurements at the lumbar spine and femoral neck by the dual-energy X-ray absorptiometry (DXA), and evaluation of serum OPG, 25(OH)D, and PTH. We also divided all IBD patients into two groups: group 1 consisted of premenopausal women and men younger than 50 years old, while group 2 included postmenopausal women and men aged more than 50 years old. We enrolled 36 UC patients (51%), 34 CD patients (49%), and 70 healthy controls. IBD group mean age was 44 ± 17.3 years old, with a mean disease duration of 6 years. IBD patients had a mean value of OPG of 48.1 ± 26.64 pg/mL, while mean OPG in the control group was 61.35 ± 47.19 pg/mL (p < 0.05). In group 1, there was a correlation between BMD Z-scores at the lumbar spine and femoral neck and mean OPG levels in UC subjects (r = 0.47 and r = −0.21, respectively; p < 0.05), and only between Z-score at the lumbar spine and OPG level in the CD group (r = 0.83, p < 0.05). For the patients of group 2, we report a statistically significant correlation between T-score measured at the lumbar site in both UC and CD patients (r = −0.79 and r = 0.77, respectively; p < 0.05). In our study, we demonstrated serum OPG levels to be significantly decreased in IBD subjects compared to healthy age-matched individuals. However, according to our data, it seems that the measurement of serum OPG levels is not useful to better define metabolic bone disorders in IBD patients.

Effect of sequential eradication therapy on serum osteoprotegerin levels in patients with Helicobacter pylori infection and co-existing inflammatory bowel disease

Objective

To investigate the effect of sequential Helicobacter pylori eradication therapy on serum osteoprotegerin levels in patients with H. pylori infection and co-existing inflammatory bowel disease (IBD).

Methods

Three groups of patients were involved in this observational cross-sectional study: IBD (n = 83), H. pylori infection (HP, n = 68), and H. pylori infection with co-existing IBD (HP + IBD, n = 52). These groups were compared with a normal control group (NC, n = 50). Serum osteoprotegerin, serum bone alkaline phosphatase (BALP), and fecal calprotectin (FC) levels were measured.

Results

Serum osteoprotegerin levels were significantly correlated with the simple endoscopic score for Crohn’s disease and Mayo score for ulcerative colitis. The receiver operating characteristic analysis of osteoprotegerin revealed high values for the area under the curve, sensitivity, and specificity. Discriminant analysis illustrated that osteoprotegerin levels significantly differentiated patients with IBD from healthy controls. Osteoprotegerin and FC levels distinguished the IBD and HP + IBD groups from the NC and HP groups.

Conclusions

Sequential eradication therapy did not affect serum osteoprotegerin levels in patients with H. pylori infection and co-existing IBD. Serum osteoprotegerin elevation might be a marker for IBD development in patients with past or current H. pylori infection.

Comprehensive assessment of tissue and serum parameters of bone metabolism in a series of orthopaedic patients

Bone diseases represent an increasing health burden worldwide, and basic research remains necessary to better understand the complexity of these pathologies and to improve and expand existing prevention and treatment approaches. In the present study, 216 bone samples from the caput femoris and collum femoris of 108 patients with degenerative or dysplastic coxarthrosis, hip fracture, or osteonecrosis were evaluated for the proportion of trabecular bone (TB) and expression of parathyroid hormone (PTH) type 1 receptor (PTH1R), osteoprotegerin (OPG), and receptor activator of nuclear factor kappa-B ligand (RANKL). Serum levels of PTH, OPG, soluble RANKL (sRANKL), alkaline phosphatase (AP), osteocalcin, total procollagen type-1 intact N-terminal propeptide (TP1NP), tartrate-resistant acid phosphatase type 5b (TRAP5b), sclerostin, and C-telopeptide of type-1 collagen (ICTP) were also determined. Age was positively correlated with serum levels of PTH, OPG, and sclerostin but negatively associated with TB and sRANKL. Women exhibited less TB, lower sclerostin and ICTP, and higher TRAP5b. Impaired kidney function was associated with shorter bone decalcification time, less TB, lower sRANKL, and higher serum PTH, OPG, and sclerostin. Furthermore, correlations were observed between bone PTH1R and OPG expression and between serum PTH, OPG, and AP. There were also positive correlations between serum OPG and TP1NP; serum OPG and sclerostin; serum AP, osteocalcin, and TRAP5b; and serum sclerostin and ICTP. Serum OPG was negatively associated with sRANKL. In summary, clear relationships between specific bone metabolism markers were observed, and distinct influences of age, sex, and kidney function, thus underscoring their suitability as diagnostic or prognostic markers.

Azathioprine Has a Deleterious Effect on the Bone Health of Mice with DSS-Induced Inflammatory Bowel Disease

Patients with inflammatory bowel disease (IBD) often present poor bone health and are 40% more at risk of bone fracture. Studies have implicated autophagy in IBD pathology and drugs used to treat IBD stimulate autophagy in varying degrees, however, their effect on the skeleton is currently unknown. Here, we have utilised the dextran sulphate sodium (DSS) model of colitis in mice to examine the effects of the thiopurine drug azathioprine on the skeleton. Ten-week-old male mice (n = 6/group) received 3.0% DSS in their drinking water for four days, followed by a 14-day recovery period. Mice were treated with 10 mg/kg/day azathioprine or vehicle control. Histopathological analysis of the colon from DSS mice revealed significant increases in scores for inflammation severity, extent, and crypt damage (p < 0.05). Azathioprine provided partial protection to the colon, as reflected by a lack of significant difference in crypt damage and tissue regeneration with DSS treatment. MicroCT of vehicle-treated DSS mice revealed azathioprine treatment had a significant detrimental effect on the trabecular bone microarchitecture, independent of DSS treatment. Specifically, significant decreases were observed in bone volume/tissue volume (p < 0.01), and trabecular number (p < 0.05), with a concurrent significant increase in trabecular pattern factor (p < 0.01). Immunohistochemical labelling for LC3 revealed azathioprine to induce autophagy in the bone marrow. Together these data suggest that azathioprine treatment may have a deleterious effect on IBD patients who may already be at increased risk of osteoporotic bone fractures and thus will inform on future treatment strategies for patient stratification.

Micronutrient Absorption and Related Outcomes in People with Inflammatory Bowel Disease: A Review

Inflammatory Bowel Disease (IBD) is a chronic disorder associated with immune dysregulation and chronic inflammation of the digestive tract. While it is poorly understood, the role of nutrition and nutrient status in the etiology of IBD and its associated outcomes has led to increased research relating to micronutrient deficiency. This review offers an overview of recent literature related to micronutrient absorption and outcomes in adults with IBD. Although the absorption and IBD-related outcomes of some micronutrients (e.g., vitamin D and iron) are well understood, other micronutrients (e.g., vitamin A) require further research. Increased research and clinician knowledge of the relationship between micronutrients and IBD may manifest in improved nutrient screening, monitoring, treatment, and outcomes for people living with IBD.

Novel Biomarkers and the Future Potential of Biomarkers in Inflammatory Bowel Disease

There is increasing importance placed upon noninvasive assessment of gut inflammation. These tools are likely to be the key in differentiating intestinal inflammatory disease from functional disorders and in monitoring the response to intervention in individuals with known inflammatory conditions. Although various noninvasive markers are currently available, they have limitations and do not provide ideal utility. This review focuses on emerging markers of gut inflammation, highlighting the potential of specific markers.

Inflammatory Bowel Disease in a Rodent Model Alters Osteocyte Protein Levels Controlling Bone Turnover

Bone loss is a common comorbidity of inflammatory bowel disease (IBD), leading to elevated fracture risk in these patients. Inflammatory factors associated with IBD cause increased bone resorption and decreased bone formation with multiple factors implicated as instigators of these alterations. In this project, we examined the influence of IBD on osteocyte proteins in male rats (2 months old) divided into two groups: induced gut inflammation via 2,4,6-trinitrobenzenesulfonic acid (TNBS) enema, and vehicle control. We examined the prevalence of two pro-inflammatory cytokines, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), an anti-inflammatory cytokine, interleukin-10 (IL-10), the anabolic factor insulin-like growth factor-I (IGF-I), osteoclastogenesis regulators RANKL and OPG, and the bone formation inhibitor sclerostin in osteocytes in three bone compartments 4 weeks after initiation of gut inflammation. Histomorphometry of the proximal tibia and fourth lumbar vertebra revealed lower bone volume, lower bone formation rate (BFR), lower osteoid surface (OS), and higher osteoclast surface (Oc.S) with TNBS. Tibial mid-shaft periosteal BFR was also lower with TNBS. Immunohistochemical staining of the distal femur demonstrated that %TNF-α⁺ , %IL-6⁺ , %RANKL⁺ , and %OPG⁺ osteocytes were elevated in cancellous bone in TNBS animals compared to vehicle. These changes were coincident with increased bone resorption. With regression analysis, %RANKL⁺ osteocytes statistically predicted the increase in cancellous Oc.S (R²  = 0.565). Increased %sclerostin⁺ osteocytes observed in the TNBS treatment predicted declines in cancellous OS (R²  = 0.581) as well as BFR in cancellous and cortical bone (R²  = 0.674, R²  = 0.908, respectively). Contrary to our hypothesis, %IGF-I⁺ osteocytes increased in TNBS animals. In conclusion, the IBD model produced a systemic inflammation that altered the regulatory protein profile in osteocytes that control bone resorption and bone formation, likely contributing to IBD-induced bone loss. These data highlight a potential mechanistic role of osteocytes in inflammatory bone loss associated with IBD and systemic inflammation. © 2017 American Society for Bone and Mineral Research.

Serum osteoprotegrin (OPG) in subclinical atherosclerosis in systemic lupus erythematosus

Introduction Osteoprotegerin (OPG) is a member of the tumor necrosis factor (TNF) receptor family. It has recently been demonstrated that OPG is produced by a variety of tissues, including the cardiovascular system (heart, arteries, veins), lung, kidney, immune tissues, and bone. The OPG-RANKL signaling pathway is strongly related to vascular calcification. We determined the association of this biomarker with subclinical atherosclerosis in systemic lupus erythematous (SLE). Methods We measured OPG and markers of subclinical atherosclerosis (coronary artery calcium (CAC), carotid intima-media thickness (cIMT) carotid plaque) in 166 SLE patients (91% female, 64% Caucasian, 31% African American, 5% others, mean age 45 years). Subgroups of patients with different levels of OPG level were compared with respect to average levels of CAC, cIMT, and with respect to presence of carotid plaque. Age was adjusted for using multiple regression. Results OPG was highly correlated with age ( p < 0.0001). Individuals with higher levels of OPG tended to have higher measures of CAC, cIMT, and more carotid plaque. However, after adjustment for age, these associations, while still positive, were no longer statistically significant. Conclusion In our study much of the association observed was due to confounding by age, and after adjusting for age, our findings do not rule out the possibility of a null association.

A 1-year prospective study of the effect of infliximab on bone metabolism in inflammatory bowel disease patients

OBJECTIVES

Infliximab (IFX) treatment has shown potentially beneficial effects on bone metabolism in inflammatory bowel disease (IBD) patients. We aimed to prospectively evaluate the impact of IFX treatment on bone metabolism in antitumour necrosis factor (TNF)-α-naive IBD patients using established bone metabolism markers and an in-vitro osteoblast model.

MATERIALS AND METHODS

A total of 37 anti-TNFα-naive IBD patients and 20 healthy controls were included. All measurements were performed at baseline and repeated in IBD patients following IFX therapy. Bone mineral density was measured by dual-energy X-ray absorptiometry. Parathyroid hormone, vitamin D, osteoprotegerin, soluble receptor activator of nuclear factor B ligand and proinflammatory and anti-inflammatory cytokines were measured. Bone formation was measured using osteocalcin (OC) and procollagen type 1N propeptide, and bone resorption was measured using serum type 1 collage c-telopeptide. The effect of control and IBD patient sera on human osteoblast viability and differentiation was analysed.

RESULTS

OC level was higher in controls than IBD patients (P=0.018). After IFX, OC and procollagen type 1N propeptide increased significantly (P=0.002 and 0.011) and (P<0.001 and P=0.016) at weeks 6 and 30 after treatment, respectively. There was a nonsignificant decrease in serum type 1 collage c-telopeptide. After IFX therapy, proinflammatory cytokines TNF-α, interleukin-6 and interleukin-13 decreased significantly (P=0.016, week 54; P=0.005, week 6 and P=0.025, week 6), respectively. Sera from IBD patients before IFX showed increased osteoblast viability compared with the controls (P=0.003 to P<0.005), but induced reduced osteoblast differentiation. After IFX, viability reduced to control levels, but osteoblast differentiation increased (P=0.041).

CONCLUSION

IFX treatment induced beneficial effects on bone metabolism. Osteoblast culture results suggest that IBD patients may have increased osteoblast viability, but reduced differentiation, which has implications for bone strength.

Osteoprotegerin: A novel biomarker for inflammatory bowel disease and gastrointestinal carcinoma

Osteoprotegerin (OPG) is a member of the tumor necrosis factor receptor superfamily of proteins. Although initial data illustrated the key role that OPG plays in bone turnover, numerous recent reports indicate that OPG is also an important factor in inflammatory pathways and tumor cell survival. OPG contributes directly to inflammatory processes and has been evaluated as a novel non-invasive biomarker of gut inflammation. Furthermore, OPG affects cell turn-over, differentiation, death, and survival via extracellular pathways, correlating with worse prognosis in inflammatory bowel diseases and several gastrointestinal carcinomas. It is now clear that OPG has multiple functions and characteristics. This review gives an overview of OPG, highlights its roles in different extracellular pathways, and outlines how OPG could be used as a novel non-invasive biological marker in inflammatory bowel diseases and gastrointestinal carcinomas.

Adalimumab Therapy Has a Beneficial Effect on Bone Metabolism in Patients with Crohn's Disease

BACKGROUND

Infliximab has been shown to have beneficial effects on bone metabolism in patients with Crohn's disease (CD) although as yet the exact mechanisms have not been fully elucidated.

AIM

To evaluate the impact of adalimumab therapy on bone metabolism using a combined in vivo and in vitro model.

METHODS

Parathyroid hormone, vitamin D, bone formation markers, bone resorption marker, pro-inflammatory cytokines, anti-inflammatory cytokines, osteoprotegerin, and sRANKL were measured in control patients and pre- and post-treatment with adalimumab in CD patients. The effect of control patients' and pre- and post-treatment CD patients' sera on human osteoblasts (hFOB 1.19) in vitro cell viability and differentiation was also analyzed.

RESULTS

There was a significant increase in bone formation markers osteocalcin (P < 0.05) and procollagen type 1 N-terminal propeptide (P < 0.01) at 1 and 3 months post-treatment. Moreover, there was a sustained but not significant fall in serum CTx, a bone resorption marker. No significant change was seen over time with other parameters measured. Serum from CD patients pre-treated with adalimumab showed increased osteoblast viability compared with that of post-treated patients at 6 months (P = 0.002) and controls. However, post-adalimumab treatment sera at 6 months appeared to increase osteoblast differentiation (P = 0.001), which is likely to be important in new bone formation.

CONCLUSIONS

This first study evaluating the role of adalimumab as a possible bone protector in Crohn's disease patients has shown that similar to infliximab, adalimumab has complex and potentially beneficial effects on bone metabolism.

Osteoprotegerin, s-RANKL, and selected interleukins in the pathology of bone metabolism in patients with Crohn's disease

Introduction

Crohn's disease (CD) promotes the development of osteopaenia/osteoporosis, the cytokine background of which is not fully known.

Aim

Evaluation of bone mineral density (BMD), the prevalence of osteopaenia and osteoporosis, and the determination of the levels of selected interleukins (IL), osteoprotegerin (OPG), and s-RANKL proteins in patients with CD in relation to a control group and assessment of the relationship between the tested cytokines, OPG, s-RANKL, and BMD.

Material and methods

Thirty-seven CD patients and 37 healthy volunteers (control group) were enrolled into the study. Densitometry of the lumbar spine (L2–L4) and of the femoral neck using the DXA technique was carried out. Serum levels of: IL-13, IL-4, IL-17, IL-1β, OPG, and s-RANKL were determined using the ELISA method. Progression-of-disease questionnaires were collected.

Results

The prevalence of osteoporosis and osteopaenia in the CD group was: 18.92% and 32.43% in L2–L4; 13.51% and 35.13% in the neck, respectively. The IL-13 and IL-1β concentrations were significantly higher and OPG was significantly lower in CD patients when compared to controls. In the case of all subjects: IL-13 correlated negatively with the BMD of the neck, IL-17 correlated negatively with the Z-score of L2–L4, and OPG correlated negatively with the IL-13. In the case of CD patients, IL-4 correlated negatively with the BMD of L2–L4.

Conclusions

The incidence of osteopaenia and osteoporosis in Polish CD patients is high. IL-13, IL-1β, and IL-4 seem to be connected with the pathology of decreased BMD in CD. It can be hypothesised that IL-13 may lower BMD by modulating OPG.

Paediatric inflammatory bowel disease: a mechanistic approach to investigate exclusive enteral nutrition treatment

The inflammatory bowel diseases (IBD) include Crohn's disease (CD) and ulcerative colitis. The disease may present at any age although the peak of presentation is the second and third decades of life. The incidences of these diseases are increasing around the world with the age of presentation getting younger. At present CD is incurable with colectomy being the treatment for severe UC. Although several pharmacological approaches are used to modulate the inflammatory response in IBD, few lead to histological healing and most have side effects. An alternative approach is to use enteral formulae given exclusively (EEN) to treat IBD. EEN requires the consumption of an elemental or polymeric formula, with the exclusion of all other nutrients, for a period of up to 12 weeks. The introduction of EEN as a therapeutic option for IBD was through prudent observation; however, EEN has become an established and reliable option for the treatment of paediatric IBD. Despite this, the mechanisms through which EEN induces disease remission are unknown and remain hypothetical. This review will discuss recent research into EEN both describing clinical features of EEN therapy and discussing the most up-to-date understanding of the mechanisms through which EEN may be reducing intestinal inflammation and inducing disease remission.

Inflammatory bowel disease and the risk of osteoporosis and fracture

Inflammatory bowel disease (IBD) is commonly believed to increase the risk of bone mineral loss, leading to osteoporosis and an increased risk of disabling fractures. In this narrative review, we will presenting a summary of the published medical literature in regards to the relationship between IBD and the development of osteoporosis, bone mineral loss, and fractures. We will explore the epidemiology of metabolic bone disease in IBD, focusing on the prevalence and both the general and IBD-specific risk factors for the development of osteoporosis and of fracture in persons with IBD. We will also examine the role of the inflammatory process in IBD promoting excessive bone mineral loss, as well as the role that low body mass, corticosteroid use, diet, and nutrient malabsorption play in contributing to bone disease. Last, we will discuss our recommendation for: screening for osteoporosis in IBD patients, the use of preventative strategies, and therapeutic interventions for treating osteoporosis in persons with IBD.

Osteoprotegerin in pediatric Crohn's disease and the effects of exclusive enteral nutrition

BACKGROUND

Osteoprotegerin (OPG) may have proinflammatory roles in addition to its contribution to the maintenance of bone mass. Exclusive enteral nutrition (EEN) is an established therapy for the induction of remission in Crohn's disease (CD). The aims of this study were to ascertain serum, fecal, and mucosal expression of OPG in children with CD and to investigate the effects of EEN on OPG expression.

METHODS

OPG was measured by enzyme-linked immunosorbent assay in serum, mucosal, and fecal samples collected from children with CD and controls. Fecal and Serum OPG was measured prior to and following 6-8 weeks of EEN therapy.

RESULTS

Children with CD (n=82) and controls (n=45) were included. Mucosal and fecal OPG levels were elevated in CD compared to controls (P=0.018 and P<0.0001, respectively). Serum OPG was elevated in children with severe CD (P=0.005). Serum and fecal OPG levels dropped significantly following EEN therapy (P=0.0001 and P=0.002, respectively).

CONCLUSIONS

Increased serum and fecal OPG are seen in active CD and likely originate from the inflamed gut. Fecal and serum OPG decrease following EEN therapy. Further investigation of OPG and related proteins in the setting of IBD is now required.

Advances in the understanding of mineral and bone metabolism in inflammatory bowel diseases

Chronic inflammatory disorders such as inflammatory bowel diseases (IBDs) affect bone metabolism and are frequently associated with the presence of osteopenia, osteoporosis, and increased risk of fractures. Although several mechanisms may contribute to skeletal abnormalities in IBD patients, inflammation and inflammatory mediators such as TNF, IL-1β, and IL-6 may be the most critical. It is not clear whether the changes in bone metabolism leading to decreased mineral density are the result of decreased bone formation, increased bone resorption, or both, with varying results reported in experimental models of IBD and in pediatric and adult IBD patients. New data, including our own, challenge the conventional views, and contributes to the unraveling of an increasingly complex network of interactions leading to the inflammation-associated bone loss. Since nutritional interventions (dietary calcium and vitamin D supplementation) are of limited efficacy in IBD patients, understanding the pathophysiology of osteopenia and osteoporosis in Crohn's disease and ulcerative colitis is critical for the correct choice of available treatments or the development of new targeted therapies. In this review, we discuss current concepts explaining the effects of inflammation, inflammatory mediators and their signaling effectors on calcium and phosphate homeostasis, osteoblast and osteoclast function, and the potential limitations of vitamin D used as an immunomodulator and anabolic hormone in IBD.

Serum correlates of the placebo effect in irritable bowel syndrome

BACKGROUND In diseases defined primarily by the subjective nature of patient self-report, placebo effects can overwhelm the capacity of randomized controlled trials to detect medication-placebo differences. Moreover, it is unclear whether such placebo effects represent genuine psychobiological phenomena or just shifts in selective attention. Knowledge of predictors of the placebo response could improve the design of clinical trials and the delivery of personalized medical care. METHODS In patients with irritable bowel syndrome (IBS), a subset of our previous study that were randomized to placebo treatment (sham acupuncture) or no-treatment group (waitlist), we tested an enriched panel of 10 serum biomarkers at the enrolment and the 3rd week of intervention, using a multiplex electrochemiluminescent immunoassay. KEY RESULTS More pronounced changes overtime in serum levels of osteoprotegerin (OPG) have been found in patients who received placebo treatment compared with the waitlist group (P = 0.039). Moreover, serum levels of OPG at baseline were found to be higher (P = 0.0167) in patients who subsequently achieved adequate relief (AR) of their IBS symptoms, independently of their treatment group. Besides, serum levels of TNF-related weak inducer of apoptosis (TWEAK) at baseline were also higher (P = 0.0144) in patients who reported AR and in particular in those who received the placebo treatment. CONCLUSIONS & INFERENCES These two measurable biological parameters associated with placebo, namely serum OPG and TWEAK, provide a proof of principle for discovering putative molecular signatures of placebo response in IBS and perhaps in other illnesses with patient self-reported outcomes.

RANKL inhibition for the management of patients with benign metabolic bone disorders

The receptor activator of NF-kappaB ligand (RANKL) is a member of the TNF receptor superfamily, essential for osteoclastogenesis. It binds to its receptor activator of NF-kappaB on the surface of osteoclast precursors and enhances their differentiation, survival and fusion, while it activates mature osteoclasts and inhibits their apoptosis. The effects of RANKL are counteracted by osteoprotegerin (OPG), a neutralizing decoy receptor. Derangement of the balance in RANKL/OPG action is implicated in the pathophysiology of metabolic bone diseases, including osteoporosis. Current therapies used to prevent or treat metabolic bone diseases are thought to act, at least in part, through modification of the RANKL/OPG dipole. The idea of using a molecule that could specifically bind and neutralize RANKL to decrease bone resorption and subsequent bone loss is appealing. Recombinant OPG was initially tested. Denosumab, a fully human monoclonal antibody against RANKL, is a promising antiresorptive agent under investigation. It rapidly decreases bone turnover markers resulting in a significant increase in bone mineral density and reduction in fracture risk. However, because receptor activator of NF-kappaB activation by RANKL is also essential for T-cell growth and dendritic-cell function, inhibition of its action could simultaneously affect the immune system, leading to susceptibility in infections or malignancies.

Comparison of the effects of 1,25 dihydroxyvitamin D and 25 hydroxyvitamin D on bone pathology and disease activity in Crohn's disease patients

BACKGROUND

Vitamin D is essential for osteopenia therapy in Crohn's disease (CD). The active form of vitamin-D (aVD) is the 1,25(OH)2D. There are no data available whether aVD or plain vitamin-D (pVD) has any advantage in managing osteoporosis in CD or has any effect on the activity of the disease itself. Our work is a prospective study to compare the effects of aVD and pVD on bone metabolism and the clinical course of CD.

METHODS

In all, 37 inactive CD patients were involved in the study and divided into 2 age-, gender-, and t-score-matched groups. Group A was treated with aVD while group B received pVD. Osteocalcin, beta-CrossLaps, osteoprotegerin, and receptor activator nuclear factor kappa-B ligand concentrations were estimated at the start of the study and at 6 weeks and 3 and 12 months. The activity of CD was also measured clinically and by laboratory parameters.

RESULTS

At week 6 the Crohn's Disease Activity Index (CDAI) scores and concentration of C-reactive protein decreased (69.44 +/- 58.6 versus 57.0 +/- 54.89 and 15.8 +/- 23.57 mmol/L versus 7.81 +/- 3.91 mmol/L, respectively, P < 0.05) parallel with markers of bone turnover (beta-CrossLaps: 0.46 +/- 0.21 ng/mL versus 0.40 +/- 0.25 ng/mL, and osteocalcin: 32.29 +/- 15.3 ng/mL versus 29.98 +/- 14.14 ng/mL, P < 0.05); however, osteoprotegerin concentration (marker of osteoblast activity) increased (3.96 +/- 2.1 pg/mL versus 4.58 +/- 2.19 pg/mL) in group A, but did not change in group B. Osteocalcin and beta-CrossLaps concentrations changed more significantly by the 3rd month; however, these changes disappeared by the 12th month.

CONCLUSIONS

According to our study, aVD has a more prominent short-term beneficial effect on bone metabolism and disease activity in CD compared with pVD.

Induction and cellular expression of tartrate resistant acid phosphatase during dextran sodium sulphate induced colitis in rats

The aim of this study was to investigate the cellular and molecular expression of tartrate resistant acid phosphatase (TRAP) as a marker of activated macrophages in macrophage dependent dextran sulphate sodium (DSS)-induced colitis in rats. In normal colon, TRAP+/CX(3)CR(1)+ macrophages were located in the upper part of the lamina propria. In the early stage (day 1-3) of acute colitis prior to histopathological changes, induction of the cytokines TNFalpha, IL-12 and IFN gamma occurred concomitant with increased mRNA and enzyme activity of TRAP along with a slight increase of TRAP immunolabelling in macrophages of the upper lamina propria, suggesting induction of TRAP in resident macrophages. Among these cytokines, TNFalpha up-regulated TRAP expression in the RAW 264.7 monocyte/macrophage cell line. In a later phase (day 7) with fulminant colitis, a massive infiltration of macrophages including recruited TRAP+/CCR2+ cells was observed also in the lower part of the lamina propria as well as in the submuscular layer. Additionally, differentiated cellular expression of pro- and mature TRAP also suggest that mucosal macrophages in the lower part of lamina propria bordering the sub-mucosa provide a source of replenishment of macrophages situated in the upper lamina propria. In conclusion, induction of TRAP provides an early sign of macrophage responsiveness in DSS induced colitis.

Osteoporosis in inflammatory bowel disease

Osteoporosis commonly afflicts patients with inflammatory bowel disease, and many factors link the 2 states together. A literature review was conducted about the pathophysiology of osteoporosis in relation to inflammatory bowel disease. Screening guidelines for osteoporosis in general as well as those directed at patients with inflammatory bowel disease are reviewed, as are currently available treatment options. The purpose of this article is to increase physician awareness about osteopenia and osteoporosis occurring in patients with inflammatory bowel disease and to provide basic, clinically relevant information about the pathophysiology and guidelines to help them treat these patients in a cost-effective manner.

A single-nucleotide polymorphism in the gene encoding osteoprotegerin, an anti-inflammatory protein produced in response to infection with diarrheagenic Escherichia coli, is associated with an increased risk of nonsecretory bacterial diarrhea in North American travelers to Mexico

BACKGROUND

Osteoprotegerin (OPG), an immunoregulatory member of the TNF receptor superfamily, is expressed in inflamed intestinal mucosa. We investigated whether OPG is produced by intestinal epithelial cells and tested the hypothesis that single-nucleotide polymorphisms (SNPs) in the gene encoding OPG (TNFRSF11B) are associated with traveler's diarrhea (TD) among North American travelers to Mexico.

METHODS

OPG concentration was measured in the supernatants of T84 cells infected with various diarrheagenic Escherichia coli pathotypes. Genotyping was performed for 4 SNPs in the OPG gene for 968 North American travelers with or without TD. Stool samples from travelers with TD were evaluated for the presence of enteric pathogens.

RESULTS

T84 cells produced higher OPG levels in response to infection with various diarrheagenic E. coli pathotypes than with E. coli controls (P<.05). A SNP in the exon 1 region of the OPG gene (OPG+1181G>C) was associated with TD in white travelers who stayed in Mexico for >1 week during the summer (P=.009) and for TD due to nonsecretory pathogens (P=.001).

CONCLUSIONS

Our study suggests that OPG is secreted by intestinal epithelial cells in response to enteropathogens and that a polymorphism in the OPG gene is associated with an increased susceptibility to TD.

Proinflammatory cytokines and receptor activator of nuclear factor kappaB-ligand/osteoprotegerin associated with bone deterioration in patients with Crohn's disease

OBJECTIVES

The high incidence of bone disease and the increasing evidence of Crohn's disease (CD) bone decline in corticosteroid users and nonusers suggest that bone metabolism is affected by inflammatory process. The aim of the study was to compare serum levels of proinflammatory cytokines, markers of bone turnover and regulatory molecules of osteoclast biogenesis, receptor activator of nuclear factor kappaB-ligand (RANKL) and osteoprotegerin (OPG), between naïve and long-standing CD patients.

METHODS

The study included 95 CD patients, 15 of them with newly diagnosed and previously untreated CD. The spine and hip bone mineral density was measured by dual-energy X-ray absorptiometry. Biochemical markers were determined by immunoassay.

RESULTS

Osteopenia was recorded at diagnosis in 53% of naïve patients and osteoporosis was found in 26% of long-standing CD patients. The newly diagnosed patients showed correlation between TNF-alpha and soluble RANKL (sRANKL) (r=0.5; P=0.04), and this positive relationship characterized the study population as a whole (r=0.3; P=0.003). Analysis of the OPG and sRANKL relationship showed absence of correlation in patients with healthy skeleton, whereas an inverse correlation was found in those with osteopenia (r=-0.31; P=0.033) and osteoporosis (r=-0.48; P=0.028). In naïve patients with reduced T score, the correlation between sRANKL and OPG was highly inverse (r=-0.8; P=0.02) and these patients were characterized by lower BMI, significantly higher level of proinflammatory cytokines, elevated C-reactive protein, and increased activity of free sRANKL and OPG.

CONCLUSION

Bone disease that accompanies CD at diagnosis suggests that bone metabolism is affected by the underlying inflammatory process per se, as probably confirmed by our finding of the central proinflammatory cytokine TNF-alpha being strongly associated with the osteoclastogenic mediator RANKL, and inversely with bone density.

Circulating osteoprotegerin levels are elevated and correlated with antiphospholipid antibodies in patients with systemic lupus erythematosus

Patients with antiphospholipid syndrome (APS) have an increased risk for the development of thrombotic complications. Recent studies indicate that osteoprotegerin (OPG) acts as an important molecule in the development of vascular diseases. The aim of the present study was to examine the association between serum OPG levels and APS manifestations in patients with SLE. Seventy-nine patients with SLE and ninety-two healthy controls, matched for age and sex, were included in this study. Serum levels of OPG, monocyte chemoattractant protein(MCP)-1 and soluble E-selectin were determined by ELISA. At the time of serum sampling, various clinical and laboratory parameters were assessed. We found that serum levels of OPG were significantly higher in patients with SLE than in healthy controls (1236 ± 82 vs 967 ± 37 pg/mL, P = 0.003). Particularly, serum OPG levels were significantly higher in SLE patients with APS than those without (1615 ± 191 vs 1171 ± 91 pg/mL, P = 0.006). Serum OPG levels correlated with titres of IgG anti-cardiolipin antibody ( P = 0.026) and anti-β2-glycoprotein I antibody ( P < 0.001). Moreover, serum OPG also correlated with serum levels of sE-selectin ( P = 0.002), which is an endothelial cell activation marker, and MCP-1 ( P = 0.003), a well known chemokine implicated in thrombogenesis. Collectively, serum OPG levels were increased in SLE patients with APS and correlated with titres of antiphospholipid antibodies, suggesting that OPG might be linked to the development of APS.

Dextran sodium sulfate-induced colitis causes rapid bone loss in mice

INTRODUCTION

Osteopenia is a common complication of human inflammatory bowel disease (IBD). We evaluated the contribution of colonic inflammation to osteopenia and its mechanism in a murine colitis model.

METHODS

Colitis was induced by adding dextran sodium sulfate (DSS) to the drinking water for 2 weeks to nine-week-old Balb/C male mice. 5% DSS was added on the first week and was reduced to 2.5% on the second week. Age- and sex-matched Balb/C mice served as the control group. Indices of femoral bone mass and architecture were determined by micro computed tomography (muCT). Bone formation parameters and osteoclast number were determined by dynamic histomorphometry. The degree of colonic inflammation was assessed by a clinical disease activity index, and colonic mucosal myeloperoxidase activity.

RESULTS

DSS-treated mice exhibited a significantly lower bone mass compared to controls as indicated by decreased trabecular bone volume (BV/TV) of 32%. This reduction was accompanied by decreased trabecular number (23%) and connectivity density (37%) compared to the controls. No changes were observed in cortical bone indices. Osteopenia resulted from suppressed bone formation, as indicated by decreased trabecular double-labeled surface (dL%) of 90%, mineralizing surface (MS) of 62%, and bone formation rate (BFR) of 67%, and increased bone resorption as indicated by a 34% increase in osteoclast number in DSS-treated mice compared to the controls. Myeloperoxidase activity inversely correlated with trabecular BV/TV (r=-0.67, p=0.02), trabecular number (r=-0.86, p=0.0008) and connectivity density (r=-0.63, p=0.03). Myeloperoxidase activity inversely correlated with the bone formation indices: dL%, MS, and BFR (r=-0.79, p=0.007, r=-0.84, p=0.002, r=-0.83, p=0.003, respectively).

CONCLUSIONS

DSS-induced colitis is associated with reduced femoral bone mass and altered micro architecture, which results from suppressed bone formation and increased bone resorption. The decrease in indices of bone mass, structure and formation are directly linked to the degree of colonic mucosal inflammation. DSS-induced colitis can be used to study pharmacological interventions for bone loss in colitis.

Parathyroid hormone is predictive of low bone mass in Canadian aboriginal and white women

Canadian Aboriginal women have lower age- and weight-corrected bone mineral density (BMD) and lower vitamin D status than White women. This study was undertaken to describe the differences in biomarkers of bone metabolism and vitamin D in Aboriginal and non-Aboriginal women and to establish which biomarkers were predictive of BMD. In total, 41 rural Aboriginal, 212 urban Aboriginal and 182 urban White women were studied for BMD of the distal radius, calcaneus, lumbar spine, femoral neck, total hip and whole body using dual-energy X-ray absorptiometry. Serum biomarkers measured included calcium, phosphate, alkaline phosphatase (ALP), C-telopeptide of type 1 collagen (CTX), osteocalcin (OC), osteoprotegerin (OPG), parathyroid hormone (PTH) and 25(OH)D. Data were analyzed for differences among the three groups stratified by age (25 to 39, 40 to 59 and 60 to 75 y) using factorial ANOVA. Predictors of BMD including ethnicity, age and body weight were identified using step-wise regression. Unadjusted BMD of all sites declined with age regardless of ethnic grouping. Prediction models for 5 of 6 BMD sites included PTH accounting for age and body weight. Other predictors of BMD included OC for the radius and calcaneus; OPG for spine and total hip; and ALP for whole body and calcaneus. Serum 25(OH)D was not included in any model of BMD. After accounting for all variables in the regression equation, an average Aboriginal woman of 46 y and 79 kg was predicted to have 6% lower calcaneus BMD and 3% lower radius BMD compared to a White woman of the same age and weight. In conclusion, PTH is a better predictor of BMD than 25(OH)D in this population of Aboriginal and White women.

Changes of OPG and RANKL concentrations in Crohn's disease after infliximab therapy

BACKGROUND

Osteoporosis is a well-known complication of Crohn's disease (CD). Osteoprotegerin (OPG) concentration is elevated in patients with CD compared to healthy controls. Long-term infliximab (IFX) maintenance therapy improves the patients' bone mineral density. The effect of IFX on bone metabolism has not yet been clarified. Our aim was to evaluate IFX effects on bone pathology in CD patients.

METHODS

Twenty-nine patients were treated with IFX as an induction therapy according to international guidelines at weeks 0, 2, and 6. Serum concentrations of biochemical markers of bone formation (osteocalcin, OC) and bone resorption (beta-crosslaps, bCL), and serum concentrations of OPG and receptor activator of nuclear factor kappa B ligand (sRANKL) were measured before every treatment at days 1, 14, and 42.

RESULTS

Serum levels of OC and sRANKL increased after treatment. OC concentrations were 28.93 +/- 14.95 ng/mL versus 36.33 +/- 20.05 ng/mL (P < 0.005) at days 1 and 42, respectively; sRANKL concentrations were elevated from 0.0112 +/- 0.028 ng/mL to 0.0411 +/- 0.123 ng/mL (NS) by the end of the study. The concentrations of both bCL and OPG decreased. bCL concentrations were 0.636 +/- 0.594 versus 0.519 +/- 0.235 (NS) at days 1 and 42, respectively, while OPG concentration decreased from 3.739 +/- 1.485 to 3.491 +/- 1.618 (P < 0,05).

CONCLUSIONS

IFX therapy decreased the OPG concentration in CD patients significantly. In parallel, the serum bone resorption marker (bCL) also decreased. Concentrations of bone formation marker (OC) and sRANKL increased during the same period; however, those changes were not statistically significant. Elevated OPG in CD could be a counter-regulatory response to inflammatory cytokines or may reflect T-cell activation.

Review article: appropriate use of corticosteroids in Crohn's disease

BACKGROUND

Corticosteroids are a well-established treatment for active Crohn's disease and have been widely used for decades. It has become apparent, however, that a proportion of patients either fails to respond to corticosteroids or is unable to withdraw from them without relapsing. Furthermore, their use is associated with a range of side effects, such that long-term treatment carries unacceptable risk.

AIM

To review the evidence regarding the appropriate use of corticosteroids in Crohn's disease, along with their side effects, safety and alternatives.

METHODS

To collect relevant articles, a PubMed search was performed from 1966 to November 2006 using the terms 'steroid', 'corticosteroid', 'glucocorticoid', 'prednisolone', 'prednisone', 'methylprednisolone', 'hydrocortisone', 'dexamethasone' and 'budesonide' in combination with 'Crohn(s) disease'. Relevant articles were reviewed, as were their reference lists to identify further articles.

RESULTS

When used correctly, corticosteroids are a highly effective, well tolerated, cheap and generally safe treatment for active Crohn' disease. Nevertheless, approximately 50% of recipients will either fail to respond (steroid-resistant) or will be steroid dependent at 1 year. Newer alternatives to corticosteroids are not, however, without risk themselves and, moreover, are not necessarily available universally.

CONCLUSIONS

Steroids are used widely to treat Crohn's disease, a situation that is unlikely to change in the near future. Accordingly, efforts should be made to ensure that they are used correctly and that their side effects are minimized. Reference is made to recently published guidelines and a simplified 'users guide' is presented.

Plasma Osteoprotegerin Levels in the General Population

Osteoprotegerin, a member of the tumor necrosis factor receptor superfamily, has pleiotropic effects on bone metabolism, endocrine function, and the immune system. Myocardial expression and circulating levels of osteoprotegerin are increased in heart failure. The relationship between osteoprotegerin levels in the general population and indices of left ventricular structure and function is unknown. Plasma osteoprotegerin levels and cardiac MRI indices of left ventricular structure and function were available in 2715 subjects (median age: 44 years; 45% male) enrolled in the Dallas Heart Study. The associations between osteoprotegerin concentration and indices of left ventricular structure and function were assessed by linear regression analysis, adjusting for possible confounders. By gender-specific linear regression analysis, higher osteoprotegerin levels were significantly associated with higher left ventricular mass, left ventricular wall thickness, left ventricular concentricity index, and lower left ventricular ejection fraction (P<0.001 for all). After adjustment for age, race, fat-free mass, fat mass, hypertension, diabetes, coronary artery disease, estimated glomerular filtration rate, hypercholesterolemia, smoking status, hormone replacement therapy, coronary artery calcium score >10, and presence of aortic plaque, osteoprotegerin remained significantly associated with each of these left ventricular indices among male subjects (P<0.05 for each). Among female subjects, higher osteoprotegerin was independently associated with higher left ventricular end-systolic volume and lower ejection fraction (P<0.0001 for each) but not with indices of left ventricular hypertrophy. These findings are compatible with the theory that osteoprotegerin may play a pathophysiological role in the development of left ventricular hypertrophy and systolic dysfunction.

Vertebral fractures and role of low bone mineral density in Crohn's disease

BACKGROUND & AIMS

Vertebral fractures in Crohn's (CD) patients with low bone mineral density (BMD) have been documented as between 14%-22%. Vertebral fractures in CD patients with normal BMD have not been reported. The objectives were to identify the prevalence of vertebral fractures in CD patients and associated predictive factors.

METHODS

Two hundred twenty-four CD patients underwent vertebral BMD analysis and radiographs. Fractures were identified by using quantitative height reduction morphometry, and severity was assessed by spinal fracture index.

RESULTS

Mean age was 40.6 +/- 11.0 years. Sixty percent reported corticosteroid use during the preceding year. Forty-five of 224 (20.0%) patients had 88 vertebral fractures. Sixteen of 45 patients with vertebral fractures had normal BMD (19.0% of all patients with normal BMD). Analysis of patients with or without vertebral fractures did not demonstrate significant differences in BMD or in corticosteroid use. Linear regression analysis demonstrated that elevations in body mass index, C-reactive protein, and parathyroid hormone were significantly predictive of vertebral fractures (r = 0.415, P < .05), and height reduction was >20% (r = 0.417, P < .05).

CONCLUSIONS

This study demonstrates that vertebral fractures in CD patients occur with an equal frequency in those with low and with normal BMD, regardless of corticosteroid use. The mean age of CD patients with vertebral fractures was much lower than that reported in the general population for these fractures. Elevations in body mass index and C-reactive protein and parathyroid hormone levels were predictive of vertebral fractures.

Soluble receptor activator of NFkappa B-ligand and osteoprotegerin in rheumatoid arthritis - relationship with bone mineral density, disease activity and bone turnover

The aim of our study was to investigate determinants of bone mineral density (BMD) measured by dual X-ray absorptiometry at the lumbar spine (BMD-LS) and at the femoral neck (BMD-FN) in patients with rheumatoid arthritis (RA) with special respect to bone resorbing proinflammatory cytokines and their physiological antagonists. In 142 RA patients the following parameters were measured in parallel with BMD: serum levels of soluble receptor activator of nuclear factor kappa-B-ligand (sRANKL), osteoprotegerin (OPG), interleukin (IL)-6, soluble glycoprotein 130 (sgp130), 25-hydroxyvitamin D3 (25OHD(3)), 1,25-dihydroxyvitamin D3 (1,25[OH](2)D(3)), intact parathyroid hormone, osteocalcin, ionized calcium, renal excretion of pyridinolin and deoxypyridinolin, C-reactive protein, and erythrocyte sedimentation rate (ESR). No significant differences of sRANKL, OPG, IL-6, and spg130 were found between patients with osteoporosis (47.9% of patients), osteopenia (36.6%), and normal BMD (15.5%). However, total sRANKL was significantly higher in postmenopausal women with osteoporosis at FN than in those without (p < 0.05) and showed a negative correlation with BMD-LS in patients older than 60 years (p = 0.01). BMD-LS and BMD-FN (p < 0.001) and total sRANKL (p < 0.01) were negatively related with the age of the patients. Only IL-6 (positive correlation, p < 0.001) and 1,25(OH)(2)D(3) (negative correlation, p < 0.001) but not sRANKL, OPG, and sgp130 were related to disease activity. Using multiple linear regression analysis, menopause was identified as the crucial negative determinant of BMD-LS (R (2) = 0.94, p = 0.001), whereas cumulative glucocorticoid dose (beta = -0.80, p = 0.001) and ESR (beta = -0.44, p = 0.016) were the negative determinants of BMD-FN (R (2) = 0.86, p = 0.001). The results indicate that influences of age and gender must be considered in investigations on the relationship between BMD and sRANKL in RA and that high serum levels of sRANKL seems to be associated with osteoporosis only in subgroups of RA patients.

Imbalance of the Osteoprotegerin/RANKL Ratio in Bone Marrow Microenvironment After Allogeneic Hemopoietic Stem Cell Transplantation

BACKGROUND

Bone loss is a common complication after allogeneic stem cell transplantation. Osteoprotegerin (OPG) plays a critical role in bone remodeling by neutralizing the effect of receptor activator of nuclear factor-kappaB ligand (RANKL) on differentiation and activation of osteoclasts. We investigated OPG and RANKL in serum and marrow plasma in transplanted patients.

MATERIALS AND METHODS

In 36 patients and 36 controls, the relationships among bone mineral density, circulating OPG, RANKL, interferon-gamma, and interleukin-6 levels were investigated; in addition, OPG and RANKL were measured in marrow plasma and in conditioned medium of long-term cultures of marrow mesenchymal-derived osteogenic cells.

RESULTS

Lumbar and femoral bone mineral density were lower in patients than in controls (P<0.01). Serum OPG (sOPG) and interferon-gamma were significantly higher in patients than in controls (P<0.05). Patients' interferon-gamma correlated with sOPG levels (r=0.4; P=0.03). Interleukin-6 did not differ between patients and controls. By contrast, OPG levels were lower in patients than in controls in marrow plasma (P<0.001) and in conditioned media after one (P=0.035) and three months (P=0.003) of culture of marrow mesenchymal-derived osteogenic cells. RANKL was similar in patients and controls. The OPG/RANKL ratio "in situ" was significantly lower in patients than in controls (P<0.05). There was no correlation between sOPG and marrow OPG, RANKL levels, densitometric values, and chronic graft-versus-host disease.

CONCLUSION

Our findings suggest that after allogeneic stem cell transplantation: 1) sOPG bear no relationship with OPG in the bone marrow; 2) increased sOPG can be the result of its enhanced production in extra bone tissues triggered by inflammatory cytokines; 3) low bone marrow OPG levels may be partly related to the persistent quantitative and qualitative deficit of osteoblastic precursors; and 4) reduced OPG/RANKL ratio in bone microenvironment may increase bone remodeling by promoting bone resorption.

Inflammatory bowel diseases as secondary causes of osteoporosis

Inflammatory bowel disease (IBD), comprising Crohn's disease and ulcerative colitis, is associated with an increased risk of osteoporosis and bone fractures. Initial studies suggested very high rates of osteoporosis in IBD, but more recent studies have suggested that bone mineral density (BMD) is often normal in patients with IBD and typically changes little over time. Nonetheless, IBD is associated with an increased risk of fractures. Doctors managing patients with IBD must consider a variety of risk factors, not just BMD measurements, in assessing fracture risk. Advances have been made in exploring the pathogenesis of osteoporosis in IBD. The evolution of knowledge regarding receptor for activated factor of nuclear factor kappaB (RANK), its ligand RANKL, and osteoprotegerin (OPG), which serves as a decoy receptor, has enhanced the understanding of both osteoporosis and T-cell immunobiology. Recent clinical studies in patients with IBD have revealed that serum OPG levels may be elevated and inflamed intestinal tissue secretes increased amounts of OPG. It is suspected that OPG levels are elevated as a counterregulatory response to low BMD, as serum OPG levels in IBD have been found to be inversely associated with BMD. Finally, in animal models of IBD, exogenous OPG has reversed both the osteopenia and the enterocolitis, suggesting that it may have a therapeutic role in human IBD.

Prevention and treatment of osteoporosis in inflammatory bowel disease

The following are guidelines for evaluation and consideration for treatment of patients with inflammatory bone disease (IBD) after bone mineral density (BMD) measurements. The Crohn's & Colitis Foundation of America (CCFA) has indicated that its recommendations are intended to serve as reference points for clinical decision-making, not as rigid standards, limits, or rules. They should not be interpreted as quality standards.

Are activated T cells regulators of bone metabolism in children with Crohn disease?

OBJECTIVES

To test the hypothesis that circulating activated T cells may release cytokines that decrease bone turnover in children with Crohn disease.

STUDY DESIGN

Newly diagnosed Crohn disease and healthy controls of similar age were compared for bone age, bone mineral content and density, markers of bone remodeling, and serum concentration and in vitro T-cell production of receptor activator of nuclear factor kappaB ligand (RANKL), interferon (INF)-gamma, and osteoprotegerin (OPG).

RESULTS

Newly diagnosed children with Crohn disease (n=23) had similar bone mineral density (BMD) z-scores and body mass index as the controls (n=40). Biochemical markers of bone remodeling indicated a state of low bone turnover in the Crohn disease patients compared with controls. Serum OPG (pmol/L; mean+/-SD, median) was higher (4.24+/-1.74, 3.98 vs 3.38+/-0.83, 3.41; P<.05), and serum RANKL (pmol/L) was lower in the Crohn disease patients (0.50+/-0.86, 0.28 vs 1.02+/-1.63, 0.49; P<.01), consistent with decreased bone resorption. Activated T cells from Crohn disease patients produced a higher concentration of INF-gamma (ng/microg protein) than those from controls (20.03+/-26.39, 8.70 vs 9.76+/-14.10, 6.17; P<.05).

CONCLUSIONS

The newly diagnosed children with Crohn disease exhibited reduced bone remodeling, possibly due to T-cell INF-gamma and OPG.

Elevated serum levels of the decoy receptor osteoprotegerin in children with Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) is characterized by an accumulation of dendritic Langerhans cells in granulomatous lesions in the bone, skin, and other sites in the body. The pathogenesis of the disease remains unknown. We measured serum levels of the decoy receptor osteoprotegerin (OPG), an important regulator of bone metabolism as well as immune responses, in 18 children with single system (SS) or multi-system (MS) forms of LCH and 20 pediatric controls. OPG levels were significantly increased in LCH patients at diagnosis when compared with controls, and pretreatment levels of OPG were elevated in MS compared with SS patients. Moreover, OPG levels in LCH patients were elevated in patients with involvement of risk organs (liver, lungs, hematopoietic system, or spleen) when compared with patients without risk organ involvement, indicative of an association between OPG values and disease severity. We also observed a positive correlation between serum levels of OPG and tumor necrosis factor (TNF)-alpha, a pro-inflammatory cytokine, at the time of onset of disease. These findings show, for the first time, that serum OPG levels are elevated in LCH patients, and suggest that OPG may play a role in the pathogenesis of this enigmatic disease.

Plasma osteoprotegerin levels are associated with glycaemic status, systolic blood pressure, kidney function and cardiovascular morbidity in type 1 diabetic patients

OBJECTIVE

The bone-related peptide osteoprotegerin (OPG) has recently been found in increased amounts in the vasculature in diabetes. It is produced by vascular smooth muscle and endothelial cells, and may be implicated in the development of vascular calcifications. OPG is present in the circulation, where increased amounts have been observed in patients with diabetes. In this study, we examined whether plasma OPG is associated with the glycaemic and vascular status of patients with type 1 diabetes.

METHODS

Two gender-, age- and duration-comparable groups of type 1 diabetic patients either with (n = 199) or without (n = 192) signs of diabetic nephropathy were studied. Plasma OPG was determined by an ELISA.

RESULTS

The plasma OPG concentration was significantly higher in patients with nephropathy than those without (3.11 (2.49-3.99) vs 2.57 (2.19-3.21) (median (interquartiles), ng/ml), P < 0.001). Plasma OPG correlated with haemoglobin A1c (HbA1c), systolic blood pressure and age in both groups and, in addition, with kidney function in the nephropathic group. These correlations remained significant in multivariate models. In addition, we found that plasma OPG concentrations were increased among patients with cardiovascular diseases (CVD), both in the normoalbuminuric and the nephropathic groups. The differences between nephropathic and normoalbuminuric, as well as subgroups with and without CVD, could largely be ascribed to changes in HbA1c, age, systolic blood pressure and creatinine.

CONCLUSION

OPG is associated with glycaemic control and CVD in patients with type 1 diabetes, compatible with the hypothesis that OPG is associated with the development of diabetic vascular complications.

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.

IBD and skeletal health: children are not small adults!

Patients with inflammatory bowel disease often have decreased bone mass, and fragility fractures can occur. Multiple disease- and treatment related factors, including malnutrition, inflammation, malabsorption, decreased weight-bearing physical activity, and corticosteroids negatively influence bone metabolic activity. Because low-impact fracture is the pathologic expression of critically reduced bone mass and bone quality, knowing the relative risk of fractures in patients with IBD is of great interest. The absolute risk for incident fractures in these patients is still being debated. Clinical and laboratory research is clarifying mechanisms by which IBD can affect the function of osteoblasts and osteoclasts. In this concise review, we aim to provide an update on this topic, with focus on how pediatric IBD affects bone health.