Bone turnover and bone collagen maturation in osteoporosis: effects of antiresorptive therapies.
Bone collagen maturation may be important for anti-fracture efficacy as the reduction in risk is only partly explained by a concomitant increase in BMD during anti-resorptive therapy. Different treatments caused diverse profiles in bone collagen degradation products, which may have implications for bone quality.


BACKGROUND
The aim of the present study was to evaluate the effect of different anti-resorptive treatments on bone collagen maturation measured as the ratio between the degradation products of newly synthesized and mature isomerized C-telopeptides of type I collagen.


METHODS
Participants were from cohorts of healthy postmenopausal women participating in double blind, placebo-controlled 2-year studies of alendronate, ibandronate, intranasal hormone replacement therapy (HRT), oral HRT, transdermal HRT, or raloxifene (n = 427). The non-isomerized alphaalphaCTX and isomerized betabetaCTX were measured in urine samples obtained at baseline, and after 6, 12, and 24 months of therapy.


RESULTS
Bone collagen maturation measured as the ratio between alphaalphaCTX and betabetaCTX showed that bisphosphonate treatment induced a collagen profile consistent with an older matrix with a 52% (alendronate) and 38% (ibandronate) reduction in the ratio between the two CTX isoforms vs. 3% and 15% with HRT or raloxifene, respectively.


CONCLUSIONS
Anti-resorptive treatments had different effects on the endogenous profile of bone collagen maturation. Whether that effect on bone collagen has an impact on bone strength independent on the treatment-dependent effect on BMD should be investigated.
Byrjalsen
I
I
Nordic Bioscience A/S, Herlev Hovedgade 207, Herlev DK-2730, Denmark. ib@nordicbioscience.com
Leeming
D J
DJ
Qvist
P
P
Christiansen
C
C
Karsdal
M A
MA
D000368:Aged; D019386:Alendronate / Q000494:pharmacology / Q000627:therapeutic use; D015519:Bone Density / Q000187:drug effects; D050071:Bone Density Conservation Agents / Q000494:pharmacology* / Q000627:therapeutic use; D003094:Collagen / Q000378:metabolism*; D024042:Collagen Type I / Q000652:urine; D004164:Diphosphonates / Q000494:pharmacology / Q000627:therapeutic use; D004311:Double-Blind Method; D015914:Estrogen Replacement Therapy; D005260:Female; D006801:Humans; D000077557:Ibandronic Acid; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000188:drug therapy / Q000503:physiopathology* / Q000652:urine; D010455:Peptides / Q000652:urine; D020849:Raloxifene Hydrochloride / Q000494:pharmacology / Q000627:therapeutic use
D050071:Bone Density Conservation Agents; D024042:Collagen Type I; D004164:Diphosphonates; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D020849:Raloxifene Hydrochloride; D003094:Collagen; D000077557:Ibandronic Acid; D019386:Alendronate