Effects of Ethnicity and Age or Menopause on the Remodeling and Turnover of Iliac Bone: Implications for Mechanisms of Bone Loss

Abstract

We measured histologic indices of bone remodeling and turnover separately on the cancellous, endocortical, and intracortical subdivisions of the endosteal envelope, and on the combined total surface, in transiliac bone biopsies obtained after double tetracycline labeling in 142 healthy women, aged 20 -74 years, 34 black and 108 white, 61 premenopausal and 81 postmenopausal. The data were analyzed by two-way analysis of variance of the four groups defined by age/menopause and ethnicity and by linear regression of the major variables on age. None of the interaction terms was significant and none of the regression slopes on age differed between blacks and whites, indicating that, as for the previously reported structural indices, the effects of ethnicity and of age/menopause are independent. Accordingly, the data were also analyzed separately for the effect of ethnicity (pre-and postmenopausal combined) and age/menopause (blacks and whites combined). The analyses led to the following conclusions. (1) The geometric mean bone formation rate on the combined total surface was 25% lower in blacks than in whites; other histologic differences between ethnic groups were inconsistent between surfaces. (2) Serum osteocalcin (OC) but not bone-specific alkaline phosphatase (BSAP) was lower by about 15% in blacks than in whites. (3) The lower bone turnover in blacks is most likely in the directed rather than in the stochastic component because of a higher bone mass and consequent reduced susceptibility to fatigue damage. (4) All Class 1 bone formation variables and the three resorption indices were significantly higher in the postmenopausal compared with the premenopausal subjects, reflecting a 33% increase in activation frequency. (5) BSAP, but not OC, was increased relatively more (66%) than the bone formation rate (BFR). Consequently, BSAP is more sensitive to the effects of menopause than OC, but OC is more sensitive to the effects of ethnicity than BSAP. (6) There were highly significant differences between the three subdivisions of the endosteal envelope for every non-cell-related variable. All Class 1 formation variables were highest on the endocortical surface, but the magnitude and pattern of the differences otherwise was inconsistent between variables. The contributions of the different subdivisions to the total bone formation rate were cancellous 54%, endocortical 13%, and intracortical 33%. (7) The previously reported changes in bone surface location, together with the presently reported changes in activation frequency and wall thickness indicated that there was no significant effect of age/menopause on erosion depth on the cancellous and intracortical surfaces but a large increase in erosion depth on the endocortical surface. (8) The increase in bone turnover that results from hormonal changes is most likely in the stochastic rather than in the directed component because it serves no purpose but has harmful effects on skeletal integrity. (J Bone Miner Res 1997;12:498-508)

The Effects of Trabecular-Bone Loading Variables on the Surface Signaling Potential for Bone Remodeling and Adaptation

“…Additionally, the loss/gain of bone mass in response to 50% reduced, respectively increased loads, both relative to the homeostatic morphology. Data from literature 15 (Table 2). Simulations using SED and its gradient had the lowest (COV).…”

Analysis of bone architecture sensitivity for changes in mechanical loading, cellular activity, mechanotransduction, and tissue properties

“…μ, k thr , τ , and F res , could not be derived from literature. Their values were chosen such that an equilibrium bone turnover rate of approximately 17% per year was obtained, in agreement with literature data (Han et al 1997). …”

Molecular and cellular mechanisms of the anabolic effect of intermittent PTH

“…If the duration of this morphologic feature of apoptosis is similar in the two species, the proportion of apoptotic osteoblasts in human bone would be 1 in 1800. The average bone formation rate in mice is about 55 μm 2 /μm/y [31] and the corresponding value in humans is about 14 μm 2 /μm/y [35]. If the relationship between osteoblast number and bone formation rate is similar in the two species, the probability of seeing an apoptotic osteoblast in a histologic section is about 50 times smaller for human than for murine bone.…”