The relationship between circulating osteoprotegerin levels and bone mineral metabolism in healthy women

Clinical Data for Parametrization of In Silico Bone Models Incorporating Cell-Cytokine Dynamics: A Systematic Review of Literature

In silico simulations aim to provide fast, inexpensive, and ethical alternatives to years of costly experimentation on animals and humans for studying bone remodeling, its deregulation during osteoporosis and the effect of therapeutics. Within the varied spectrum of in silico modeling techniques, bone cell population dynamics and agent-based multiphysics simulations have recently emerged as useful tools to simulate the effect of specific signaling pathways. In these models, parameters for cell and cytokine behavior are set based on experimental values found in literature; however, their use is currently limited by the lack of clinical in vivo data on cell numbers and their behavior as well as cytokine concentrations, diffusion, decay and reaction rates. Further, the settings used for these parameters vary across research groups, prohibiting effective cross-comparisons. This review summarizes and evaluates the clinical trial literature that can serve as input or validation for in silico models of bone remodeling incorporating cells and cytokine dynamics in post-menopausal women in treatment, and control scenarios. The GRADE system was used to determine the level of confidence in the reported data, and areas lacking in reported measures such as binding site occupancy, reaction rates and cell proliferation, differentiation and apoptosis rates were highlighted as targets for further research. We propose a consensus for the range of values that can be used for the cell and cytokine settings related to the RANKL-RANK-OPG, TGF-β and sclerostin pathways and a Levels of Evidence-based method to estimate parameters missing from clinical trial literature.

Ovariectomized Rat Model and Shape Variation in the Bony Labyrinth

Postmenopausal osteoporosis is a serious concern in aging individuals, but has not been explored for its potential to alter the shape of the inner ear by way of increased remodelling in the otic capsule. The otic capsule, or bony labyrinth, is thought to experience uniquely limited remodelling after development due to high levels of osteoprotegerin. On this basis, despite the widespread remodelling that accompanies osteoporosis, we hypothesize that both the shape and volume of the semicircular canals will resist such changes. To test this hypothesis, we conducted three-dimensional geometric morphometric shape analysis on microcomputed tomographic data collected on the semicircular canals of an ovariectomized (OVX) rat model. A Procrustes ANOVA found no statistically significant differences in shape between surgery and sham groups, and morphological disparity testing likewise found no differences in shape variation. Univariate testing found no differences in semicircular volume between OVX and control groups. The range of variation in the OVX group, however, is greater than in the sham group but this difference does not reach statistical significance, perhaps because of a combination of small effect size and low sample size. This finding suggests that labyrinthine shape remains a tool for assessing phylogeny and function in the fossil record, but that it is possible that osteoporosis may be contributing to intraspecific shape variation in the bony labyrinth. This effect warrants further exploration at a microstructural level with continued focus on variables related to remodelling. This article is protected by copyright. All rights reserved.

Detection of inflammatory biomarkers in saliva and urine: Potential in diagnosis, prevention, and treatment for chronic diseases

Inflammation is a part of the complex biological response of inflammatory cells to harmful stimuli, such as pathogens, irritants, or damaged cells. This inflammation has been linked to several chronic diseases including cancer, atherosclerosis, rheumatoid arthritis, and multiple sclerosis. Major biomarkers of inflammation include tumor necrosis factor, interleukins (IL)-1, IL-6, IL-8, chemokines, cyclooxygenase, 5-lipooxygenase, and C-reactive protein, all of which are regulated by the transcription factor nuclear factor-kappaB. Although examining inflammatory biomarkers in blood is a standard practice, its identification in saliva and/or urine is more convenient and non-invasive. In this review, we aim to (1) discuss the detection of these inflammatory biomarkers in urine and saliva; (2) advantages of using salivary and urinary inflammatory biomarkers over blood, while also weighing on the challenges and/or limitations of their use; (3) examine their role(s) in connection with diagnosis, prevention, treatment, and drug development for several chronic diseases with inflammatory consequences, including cancer; and (4) explore the use of innovative salivary and urine based biosensor strategies that may permit the testing of biomarkers quickly, reliably, and cost-effectively, in a decentralized setting.

Insulin resistance and bone strength: findings from the study of midlife in the United States

Although several studies have noted increased fracture risk in individuals with type 2 diabetes mellitus (T2DM), the pathophysiologic mechanisms underlying this association are not known. We hypothesize that insulin resistance (the key pathology in T2DM) negatively influences bone remodeling and leads to reduced bone strength. Data for this study came from 717 participants in the Biomarker Project of the Midlife in the United States Study (MIDUS II). The homeostasis model assessment of insulin resistance (HOMA-IR) was calculated from fasting morning blood glucose and insulin levels. Projected 2D (areal) bone mineral density (BMD) was measured in the lumbar spine and left hip using dual-energy X-ray absorptiometry (DXA). Femoral neck axis length and width were measured from the hip DXA scans, and combined with BMD and body weight and height to create composite indices of femoral neck strength relative to load in three different failure modes: compression, bending, and impact. We used multiple linear regressions to examine the relationship between HOMA-IR and bone strength, adjusted for age, gender, race/ethnicity, menopausal transition stage (in women), and study site. Greater HOMA-IR was associated with lower values of all three composite indices of femoral neck strength relative to load, but was not associated with BMD in the femoral neck. Every doubling of HOMA-IR was associated with a 0.34 to 0.40 SD decrement in the strength indices (p<0.001). On their own, higher levels of fasting insulin (but not of glucose) were independently associated with lower bone strength. Our study confirms that greater insulin resistance is related to lower femoral neck strength relative to load. Further, we note that hyperinsulinemia, rather than hyperglycemia, underlies this relationship. Although cross-sectional associations do not prove causality, our findings do suggest that insulin resistance and in particular, hyperinsulinemia, may negatively affect bone strength relative to load.

Relationships between age-related biochemical markers of bone turnover and OPG, TGF-β1 and TGF-β2 in native Chinese women

Osteoprotegerin (OPG), transforming growth factor-β1 (TGF-β1) and TGF-β2 are cytokines closely associated with bone metabolism. However, their association with bone turnover markers in native Chinese women remains unknown. The study aims to investigate the relationship between bone metabolism related cytokines including OPG, TGF-β1, TGF-β2 and bone turnover markers in native Chinese women. The cross-sectional study was conducted on 691 healthy Chinese women (20-80 years old). Levels of OPG, TGF-β1, TGF-β2, serum bone-specific alkaline phosphatase (BAP), osteocalcin (OC), cross-linked N-terminal telopeptides of type I collagen (sNTX), cross-linked C-terminal telopeptides of type I collagen (sCTX), urinary NTX (uNTX), urinary CTX (uCTX) and total urinary deoxypyridinoline (uDPD) were determined. The present study showed that OPG and TGF-β2 had positive correlation with BAP, OC, uNTX, uCTX and uDPD, while TGF-β1 showed negative correlation with BAP, OC, sCTX, uNTX and uCTX, and most of the coefficients of partial correlation remained significant after adjustments for age and body mass index (BMI). Multiple linear regression stepwise analysis showed that OPG and TGF-β2 were positive determinative factors for BAP, sCTX, uNTX and uCTX, which could explain 0.6-16.6% of the variation in these markers. TGF-β1 was a negative determinative factor for BAP, OC, sCTX and uCTX, which could explain 0.7-7.3% of the variation in these markers. This study suggested that measuring bone turnover indicators and serum cytokines simultaneously might help evaluating changes in bone turnover rate caused by aging or menopause in women.

OPG and sRANKL serum levels and incident hip fracture in postmenopausal Caucasian women in the Women's Health Initiative Observational Study

PURPOSE

The osteoprotogerin/receptor activator of NF-kappa β/receptor activator of NF-kappa β ligand (OPG/RANK/RANKL) pathway plays a critical role in bone remodeling. This study investigated associations between serum levels of OPG, soluble RANKL (sRANKL), and the ratio of OPG/sRANKL to risk of incident hip fracture.

METHODS

A nested case-control study was conducted among postmenopausal, Caucasian women aged 50-79 at baseline (1993-1998), followed for hip fracture through March 2005 in the Women's Health Initiative Observational Study. 400 incident hip fracture cases were selected and individually matched to 400 controls with no prior fracture or incident hip fracture. Matching factors were baseline age, enrollment date and hormone therapy (HT) exposure. Baseline serum OPG and sRANKL levels were measured using high sensitivity ELISA. Odds ratios were computed for quartiles of each biomarker adjusting for matching factors and hip fracture risk factors.

RESULTS

Serum OPG was significantly associated with older age, low physical activity and poorer physical function in control women. sRANKL was inversely associated with total calcium intake in control women, but not associated with age or other fracture risk factors. The odds ratio for hip fracture comparing the highest to lowest quartiles of OPG was 2.28 (95% confidence interval (CI), 1.45-3.61) after adjusting for the matching variables (p-value for linear trend <0.001), and 1.87 (95% CI, 1.15-3.04; p for linear trend=0.02) after adjusting for self-rated health status, physical activity and physical functioning. No significant associations between sRANKL or the ratio of OPG/sRANKL and hip fracture risk were observed.

CONCLUSION

Serum OPG levels were independently associated with a nearly twofold increased risk of hip fracture in postmenopausal women.

Osteoprotegerin is associated with hip fracture incidence: the Tromso Study

BACKGROUND

Osteoprotegerin (OPG) is a cytokine essential for the regulation of bone resorption, but large longitudinal studies on its relationship to fracture risk in humans are lacking. In this population-based study of 2740 men and 2857 post-menopausal women, it was examined whether serum OPG was associated with hip fracture incidence. The participants were followed for 15 years.

METHODS

Baseline measurements included height, weight and serum OPG, and information about lifestyle, prevalent diseases and use of medication.

RESULTS

Men with OPG in the highest quartile were 2.79-fold [95% confidence interval (CI) 1.34-5.82] more likely to have a hip fracture during follow-up, compared with those with OPG in the lowest quartile (P-trend over OPG quartiles ≤ 0.001, after adjustments for age and other confounders). In women not using post-menopausal hormone therapy (HT), the risk of hip fracture was 1.64-fold higher (95% CI 0.94-2.86) in the highest quartile compared with the lowest OPG quartile (P-trend over OPG quartiles = 0.05). No relationship was found in post-menopausal women using HT (P-trend over OPG quartiles = 0.23).

CONCLUSIONS

In men, OPG was positively associated with the incidence of hip fracture. In post-menopausal women not using HT a similar, but weaker, relationship was found.

Identifying coronary artery disease in men with type 2 diabetes: osteoprotegerin, pulse wave velocity, and other biomarkers of cardiovascular risk

OBJECTIVES

In patients with type 2 diabetes, high serum levels of osteoprotegerin (OPG) have been associated with a greater risk of cardiovascular events. However, it remains unclear how well OPG performs when compared with traditional biomarkers of cardiovascular risk such as high-sensitivity C-reactive protein (hsCRP). Furthermore, OPG levels are also high in the presence of diabetes-related microvascular disease, and it is unclear whether OPG can distinguish microvascular disease from large-vessel atherosclerosis. The first aim of this study was to compare OPG levels against other biomarkers of cardiovascular risk in the identification of patients with documented multivessel coronary artery disease (CAD). The second aim was to compare OPG levels in patients with microvascular complications (microalbuminuria) against those with established CAD.

METHODS

Three groups of male patients with type 2 diabetes were recruited: patients without microvascular complications or large-vessel atherosclerosis (n = 24), patients with microalbuminuria only (n = 23), and patients with microalbuminuria and documented multivessel CAD (n = 25). OPG, hsCRP, interleukin 6, urate, and pulse wave velocity were measured.

RESULTS

Serum OPG levels were significantly higher in patients with a combination of microalbuminuria and CAD than in those with microalbuminuria alone. There were no significant differences in any of the other biomarkers between the groups.

CONCLUSION

OPG was found to be superior to the other biomarkers studied in identifying patients with documented CAD. The presence of CAD was a greater determinant of serum OPG levels than microalbuminuria in our population. These findings support the use of OPG as a biomarker of cardiovascular risk.

Serum osteoprotegerin levels are related to height loss: the Tromsø Study

Severe loss of body height is often a consequence of osteoporotic vertebral fractures. Osteoprotegerin (OPG) and receptor activator of nuclear factor-kB ligand (RANKL) are cytokines essential for the regulation of bone resorption. The aim of this study was to assess the relationship between the OPG/RANKL system and height loss. A total of 4,435 inhabitants from the municipality of Tromsø, Norway (2,169 men and 2,266 women) were followed for 6 years. Baseline measurements included height, weight, bone mineral density, OPG, RANKL, serum parathyroid hormone and information about lifestyle, prevalent diseases and use of medication. Height was measured again at follow-up, and the loss of height was categorized into 4 groups: ≤1, 1.1-2, 2.1-3, >3 cm. We found increasing height loss with increasing baseline OPG levels in both men and women (P trend = 0.02 and 0.001, respectively), after adjustments for age and other confounders. However, when the women were stratified according to menopausal status and use of hormone replacement therapy (HRT), a significant relationship was present only among postmenopausal women not using HRT (P trend = 0.02). No relations between OPG and height loss were found in post-menopausal HRT-users and premenopausal women (P trend ≥0.39). We conclude that height loss is positively associated with OPG in men and in postmenopausal women not using HRT. No relationship was found between RANKL and height loss.

Bone loss in relation to serum levels of osteoprotegerin and nuclear factor-kappaB ligand: the Tromsø Study

SUMMARY

In this longitudinal study of 4,137 persons, bone mineral density was negatively associated with osteoprotegerin at baseline in both genders. In postmenopausal women not using hormone replacement therapy (HRT), bone-loss increased with increasing osteoprotegerin levels, whereas no relationship was found in men, premenopausal women, or postmenopausal women taking HRT.

INTRODUCTION

In a population-based study of 2,003 men and 2,134 women, the relationship between the osteoprotegerin (OPG)/factor-kappaB ligand (RANKL) system and bone mineral density (BMD) and changes in BMD was examined.

METHODS

Baseline measurements included height, weight, BMD of the forearm, OPG, RANKL, vitamin D, and serum parathyroid hormone (PTH) and information about lifestyle, prevalent diseases, and use of medication. BMD was remeasured at follow-up 6 years later.

RESULTS

BMD was negatively associated with OPG at baseline in both men and women (p trend over OPG levels = 0.01 and 0.007, respectively, after adjustments for age, and other confounders). In postmenopausal women not on hormone replacement therapy, bone loss increased with increasing OPG (p = 0.005), whereas no relationship was found in men, premenopausal women, or postmenopausal women on HRT (p >or= 0.28). BMD at baseline and BMD changes were not related to RANKL levels in any of the groups (p >or= 0.14).

CONCLUSIONS

In postmenopausal women not using HRT, bone loss associated positively with OPG. The results indicate that in women deficient in sex steroids, the OPG/RANKL system may play an important counter regulatory role in order to avoid bone loss and maintain BMD. In men and women replete in sex steroids, the OPG/RANKL system was not associated with BMD.

Biological variation and reference intervals for circulating osteopontin, osteoprotegerin, total soluble receptor activator of nuclear factor kappa B ligand and high‐sensitivity C‐reactive protein

OBJECTIVE

Monitoring inflammatory diseases and osteoclastogenesis with osteopontin (OPN), osteoprotegerin (OPG), total soluble receptor activator of nuclear factor kappa B ligand (total sRANKL) and high-sensitivity C-reactive protein (hsCRP) has recently attracted increased interest. The purpose of our study was to determine reference intervals, variability caused by sampling time, biological variation and stability after repeated freeze-thaw cycles of circulating levels of OPN, OPG, total sRANKL and hsCRP.

MATERIAL AND METHODS

Plasma OPN and plasma OPG concentrations were determined with sandwich ELISA; serum total sRANKL concentration was determined using a two-site sandwich ELISA; and hsCRP was analysed by turbidimetry in 300 Danish blood donors (183 M and 117 F) with a median age of 43 years (range 18-64 years). Variability due to biological variation and sampling time was studied in serial samples from 38 healthy subjects.

RESULTS

The 95th percentiles in the donors were 76 microg/L for OPN, 4.2 pmol/L for OPG, 40.2 nmol/L for total sRANKL and 12 mg/L for hsCRP. The overall medians for both genders were 51 microg/L, 2.2 pmol/L, 0.66 nmol/L and 1.0 mg/L, respectively. We found a significant correlation between hsCRP and OPN (rho = 0.173; p<0.003). The biological within-subject variations were calculated to be 8.2 % for OPN, 8.8% for total sRANKL and 50% for hsCRP.

CONCLUSIONS

Reference intervals have been established with a high analytic performance for OPN and an acceptable analytic performance for OPG and total sRANKL. The study revealed low biological variation for OPN and total sRANKL and high biological variation for hsCRP.

The effect of exercise and estrogen on osteoprotegerin in premenopausal women

BACKGROUND

The benefits of exercise are widely recognized, however physically active women can develop exercise associated menstrual cycle disturbances such as amenorrhea (i.e., estrogen deficiency) secondary to a chronic energy deficiency.

OBJECTIVE

To assess the effects of exercise status and estrogen deficiency on osteoprotegerin (OPG) and its relationship to bone resorption in premenopausal exercising women.

DESIGN

Cross-sectional study of serum OPG, urinary c-telopeptides (uCTX), urinary estrone 3-glucuronide (E1G), urinary pregnanediol 3-glucuronide (PdG) and bone mineral density (BMD) measured on multiple occasions in 67 women. Volunteers were retrospectively grouped: 1) sedentary menstruating group (SedMen n=8), 2) exercising menstruating group (ExMen, n=36), and 3) exercising amenorrheic group (ExAmen, n=23). One-way ANOVAs were performed, and LSD post-hoc tests were performed when differences were detected.

RESULTS

Subjects were similar with respect to age (24.2+/-1.0 years), weight (57.8+/-1.7 kg), and height (164.3+/-1.3 cm) (p>0.05). ExMen and ExAmen groups were more aerobically fit (p=0.003) and had less body fat (p=0.002) than the SedMen group. Resting energy expenditure/fat free mass was lowest (p=0.001) in the ExAmen groups. Mean E1G across the measurement period (p<0.001) and overall E1G exposure as assessed by E1G area under the curve (AUC) (p<0.001) were lower in the ExAmen group vs. the SedMen and ExMen groups. U-CTX-I was elevated (p=0.033) in the ExAmen group (281.8+/-40.3 microg/L/mmCr), compared with the SedMen and ExMen groups (184.5+/-22.4, 197.2+/-14.7 microg/L/mmCr, respectively). OPG was suppressed (p=0.005) in the ExAmen group (4.6+/-0.2 pmol/L) vs. ExMen group (5.2+/-0.2 pmol/L), and OPG was lower in the SedMen group (4.1+/-0.3 pmol/L) compared with the ExMen group. Findings were translated to BMD; the ExAmen group had suppressed total body BMD (p=0.014) and L2-L4 BMD (p=0.015) vs. the ExMen group.

CONCLUSIONS

Our results suggest that OPG responds to the bone loading effect of exercise, and that suppressed OPG may play a role in the etiology of increased bone resorption observed in exercising women with chronic estrogen deficiency secondary to hypothalamic amenorrhea.

Effect of long-term treatment with risedronate on arterial compliance in osteoporotic patients with cardiovascular risk factors

Accumulating evidence suggests that osteoporosis and coronary artery disease have epidemiologic similarities. Moreover, the anti-atherogenic effects of bisphosphonates have been observed in vitro and in animal models. The present study investigated the effect of risedronate on indices of arterial compliance, serum osteoprotegerin (OPG) level, inflammatory and metabolic parameters in osteoporotic women with cardiovascular risk factors. In an open label, prospective study 68 postmenopausal osteoporotic women were evaluated for the study. Patients received risedronate orally in a dose of 35 mg per week, daily supplements of calcium and cholecalciferol during 6month treatment period. Patients were evaluated for lipid profile, HbA1C, insulin, C-peptide, fibrinogen, hs-CRP and plasma osreoprotegerin. Arterial elasticity was evaluated using pulse wave contour analysis (HDI CR 2000, Eagan, Minnesota). Large artery elasticity index (LAEI) increased from 9.86+/-3.66 to 11.54+/-">+/-3.16 ml/mm HgX10 (p<0.0001) during treatment period. Small artery elasticity index (SAEI) increased from 2.64+/-1.10 to 3.28+/-1.16 ml/mm HgX100 (p<0.0001). Systemic vascular resistance (SVR) decreased from 1876.12+/-457.72 to 1646.12+/-260.17 dyn/s/cm(- 5) (p<0.013). Metabolic parameters did not change during the treatment period. Plasma osteoprotegerin was significantly, positively correlated to SVR at baseline (r=0.36, p=0.045). At the final visit, OPG was marginally inversely associated with LAE (r=- 0.312, p=0.09), and significantly, positively associated with total vascular impedance (r=0.43, p=0.015). In conclusion, prolonged treatment with risedronate improved arterial elasticity of small and large arteries, and decreased SVR. These beneficial vascular effects were not related to changes in cardiovascular risk factors and may be attributed to direct effects of risedronate on the vascular wall.

Changes in bone markers after once-weekly low-dose alendronate in postmenopausal women with moderate bone loss

BACKGROUND

High bone turnover, with bone resorption exceeding bone formation, is a major mechanism of postmenopausal osteoporosis. Therefore, inhibition of bone resorption is a rational approach for the prevention of bone loss. The objective of the current study was to determine the short-term efficacy of once-weekly low-dose alendronate in the prevention of bone loss, via bone turnover markers, in early postmenopausal Korean women with moderate bone loss.

METHODS

This study involved a 12-week, randomized, double-blind clinical trial that compared the effects of placebo with alendronate 20mg once weekly. All subjects received supplemental calcium 600 mg and vitamin D 400IU daily. We recruited 63 postmenopausal women (ranging from 50 to 65 years of age) with the lowest lumbar spine bone mineral density (BMD) at least 2.0 S.D. below the mean value for young healthy adults. BMD was measured at baseline and serum alkaline phosphatase (ALP), osteocalcin, C-terminal telopeptide of type I collagen (CTX), and osteoprotegerin (OPG) were measured at baseline and 12 weeks after treatment.

RESULTS

We randomly assigned 63 women to either placebo or alencronate 20 mg once a week for 3 months. Forty-nine women continued and completed all 3 months. After 3 months, bone resorption markers were significantly decreased in the alendronate group than in the placebo group: CTX -47.2% vs. 15% (p<0.01), ALP 1.6% vs. 25.9% (p=0.01), osteocalcin -29.2% vs. -13.6 (p=0.06). Women who received alendronate showed similar results to those who received placebo with regard to adverse events.

CONCLUSION

Once-weekly low-dose alendronate may be a cost-effective and safe method of suppressing bone turnover in early postmenopausal women with moderate bone loss.

Increased plasma osteoprotegerin concentrations are associated with indices of bone strength of the hip

OBJECTIVE

Osteoprotegerin (OPG) is an important regulator of bone turnover through its effects on osteoclastogenesis, yet findings from previous studies of circulating OPG and commonly measured bone indices in humans have been conflicting. We conducted a cross-sectional study to evaluate the association between plasma OPG and femoral neck (FN) bone density (BMD) and geometry in a large cohort of women and men.

DESIGN

Participants included 1379 postmenopausal women and 1165 men, aged 50-89 yr (mean, 64 yr), in the Framingham Offspring Study. Dual x-ray absorptiometry was used to evaluate FN BMD and geometry (bone width, section modulus, and cross-sectional area at the narrow neck region). Plasma OPG concentrations were measured by ELISA. Sex-specific analysis of covariance was used to calculate means and assess linear trend in BMD and geometry values across OPG quartiles, adjusted for confounders.

RESULTS

OPG concentrations were greater in women than men, increased with age, and were greater in smokers and those with diabetes and heart disease. Multivariable-adjusted mean FN BMD in women increased from the lowest to the highest OPG quartile (trend, P < 0.01). However, no linear trend between FN BMD and OPG was observed in men (trend, P = 0.34). Section modulus and bone width increased with OPG in men (trend, P < 0.01), whereas no association between hip geometry indices and OPG was observed in women.

CONCLUSION

Higher OPG concentration may indicate greater skeletal strength in women and men, possibly through reducing bone loss in women and increasing periosteal apposition in men.

Follicle-stimulating hormone does not directly regulate bone mass in human beings: evidence from nature

OBJECTIVE

To evaluate the effect of FSH levels in the development of human osteoporosis.

DESIGN

Case-series study.

SETTING

Gynecology department in a teaching hospital.

PATIENT(S)

A total of 8 women diagnosed with Kallman syndrome (KS) were compared with 11 with Turner syndrome and 11 with pure gonadal dysgenesia (GD, karyotype 46,XX).

INTERVENTION(S)

We assessed the pituitary-gonadal axis, bone turnover markers, bone mass, and patient characteristics.

MAIN OUTCOME MEASURE(S)

Bone mineral density as assessed by dual-energy X-ray absorptiometry, plasma FSH, LH, E(2), osteocalcin (BGP), and urinary type I collagen cross-linked N-telopeptide. Other biochemical markers included 25-hydroxyvitamin D, as well as parathyroid hormone and urine concentration of calcium and creatinine.

RESULT(S)

In girls with Turner syndrome and GD, FSH (64.03 +/- 29.2 and 90.08 +/- 22.41 mIU/mL, respectively) and LH (45.29 +/- 11.90 and 48.83 +/- 12.44 mIU/mL, respectively) levels were significantly higher compared with those observed in girls with KS (FSH: 1.87 +/- 0.64 and LH: 1.02 +/- 0.57), whereas no differences were detected in E(2) or bone marker levels. Bone mineral density correlated positively with FSH levels but not with E(2); however, after adjusting for previous growth-hormone therapy, these differences were not found. In addition, bone mineral density in spine and total hip was significantly lower in patients with KS.

CONCLUSION(S)

Follicle-stimulating hormone does not appear to have a major role in the development of bone loss in young women with primary amenorrhea.

Circulating leptin and osteoprotegerin levels affect insulin resistance in healthy premenopausal obese women

We investigated the relationship between circulating leptin and osteoprotegerin (OPG) levels and insulin resistance assessed by HOMA-IR in premenopausal obese and normal weight women. Thirty four obese women (age 31 +/- 8 years) (BMI 35 +/- 4 kg/m(2)) with 19 healthy controls (age 31 +/- 7 years) (BMI <25 kg/m(2)) (BMI 21 +/- 2 kg/m(2)) were included in the study. Women were healthy and had no osteoporosis. Circulating leptin levels were significantly higher in obese women (17.11 +/- 2.05 ng/mL vs. 8.38 +/- 4.71 ng/mL, p <0.0001) and decreased OPG levels were found (14.7 +/- 7.15 pg/mL vs. 19.17 +/- 6.37 pg/mL, p = 0.03). Leptin showed a positive correlation with BMI (r = 0.851, p <0.0001), waist-to-hip ratio (r = 0.692, p <0.0001), fasting insulin (r = 0.441, p <0.001), HOMA-IR (r = 0.412, p = 0.002), fibrinogen (r = 0.387, p = 0.004), uric acid (r = 0.293, p = 0.033), hematocrit (r = 0.394, p = 0.003), systolic (r = 0.504, p <0.0001), and diastolic blood pressure (r = 0.363, p = 0.008). OPG showed a negative correlation with insulin (r = -0.341, p = 0.013) and HOMA-IR (r = -0.324, p = 0.018). In obese women group, the regression equation of HOMA-IR was (HOMA-IR = [0.095 x leptin]-[0.051 x OPG] + 1.71). However, there was no relation between leptin and OPG levels. In conclusion, circulating leptin and OPG levels were related to insulin resistance in premenopausal obese women. However, leptin had no interference in OPG in premenopausal women.

The circadian rhythm of osteoprotegerin and its association with parathyroid hormone secretion

BACKGROUND

Osteoclast resorptive activity, which is known to demonstrate circadian rhythmicity, is regulated by various endocrine hormones and cytokines. PTH suppresses osteoprotegerin (OPG), a regulator of osteoclast activity that has recently been shown to have a circadian rhythm in healthy controls. We studied the differences in the relationship between PTH, OPG, and type I collagen C-telopeptide (betaCTX) over a 24-h period in premenopausal women, elderly postmenopausal women, and elderly men.

METHODS

Hourly peripheral venous blood samples were obtained from 18 healthy non-osteoporotic volunteers: premenopausal women (n = 6; mean age, 30.2 +/- 2.2 yr), postmenopausal women (n = 6; mean age, 68.2 +/- 2.6 yr), and elderly men (n = 6; mean age, 68.2 +/- 2.3 yr). Plasma PTH (1-84), OPG, betaCTX, and calcium were measured on all samples. Cosinor analysis was performed to analyze the circadian rhythm parameters. Cross-correlation analysis was used to determine the relationship between the time series of the variables.

RESULTS

The 24-h mean PTH, OPG, and betaCTX concentrations were significantly higher in postmenopausal women as compared with premenopausal women and elderly men (P < 0.001). Significant circadian rhythms were observed for PTH (P < 0.05), OPG (P < 0.05), and betaCTX (P < 0.001) in all subjects. PTH secretion was characterized by two peaks in premenopausal women and elderly men and by a sustained increase in PTH concentration in postmenopausal women. OPG secretion was circadian with a daytime increase and nocturnal decrease, and a greater percent decrease in OPG secretion was observed in the postmenopausal women between 1600 and 2400 h. OPG secretion was inversely related to PTH (r = -0.4) and betaCTX (r = -0.6) secretion over a 24-h period.

CONCLUSION

This report confirms a circadian rhythm for circulating OPG. The nocturnal decline in circulating OPG is greater in postmenopausal women as compared with premenopausal women and elderly men. Altered PTH secretion may contribute to the OPG secretory pattern in postmenopausal women resulting in increased nocturnal bone resorption.

The sex-specific association of serum osteoprotegerin and receptor activator of nuclear factor kappaB legend with bone mineral density in older adults: the Rancho Bernardo study

OBJECTIVE

The role of osteoprotegerin (OPG) and its receptor activator of nuclear factor kappaB legend (RANKL) in the regulation of bone in humans remain unclear. We examined the sex-specific associations of serum OPG, RANKL, and their ratio with bone mineral density (BMD) in older adults.

DESIGN

Participants were 681 community-dwelling adults, ages 45-90 years, who had serum OPG and RANKL measured and bone density scans in 1988-1991, with follow-up scans 5 and/or 10 years later.

METHODS

Analyses were sex-specific; women using and not using estrogen were evaluated separately. Cross-sectional analyses used multivariable regression models; longitudinal analyses used repeated measures mixed effects models.

RESULTS

In cross-sectional analyses, age- and weight-adjusted serum OPG levels were significantly positively associated with BMD at the lumbar spine in men, and at the femoral neck, total hip, and lumbar spine in women using estrogen, but not in non-users of estrogen. RANKL concentrations were significantly and inversely associated with BMD in men only, and at the total hip. Neither OPG nor RANKL was significantly associated with bone loss. Results for the RANKL/OPG ratio were the same as those for RANKL alone.

CONCLUSIONS

These results suggest a modulatory effect of both endogenous and exogenous sex hormones on the biologic interaction of OPG, RANKL, and bone.

Effects of estrogen-progestin therapy on serum levels of RANKL, osteoprotegerin, osteocalcin, leptin, and ghrelin in postmenopausal women

OBJECTIVE

The aim of this study was to evaluate the effects of estrogen-progestin therapy on serum levels of receptor-activating nuclear factor kappabeta ligand (RANKL), osteoprotegerin, osteocalcin, leptin, and ghrelin in a cross-sectional study of 99 healthy postmenopausal women conducted at the Menopause Clinic of our department.

DESIGN

In this cross-sectional, observational study, 99 participants were divided into two groups. Group A was composed of 77 postmenopausal women who had never received estrogen-progestin therapy, and group B was composed of 22 postmenopausal women who had received transdermal 17beta-estradiol at a dose of 50 microg/day in a continuous regimen for at least 24 months and nomegestrol at a dose of 5 mg/day for 12 days/month in a sequential regimen. All participants underwent blood sampling in the morning and quantitative ultrasound bone-densitometry measurement of the proximal phalanges of the dominant hand.

RESULTS

T score and amplitude-dependent speed of sound were significantly higher in group B than in group A. No significant differences in RANKL, osteoprotegerin, and osteocalcin were observed between the two groups. Serum leptin levels were significantly lower in group B than in group A, whereas ghrelin was significantly higher in group B than in group A.

CONCLUSIONS

The data gathered in this preliminary study indicate that estrogen-progestin therapy may protect against postmenopausal bone loss, but this protective effect does not seem to be exerted through action on the RANK-RANKL-osteoprotegerin system. Similarly, although several reports suggest that leptin and ghrelin are involved in bone metabolism, we could not detect any important correlation of these two hormones with bone metabolism or bone status in treated and untreated postmenopausal women. Because of the limited number of treated participants and the study design, the results of this preliminary study must be confirmed in larger, prospective, longitudinal studies.

Raloxifene therapy interacts with serum osteoprotegerin in postmenopausal women

OBJECTIVES

Osteoprotegerin (OPG) is a protein expressed by osteoblasts that, linking the receptor activator of nuclear factor kappaB (RANK) ligand (RANKL), produced by osteoblasts, blocks the process of osteoclastic differentiation and modulates osteoclastic apoptosis. Raloxifene (RAL) stimulates the production of OPG from osteoblasts, as demonstrated in vitro, carring out their antiresorption activity, at least in part, as means of the OPG/RANK/RANKL system. The aim of this study was to evaluate in vivo if the RAL treatment of postmenopausal women was associated to changes in serum OPG; moreover, to evaluate the serum changes of bone turnover modulators interleukin-6 (IL-6) and C-telopeptides of type-1 collagen (CrossLaps).

METHODS

A prospective, randomized, placebo-controlled study was designed. A group of consecutive healthy postmenopausal women (n=40) referred to II Menopause Centre of the Department of Gynaecology of Second University of Naples for climacteric syndrome was enrolled and divided in two groups: (n=20) postmenopausal women received for 6 months oral raloxifene (60 mg/day) versus (n=20) postmenopausal women received placebo tablets.

RESULTS

Serum OPG levels in postmenopausal women after RAL treatment are statistically significant increased (P<0.001) versus baseline (P=0.007) versus placebo.

CONCLUSIONS

These in vivo data demonstrate that RAL could improve osteoporosis, also through an increase of OPG production by osteoblasts.

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.

Serum markers of bone turnover in dialyzed patients separated according to age

BACKGROUND

Bone metabolism changes with aging in healthy population. Our aim was to determine serum markers of bone turnover in dialysis patients separated according to age.

METHODS

Peritoneal dialysis (PD) or hemodialysis (HD) patients were divided into two groups. Group I (n = 30) consisted of patients older than 65 years. Patients at the age less or equal 65 years were included in group II (n = 37). In all patients we determined serum concentration of intact parathyroid hormone (iPTH), cyclase activating parathyroid hormone (CAP), osteoprotegrin (OPG) and osteoprotegrin ligand (OPGL). Cyclase inactive parathyroid hormone (CIP) was calculated. Healthy volunteers (n = 13) at the age of 42.1 years (range 23.5-70.9 years) served as controls.

RESULTS

When results of dialysis patients were adjusted to gender, dialysis modality and duration, group I revealed significantly lower iPTH (113.0, 10.3-606.3 pg/ml), CAP (70.0, 6.5-442.6 pg/ml) and CIP (53.3, 3.3-214.4 pg/ml) than group II (310.6, 13.7-1266.9 pg/ml for iPTH; 205.0, 9.3-887.9 pg/ml for CAP; 76.0, 2.4-399.0 pg/ml for CIP), but this group showed significantly higher serum OPG (7.39, 1.52-15.84 pg/ml) than group II (5.45, 0.95-16.47 pg/ml) and controls (2.17, 1.05-3.95 pg/ml). Only patients of group II showed significantly higher iPTH, CAP and CIP than controls (34.9, 18.9-76.9 pg/ml; 24.3, 11.2-42.6 pg/ml, 12.0, 1.0-34.2 pg/ml, respectively for iPTH, CAP and CIP).

CONCLUSION

Our results suggest that age over 65 years is a risk factor for low bone turnover in dialyzed patients. An increase in serum OPG probably reflects a paracrine mechanism of bone cells to compensate for age dependent bone loss.

The relationship between four single nucleotide polymorphisms in the promoter region of the osteoprotegerin gene and aortic calcification or coronary artery disease in Koreans

OBJECTIVE

Osteoprotegerin (OPG) is a recently identified cytokine that acts as a decoy receptor for the receptor activator of the NF-kappaB ligand (RANKL). OPG has been shown to be an important inhibitor of osteoclastogenesis and arterial calcification in animal models. OPG has been proposed as a link molecule between osteoporosis and arterial calcification, but the relationship between the OPG gene and the cardiovascular system in human populations is unclear. Thus, the aim of this study was to investigate the relationship between OPG gene polymorphisms and aortic calcification or coronary artery disease in Koreans.

DESIGN AND PATIENTS

Genotyping of four polymorphisms, A163G, G209A, T245G and T950C, in the promoter region of the OPG gene was performed in 251 healthy Korean women (mean age 51.3 +/- 6.9 years) and in a second study population consisting of 100 patients who underwent coronary angiography (mean age 57.0 +/- 11.9 years), by allelic discrimination using the 5' nuclease polymerase chain reaction assay. Cardiovascular risk factors and serum OPG levels were measured and aortic calcification in thoracic and abdominal aorta was examined by simple radiological methods.

RESULTS

In the first study population, the prevalence of aortic calcification increased significantly as the subjects grew older. The frequencies of mutant alleles were significantly higher in the subjects with aortic calcification compared with those without aortic calcification in G209A and T950C polymorphisms, although these significances were lost after adjustment for age. No significant relationship was found between OPG gene polymorphisms and serum OPG levels or cardiovascular risk factors. In the second study group, there were no associations between OPG promoter genotypes and aortic calcification, serum OPG levels, or coronary artery disease.

CONCLUSIONS

We observed that the four polymorphisms in the promoter region of the OPG gene were not associated with aortic calcification or coronary artery disease in Koreans. Further studies are needed to clarify this relationship.