Changes with age in the urinary excretion of lysyl- and hydroxylysylpyridinoline, two new markers of bone collagen turnover

Effects of odanacatib on bone-turnover markers in osteoporotic postmenopausal women: a post hoc analysis of the LOFT study

This post hoc analysis and modeling study examined the mechanism of action of odanacatib using a statistical model to explain sCTx response in ODN-treated patients as a function of other bone-turnover biomarkers that, with other observed biomarker changes, showed that odanacatib persistently inhibited osteoclastic bone removal activity without preventing osteoclastogenesis.

INTRODUCTION

Odanacatib (ODN) is an oral selective cathepsin K (CatK) inhibitor, previously in development for osteoporosis treatment. A post hoc analysis examined ODN's mechanism of action on bone-turnover biomarkers.

METHODS

A subset of patients who completed 60 months' treatment in the Long-Term Odanacatib Fracture Trial (LOFT; NCT00529373) (N = 112 [57 ODN, 55 placebo]) were evaluated. Serum (s) and urine (u) samples were assayed at baseline and months 6-60 for 10 known bone-remodeling biomarkers: sCTx, uαα- and uββCTx/Cr, uNTx/Cr, sNTx, uDPD/Cr, sICTP, sTRAP5b, sPINP, and sBSAP. Because the CrossLaps® CTx assay identifies the CTx peptide as well as larger molecular weight CTx-containing peptides, including ICTP, a best-fit model was developed to explain the transient sCTx reduction in ODN-treated patients.

RESULTS

ODN persistently reduced the bone-resorption markers sNTx, uNTx/Cr, uαα- and uββCTx/Cr, and uDPD/Cr, and gradually increased the target-engagement marker sICTP and osteoclast number (sTRAP5b), versus placebo from baseline to month 60. sCTx was transiently reduced with ODN within 12 months, returning to baseline by month 48. Modeling suggested that sCTx changes in the ODN group were primarily due to increased accumulation of larger CTx species, including sICTP. The bone-formation markers sPINP and sBSAP showed partial reductions, versus placebo, in the first 6 months but approached baseline by months 48-60.

CONCLUSION

Observed changes in bone-turnover biomarkers support the persistent efficacy of ODN in direct inhibition of osteoclastic bone-resorption activity, without inhibition of osteoclastogenesis. Long-term evaluation also underscores the unique mechanism of ODN on osteoclastic collagen processing and subsequently osteoblastic bone formation.

TRIAL REGISTRATION

NCT00529373.

Bone biochemical markers for assessment of bone responses to differentiated phosphorus supply in growing-finishing pigs

Phosphorus (P) is essential for building and maintaining a healthy and strong skeleton. Moreover, dietary P supply may play a role for bone turnover, and the excretion of bone turnover metabolites may be useful as markers for sufficient dietary P supply. The objective was to study the long-term effects of low, medium, and high dietary P supply on bone metabolism in terms of serum concentration and urinary excretion of bone turnover components and metabolites in healthy growing-finishing pigs compared with bone mineral content (BMC) and bone mineral density (BMD) of humerus and femur. Pigs were fed diets containing low [LP; 4.1 g/kg dry matter (DM)], medium (MP; 6.2 g/kg DM), or high dietary P (HP; 8.9 g/kg DM) from 39.7 kg body weight (BW) until slaughter at 110 kg BW. Urine and blood were collected at 40, 70, and 110 kg BW while bones were collected at slaughter. Serum was analyzed for osteocalcin (OC), bone alkaline phosphatase (BAP), and C-terminal telopeptides of type I collagen (CTX-I), whereas urine was analyzed for pyridinoline (PYD), deoxypyridinoline (DPD), CTX-I, hydroxylysine (HYL), galactosyl-hydroxylysine (GAL-HYL), glycosyl-galactosyl-hydroxylysine (GLC-GAL-HYL), and hydroxyproline (HYP). Humerus and femur were analyzed for BMC and BMD. The LP diet caused reduced OC and increased BAP and CTX-I concentrations in serum. Furthermore, BAP was increased in response to the HP diet. Urine metabolites of bone resorption were all increased in pigs fed the LP diet, but only a few responses were obtained in response to the HP diet. Furthermore, age-related decreases were identified for BAP, HYL, GAL-HYL, and GLC-GAL-HYL. Bone mineral content and BMD were markedly lowered in pigs fed the LP diet but were not affected in pigs fed the HP diet. In conclusion, OC, BAP, and CTX-I in serum have proved useful for P adequacy in growing-finishing pigs. In addition, urine bone resorption metabolites have also proved useful for P adequacy and analysis of PYD, DPD, and CTX-I was considered to be the most relevant markers due to their specificity for bone and their negative correlation with BMD, BMC, ash, calcium (Ca), and P contents. Finally, DPD may be the preferred marker in long-term P feeding assessments.

Combined Effects of Eurycoma longifolia and Testosterone on Androgen-Deficient Osteoporosis in a Male Rat Model

Androgen-deficient osteoporosis in men is treated with testosterone therapy, which is associated with side effects. Eurycoma longifolia (EL) is known to possess androgenic properties and has been reported to protect bone from androgen-deficient osteoporosis in experimental animal models. The present study aimed to determine the effectiveness of combination therapy of EL and testosterone (T) in treating androgen-deficient osteoporosis. Forty male Sprague-Dawley rats were divided into: sham-operated (SHAM), orchidectomized-control (ORX), orchidectomized with testosterone (ORX + T), orchidectomized with EL (ORX + EL), and orchidectomized with combined T and EL therapy (ORX + T + EL). EL was administered via oral gavages daily at the dose of 15 mg/kg. T was injected intramuscularly at 8 mg/kg and 4 mg/kg for the ORX + T and ORX + T + EL groups, respectively. Following 6 weeks of treatment, the osteocalcin levels of ORX + T and ORX + T + EL groups were significantly lower than the SHAM group (P < 0.05). The posttreatment CTX levels of ORX + T and ORX + T + EL groups were significantly lower than their pretreatment levels (P < 0.05). Biomechanically, the strain parameter of the ORX + T + EL group was significantly higher than the ORX group (P < 0.05). Thus, the combination therapy of EL and low-dose T has potential for treatment of androgen-deficient osteoporosis. The lower T dose is beneficial in reducing the sideeffects of testosterone therapy.

Safety, efficacy and physiological actions of a lysine-free, arginine-rich formula to treat glutaryl-CoA dehydrogenase deficiency: focus on cerebral amino acid influx

Striatal degeneration from glutaryl-CoA dehydrogenase deficiency (glutaric aciduria type 1, GA1) is associated with cerebral formation and entrapment of glutaryl-CoA and its derivatives that depend on cerebral lysine influx. In 2006 we designed a lysine-free study formula enriched with arginine to selectively block lysine transport across cerebral endothelia and thereby limit glutaryl-CoA production by brain. Between 2006 and present, we treated twelve consecutive children with study formula (LYSx group) while holding all other treatment practices constant. Clinical and biochemical outcomes were compared to 25 GA1 patients (PROx group) treated between 1995 and 2005 with natural protein restriction (dietary lysine/arginine ratio of 1.7±0.3 mg:mg). We used published kinetic parameters of the y+and LAT1 blood-brain barrier transporters to model the influx of amino acids into the brain. Arginine fortification to achieve a mean dietary lysine/arginine ratio of 0.7±0.2 mg:mg was neuroprotective. All 12 LYSx patients are physically and neurologically healthy after 28 aggregate patient-years of follow up (current ages 28±21 months) and there were no adverse events related to formula use. This represents a 36% reduction of neurological risk (95% confidence interval 14-52%, p=0.018) that we can directly attribute to altered amino acid intake. During the first year of life, 20% lower lysine intake and two-fold higher arginine intake by LYSx patients were associated with 50% lower plasma lysine, 3-fold lower plasma lysine/arginine concentration ratio, 42% lower mean calculated cerebral lysine influx, 54% higher calculated cerebral arginine influx, 15-26% higher calculated cerebral influx of several anaplerotic precursors (isoleucine, threonine, methionine, and leucine), 50% less 3-hydroxyglutarate excretion, and a 3-fold lower hospitalization rate (0.8 versus 2.3 hospitalizations per patient per year). The relationship between arginine fortification and plasma lysine indicates that transport competition exists at both cerebrovascular and gastrointestinal barriers, suggesting their co-administration is key to efficacy. Monitoring the ratio between lysine and arginine in diet and plasma may prove a useful strategy for treating children with GA1.

Isotopic and dental evidence for infant and young child feeding practices in an imperial Roman skeletal sample

This study integrates isotopic, palaeopathological, and historical evidence to investigate infant and young child feeding practices in a Roman period (1st to 3rd centuries AD) skeletal sample from the Isola Sacra necropolis (Rome, Italy). Stable isotope analysis of bone collagen from 37 rib samples indicates that transitional feeding began by the end of the first year and weaning occurred by 2-2.5 years of age. Both delta(15)N and delta(13)C data clearly show the trophic level effect associated with breastfeeding. Childhood diet is investigated using dental pathology data in the deciduous dentitions of 78 individuals aged between 1 and 12 years. The presence of calculus, caries, and tooth wear in young children suggests that individuals were provided complementary foods and other items that impacted their dental health at an early age. The isotopic and dental data are generally consistent with the historical evidence from the Roman period with respect to the general timetable of weaning and the character of complementary foods. This is the first study to integrate isotopic and deciduous dental pathology data to explore infant and young child feeding practices in the Roman world.

A marker of growth differs between adolescents with high vs. low sugar preference

Sweet preference is higher in childhood than adulthood but the mechanism for this developmental shift is not known. The objective of this study was to assess perceptual, physiological and eating habit differences between children preferring solutions high in sugar (high preference) and children preferring solutions low in sugar (low preference). We tested 143 children (11- to 15-years old) using sip and spit methodology to assess their hedonic profile, detection threshold, and perceived intensity of sucrose. Their plasma concentration of several hormones, a biomarker of bone-growth, body size, puberty stage, and dietary habits were measured. Eighty-eight children were classified as high preference and 53 were classified as low preference based on their hedonic ratings to a series of sucrose solutions. A marker of bone growth measured in urine and plasma leptin adjusted for body weight were significantly lower in the low preference group. Children with high and low preference patterns did not differ in sensory aspects of sucrose perception, nor did they differ in age, body mass index percentile, or dietary restraint. The change in sugar preference from high to low during adolescence appears to be associated with the cessation of growth.

Advances in collagen cross-link analysis

The combined application of ion-trap mass spectrometry and peptide-specific antibodies for the isolation and structural analysis of collagen cross-linking domains is illustrated with examples of results from various types of collagen with the emphasis on bone and cartilage. We highlight the potential of such methods to advance knowledge on the importance of post-translational modifications (e.g., degrees of lysine hydroxylation and glycosylation) and preferred intermolecular binding partners for telopeptide and helical cross-linking domains in regulating cross-link type and placement.

A noninvasive analysis of urinary musculoskeletal collagen metabolism markers from rhesus monkeys subject to chronic hypergravity

A decrease in load-bearing activity, as experienced during spaceflight or immobilization, affects the musculoskeletal system in animals and humans, resulting in the loss of bone and connective tissue. It has been suggested that hypergravity (HG) can counteract the deleterious effects of microgravity-induced musculoskeletal resorption. However, little consensus information has been collected on the noninvasive measurement of collagen degradation products associated with enhanced load-bearing stress on the skeleton. The purpose of this study is to assess the urinary collagen metabolic profiles of rhesus monkeys (Macaca mulatta) during 1) 2 wk of basal 1 G (pre-HG), 2) 2 wk of HG (2 G), and 3) two periods of post-HG recovery (1 G). Urine was collected over a 24-h period from six individual rhesus monkeys. Hydroxyproline (Hyp) and collagen cross-links (hydroxylysylpyridinoline and lysylpyridinoline) were measured by reverse-phase HPLC. Urinary calcium, measured by atomic absorption, and creatinine were also assayed. The results indicate no changes in nonreducible cross-links and Hyp during HG. Collagen cross-link biomarker levels were significantly elevated during the 2nd wk of HG. Urinary calcium content was significantly lower during HG than during the 1-G control period, suggesting calcium retention by the body. We conclude that there is an adaptation of the nonhuman primate musculoskeletal system during hyperloading and that noninvasive measurements of musculoskeletal biomarkers can be used as indicators of collagen and mineral metabolism during HG and recovery in nonhuman primates.

The amino- and carboxyterminal cross-linked telopeptides of collagen type I, NTX-I and CTX-I: a comparative review

Bone diseases such as osteoporosis or bone metastases are a continuously growing problem in the ageing populations across the world. In recent years, great efforts have been made to develop specific and sensitive biochemical markers of bone turnover that could help in the assessment and monitoring of bone turnover. The amino- and carboxyterminal cross-linked telopeptides of type I collagen (NTX-I and CTX-I, respectively) are two widely used bone resorption markers that attracted great attention due to their relatively high sensitivity and specificity for the degradation of type I collagen, and their rapid adaptation to automated analyzers. However, the clinical performance of both markers differs significantly depending on the clinical situation. These differences have caused considerable confusion and uncertainty. If used correctly, both markers have great potential to improve the management of many bone diseases. We here review the biochemistry, analytical background and clinical performance of NTX-I and CTX-I, as documented in the accessible literature until March 2008.

Clinical application of biochemical markers of bone turnover

With the ageing population in most countries, disorders of bone and mineral metabolism are becoming increasingly relevant to every day 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 have markedly grown. Together with clinical and imaging techniques, biochemical tests play an important role in the assessment and differential diagnosis of metabolic bone disease. In recent years, the isolation and characterisation of cellular and extracellular components of the skeletal matrix have resulted in the development of molecular markers that are considered to reflect either bone formation or bone resorption. These biochemical indices are non-invasive, comparatively inexpensive and, when applied and interpreted correctly, helpful tools in the diagnostic and therapeutic assessment of metabolic bone disease. This review provides an overview of the current evidence regarding the clinical use of biochemical markers of bone remodelling in bone disease, with an emphasis on osteoporosis.

Osteoporosis

Effective therapies are available for the patient who has arthritic osteoporosis. The approach is critical to ensure an optimal quality of life in these individuals who suffer with a disease that is clearly treatable.

Positive effects of a chicken eggshell powder-enriched vitamin–mineral supplement on femoral neck bone mineral density in healthy late post-menopausal Dutch women

Although bone metabolism is largely under genetic control, the role of nutrition is considerable. The present study evaluates the effects of chicken eggshell powder, a new source of dietary Ca, and purified CaCO3 on bone mineral density (BMD) of the lumbar spine and hip. Besides BMD we also looked at biochemical markers of bone and Ca metabolism. Both Ca sources were provided in combination with minerals and vitamins including Mg, cholecalciferol and phylloquinone. We designed a randomised, double-blind, placebo-controlled study to take place over 12 months. Healthy Caucasian women (n 85), selected by age (≥50 and <70 years), from the databases of general practitioners were recruited by telephone calls. They had to be at least 5 years post-menopausal, with lumbar spine T-score being >-2·5. At baseline, their mean habitual daily Ca intake was adequate. The women were randomly allocated to: eggshell powder-enriched (group A; n 24), purified CaCO3-enriched (group B; n 22), or a placebo product (group C; n 27). BMD was measured at baseline and then after 6 and 12 months of supplementation as were the biochemical markers bone-specific alkaline phosphatase, amino-terminal propeptide extension of type I collagen, deoxypyridinoline, calcitonin, intact parathyroid hormone, calcidiol, and urinary Ca. After 12 months of supplementation, only mean BMD of the femoral neck in group A was significantly increased (P=0·014) by 1·75 % (95 % CI 0·18, 3·32) compared with a decrease of -0·60 % (95 % CI -1·92, 0·72) in group C. This increase coincided with significant decreases in markers of bone resorption and formation. No significant changes were seen in BMD at other sites, including lumbar spine, nor in groups B and C. No differences were found between groups A and B, or B and C. The present study indicates that healthy late post-menopausal women with an adequate Ca intake at baseline may increase BMD of the hip within 12 months following supplementation with the chicken eggshell powder-enriched supplement.

Size-corrected BMD decreases during peak linear growth: implications for fracture incidence during adolescence

Peak adolescent fracture incidence at the distal end of the radius coincides with a decline in size-corrected BMD in both boys and girls. Peak gains in bone area preceded peak gains in BMC in a longitudinal sample of boys and girls, supporting the theory that the dissociation between skeletal expansion and skeletal mineralization results in a period of relative bone weakness.

INTRODUCTION

The high incidence of fracture in adolescence may be related to a period of relative skeletal fragility resulting from dissociation between bone expansion and bone mineralization during the growing years. The aim of this study was to examine the relationship between changes in size-corrected BMD (BMDsc) and peak distal radius fracture incidence in boys and girls.

MATERIALS AND METHODS

Subjects were 41 boys and 46 girls measured annually (DXA; Hologic 2000) over the adolescent growth period and again in young adulthood. Ages of peak height velocity (PHV), peak BMC velocity (PBMCV), and peak bone area (BA) velocity (PBAV) were determined for each child. To control for maturational differences, subjects were aligned on PHV. BMDsc was calculated by first regressing the natural logarithms of BMC and BA. The power coefficient (pc) values from this analysis were used as follows: BMDsc = BMC/BA(pc).

RESULTS

BMDsc decreased significantly before the age of PHV and then increased until 4 years after PHV. The peak rates in radial fractures (reported from previous work) in both boys and girls coincided with the age of negative velocity in BMDsc; the age of peak BA velocity (PBAV) preceded the age of peak BMC velocity (PBMCV) by 0.5 years in both boys and girls.

CONCLUSIONS

There is a clear dissociation between PBMCV and PBAV in boys and girls. BMDsc declines before age of PHV before rebounding after PHV. The timing of these events coincides directly with reported fracture rates of the distal end of the radius. Thus, the results support the theory that there is a period of relative skeletal weakness during the adolescent growth period caused, in part, by a draw on cortical bone to meet the mineral demands of the expanding skeleton resulting in a temporary increased fracture risk.

Urinary excretion of deoxypyridinoline in Perthes' disease: a prospective, controlled comparative study in 83 children

Our aim was to investigate the relationship between urinary excretion of deoxypyridinoline (DPD) as a marker of bone resorption, and Perthes' disease. There were 39 children with Perthes' disease in the florid stage who collected first-morning urine samples at regular intervals of at least three months. The level of urinary DPD was analysed by chemiluminescence immunoassay and was correlated with the radiological stage of the disease as classified by Waldenström, and the severity of epiphyseal involvement according to the classification systems of Catterall and Herring. The urinary DPD levels of a group of 44 healthy children were used as a control. The median urinary DPD/creatinine (CREA) ratio was significantly reduced (p < 0.0001) in the condensation stage and increased to slightly elevated values at the final stage (p = 0.05) when compared with that of the control group. Herring-C patients showed significantly lower median DPD/CREA ratios than Herring-B patients (p = 0.03). The significantly decreased median DPD/CREA ratio in early Perthes' disease indicated a reduced bone turnover and supports the theory of a systemic aetiology. Urinary levels of DPD may therefore be used to monitor the course of Perthes' disease.

Pediatric reference intervals for bone markers

Bone markers are specific bone-derived molecules that reflect bone remodeling activity and can be classified into two categories: bone formation and bone resorption markers. Children have significantly elevated bone marker levels due to high skeletal growth velocity and rapid bone turnover during childhood growth. Many physiological and pathological processes may influence bone metabolism and bone marker concentrations during childhood growth. Measurements of bone markers may be useful in investigating skeletal diseases in children and monitoring the response to treatment. This review documents recent advances in analytical methods, preanalytical considerations related to each marker and particularly highlights the most valuable bone formation markers, bone alkaline phosphatase and osteocalcin, and bone resorption markers, pyridinium cross-links and cross-linked telopeptides. Age- and sex-specific pediatric reference intervals and their limitations in clinical application are also discussed.

Vitamin C status and collagen cross-link ratios in Gambian children

Vitamin C (ascorbate) is essential for hydroxylation of prolyl and lysyl residues in nascent collagen, the failure of which leads to connective tissue lesions of scurvy. Of the pyridinium-type cross-links in mature collagen, pyridinoline requires more hydroxylysyl residues than does deoxypyridinoline. Our study tested the hypothesis that pyridinoline:deoxypyridinoline ratios in urinary degradation products may vary with ascorbate status in man. These ratios were compared between British and Gambian prepubertal boys, mean age 8.3 years, and in Gambian boys between two seasons with contrasting ascorbate availability. The mean cross-links ratio in 216 British boys was 4.36 (SD 0.71), significantly greater (P<0.0001) than in sixty-two Gambian boys: 3.83 (SD 0.52). In the Gambians the cross-links ratio was significantly higher in the dry season (with high ascorbate intake and status) than in the rains (with low intake and status). A 7-week controlled intervention was carried out in Gambian boys during the rainy season (the 'hungry' season, when vitamin C-containing foods are virtually unavailable): 100 mg ascorbate/d was given to one group of thirty-two Gambian boys and placebo to another group. The intervention did not, however, significantly alter the cross-link ratio, possibly because the response time and/or intervention-response delay is >7 weeks. If confirmed, the putative association between ascorbate and collagen cross-link ratios in man could become the basis for a functional test for adequacy of ascorbate status.

Osteoporosis

Bone is a complex organ which contains an organic matrix which serves as scaffolding, includes mineral as calcium distributed in a pattern providing structure and serves as an ion reservoir for the body. Throughout life it dynamically changes in response to changes in activity, body mass, and weight bearing. It is important to define patients at risk for bone loss, since accrued bone loss leading to osteoporosis in the older population of both men and women is unacceptable. There are many different therapies including biphosphonates which can decrease loss of bone and decrease fracture risk in patients who already have had sustained a fracture. Newer therapies such as parathyroid hormone may improve the fracture risk even more than biphosphonates over a shorter period of time.

The pathophysiology of bone loss

Aging is associated with a decline in cancellous and cortical bone mass and with a deterioration of microarchitecture in both skeletal compartments. These changes are more marked in women than men and are exaggerated in patients with fracture. With the insight gained from histomorphometry, we are beginning to understand the cellular mechanisms that underlie these changes. We recognize that deterioration in microarchitecture contributes to fracture risk, independently of bone mass. Techniques to assess bone microarchitecture noninvasively in a clinical setting are currently under development; it is likely that advances in this area will improve our ability to identify and manage patients with osteoporosis in the not too distant future.

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.

Association between craniofacial growth and urinary bone metabolic markers (pyridinoline, deoxypyridinoline) in growing rats

Pyridinoline (Pyr) and deoxypyridinoline (Dpyr) are intermolecular cross-links of mature collagen and reflect the bone turnover. The purpose of this study was to elucidate the association between craniofacial growth and urinary Pyr and Dpyr levels. Lateral cephalograms and 24-hour urine were taken for 7 male rats from 5 to 20 wks old. The urinary Pyr and Dpyr were quantified by high-performance liquid chromatography. The neurocranium and upper viscerocranium exhibited significant increases in size, with the maximum rate at around 6 wks old. The mandible presented more substantial growth, with the maximum change at 8 wks old. The urinary Pyr and Dpyr levels gradually increased and reached the maximum at 8 wks old. No prominent association was found between neurocranial growth and urinary levels of pyridinium cross-links, whereas Pyr and Dpyr levels exhibited similar time-dependent metabolic changes to mandibular growth. In conclusion, it is shown that urinary pyridinium cross-links may be useful for the prediction of mandibular growth.

Instability and variability of urinary telopeptides and free crosslinks

BACKGROUND

The use of the urinary bone degradation markers, NTx and free Dpd, in the diagnosis and monitoring of pathological bone resorption has been studied intensely. Urinary NTx and Dpd are normalized by creatinine to account for differences in diuresis.

METHODS

We investigated the effects of storage (-20 degrees C for 119 days) on concentrations of NTx, Dpd and creatinine in the urine of 40 subjects. Precipitates (visible upon thawing) were resuspended, but specimens were not recentrifuged (in contrast to previous experiments).

RESULTS

After storage at -20 degrees C, the NTx and creatinine concentrations in urine specimens were significantly decreased by about 18% and 22% (p < 0.01 and p < 0.0001), respectively. Thus, the quotient of NTx/creatinine was slightly increased after storage (p < 0.05). Free Dpd and free Dpd/creatinine were both significantly increased after storage (p < 0.0001)--by about 20% and 60%, respectively.

CONCLUSIONS

We suggest that storage at -20 degrees C frees Dpd and denatures the epitope used in NTx quantification, and that these changes are usually masked by the removal of free Dpd via recentrifugation and by the decrease in creatinine in NTx/creatinine. Additionally, we suggest that the quotient Dpd/NTx should be evaluated as an alternative to normalizing via creatinine excretion.

Urinary creatinine instability falsely increases the deoxypyridinoline/creatinine quotient

BACKGROUND

The concentration of urinary deoxypyridinoline crosslinks (Dpd) (as in line 17)-normalized with respect to the urinary creatinine concentration is used as a biochemical marker of pathological bone resorption.

METHODS

The effect of various storage conditions on the stability of Dpd/creatinine in urine specimens was examined in a sample of 14 individuals without aseptic endoprosthetic loosening (control) and 14 patients with aseptic endoprosthetic loosening (AEL).

RESULTS

In the control group, values of Dpd/creatinine measured after 1 day of storage at -20 degrees C were significantly greater (p < 0.005) than values measured in fresh urine specimens. In the AEL group, increases in urinary Dpd/creatinine values were less pronounced (NS to p < 0.05). Increases in Dpd/creatinine were primarily the mathematical consequence of significant decreases in urinary creatinine concentration in the control group (p < 0.0001) and the AEL group (p < 0.05, after at least 7 days of storage). The decrease in urinary creatinine concentration appears to reach a plateau--between 75% and 80% of the original value--after approximately 10 days of storage.

CONCLUSION

To prevent falsely increased Dpd/creatinine quotients, we suggest that urinary creatinine should be measured exclusively in fresh urine specimens or consistently in specimens stored for at least 14 days at -20 or -80 degrees C.

Comparison of thyroid function in pregnant and non-pregnant Asian and western Caucasian women

BACKGROUND

Gestational thyrotoxicosis may be more prevalent in Asian women.

METHODS

We have measured thyroid function, ferritin and bone specific alkaline phosphatase (BALP) as peripheral markers of thyroid function and hCG in Asian and western Caucasian women in non-pregnant and early pregnancy.

RESULTS

TSH was lower in Asian women in non-pregnancy but not during normal pregnancy and this may reflect increased sensitivity of the thyroid gland to thyroid stimulation in the Asian population. No ethnic difference was found in FT3, FT4 or hCG but ferritin was lower and BALP higher in Asian women whether pregnant or not and this may be a reflection of iron balance and vitamin D status.

CONCLUSIONS

We found during normal pregnancy that dynamic patterns of change for thyroid hormones and hCG are not different in Asian and western Caucasian women. We have developed gestation related reference intervals, which are a pre-requisite to the study of ethnic differences in gestation thyrotoxicosis in pregnancy.

Osteopathia striata with cranial sclerosis

Osteopathia striata with cranial sclerosis (OS-CS) is a specific bone dysplasia manifested by hypertelorism, flat nasal bridge, frontal bossing, large head, hypoplastic maxilla, palate anomalies, chronic otitis media, hearing deficits, nasal obstruction, and neurological changes of deafness, facial palsy, ophthalmoplegia, and mental retardation. We will review the clinical and radiologic findings in a new patient from birth to 20 years; this is believed to be the thirty-fifth patient reported. OS-CS is 2.5 times more common in females and occurs as an autosomal dominant condition or a sporadic dominant mutation with patients presenting for evaluation from the newborn period to the fifth decade. Skeletal abnormalities are distinctive including sclerosis of the skull base and calvarium, linear striated densities in the long bones and pelvis, and poor development of the mastoid and sinus air cells. Radionuclide bone scans with SPECT indicated in our patient increased bone turnover which was supported by biochemical findings of increased pyridinoline excretion. The major complications are due to constriction of essential foramina at the skull base. The condition is not life-threatening but can produce disability.

A prospective study of quantitative ultrasound in children and adolescents

The accrual of optimal bone mass during childhood and adolescence is essential for the formation of a skeleton that will meet structural needs throughout life. Assessing bone health of children is becoming increasingly important in order to identify those who require interventions, and quantitative ultrasound (QUS) has appeal for these assessments. The purpose of this prospective study was to characterize changes in QUS values in 328 healthy children and adolescents over a 3-yr period. Measurements of QUS, height, weight, nutrient intake, fracture history, and Tanner stage were made at baseline and 3 yr later. Both females and males experienced significant increases in QUS values during the study. The rate of change of QUS peaked at an earlier age in females than in males, and maximum accumulation rates in both genders occurred at ages at which highest accumulation rates are seen with densitometry. Females exhibited higher QUS values than males during puberty, also similar to results for dual X-ray absorptiometry (DXA). This is the first report of prospective data of QUS in children and adolescents. Our findings that QUS values change during childhood and adolescence in a manner similar to DXA values, the "gold standard," provide support for the validity of using QUS to assess bone health in children and adolescents.

Determination of bone markers in pycnodysostosis: effects of cathepsin K deficiency on bone matrix degradation

Pycnodysostosis (Pycno) is an autosomal recessive osteosclerotic skeletal dysplasia that is caused by the markedly deficient activity of cathepsin K. This lysosomal cysteine protease has substantial collagenase activity, is present at high levels in osteoclasts, and is secreted into the subosteoclastic space where bone matrix is degraded. In vitro studies revealed that mutant cathepsin K proteins causing Pycno did not degrade type I collagen, the protein that constitutes 95% of organic bone matrix. To determine the in vivo effects of cathepsin K mutations on bone metabolism in general and osteoclast-mediated bone resorption specifically, several bone metabolism markers were assayed in serum and urine from seven Pycno patients. Two markers of bone synthesis, type I collagen carboxy-terminal propeptide and osteocalcin, were normal in all Pycno patients. Tartrate-resistent acid phosphatase, an osteoclast marker, was also normal in these patients. Two markers that detect type I collagen telopeptide cross-links from the N and C termini, NTX and CTX, respectively, were low in Pycno. A third marker which detects a more proximal portion of the C terminus of type I collagen in serum, ICTP, was elevated in Pycno, a seemingly paradoxical result. The finding of decreased osteoclast-mediated type I collagen degradation as well as the use of alternative collagen cleavage sites by other proteases, and the accumulation of larger C-terminal fragments containing the ICTP epitope, established a unique biochemical phenotype for Pycno.

Biochemical markers of bone turnover

Biochemical markers of bone turnover that are specific to bone allow study of the subtle changes in bone turnover associated with osteoporosis. They have been evaluated in Paget's disease of the bone and chronic renal failure. This review focuses on the use of biochemical markers of bone turnover in osteoporosis. The data in this review period are numerous and varied due to the growing interest in the use of biochemical markers of bone turnover in clinical practice. The data provide support for the use of the newer bone turnover markers for monitoring treatment of osteoporosis, if care is taken to minimize sources of variability.

Prostaglandin E2-bisphosphonate conjugates: potential agents for treatment of osteoporosis

Conjugates of bisphosphonates (potential bone resorption inhibitors) and prostaglandin E2 (a bone formation enhancer) were prepared and evaluated for their ability to bind to bone and to liberate, enzymatically, free PGE2. The conjugate 3, an amide at C-1 of PGE2 proved to be too stable in vivo while conjugate 6, a thioester, was too labile. Several PGE2, C-15 ester-linked conjugates (18, 23, 24 and 31) were prepared and conjugate 23 was found to bind effectively to bone in vitro and in vivo and to liberate PGE2 at an acceptable rate. A 4-week study in a rat model of osteoporosis showed that 23 was better tolerated and more effective as a bone growth stimulant than daily maximum tolerated doses of free PGE2.

Use of bone turnover marker, pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP), in the assessment and monitoring of bone metastasis in prostate cancer

BACKGROUND

We investigated whether a new marker of bone turnover, pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP), could be useful in the assessment of bone metastasis and in monitoring of the response to treatment in patients with prostate cancer with bone metastasis.

METHODS

In all, 58 patients with prostate cancer (25 with bone metastasis and 33 without bone metastasis) and 52 patients with benign prostate hypertrophy who were treated between June 1994-August 1997 were included in this study. All patients were newly diagnosed.

RESULTS

Serum ICTP levels in patients with prostate cancer with bone metastasis were significantly higher than those in patients with prostate cancer without bone metastasis (P<0.0001) or with benign prostate hypertrophy (P<0.0001). No significant differences were observed in serum ICTP levels between patients with prostate cancer without bone metastasis and those with benign prostate hypertrophy. Serum ICTP levels correlated significantly with Soloway's grading system for bone scans. Serum ICTP levels in patients with bone metastasis showed a significant downward trend in response to hormonal treatment.

CONCLUSIONS

The determination of serum ICTP levels is useful in the assessment of bone metastasis and in monitoring the response of bone metastasis to treatment to prostate cancer.

The Relationship between Urinary Pyridinoline, Deoxypyridinoline and Bone Metastasis in a Rat Breast Cancer Model

BACKGROUND: Bone metastasis from breast cancer is often recognized clinically, but there are nonetheless several difficulties in diagnosis. In this study we used an animal model of bone metastasis from breast cancer and clarified the relationship between the urinary Pyd/Cr and Dpd/Cr and the progression of bone metastasis, compared with other bone related markers: serum alkaline phosphatase bone isozyme (ALP-BI), osteocalcin, and calcium. METHODS: The evaluation of bone metastasis was assessed by histological examination of the thoracic and lumbar vertebrae. According to the histological findings 4 weeks after the tumor cell injection, 11 animals were retrospectively divided into 2 subgroups: (1) tumor-bearing rats with bone destruction due to bone metastasis (TBR-BD(+), n = 5), (2) tumor-bearing rats without bone destruction (TBR-BD(-), n =6). These animals were compared to age-matched controls without tumor cell injection (n =6). An additional 5 animals were sacrificed at 2 weeks after the tumor cell injection to evaluate micrometastasis to bone. RESULTS: The values of other markers for bone metastasis in animals with micrometastatic foci in bone marrow did not differ significantly from those of the controls. Pyd/Cr and Dpd/Cr in the TBR-BD(+) group were significantly higher than those of the TBR-BD(-) and the control group (233 +/- 78.3 vs 93.8 +/- 6.5, 98.5 +/- 18.7, 123.1 +/- 35.9 vs 67.9 +/- 6.2, 60.6 +/- 9.8, p< 0.01), while there were no significant differences between TBR-BD(-) and the control. CONCLUSION: Both Pyd/Cr and Dpd/Cr are correlated significantly with the volume of bone metastasis, and are useful for the diagnosis and evaluation of progression of bone metastasis compared with other markers.

Skeletal effects of aging in male rhesus monkeys

Age-related bone loss in men is receiving increased attention. In light of this, animal models for male bone loss are desirable. This study examined the effects of age and osteoarthritis (OA) on bone mineral content (BMC), bone mineral density (BMD), and markers of bone turnover and skeletal relevance in 56 male rhesus monkeys 4-34 years of age. BMC and BMD increased at all sites from 4 to 10 years of age. Male rhesus monkeys reach peak bone mass at approximately 10 years of age after which bone mass is lower at the lateral spine and distal radius. Markers of bone turnover (osteocalcin and carboxyterminal telopeptide of type I collagen [ICTP]) decreased with age. There was no relationship between PTH, 25-hydroxyvitamin D, FSH, or testosterone and age. With advancing age, the prevalence of lumbar spine OA increases dramatically, masking decreases in posteroanterior spine bone mass that are clear in the lateral projection. These data suggest that male rhesus monkeys sustain age-related bone loss in the absence of nutritional or gonadal steroid deficiencies. These animals may prove useful in studying the mechanisms of age-related bone loss.

Basic principles and clinical applications of biochemical markers of bone metabolism: biochemical and technical aspects

The interest in and the need for effective measures to be used in the screening, diagnosis, and follow-up of disorders of connective tissue, bone, and mineral metabolism has markedly grown. Next to clinical and imaging techniques, indices of bone turnover have come to play an important role in the assessment of metabolic bone disease. In osteoporosis, recent research has shown that bone markers may also be used to predict future bone loss and hip fractures (in larger cohorts of older patients), identify individuals at risk for osteoporosis, select therapy, and predict and monitor the therapeutic response in individual patients. The development of new markers of bone metabolism has greatly enriched the spectrum of serum and urine analytes used in the assessment of skeletal pathologies. Besides total alkaline phosphatase, other markers such as bone-specific alkaline phosphatase, osteocalcin, or the collagen propeptides are being used to measure bone formation. Bone resorption, previously assessed only by the measurement of urinary calcium and hydroxyproline, may now be detected more precisely by a number of new serum and urine markers. Among these, the pyridinium crosslinks and the telopeptides of collagen type I are presently considered the most specific markers of bone resorption. More recently, bone sialoprotein has also been suggested as a marker of bone resorption in serum. Tartrate-resistant acid phosphatase is now measurable by immunoassay. This article surveys the biochemistry and relevant technical aspects of the currently available markers of bone metabolism.

Increased urinary excretion of pyridinoline and deoxypyridinoline in a girl with congenital contractural arachnodactyly

Congenital contractural arachnodactyly (CCA) is caused by mutations in the gene for fibrillin 2 glycoprotein, a component of connective tissue. The causes of osteodystrophy or osteodysplasia in CCA are unknown. We report bone metabolism in a 28 month-old girl with CCA. Serum alkaline phosphatase and osteocalcin levels were 650 IU/l and 22 ng/ml at 1.5 months old (control: 530+/-65, 16.5+/-4.3), and 580 IU/l and 21 ng/ml at 28 months old (control: 465+/-58, 15.0+/-3.5), i.e. in upper-normal levels. The urinary pyridinoline and deoxypyridinoline levels were 1176 and 194 micromol/mol creatinine at 1.5 months old (control: 329+/-76, 63+/-12), and 407 and 111 micromol/mol cr at 28 months old (control: 231+/-49, 50+/-11), apparently higher than the control values. These findings may indicate that abnormal fibrillin may impair bone metabolism and cause the osteodystrophy or osteodysplasia in CCA.

Bone biomarkers as tools in osteoporosis management

Biochemical tests that can index bone turnover rate in the patient are increasingly being used in the study and management of osteoporosis. Markers of bone formation and resorption are reviewed here, including their molecular basis, relative strengths and weaknesses in clinical performance, and future potential. A bone mass measurement (e.g., by dual-energy x-ray absorptiometry) and a biochemical index of bone turnover provide different but complementary information that can aid in predicting risk of future bone loss and osteoporotic fracture. A specific and responsive bone resorption marker can also be used to monitor and establish the short-term effectiveness of an antiresorptive therapy in the patient. Bone-specific alkaline phosphatase (an osteoblast enzyme) and osteocalcin (a bone matrix protein) levels in serum are the best markers of bone formation. Collagen degradation products in urine, particularly cross-linked telopeptides and pyridinolines, have the highest specificity to bone resorption activity. The telopeptide markers (NTx and CTx) appear to be the most specific and responsive markers of systemic osteoclast activity.

Urinary assays for desmosine and hydroxylysylpyridinoline in the detection of cirrhosis

BACKGROUND/AIMS

Non-invasive markers of liver fibrosis have great potential for both the diagnosis and therapy of liver disease and cirrhosis. The aim of this study was to evaluate the potential of urinary amino acids desmosine (DES) and isodesmosine (IDES) derived from the breakdown of elastin and hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) derived from fibrillar collagen in diagnosing chronic liver disease.

METHODS

We studied 48 patients with chronic liver disease who had varying degrees of liver fibrosis, graded 0-6 using a modified Knodell score, and 20 control subjects without liver disease. Urinary DES (microg/g creatinine) and HP (nmol/mmol creatinine) were measured by an isotope dilution, high performance liquid chromatography method. For liver disease patients, aminoterminal propeptide of type III procollagen (PIIINP) and alanine aminotransferase were determined. The urine and serum markers were correlated to degree of fibrosis and inflammation on liver biopsies. Differences between groups were analyzed by ANOVA and multiple linear regression was applied to determine independence of variables. Sensitivity, specificity and receiver operating curves were derived for each marker.

RESULTS

In the 17 patients with liver fibrosis score of 5-6, mean urinary DES, IDES, HP and LP were all significantly greater than in the control group (p<0.05). Urinary DES and IDES correlated best with fibrosis score, r=0.61 for both markers. The correlation coefficient between serum PIIINP and fibrosis score was 0.47. Urinary DES and HP each had an overall diagnostic accuracy of 77% for fibrosis. Combining markers improved accuracy to over 80%. No correlation was seen between the urinary markers and inflammation scores.

CONCLUSIONS

Urinary DES and HP are potentially useful clinical markers for liver fibrosis, especially when used in combination or in association with PIIINP.

Single-column high-performance liquid chromatographic-fluorescence detection of immature, mature, and senescent cross-links of collagen

A high-performance liquid chromatographic-fluorescence detection method of reducible (immature) and nonreducible (mature and senescent) cross-links of collagen was established without the use of a radioisotope and preliminary fractionation step. This method used a gradient elution procedure of sodium citrate buffer containing 7% ethanol. The reducible cross-links (dihydroxylysinonorleucine, hydroxylysinonorleucine, and lysinonorleucine) and nonreducible cross-link (histidinohydroxylysinonorleucine) were detected by O-phthalaldehyde derivatization with the postcolumn method, whereas other nonreducible cross-links (pyridinoline, deoxypyridinoline, and pentosidine) were detected by natural fluorescence. The linear ranges of contents of the O-phthalaldehyde derivative cross-links and the natural fluorescent nonreducible cross-links were 20-600, 5-500 (pyridinoline, deoxypyridinoline), and 0.2-20 pmol (pentosidine), respectively. Tissue containing 1-2 mg dry wt of collagen was adequate for duplicate analyses of the reducible and nonreducible cross-links. An equivalent of 0.25 mg of hydrolyzed collagen could be analyzed by this HPLC system. Using this system, age-related changes in the cross-links of collagen from human connective tissues were also investigated.

Procollagen propeptide and pyridinium cross-links as markers of type I collagen turnover: sex- and age-related changes in healthy children

The correlations among age, gender, body size parameters, and type I collagen metabolism were evaluated in 183 healthy infants, aged 8.5-27.5 months. Collagen formation was assessed by measuring serum type I collagen carboxy-terminal propeptide, and degradation was determined by urinary pyridinoline and deoxypyridinoline (measured by high performance liquid chromatography) and cross-linked N- and C-terminal telopeptides of type I collagen (measured by NTx and CrossLaps assays). A new RIA specific for deoxypyridinoline was also evaluated. The results provide reference values at 10 months and 2 yr of age, including cross-linked C-terminal telopeptides (1492 +/- 685 and 1510 +/- 446 in boys; 1705 +/- 612 and 1849 +/- 611 micrograms/mmol creatinine in girls; mean +/- 1 SD). There was a good correlation between the high performance liquid chromatography and RIA data for deoxypyridinoline, showing that the RIA method is suitable for use in healthy children. Some correlations were found among peptide-bound cross-links, serum type I collagen carboxy-terminal propeptide, and the anthropometric parameters, suggesting that these peptides reflect bone resorption and also overall body type I collagen. Finally, there were age- and sex-related differences in the urinary excretion of the collagen degradation markers, suggesting that, unlike boys, girls maintain a high degree of collagen degradation up to the age of 24 months despite a decrease in their rate of collagen formation.

Prospective ten-month exercise intervention in premenarcheal girls: positive effects on bone and lean mass

Enhancement of bone mineral acquisition during growth may be a useful preventive strategy against osteoporosis. The aim of this study was to explore the lean mass, strength, and bone mineral response to a 10-month, high-impact, strength-building exercise program in 71 premenarcheal girls, aged 9-10 years. Lean body mass, total body (TB), lumbar spine (LS), proximal femur (PF), and femoral neck (FN) bone mineral were measured using the Hologic QDR 2000+ bone densitometer. Strength was assessed using a grip dynamometer and the Cybex isokinetic dynamometer (Cybex II). At baseline, no significant difference in body composition, pubertal development, calcium intake, physical activity, strength, or bone mineral existed between groups. At completion, there were again no difference in height, total body mass, pubertal development, calcium intake, or external physical activity. In contrast, the exercise group gained significantly more lean mass, less body fat content, greater shoulder, knee and grip strength, and greater TB, LS, PF, and FN BMD (exercise: TB 3.5%, LS 4.8%, PF 4.5%, and FN 12.0%) compared with the controls (controls: TB 1.2%, LS 1.2%, PF 1.3%, and FN 1.7%). TB bone mineral content (BMC), LS BMC, PF BMC, FN BMC, LS bone mineral apparent density (BMAD), and FN bone area also increased at a significantly greater rate in the exercise group compared with the controls. In multiple regression analysis, change in lean mass was the primary determinant of TB, FN, PF, and LS BMD accrual. Although a large proportion of bone mineral accrual in the premenarcheal skeleton was related to growth, an osteogenic effect was associated with exercise. These results suggest that high-impact, strength building exercise is beneficial for premenarcheal strength, lean mass gains, and bone mineral acquisition.

Osteoclasts generate cross-linked collagen N-telopeptides (NTx) but not free pyridinolines when cultured on human bone

Urinary excretion of the cross-linked alpha 2(I) N-telopeptide (NTx) of type I collagen has proven in clinical studies to provide a highly responsive and specific index of bone resorption. In order to understand better the biological basis of the specificity and responsiveness of this marker, we examined whether osteoclasts cultured on human bone could generate immunoreactive NTx peptide. Mouse bone marrow cultures stimulated with 1,25 diliydroxyvitamin D3 (1,25(OH)2D3) and hydrocortisone to produce osteoclasts, were cocultured on human bone particles or dentin slices. Aliquots of culture medium were assayed for NTx by enzyme-linked immunosorbent assay (ELISA). NTx was detected in the medium 5 days after the addition of bone and continued to be produced linearly over the 14-day culture period. NTx production required attachment to the bone particles or dentin slices of mononuclear and multinuclear cells that stained for tartrate-resistant acid phosphatase. Surface area of resorbed dentin was highly correlated with medium NTx concentration (R2 = 0.84). Production of NTx was suppressed by the osteoclast inhibitors, calcitonin and alendronate, in a dose-dependent manner. Two other markers of bone resorption, hydroxylysyl pyridinoline and lysyl pyridinoline, were found in peptide linkage in the culture medium but not in free form; indicating that the osteoclasts had degraded the bone collagen to peptides but not to the free cross-linking amino acids.

Bone markers

The recent development of specific and sensitive biochemical markers reflecting the overall rate of bone formation and bone resorption, has markedly improved the non-invasive assessment of bone turnover in various metabolic bone diseases, especially osteoporosis. The immunoassay of human osteocalcin recognizing the intact molecule and its major proteolytic fragment, along with that of bone alkaline phosphatase, are currently the most sensitive markers to assess bone formation. For bone resorption, the total urinary excretion of pyridinoline crosslinks measured by high pressure liquid chromatography has shown its superiority over all other markers for the clinical assessment of osteoporosis. The recent development of immunoassays recognizing either the free pyridinoline crosslinks or pyridinoline crosslinked-type I collagen peptides in urine and serum should allow a broad use of this sensitive resorption marker. Recent studies, some of them still in progress, define the clinical use of these markers: first, to improve the prognostic assessment of post-menopausal women in combination with bone mass measurement, i.e. their risk of developing osteoporosis and, ultimately, fractures and, second, to monitor the efficacy of anti-resorption drugs.

Bone-turnover metabolites as clinical markers of bone metastasis in patients with prostatic carcinoma

BACKGROUND

Candidate markers of prostatic metastases to bone, urinary deoxypyridinoline, serum carboxy-terminal propeptide of type 1 procollagen (P1CP), and pyridinoline cross-linked carboxy-terminal telopeptide of type 1 collagen (1CTP), were measured to evaluate their prognostic efficacy.

METHODS

Urinary levels (mean +/- SD) of deoxypyridinoline were measured by a competitive immunoassay, and serum levels of P1CP and 1CTP were measured by radioimmunoassay in 30 patients with benign prostatic hyperplasia, 18 patients with prostatic carcinoma without bone metastases, and 27 patients with prostatic carcinoma and bone metastases.

RESULTS

Urinary concentrations of deoxypyridinoline (pmol/micromol creatinine) in patients with prostatic carcinoma and bone metastases (10.4 +/- 7.7) were significantly higher than those in similar patients without bone metastases (4.3 +/- 1.3) and those in patients with benign prostatic hyperplasia (3.8 +/- 1.2). Serum levels of P1CP and 1CTP (ng/mL) in patients with prostatic carcinoma and bone metastases (262.6 +/- 188.7 and 10.3 +/- 9.5, respectively) were significantly higher than those in similar patients without bone metastases (118.1 +/- 30.2 and 4.3 +/- 1.4, respectively) and those in patients with benign prostatic hyperplasia (93.9 +/- 25.1 and 3.3 +/- 1.1, respectively). Serial measurements of urinary deoxypyridinoline and serum P1CP and 1CTP were correlated with a positive response to treatment (reduced measurements) and with the clinical progression of disease (increased measurements) before detection of new bone lesions by bone scintigram.

CONCLUSION

Urinary deoxypyridinoline, serum P1CP, and serum 1CTP should be useful markers in confirming and monitoring prostatic carcinoma metastases to bone.

Bone turnover in neonates: changes of urinary excretion rate of collagen type I cross-linked peptides during the first days of life and influence of gestational age

New markers have been used to monitor the changes of bone turnover occurring during growth. Data on bone turnover rate during the perinatal period are, however, very scarce. In the present study we evaluated bone turnover rate, assessed by the measurement of urinary N-terminal telopeptide of type I collagen (NTx) concentrations, at different gestational ages, and we documented the trend of bone turnover rate occurring in the first days after birth. Urine samples were obtained from 83 healthy full term newborn infants, 16 preterm, and 17 infants of diabetic mothers (IDMs). The first miction after birth was collected. Urine samples were also collected 24 and 48 h after birth. NTx was measured by an enzyme-linked immunosorbent assay (Osteomark, Ostex International, Inc. Seattle, WA). The relationship between NTx at birth and all the other variables has been evaluated using multiple regression analysis. The changes of NTx excretion over time and the effect of the groups were studied by multivariate analysis of variance (MANOVA) for repeated measures. We found a remarkable association between gestational age and NTx concentrations at birth (R = 0.56; p < 0.00001). NTx concentrations showed a progressive decrement, reaching a nadir between the 38th and the 42nd week of gestation. The NTx concentrations changed significantly during the first 48 h of life in the three groups. Moreover, preterm infants had NTx excretion values at birth significantly higher than full term infants (p < 0.001), whereas NTx excretion rates of IDMs were not different from those of the other two groups of subjects. In conclusion, gestational age seems to be the major determinant of bone turnover in neonates; NTx excretion rate is higher before term, it slows in proximity of delivery, and it increases significantly during the first 48 h of life. Preterm infants have higher bone turnover rate than full term infants. NTx excretion rate of IDMs was comparable with those of the control subjects.

Determination of pyridinium crosslinks in serum an optimization of sample preparation

Urinary pyridinoline (UPD) and deoxypyridinoline (UDPD) are selective markers in kinetic studies of mature collagen degradation in connective tissue, especially in bone. In patients with renal dysfunction, the determination of UPD and UDPD is not entirely reliable, while in anuretic patients it is impossible. As renal dysfunction is considered a risk factor for bone diseases, it is essential to determine both markers directly in the serum (SPD and SDPD). Due to the high serum concentrations of proteins, which during acid hydrolysis are converted to amino acid hydrochlorides, the system butanol-water is sometimes separated into two phases during sample preparation. Should this fact not be taken into account, the usual sample processing on a cellulose sorbent could yield substantially lower false results. This calls for some preventive measures: to ensure the homogeneity of the system containing n-butanol it is recommended to add an appropriate third component, e.g. methanol.