Diurnal variation and age differences in the biochemical markers of bone turnover in horses.
Biochemical markers of bone turnover provide sensitive, rapid, and noninvasive monitoring of bone resorption and formation. Serum concentrations of osteocalcin (OC) reflect rates of bone formation, and urinary concentrations of the pyridinium crosslinks pyridinoline (Pyd) and deoxypyridinoline (Dpd) are specific and sensitive markers of bone resorption. These markers are age-dependent and are used to detect and monitor changes in the rates of bone turnover in a variety of orthopedic diseases in humans and may prove to have similar application in horses. This study examined age differences and diurnal variation in OC, Pyd, and Dpd in eight adult geldings and seven weanling colts. Blood and urine were collected at regular intervals over 24 h. Serum OC and cortisol, and urinary Pyd and Dpd were analyzed. Mean 24-h concentrations of cortisol and all three markers were higher (P<.003) in weanlings than adults. Significant 24-h variation was observed in adult gelding OC, Pyd, and Dpd concentrations (P< .02). Adult OC concentrations were highest between 2400 and 0900; Pyd and Dpd peaked between 0200 and 0800. Similar patterns of bone turnover were observed in weanling values, but they were not significant (P>.17) owing to greater variability between individuals. Cortisol secretion varied (P<.001) over 24 h in both adults and weanlings and, thus, did not seem to be responsible for greater variability in markers of bone turnover between weanlings. These data demonstrate that diurnal rhythms exist for serum OC and urinary Pyd and Dpd in adult horses, as reported in humans, and that sample timing is an important consideration in future equine studies using these markers. (+info)
Biochemical markers of bone turnover in breast cancer patients with bone metastases: a preliminary report.
BACKGROUND: Some biochemical markers of bone turnover are expected to reflect the disease activity of metastatic bone tumor. In the present study six biochemical markers were evaluated to determine appropriate markers for the detection of metastatic bone tumors from breast cancer (BC). METHODS: A panel of bone turnover markers was assessed in 11 normocalcemic patients with bone metastases from BC and in 19 BC patients without clinical evidence of bone metastases. Bone formation was investigated by measuring serum bone isoenzyme of alkaline phosphatase (BALP), osteocalcin (OC) and carboxy-terminal propeptide of type I procollagen (PICP): Bone resorption was investigated by measuring serum carboxy-terminal telopeptide of type I collagen (ICTP), fasting urinary pyridinoline (Pyr) and deoxypyridinoline (D-Pyr). RESULTS: PICP was influenced by age and menopausal status. Significant correlations were observed between each of bone turnover markers except between BALP and OC. The mean levels of the six bone turnover markers were higher in patients with bone metastases than in those without them and significance was observed except for OC. The best diagnostic efficiency by receiver-operating characteristic (ROC) analysis was provided by ICTP followed by Pyr or D-Pyr, BALP, PICP and OC and significance was observed between ICTP and OC. Multiple logistic regression analysis adjusted by age revealed that the only significant marker related to bone metastases was ICTP. CONCLUSIONS: Serum ICTP appears to be the leading marker of bone metastases from BC. However, to reveal the clinical usefulness of these markers, further examination will be needed to account for the ease and cost-effectiveness of the measurements. (+info)
The associations of bone mineral density and bone turnover markers with osteoarthritis of the hand and knee in pre- and perimenopausal women.
OBJECTIVE: To determine whether Caucasian women ages 28-48 years with newly defined osteoarthritis (OA) would have greater bone mineral density (BMD) and less bone turnover over time than would women without OA. METHODS: Data were derived from the longitudinal Michigan Bone Health Study. Period prevalence and 3-year incidence of OA were based on radiographs of the dominant hand and both knees, scored with the Kellgren/Lawrence (K/L) scale. OA scores were related to BMD, which was measured by dual-energy x-ray absorptiometry, and to serum osteocalcin levels, which were measured by radioimmunoassay. RESULTS: The period prevalence of OA (K/L grade > or =2 in the knees or the dominant hand) was 15.3% (92 of 601), with 8.7% for the knees and 6.7% for the hand. The 3-year incidence of knee OA was 1.9% (9 of 482) and of hand OA was 3.3% (16 of 482). Women with incident knee OA had greater average BMD (z-scores 0.3-0.8 higher for the 3 BMD sites) than women without knee OA (P < 0.04 at the femoral neck). Women with incident knee OA had less change in their average BMD z-scores over the 3-year study period. Average BMD z-scores for women with prevalent knee OA were greater (0.4-0.7 higher) than for women without knee OA (P < 0.002 at all sites). There was no difference in average BMD z-scores or their change in women with and without hand OA. Average serum osteocalcin levels were lower in incident cases of hand OA (>60%; P = 0.02) or knee OA (20%; P not significant). The average change in absolute serum osteocalcin levels was not as great in women with incident hand OA or knee OA as in women without OA (P < 0.02 and P < 0.05, respectively). CONCLUSION: Women with radiographically defined knee OA have greater BMD than do women without knee OA and are less likely to lose that higher level of BMD. There was less bone turnover among women with hand OA and/or knee OA. These findings suggest that bone-forming cells might show a differential response in OA of the hand and knee, and may suggest a different pathogenesis of hand OA and knee OA. (+info)
Acute fasting diminishes the circadian rhythm of biochemical markers of bone resorption.
OBJECTIVE: Biochemical markers of bone turnover exhibit circadian rhythms with the peak during the night/early morning and the nadir in the late afternoon. The nocturnal increase in bone resorption could theoretically be caused by the absence of food consumption which brings about a decrease in net calcium absorption and an increase in parathyroid hormone (PTH), followed by increased bone resorption in response to the body's demand for calcium. The aim of the present study was to assess the influence of a 33-h fast on the circadian variation in biochemical markers of bone turnover. DESIGN: Eleven healthy premenopausal women (age: 24+/-5 years) participated in a randomised, cross-over study consisting of two periods: either 33h of fasting (fasting) followed 1 week later by a 33-h period with regular meals eaten at 0800-0830h, 1130-1230h and 1800-1900h (control) or vice versa. METHODS: Urinary CrossLaps (U-CL/Cr) corrected with creatinine, as a marker of bone resorption; serum osteocalcin (sOC) as a marker of bone formation; serum intact PTH (iPTH); serum phosphate; and serum calcium corrected with albumin. RESULTS: Both the fasting and the control periods showed a significant circadian rhythm in U-CL/Cr (P<0.001), but the decrease was significantly less pronounced in the morning hours during the fasting period. Fasting resulted in a significant decrease in serum iPTH (throughout the study period) as compared with the control period (P<0.05-0.001). No change was observed in sOC by fasting. CONCLUSION: Food consumption has a small influence on the circadian variation in bone resorption, independent of PTH. The fall in iPTH during fasting may be secondary to an increased bone resorption produced by fasting. (+info)
Immunoradiometric assay for intact human osteocalcin(1-49) without cross-reactivity to breakdown products.
BACKGROUND: Osteocalcin (Oc), a serum marker of bone turnover, circulates in several forms. We developed an assay for intact human Oc and investigated its clinical features. METHODS: We generated goat antibodies and N- and C-terminal Oc. The former was used on solid phase (polystyrene beads), and the latter was used as the tracer in an IRMA. RESULTS: The assay was linear with no cross-reactivity to Oc(1-43), total imprecision (CV) of <10%, and recovery of 100% +/- 10%. Assay values for intact Oc in EDTA plasma samples were unchanged at 18-25 degrees C for 6 h. Values for intact Oc in serum, EDTA plasma, and heparin plasma samples did not change after storage on ice for 8 h. Serum samples from patients with various conditions were stored at -70 or -135 degrees C for up to 5 years and yielded z-scores comparable to an Oc(1-43) IRMA for all conditions except for renal failure. In renal failure, the Oc(1-43) assay values were increased, whereas the intact assay values were in the reference interval. CONCLUSION: Decreases in Oc assay values are inhibited by calcium chelation, and slowed by reduced temperatures. The described assay for intact Oc allows improved specificity for bone compared with an assay for Oc(1-43). (+info)
Structure-function studies of new C-20 epimer pairs of vitamin D3 analogs.
A growing number of calcitriol (1alpha,25-dihydroxyvitamin D3) analogs have become available in recent years. Many of these analogs exhibit lower calcemic effects than calcitriol and inhibit cell proliferation and enhance cell differentation more efficiently than calcitriol. We have compared structure-function relationships of a series of new C-20 epimer (20-epi) vitamin D3 analogs with their natural C-20 counterparts. In human MG-63 osteosarcoma cells, quantification of cellular osteocalcin mRNA levels by Northern blot analysis and osteocalcin biosynthesis by radioimmunoassay indicated that most studied analogs at a concentration of 10 nm induced osteocalcin gene expression more efficiently than the parent compound, calcitriol. Interestingly, when the biological responses were compared with the binding affinities of the analogs to in-vitro translated human vitamin D receptor and with their ability to protect the receptor against partial proteolytic digestion, significant correlations were not observed. Further, molecular modelling of the compounds by energy minimization did not reveal marked differences in the three-dimensional structures of the analogs. These results suggest that higher than normal ligand binding affinity or 'natural' conformation of the ligand-receptor complex are not necessarily required for the 'superagonist' transactivation activity. The mechanism of action of the efficient analogs may involve stabilization and/or differential binding of transcriptional coactivators or transcription intermediary factors to the hVDR during transactivation. (+info)
A WW domain-containing yes-associated protein (YAP) is a novel transcriptional co-activator.
A protein module called the WW domain recognizes and binds to a short oligopeptide called the PY motif, PPxY, to mediate protein-protein interactions. The PY motif is present in the transcription activation domains of a wide range of transcription factors including c-Jun, AP-2, NF-E2, C/EBPalpha and PEBP2/CBF, suggesting that it plays an important role in transcriptional activation. We show here that mutation of the PY motif in the subregion of the activation domain of the DNA-binding subunit of PEBP2, PEBP2alpha, abolishes its transactivation function. Using yeast two-hybrid screening, we demonstrate that Yes-associated protein (YAP) binds to the PY motif of PEBP2alpha through its WW domain. The C-terminal region of YAP fused to the DNA-binding domain of GAL4 showed transactivation as strong as that of GAL4-VP16. Exogenously expressed YAP conferred transcription-stimulating activity on the PY motif fused to the GAL4 DNA-binding domain as well as to native PEBP2alpha. The osteocalcin promoter was stimulated by exogenous PEBP2alphaA and a dominant negative form of YAP strongly inhibited this activity, suggesting YAP involvement in this promoter activity in vivo. These results indicate that the PY motif is a novel transcription activation domain that functions by recruiting YAP as a strong transcription activator to target genes. (+info)
Inhibition of osteoblastic cell differentiation by lipopolysaccharide extract from Porphyromonas gingivalis.
Lipopolysaccharide from Porphyromonas gingivalis (P-LPS), an important pathogenic bacterium, is closely associated with inflammatory destruction of periodontal tissues. P-LPS induces the release of cytokines and local factors from inflammatory cells, stimulates osteoclastic-cell differentiation, and causes alveolar bone resorption. However, the effect of P-LPS on osteoblastic-cell differentiation remains unclear. In this study, we investigated the effect of P-LPS extract prepared by the hot-phenol-water method, on the differentiation of primary fetal rat calvaria (RC) cells, which contain a subpopulation of osteoprogenitor cells, into osteoblastic cells. P-LPS extract significantly inhibited bone nodule (BN) formation and the activity of alkaline phosphatase (ALPase), an osteoblastic marker, in a dose-dependent manner (0 to 100 ng of P-LPS extract per ml). P-LPS extract (100 ng/ml) significantly decreased BN formation to 27% of the control value and inhibited ALPase activity to approximately 60% of the control level on days 10 to 21 but did not affect RC cell proliferation and viability. P-LPS extract time-dependently suppressed the expression of ALPase mRNA, with an inhibitory pattern similar to that of enzyme activity. The expression of mRNAs for osteocalcin and osteopontin, matrix proteins related to bone metabolism, was markedly suppressed by P-LPS extract. Furthermore, P-LPS extract increased the expression of mRNAs for CD14, LPS receptor, and interleukin-1beta in RC cells. These results indicate that P-LPS inhibits osteoblastic-cell differentiation and suggest that LPS-induced bone resorption in periodontal disease may be mediated by effects on osteoblastic as well as osteoclastic cells. (+info)