Decreased beta-isomerization of the C-terminal telopeptide of type I collagen alpha 1 chain in Paget's disease of bone.
In Paget's disease of bone, the normal lamellar bone is replaced by a woven structure with an irregular arrangement of collagen fibers. In this study, we investigated whether the degree of beta-isomerization within C-telopeptide of alpha 1 chain of type I collagen was altered in Paget's disease compared with other bone diseases with no alteration of bone structure. In Paget's disease (n = 26), but not in patients with primary hyperparathyroidism (n = 6) or hyperthyroidism (n = 17), the urinary excretion of nonisomerized (alpha) fragments derived from degradation of type I collagen C-telopeptide (CTX) was markedly increased compared with beta-isomerized CTX (+ 13-fold vs. + 3.5-fold over controls) resulting in an urinary alpha CTX/beta CTX ratio 3-fold higher than in controls (2.6 +/- 1.0 vs. 0.8 +/- 0.3, p < 0.001). In five pagetic patients in complete remission, as demonstrated by normal total alkaline phosphatase activity, the alpha CTX/beta CTX ratio was normal. The immunohistochemistry of normal and pagetic human bone sections showed a preferential distribution of alpha CTX within woven structure, while lamellar bone was intensely stained with an anti-beta CTX antibody, suggesting a lower degree of beta-isomerization of type I collagen in the woven pagetic bone. In collagenase digest of human bone specimens, we found a lower proportion of beta-isomerized type I collagen molecules in pagetic bone (40% of beta CTX) than in normal bone taken from trabecular (68%) and cortical compartments (71%). In conclusion, we found that in Paget's disease the alpha CTX/beta CTX ratio in bone and in urine is markedly increased. This altered beta isomerization can be accurately detected in vivo by measuring urinary degradation products arising from bone resorption.
Garnero
P
P
INSERM Unit 403, Hôpital E. Herriot, Lyon, France.
Fledelius
C
C
Gineyts
E
E
Serre
C M
CM
Vignot
E
E
Delmas
P D
PD
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000596:Amino Acids / Q000652:urine; D015415:Biomarkers; D001842:Bone and Bones / Q000737:chemistry; D003094:Collagen / Q000737:chemistry / Q000378:metabolism* / Q000652:urine; D024042:Collagen Type I; D005260:Female; D006801:Humans; D007536:Isomerism; D008297:Male; D008875:Middle Aged; D008956:Models, Chemical; D010001:Osteitis Deformans / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry / Q000378:metabolism* / Q000652:urine
D000596:Amino Acids; D015415:Biomarkers; D024042:Collagen Type I; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; C036020:deoxypyridinoline; D003094:Collagen