Urinary Excretion Of Pyridinium Crosslinks Research Articles

Short-term Changes in Calcium but not Protein Intake Alter the Rate of Bone Resorption in Healthy Subjects as Assessed by Urinary Pyridinium Cross-Link Excretion

This study was conducted to determine whether the markers of bone resorption, pyridinium cross-links of collagen, are sensitive to changes in dietary protein and calcium intake. Fifteen young healthy subjects (7 males and 8 females) participated in three 5-d diet periods. Dietary intake during each dietary period consisted of: 1) low nitrogen and low calcium [0.49 ± 0.11 g protein/ (kg·d), 429 ± 190 mg calcium/d]; 2) low nitrogen and high calcium [0.44 ± 0.08 g protein/ (kg·d), 1643 ± 171 mg calcium/d]; and 3) a high nitrogen and high calcium [2.71 ± 0.75 g protein/(kg·d), 1589 ± 633 mg calcium/d] diet, and this was compared with subjects' baseline dietary intake [0.99 ± 0.51 g protein/(kg·d), 589 ± 152 mg calcium/d]. The order of these diets was randomly assigned. Twenty-four-hour and 3-h urine samples were collected before and during each dietary period and were analyzed for pyridinium cross-links (pyridinoline, deoxypyridinoline), nitrogen and creatinine. The rate of pyridinium cross-link excretion did not vary with protein intake but was ∼33% lower (P < 0.01) during periods of high compared with low calcium intake. These data indicate that a short-term increase in calcium intake is accompanied by a reduced rate of bone resorption and that this effect is independent of dietary protein intake.

β-Cryptoxanthin rich paprika extract prevents ovariectomy induced bone loss in Wistar rats

Recent studies show that high intake of carotenoids is helpful in preventing bone loss in post-menopausal women. Carotenoids like β-cryptoxanthin increases calcium and phosphorus deposition in cultured osteoblasts. β-Cryptoxanthin is also reported to have anabolic property in cultured osteoblast cells. It can also inhibit bone resorption process. Paprika and its dietary products are rich in carotenoids like β-cryptoxanthin. Carotenoids from the paprika oleoresin are also reported to have very good bioavailability in humans. The present study was carried out to investigate the effect of β-cryptoxanthin rich paprika extract on animal model of ovariectomy induced bone loss. Treatment with the test drug was given for 6 weeks. The β-cryptoxanthin rich paprika extract significantly reduced urinary excretion of pyridinium crosslinks, indicating its probable anti-resorptive property. The mechanical strength and density of cancellous bones are significantly improved. Thus the paprika extract may have potential role as a sustainable nutritional approach to improving bone health in post-menopausal condition.

Lower serum 25-hydroxyvitamin D is associated with increased bone resorption markers and lower bone density at the proximal femur in normal females: a population-based study.

Subclinical vitamin D deficiency is considered to be a risk factor for osteoporosis. Therefore, we studied vitamin D status and bone mineral density (BMD) in an age- and sex-stratified population based sample (209 males and 206 females aged between 50 and 80 years). In addition, urinary excretion of pyridinium crosslinks of collagen was determined in order to monitor bone resorption. We found a seasonal variation of serum 25-hydroxyvitamin D (25(OH)D) levels with higher values detected in the summer (27 +/ - 10 ng/ml) and lower values measured in the winter (17 +/- 9 ng/ml). Further analyses were performed separately for winter and summer, respectively. We also excluded subjects taking osteotropic medication. In men, we found no significant relationship between vitamin D status and bone density or pyridinium crosslinks. In women, we found significant positive correlations between 25(OH)D and proximal femur BMD in winter (r = 0.21, p < 0.05) and in summer (r = 0.36, p < 0.01). The association between 25(OH)D and proximal femur BMD persisted after correction for age and body mass index. Serum 25(OH)D and urinary pyridinium crosslinks were inversely correlated in females in winter (r = -0.24, p < 0.02) and in summer (r = -0.32, p < 0.02). Our data support the hypothesis that already moderately low serum levels of 25(OH)D within the "normal" range lead to osteopenia via increased bone resorption.

Evidence of Increased Bone Resorption in Neurofibromatosis Type 1 Using Urinary Pyridinium Crosslink Analysis

Although neurofibromatosis type 1 (NF1) is a neurocutaneous disorder, skeletal abnormalities such as long-bone dysplasia, scoliosis, sphenoid wing dysplasia, and osteopenia are observed. To investigate the role of bone resorption as a mechanism for the bony abnormalities, we selected urinary pyridinium crosslinks (collagen degradation products excreted in urine) as a measure of bone resorption in NF1. Bone resorption was evaluated by quantitative assessment of the urinary excretion of pyridinium crosslinks [pyridinoline (Pyd) and deoxypyridinoline (Dpd)]. Total (free plus peptide-bound) pyridinium crosslinks from the first morning urines from 59 NF1 children (ages 5-19) were extracted and analyzed (17 children with a localized skeletal dysplasia, and 42 without). The data were compared with a healthy reference population without NF1 (n = 99). Multivariate analyses, controlling for age showed statistically significant increases for Dpd (p < 0.001) and the Dpd/Pyd ratio (p < 0.001) in NF1 individuals with and without a skeletal dysplasia. NF1 children have an increase in the urinary excretion of pyridinium crosslinks, reflecting increased bone resorption. The effects of NF1 haploinsufficiency likely contribute to abnormal bone remodeling, either directly or indirectly by aberrant Ras signaling, potentially predisposing NF1 individuals to localized skeletal defects.

TGF-beta 1 and urinary excretion of pyridinium crosslinks: two often overlooked risk factors for assessing risk of progression in patients with monoclonal gammopathy of undetermined significance

The article by Sackmann et al is highly interesting and provides an excellent analysis of the factors that predict the risk of progression in patients with Monoclonal Gammopathy of Undetermined Significance (MGUS).[1][1] Two other parameters that may also aid in assessing risk progression and are

ELEVATED DEOXYPYRIDINOLINE/PYRIDINOLINE RATIOS IN CHILDREN WITH NEUROFIBROMATOSIS TYPE 1 SUGGEST ABNORMALITY OF BONE REMODELING RATHER THAN COLLAGEN BREAKDOWN FROM OTHER TISSUES.

Objective Neurofibromatosis type 1 (NF1), although classically thought of as a neurocutaneous disorder, is associated with localized skeletal abnormalities, including long-bone dysplasia, scoliosis, sphenoid wing dysplasia, and bone cysts. Our preliminary studies have documented decreased bone mineral density in children with NF1. Pyridinium cross-links [pyridinoline (Pyd) and deoxypyridinoline (Dpd)] are hydroxylysine-derived cross-links of mature collagen excreted in urine as a result of collagen degradation. Both Pyd and Dpd are found in bone and cartilage, but Dpd is most abundant in bone and reflects more the status of bone. To draw inferences of bone resorption, studies were designed to assess the Dpd/Pyd ratio in individuals with NF1 compared with individuals without NF1. Methods The total (free plus peptide-bound) pyridinium cross-links from two consecutive first morning urines from 60 NF1 children (ages 5-19) were extracted after acid hydrolysis and analyzed by high-performance liquid chromatography. Data were compared with 99 healthy controls without NF1. Regression analysis controlling for age and skeletal dysplasia status (defined as scoliosis, long-bone dysplasia, and/or sphenoid wing dysplasia) was used. Results Statistically significant increases of Pyd (p = .019) and Dpd (p Conclusions The elevated urinary excretion of pyridinium cross-links, both Dpd and Pyd, reflects increased collagen degradation in children with NF1. In addition, the elevated Dpd/Pyd ratio shows that the increased collagen breakdown products are predominantly due to abnormal resorption of bone and not from collagen breakdown of other tissues. The linear regression analysis adjusting for skeletal dysplasia status suggests that NF1 haploinsufficiency contributes to increased bone resorption and a generalized abnormality of bone remodeling predisposing individuals with NF1 to localized skeletal defects.

Chelation Therapy and Bone Metabolism Markers in Thalassemia Major

The aim of our study was to investigate the effects of subcutaneous desferrioxamine (DFX) and oral deferiprone (L1) therapy on bone metabolism markers in patients with thalassemia major. We studied 17 patients with thalassemia receiving long-term treatment with desferrioxamine, 20 patients receiving long-term treatment with deferiprone, and 15 healthy age-matched controls. The following investigations were performed: a) intact parathyroid hormone (PTH), 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH)2D] as endocrine parameters; b) alkaline phosphatase (ALP), bone alkaline phosphatase (BALP), osteocalcin (OC); c) bone resorption biochemical markers in serum and urine pyridinium crosslinks: hydroxylysyl-pyridinoline (HP) and lysyl-pyridinoline (LP); d) serum levels of cytokines and growth factors: transforming growth factor-beta1 (TGFbeta1), insulin-like growth factor-I (IGF-I), interleukin-1beta (IL-1beta), interleukin-6 (IL-6), tumor necrosis factor-a (TNFalpha); e) serum levels of IGF binding protein-3 (IGFBP-3). No significant differences among all studied variables were found in patients with thalassemia treated with desferrioxamine or deferiprone. In contrast, significant differences were found between patients with thalassemia and the control group: intact PTH was significantly lower in patients with thalassemia than in the controls (p < 0.0005), and a significant increase in ALP and BALP (p < 0.0005), but not in OC, was found in the patient group. With regard to bone resorption and remodeling markers, the urinary excretion of pyridinium crosslinks was higher in patients with thalassemia for HP fraction (p < 0.0005) and LP fraction (p = 0.002), as well as TGFbeta (p = 0.001). In contrast, IGF-I and IGFBP-3 were reduced when compared with controls. In conclusion, the study of bone metabolism markers in adult patients with thalassemia reveals a complex behavior with an increase in bone resorption indexes. Bone formation did not appear to be impaired. In particular, TGFbeta1 was higher in patients with thalassemia receiving L1 treatment.

Urinary excretion of pyridinium cross-links and serum osteocalcin levels in patients with primary high-grade osteosarcoma.

Osteosarcoma is the most frequent primary high grade bone tumor, usually occurring in adolescents and children. The aim of the present study was to investigate parameters of bone turnover as urinary excretion of pyridinoline (Pyr), and deoxypyridinoline (D-Pyr), serum osteocalcin (OC), and total alkaline phosphatase (AP) in patients with osteosarcoma. Thirty-five patients aged 7-22 (median age 14) with primary high-grade osteosarcoma of the extremity entered the study. A control population of age- and sex-matched healthy individuals was studied. Urinary excretion of Pyr, D-Pyr was measured on fasting urine specimens, corrected for creatine excretion (Ucr), and expressed as pM/microM UCr. At the same time as urine collection, blood samples were taken for measurement of AP and OC. In patients with osteosarcoma the urinary excretion of D-Pyr (74.5 +/- 41) was significantly higher (P = 0.005) than in controls (38.2 +/- 22.5). The serum level of OC was significantly lower (P < 0.001) in patients with osteosarcoma than in controls. Moreover, significantly (P = 0.03) higher excretion of D-Pyr (85.3 +/- 43) was found in patients who relapsed after surgical removal of the tumor and chemotherapeutic treatment compared with those (58.1 +/- 22) who remained continuously free of disease. The present study showed significant abnormalities of urinary excretion of pyridinium crosslinks and serum OC level in patients with osteosarcoma. The relation between urinary excretion of D-Pyr and biological tumor aggressiveness observed in the present study requires further investigation.

Bone resorption in anorexia nervosa and rehabilitated patients.

To assess the impact of anorexia nervosa and that of nutritional rehabilitation on bone resorption. Cross-sectional, observational study. Rome, Italy Twenty-eight female patients affected by anorexia nervosa (AN, BMI<or=17.0 kg/m(2)), 18 females rehabilitated from anorexia nervosa and weight-stable for at least 6 months (RE, BMI >or=18.5 kg/m(2)) and 34 age- and sex-matched healthy controls (CO, BMI >or=18.5 kg/m(2)). Among AN patients, 16 were affected by the 'restrictive' (ANr) and 12 by the 'purging' type (ANp) of anorexia nervosa. Body weight, height and skeletal diameters were measured on each individual. The skeletal mass (SKM) was predicted from the skeletal diameters of the elbow, wrist, knee and ankle, using the equation of Martin. Twenty-four-hour urinary excretion of pyridinium crosslinks of collagen (pyridinoline (Pyd) and deoxypyridinoline (Dpd)) and creatinine was assessed by reversed-phase HPLC with fluorimetric detection after solid-phase extraction and by the Jaffé-method with deproteinization, respectively. Twenty-four-hour urinary output of Pyd and Dpd was not significantly different between AN and CO when expressed in absolute values, but AN showed higher bone resorption than CO when Pyd and Dpd excretion was adjusted by either creatinine (P<0.0000) or the SKM (P<0.05). Within the AN group, urinary excretion of both cross-links was significantly and consistently higher in ANp compared with ANr (P<0.05). However, these differences disappeared when crosslink output was adjusted either by urinary creatinine or SKM. RE subjects showed no differences in bone resorption with the AN group despite weight gain, being crosslink excretion consistently elevated compared to controls (Pyd: P<0.01 by creatinine and P<0.05 by SKM; Dpd: P<0.01 by creatinine and P<0.05 by SKM). Bone resorption is elevated in anorexia nervosa and different strategies for low-weight maintenance do not seem to have a differential impact. Increased bone resorption persists in subjects with past diagnosis of anorexia nervosa despite rehabilitation lasting more than 6 months. This finding indicates that bone mass and turnover should be monitored in anorexia nervosa patients and ex-patients well beyond recovery of normal body mass. Further investigation is warranted to examine the long-term effect of such prolonged increase in bone turnover at a young age.

Urinary excretion of pyridinium crosslinks in short children treated with growth hormone.

The aim of this study was to evaluate the effect of growth hormone (GH) treatment on bone resorption in children with GH deficiency and those with idiopathic short stature. The study population included seven children with subnormal spontaneous GH secretion and 13 children with idiopathic short stature, all of them pre-pubertal. Anthropometric measurements, free, protein-bound and total urinary pyridinoline (Pyd) and deoxypyridinoline (Dpd), serum GH, and serum immunoreactive PTH were measured at baseline and months 1, 3, 6 and 12 of GH treatment. The urinary excretion of total Pyd and Dpd, standardized by the cube of height (m3) in overnight, 24-hour urine collections was not different from age-matched healthy controls at baseline in either group of patients. During treatment with human recombinant GH, both pyridinium crosslinks increased above normal values, reaching a peak after one month in children with GH deficiency and later (after 3-6 months) in children with short stature. Free and total crosslink forms were correlated, and GH treatment did not affect the proportion of free to bound crosslinks. Serum concentrations of iPTH showed a moderate but not statistically significant increase. This study provides no evidence of reduced bone resorption in untreated GH deficiency or in idiopathic short stature. GH treatment induced a marked, but temporary, increase of bone resorption in both groups of patients.

INCIDENCE OF SKELETAL COMPLICATIONS IN PATIENTS WITH BONE METASTATIC PROSTATE CANCER AND HORMONE REFRACTORY DISEASE: PREDICTIVE ROLE OF BONE RESORPTION AND FORMATION MARKERS EVALUATED AT BASELINE

We evaluated the incidence of skeletal complications in patients with bone metastatic prostate cancer and hormone refractory disease. We also assessed the predictive role of bone turnover markers determined at baseline. A total of 112 patients were consecutively enrolled in our study from July 1990 to July 1998 and followed until death or the last followup. Bone pain, disease extent in bone, serum prostate specific antigen, hemoglobin, and a panel of bone formation and resorption markers were assessed at baseline before any second line treatment. Skeletal complications in 34 patients (30.3%, estimated yearly incidence 12.3%) involved vertebral deformity or collapse requiring spinal orthosis in 20 (17.9%), spinal cord compression in 7 (6.2%), pathological bone fracture in 10 (8.9%), symptomatic hypercalcemia in 1 (0.9%) and symptomatic hypocalcemia in 1 (0.9%). Median time to the evidence of the initial skeletal complication was 9.5 months. These adverse events did not influence overall survival. At baseline patients with eventual skeletal complications had greater bone pain (p = 0.02), a heavier tumor load in bone (p = 0.005), lower performance status (p = 0.05), and higher serum alkaline phosphatase (p <0.02) and urinary deoxypyridoline (p <0.05) than their counterparts. Multivariate analysis revealed that only urinary deoxypyridinoline was independently associated with the onset of these events (p <0.02). The scatterplot of urinary deoxypyridinoline values in patients with and without skeletal complications enabled us to detect a cutoff of 38 pM./mM. for predicting 51% of skeletal events with only an 8% false-positive rate. Skeletal complications are common in patients with prostate cancer and hormone refractory disease. Bone loss is the major cause of onset. Baseline deoxypyridinoline at the cutoff point noted had moderate sensitivity but high specificity for predicting these adverse skeletal events.

Effect of hormone replacement therapy on the bone mass and urinary excretion of pyridinium cross-links.

The menopause accelerates bone loss and is associated with an increased bone turnover. Bone formation may be evaluated by several biochemical markers. However, the establishment of an accurate marker for bone resorption has been more difficult to achieve. To study the effect of hormone replacement therapy (HRT) on bone mass and on the markers of bone resorption: urinary excretion of pyridinoline and deoxypyridinoline. Cohort correlational study. Academic referral center. 53 post-menopausal women, aged 48-58 years. Urinary pyr and d-pyr were measured in fasting urine samples by spectrofluorometry after high performance liquid chromatography and corrected for creatinine excretion measured before treatment and after 1, 2, 4 and 12 months. Bone mineral density (BMD) was measured by dual energy X-ray absorptiometry (DEXA) before treatment and after 12 months of HRT. The BMD after HRT was about 4.7% (P < 0.0004); 2% (P < 0.002); and 3% (P < 0. 01) higher than the basal values in lumbar spine, neck and trochanter respectively. There were no significant correlations between pyridinium cross-links and age, weight, menopause duration and BMD. The decrease in pyr and d-pyr was progressive after HRT, reaching 28.9% (P < 0.0002), and 42% (P < 0.0002) respectively after 1 year. Urinary pyridinoline and deoxypyridinoline excretion decreases early in hormone replacement therapy, reflecting a decrease in the bone resorption rate, and no correlation was observed with the bone mass evaluated by densitometry.

Urinary excretion of pyridinium crosslinks in healthy 4-10 year olds.

Urinary pyridinoline and deoxypyridinoline, pyridinium crosslinks released during breakdown of mature collagen, might serve as useful markers of bone resorption. Before their role can be identified, reference values must be established. In this study, free pyridinoline (f-Pyr), free deoxypyridinoline (f-DPyr), and creatinine (Cr) were measured in first morning void urine samples from 250 girls and 265 boys between the ages of 4 and 10 years. Overall, there was a decrease in f-Pyr:Cr and f-DPyr:Cr ratios with increasing age in both sexes, but there was a wide range of values for individuals of similar ages. Further studies are required to assess whether urinary pyridinium crosslink excretion is sufficiently deranged in conditions affecting bone metabolism for the measurement of these compounds to be of clinical value.

Increased Urinary Excretion of Pyridinium Crosslinks in Streptozotocin-induced Diabetic Rats

Increased Urinary Excretion of Pyridinium Crosslinks in Streptozotocin-induced Diabetic Rats

Endothelin subtype A receptor antagonist induces osteopenia in growing rats

Previous studies suggested that endothelin (ET) peptides are involved in bone metabolism. We examined the effects of long-term blockade of the ET A receptor, a receptor subtype primarily involved in the anabolic actions of ET, on bone mineral status in growing rats. Eight-week-old rats injected intraperitoneally with FR139317 50 mg/kg body weight, a specific ET A receptor antagonist, for 2 or 4 weeks were compared with control rats injected with vehicle only. Treatment with FR139317 caused a significant decrease in bone mass in the lumbar spine as determined by dual-energy x-ray absorptiometry (DXA). FR139317-induced osteopenia was associated with a significant decrease in the serum osteocalcin concentration but no change in the urinary excretion of pyridinium cross-links of collagen. Our findings indicate that long-term blockade of the ET A receptor reduces bone formation and induces osteopenia in growing rats. Our results suggest that ET produced by vascular endothelial cells plays an important role in bone growth and metabolism in vivo.

A 12-Month Prospective Study of the Relationship Between Stress Fractures and Bone Turnover in Athletes

Bone remodeling may be involved in the pathogenesis of stress fractures in athletes. We conducted a 12-month prospective study to evaluate bone turnover in 46 female and 49 male track and field athletes aged 17-26 years (mean age 20.3; SD 2.0) 20 of whom developed a stress fracture. Baseline levels of bone turnover were evaluated in all athletes and monthly bone turnover levels were evaluated in a subset consisting of the 20 athletes who sustained a stress fracture and a matched comparison group who did not sustain a stress fracture. Bone formation was assessed using serum osteocalcin (OC) measured by human immunoradiometric assay and bone resorption by urinary excretion of pyridinium cross-links (Pyr and D-Pyr); high performance liquid chromatography and N-telopeptides of type 1 collagen (NTx) using ELISA assay. Athletes who developed stress fractures had similar baseline levels of bone turnover compared with their nonstress fracture counterparts (P > 0.10). Results of serial measurements showed no differences in average levels of Pyr, D-Pyr, or OC in those who developed stress fractures (P = 0.10) compared with the control group. In the athletes with stress fractures, there was also no difference in bone turnover levels prior to or following the onset of bony pain. Our results show that single and multiple measurements of bone turnover are not clinically useful in predicting the likelihood of stress fractures in athletes. Furthermore, there were no consistent temporal changes in bone turnover associated with stress fracture development. However, our results do not negate the possible pathogenetic role of local changes in bone remodeling at stress fracture sites, given the high biological variability of bone turnover markers and the fact that levels of bone turnover reflect the integration of all bone remodeling throughout the skeleton.

Urinary excretion of pyridinium crosslinks and N -terminal crosslinked peptide in preterm and term infants

Urinary excretion of pyridinium crosslinks and N -terminal crosslinked peptide in preterm and term infants

Monitoring of multiple myeloma patients by simultaneously measuring marker substances of bone resorption and formation

Fifteen patients (13 males and two females; mean age, 63 years; age range, 46–84 years) with multiple myeloma were studied prospectively (range of follow-up period, 2–6 months) to elucidate the diagnostic validity of biochemical markers of bone formation (bone alkaline phosphatase and the C-terminal propeptide of type I procollagen) and bone resorption (urinary excretion of pyridinium cross-links) for monitoring these patients. Eleven of 15 patients received melphalan i.v. and prednisone p.o. every 4 weeks. All patients were given pamidronate i.v. for inhibition of bone resorption. The mean values of the urinary excretion of pyridinium cross-links were significantly higher in the patients fulfilling the criteria of `progression' or `relapse' than in those showing `response' and those in the `plateau phase' ( P<0.05). In contrast, neither bone alkaline phosphatase nor C-terminal propeptide serum values differed significantly between these two groups ( P>0.05). The concentrations of both bone formation markers were significantly lower in the patients than in the samples obtained from apparently healthy persons ( P<0.001). There was a significant inverse correlation between the number of pamidronate courses and the serum concentrations of bone alkaline phosphatase ( P<0.05). A lack of correlation was observed between the urinary excretion of pyridinium cross-links and all other laboratory parameters measured (serum concentrations of total protein, calcium, creatinine and (β 2-microglobulin). In conclusion, the urinary excretion of pyridinium cross-links might be a useful parameter for monitoring multiple myeloma patients. Decreased values of bone formation markers may be due to a suppressive effect of the bisphosphonate agents administered or reflect the severity of osteolytic lesions which have been described as being associated with unbalanced bone remodelling.

Inter and intra-individual variations in urinary excretion of pyridinium crosslinks of collagen in healthy young adults

To investigate the inter- and intra-individual variation in the excretion of pyridinium crosslinks of collagen in first morning void urine samples in healthy young adults. An observational study in which urinary pyridinium crosslinks of collagen were measured in fasting first void urine samples over five consecutive days. The study was conducted in the Department of Nutrition, University College, Cork, Ireland. A total of 17 healthy young adults (11 females and 6 males) aged 22-26 y were recruited from University College, Cork. The subjects were without any history of bone or articular disease, and with no intake of medicine that could affect bone or cartilage metabolism. There were large intra-individual variations in the excretion of both pyridinoline (Pyr) and deoxypyridinoline (Dpyr) in first morning void urine samples and the ratios of intra- to inter-individual variation were high. In comparison, inter-individual variation in excretion of crosslinks was relatively low. No significant day-to-day variation was observed either in Pyr or Dpyr excretion when either five, four or three consecutive days or four or three non-consecutive days of urine sampling were used. However, there were significant differences between any two consecutive or non-consecutive days in both Pyr and Dpyr excretion. The relatively large day-to-day variation in urinary excretion of the pyridinium crosslinks emphasises the need to use multiple samples to characterise the crosslink excretion of an individual. The present study demonstrates that urine sampling for these crosslinks necessitates at least a 3 d collection to ensure that day-to-day effects are not a significant source of variation included in the data analysis.

Clinical application of immunoassay for urinary total excretion of deoxypyridinoline in patients with osteoporosis

Urinary excretion of pyridinium cross-links is one of the biochemical markers for bone resorption in metabolic bone diseases. Efficacy of immunoassay for deoxypyridinoline (D-pyr) for monitoring effects of antiresorptive therapy was evaluated in 44 women with osteoporosis, including 4 patients with asymptomatic primary hyperparathyroidism. Urinary free forms and protein-bound (conjugated) forms of D-pyr were measured totally by a modified enzyme-liked immunoabsorbent assay (ELISA; PYRILINKS-DTM, Metra Biosystem, Mountain View, CA, USA), which required prehydrolysis of urine samples and adequate acidity adjusted with alkali. There was a close relationship between total excretion of D-pyr measured by reverse-phase high performance liquid chromatography (HPLC) and that measured by ELISA. In 27 patients, the percent change of urinary D-pyr by ELISA following hormone replacement therapy (HRT) was similar to that of urinary total forms of D-pyr using HPLC at the end of the first third, and sixth month. In 8 patients whose series of urine samples were corrected following HRT, the percent change of urinary total excretion of D-pyr by ELISA at the end of the third month was approximately −40%, significantly greater than that of excretion of free forms of D-pyr measured by ELISA (−30%;P<.01). In 16 patients, total urinary D-pyr excretion measured by both methods of HPLC and ELISA decreased by approximately 12% within 4h after a single administration of 20 IU of salmon calcitonin. There were significant differences between percent change of urinary total excretion and that of free forms of D-pyr measured by ELISA (P<.05). We conclude that short-term and subtle change of bone resorption following a single injection of salmon calcitonin, as well as long-term effects of HRT, can be detected by measuring total D-pyr excretion in urine irrespective of assays utilized. A modified assay using ELISA for urinary total D-pyr with an easy procedure provides an informative and cost-beneficial tool in monitoring bone resorption in patients with osteoporosis.