Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.3.1 (alkaline phosphatase)
47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Estrogen responsiveness of bone is a fundamental regulatory mechanism operative in skeletal homeostasis. We examined the expression of estrogen receptor-alpha (ER) messenger RNA (mRNA) in cultured rat calvarial-derived osteoblasts during progressive development of the osteoblast phenotype. Levels of ER message were compared with the expression of traditional osteoblastic markers that have been mapped throughout the differentiation process of these cells. ER transcripts, measured using semiquantitative RT-PCR analysis, were expressed at low levels in early stage proliferating osteoblasts and increased at confluence upon initial expression of bone cell phenotypic genes. A 23-fold up-regulation of ER mRNA expression coincided with the initiation of alkaline phosphatase activity (day 8). ER mRNA levels progressively increased 70-fold, reaching a maximum level on days 22-25 in fully differentiated osteoblasts when osteocalcin expression peaked, but declined precipitously by day 32 in osteocytic cells. Analysis of RNA isolated directly from rat calvaria confirmed these in vitro results and demonstrated that ER message levels become more abundant postnatally as bone becomes more mineralized. We also examined the responsiveness of osteoblasts to 17beta-estradiol (17beta-E2) at two periods of maturation: the nodule-forming stage (day 14) and the late mineralization stage (day 30). Estradiol suppressed the levels of alkaline phosphatase, osteocalcin, osteonectin, and ER mRNAs on day 14, but up-regulated these messages on day 30. In contrast, 17beta-E2 treatment regulated the steady state levels of transforming growth factor-beta1 and type I procollagen mRNAs only in the late mineralization stage, whereas histone H4 message was unaffected by the steroid at either stage of differentiation. Thus, the observed developmental expression of ER mRNA correlates with progressive osteoblast differentiation and may be a contributing factor to differential regulation of bone cell gene expression by 17beta-E2.
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PMID:Estrogen receptor-alpha is developmentally regulated during osteoblast differentiation and contributes to selective responsiveness of gene expression. 952 93

The effects of pregnancy and lactation on bone histomorphometry have been studied extensively in rats and dogs. However, these models differ greatly in reproductive physiology compared with women. The purpose of this study was to evaluate histomorphometric changes in iliac crest bone biopsies taken from cynomolgus monkeys (Macaca fascicularis), animals similar to women both skeletally and reproductively. After fluorochrome labeling, paired iliac crest bone biopsies were collected and subjected to structural and dynamic histomorphometric analyses during the third trimester and 3 months postpartum in one group (n=16), at 3 and 9 months postpartum in the second group (n=14), and at 4 month intervals in a nonpregnant control group (n=6). Serum was collected at the time of surgery to measure total alkaline phosphatase (ALP), bone gla-protein (BGP), calcium, and estradiol. Trabecular thickness increased significantly between 3 and 9 months postpartum. Bone formation rates did not differ between control and pregnant monkeys, but were significantly increased during lactation (3 months postpartum) and remained elevated at 9 months postpartum. ALP and BGP levels were elevated at 3 months postpartum, compared with levels during pregnancy, and remained elevated at 9 months postpartum. Estradiol concentrations were greatly elevated during pregnancy, dropped below normal nonpregnant levels by 3 months postpartum, and remained suppressed at 9 months postpartum. These results suggest that, during the third trimester, the rate of bone turnover was not altered, but lactational demands for calcium were met in part by increased bone turnover.
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PMID:Effects of pregnancy and lactation on bone in cynomolgus macaques: histomorphometric analysis of iliac biopsies. 960 Jul 90

Previous studies have shown that treatment with estrogen or calcium decreases bone turnover in older women. The mechanisms by which estrogen and calcium exert their effects are probably different. We therefore examined the possibility of an additive or synergistic effect of combined treatment with calcium and low dose estrogen on bone turnover in older women, using biochemical markers. Thirty-one healthy women over 70 yr of age were randomized to 12 weeks of treatment with either micronized 17beta-estradiol [0.5 mg/day Estrace (E2)] or 1500 mg/day elemental calcium, given as carbonate plus vitamin D (800 IU/day; Ca+D). At the end of the initial 12-week treatment period, both groups received both Ca+D and E2 for an additional 12 weeks. Eleven older women were followed for 36 weeks without any treatment and served as a control group. Serum and urine were collected at baseline, at 12 and 24 weeks on treatment, and at 12 weeks after treatment was terminated for measurement of biochemical markers of bone turnover. Markers of bone formation were bone alkaline phosphatase, osteocalcin, and type I procollagen peptide; markers of bone resorption were urinary cross-linked C-telopeptides and N-telopeptides of type I collagen, serum cross-linked N-telopeptides of type I collagen, urinary free deoxypyridinoline cross-links, and serum bone sialoprotein. Repeated measures ANOVA was used to determine changes in bone turnover measures over time by group. All markers of bone resorption decreased with initial treatment and decreased further with combination therapy (P < 0.001). Markers of bone formation decreased with Ca+D treatment, but not with E2 alone; there was no additional effect of combination therapy on formation markers compared to Ca+D alone. Neither markers of formation nor resorption changed in the control group. These results suggest that there is an additive effect of low dose estrogen and calcium on bone resorption, but not on bone formation, in older women. Thus, the combination of low dose estrogen plus calcium is likely to be more effective in older women than either treatment alone.
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PMID:Low dose estrogen and calcium have an additive effect on bone resorption in older women. 992 80

A total of 277 early postmenopausal women were enrolled in this placebo-controlled 2-year study to examine the efficacy of a matrix transdermal 17beta-estradiol system, at three different dosages (25, 50 and 75 mg/day) combined with sequential oral dydrogesterone 20 mg/day, in preventing bone loss. At 2 years, the difference from placebo in percentage change from baseline of L1-4 lumbar spine bone mineral density (BMD) (assessed by dual-energy X-ray absorptiometry) was 4.7% +/- 0.7% with estradiol 25 mg/day, 7.3% +/- 0.7% with estradiol 50 mg/day and 8.7% +/- 0.7% with estradiol 75 mg/day (all values mean +/- SEM). There were also significant increases in femoral neck, trochanter and total hip BMD with all doses of estradiol compared with placebo. Additionally, most patients had a significant gain (increase greater than 2.08%) in lumbar spine bone mass compared with placebo. Patients who received estradiol also experienced clinically significant and dose-related decreases in total serum osteocalcin, serum bone alkaline phosphatase and urinary C-telopeptide, with all three markers of bone turnover returning to premenopausal levels. Estradiol was well tolerated during the 2-year treatment period. Transdermal estradiol is effective and well tolerated at dosages between 25-75 mg/day in the prevention of bone loss in postmenopausal women; 25 mg/day offers an effective option for those women who cannot tolerate higher doses.
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PMID:Matrix delivery transdermal 17beta-estradiol for the prevention of bone loss in postmenopausal women. The International Study Group. 1055 Apr 54

Oestradiol can stimulate osteoblast activity. Osteoblast function is thought to be regulated by nitric oxide (NO). We hypothesised that the effect of 17beta-oestradiol (17beta-E(2)) on osteoblast activity is mediated by NO. This hypothesis was tested using osteoblasts isolated from human trabecular bone, calvariae of rats, endothelial NO synthase (eNOS) gene-deficient mice, and their wild-type counterparts. Our results show that 17beta-E(2) dose-dependently stimulated proliferation and differentiation of primary human, rat and wild-typeosteoblasts. The presence of N(G)-monomethyl-l-arginine (10(-3) M), an inhibitor of NOS activity, blocked the 17beta-E(2)-(10(-7) M)-induced increases in thymidine incorporation (P < 0.01), alkaline phosphatase activity (P < 0.01) and bone nodule formation (P < 0.01) of wild-type, human and rat osteoblasts, respectively. Moreover, 17beta-E(2) did not induce a response in eNOS gene-deficient osteoblasts. 17beta-E(2) also increased total eNOS enzyme expression in rat osteoblasts. These findings indicate 17beta-E(2) modulates osteoblast function by NO-dependent mechanisms mediated via the eNOS isoform.
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PMID:Nitric oxide mediates 17beta-estradiol-stimulated human and rodent osteoblast proliferation and differentiation. 1106 1

Levormeloxifene, a nonsteroidal selective estrogen receptor modulator (SERM), has been evaluated for its effects on bone in cynomolgus monkeys (Macaca fascicularis). Adult female monkeys were imported from Indonesia and randomized into six groups of 25-28 animals each (n = 158). Animals in one group were sham ovariectomized (sham) and received vehicle. Animals in the remaining five groups were ovariectomized and received either vehicle (ovx); 17beta-estradiol at 0.016 mg/kg (est); or levormeloxifene at 0.5 (L1), 1 (L2), or 5 (L3) mg/kg. Lumbar spine and whole body bone mass were measured by dual-energy X-ray absorptiometry (DXA) pretreatment and at 6 and 12 months following the initiation of treatment. Bone mass at the femoral neck was measured by peripheral quantitative computed tomography (pQCT) at 0 and 12 months. Serum markers of bone turnover, including bone-specific alkaline phosphatase (BSAP), osteocalcin (BGP), tartrate-resistant acid phosphatase (TRAP), and urinary collagen C-terminal extension peptides (CrossLaps), were measured at 0, 6, and 12 months. Ovariectomy resulted in an increase in these markers; the increase was prevented by estradiol or levormeloxifene. Estradiol or levormeloxifene inhibited loss of lumbar spine bone mineral density (BMD) following ovariectomy compared with untreated monkeys (ovx -5.0%; sham -0.4%; est +0.2%; L1 -3.6%, L2 -2.0%, L3 -2.5%). Estradiol, but not levormeloxifene, prevented loss of BMD at the femoral neck (ovx -7.4%; sham -3.1%; est -3.6%; L1 -8.0%, L2 -6.5%, L3 -7.8%), and whole body bone mineral content (BMC) (ovx -7.6%; sham -1.9%, est -2.9%; L1 -6.2%, L2 -6.1%, L3 -6.7%). Bone loss at each site was correlated with bone turnover as measured by serum and urine biomarkers. There was no dose effect of levormeloxifene.
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PMID:Levormeloxifene prevents increased bone turnover and vertebral bone loss following ovariectomy in cynomolgus monkeys. 1147 85

This 2-year, double-masked, randomized, placebo-controlled trial was designed to evaluate the safety and efficacy in preventing bone loss in postmenopausal women of two doses of transdermal 17betaestradiol (estradiol) delivered by a matrix patch, compared with placebo. One hundred and sixty healthy, hysterectomized postmenopausal volunteers aged 40-60 years with serum estradiol levels < 20 pg/ml were started on treatment at four centers in The Netherlands. Every 6 months, bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA) at the lumbar spine, non-dominant wrist and left hip, and markers of bone turnover were assessed in urine and serum. The treatment arms were: estradiol, 100 microg/day (E-100, n = 53), oestradiol, 50 microg/day (E-50, n = 54), placebo (P-100, placebo to E-100, n = 27 or P-50, placebo to E-50, n = 26). Treatment was continued for up to 2 years. After 24 months, BMD of the lumbar spine in the E-100 group differed by 7.7% [5.8-9.5%] (mean [95% confidence interval]) from the placebo group and showed a mean (s.e.m.) increase in BMD from baseline of 5.9% (0.69%). For the E-50 group the difference compared with placebo was 6.2% [4.4-8.0%] and the absolute increase was 4.5% (0.62%); in the placebo group, the absolute change was -2.3% (0.48%). In the total wrist, the changes were: E-100: difference compared with placebo 2.5% [1.5 3.6%], absolute increase 0.6% (0.3%); E-50: difference compared with placebo 2.9% [1.8-3.9%], absolute increase 0.7% (0.25%); and absolute change on placebo: -2.5% (0.35%). In the total hip, the changes were: E-100: difference compared with placebo 3.7% [2.2-5.2%], absolute increase 2.8% (0.5%); E-50: difference compared with placebo: 3.2% [1,8-4.7%], absolute change 2.4% (0.36%); and absolute change on placebo -1.4% (0.66%). Three markers of bone turnover--serum bone-specific alkaline phosphatase, serum osteocalcin and urinary CTX--fell significantly during the trial. Breast pain was reported by 8% of women on placebo, by 6% of women on E-50 and by 17% of women on E-100. Estradiol delivered by the E-50 matrix patch effectively reversed bone loss in hysterectomized postmenopausal women with few side-effects. The marginal additional gain in BMD with the higher dose may be offset by a more important side effect profile.
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PMID:Effects of transdermal estradiol delivered by a matrix patch on bone density in hysterectomized, postmenopausal women: a 2-year placebo-controlled trial. 1190 92

17 beta-Estradiol (E(2)) regulates growth plate cartilage cells via classical nuclear receptor mechanisms, as well as by direct effects on the chondrocyte membrane. These direct effects are stereospecific, causing a rapid increase in protein kinase C (PKC) specific activity, are only found in cells from female rats and are mimicked by E(2)-bovine serum albumin (BSA), which cannot penetrate the cell membrane. E(2) and E(2)-BSA stimulate alkaline phosphatase specific activity and proteoglycan sulfation in female rat costochondral cartilage cell cultures, but traditional nuclear receptors do not appear to be involved. This study examined the effect of the anti-estrogen tamoxifen on these markers of chondrocyte differentiation; the gender-specificity of tamoxifen's effect on PKC, if tamoxifen has an effect on vitamin D metabolite-stimulated PKC, which is mediated via specific membrane receptors (1,25-mVDR; 24,25-mVDR) and whether the effect of tamoxifen is mediated by nuclear estrogen receptors. Tamoxifen dose-dependently inhibited the effect of E(2)-BSA on PKC, alkaline phosphatase and proteoglycan sulfation in confluent cultures of female resting zone (RC) cells and growth zone (GC) (prehypertrophic/upper hypertrophic zones) cells, suggesting that its action is at the membrane and not cell maturation-dependent. Neither the estrogen receptor (ER) antagonist ICI 182780 nor the ER agonist diethylstilbesterol affected E(2) or E(2)-BSA-stimulated PKC in female chondrocytes. Tamoxifen also inhibited the increase in PKC activity due to 1 alpha,25-(OH)(2)D(3) or 24R,25-(OH)(2)D(3) in growth plate cells derived from either female or male rats. Inhibition of PKC by tamoxifen may be a general property of membrane receptors involved in rapid responses to hormones.
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PMID:Tamoxifen elicits its anti-estrogen effects in growth plate chondrocytes by inhibiting protein kinase C. 1198 87

The effects of melatonin on osteoclastic and osteoblastic cells were examined using a culture system of the goldfish scale. Tartrate-resistant acid phosphatase (TRACP) and alkaline phosphatase (ALP) were used as markers of osteoclastic and osteoblastic cells, respectively. In Earle's minimum essential medium containing melatonin (10(-9) to 10(-5) m), activities of both enzymes in scales were significantly suppressed at 6 hr after incubation (TRACP: 10(-8), 10(-6), 10(-5) m; ALP: 10(-7) to 10(-5) m), but at 18 hr only ALP activity was significantly lowered (10(-8), 10(-7) m). Estradiol-17beta (E(2)) enhanced both activities, which were significantly inhibited and brought down to the level of the controls when co-incubated with E(2) and melatonin (TRACP at 6 hr: 10(-9) to 10(-5) m; ALP at 6 hr: 10(-7) m; ALP at 18 hr: 10(-8) m). Moreover, using reverse-transcription polymerase chain reaction, the mRNA expression of the estrogen receptor (ER) and insulin-like growth factor (IGF)-1, which are related to osteoblastic growth and differentiation, was decreased in the melatonin-treated scales. These results suggest that melatonin acts directly on the scale osteoclastic and osteoblastic cells where it suppresses the ALP activity via down-regulation of ER and IGF-1 mRNAs expression. This is the first report on the function of melatonin in osteoclasts and on the suppressive effect of melatonin in osteoblasts among vertebrates.
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PMID:Melatonin suppresses osteoclastic and osteoblastic activities in the scales of goldfish. 1239 May 9

To investigate day-to-day biological change of biochemical makers of bone turnover, we measured eight markers for 5 days in 10 healthy women. They aged 26-41 years (mean age; 31.1 years old), and had regular menstrual cycles. Fasting second void urine and blood was collected from them on five successive days. As serum marker, Estradiol (E2), intact PTH (i-PTH), Bone-specific alkaline phosphatase (BAP), and serum C-telopeptide (S-CTX) were measured. As urinary markers, urinary CTX (U-CTX), N-telopeptide (NTX), pyridinoline (Pyr) and deoxypyridinoline (Dpyr) were measured. Day-to-day physiological variations were different between bone markers. Variability of serum markers was less than that of urinary markers. Moreover, in the comparison of the same molecular marker, CTX, the variability of S-CTX was less than U-CTX. One should consider physiological variation of the marker to evaluate whether the change of the biochemical marker of bone turnover is significant or not.
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PMID:Biological variability of biochemical markers of bone turnover in healthy women. 1248 74


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