Bone mineral density and metabolism at an early stage of menopause when estrogen and calcium supplement are not used and without the interference of major confounding variables.

OBJECTIVES: To measure bone mineral density (BMD) and to screen for early biochemical abnormalities in bone mineral metabolism in the first five years of natural menopause when estrogen and calcium supplement are not used and in the absence of major confounding variables. SETTING: Two homogeneous and comparable groups (n = 30) of healthy pre- and postmenopausal Caucasian women living in a northern region (latitude 46 degrees N) were recruited during the mid-Spring/Summer season in a cross-sectional design. METHODS: Volumetric apparent BMAD (g/cm(3)) was calculated from areal BMD (g/cm(2)) which was evaluated by dual energy X-ray absorptiometry (Lunar) at both axial and peripheric (femur) sites using two sets of reference values (WHO criterion expressed as T-score and absolute values of areal density) in combination to bone specific biochemical measurements. RESULTS: BMD and BM(A)D were significantly lower in postmenopausal women for all lumbar sites, but not for Ward's triangle and any other femoral sites whereas free deoxypyridinoline (Dpd), urinary biochemical marker of bone resorption, was markedly (p < 0.0001) greater. Their serum calcium and phosphate were significantly higher without a difference in 1,25(OH)(2)D(3) and PTH. The prevalence of osteopenia in pre- and postmenopausal women was about 2-fold lower in both groups (26.6 and 46.9%, respectively) when lumbar (L) spine and femur neck were combined and using the criteria based on reference values of areal density instead of T-scores. CONCLUSIONS: The present study showed that the negative effects of estrogen deficiency on BMD and bone metabolism in early menopause occurred independently of the effect of major calcitropic hormones. Bone loss affects a non negligible proportion of premenopausal women. The prevalence of osteopenia in pre- and postmenopausal women varied according to the criterion used and anatomic site.

Chemical and biomechanical characterization of hyperhomocysteinemic bone disease in an animal model.

BACKGROUND: Classical homocystinuria is an autosomal recessive disorder caused by cystathionine beta-synthase (CBS) deficiency and characterized by distinctive alterations of bone growth and skeletal development. Skeletal changes include a reduction in bone density, making it a potentially attractive model for the study of idiopathic osteoporosis. METHODS: To investigate this aspect of hyperhomocysteinemia, we supplemented developing chicks (n = 8) with 0.6% dl-homocysteine (hCySH) for the first 8 weeks of life in comparison to controls (n = 10), and studied biochemical, biomechanical and morphologic effects of this nutritional intervention. RESULTS: hCySH-fed animals grew faster and had longer tibiae at the end of the study. Plasma levels of hCySH, methionine, cystathionine, and inorganic sulfate were higher, but calcium, phosphate, and other indices of osteoblast metabolism were not different. Radiographs of the lower limbs showed generalized osteopenia and accelerated epiphyseal ossification with distinct metaphyseal and suprametaphyseal lucencies similar to those found in human homocystinurics. Although biomechanical testing of the tibiae, including maximal load to failure and bone stiffness, indicated stronger bone, strength was proportional to the increased length and cortical thickness in the hCySH-supplemented group. Bone ash weights and IR-spectroscopy of cortical bone showed no difference in mineral content, but there were higher Ca2+/PO4(3-) and lower Ca2+/CO3(2-) molar ratios than in controls. Mineral crystallization was unchanged. CONCLUSION: In this chick model, hyperhomocysteinemia causes greater radial and longitudinal bone growth, despite normal indices of bone formation. Although there is also evidence for an abnormal matrix and altered bone composition, our finding of normal biomechanical bone strength, once corrected for altered morphometry, suggests that any increase in the risk of long bone fracture in human hyperhomocysteinemic disease is small. We also conclude that the hCySH-supplemented chick is a promising model for study of the connective tissue abnormalities associated with homocystinuria and an important alternative model to the CBS knock-out mouse.

Articular cartilage calcification and matrix vesicles.

There has been much research in calcium-containing crystal deposition diseases of hereditary and sporadic type. Synovial cell-induced inflammation and secondary cartilage damage are common in these diseases. In most cases of these diseases and in primary osteoarthritis, there are mineral deposits in the cartilage, mineral crystals in the synovial fluid, and aberrations of pyrophosphate metabolism.

Inhibition of insulin-like growth factor binding protein 5 proteolysis in articular cartilage and joint fluid results in enhanced concentrations of insulin-like growth factor 1 and is associated with improved osteoarthritis.

OBJECTIVE: The complement component C1s is present in dog joint fluid in an activated state. Since C1s degrades insulin-like growth factor binding protein 5 (IGFBP-5), we undertook to determine whether inhibiting C1s in joint fluid would result in an increase in the amount of intact IGFBP-5 and IGF-1 in cartilage and joint fluid, and whether C1s inhibition would be associated with a reduction in cartilage destruction during the development of osteoarthritis (OA). METHODS: Twenty-two dogs were randomized to 3 treatment groups. All dogs underwent anterior cruciate ligament transection and were exercised. Dogs received 1 of 3 treatments: buffer alone (controls; n = 6); PB-145, a peptide derived from the sequence of antithrombin III (n = 9); and pentosan polysulfate (PPS; n = 7). PB-145 or saline was injected into the joint space 3 times per week for 3 weeks. PPS was injected intramuscularly weekly for 3 weeks. RESULTS: Joint histology showed preservation of chondrocytes and a smooth joint surface in the animals treated with PB-145 and PPS. Mankin scoring showed statistically significant reductions in joint destruction with PB-145 and PPS treatments (P < 0.01) compared with buffer control. Mean active collagenase concentrations were decreased by these two treatments. Immunoblotting of joint fluid showed that both treatments increased concentrations of intact IGFBP-5. Direct analysis of IGFBP-3 and IGFBP-5 protease activity showed that IGFBP-5 was degraded more rapidly and that PB-145 and PPS inhibited the degradation of both proteins. Total IGF-1 concentrations in joint fluid were increased 5.6-5.8-fold by these two treatments. Analysis showed that C1s was being activated in joint fluid and that its activation was inhibited by the addition of PB-145 or PPS. CONCLUSION: The findings suggest that direct inhibition of the serine protease C1s results in increased concentrations of intact IGFBP-5 and that proteolysis of IGFBP-3 is also inhibited, probably by the inhibition of some other protease. This increase in concentrations of intact IGFBP-3 and IGFBP-5 leads to an increase in IGF-1 which is associated with an improvement in joint architecture during the development of OA.

Altered swelling behavior of femoral cartilage following joint immobilization in a canine model.

Periods of reduced joint loading have been shown to induce changes in the biochemical composition. metabolism and mechanics of articular cartilage. In this study, changes in cartilage swelling behavior were studied following a 4-week period of joint immobilization, using a recently developed osmotic loading technique [J. Biomech, 32 (1999) 401-408]. The magnitude and distribution of swelling strains were measured in cartilage-bone samples equilibrated in physiological and hypotonic saline, relative to a hypertonic reference NaCl solution. Physicochemical parameters (glycosaminoglycan fixed charge density and water volume fraction) were determined in site-matched cartilage samples. The experimental data for swelling strains, fixed charge density and water volume fraction were used with a triphasic mechano-chemical theory [J. Biomech. Eng. 113 (1991) 245-258] to determine the effect of joint immobilization on the tensile modulus of the cartilage solid matrix. Four weeks of immobilization resulted in a significant increase in the magnitude of swelling-induced strains, and a significant decrease in fixed charge density in cartilage, as compared with the contralateral controls. Joint immobilization also resulted in decreases in values for the modulus of cartilage, as compared with the contralateral controls. Our results suggest that 4 weeks of joint immobilization had a significant effect on cartilage mechanical function that may be linked to collagen changes in the cartilage extracellular matrix.