A. Tokita et al., GENETIC INFLUENCES ON TYPE-I COLLAGEN-SYNTHESIS AND DEGRADATION - FURTHER EVIDENCE FOR GENETIC-REGULATION OF BONE TURNOVER, The Journal of clinical endocrinology and metabolism, 78(6), 1994, pp. 1461-1466
Circulating osteocalcin, a marker of bone formation, is under strong g
enetic influence, and this effect is related to the genetic influence
on bone density. To examine genetic influences on bone turnover furthe
r, other markers of bone formation (serum carboxyterminal propeptide o
f type I procollagen, PICP), bone resorption (serum pyridinoline cross
linked carboxyterminal telopeptide of type I collagen, ICTP), and nono
sseous connective tissue synthesis (serum aminoterminal propeptide of
type III procollagen, PIIINP) were studied in 82 female twin pairs: 42
monozygotic (MZ) and 40 dizygotic (DZ) twin pairs (mean age, MZ; 48.4
yr; DZ; 45.6 yr). The intraclass correlation coefficients of MZ twin
pairs, rMZ, for serum PICP (0.78) and serum ICTP (0.68) were significa
ntly greater than the corresponding rDZ (0.31 and 0.36, respectively),
but a genetic effect on serum PIIINP was not demonstrable. Within DZ
twin pair differences in serum PICP predicted differences in lumbar sp
ine bone density (r = -0.37); higher serum PICP levels indicating the
twin with the lower lumbar spine bone density. Also within pair differ
ences in serum ICTP and PICP predicted differences in bone density at
the lumbar spine independent of serum osteocalcin. These data indicate
that both synthesis and degradation of type I collagen are geneticall
y determined and that this phenomenon is related to the genetic regula
tion of bone density.