Plasma Osteocalcin Research Articles

Effects of intranasal corticosteroids on adrenal, bone, and blood markers of systemic activity in allergic rhinitis

Background: Intranasal corticosteroids are regarded as the first-line treatment for allergic rhinitis, but few studies have directly compared their systemic effects. Objective: The purpose of this study was to compare the systemic bioactivity of aqueous formulations of intranasal budesonide, mometasone furoate (MF), and triamcinolone acetonide (TAA) in terms of adrenal, bone, and white blood cell markers. Methods: Twenty patients with allergic rhinitis, mean age (SE) 35.7 (3.5) years were studied in a single-blind, randomized, 4-way crossover design, with treatments separated by 7-day washout periods, comparing placebo with budesonide 200 μg once daily, MF 200 μg once daily, and TAA 220 μg once daily. After 5 days of treatment at steady-state, serial blood and urine samples were taken for 24 hours. Collective and fractionated measurements (daytime, overnight, and 8 am) were done on plasma cortisol and urine cortisol/creatinine excretion. Plasma osteocalcin and blood eosinophil counts were measured at 8 am. Results: There was no significant difference between placebo and the active treatments with any of the markers of adrenal suppression. Mean values (SE) for 24-hour area under the curve plasma cortisol (nmol/L.hr) were placebo, 6312.9 (564.4); budesonide, 5908.8 (496.8); MF, 6374.1 (509.9); and TAA, 6239.2 (552.0). Twenty-four hour urinary cortisol/creatinine ratio (nanomoles per millimoles) showed placebo, 9.2 (0.5); budesonide, 8.5 (0.5); MF, 8.6 (0.4); and TAA, 8.6 (0.4). The diurnal circadian rhythm was unaffected, and there were only occasional patients with abnormally low cortisol values. There was also no suppression in terms of osteocalcin (placebo, 1.27 nmol/L; budesonide, 1.22 nmol/L; MF, 1.33 nmol/L; and TAA, 1.24 nmol/L) and blood eosinophil count (placebo, 0.29 × 10 9 /L; budesonide, 0.27 × 10 9 /L; MF, 0.25 × 10 9 /L; and TAA, 0.24 × 10 9 /L). Conclusion: Neither budesonide, MF, nor TAA produced significant systemic suppression of adrenal, bone, or white blood cell markers at the doses studied. This reflects the good safety profile of these aqueous intranasal formulations when taken at clinically recommended doses. (J Allergy Clin Immunol 1998;102:598-604.)

Effects of variations in dietary calcium and phosphorus supply on plasma and bone osteocalcin concentrations and bone mineralization in growing pigs.

Growing pigs were fed diets supplying 45% (low), 70% (intermediate) and 100% (high) recommended dietary allowances of calcium (the Ca:P ratio was kept constant), but otherwise adequate in nutrients. The effects of varying calcium and phosphorus intakes on bone and plasma osteocalcin were monitored. Mineral content of the diet did not affect feed conversion and live weight gain. Plasma phosphorus concentrations decreased significantly in pigs fed a low mineral diet compared with those fed the high mineral diet, but there were no changes in plasma calcium and osteocalcin concentrations. Bones from the low mineral group had marked reductions in dry matter, calcium and phosphorus contents, as well as increased collagen, pyridinoline and deoxypyridinoline concentrations: osteocalcin concentrations in bone were unaffected by treatment. The results showed no direct link between osteocalcin and the degree of bone mineralization.

Tamoxifen attenuates the effects of exogenous glucocorticoid on bone formation and growth in piglets.

Tamoxifen (Tam) has been shown to inhibit dexamethasone (Dex)-mediated effects on bone formation in vitro. Our objective was to determine whether Tam would block Dex-induced osteopenia and growth inhibition in growing piglets. Four-day-old male Yorkshire piglets were adapted to a liquid formula diet (400 ml/kg x day) and randomized to one of four groups (n = 5/group): Dex (0.5 mg/kg x day), Tam (1 mg/kg x day), Dex plus Tam, or placebo control (vehicle only). Both drugs were administered by orogastric gavage twice daily for 12 days. At baseline and at the end of treatment, whole body bone mineral density (BMD) was determined by dual energy x-ray absorptiometry (Hologic QDR1000W). Plasma osteocalcin and PTH were measured on days 0 and 12, and urinary N-telopeptide was measured on day 12. Changes in axial length and daily weight were also measured. Delta whole body BMD was 29% lower (P < 0.05) in Dex alone treated piglets than in controls (0.033 vs. 0.047 g/cm2, respectively), whereas the maximum change in BMD in Dex plus Tam group (0.046 g/cm2) was similar to that in controls. Concurrent Tam administration reduced the Dex-induced deficit in weight gain by 56% (P < 0.05) and the deficit in axial length gain by 72% (P < 0.01). In Dex alone treated piglets, PTH was significantly elevated (7-fold), whereas osteocalcin and N-telopeptide were significantly reduced compared with control values. These effects were prevented by Tam. These data suggest that the suppression of growth and other changes in parameters of bone metabolism induced by glucocorticoids in vivo can be attenuated by Tam.

Dexamethasone-induced abnormalities in growth and bone metabolism in piglets are partially attenuated by growth hormone with no synergistic effect of insulin-like growth factor-I.

Dexamethasone (DEX) therapy improves pulmonary compliance in premature infants with chronic lung disease; however, normal growth and bone development are impaired. Because DEX may mediate its effects by altering the GH-IGF-I axis, we investigated whether adjunctive therapy with GH or GH + IGF-I during DEX therapy could attenuate these DEX-induced effects. Piglets were randomized to placebo, oral tapered DEX (0.5, 0.3, and 0.2 mg kg(-1) d(-1) over 14 d), DEX + GH (0.1 mg kg(-1) d(-1)) or DEX + GH + IGF-I (0.1 mg kg(-1) d(-1)). Final whole body weight and length were improved with GH or GH + IGF-I compared with the DEX alone group. Plasma GH and IGF-I were not influenced by DEX, but infusion of IGF-I resulted in higher (p < 0.05) plasma IGF-I compared with all other groups at d 15. DEX reduced (p < 0.05) circulating IGFBP-2 and IGFBP-3 and liver IGFBP-2 and IGFBP-4 mRNA expression compared with controls. Treatment with DEX alone resulted in lower (p < 0.05) plasma osteocalcin, urinary N-telopeptide, and whole body and femur bone mineral density compared with controls, whereas results with piglets receiving adjunctive GH or GH + IGF-I were similar to those of controls. Given adjunctively, GH alone appears to partially counter the abnormalities in growth and bone metabolism associated with DEX therapy; however, this improvement cannot be attributed to higher circulating IGF-I, because combined therapy did not further improve growth or bone homeostasis compared with DEX + GH treatment. Growth hormone therapy has the potential to stimulate growth in infants exposed to steroid treatment.

DHEA and the Intracrine Formation of Androgens and Estrogens in Peripheral Target Tissues: Its Role during Aging

Human and some other primates are unique since their adrenals secrete large amounts of dehydroepiandrosterone (DHEA) and its sulfate (DHEA-S), which are converted into androstenedione (4-dione) and then into potent androgens and estrogens in peripheral tissues, therefore providing autonomous intracrine control to target tissues that can adjust the formation and metabolism of active sex steroids according to local requirements. Knowledge in this area has recently made rapid progress with the elucidation of the structure of most of the tissue-specific cDNAs and genes that encode the steroidogenic enzymes responsible for the transformation of these inactive precursor steroids into androgens and/or estrogens. It is estimated that 30 to 50% of total androgens in men are synthesized in peripheral intracrine tissues from inactive adrenal precursors while, in women, peripheral estrogen formation is even more important, the best estimate being 75% before menopause and 100% after menopause. The marked reduction in the formation of DHEA-S by the adrenals during aging, especially before the age of 50 years, results in a dramatic fall in the formation of active sex steroids in peripheral target tissues, a situation which is thought to be associated with a long series of age-related decreases such as insulin resistance, obesity, osteoporosis, cardiovascular diseases, loss of muscle mass, cancer and other diseases. We have demonstrated for the first time a series of medically important beneficial effects of DHEA administered for 12 months to post-menopausal women. Most interestingly, the bone mineral density significantly increased. This relatively rapid change was associated with an increase in plasma osteocalcin, a marker of bone formation, while a decrease in bone resorption reflected by a decrease in urinary hydroxyproline excretion was observed in parallel. In addition, the estrogenic stimulation of vaginal cytology in the absence of any sign of stimulatory effect on the endometrium is also of potentially major interest for the prevention and management of menopause. Furthermore, the inhibitory effect of DHEA on the growth of human breast cancer xenografts in vivo in nude mice supports the beneficial use of DHEA as hormone replacement therapy in women.

Circulating Levels of Tartrate-Resistant Acid Phosphatase in Rat Models of Non-Insulin-Dependent Diabetes Mellitus

In order to investigate the pathogenic role of bone resorption by osteoclasts in altered bone metabolism in non–insulin-dependent diabetes mellitus (NIDDM), the circulating levels of tartrate resistant acid phosphatase (TRACP) were simultaneously determined with osteocalcin, in rat models of NIDDM, i.e., genetic Wistar fatty rats and neonatally streptozotocin-induced diabetic rats (NSZ rats). In Wistar fatty rats exhibiting hyperglycemia and hyperinsulinemia, plasma TRACP was 40.0 ± 0.4 U/l (mean ± SE), significantly higher than that of 32.8 ± 1.3 U/l in their lean littermates ( p < 0.01). Bone length, bone strength, and weight of powdered bone in Wistar fatty rats were significantly decreased compared to control rats ( p < 0.02–0.001). On the other hand, plasma TRACP in NSZ rats was 13.6 ± 1.0 U/l, significantly lower than that of 31.4 ± 1.2 U/l in their controls ( p < 0.01). In addition, there were positive correlations between circulating TRACP and insulin levels in both NIDDM rat models ( p < 0.05–0.01). Furthermore, plasma osteocalcin levels in these NIDDM models were significantly decreased than those of their corresponding controls ( p < 0.001). Consequently, in Wistar fatty rats with hyperinsulinemia, it is suggested that the bone formation by osteoblasts was decreased, while the bone resorption by osteoclasts was increased. In contrast, in NSZ rats with hypoinsulinemia, both of bone formation and resorption were speculated to be decreased, indicating the decreased bone turnover. These results suggest that, although the deterioration in the osteoblastic function can be commonly observed in NIDDM animal models, the osteoclastic function is heterogeneous under NIDDM conditions.

Influence of Aging on Cortical and Trabecular Bone Response to Estradiol Treatment in Ovariectomized Rats

Three groups (n = 15/group) of 6-, 12- and 30-month-old (mature, old and senescent animals, respectively) female Wistar rats on a diet (6 g/100 g BW/day) containing 0.8% calcium and 0.8% inorganic phosphorus were studied. Within each group, 10 rats were ovariectomized surgically and 5 injected s.c. with 17β-estradiol (E rats, 10 µg/kg BW/48 h) and 5 with solvent alone (OVX rats) from day 2 until day 60 after ovariectomy. Five other rats were sham-operated (SH rats) and received solvent only. All rats were killed by exsanguination 60 days after ovariectomy. Neither ovariectomy nor estradiol treatment had a significant effect upon tibial mechanical properties in 6-, 12- and 30-month-old animals. Bone mineral density (BMD) and bone mineral content (BMC) of the distal femur and BMC of the whole femur were decreased by ovariectomy in 6- and 12-month-old rats, but were not different in the SH and E groups. In senescent animals, in which the lowest BMD and BMC were measured, estradiol treatment was more effective in increasing these parameters than in adult and old rats. Image analysis of the distal femoral diaphysis showed that estradiol treatment prevented trabecular bone loss induced by senescence and/or ovariectomy. In each group, urinary deoxypyridinoline excretion and plasma osteocalcin concentration were higher in the OVX animals than in the controls, consistent with increased bone turnover in the estrogen-deficient state. Both biochemical turnover markers were reduced in the estrogen-treated groups. These results indicate that 17β-estradiol is particularly effective at preventing high-turnover-induced osteopenia in 30-month-old animals.

Supplemental Arachidonic (AA) and Docosahexaenoic (DHA) Acids Increase Bone Mineral Density, but not Calcium Absorption, in Piglets † 1586

The objective of this study was to determine if supplemental AA and DHA increase bone mineral density without compromising growth. Twelve 10 d old male piglets were randomized to 14 d of standard formula (STD) (n-6:n-3 ratio of 4:1) or a fatty acid supplemented formula (FA) containing 0.5% AA and 0.1% DHA (w/w). Bone metabolism after 14 d was assessed by plasma osteocalcin, carboxy-terminal telopeptide of type I collagen (ICTP), carboxy-terminal propeptide of type I collagen (PICP) and urinary Ca, P and prostaglandin E2(PGE2) corrected to creatinine. Intestinal Ca absorption was assessed using an in situ ligated loop procedure. Whole body (WB), femur (F) and lumbar 2-4(L2-4) bone mineral content (BMC; g) and density (BMD; g/cm2) were measured using dual energy x-ray absorptiometry. All data are mean±SD with differences detected by t-tests. No differences were observed in initial weight (wt) or formula intake (400 mL/kg/d) during the study. After 14 d, FA piglets had a significantly higher wt (STD: 7.8±0.6 vs FA: 9.0±0.9 kg, P<0.05), but not length (lg)(STD: 61.6±1.6 vs 63.5±3.7 cm). Osteocalcin was significantly lower in FA piglets (STD: 21.3±2.5 vs FA 18.0±2.5 ug/L,P<0.05); PICP and ICTP were not different. There were no significant differences in urinary Ca/creatinine, P/creatinine and PGE2/creatinine; although Ca/creatinine tented to be lower. Intestinal Ca absorption was similar between groups (range 10-12 umol/30 min/g intestine). Results for BMC and BMD are in the table with significant differences between groups indicated by *, P<0.05. The results indicate the potential of dietary AA and DHA to enhance bone mineral density even though both groups received a high Ca/P diet. In addition, delays in growth were not observed, implying an appropriate n-6:n-3 fatty acid ratio.

Decreased trabecular bone mineral density in ulcerative colitis as well as Crohn's disease in newly diagnosed Korean patients

Decreased bone mineral density(BMD) may be already present at the time of diagnosis in patients with inflammatory bowe ! disease(IBD), at least in those with Crohn's disease(CD). However, the pathogenesis of the osteopenia is still unclear and bone histology of newly diagnosed patients with IBD has never been reported. Our aim was to study BMD and biochemical parameters in newly diagnosed patients in Korea, where the incidence of IBD is persistently increasing with westernization. We also obtained a specimen of bone biopsy to assess hist0morphometry. Methods: We studied 5 patients with CD(3 M, 2 F, mean age 26, range 21-32 years) and 7 patients with ulcerative colitis(UC, 4 M, 3 F, mean age 34, range 22-44 years), all of whom were newly diagnosed and had not received corticosteroids. BMD was measured in lumbar spine and femoral neck by dual energy x-ray absorptiometry. Biochemical parameters including plasma osteocalcin, PTH, inactive and active vitamin D and urinary deoxypyridinoline were measured. Bone biopsy was obtained from a 32-yearold man with CD by transilial approach after administration of pulsed doses of tetracycline. Results: 6 cases(50%) of the patients had a reduced BMD at lumbar spine(Z score<1).

Bone and mineral abnormalities in childhood acute lymphoblastic leukemia: Influence of disease, drugs and nutrition

In children with acute lymphoblastic leukemia (ALL), abnormalities in mineral homeostasis and bone mass were first reported by our group in the late 1980s. Prospective longitudinal cohort studies in 40 consecutive patients receiving treatment according to the Dana-Farber Cancer Institute (DFCI) protocol 87-001 and 16 children receiving DFCI protocol 91-001 afforded us the opportunity to explore various etiologies of the observed abnormalities in mineral and bone metabolism, specifically the leukemic disease process and chemotherapeutic drugs such as steroids and aminoglycoside antibiotics. At diagnosis of ALL, > 70% of children had abnormally low plasma 1,25-dihydroxyvitamin D, 73% had low osteocalcin and 64% had hypercalciuria, indicating an effect of the leukemic process on vitamin D metabolism and bone turnover. During remission induction, treatment with high-dose steroid (prednisone or dexamethasone) resulted in further reduction in plasma osteocalcin and elevated parathyroid hormone levels. During 24 months of chemotherapy-maintained remission, reduction in bone mineral content (BMC), as measured by Z-scores, occurred in 64% of children, most severely affecting those > 11 years of age. A reduction in BMC during the first 6 months had a positive predictive value of 64% for subsequent fracture. By the end of 2 years of therapy, fractures occurred in 39% of children and radiographic evidence of osteopenia was found in 83% of the entire study group. Investigations of the biochemical basis of the bone abnormalities revealed that by 6 months hypomagnesemia developed in 84% of children (of whom 52% were hypermagnesuric) and plasma 1,25-dihydroxyvitamin D remained abnormally low in 70%. Altered magnesium status was attributed to renal wastage of magnesium following cyclical prednisone therapy and treatment with aminoglycoside antibiotics such as amikacin for fever accompanying neutropenia. Dietary intake and absorption of magnesium were normal. In 10 children treated for hypomagnesemia with supplemental magnesium for up to 16-20 weeks, plasma magnesium normalized in only 50% of subjects.

Effect of Zinc Supplementation on Plasma Osteocalcin Levels in Healthy Young and Elderly Subjects

Effect of Zinc Supplementation on Plasma Osteocalcin Levels in Healthy Young and Elderly Subjects

Effect of 12-Month Dehydroepiandrosterone Replacement Therapy on Bone, Vagina, and Endometrium in Postmenopausal Women

The effect of 12-month dehydroepiandrosterone (DHEA) replacement therapy has been evaluated in 14 60- to 70-yr-old women who received daily applications of a 10% DHEA cream. Vaginal epithelium maturation was stimulated by DHEA administration in 8 of 10 women who had a maturation value of zero at the onset of therapy, whereas a stimulatory effect was also seen in all three women who had an intermediate vaginal maturation index before therapy. The estrogenic effect of DHEA observed in the vagina was not observed in the endometrium, which remained atrophic in all women. Most interesting, the bone mineral density significantly increased at the hip from 0.744 ± 0.021 to 0.759 ± 0.025 g/cm2 after 12 months of treatment (P < 0.05). These changes in bone mineral density were associated with a significant 20.0% decrease (P < 0.01) in plasma bone alkaline phosphatase and a 28% decrease in the urinary hydroxyproline/creatinine ratio. A 2.1-fold increase over the control value (P < 0.01) in plasma osteocalcin was concomitantly observed. The present data describe for the first time a series of medically important beneficial effects of DHEA therapy in postmenopausal women through transformation of the precursor steroid DHEA into androgens and/or estrogens in specific peripheral intracrine tissues without significant adverse effects. The stimulatory effect on the vaginal epithelium in the absence of stimulation of the endometrium is of particular interest because it eliminates the need for progestin replacement therapy. On the other hand, the stimulatory effect on bone mineral density accompanied by an increase in serum osteocalcin, a marker of bone formation, suggests stimulation of bone formation by the androgenic action of DHEA, a finding of particular interest for both the prevention and treatment of osteoporosis.

Effect of 12-month dehydroepiandrosterone replacement therapy on bone, vagina, and endometrium in postmenopausal women.

The effect of 12-month dehydroepiandrosterone (DHEA) replacement therapy has been evaluated in 14 60- to 70-yr-old women who received daily applications of a 10% DHEA cream. Vaginal epithelium maturation was stimulated by DHEA administration in 8 of 10 women who had a maturation value of zero at the onset of therapy, whereas a stimulatory effect was also seen in all three women who had an intermediate vaginal maturation index before therapy. The estrogenic effect of DHEA observed in the vagina was not observed in the endometrium, which remained atrophic in all women. Most interesting, the bone mineral density significantly increased at the hip from 0.744 +/- 0.021 to 0.759 +/- 0.025 g/cm2 after 12 months of treatment (P < 0.05). These changes in bone mineral density were associated with a significant 20.0% decrease (P < 0.01) in plasma bone alkaline phosphatase and a 28% decrease in the urinary hydroxyproline/creatinine ratio. A 2.1-fold increase over the control value (P < 0.01) in plasma osteocalcin was concomitantly observed. The present data describe for the first time a series of medically important beneficial effects of DHEA therapy in postmenopausal women through transformation of the precursor steroid DHEA into androgens and/or estrogens in specific peripheral intracrine tissues without significant adverse effects. The stimulatory effect on the vaginal epithelium in the absence of stimulation of the endometrium is of particular interest because it eliminates the need for progestin replacement therapy. On the other hand, the stimulatory effect on bone mineral density accompanied by an increase in serum osteocalcin, a marker of bone formation, suggests stimulation of bone formation by the androgenic action of DHEA, a finding of particular interest for both the prevention and treatment of osteoporosis.

Decreased osteoblast activity in spontaneously diabetic rats. In vivo studies on the pathogenesis.

Diabetes in both humans and rats is accompanied by low bone formation, which is presumably caused by serum-borne factors. To explore its pathogenesis, we carried out experiments in diabetic and nondiabetic BB rats, using plasma osteocalcin concentrations (OC) as a marker for osteoblast activity. In nondiabetic rats, the i.v. infusion of glucose (30%, 4 d) did not change OC; s.c. insulin infusion (4 U/d, 14 d) reduced OC by 27% (p < 0.01). In diabetic rats, OC were decreased from the first day of glycosuria (71 +/- 5% of paired controls), declining exponentially to 24 +/- 3% after 5 wk. Insulin infusion (1, 2, and 3 U/d, 14 d) produced gradual restoration of OC. OC were better correlated with insulin-like growth factor-I (IGF-I) than with insulin levels in these experiments. OC were dramatically increased 4 d after adrenalectomy (ADX) in all diabetic rats (73 +/- 8 vs 22 +/- 4 micrograms/L before ADX; p < 0.001), but not if corticosterone was administered. Ligand blotting of IGF binding proteins showed a marked decrease in two bands (44-49 and 32-35 kDa) 10-14 d after diabetes onset; the density of these bands was increased, but not normalized after ADX. Thus, decreased osteoblast activity is present from the onset of diabetes, is dependent on endogenous corticosterone, and cannot be reproduced by hyperglycemia in nondiabetic rats.

Effects of combined low dose of the isoflavone derivative ipriflavone and estrogen replacement on bone mineral density and metabolism in postmenopausal women

Objectives: To assess the pattern of biochemical markers of bone metabolism and vertebral bone mineral density in early postmenopausal women treated with combined ipriflavone and low dose conjugated estrogens. Methods: Bone biochemical markers and vertebral bone density were evaluated in a longitudinal, comparative, 2 year study conducted in postmenopausal women treated with sole calcium supplementation (500 mg/day), or with either ipriflavone (IP) at the standard dose (600 mg/day) plus the same calcium dose, low dose conjugated estrogens (CE) (0.3 mg/day) plus calcium, or low dose IP (400 mg/day) plus low dose CE (0.3 mg/day) plus calcium. The results were analyzed by repeated measures analysis of variance, as appropriate. Results: No modifications of both urinary excretion of hydroxyproline and plasma osteocalcin levels were observed in calcium and in CE-treated women, while vertebral bone density significantly decreased ( P < 0.0001) in both groups. In IP or IP + CE-treated women, plasma osteocalcin did not show any modification, while urinary hydroxyproline showed a significant ( P < 0.05) decrease, that paralleled a significant ( P < 0.05) increase in vertebral bone density. Conclusion: Postmenopausal IP administration, at the standard dose of 600 mg/day, can prevent the increase in bone turnover and the decrease in bone density that follow ovarian failure. The same effect can be obtained with the combined administration of low dose (400 mg/day) IP with low dose (0.3 mg/day) CE.

Vitamin C Supplementation Does Not Modify Bone Mineral Content or Mineral Absorption in Growing Pigs ,

We have demonstrated that alkaline phosphatase activity and collagen synthesis are dose-dependently stimulated by ascorbic acid in differentiated pig osteoblasts. In this study we further examined the relationship between ascorbic acid and bone metabolism by feeding young pigs large amounts of ascorbic acid. Three groups of seven 47-d-old pigs were given no ascorbic acid supplement (control), 500 (500 AA) or 1000 (1000 AA) mg ascorbic acid/kg diet for 4 mo. Calcium and P absorption and retention were evaluated by a 14-d balance trial immediately before killing in control and 1000 AA groups only (n = 6). Bones were collected at death and the bone ash and bending moment (three-point bending test) determined. Various plasma and urine indices of bone metabolism, especially those reflecting collagen degradation (hydroxyproline, deoxypyridinoline) and synthesis (carboxyterminal propeptide of type I collagen) were monitored. The plasma ascorbic acid concentrations increased with time and paralleled the dietary concentrations (P < 0.01). The Ca and P balances and the bone ash and bending moments in the ascorbic acid–supplemented pigs did not differ from those of the controls. Plasma osteocalcin was elevated (P < 0.05), whereas the other bone formation markers, alkaline phosphatase and carboxy terminal propeptide of type I collagen, were not affected by ascorbic acid. The plasma concentrations of Ca, P and 1,25-dihydroxycholecalciferol did not differ among the three groups. The unaffected urinary excretion of deoxypyridinoline and hydroxyproline in the ascorbic acid–supplemented pigs indicates that ascorbic acid does not alter bone resorption. Thus, high intakes of ascorbic acid have no positive influence on bone metabolism and bone characteristics in pigs. The in vivo long-term effects do not correlate with the short-term in vitro effects previously reported.

Influence of treadmill running on femoral bone in young orchidectomized rats.

Forty 6-wk-old male Wistar rats weighing 308 +/- 24 g were divided into two groups. On day 0, the 20 animals in one group were surgically castrated and the other group was sham operated. Within each group, 10 rats were selected for treadmill running (60% maximal O2 consumption, 1 h/day, 6 days/wk for 15 wk). The 20 sedentary rats were used as controls. At the time the rats were killed (day 105), running had no significant effect on femoral mechanical properties either in castrated or in sham-operated rats. Femoral bone density was lower in orchidectomized than in sham-operated rats. Nevertheless, it was higher in exercised than in sedentary rats. Femoral Ca content paralleled changes in bone density. Treadmill running had no significant effect on plasma osteocalcin concentration but inhibited the increase in urinary deoxypyridinoline excretion observed in castrated rats. Image analysis (measured at the distal femoral diaphysis) revealed that these effects mainly resulted from decreased trabecular bone resorption in castrated exercised rats.

Serum bone alkaline phosphatase is superior to plasma levels of bone matrix proteins for assessment of bone metabolism in patients receiving renal transplants

The plasma concentrations of two bone matrix proteins (osteocalcin, osteonectin) were monitored in 56 samples from 14 patients receiving renal transplants and the values compared with serum bone alkaline phosphatase mass concentrations and osteotropic hormone levels (parathyroid hormone, calcitriol). There were no significant changes in the concentrations of plasma osteonectin at any time after transplantation, as compared with the values before transplantation ( P > 0.1). None of the plasma samples showed osteonectin levels above the reference interval. There was a weak but significant relationship between platelet counts and plasma osteonectin levels ( r = + 0.322; P < 0.05). Osteocalcin showed a marked decrease of the values 1 week following transplantation as compared with the values before transplantation without further change of the values 1 and 3 months after transplantation ( P > 0.5) whereas 3 months after transplantation bone alkaline phosphatase levels were higher than before transplantation ( P < 0.05). Multiple regression analysis (performed with, data from 42 samples obtained after transplantation) revealed serum creatinine as an independent predictor of plasma osteocalcin whereas serum calcitriol was an independent predictor of serum bone alkaline phosphatase ( P < 0.05). No correlation was observed between serum calcitriol/plasma parathyroid hormone on the one hand and plasma osteocalcin on the other ( P > 0.05). After transplantation there was a lack of correlation between serum bone alkaline phosphatase mass concentrations and plasma osteocalcin values ( P > 0.05). In conclusion, serum bone alkaline phosphatase should be preferred to bone matrix proteins for the assessment of bone metabolism in patients receiving renal transplants: (a) bone alkaline phosphatase — but not osteocalcin — is significantly correlated with calcitriol and adequately reflects increased bone formation after renal transplantation; (b) interpretation of osteocalcin values is severely hampered by their strong correlation with serum creatinine concentrations; (c) plasma osteonectin determinations are not useful for monitoring bone formation.

Effect of diets varying in nitrogen or phosphorus content on indicators of bone growth in lambs.

Growing lambs were fed diets low in nitrogen and phosphorus (LNLP), low in nitrogen and high in phosphorus (LNHP), high in nitrogen and low in phosphorus (HNLP) or high in nitrogen and phosphorus (HNHP) and the effects on bone growth and on blood and urinary bone marker levels or excretion rates were monitored. Plasma calcium concentrations were higher, and phosphorus concentrations lower, in lambs fed the low phosphorus diets but there were no differences in plasma 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) concentrations. Lambs fed both low phosphorus diets (LNLP and HNLP) had lower plasma osteocalcin and higher bone-specific alkaline phosphatase concentrations than those fed the high phosphorus diets. Urinary pyridinoline and deoxypyridinoline excretion were also affected by treatment, with their rates of excretion being highest in lambs fed the diet low in both nitrogen and phosphorus (LNLP). Lambs fed the low phosphorus diets were lighter in weight at slaughter and had lighter bones that were less well mineralized than those fed the high phosphorus diets. Reducing the nitrogen content of the diet appeared to have little effect on bone composition. These results suggest that bone markers that have proved useful in the diagnosis and treatment of bone disease are sensitive to variation in nutrient supply and may prove useful in early detection of nutrient deficiencies that affect bone growth.

Influence of Ovariectomy and Estradiol Treatment on Calcium Homeostasis During Aging in Rats

Study was carried out on Wistar female rats to evaluate the consequences of ovariectomy and 17β-estradiol substitutive treatment during aging on bone, Ca metabolism and calciotropic hormones. Three groups of fifteen rats, mature, old and senescent (4–, 10–, and 28 month-old) female were fed a diet (6 g/100 g BW/day) containing 0.9% Ca and 0.8% Pi. Within each group, 10 rats were surgically ovariectomized (OVX). From day 1 until day 60 after OVX, they were subcutaneously injected with either 17β-estradiol (E: 10 µg/kg BW/48 h; n = 5) or with solvent alone (OVX; n = 5). Five other rats were sham operated (SH) and received solvent alone. Animals were put in balance 1 day per week to determine Ca and Pi intestinal apparent absorption and urinary pyridinium cross-links excretion was measured by HPLC. All rats were killed by exsanguination 60 days after OVX. Plasma was collected for measurement of intact parathyroid hormone (PTH), calcitonin (CT), insulin-like growth factor-1 (IGF-1), Ca and Pi. The success of OVX was confirmed at necropsy by observation of marked atrophy of the uterine horns. The right femur was collected, cleaned from adjacent tissue and used for mineral analysis. Despite correct matching for feeding, BW was significantly larger in 6 and 12 month-old OVX rats. OVX and 17β-estradiol had no significant effect upon plasma Ca, Pi and CT concentrations. Aging is associated with increased circulating PTH levels (pg/ml) (SH - 6 months: 50.8 ± 12.6; 12 months: 219.1 ± 34.9; 30 months: 158.7 ± 23.5; P < 0.05). Ur inary and fecal Ca and Pi excretion in senescent animals were higher than in adult or old rats, thus resulting in a drastic fall in both intestinal apparent absorption and retention of Ca and Pi in 30 month-old animals. In each group, urinary pyridinium cross-links excretion and plasma osteocalcin concentration were higher in the OVX animals than in the controls, consistent with increased bone turnover in the estrogen deficient state. Both biochemical turnover markers were reduced in the estrogen-treated groups. In the same way, OVX increased and estrogen decreased the plasma IGF-1 levels. We conclude that 17β-estradiol prevents high turnoverinduced osteopenia even in 30 month-old rats.