Urinary osteocalcin as a marker of bone metabolism

Institute of Biomedicine, Department of Anatomy, University of Turku, Turku, Finland.
Clinical Chemistry (Impact Factor: 7.91). 03/2005; 51(3):618-28. DOI: 10.1373/clinchem.2004.043901
Source: PubMed


Osteocalcin (OC) is produced by osteoblasts during bone formation, and circulating OC has been used in clinical investigations as a marker of bone metabolism. OC is excreted into urine by glomerular filtration and can be found in urine as midmolecule fragments.
We developed and evaluated three immunoassays (U-MidOC, U-LongOC, and U-TotalOC) for the detection of various molecular forms of urine OC (U-OC). We evaluated the association of U-OC with other markers of bone turnover and with bone mass in 1044 elderly women and studied seasonal and circadian variation of U-OC.
U-OC correlated with other bone turnover markers [Spearman correlation (r), 0.30-0.57; P <0.0001], demonstrating the association between U-OC and skeletal metabolism. There was also a significant association between bone metabolism assessed by U-OC quartiles and bone mass assessed by total body bone mineral content (P <0.0001). The seasonal effects appeared to be rather small, but we observed a significant circadian rhythm similar to the one reported for serum OC with high values in the morning and low values in the afternoon.
The three immunoassays had unique specificities toward different naturally occurring U-OC fragments. U-OC concentrations measured with any of these assays correlated with bone turnover rates assessed by conventional serum markers of bone metabolism. The measurement of OC in urine samples could be used as an index of bone turnover in monitoring bone metabolism.

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    • "Urinary pyridinium crosslinks, Deoxypyridinoline (Dpd) and Pyridinoline (Pyd), were analyzed using HPLC analysis (ARUP Laboratories , University of Utah). Osteocalcin midfragments (U-MidOC) were detected by a previously described two-site immunoassay based on monoclonal antibodies 6F9 and 3H8 [28]. Undercarboxylated osteocalcin (unOC or Glu-OC), the metabolically active form of osteocalcin, was detected in urine samples with an EIA kit (Takara Bio Inc.). "
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    Bone 07/2012; 51(4):661-6. DOI:10.1016/j.bone.2012.07.016 · 3.97 Impact Factor
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    • "Three different assays of urinary osteocalcin, total osteocalcin (U-TotalOC), long osteocalcin (U-LongOC) and mid osteocalcin (U-MidOC) were analyzed as previously published with intra- and inter- assay CVs of 14% and < 27% (U-TotalOC), 4.3% and < 14% (U-LongOC), and 1.7% and < 12% (U-MidOC), respectively [21]. "
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