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PubMedDate not supplied

[In vitro availability of minerals in infant foods with different protein source].

As the result of the digestion process, it is produced at gastrointestinal level interactions between proteins-minerals and minerals-minerals that might modify the bioavailability of the nutrients initially designed for an adequate nutrition in infant formulas. The aim of the present study is to compare the in vitro availability of some minerals and trace elements (calcium, phosphorus, magnesium, iron and zinc) in infant formulas of initiation elaborated with different protein sources: formulas based on cow milk protein (whey-casein) versus vegetal protein (soy-based infant formulas). Also, for evaluating the effects of the different mineral supplementation in the availability of minerals, it was used infant formulas from two different manufacturers. Milk-protein based infant formulas showed for both manufacturers higher dialysis percentage (%) of phosphorus and zinc than the soy-protein based formulas. The availability of iron in the soy formula of the manufacturer A lowered significantly (P < 0.05) respect to the whey-casein based formula (9.6 +/- 2.3 versus 4.6 +/- 0.8), but not respect to the whey-casein formula of manufacturer B (9.6 +/- 1.1 versus 9.0 +/- 0.7), which might be due to the lowest proportion of phytic acid in this last commercial formula. Dialysability of all the minerals analysed from soy-protein based formulas showed significant differences depending on the manufacturer. The purification processes of the soy protein have a high repercussion in the mineral availability of soy-based infant formulas. It could be more interesting to use soy proteins more purified, with low level of phytic acid, in the elaboration of soy infants formulas, than the supplementation them with high amounts of minerals.

Dietary Proteins↗
PubMed1985

Ultrastructural modifications of proteoglycans coincident with mineralization in local regions of rat growth plate.

We carried out histochemical and electron-microscopic studies to examine the relationship between mineral deposition and changes in the organization of proteoglycans during mineralization in the cartilaginous growth plate of the rat. To preserve the distribution and organization of proteoglycans in the extracellular matrix and to stain proteoglycans, acridine orange was included in the solutions that were used for fixation and demineralization. In undecalcified sections, mineral crystals that initially appeared at the level of the penultimate hypertrophic chondrocyte grew into dense, spherical mineral clusters, roughly one micrometer in diameter, in the longitudinal septa of the lowermost hypertrophic zone. Following the removal of mineral with EDTA in the presence of acridine orange, proteoglycan structures with a characteristic rosette-like architecture were revealed within the matrix of the longitudinal septa of the lower hypertrophic zone. The location of these rosette-like proteoglycan structures was identical to that of the dense, spherical mineral clusters in the undemineralized controls, and they were remarkably similar in morphology and size. In the electron micrographs stained with uranyl acetate and lead citrate, the greatly increased density of the rosette-like structures and large diameter of the proteoglycan structures located in mineral clusters contrasted sharply with the slender strands of more faintly stained proteoglycan that was diffusely distributed throughout most of the extracellular matrix. X-ray microprobe analysis for sulphur confirmed the existence of proteoglycans in the rosette-like structures and demonstrated that the concentration of proteoglycans was selectively increased in these regions. The cores of the metaphyseal calcified cartilage also exhibited rosette-like proteoglycan structures, which before demineralization were totally obscured by the diffuse, dense homogeneous deposition of mineral. Without stabilization of the proteoglycans in the extracellular matrix with acridine orange, the rosette-like proteoglycan structures could not be demonstrated. These results clearly indicate that there is a selective increase in the concentration of proteoglycans in exactly the same regions where mineral clusters are formed in the hypertrophic zone of the cartilaginous growth plate.

Acridine Orange↗
PubMed1982

Mineralization of human aortas with coarctation: quantitative electron probe microanalysis.

Aortas with coarctation (isthmus stenosis) are obviously an ideal model to investigate pressure dependent changes of the aorta, as one can compare the proximal region (high pressure) with the distal region (low pressure). 7 aortas of patients aged from 2 months to 54 years were investigated. The concentrations of Na, Mg, P, S, C1, K, and Ca were determined by electronprobe microanalysis. Ca and P are constituent parts of the developing mineral and are mainly discussed. The Ca/P ratio (by weight) is about 0.3 in the unmineralized and about 2 in the mineralized tissue. Mineralization is demonstrated by a parallel increase of Ca, P, and the Ca/P ratio. Enrichments of Ca and P are found above all in a subintimal band. Usually they occur proximally and distally, but are much more pronounced proximally. Even in the aorta of a 2 month old infant enrichments were found proximally, but not distally. Thus mineral deposits occur very early in regions of hypertension. The differences between the proximal and distal region may demonstrate the influence of blood pressure on vascular mineralization. The mineralization starts in small compartments, which increase in size and number in the process of mineralization. Mineralized regions could often be localized by cathodoluminescence. But to demonstrate and localize the initial mineral deposits and to quantify element contents, electronprobe microanalysis became indispensable.

Adolescent↗
PubMed1992

Bone mineral density in 15- to 21-year-old eumenorrheic and amenorrheic subjects.

The purposes of this study were to compare the lumbar spine bone mineral density of eumenorrheic and amenorrheic white subjects aged 15 to 21 years, and to describe the femoral neck bone mineral density in the eumenorrheic subjects. Twenty-eight eumenorrheic females had lumbar bone mineral density (mean +/- SD) of 1.213 +/- 0.117 g/cm2, and femoral neck bone mineral density of 1.032 +/- 0.092 g/cm2 measured with dual energy x-ray absorptiometry. Bone mineral density at neither site was related to age, energy intake, or calcium intake. Femoral neck bone mineral density was related to energy expenditure. Body composition was measured with total body electrical conductivity, and bone mineral density at both sites was related to body weight as much as fat-free mass. Eight amenorrheic subjects had a lumbar spine bone mineral density of 1.057 +/- 0.113 g/cm2, which was lower than in the eumenorrheic group. However, when controlling for weight, this difference was not significant. Peak lumbar and femoral neck bone mineral density may be reached at midadolescence.

Absorptiometry, Photon↗
PubMed1992

Bone mineral metabolism in full-term infants fed human milk, cow milk-based, and soy-based formulas.

OBJECTIVE: To study the hypothesis that ingestion of a modified soy-based formula with an improved mineral suspension system may result in bone mineral content similar to that observed in infants fed human milk or cow milk-based formulas. DESIGN: Prospective, self-selected group of infants fed human milk randomized between the two formula-fed groups. SETTING: University-based hospital nursery and follow-up. PARTICIPANTS: Fifty-six normal, healthy, full-term infants, free of major malformations or disorders, including 17 infants fed human milk, 19 infants fed a cow milk-based formula, and 20 infants fed a soy protein formula were followed up to 6 months' postnatal age. The soy-based formula studied was modified to improve the suspendability of the minerals. INTERVENTIONS: Infants were fed human milk or the study formula for the first 4 months, at which time beikost was permitted. Infants fed human milk received vitamin supplementation to provide 400 IU of vitamin D per day. MEASUREMENTS: Anthropometric variables, serum calcium, magnesium, phosphorus, alkaline phosphatase, and parathyroid hormone levels were measured at enrollment, and at 8, 16, and 24 to 26 weeks' postnatal age. Bone mineral content at the distal third radius site was measured with single photon absorptiometry at these times. Growth in the infants did not differ significantly among the groups. There was no significant difference in serum calcium, magnesium, alkaline phosphatase, or parathyroid hormone concentrations among the infants during the study. Serum phosphorus was significantly lower at 8 weeks in the group fed human milk than in that fed the cow milk-based formula. Bone mineral content at 16 and 24 to 26 weeks was higher in the group fed the soy-based formula than in that fed human milk, and bone width was also higher at 16 weeks in the infants fed the soy-based formula. CONCLUSIONS: Improving the suspendability of the mineral system in the soy formula results in bone mineralization in infants fed the soy-based formula similar to that measured in infants fed human milk and cow milk-based formula. We suggest that the suspendability of the minerals used is an important variable in the interpretation of the effect of feedings on the bone mineral status of infants.

Animals↗
PubMed1991

A contribution with review to the description of mineralization of bone and other calcified tissues in vivo.

This manuscript considers certain aspects of mineral deposition in bone and other vertebrate calcifying tissues in order to examine physical, chemical, and biological factors important in the mineralization process. The paper in a discussion format principally presents a new data and the formulation of concepts based on such data as well as a summary of background material as necessary review. Mineralization is found to occur at spatially independent sites throughout the organic extracellular tissue matrices. Matrix vesicles and collagen fibrils each may serve as independent nucleation centers for mineral with vesicle mineralization being local and collagen mineralization dominating the tissues as a whole. Collagen fibril organization is suggested to be such that hole zones are aligned in three dimensions, creating extensive channels for mineral accommodation. Nucleation occurs initially in hole zones and crystal growth leads to the development of plate-like mineral particles whose orientation, disposition, and sizes within fibrils are detailed. Effects of diffusion, crystallinity, and critical nucleation and growth events are described with respect to their influence on mineral deposition in bulk and local regions of tissue matrices.

Animals↗
PubMed1993

Bone mineral density and mass in a cross-sectional study of white and Asian women.

The literature suggests that Asians have lower bone mineral density and mass than whites. It has been proposed that these differences may be due to differences in height, weight, and factors other than ethnicity, but no study has made the appropriate direct comparisons. We compared total-body bone mineral density and mass between Asian and white women while controlling for factors known to be associated with bone mineral density and mass. Measurements were made in 129 Asian (primarily of Chinese ancestry) and 274 white women. A subgroup was formed of women who did not have a history of alcoholism, premenopausal amenorrhea, kidney disease, estrogen use, birth control pill use, thyroid disease, steroid use, hysterectomy, or smoking. In both the main group and the subgroups, bone mineral mass was significantly lower in Asian than in white women, but after analysis of covariance with body weight, height, and age (or years since menopause) as covariates, the differences between ethnic groups disappeared, except in the large group of premenopausal women, in whom average bone mineral density in Asians actually exceeded (p < 0.04) that in whites. The data set was also searched for Asian-white pairs who matched on 17 characteristics related to bone mineral density and mass. In the resulting 16 matched pairs, bone mineral density and mass were not different between ethnic groups. Although Asian women have lower bone mineral mass than white women, when weight, height, and other factors are controlled, bone mineral density and mass do not differ between Asian and white women.

Absorptiometry, Photon↗
PubMed1995

Mineralization of alkaline phosphatase-complexed collagen implants in the rat in relation to serum inorganic phosphate.

The present study was designed to determine the relationship between mineralization of collagenous matrices and serum levels of calcium and inorganic phosphate. Collagen slices were prepared from bovine dentin or cortical bone and complexed with varying amounts of intestinal alkaline phosphatase (ALP). The enzyme was added to induce de novo mineralization. The ALP-complexed slices were implanted subcutaneously over the skull and in the dorsolateral aspect of the abdominal wall in female Wistar rats of various ages (5-, 10-, 20-, or 35-week-old) and in young male rats fed on a low-P diet. After 1-4 weeks, the implants were removed and analyzed for calcium and phosphate content. In addition, serum levels of calcium and phosphate (total and inorganic) were determined. It was shown that the highest mineral influx occurred in the younger rats (which were also highest in serum P(i)), whereas almost no mineral uptake occurred in the older ones. Also in rats fed on a low-P diet (which were low in serum P(i), a strongly decreased mineral influx was noted. In all animal groups a positive correlation was found between the degree of mineralization and serum P(i). No distinct relationship was found between serum Ca/organic phosphate levels and mineral influx in the implants. In vitro incubation of ALP-collagen conjugates in serum from younger and older rats confirmed our view that serum P(i), besides local levels of ALP, is important in de novo mineral deposition. For accretion of mineral in partially remineralized collagenous carriers, ALP activity was not required.

Aging↗
PubMed1993

Studies of the levamisole inhibitory effect on rat stromal-cell commitment to mineralization.

The ability of Levamisole to decrease mineralization in skeletal tissue is usually related to its effect on alkaline phosphatase (ALP). However, Levamisole is also suspected to diminish mineralization by an additional mechanism which is unrelated to the ALP control of apatite crystal growth. To delineate the time in differentiation during which Levamisole inhibits mineralization, a tissue culture model system of bone marrow stromal cells was used. Secondary cultures of stromal cells were propagated in osteoprogenitor cell (OPC) induction medium for three weeks, followed by measurement of calcium precipitation. In situ ALP assays at pH 7.6 were also performed. When cells were cultured with 0.2 mM Levamisole for three weeks, Day 20 values of calcium precipitates were lower than in controls, but Day 20 ALP values were paradoxically higher. The correlation between calcium and ALP within each group was low. The correlation slightly improved, in uninhibited cultures, when Day 21 calcium values were matched with earlier Day 12 ALP values. This suggested the existence of a Levamisole-sensitive mechanism for mineralization inhibition effective prior to the culture's mineralization stage. To focus on this early effect on mineralization Levamisole was added to stromal cultures on different days and removed on Day 12. Levamisole decreased Day 21 mineralization when added on Days 0, 3, 5, and 7, but not when added on Day 9. The Levamisole-induced inhibition of mineralization was accompanied by an increase in Day 12 ALP specific activity, compared to controls, when added from Day 5 and thereafter. The results indicate that part of the ability of stromal cells to mineralize is determined during the first week of culture.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1994

Adenosine 5'-triphosphate promotes mineralization in differentiating chick limb-bud mesenchymal cell cultures.

When chick limb-bud mesenchymal cells are plated in micromass culture, they differentiate to form a mineralizable cartilage matrix. Previous studies have demonstrated that, when the total inorganic phosphate concentration of the medium is adjusted to 3-4 mM by adding inorganic phosphate to the basal medium, the mineralized matrix formed resembles that of chick calcified cartilage in ovo. When the high-energy phosphates adenosine 5'-triphosphate (ATP) or creatine phosphate are used as supplements in place of inorganic phosphate, the mineralized matrix as analyzed by electron microscopy and Fourier transform infrared microscopy is also similar to that in ovo. This is in marked contrast to the mineralized matrix formed in the presence of 2.5-5 mM beta-glycerophosphate, where mineral deposition is random and mineral crystal sizes in general are larger. This is also in contrast to the known ability of ATP to inhibit mineral deposition in solution in the absence of cells. In the differentiating mesenchymal cell culture system, ATP does not alter the rate of cell proliferation (DNA content), the rate of matrix synthesis (3H-leucine uptake), the mean crystallite length, or the rate of mineral deposition (45Ca uptake) when contrasted with cultures supplemented with inorganic phosphate. However, ATP does increase the mineral to matrix ratio, especially around the edge of the culture, where a type I collagen matrix is presented. It is suggested that ATP promotes mineral deposition by providing a high-energy phosphate source, which may be used to phosphorylate extracellular matrix proteins and to regulate calcium flux through cell membranes.

Adenosine Triphosphate↗
PubMed1976

Electron microscopic microprobe analysis of mineralized collagen fibrils and extracollagenous regions in turkey leg tendon.

Bundles of tibia tendon from 19 week-old turkeys were deep frozen, freeze dried and embedded in styrol methacrylate or Epon. In the distal mineralized region, bundles of unmineralized collagen fibrils as well as mineralized regions consisting of round microcompartments with low contrast surrounded by a mineral sheath with high contrast were found. The inner regions with low contrast corresponded to the mineralized collagen fibrils, while the contrast-rich peripheral zones corresponded to the mineralized collagen-free "ground substance". Using electron microscopic microprobe analysis, it was shown that the peripheral mineralized region, consisting mainly of closely packed needles, often contained 100% more mineral substance than the central, mineralized collagen zone, which consisted mainly of plate-like crystallites. Possible reasons for this difference in mineral content are discussed on the molecular level.

Animals↗
PubMed2002

Association of polymorphisms of the estrogen receptor alpha gene with bone mineral density of the femoral neck in elderly Japanese women.

The estrogen receptor alpha gene is a candidate locus for genetic influence on bone mass. The possible association between two polymorphisms in the first intron of this gene, alone or in combination, and bone mineral density at various sites was examined in participants in the National Institute for Longevity Sciences Longitudinal Study of Aging, a population-based prospective cohort study of aging and age-related diseases. The relationship of the TC ( PvuII) and AG ( XbaI) polymorphisms in the first intron of the estrogen receptor alpha gene to bone mineral density was determined in 2230 subjects (1120 men, 1110 women) and in 2238 subjects (1128 men, 1110 women), respectively, all of whom were community-dwelling individuals aged 40-79 years. Bone mineral density at the radius was measured by peripheral quantitative computed tomography and that for the lumbar spine, right femoral neck, right trochanter, right Ward's triangle, and total body was measured by dual-energy X-ray absorptiometry. Estrogen receptor alpha genotypes were determined with an automated fluorescent allele-specific DNA primer assay system. Analysis of the TC ( PvuII) polymorphism revealed that bone mineral density for the total body, femoral neck, and trochanter was significantly lower in women aged 60 years or over with the CC genotype than in those with the TT genotype, but statistical significance was not achieved after adjustment for age, body mass index, and smoking status. Analysis of the AG ( XbaI) polymorphism revealed that bone mineral density for the femoral neck was significantly lower in women aged 60 years or over with the GG genotype than in those with the AA genotype. After adjustment for age, body mass index, and smoking status, bone mineral density for the femoral neck was significantly lower in women aged 60 years or over with the GG genotype than in those with the AA or AG genotypes. Analysis of combined genotypes in women aged 60 years or over revealed that bone mineral density for the femoral neck was significantly lower in women with the CC/ GG genotype than in those with the TT/ AA or TC/ AA genotypes. After adjustment for age, body mass index, and smoking status, bone mineral density for the femoral neck was significantly lower in women aged 60 years or over with the CC/ GG genotype than in those with other genotypes. No differences in bone mineral density at the various sites were detected among TC ( PvuII), AG ( XbaI), or combined genotypes in women aged under 60 years or in men. These results suggest that the estrogen receptor alpha gene is a susceptibility locus for bone mass, especially for the femoral neck, in elderly Japanese women.

Absorptiometry, Photon↗
PubMed2003

Bone mineral density and bone metabolism in Duchenne muscular dystrophy.

Very few studies on bone mineral density and bone metabolism in Duchenne muscular dystrophy (DMD) have been reported. DMD is a severe, progressive muscular disease resulting in death at a young age. No specific therapies are available, but corticosteroids induce improvement and slower progression of the disease. However, long-term steroid therapy is a serious risk factor for osteoporosis. This study was aimed at evaluating bone mineral density and calciotropic hormones in a group of children affected by DMD, with or without steroid therapy. Bone mineral density was measured by DXA scan on lumbar spine and total body. Evaluation of calcium, phosphorus, bone turnover markers and calciotropic hormones was performed. Thirty-two children affected by DMD were studied: twenty-two on long-term prednisone therapy, ten not taking corticosteroids. Bone mineral density was lower than normal for age in all patients, and even lower in the group of steroid-treated children. Trunk and lower limb bone mineral densities were more reduced than upper limb mineral density, especially in the steroid-treated subjects. A marked reduction in spine bone mineral density, hypocalciuria, low 25-hydroxyvitamin D levels, and increased bone turnover markers were observed, and even these especially in the steroid-treated group. In conclusion, decreased bone mineral density and derangement of calcium metabolism were present in DMD patients, and were worsening during corticosteroid therapy. It is thus recommended that bone and mineral metabolism be carefully evaluated in patients with DMD, so that appropriate measures could be taken, especially now that chronic corticosteroid therapy is frequently given.

25-Hydroxyvitamin D 2↗
PubMed2005

Association of COLIA1 Sp1 alleles with defective bone nodule formation in vitro and abnormal bone mineralization in vivo.

Previous work identified a G/T polymorphism affecting a Sp1 binding site in a regulatory region of the COLIA1 gene that predisposes to osteoporotic fractures by affecting bone strength through mechanisms that are partly independent of differences in bone mineral density (BMD). To clarify the mechanisms by which COLIA1 Sp1 alleles influence bone strength we used quantitative backscattered electron imaging (qBEI) to characterize bone mineralization in biopsy samples from subjects of different COLIA1 genotype and studied the ability of osteoblast-like cells cultured from subjects of different genotypes to form mineralized bone nodules. The qBEI analysis showed a significant (P = 0.014) reduction in mineralization in bone biopsies from G/T heterozygotes (n = 6) compared with G/G homozygotes (n = 7) and a significant increase in heterogeneity of mineralization (P = 0.017). The in vitro studies showed that osteoblasts derived from G/T heterozygotes (n = 5) were significantly less able to produce mineralized bone nodules than G/G homozygotes (n = 10) at all time-points examined (P < 0.0001). We conclude that carriage of the COLIA1 Sp1 "T" allele is associated with an impaired ability of osteoblast-like cells to form mineralized bone nodules in vitro and with abnormalities of bone mineralization in vivo. This suggests that the increased bone fragility in carriers of the COLIA1 Sp1 allele may result in part from defects in bone mineralization.

Aged↗
PubMed2004

Regulation of mineral-to-matrix ratio of lumbar trabecular bone in ovariectomized rats treated with risedronate in combination with or without vitamin K2.

The relationship between bone turnover and bone tissue and material properties was examined in ovariectomized (OVX) rats treated with risedronate in combination with or without vitamin K2. Seventy female rats, 18 weeks of age, were assigned to 7 groups (n=10): sham-operated + vehicle control; OVX + vehicle control; OVX + risedronate 0.1, 0.5, or 2.5 mg/kg/day po; OVX + vitamin K2 approximately 30 mg/kg/day po; OVX + vitamin K2 (approximately 30 mg/kg/day) and risedronate (0.5 mg/kg/day). Treatments were given daily for 9 months. To assess bone turnover, we measured serum osteocalcin and urinary deoxypyridinoline at 0, 3, and 9 months. To assess vertebral and femoral tissue and material properties, bone mass, bone mineral density (BMD by DXA), trabecular bone structure (vertebra: 3D-microCT), cortical bone structure (femur: histomorphometry), biomechanical properties, and mineral properties (mineral-to-matrix and carbonate-to-phosphate ratios by Fourier transform infrared microspectroscopy) were measured ex vivo at 9 months. Ovariectomy increased bone turnover and induced significant loss of bone mass/density, structure, mineral properties (mineral-to-matrix ratio), and strength. Risedronate produced dose-dependent inhibition of the ovariectomy-induced increase in turnover and loss of bone mass/density, structure, mineral-to-matrix ratio, and strength, with a lowest effective dose of 0.1-0.5 mg/kg/day. High-dose risedronate (2.5 mg/kg/day) did not induce increases in any parameter above that of sham control. Vitamin K2 had no effects. In the OVX groups, urinary deoxypyridinoline at 3 and 9 months correlated significantly with vertebral BMD, trabecular bone volume, ultimate load, stiffness, and mineral-to-matrix ratio, and with femoral BMD, cortical area, and ultimate load. These results support the concept that changes in bone tissue and material properties can result directly from changes in bone turnover. Different effects among different drugs on material properties, including mineral-to-matrix ratio, may reflect differences in the relative rate and magnitude of osteoclastic bone resorption and osteoblastic primary bone mineralization.

Absorptiometry, Photon↗
PubMed1994

Determinants of total-body and regional bone mineral content and density in postpubertal normal women.

Some investigators consider body fat the main determinant of bone mass in women, and others, weight. Although genetics may be the primary determinant of peak bone mass, modifiable secondary factors such as nutrition and hormone exposure may significantly affect bone mass accretion during the second decade of life. To determine the principal determinants of bone mass, we analyzed total and regional bone mass (by dual-energy x-ray absorptiometry), weight, height, percentage body fat, and lean body mass in a group of 50 young women ranging in age from 14 to 18 years. Total-body bone mineral content, total-body bone mineral density, and total-body bone mineral density corrected for height, analyzed by multiple correlation, were not related to percentage body fat, although percentage body fat did correlate with the regional bone mineral content of the trunk (P < .001), legs (P < .01), and pelvis (P < .001). Lean body mass correlated with total-body bone mineral content and density, total-body bone mineral density corrected for height (P < .001), and regional bone mineral content of the trunk (P < .05), arms (P < .01), and legs (P < .001), but not with regional bone mineral content of the pelvis and head. Weight correlated significantly (P < .001) with all bone mass measurements except regional bone mineral content of the head, where the significance was P less than .05. Similar results were obtained by multiple regression analysis. These results indicate that weight, not body fat, is the main determinant of bone mass in postpubertal women.

Absorptiometry, Photon↗
PubMed1991

Stimulation by 1,25-dihydroxyvitamin D3 of in vitro mineralization induced by osteoblast-like MC3T3-E1 cells.

Although vitamin D is essential for mineralization of bone, it is as yet unclear whether vitamin D has a direct stimulatory effect on the bone mineralization process. In the present study, the effect of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] on in vitro mineralization mediated by osteoblast-like MC3T3-E1 cells was examined. MC3T3-E1 cells continued to grow after they reached confluency, and DNA content and alkaline phosphatase activity increased linearly until about 16 days of culture, whereas 45Ca accumulation into cell and matrix layer remained low. After this period, DNA content plateaued, and 45Ca accumulation increased sharply. Histological examination by von Kossa staining revealed that calcium was accumulated into extracellular matrix. In addition, needle-shaped mineral crystals similar to hydroxyapatite crystals could be demonstrated in between collagen fibrils by electron microscopy. Thus, MC3T3-E1 cells differentiate in vitro into cells with osteoblastic phenotype and exhibit mineralization. When MC3T3-E1 cells were treated with 1,25(OH)2D3 at this stage of culture, there was a dose-dependent stimulation of 45Ca accumulation by 1,25(OH)2D3, and a significant stimulation of 45Ca accumulation was observed with 3 x 10(-10) M 1,25(OH)2D3. Although 1,25(OH)2D3 enhanced alkaline phosphatase activity and collagen synthesis at the early phase of culture, it did not affect any of these parameters at the late phase when 1,25(OH)2D3 stimulated mineralization. Neither 24,25-dihydroxyvitamin D3 nor human PTH(1-34) affected mineralization in the presence or absence of 1,25(OH)2D3. These results demonstrate that 1,25(OH)2D3 stimulates matrix mineralization induced by osteoblastic MC3T3-E1 cells, and are consistent with the possibility that 1,25(OH)2D3 has a direct stimulatory effect on bone mineralization process.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed2003

Tissue mineralization is increased following 1-year treatment with high doses of bisphosphonates in dogs.

Suppression of bone turnover using anti-resorptive agents such as bisphosphonates prevents bone loss but also may increase tissue mineralization. This may make the bone more prone to initiate microcracks. The objective of this study was to determine whether suppression of remodeling caused by treatment of dogs for 1 year with five times the clinical dose of either alendronate or risedronate is associated with increased tissue mineralization and whether it changes the nature of the mineral crystal. Thirty-five dogs were divided into three weight-matched groups and treated daily for 1 year with a subcutaneous injection of saline (CON, n = 12), oral risedronate (RIS, 0.5 mg/kg/day, n = 11), or oral alendronate (ALN, 1.0 mg/kg/day, n = 12). Density fractionation, peripheral quantitative computerized tomography (pQCT), and quantitative backscattered electron microscopy (qBSE) were used to evaluate changes in mineral content of bone tissue from the vertebrae or ribs. Infrared microspectroscopy (IR) and X-ray diffraction were used to assess the quality of the mineral and some aspects of collagen structure in the thoracic vertebrae and iliac crest. Following 12 months of treatment, there was a significant shift toward higher density bone in both ALN (P = 0.04) and RIS (P = 0.002) by density fractionation methods. IR, pQCT, and qBSE did not detect any significant differences in mineralization, probably because of their lower sensitivity and/or because of the smaller region of interest they sample. No significant differences were found in the maturity of the mineral crystals or in their length or size. We conclude that treatment for 1 year with high doses of bisphosphonates which suppress bone remodeling up to 90% increases tissue mineralization, but does not change the nature of the mineral crystal.

Alendronate↗