Increased serum osteoprotegerin values in long-lived subjects: different effects of inflammation and bone metabolism

Systemic Bone Density at Disease Onset Is Associated With Joint Erosion Progression in Early Naive to Treatment Rheumatoid Arthritis: A Prospective 12-Month Follow-Up Open-Label Study

Objectives: Osteoporosis and bone erosions are hallmarks of rheumatoid arthritis (RA) since disease onset is underpinned by the inflammatory burden. In this observational study, we aimed to dissect the putative RA-related parameters and bone-derived biomarkers associated with systemic and focal bone loss at disease onset and with their progression.

Methods: One-hundred twenty-eight patients with early rheumatoid arthritis (ERA) were recruited at disease onset. At study entry, demographic, clinical, and immunological parameters were recorded. Each ERA patient underwent plain X-rays of the hands and feet at study entry and after 12 months to assess the presence of erosions. After enrollment, each patient was treated according to the recommendations for RA management and followed up based on a treat-to-target (T2T) strategy. At baseline, blood samples for soluble biomarkers were collected from each patient, and plasma levels of osteoprotegerin (OPG), receptor activator of nuclear factor κB ligand (RANKL), Dickkopf-1 (DKK1), and interleukin 6 (IL-6) were assessed by enzyme-linked immunosorbent assay (ELISA). Seventy-one ERA patients underwent bone mineral density (BMD) measurement at the left femoral neck and second to fourth lumbar spine vertebrae (L2–L4) by dual-energy X-ray absorptiometry (DXA).

Results: Among the whole cohort, 34 (26.6%) ERA patients with bone erosions at study entry had a higher disease activity (p = 0.02) and IL-6 plasma levels (p = 0.03) than non-erosive ones. Moreover, at DXA, 33 (46.5%) ERA patients had osteopenia, and 16 (22.5%) had osteoporosis; patients with baseline bone erosions were more likely osteopenic/osteoporotic than non-erosive ones (p = 0.03), regardless of OPG, RANKL, and DKK1 plasma levels. Obese ERA patients were less likely osteopenic/osteoporotic than normal weight ones (p = 0.002), whereas anti-citrullinated protein antibodies (ACPA) positive ERA patients were more likely osteopenic/osteoporotic than ACPA negative ones (p = 0.034). At logistic regression analysis, baseline Disease Activity Score measured on 44 joints (DAS44) [OR: 2.46 (1.11–5.44)] and osteopenic/osteoporosis status [OR: 7.13 (1.27–39.94)] arose as independent factors of erosiveness. Baseline osteopenic/osteoporotic status and ACPA positivity were associated with bone damage progression during the follow-up.

Conclusions: Bone erosions presence is associated with systemic bone loss since the earliest phases of RA, suggesting that the inflammatory burden and autoimmune biology, underpinning RA, represent crucial enhancers of bone remodeling either locally as at systemic level.

Reproductive and Lifestyle Factors and Circulating sRANKL and OPG Concentrations in Women: Results from the EPIC Cohort

BACKGROUND

Except for a documented increase in osteoprotegerin (OPG) concentrations with older age, data on determinants of soluble Receptor Activator of Nuclear Factor κB (sRANKL) and OPG concentrations in women are limited. We evaluated reproductive and lifestyle factors as potential sources of variation in circulating sRANKL and OPG concentrations in pre- and postmenopausal women.

METHODS

This study includes 2,016 controls [n = 1,552 (76%) postmenopausal, n = 757 (38%) using postmenopausal hormone therapy (PMH)] from a breast cancer case-control study nested in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Serum sRANKL was measured using an ELISA and serum OPG using an electrochemiluminescent assay. Generalized linear models were used to evaluate associations between these analytes and reproductive and lifestyle factors.

RESULTS

Older age at blood collection was associated with lower sRANKL concentrations in postmenopausal women (P trend ≤ 0.03) and higher OPG concentrations in all women (P trend ≤ 0.01). Longer duration of oral contraceptive use among premenopausal women and postmenopausal PMH users was associated with higher OPG (P trend ≤ 0.04). In postmenopausal non-PMH users, sRANKL concentrations were lower with longer duration of oral contraceptive use and current (vs. never) smoking (P ≤ 0.01). sRANKL concentrations were higher among women with higher BMI (P trend ≤ 0.01). The evaluated factors accounted for 12% of the variation in sRANKL concentrations and 21% of the variation in OPG concentrations.

CONCLUSIONS

Circulating sRANKL and OPG concentrations are minimally impacted by hormone-related factors in pre- and postmenopausal women.

IMPACT

This study suggests circulating concentrations of sRANKL and OPG are unlikely to be strongly modified by hormone-related reproductive and lifestyle factors.

Circulating levels of dickkopf-1, osteoprotegerin and sclerostin are higher in old compared with young men and women and positively associated with whole-body bone mineral density in older adults

Bone mineral density declines with increasing older age. We examined the levels of circulating factors known to regulate bone metabolism in healthy young and older adults. The circulating levels of dickkopf-1, osteocalcin, osteoprotegerin and sclerostin were positively associated with whole-body bone mineral density (WBMD) in older adults, despite the average WBMD being lower and circulating dickkopf-1, osteoprotegerin and sclerostin being higher in old than young.

INTRODUCTION

This study aims to investigate the relationship between whole-body bone mineral density (WBMD) and levels of circulating factors with known roles in bone remodelling during 'healthy' ageing.

METHODS

WBMD and fasting plasma concentrations of dickkopf-1, fibroblast growth factor-23, osteocalcin, osteoprotegerin, osteopontin and sclerostin were measured in 272 older subjects (69 to 81 years; 52% female) and 171 younger subjects (18-30 years; 53% female).

RESULTS

WBMD was lower in old than young. Circulating osteocalcin was lower in old compared with young, while dickkopf-1, osteoprotegerin and sclerostin were higher in old compared with young. These circulating factors were each positively associated with WBMD in the older adults and the relationships remained after adjustment for covariates (r values ranging from 0.174 to 0.254, all p < 0.01). In multivariate regression, the body mass index, circulating sclerostin and whole-body lean mass together accounted for 13.8% of the variation with WBMD in the older adults. In young adults, dickkopf-1 and body mass index together accounted for 7.7% of variation in WBMD.

CONCLUSION

Circulating levels of dickkopf-1, osteocalcin, osteoprotegerin and sclerostin are positively associated with WBMD in community-dwelling older adults, despite the average WBMD being lower and circulating dickkopf-1, osteoprotegerin and sclerostin being higher in old than young.

Cystatin C as a potential predictor of osteoprotegerin levels in healthy men, a cross-sectional, observational study

Background

The aim of the present study is to evaluate serum osteoprotegerin (OPG) and soluble receptor activator of nuclear factor κB ligand (sRANKL) levels in a randomly selected male cohort over 50 years of age and its association with cystatin C, a cysteine proteinase inhibitor that decreases formation of osteoclasts by interfering at a late stage of pre-osteoclast differentiation, apart from being a marker of renal function independent of gender, muscle mass and age; in addition to known predictors such as age, sex hormones, vitamin D, bone mineral density (BMD) and biochemical markers of bone turnover.

Methods

We determined serum OPG and sRANKL levels and examined its relationship with cystatin C, age, osteocalcin, C-terminal telopeptides of type-I collagen, procollagen type 1 amino-terminal propeptide, 25-hydroxyvitamin D, parathyroid hormone, total 17β-estradiol (E2), total testosterone and L1–L4 (LS) and femur neck (FN) BMD data available from 194 (age, range: 51–81 years) randomly selected ambulatory men belonging to the HunMen cohort.

Results

OPG correlated significantly with age (Spearman’s rho (r) = 0.359, p < 0.001), cystatin C (r = 0.298, p < 0.001), E2 (r = 0.160, p = 0.028) and free testosterone index (FTI) (r = −0.230, p = 0.001). Compared to the middle-aged (age: ≤ 59 years, n = 98), older men (age > 59 years, n = 96) had significantly higher serum OPG (4.6 pmol/L vs. 5.4 pmol/L; p < 0.001), and lower sRANKL (0.226 pmol/L vs. 0.167 pmol/L; p = 0.048) levels. The older men showed a significant correlation between serum OPG levels and cystatin C (Spearman’s rho = 0.322, p = 0.002), and E2 (Spearman’s rho = 0.211, p = 0.043). Including cystatin C and E2 in a regression model showed that cystatin C (standard regression coefficient (β) = 0.345; p = 0.002) was the only significant predictor of serum OPG levels in the older men.

Conclusions

The results of this study demonstrated that in addition to age (which was the stronger predictor), other modifiable factors such as cystatin C, FTI and E2 were also significant predictors of OPG, and that the association between cystatin C and OPG was more evident with increased age (older age group). As such, cystatin C is a significant predictor of OPG independently of age, FTI and E2.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-015-0684-1) contains supplementary material, which is available to authorized users.

Aging affects the phenotypic characteristics of human periodontal ligament cells and the cellular response to hormonal stimulation in vitro

BACKGROUND AND OBJECTIVE

Aging modulates the proliferative activity and organic matrix production of cells in vivo and in vitro. Here, we explore how aging affects the phenotypic characteristics of human periodontal ligament cells and their response to hormonal stimulation.

MATERIAL AND METHODS

Fifth passage periodontal ligament cells from subjects aged 12-14 (group 1), 41-55 (group 2) and 61-70 years (group 3) were characterized for the expression of mesenchymal marker genes and proteins by real-time PCR and flow cytometry. Confluent cultures were exposed to 10(-12) m parathyroid hormone(1-34) [PTH(1-34)] intermittently for three cycles. At harvest, cell number, alkaline phosphatase activity and osteocalcin production were determined by cell count, biochemical assay and ELISA.

RESULTS

The characterization of the cells revealed a decreased expression of osteoblast-specific marker genes along with a lower percentage of cells presenting the respective proteins with age. An intermittent exposure of the cultures to 10(-12) m PTH(1-34) induced an increase of the cell number as opposed to a significant decrease of alkaline phosphatase activity and osteocalcin production. The cellular response to PTH(1-34) was strongest in group 1. Basal osteoprotegerin levels were highest in the cultures from the oldest donors and inhibited by intermittent PTH(1-34) in all groups.

CONCLUSION

Our data indicate that periodontal ligament cells from older subjects display a less differentiated phenotype and a reduced response to intermittent PTH, suggesting a compromised ability to maintain tissue homeostasis and a limited possibility to support periodontal repair processes with age. The high basal osteoprotegerin expression in older subjects might serve as a compensatory mechanism.

Increased osteoprotegerin levels in women with previous gestational diabetes developing metabolic syndrome

Osteoprotegerin (OPG), a novel soluble member of tumour necrosis factor receptor superfamily, has been shown to link cardiovascular disorders. The aim of this study is to investigate the potential relationship between serum OPG levels, cardiovascular risk factors and metabolic syndrome in a relatively large group of women with previous GDM. In this cross-sectional case-control study, 128 women with previous GDM and 67 age-matched controls were enrolled. Subjects were evaluated for the diagnosis of metabolic syndrome according to the criteria of the American Heart Association (AHA). Fasting glucose, insulin, serum lipids, CRP and OPG were assayed. HOMA score was calculated. Carotid intima media thickness (IMT) was measured. There was no significant increase in OPG levels in women with previous GDM when compared to controls. On the other hand, women with previous GDM developing metabolic syndrome had higher OPG levels than those without metabolic syndrome and healthy controls. Serum OPG levels were associated with obesity, insulin resistance, serum CRP and carotid IMT. Serum OPG is related to cardiovascular risk factors and metabolic syndrome, and might be involved in the development of cardiovascular disorders in women with previous GDM.

Receptor activator of nuclear factor-κB ligand and osteoprotegerin: maintaining the balance to prevent bone loss

Bone remodeling requires a precise balance between resorption and formation. It is a complex process that involves numerous factors: hormones, growth factors, vitamins, and cytokines, and notably osteoprotegerin (OPG) and receptor activator for nuclear factor-κB (RANK) ligand. The signaling pathway OPG/RANK/RANKL is key to regulation for maintaining the balance between the activity of osteoblasts and osteoclasts in order to prevent bone loss and ensure a normal bone turnover. In this review, the RANK/RANKL/OPG pathway is described. The multiple interactions of various factors (hormones, cytokines, growth factors, and vitamins) with the OPG/RANK/RANKL pathway are also commented on. Finally, the effects of denosumab, a human monoclonal antibody that binds to RANKL and thereby inhibits the activation of osteoclasts, and of strontium ranelate are also described. Indeed, these two new drugs afford appreciable assistance in daily care practice, helping to prevent bone loss in patients with osteoporosis.

Relationships among serum receptor of nuclear factor-kappaB ligand, osteoprotegerin, high-sensitivity C-reactive protein, and bone mineral density in postmenopausal women: osteoimmunity versus osteoinflammatory

OBJECTIVE

The aim of this study was to investigate the correlations among circulating osteoprotegerin (OPG), the receptor activator of nuclear factor-kappaB ligand (RANKL), high-sensitivity C-reactive protein (hsCRP), and bone mineral density (BMD) in healthy postmenopausal women.

METHODS

In a population-based study, highly specific enzyme-linked immunosorbent assay methods were used to evaluate the sera of 382 healthy Iranian postmenopausal women (mean age +/- SD, 58.7 +/- 7.5 y) for RANKL, OPG, hsCRP, degradation products of C-terminal telopeptides of type I collagen, and osteocalcin. BMD was determined for the lumbar spine (L2-L4) and the proximal femur using dual-energy x-ray absorptiometry.

RESULTS

Circulating levels of OPG (r = 0.30, P < 0.001) and the RANKL/OPG ratio (r = -0.17, P < 0.001) were significantly associated with age. The geometric mean of hsCRP was 1.89 mg/L (SE, 1.05) in the population studied. There was a significant correlation between log(hsCRP) levels and body mass index (BMI; r = 0.36, P < 0.001). Multivariate linear analyses revealed that age (beta = -0.295, P < 0.001), BMI (beta = 0.464, P < 0.001), RANKL (beta = -0.105, P = 0.014), and OPG (beta = 0.098, P = 0.029) were the independent determinants for lumbar BMD (R(2) = 0.35). Age (beta = -0.250, P < 0.001), BMI (beta = 0.486, P < 0.001), and RANKL (beta = -0.110, P = 0.009) were independently correlated with femoral neck BMD (R(2) = 0.36). Age- and BMI-adjusted analysis by quartiles of log-transformed hsCRP did not reveal an association with BMD, serum levels of biochemical markers of bone turnover, RANKL, or OPG.

CONCLUSIONS

The circulating levels of the RANKL/OPG osteoimmunity system have an association with BMD, but subclinical systemic inflammation may not be involved in bone mass in healthy postmenopausal women.

Testing of the OMERACT 8 Draft Validation Criteria for a Soluble Biomarker Reflecting Structural Damage in Rheumatoid Arthritis: A Systematic Literature Search on 5 Candidate Biomarkers

Objective.

To test the OMERACT 8 draft validation criteria for soluble biomarkers by assessing the strength of literature evidence in support of 5 candidate biomarkers.

Methods.

A systematic literature search was conducted on the 5 soluble biomarkers RANKL, osteoprotegerin (OPG), matrix metalloprotease (MMP-3), urine C-telopeptide of types I and II collagen (U-CTX-I and U CTX-II), focusing on the 14 OMERACT 8 criteria. Two electronic voting exercises were conducted to address: (1) strength of evidence for each biomarker as reflecting structural damage according to each individual criterion and the importance of each individual criterion; (2) overall strength of evidence in support of each of the 5 candidate biomarkers as reflecting structural damage endpoints in rheumatoid arthritis (RA) and identification of omissions to the criteria set.

Results.

The search identified 111 articles. The strength of evidence in support of these biomarkers reflecting structural damage was low for all biomarkers and was rated highest for U-CTX-II [score of 6.5 (numerical rating scale 0–10)]. The lowest scores for retention of specific criteria in the draft set went to criteria that refer to the importance of animal studies, correlations with other biomarkers reflecting damage, and an understanding of the metabolism of the biomarker.

Conclusion.

Evidence in support of any of the 5 tested biomarkers (MMP-3, CTX-I, CTX-II, OPG, RANKL) was inadequate to allow their substitution for radiographic endpoints in RA. Three of the criteria in the draft criteria set might not be required, but few omissions were identified.

Involvement of molecular mimicry between human T-cell leukemia virus type 1 gp46 and osteoprotegerin in induction of hypercalcemia

Human T-cell leukemia virus type-1 (HTLV-1) causes adult T-cell leukemia/lymphoma (ATL), frequently associated with hypercalcemia and bone destruction. A positive correlation between the appearance of an antibody recognizing the central region (Asp197 to Leu216) on Gp46, gp46-197, and the severity of ATL has been demonstrated. In this study, five male Nihon Hakusyoku rabbits were immunized with a synthetic peptide corresponding to the gp46-197 region to clarify its action and mechanism. Two of the rabbits showed piloerection, anorexia, and somnolence, and died soon after booster administration. The serum calcium level of the dead rabbits was significantly high, compared to those of surviving rabbits. Interestingly, amino acid sequences homologous with gp46-197 were found in the carboxyl-terminal half of osteoprotegerin (OPG), an osteoclast inhibitory factor. To confirm the effect of the gp46-197 region on osteogenesis in vivo, the peptide was intraperitoneally administered to male Sprague-Dawley rats. The administration of the gp46-197 peptide resulted in a decrease of bone mineral density (BMD), a significant increase of serum calcium level, and inhibition of normal bone growth in both short- and long-term experiments. In rats, femoral growth inhibition by the gp46-197 peptide was restored by the coadministration of recombinant human OPG. Improvement by OPG in the adverse effect indicates that the central region of HTLV-1 Gp46 acts as an antagonist for OPG and leads to hypercalcemia.

Calcium metabolism and vitamin D in the extreme longevity

Skeletal remodelling is a continuous process during life and is still active also in extreme senescence. In the elderly, bone resorption often prevails over bone formation, causing bone loss and fragility. Elderly subjects are exposed to the risk of fractures, and loss of self-sufficiency, if considering that the proximal femur is the most frequently involved site. Bone remodelling can maintain circulating calcium within physiological ranges, at the expense of a substantial loss of this ion from the skeleton, particularly during senescence. Calcium metabolism is regulated at cellular/molecular level by a network of cytokines, growth factors, systemic hormones that act on bone in paracrine/autocrine/systemic fashion. Among the molecules involved in bone metabolism, parathyroid hormone (PTH) and vitamin D present some peculiar aspects during senescence. The osteometabolic features in a consistent group of centenarians have been evaluated. It results that a severe hypovitaminosis D was present in 99 out of 104 centenarians (25-OH vitamin D below 5 nmol/L), and that it plays an important role as a factor inducing a vicious circle involving hypocalcemia, secondary hyperparathyroidism, together with biochemical features indicating a consistent bone loss. Serum C-terminal cross-linking telopeptide, a specific marker of bone resorption was elevated in 92% of these subjects. Moreover, it has been found that several femoral fractures had occurred after 90 years of age. These data offer a rational for the possible prevention of elevated bone turnover, bone loss and consequently the reduction of osteoporotic fractures and fractures-induced disability, in the oldest olds, through the simple supplementation with calcium and vitamin D.

Serum osteoprotegerin levels in patients with acute atherothrombotic stroke and lacunar infarct

BACKGROUND

Arterial calcification is associated with increased risk of cardiovascular events. Osteoprotegerin (OPG) is a cytokine involved in the bone metabolism and vascular calcification. Recent data support a relationship between high serum levels of OPG and increased risk for cardiovascular disease in human. The aim of this study was to evaluate the OPG serum levels in acute ischemic stroke. Our study was further designed to detect differences in serum OPG levels between subtypes of ischemic stroke.

MATERIALS AND METHODS

The study consisted of 51 patients with acute ischemic stroke and 28 control subjects. Stroke subtypes were defined by the TOAST classifications. Serum OPG levels were measured with the ELISA method.

RESULTS

OPG serum levels were significantly higher in patients with ischemic stroke than in control subjects (p<0.001). OPG serum levels were significantly higher in large-vessel disease (LVD) subtype compared with small-vessel disease (SVD) subtype and controls (p<0.001, p<0.001). There was no significant difference in OPG serum levels between SVD group and control subjects. Serum OPG levels were correlated with age (r=0.407, p=0.005) and fasting glucose levels (r=0.542, p=0.001) in ischemic stroke group. Logistic regression analysis showed that plasma OPG levels (OR 2.1, 95% CI, 1.16 to 3.4, p=0.01) associated with presence of stroke independently of the other risk factors.

CONCLUSIONS

High serum OPG levels were associated with the LVD stroke subtype, suggesting that OPG levels may play role in pathogenesis of atherothrombotic stroke. The precise mechanism for the role of OPG in atherosclerosis needs to be investigated further.