Clinical and Technical Review - Tecomedical

6
Collagen metabolites and epitopes
DPD:
Deoxypyridinoline. Breakdown product from Type I collagen
degradation.
PYD:
Pyridinoline. Breakdown product from Type I collagen
degradation.
NTX:
Cross-linked N-terminal telopeptide resulting from
Type I collagen degradation. NTX = new synthesized and
agemodified bone matrix.
CTX:
C-terminal telopeptide resulting from Type I collagen
degradation, CTX alpha (New Bone Matrix), CTX beta (Old
Bone Matrix).
ICTP=CTX-MMP:
Carboxy-terminal telopeptide of type I collagen.
Larger epitope containing the smaller CTX epitope.
Helical Peptide:
Peptide derived from the helical region of the α-1 chain of
Type 1 collagen.
Note:
The concentration of the different biomarker are partly
dependent on age, gender, race as well as influenced by
diurnal rhythm, food intake etc. (see table on page 8). Age
dependency is of high importance if biomarker are used for
preclinical testing, especially in juvenile laboratory animals
(rat, mice).
Bone turnover regulators
Calcitonin:
Inhibits bone resorption, directly acts on osteoclasts.
Parathyroid hormone (PTH):
Key factor in the maintenance of calcium and phosphate
homeostasis. Stimulates osteoclasts activity.
1,25(OH) 2D3 :
1,25 dihydroxy vitamin D3 (or 1,25-dihydroxycholecalciferol)
is the biologically active form of vitamin D. It is
synthesized in the kidney from 25-vitamin D (25-hydroxycholecalciferol).
1,25(OH) 2D3 is the principal regulator
of calcium homeostasis in the body. It enhances the
efficiency of calcium.
Fetuin A:
Glycoprotein synthesized by liver, secreted into blood.
Deposited as noncollagenous protein in mineralized bones.
Potent inhibitor of soft tissue (vascular) calcification by binding
excess mineral in serum. Regulates calcium metabolism
and osteogenesis.
FGF-23:
Fibroblast Growth Factor 23. Important regulator of
phosphate homeostasis. Able to “block” renal reabsorption
of Pi. FGF-23 abnormalities are involved in renal phos-phate
wasting disorders leading to “hypophosphatemia”.
Literature:
1. Leeming DJ, Koizumi M, Byrjalsen I, Li B, Qvist P, Tanko LB.
The relative use of eight collagenous and noncollagenous markers
for diagnosis of skeletal metastases in breast, prostate, or
lung cancer patients.
Cancer Epidemiol Biomarkers Prev. 2006; 15(1):32-8.
2. Caulfield MP, Reitz RE. Biochemical markers of bone turnover and
their utility in osteoporosis. MLO-online April 2004.
Schaller S, Henriksen K, Hoegh-Andersen P, Søndergaard BC,
Sumer EU, Tanko LB, Qvist P and Karsdal MA. In vitro, ex vivo, and
in vivo methodological approaches for studying
therapeutic targets of osteoporosis and degenerative joint
diseases: How biomarkers can assist? Assay And Drug
Development Technologies 2005; 3:553-580.
3. Delmas PD, Eastell R, Garnero P, Seibel MJ and Stephan J. The use
of biochemical markers of bone turnover in osteoporosis.
Osteoporosis Int 2000: Supp 6: S2-17.