High bone turnover is associated with low bone mass and spinal fracture in postmenopausal women

Association of Insulin Resistance and β-cell Function With Bone Turnover Biomarkers in Dysglycemia Patients

BACKGROUND

The interrelation between glucose and bone metabolism is complex and has not been fully revealed. This study aimed to investigate the association between insulin resistance, β-cell function and bone turnover biomarker levels among participants with abnormal glycometabolism.

METHODS

A total of 5277 subjects were involved through a cross-sectional study (METAL study, http://www.chictr.org.cn, ChiCTR1800017573) in Shanghai, China. Homeostasis model assessment of insulin resistance (HOMA-IR) and β-cell dysfunction (HOMA-%β) were applied to elucidate the nexus between β-C-terminal telopeptide (β-CTX), intact N-terminal propeptide of type I collagen (P1NP) and osteocalcin (OC). β-CTX, OC and P1NP were detected by chemiluminescence.

RESULTS

HOMA-IR was negatively associated with β-CTX, P1NP and OC (regression coefficient (β) -0.044 (-0.053, -0.035), Q4vsQ1; β -7.340 (-9.130, -5.550), Q4vsQ1 and β -2.885 (-3.357, -2.412), Q4vsQ1, respectively, all P for trend <0.001). HOMA-%β was positively associated with β-CTX, P1NP and OC (β 0.022 (0.014, 0.031), Q4vsQ1; β 6.951 (5.300, 8.602), Q4vsQ1 and β 1.361 (0.921, 1.800), Q4vsQ1, respectively, all P for trend <0.001).

CONCLUSIONS

Our results support that lower bone turnover biomarker (β-CTX, P1NP and OC) levels were associated with a combination of higher prevalence of insulin resistance and worse β-cell function among dysglycemia patients. It is feasible to detect bone turnover in diabetes or hyperglycemia patients to predict the risk of osteoporosis and fracture, relieve patients' pain and reduce the expenses of long-term cure.

The Effect of Clothing on Vitamin D Status, Bone Turnover Markers, and Bone Mineral Density in Young Kuwaiti Females

Many Arab women in the Gulf region cover their bodies for cultural and religious reasons, limiting the skin's exposure to sunlight and therefore its ability to synthesize vitamin D. The aim of this study is to determine whether the clothing style of Kuwaiti premenopausal women affects their vitamin D status, bone marker expression, and bone density. Three groups of healthy unmarried single Kuwaiti females (20-35 years old; n=30 per group) were recruited randomly from the general community: a control group who wear Western-style clothing (unveiled group), a group who wear a hejab that covers the whole body except for the face and hands (hejab group), and a group who wear a black veil with the entire body covered (veiled group). Bone mineral density (BMD), bone markers (procollagen type 1 N-terminal propeptide [P1NP], osteocalcin, and β-CrossLaps), 25-hydroxy vitamin D, intact parathyroid hormone [iPTH], and calcitonin were measured. The bone marker osteocalcin was significantly higher in the hejab group compared to the control group, whereas P1NP and β-CrossLaps were significantly higher in the veiled group compared to the control group. 25-hydroxy vitamin D, iPTH, calcitonin, and BMD were not significantly different across the three groups despite the observed elevation in bone turnover markers. The majority of participants in all three groups exhibited vitamin D deficiency; however, the lowest vitamin D levels were observed among the hejab and veiled participants. These findings suggest that clothing style may contribute to vitamin D deficiency in young Kuwaiti women.

Comparison of combined low-dose hormone therapy vs. tibolone in the prevention of bone loss

OBJECTIVES

To compare the effects on bone mineral density (BMD) measured by dual-energy X-ray absorptiometry at the lumbar spine, the femoral neck and the total hip following 2 years of treatment with a low-dose combined hormone therapy (HT) comprised of 1 mg estradiol and 0.5 mg norethisterone acetate (E2/NETA) versus 2.5 mg tibolone in postmenopausal women. Additionally, quantitative ultrasonometry (QUS) of the os calcaneus and of the phalanges was performed.

METHODS

Changes in BMD, QUS and side-effects were assessed at baseline, 6, 12 and 24 months in 50 postmenopausal women who received either E2/NETA (n = 26) or tibolone (n = 24) for 2 years.

RESULTS

Compared to women on tibolone, women receiving E2/NETA showed a significant increase in BMD from baseline to 12 and 24 months at the lumbar spine (3.07%, 3.86%; p < 0.01 vs. 1.13%, 2.23%; p < 0.05), and at the total hip (1.33%, 1.69%; p < 0.01 vs. 0.76%, 0.70%) and at the femoral neck from baseline to 24 months (1.10%; p < 0.05). QUS indices only showed a significant change with the ultrasound bone profile index with E2/NETA at 6 months (-2.32%; p < 0.001).

CONCLUSIONS

Low-dose E2/NETA showed a significantly higher increase in BMD compared to tibolone. QUS measurement was not considered to comprise beneficial effects in monitoring drug-induced bone changes.

Effect of Concurrent Use of Whole-Body Vibration and Parathyroid Hormone on Bone Structure and Material Properties of Ovariectomized Mice

This study was designed to determine the effectiveness of whole-body vibration (WBV) and intermittent parathyroid hormone (iPTH) in combination against estrogen deficiency-induced osteoporosis. Female C57BL/6J mice were bilaterally ovariectomized (OVX, n = 40) or sham-operated (sham-OVX, n = 8) at 9 weeks of age. Two weeks later, the OVX mice were randomly divided into four groups (n = 10 each): the control group (c-OVX) and groups treated with iPTH (p-OVX), WBV (w-OVX) and both (pw-OVX). The p-OVX and pw-OVX groups were given human PTH (1-34) at a dose of 30 µg/kg/day. The w-OVX and pw-OVX groups were exposed to WBV at an acceleration of 0.3 g and 45 Hz for 20 min/day. All mice were euthanized after the 18-day treatment, and the left tibiae were harvested. The proximal metaphyseal region was µCT-scanned, and its cortical bone cross-section was analyzed by Fourier transform infrared microspectroscopy and nanoindentation testing. A single application of iPTH or WBV to OVX mice had no effect on bone structure or material properties of cortical bone, which were compromised in comparison to those in sham-OVX mice. The combination of iPTH and WBV improved trabecular bone volume, thickness, and connectivity in OVX mice. Although the combined treatment failed to improve cortical bone structure, its mineral maturity and hardness were restored to the levels observed in sham-OVX mice. There was no evidence of interaction between the two treatments, and the combined effects seemed to be additive. These results suggest combining WBV with iPTH has great potential for treating postmenopausal osteoporosis.

Osteocyte-derived insulin-like growth factor I is not essential for the bone repletion response in mice

The present study sought to evaluate the functional role of osteocyte-derived IGF-I in the bone repletion process by determining whether deficient expression of Igf1 in osteocytes would impair the bone repletion response to one week of dietary calcium repletion after two weeks of dietary calcium deprivation. As expected, the two-week dietary calcium depletion led to hypocalcemia, secondary hyperparathyroidism, and increases in bone resorption and bone loss in both Igf1 osteocyte conditional knockout (cKO) mutants and WT control mice. Thus, conditional disruption of Igf1 in osteocytes did not impair the calcium depletion-induced bone resorption. After one week of calcium repletion, both cKO mutants and WT littermates showed an increase in endosteal bone formation attended by the reduction in osteoclast number, indicating that deficient Igf1 expression in osteocytes also did not have deleterious effects on the bone repletion response. The lack of an effect of deficient osteocyte-derived IGF-I expression on bone repletion is unexpected since previous studies show that these Igf1 osteocyte cKO mice exhibited impaired developmental growth and displayed complete resistance to bone anabolic effects of loading. These studies suggest that there is a dichotomy between the mechanisms necessary for anabolic responses to mechanical loading and the regulatory hormonal and anabolic skeletal repletion following low dietary calcium challenge. In conclusion, to our knowledge this study has demonstrated for the first time that osteocyte-derived IGF-I, which is essential for anabolic bone response to mechanical loading, is not a key regulatory factor for bone repletion after a low calcium challenge.

Effects of high phosphorus diet on bone metabolism-related gene expression in young and aged mice

In this study, the effects of high phosphorus (P) diet on bone metabolism-related gene expression were investigated in young and aged mice. Twelve- and 80-week-old ddY male mice were divided into two groups, respectively, and fed a control diet containing 0.3% P or a high P diet containing 1.2% P. After 4 weeks of treatment, serum parathyroid hormone (PTH) concentration was significantly higher in the high P groups than in the control groups in both young and aged mice and was significantly higher in aged mice than in young mice fed the high P diet. High P diet significantly increased receptor activator of NF-κB ligand (RANKL) mRNA in the femur of both young and aged mice and significantly increased the RANKL/osteoprotegerin (OPG) mRNA ratio only in aged mice. High P diet significantly increased mRNA expression of transient receptor potential vanilloid type 6, calbindin-D9k, and plasma membrane Ca(2+)-ATPase 1b in the duodenum of both young and aged mice. These results suggest that high P diet increased RANKL mRNA expression in the femur and calcium absorption-related gene expression in the duodenum regardless of age. Furthermore, the high P diet-induced increase in PTH secretion might increase the RANKL/OPG mRNA ratio in aged mice.

Age-related bone turnover markers and osteoporotic risk in native Chinese women

BACKGROUND

The rate of bone turnover is closely related to osteoporosis risk. We investigated the correlation between bone turnover markers and BMD at various skeletal sites in healthy native Chinese women, and to study the effect of changes in the levels of bone turnover markers on the risk of osteoporosis.

METHODS

A cross-section study of 891 healthy Chinese women aged 20-80 years was conducted. The levels of serum osteocalcin (OC), bone-specific alkaline phosphatase (BAP), serum 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. BMD at the posteroanterior spine and the hip was measured using DXA.

RESULTS

Pearson's correlation coefficient found significant negative correlation between bone turnover marker and BMD T-score at different skeletal sites (r = -0.08 to -0.52, all P = 0.038-0.000). After adjustments for age and body mass index, the partial correlation coefficients between the OC, BAP, sNTX, sCTX and uCTX, and the T-scores at various skeletal sites were still significant. After adjustment of height and weight, the correlation coefficients between most BTMs and PA lumbar spine BMD were also significant. Multiple linear regression analysis showed that bone turnover markers were negative determinants of T-scores. BAP and OC accounted for 33.1% and 7.8% of the variations in the T-scores of the PA spine, respectively. Serum OC, BAP, uDPD, and sNTX accounted for 0.4-21.9% of the variations in the femoral neck and total hip T-scores. The bone turnover marker levels were grouped as per quartile intervals, and the T-scores, osteoporosis prevalence and risk were found to markedly and increase with increase in bone turnover marker levels.

CONCLUSIONS

This study clarified the relationship between bone turnover markers and osteoporosis risk in native Chinese women. Bone turnover marker levels were found to be important determinants of BMD T-scores. Furthermore, osteoporotic risk significantly increased with increase in the levels of bone turnover markers.

The relationship between bone turnover markers and BMD decreasing rates in Chinese middle-aged women

BACKGROUND

The relationship between bone turnover markers (BTMs) and BMD decreasing rate (BDR) in Chinese women is unclear. Wu investigated the relationship between (BTMs) and BDR at various skeletal sites in Chinese middle-aged women.

METHODS

A cross-section study of 555 healthy Chinese women over 35-60years of age. BMD at posteroanterior spine, the left hip, and the left forearm were measured with a DXA. Levels of serum osteocalcin (OC), bone-specific alkaline phosphatase (BAP), cross-linked N-terminal telopeptides of type I collagen (sNTX) and total urinary deoxypyridinoline (uDPD) were determined.

RESULTS

BDR at various skeletal sites had significant negative correlation with serum OC(r=-0.395 to -0.530), BAP(r=-0.297 to -0.486), and sNTX(r=-0.207 to -0.272). After adjustment of age and weight, serum OC, BAP, and sNTX rather than total uDPD still exhibited significant correlations with BDR. Stepwise regression analyses showed that, serum OC and BAP were the significantly negative determinants of BDR. Between 4.7-27.7% and 1.2-16.1% of the changes in BDR were determined by serum OC and BAP, respectively. However, sNTX and total uDPD had no significant effect on BDR at various skeletal sites.

CONCLUSIONS

This study indicated the correlation between BTMs and early-stage BDR in Chinese middle-aged women and suggested that serum OC and BAP, rather than sNTX and total uDPD, are the key determining factors of early BMD decreases.

Hop rho iso-alpha acids, berberine, vitamin D3 and vitamin K1 favorably impact biomarkers of bone turnover in postmenopausal women in a 14-week trial

Osteoporosis is a major health issue facing postmenopausal women. Increased production of pro-inflammatory cytokines resulting from declining estrogen leads to increased bone resorption. Nutrition can have a positive impact on osteoporosis prevention and amelioration. The objective of this study was to investigate the impact of targeted phytochemicals and nutrients essential for bone health on bone turnover markers in healthy postmenopausal women. In this 14-week, single-blinded, 2-arm placebo-controlled pilot study, all women were instructed to consume a modified Mediterranean-style low-glycemic-load diet and to engage in limited aerobic exercise; 17 randomized to the placebo and 16 to the treatment arm (receiving 200 mg hop rho iso-alpha acids, 100 mg berberine sulfate trihydrate, 500 IU vitamin D(3) and 500 microg vitamin K(1), twice daily). Thirty-two women completed the study. Baseline nutrient intake did not differ between arms. At 14 weeks, the treatment arm exhibited an estimated 31% mean reduction (P = 0.02) in serum osteocalcin (a marker of bone turnover), whereas the placebo arm exhibited a 19% increase (P = 0.03) compared to baseline. Serum 25-hydroxyvitamin D (25(OH)D) increased by 13% (P = 0.24) in the treatment arm and decreased by 25% (P < 0.01) in the placebo arm. The between-arm differences for OC and 25(OH)D were statistically significant. Serum IGF-I was increased in both arms, but the increase was more significant in the treatment arm at 14 weeks (P < 0.01). Treatment with hop rho iso-alpha acids, berberine sulfate trihydrate, vitamin D(3) and vitamin K(1) produced a more favorable bone biomarker profile that supports a healthy bone metabolism.

Vertebral anti-fracture efficacy of strontium ranelate according to pre-treatment bone turnover

Osteoporotic post-menopausal women patients in two randomised trials comparing the anti-fracture efficacy of strontium ranelate with placebo were separated into tertiles according to their baseline levels of biochemical markers of bone formation and resorption. The vertebral anti-fracture efficacy of strontium ranelate was shown to be independent of baseline bone turnover levels.

INTRODUCTION

Bone turnover (BTO) levels vary among women at risk of osteoporotic fracture. Strontium ranelate is an anti-osteoporotic treatment increasing bone formation and reducing bone resorption. It was hypothesised that its anti-fracture efficacy would be independent of baseline BTO levels.

METHODS

Post-menopausal women with osteoporosis from two pooled studies were stratified in tertiles according to baseline levels of two BTO markers: bone-specific alkaline phosphatase (b-ALP, n = 4995) and serum C-telopeptide cross-links (sCTX, n = 4891). Vertebral fracture risk was assessed over 3 years with strontium ranelate 2 g/day or placebo.

RESULTS

In the placebo group, relative risk of vertebral fractures increased with BTO tertiles by 32% and 24% for patients in the highest tertile for b-ALP and CTX, respectively, compared to those in the lowest tertile. In the strontium ranelate group, incidences of vertebral fracture did not differ significantly across BTO tertiles. Significant reductions in vertebral fractures with strontium ranelate were seen in all tertiles of both markers, with relative risk reductions of 31% to 47% relative to placebo. Risk reduction did not differ among tertiles (b-ALP: p = 0.513; sCTX: p = 0.290).

CONCLUSION

The vertebral anti-fracture efficacy of strontium ranelate was independent of baseline BTO levels. Strontium ranelate offers clinical benefits to women across a wide range of metabolic states.

Role of type I collagen C telopeptide, bone-specific alkaline phosphatase and osteocalcin in the assessment of bone status in postmenopausal women

AIM

To investigate the clinical role of the bone turnover markers type I collagen C telopeptide (CTX), osteocalcin (OC) and bone-specific alkaline phosphatase (BAP) in the assessment of bone status in women with postmenopausal osteoporosis.

METHODS

Serum CTX (s-CTX), OC and BAP were measured in 200 healthy menopausal women at their initial visit and were correlated with spine and femur bone mineral density (BMD), determined on dual-energy X-ray absorptiometry. The relationship between biochemical markers of bone turnover and age, age at menopause, body mass index (BMI) and BMD was analyzed using linear correlation. A receiver operating characteristic (ROC) curve was constructed for each serum marker versus both femur and vertebral BMD.

RESULTS

No correlation was found between serum levels of OC and BAP and vertebral or femur BMD. A statistically significant inverse correlation was found between s-CTX and BMD at spine and femur. S-CTX levels were higher in women with osteoporosis than in women with normal or moderately low (osteopenic) values of BMD. The sensitivity and specificity versus spine BMD were 73.9% and 41.6% for s-CTX, 40.4% and 80.6% for BAP, and 68.3% and 39% for OC, respectively. The sensitivity and specificity versus femur BMD were 76.9% and 40.4% for s-CTX, 23.8% and 88.3% for BAP, and 80.4% and 53.3% for OC, respectively.

CONCLUSIONS

Determination of s-CTX, BAP and OC is of limited clinical value in the initial evaluation of bone status in menopausal women.

Soy isoflavone intake inhibits bone resorption and stimulates bone formation in menopausal women: meta-analysis of randomized controlled trials

OBJECTIVE

To clarify the effects of isoflavone intake on bone resorption and bone formation.

METHODS

We identified randomized controlled trials related to urinary deoxypyridinoline (Dpyr, a bone resorption marker) and serum bone-specific alkaline phosphatase (BAP, a bone formation marker) listed on MEDLINE (January 1966-April 2006), the Cochrane Controlled Trials Register, EMBASE (1985-January 2006), Science Citation Index and PUBMED (updated till April 2006).

RESULTS

Nine studies with a total of 432 subjects were selected for meta-analysis. The urinary Dpyr concentration in subjects who consumed isoflavones decreased significantly by -2.08 nmol/mmol (95% confidence interval (CI): -3.82 to -0.34 nmol/mmol) in comparison with that in subjects who did not consume isoflavones. Isoflavone intake vs placebo intake significantly increased serum BAP by 1.48 microg/l (95% CI: 0.22-2.75 mug/l). Decreases in the urinary Dpyr concentration with isoflavone intake of <90 mg/day and with treatment lasting less than 12 weeks were -2.34 nmol/mmol (95% CI: -4.46 to -0.22 nmol/mmol) and -2.03 nmol/mmol (95% CI: -3.20 to -0.85 nmol/mmol), respectively.

CONCLUSIONS

Isoflavone intervention significantly inhibits bone resorption and stimulates bone formation. These favorable effects occur even if <90 mg/day of isoflavones are consumed or the intervention lasts less than 12 weeks.

Reference intervals of serum tartrate-resistant acid phosphatase type 5b activity measured with a novel assay in Japanese subjects

Among the isotypes of serum tartrate-resistant acid phosphatase (TRACP), only type 5b (TRACP-5b) is derived from osteoclasts, and it is necessary to develop an assay specific for this TRACP-5b for evaluation of osteoclastic activity. Recently, a novel assay system for TRACP-5b called the fragments absorbed immunocapture enzymatic assay (FAICEA) has been developed. With two unique monoclonal antibodies, one that is highly specific for TRACP-5b and another which absorbs inactive TRACP-5b fragments that interfere with measuring active TRACP-5b, this assay provides correct measurement of TRACP-5b activity in the serum without interference by the inactive fragments of TRACP-5b and other isotypes of TRACP, especially TRACP-5a. To study the reference data of Japanese subjects, we measured TRACP-5b activity in the serum of 320 men (age, 20-82 years) and 466 women [315 premenopausal (age, 18-55 years) and 151 postmenopausal (age, 45-77 years)] with this novel assay. In men, serum TRACP-5b activity did not vary significantly with age. The postmenopausal women had significantly higher serum TRACP-5b activity than the premenopausal women. The reference intervals (logarithmic mean +/-1.96 SD) for men, premenopausal women, and postmenopausal women were 1.7-5.9 U/l, 1.2-4.4 U/l, and 2.5-7.6 U/l, respectively.

Analysis of Change Patterns of Microcomputed Tomography 3-Dimensional Bone Parameters as a High-Throughput Tool to Evaluate Antiosteoporotic Effects of Agents at an Early Stage of Ovariectomy-Induced Osteoporosis in Mice

OBJECTIVES

The purposes of this study were to develop an osteoporosis model in a short period of 2 weeks after ovariectomy in mice and to investigate whether analysis of microcomputed tomography (muCT) 3-dimensional bone parameters could provide useful information on the mechanism of action of antiosteoporotic agents.

MATERIALS AND METHODS

Mice were ovariectomized (OVX) or sham-operated, and the OVX mice were treated daily with 17beta-estradiol (E2), parathyroid hormone (PTH[1-34]), raloxifene, rolipram, or vehicle for 2 weeks. On day 14 post-OVX, the left femur bones were removed and then the distal metaphyseal bone was analyzed by both muCT and histomorphometry.

RESULTS

The trabecular bone volume, thickness, number, and connectivity significantly decreased and the number of osteoclasts increased in OVX mice. Treatment of OVX animals with each of the 4 antiosteoporotic agents significantly increased the bone volume and improved the bone architecture. However, the improvement of trabecular thickness in the rolipram-treated group and that of cortical thickness in the PTH(1-34)-treated group were the most marked, whereas the improvement of connectivity in the rolipram-treated group was the least among the drug-treated groups. These different improving effects of agents on the bone parameters reflect the differential effects of these agents on bone formation and bone resorption.

CONCLUSIONS

This study demonstrated the feasibility of evaluating the effect of the antiosteoporotic agents within 2 weeks after ovariectomy in mice. The muCT analysis may serve as a valuable tool, specifically in a high-throughput pharmacological screening test, offering useful information regarding the effects of test compounds on both bone resorption and formation.

Age-related changes in bone biochemical markers and their relationship with bone mineral density in normal Chinese women

Measurements of bone biochemical markers are increasingly being used to evaluate the state of bone turnover in the management of bone metabolic diseases, especially osteoporosis. However, changes in the bone turnover rate vary with age. The aim of this study was to establish the laboratory reference range of serum bone-specific alkaline phosphatase (sBAP), serum type I collagen cross-linked C-terminal telopeptide (sCTx), and urine CTx (uCTx), based on values from 665 healthy Chinese women aged 20-80 years. We measured the levels of sBAP, sCTx, serum alkaline phosphatase (sALP), and uCTx and evaluated the age-related changes and their relationship with bone mineral density (BMD) in the anteroposterior (AP) lumbar spine, hip, and left forearm. We found significant correlations between biochemical markers and age, with coefficients of determination (R (2)) of 0.358 for sBAP, 0.126 for sCTx, 0.125 for uCTx, and 0.336 for sALP. The net changes in different biochemical markers were inversely correlated with the rates of BMD loss in the AP lumbar spine. After correction for age, body weight, and height, the levels of the markers had significant negative correlations with the BMD of the AP lumbar spine, femoral neck, and ultradistal forearm. All four biochemical markers had the highest negative correlation with BMD of the AP lumbar spine (partial correlation coefficients of -0.366, -0.296, -0.290, and -0.258 for sBAP, sCTx, uCTx, and sALP, respectively). The mean and SD values of these markers in premenopausal and postmenopausal women with normal BMD values were used as the normal reference ranges. The reference ranges of sBAP, sCTx, and uCTx for pre- vs postmenopausal women were 17.3 +/- 6.23 vs 18.9 +/- 7.52 U/l, 3.18 +/- 1.49 vs 3.23 +/- 1.57 nmol/l, and 15.5 +/- 11.4 vs 16.2 +/- 12.4 nM bone collagen equivalents/mM urinary creatinine, respectively. Levels of the bone formation marker (sBAP) and bone resorption markers (sCTx, uCTx) increased rapidly in women with osteopenia or osteoporosis, indicating that they may be sensitive markers to determine the bone turnover rate in healthy Chinese women.

High-phosphorus diet stimulates receptor activator of nuclear factor-kappaB ligand mRNA expression by increasing parathyroid hormone secretion in rats

The purpose of the present study was to clarify the manner by which the supplementation of high-P diet induces bone loss. Eighteen 4-week-old male Wistar-strain rats were assigned randomly to three groups and fed diets containing three P levels (0.3, 0.9, and 1.5 %) for 21 d. A lower serum Ca concentration was observed in the rats fed on the 1.5 % P diet than in the other two groups. Serum P and parathyroid hormone concentrations and urinary excretion of C-terminal telopeptide of type I collagen were elevated with increasing dietary P levels. Serum osteocalcin concentration was increased in the rats fed on the 1.5 % P diet than in the other two groups. Bone formation rate of the lumbar vertebra was significantly increased in the two high-P groups than in the 0.3 % P group. Osteoclast number was significantly increased with increasing dietary P levels. Bone mineral content and bone mineral density of the femur and lumbar vertebra and ultimate compression load of the lumbar vertebra were decreased with increasing dietary P levels. Additionally, ultimate bending load of the femur was decreased in the rats fed on the 1.5 % P diet than in the other two groups. Receptor activator of NF-kappaB ligand (RANKL) mRNA expression in the femur was significantly higher with increasing dietary P levels. These results suggest that secondary hyperparathyroidism due to a high-P diet leads to bone loss via an increase in bone turnover. Furthermore, an increase in osteoclast number was caused by increased RANKL mRNA expression.

Differential effects of teriparatide and alendronate on bone remodeling in postmenopausal women assessed by histomorphometric parameters

An 18-month randomized double-blind study was conducted in postmenopausal women with osteoporosis to compare the effects of once-daily teriparatide 20 microg with alendronate 10 mg on bone histomorphometry. Biopsies were obtained from 42 patients. Indices of bone formation were significantly higher after 6 or 18 months of teriparatide compared with alendronate treatment.

INTRODUCTION

Alendronate and teriparatide increased BMD, assessed by DXA, by different mechanisms of action, supported by changes in biochemical markers of bone turnover. The purpose of this cross-sectional study was to explore the differential effects of these two osteoporosis treatments at the bone tissue level by examining bone histomorphometric parameters of bone turnover after either 6 or 18 months of treatment.

MATERIALS AND METHODS

Patients were a cohort from a randomized parallel double-blind study conducted to compare the effects of once-daily teriparatide 20 microg and alendronate 10 mg in postmenopausal women with osteoporosis. Transiliac crest bone biopsies were obtained after tetracycline double labeling from 42 patients treated for 6 months (n = 23) or 18 months (n = 14); 5 additional patients were biopsied from contralateral sides at 6 and 18 months. Biopsy specimens adequate for quantitative analysis were analyzed by 2D histomorphometry from 17 patients at 6 months (teriparatide, n = 8; alendronate, n = 9) and 15 patients at 18 months (teriparatide, n = 8; alendronate, n = 7). Data were analyzed by two-sample tests.

RESULTS

Histomorphometric indices of bone formation were significantly and markedly greater in the teriparatide group than in the alendronate group at 6 and 18 months, whereas indices of bone resorption were only significantly greater in the teriparatide group than in the alendronate group at 6 months. Bone formation and activation frequency were significantly lower at 18 months compared with 6 months in the teriparatide group, returning to levels comparable with untreated postmenopausal women. In the teriparatide group, the peak in histomorphometric bone formation indices coincided with peak levels for N-terminal propeptide of type I collagen, a biochemical marker of bone formation. The degree of mineralization was lower at 18 months than at 6 months with treatment in both groups but was not different between groups.

CONCLUSIONS

These results confirm the opposite mechanisms of action of teriparatide and alendronate on bone remodeling and confirm the bone formation effect of teriparatide.

Biochemical markers of bone remodeling

Because of the aging population in most countries, disorders of bone and mineral metabolism are becoming increasingly relevant to everyday clinical practice. Consequently, the interest in, and the need for effective measures to be used in the screening, diagnosis, and follow-up of such pathologies has markedly grown. Together with clinical and imaging techniques, laboratory tests play an important role in the assessment and differential diagnosis of metabolic bone disease.

Biochemical markers to survey bone turnover

Molecular markers of bone turnover have gained increasing relevance in the evaluation of patients with metabolic bone diseases. Their clinical applications include the assessment of future osteoporotic fracture risk, complementation of bone density measurements, diagnosis of certain metabolic osteopathies, therapeutic decision making, and monitoring of therapeutic efficacy and patient compliance. One should be aware, however, that the results from large epidemiologic or clinical trials are sometimes difficult to translate into the everyday clinical situation. The individual patient often has more than one disease that might affect either bone turnover or the handling of the parameters mentioned (or both). Analytic and biologic variability of bone markers can be significant and also needs to be considered when using these indices. In the scientific setting, conventional and new markers of bone turnover can help to elucidate formerly unknown mechanisms and pathways. Because the development of ever more specific and sensitive markers of bone metabolism is progressing rapidly, we are likely to witness new insights into the pathophysiology of bone diseases in the near future.

Isoflavone-rich soy protein isolate attenuates bone loss in the lumbar spine of perimenopausal women

BACKGROUND

No published studies have directly examined the effect of soy protein with isoflavones on bone or bone turnover in perimenopausal women.

OBJECTIVE

Our objective was to determine the effects of 24 wk of consumption of soy protein isolate with isoflavones (80.4 mg/d) in attenuating bone loss during the menopausal transition.

DESIGN

Perimenopausal subjects were randomly assigned, double blind, to treatment: isoflavone-rich soy (SPI+; n = 24), isoflavone-poor soy (SPI-; n = 24), or whey (control; n = 21) protein. At baseline and posttreatment, lumbar spine bone mineral density (BMD) and bone mineral content (BMC) were measured by using dual-energy X-ray absorptiometry. At baseline, midtreatment, and posttreatment, urinary N:-telopeptides and serum bone-specific alkaline phosphatase (BAP) were measured.

RESULTS

The percentage change in lumbar spine BMD and BMC, respectively, did not differ from zero in the SPI+ or SPI- groups, but loss occurred in the control group (-1.28%, P: = 0.0041; -1.73%, P: = 0.0037). By regression analysis, SPI+ treatment had a positive effect on change in BMD (5.6%; P: = 0.023) and BMC (10.1%; P: = 0.0032). Baseline BMD and BMC (P: < or = 0.0001) negatively affected the percentage change in their respective models; baseline body weight (P: = 0.0036) and bone-free lean weight (P: = 0.016) contributed positively to percentage change in BMD and BMC, respectively. Serum BAP posttreatment was negatively related to percentage change in BMD (P: = 0.0016) and BMC (P: = 0.019). Contrast coding using analyses of covariance with BMD or BMC as the outcome showed that isoflavones, not soy protein, exerted the effect.

CONCLUSION

Soy isoflavones attenuated bone loss from the lumbar spine in perimenopausal women.

The predictive value of biochemical markers of bone turnover for bone mineral density in postmenopausal Japanese women

To examine the predictive value of biochemical markers of bone turnover for bone loss pre- and postmenopausally, we measured two markers of bone formation, bone-specific alkaline phosphatase (BALP) and intact osteocalcin (OC); four markers of bone resorption, urinary cross-linked N-telopeptides of type I collagen (NTx), type I collagen C-telopeptide breakdown products (CTx), hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP); serum OC N-terminal (OC-N); and two serum cytokines, soluble interleukin-6 receptor (sIL-6R) and IL-1r antagonist at baseline and 1 year, as well as lumbar spine bone mineral density (BMD) at baseline and 1, 2, 3, 4, and 5 years after trial in 82 premenopausal (44.8 +/- 5.4 years old) and 325 postmenopausal (60.2 +/- 6.1 years old) healthy Japanese women. In premenopausal women, stratification of the baseline value of each biochemical marker into quartiles did not cause any significant difference in the change in BMD. Stratification of the NTx baseline value in postmenopausal women showed significant differences in rate of bone loss to the first year among those subjects with each quartile (Q1 [0.28 +/- 0.28%], Q2 [-0.32 +/- 0.34%], Q3 [-1.50 +/- 0.31%], and Q4 [-2.43 +/- 0.35%]) except for the difference between Q1 and Q2. The predictive value of NTx for BMD was greater in early postmenopausal women within 5 years after menopause than in late postmenopausal women with more than 5 years since menopause (YSM). Quartile analysis of the other biochemical markers and serum cytokines did not show any significant capacity for differentiating between bone loss rates. Moreover, when the changes in the lumbar spine BMD to the second and third years were stratified into quartiles by the baseline NTx, the ratios of bone loss to the second and the third years were significantly higher in those women with higher NTx (Q4; -3.15 +/- 0.56% and -4.06 +/- 0.57%, respectively) than in those with lower NTx (Q1; -0.74 +/- 0.44% and -1.03 +/- 0.51%, respectively). In conclusion, baseline urinary NTx was the most sensitive predictor of bone loss in the lumbar spine after 1, 2, and 3 years. Markers of bone resorption can be used clinically to predict future BMD in postmenopausal women.

The role of bone turnover markers and risk factors in the assessment of osteoporosis and fracture risk

The clinical evaluation of osteoporosis in individual patients involves confirmation of the diagnosis, the investigation of secondary causes of osteoporosis and the evaluation of subsequent fracture risk. Optimum clinical assessment involves bone mineral densitometry with the treatment thresholds modified by clinical risk factors for individual patients. Bone turnover markers and clinical risk factors can be used to identify patients at risk of osteoporotic fracture and those who have secondary osteoporosis. Risk assessment should involve the evaluation of absolute rather than relative risk. Further work is required to improve the integration of clinical risk factors, bone turnover markers and bone densitometry into appropriate models to enable the assessment of the absolute risk of fracture for individual patients.

Urinary galactosyl-hydroxylysine in postmenopausal osteoporotic women: A potential marker of bone fragility

Alterations of the collagen matrix, e.g., increased hydroxylation and glycosylation of lysyl residues in collagen I, were found in human osteoporotic bone, and it was suggested that they could alter the mechanical properties of skeleton. To test this hypothesis, we evaluated the content of galactosyl-hydroxylysine (GHYL) in bone collagen, as assessed by its urinary excretion, and related it to the occurrence of fracture. Two hundred and fifteen unselected postmenopausal women with osteoporosis were divided in two subgroups (comparable for age, age of menopause, bone mineral density, and biochemical parameters of bone turnover) on the basis of the history of fragility fracture; 115 patients had suffered no fracture and 100 patients had suffered one or more fractures 3 or more years before. Four urinary markers of bone turnover (hydroxyproline, cross-linked N-telopeptide, free deoxypyridoline, and GHYL) were evaluated in all patients. There was no difference between the two groups with regard to all the parameters studied except for GHYL, which was significantly higher in the group with a history of fracture (1.35 +/- 0.82 mmol/mol of creatinine [Cr] versus 1.03 +/- <0.48 mmol/mol Cr, p < 0.001); this marker did not correlate with other markers of bone remodeling in the fracture group, indicating a possible defect in bone collagen. In conclusion, provided that increased levels of urinary GHYL do reflect overglycosylation of hydroxylysine in bone collagen, the GHYL may be considered a marker of bone collagen quality. Our results, showing higher urinary GHYL in osteoporosis patients with fracture, seem to confirm this suggestion.

Bone markers in clinical practice

Although biologic indices of bone turnover are widely accepted as research tools in population-based studies, their clinical utility in the management of the individual patient remains controversial. Their main limitation for a routine clinical use is related to an important biologic variability, which means that large variations (ie, in response to therapy) are needed to consider a difference between two measurements as reflecting a significant biologic change. To date, the most valuable bone markers are serum osteocalcin, bone-specific alkaline phosphatase, and the N-terminal propeptide of type 1 procollagen for bone formation and urinary measurements of the phenazopyridine crosslinks and related telopeptides for bone resorption. New serum assays for both C-telopeptide and N-telopeptide of type 1 collagen seem promising but need extensive validation. Although bone markers provide little information in the diagnosis of osteoporosis, strong evidence now shows that they can predict, albeit imperfectly, the rate of bone loss in menopausal women and the response to some antiresorptive therapies. In some populations, increased bone turnover has been shown to be a strong predictor of fracture risk, independently and to the same extent as low bone density. Whether bone markers are used to monitor the efficacy of (or compliance with) a specific treatment or to identify patients at risk for osteoporosis and thus to target preventive therapy, cost-benefit analysis, and evaluation of the potential improvement in patient outcome are clearly needed before these parameters may be universally accepted as tools to optimize patient care.

Fast and slow bone losers. Relevance to the management of osteoporosis

A low bone mineral density (BMD) is presently regarded as the most important risk factor for the development of osteoporosis. BMD is a function of peak bone mass attained during growth and subsequent age-related bone loss. BMD can be measured accurately and precisely, although the rate of bone loss is more difficult to assess. When axial BMD was measured, the rate of bone loss was shown to increase by 2- to 4-fold at the menopause. Although this rate varies markedly between individuals, it is symmetrically distributed, which argues against the existence of a subpopulation of fast bone losers. Levels of biochemical markers of bone turnover (e.g. osteocalcin, bone specific alkaline phosphatase, deoxypyridinoline) also increase markedly at the menopause, and individuals with a high turnover tend to lose bone more rapidly. Moreover, since increased bone resorption also results in qualitative changes regardless of BMD, a high bone turnover constitutes an independent risk factor. Currently, large intraindividual variations (10 to 40%) in levels of biochemical markers and assay errors still limit our ability to correctly classify individual patients as fast or slow bone losers. The routine use of these markers as a screening tool to predict the risk of osteoporosis in individuals is of limited value, although their selective use in therapeutic decision-making is more promising.

Rapid bone loss is associated with increased levels of biochemical markers

We examined associations of biochemical markers of bone turnover with rapid bone loss, as measured by changes in bone mineral density (BMD). To improve the precision of bone loss estimates, calcaneal BMD was measured up to eight times over a long interval (13 years) among postmenopausal women (mean age = 62 years at baseline). Women with fractures during the previous year, and users of corticosteroids, active vitamin D, bisphosphonates or calcitonin were excluded to avoid potential transient effects on marker levels. Among the remaining 354 women, markers were measured for 100 women with the fastest BMD loss (rapid loss group; mean = 2.2%/year) and 100 with the slowest loss (mean = 0.4%/year). Two markers of bone formation, serum bone alkaline phosphatase (Alkphase-B; BAP) and osteocalcin (NovoCalcin; OC), and two markers of bone resorption, urinary creatinine-corrected free deoxypyridinoline (Pyrilinks-D; DPD) and free pyridinolines (Pyrilinks; PYD), were measured. In separate logistic regression models, each of the markers was strongly associated with rapid loss: the odds of rapid loss increased by 1.8 to 2.0 times for each 1.0 standard deviation (SD) increase of the marker. For BAP levels 2 SD above the mean, the probability of rapid bone loss was 80%; in contrast, the probability was only 20% at 2 SD below the mean. The other markers yielded similar results. We conclude that these markers are associated with rapid bone loss; this relationship appears to be continuous, with progressively greater risk of rapid bone loss with increasing levels of biomarkers. Prospective studies that include the entire distribution of bone loss rates are warranted to confirm these findings.