Effect of calcium stress on the skeleton mass of intact and ovariectomized rats

Female rats were ovariectomized (Ovx) or sham-operated (control) at 18 weeks and the entire skeleton obtained at 24 weeks (baseline) or after an additional 31 day (28 week) interval on a normal (1.0%) or deficient (0.02%) calcium diet. Ovx rats showed a 42% increase in whole body bone resorption (3H-tetracycline loss) in the absence of calcium stress (1.0% calcium diet) and a 70% increase in resorption with morphological evidence of dramatic loss of cancellous bone mass when placed on calcium-deficient (0.02%) diets. Ovx rats kept on the 1.0% calcium diet showed a significant increase in both their body weight (30.2%) and total bone mass (11.6%) compared to baseline sham-operated controls. However, the total skeleton mass of these animals was significantly reduced (-20%) from that predicted by calculations based on body weight. Maintaining animals on calcium-deficient diets had no significant effect on the total skeleton mass of either control or Ovx rats in comparison with age-matched controls on 1.0% diets. It was further determined that an increase in bone mass between 24 and 28 weeks in rats receiving 1.0% dietary calcium occurred in both the axial and appendicular skeleton and was proportionately similar between control and Ovx groups. However, in animals subjected to dietary calcium stress during this interval, the decreased skeletal growth noted was confined primarily to the axial skeleton. The data indicate that ovariectomy or ovariectomy plus calcium stress does not result in loss of total bone mass during the interval of dramatically increased resorption and rapid loss of cancellous bone. The results suggest that the deterioration in individual bone structural and mechanical integrity due to ovariectomy or dietary calcium deficiency may not be attributed to overt loss in total bone mass but may involve a redistribution of bone mass.     

Dietary calcium,sex hormones,and bone mineral density in men.

OBJECTIVE--To evaluate the factors that determine bone mineral density at axial and appendicular sites in normal men. DESIGN--Measurement of bone mineral density of the radius by single photon absorptiometry and of the lumbar spine and hip by dual photon absorptiometry to assess their relation with various determinants of bone mineral density. Dietary calcium was assessed from a questionnaire validated against a four day dietary record. SETTING--Local community, Sydney, Australia. PATIENTS--48 Men (aged 21-79, median 44) recruited from the local community including 35 male cotwins of twin pairs of differing sex recruited from the Australian National Health and Medical Research Council twin registry for epidemiological studies on determinants of bone mineral density. MAIN OUTCOME MEASURES--Bone mineral density of the axial and appendicular skeleton and its relation to age, anthropometric features, dietary calcium intake, and serum sex hormone concentrations. RESULTS--Dietary calcium intake (g/day) was a significant predictor of bone mineral density of axial bones, explaining 24% and 42% of the variance at the lumbar spine and femoral neck respectively. This effect was independent of weight. In contrast with the axial skeleton, bone mineral density at each forearm site was predicted by weight and an index of free testosterone but not by dietary calcium intake. CONCLUSIONS--Dietary calcium intake has a role in the determination or maintenance, or both, of the axial but not the appendicular skeleton in adult men.     

Enhancing effect of dietary vinegar on the intestinal absorption of calcium in ovariectomized rats.

We studied the effect of dietary vinegar on calcium absorption by using ovariectomized rats fed on a low-calcium diet. The apparent absorption of calcium was higher when the rats were fed on a diet containing 1.6% vinegar for 32 days than when fed on a diet without vinegar (P < 0.05). The calcium content in the femur of the rats given diets containing 0.4% and 1.6% vinegar were also higher (P < 0.05). The serum parathyroid hormone level was lower and the crypt depth of the duodenum thicker in the rats fed on a diet containing 1.6% vinegar (P < 0.05). These results suggest that dietary vinegar enhanced intestinal calcium absorption by improving calcium solubility and by the trophic effect of the acetic acid contained in vinegar, which would reduce the bone turnover caused by ovariectomy and be helpful in preventing osteoporosis.     

Effects of dietary calcium on the metabolism of trace elements in male and female rats

The effect of dietary calcium on the metabolism of iron, zinc, copper, and manganese in male and female rats was investigated. For 3 or 6 weeks the rats were fed three diets containing: (1) 0.26, (2) 0.52, or (3) 2.08% Ca. The apparent absorption of iron was depressed by the high calcium diet, and manganese absorption was highest in the low calcium groups. Generally there was a decrease in the absorption of minerals from 3 to 6 weeks. With an increase in the dietary calcium the absorption of Ca and P decreased. The liver iron concentration in the females fed diet 3 decreased from about 600 to 200 microg/g dry weight. The high calcium intake also caused a slight increase in the heart calcium levels in both sexes. However, diet 3 prevented kidney calcification in the female rats at 6 weeks and this was attributed to a dramatic decrease in the urinary phosphorus, although the calcium had increased about 40 times. In males, on the other hand, the high calcium diet caused some kidney calcification.     

Dietary fat composition modifies the effect of boron on bone characteristics and plasma lipids in rats

Female and male rats weighing about 170 g and 200 g, respectively, were fed diets (approximately 70 microg boron/kg) in a factorial arrangement with supplemental boron at 0 (deficient) and 3 (adequate) mg/kg and canola oil or palm oil at 75 g/kg of diet as variables. After 5 weeks, six females in each treatment were bred. Dams and pups continued on their respective dietary treatments through gestation, lactation and post-weaning. Thirteen weeks after weaning, plasma and bones were collected from 12 male and 12 female offspring in each treatment. Boron supplementation increased femur strength measured by the breaking variable bending moment; tibial calcium and phosphorus concentrations; and plasma alkaline phosphatase. Femur breaking stress was greatest in boron-supplemented rats fed canola oil, and lowest in boron-deprived females fed canola oil; this group also exhibited the lowest femur bending moment. Minerals associated with bone organic matrix, zinc and potassium, were increased by boron supplementation in tibia. Plasma phospholipids were decreased by boron deprivation in females, but not males. Plasma cholesterol was decreased in boron-supplemented males by replacing canola oil with palm oil. The findings suggest that a diet high in omega-3 alpha-linolenic acid promotes femur strength best when the dietary boron is adequate.     

Feeding flaxseed oil but not secoisolariciresinol diglucoside results in higher bone mass in healthy rats and rats with kidney disease

Flaxseed's oil and lignan, secoisolariciresinol diglucoside (SDG), are implicated in attainment of health and treatment of renal injury and osteoporosis. To test for these benefits, weanling Han:SPRD-cy rats (n=171) with or without kidney disease were randomized to diets made with either corn oil or flaxseed oil and with or without SDG for 12 weeks. In females, weight was lower with the SDG diet. In males fed flaxseed oil, lean mass was higher and fat % was lower. In both sexes, fat % was lower in diseased rats. Bone mineral content (BMC) and density were higher in rats fed flaxseed oil and lower in diseased rats, additionally; BMC was lower in SDG-supplemented females. The benefit of flaxseed oil on body composition is sex specific but the effect on bone mass is not. Lastly, reduced weight due to early rat kidney disease is not due to loss of lean body mass.     

Effect of dietary calcium: Phosphorus ratio on bone mineralization and intestinal calcium absorption in ovariectomized rats

We investigated the effect of dietary calcium:phosphorus (Ca:P) ratio on bone mineralization and intestinal Ca absorption in ovariectomized (OVX) rat models of osteoporosis and sham-operated rats. Thirty 12-wk-old female Wistar rats were divided into three groups of OVX rats and three groups of sham rats. Thirty days after the adaptation period, OVX rats and sham rats were fed a diet formulated Ca:P, 1:0.5, 1:1 or 1:2 (each diet containing 0.5% Ca), respectively for 42 d. In both sham and OVX rats, serum osteocalcin, a marker of bone turnover, was increased by decreasing Ca:P ratio (1:2). In contrast, rats fed the Ca:P = 1:0.5 diet (dietary P restriction) suppressed the increased serum parathyroid hormone, osteocalcin and urinary deoxypyridinoline, and increased Ca absorption in both sham and OVX rats compared to the Ca:P = 1:1 and 1:2 diets. Especially, in OVX rats, the decreased bone mineral density of the fifth lumbar was also suppressed when rats were fed the Ca:P = 1:0.5 diet. These results indicated that the elevation of dietary Ca:P ratio may inhibit bone loss and increase intestinal Ca absorption in OVX rats.     

Effects of ovariectomy on duodenal calcium transport in the rat: altered ability to adapt to low-calcium diet

Studies were undertaken to determine whether ovariectomy (ovx) would alter the ability of female rats to adapt to low dietary Ca intake by exhibiting an in duodenal active Ca transport. Intact and ovx female rats were fed diets containing 1.5, 0.50, or 0.02% Ca prior to measuring active Ca transport using everted duodenal sacs in vitro. In some experiments, ovx animals were pair-fed to intact animals of the same age consuming the same diet. When ovx animals were allowed to eat ad lib, we found that both growth rate and duodenal active Ca transport increased relative to age-matched, intact controls. However, when growth of ovx animals was maintained at the control rate by pair-feeding, ovx per se did not affect intestinal active Ca transport. Ovx did not alter circulating levels of 1,25-dihydroxyvitamin D (1,25(OH)2D). We found that intact females responded to the low-Ca (0.02%) diet with increased circulating 1,25(OH)2D levels and increased intestinal active Ca transport. Ovx animals exhibited the same increase in circulating concentrations of 1,25(OH)2D in response to low-Ca diet, but did not demonstrate increased duodenal active Ca transport. When ovx animals consumed the diet ad lib, they became larger and exhibited higher Ca transport rates than intact animals fed the high-Ca diet, but there was no difference in Ca transport between ovx animals fed diets containing different Ca contents. The results of these experiments demonstrate that in female rats, the ability to adapt to altered dietary Ca intake is dependent on intact ovarian function and is not necessarily directly related to circulating concentrations of 1,25(OH)2D.     

Effects of vitamin K2 administration on calcium balance and bone mass in young rats fed normal or low calcium diet

OBJECTIVE: The purpose of this study was to examine the effects of vitamin K2 administration on calcium balance and bone mass in young rats fed a normal or low calcium diet. METHODS: Forty female Sprague-Dawley rats, 6 weeks of age, were randomized by stratified weight method into four groups with 10 rats in each group: 0.5% (normal) calcium diet, 0.1% (low) calcium diet, 0.5% calcium diet + vitamin K2 (menatetrenone, 30 mg/100 g chow diet), and 0.1% calcium diet + vitamin K2. After 10 weeks of feeding, serum calcium and calciotropic hormone levels were measured, and intestinal calcium absorption and renal calcium reabsorption were evaluated. Bone histomorphometric analyses were performed on cortical bone of the tibial shaft and cancellous bone of the proximal tibia. RESULTS: Feeding a low calcium diet induced hypocalcemia, increased serum parathyroid hormone (PTH) and 1,25-dihydroxyvitamin D [1,25(OH)2D] levels with decreased serum 25-hydrovyvitamin D [25(OH)D] level, stimulated intestinal calcium absorption and renal calcium reabsorption, and reduced cortical bone mass as a result of decreased periosteal bone gain and enlarged marrow cavity, but did not significantly influence cancellous bone mass. Vitamin K2 administration in rats fed a low calcium diet stimulated renal calcium reabsorption, retarded the abnormal elevation of serum PTH level, increased cancellous bone mass, and retarded cortical bone loss, while vitamin K2 administration in rats fed a normal calcium diet stimulated intestinal calcium absorption by increasing serum 1,25(OH)2D level, and increased cortical bone mass. CONCLUSION: This study clearly shows the differential response of calcium balance and bone mass to vitamin K2 administration in rats fed a normal or low calcium diet.     

Phytase supplementation increases bone mineral density,lean body mass and voluntary physical activity in rats fed a low-zinc diet

Phytic acid forms insoluble complexes with nutritionally essential minerals, including zinc (Zn). Animal studies show that addition of microbial phytase (P) to low-Zn diets improves Zn status and bone strength. The present study determined the effects of phytase supplementation on bone mineral density (BMD), body composition and voluntary running activity of male rats fed a high phytic acid, low-Zn diet. In a factorial design, rats were assigned to ZnLO (5 mg/kg diet), ZnLO+P (ZnLO diet with 1500 U phytase/kg) or ZnAD (30 mg/kg diet) groups and were divided into voluntary exercise (EX) or sedentary (SED) groups, for 9 weeks. SED rats were significantly heavier from the second week, and no catch-up growth occurred in EX rats. Feed intakes were not different between groups throughout the study. ZnLO animals had decreased food efficiency ratios compared to both phytase-supplemented (ZnLO+P) and Zn-adequate (ZnAD) animals (P<.01 compared to ZnLO). The ZnLO+P and ZnAD rats ran 56–75 km more total distance than ZnLO rats (P<.05), with the ZnLO+P rats running more kilometers per week than the ZnLO rats by Week 6. In vivo DEXA analyses indicate that rats fed phytase-supplemented diets had higher lean body mass (LBM) than those fed ZnLO diets; and that rats fed the Zn-adequate diets had the highest LBM. Body fat (%) was significantly lower in EX rats and was both Zn- and phytase insensitive. Rats fed phytase-supplemented diets had higher bone mineral content (BMC), bone area (BA) and BMD than rats fed ZnLO diets; and in rats fed ZnAD diets these indices were the highest. The dietary effects on BMC, BA and BMD were independent of activity level.We conclude that consuming supplemental dietary phytase or dietary Zn additively enhances Zn status to increase BMD, LBM and voluntary physical activity in rats fed a low-Zn diet. While the findings confirm that bone health is vulnerable to disruption by moderate Zn deficiency in rats, this new data suggests that if dietary Zn is limiting, supplemental phytase may have beneficial effects on LBM and performance activity.     

Bone loss is a physiological cost of reproduction in white-footed mice (Peromyscus leucopus)

Investment in offspring production often requires the mobilization of endogenous resources, a strategy that may negatively impact maternal condition. In mammals, skeletal ossification in growing offspring requires a large investment of calcium by mothers, and bone loss has been described in several species as a means of supporting this demand. Although bone loss can have adverse effects on the mother, its potential role in a reproductive trade-off has not been addressed. Using white-footed mice (Peromyscus leucopus), we tested the effect of dietary calcium availability on maternal skeletal condition during reproduction to assess if calcium availability drives a trade-off between maternal skeletal condition and offspring production. We provided mice with a low-calcium or standard diet and monitored reproductive output along with changes in bone mineral density and bone resorption (via serum concentrations of pyridinoline cross-links) throughout reproduction. Reproductive performance was not impaired by low calcium intake. Reproductive females on the low-calcium diet showed a significant reduction in bone mineral density relative to reproductive females consuming the standard diet and non-reproductive mice consuming the low-calcium diet, but no difference in bone resorptive activity. Our results suggest that when dietary calcium is limited white-footed mice reproduce at the expense of their skeletal condition, and may do so by limiting bone mineral accretion relative to resorption.     

Bone chemistry and prehistoric diet: strontium studies of laboratory rats

Strontium analysis of prehistoric human bone for the reconstruction of past diets is a relatively new technique in anthropology. In order to evaluate certain assumptions of the method, diets with low and high levels of strontium were fed to male, virgin female, and pregnant female laboratory rats. Analysis of the femurs of these rats by inductively coupled plasma/atomic emission spectrometry indicates that dietary intake is directly reflected in levels of strontium in bone ash. When dietary strontium levels were low, the observed ratio for bone:diet in the laboratory rats averaged 0.26, a value similar to that observed by other investigators. Among the groups fed high levels of strontium, pregnant females accumulated the most and virgin females accumulated the least strontium in bone. Males were intermediate. Gender differences in bone strontium among prehistoric human populations are considered in these terms.     

Dietary ratio of n-6/n-3 PUFAs and docosahexaenoic acid: actions on bone mineral and serum biomarkers in ovariectomized rats

Hypoestrogenic states escalate bone loss in animals and humans. This study evaluated the effects of the amount and ratio of dietary n-6 and n-3 polyunsaturated fatty acids (PUFAs) on bone mineral in 3-month-old sexually mature ovariectomized (OVX) Sprague-Dawley rats. For 12 weeks, the rats were fed either a high-PUFA (HP) or a low-PUFA (LP) diet with a ratio of n-6/n-3 PUFAs of 5:1 (HP5 and LP5) or 10:1 (HP10 and LP10). All diets (modified AIN-93G) provided 110.4 g/kg of fat from safflower oil and/or high-oleate safflower oil blended with n-3 PUFAs (DHASCO oil) as a source of docosahexaenoic acid (DHA). Fatty acid analyses confirmed that the dietary ratio of 5:1 significantly elevated the amount of DHA in the periosteum, marrow and cortical and trabecular bones of the femur. Dual-energy X-ray absorptiometry measurements for femur and tibia bone mineral content (BMC) and bone mineral density showed that the DHA-rich diets (HP5 and LP5) resulted in a significantly lower bone loss among the OVX rats at 12 weeks. Rats fed the LP diets displayed the lowest overall serum concentrations of the bone resorption biomarkers pyridinoline (Pyd) and deoxypyridinoline, whereas the bone formation marker osteocalcin was lowest in the HP groups. Regardless of the dietary PUFA content, DHA in the 5:1 diets (HP5 and LP5) preserved rat femur BMC in the absence of estrogen. This study indicates that the dietary ratio of n-6/n-3 PUFAs (LP5 and HP5) and bone tissue concentration of total long-chain n-3 PUFAs (DHA) minimize femur bone loss as evidenced by a higher BMC in OVX rats. These findings show that dietary DHA lowers the ratio of 18:2n-6 (linoleic acid)/n-3 in bone compartments and that this ratio in tissue correlates with reduced Pyd but higher bone alkaline phosphatase activity and BMC values that favor bone conservation in OVX rats.     

Cadmium-induced alterations in ocular trace elements

The present report demonstrates, for the first time, that feeding rats 50 ppm cadmium for just 7 wk results in detectable levels of cadmium in the eye of rats. Furthermore, these ocular cadmium concentrations affect significant alterations in the levels of the essential trace elements selenium, calcium iron, and copper in the eye. Rats were fed a low-selenium (<0.02 ppm selenium), high-copper basal diet (50 ppm copper) supplemented with 0, 0.1, and 0.5 ppm selenium. The animals were either untreated or treated with 50 ppm cadmium admixed with their feed. Cadmium treatment resulted in significant reductions (up to 50%) in ocular selenium. Furthermore, rats fed the basal diet and given 100 ppm cadmium via their feed for 6 wk exhibited a 69% reduction in the activity of the selenoenzyme, glutathione peroxidase, in the eye. Cadmium treatment also resulted in reductions of up to 50% in ocular calcium, irrespective of dietary selenium supplementation. Iron levels were increased by 30% in rats fed the low-selenium diet and decreased by as much as 40% in rats fed the selenium-supplemented diets, compared to animals fed identical levels of selenium without cadmium. Ocular copper levels were significantly increased only in rats fed the low-selenium diet and treated with cadmium. Ocular zinc levels were not significantly affected by dietary cadmium or selenium.     

Feeding Blueberry Diets to Young Rats Dose-Dependently Inhibits Bone Resorption through Suppression of RANKL in Stromal Cells

Previous studies have demonstrated that weanling rats fed AIN-93G semi-purified diets supplemented with 10% whole blueberry (BB) powder for two weeks beginning on postnatal day 21 (PND21) significantly increased bone formation at PND35. However, the minimal level of dietary BB needed to produce these effects is, as yet, unknown. The current study examined the effects of three different levels of BB diet supplementation (1, 3, and 5%) for 35 days beginning on PND25 on bone quality, and osteoclastic bone resorption in female rats. Peripheral quantitative CT scan (pQCT) of tibia, demonstrated that bone mineral density (BMD) and content (BMC) were dose-dependently increased in BB-fed rats compared to controls (P<0.05). Significantly increased bone mass after feeding 5% BB extracts was also observed in a TEN (total enteral nutrition) rat model in which daily caloric and food intake was precisely controlled. Expression of RANKL (receptor activator of nuclear factor-κB ligand) a protein essential for osteoclast formation was dose-dependently decreased in the femur of BB animals. In addition, expression of PPARγ (peroxisome proliferator-activated receptor γ) which regulates bone marrow adipogenesis was suppressed in BB diet rats compared to non-BB diet controls. Finally, a set of in vitro cell cultures revealed that the inhibitory effect of BB diet rat serum on RANKL expression was more profound in mesenchymal stromal cells compared to its effect on mature osteoblasts, pre-adipocytes and osteocytes. These results suggest that inhibition of bone resorption may contribute to increased bone mass during early development after BB consumption.     

Mineral supplementation of white wheat flour is necessary to maintain adequate mineral status and bone characteristics in rats

This experiment was designed to compare the effect of ingestion of a wheat flours on mineral status and bone characteristics in rats. White flour was tested either without further mineral supplementation or with Mg, Fe, Zn and Cu supplementation. The flour diets were compared to a control purified diet. Four groups of 10 male Wistar rats each were fed one of the experimental diets for 6 wk and mineral status and tissue retention as well as bone characteristics were determined. As expected, mineral intake, except for calcium, was significantly lesser in rats fed the white flour diet than in the other groups. The rats fed the white flour diet had the lowest food intake, weight gain, fecal excretion and intestinal fermentation. The most important result was that Mg and Fe status were drastically lower in rats fed the white flour diet than in those fed whole flour or control diets. The status of these both elements were significantly improved by the mineral supplementation of white flour. There were no major significant differences between mineral-supplemented white flour and whole flour groups in mineral status. Furthermore, bone mineral densities (total, metaphyseal and diphyseal) were significantly lower in rats fed white flour diet compared to the other diet groups, while no significant difference was observed between the mineral-supplemented white flour, whole flour or control diet groups. In conclusion, the present work shows clearly the importance of mineral-supplementation of white wheat flour to sustain an adequate intake of minerals. Our results indicate also that the whole wheat flour did not negatively alter mineral bioavailability, in comparison to mineral supplemented white flour. Clinical studies are still needed to confirm these rat results in human.     

Effect of treadmill exercise on bone mass in female rats.

Increasing peak bone mass at skeletal maturity, minimizing bone loss during middle age and after menopause, and increasing bone mass and preventing falls in advanced age are important measures for preventing osteoporotic fractures in women. Exercise has generally been considered to have a positive influence on bone health. This paper reviews the effects of treadmill exercise on bone in young, adult, ovariectomized, and osteopenic female rats. Treadmill exercise increases cortical and cancellous bone mass of the tibia as a result of increased bone formation and decreased bone resorption in young and adult rats. The increase in lumbar bone mass seems to be more significant when long-term exercise is applied. Treadmill exercise prevents cancellous bone loss at the tibia as a result of suppressed bone resorption in ovariectomized rats, and increases bone mass of the tibia and mechanical strength of the femur, as a result of suppressed bone resorption and increased bone formation in osteopenic rats after ovariectomy. Treadmill exercise transiently decreases the serum calcium level as a result of accumulation of calcium in bone, resulting in an increase in serum 1,25-dihydroxyvitamin D(3) level and a decrease in serum parathyroid hormone level. We conclude that treadmill exercise may be useful to increase bone mass in young and adult rats, prevent bone loss in ovariectomized rats, and increase bone mass and bone strength in osteopenic rats, especially in the long bones at weight-bearing sites. Treadmill exercise may have a positive effect on the skeleton in young, and adult, ovariectomized, and osteopenic female rats.     

The effect of purified compared with nonpurified diet on bone changes induced by hindlimb suspension of female rats

The purpose of this study was to compare the bone changes induced by unloading in rats fed different diets, because space flight studies use a semipurified diet, whereas space flight simulation studies typically use nonpurified diets. Female Sprague-Dawley rats were fed a purified American Institute of Nutrition (AIN) 93G diet or a standard nonpurified diet and kept ambulatory or subjected to unloading by hindlimb suspension (HLS) for 38 days. Bone mineral content (BMC), mechanical strength, and factors related to the diet that affect bone (i.e., urinary calcium excretion, estradiol, and corticosterone) were measured. Average food intakes (grams per day) differed for diets, but caloric intake (kilocalories per day) and the final body masses of treatment groups were similar. The HLS-induced decrease in femoral BMC was not statistically different for rats fed a nonpurified diet (-8.6%) compared with a purified AIN-93G diet (-11.4%). The HLS-induced decrease in femoral mechanical strength was not statistically different for rats fed a nonpurified diet (-24%) compared with a purified AIN-93G diet (-31%). However, bone lengths were decreased (P < 0.05) in rats fed a nonpurified diet compared with a purified diet. Plasma estradiol levels were lower (P < 0.05) in the HLS/AIN-93G group but similar in the HLS and ambulatory rats fed a nonpurified diet. Plasma estradiol was related to femoral BMC (r = 0.85, P < 0.01). Urinary calcium excretion was higher (P < 0.05) in rats fed a nonpurified diet than those fed a purified AIN-93G diet, which is consistent with the higher level of calcium in the nonpurified diet. Urinary corticosterone levels were higher (P < 0.05) in rats fed a nonpurified diet than rats fed the AIN-93G diet. Although the osteopenia induced by unloading was similar in both diet groups, there were differences in longitudinal bone growth, calcium excretion, plasma estradiol levels, and urinary corticosterone levels. Results indicate that the type of standard diet used is an important factor to consider when measuring bone end points.     

Effect of Dietary Nutrient Density on Small Intestinal Phosphate Transport and Bone Mineralization of Broilers during the Growing Period

A 2 × 4 factorial experiment was conducted to determine the effects of dietary nutrient density on growth performance, small intestinal epithelial phosphate transporter expression, and bone mineralization of broiler chicks fed with diets with different nutrient densities and nonphytate phosphorus (NPP) levels. The broilers were fed with the same starter diets from 0 to 21 days of age. In the grower phase (day 22 to 42), the broilers were randomly divided into eight groups according to body weight. Relatively high dietary nutrient density (HDND) and low dietary nutrient density (LDND) diets were assigned metabolic energy (ME) values of 3,150 and 2,950 kcal/kg, respectively. Crude protein and essential amino acid levels were maintained in the same proportion as ME to prepare the two diet types. NPP levels were 0.25%, 0.30%, 0.35%, and 0.40% of the diets. Results showed that a HDND diet significantly increased the body weight gain (BWG) of broilers and significantly decreased the feed conversion ratio and NPP consumed per BWG. HDND significantly decreased tibial P content of the broilers. Conversely, mRNA expression of NaPi-IIb and protein expression of calbindin were significantly increased in the intestine of broilers fed a HDND diet. HDND also increased vitamin D receptor (VDR) expression, especially at a relatively low dietary NPP level (0.25%). The mRNA expression of NaPi-IIa in the kidneys was significantly increased at a relatively low dietary NPP level (0.25%) to maintain P balance. Tibial P, calcium, and ash content were significantly decreased, as were calbindin and VDR expression levels in the intestine at a low NPP level. Therefore, HDND improved the growth rate of broilers and increased the expression of phosphate and calcium transporter in the small intestine, but adversely affected bone mineralization.     

Hippuric acid and 3-(3-hydroxyphenyl) propionic acid inhibit murine osteoclastogenesis through RANKL-RANK independent pathway

Nutritional factors influence bone development. Previous studies demonstrated that bone mass significantly increased with suppressed bone resorption in early life of rats fed with AIN-93G semi-purified diets supplemented with 10% whole blueberry (BB) powder for 2 weeks. However, the effects of increased phenolic acids in animal serum due to this diet on bone and bone resorption were unclear. This in vitro and in ex vivo study examined the effects of phenolic hippuric acid (HA) and 3-(3-hydroxyphenyl) propionic acid (3-3-PPA) on osteoclastic cell differentiation and bone resorption. We cultured murine osteoclast (macrophage) cell line, RAW 264.7 cells, and hematopoietic osteoclast progenitor cells (isolated from 4-week-old C57BL6/J mice) with 50 ng/ml of receptor activator of nuclear factor κ-Β ligand (RANKL). Morphologic studies showed decreased osteoclast number with treatment of 2.5% mouse serum from BB diet–fed animals compared with those treated with serum from standard casein diet–fed mice in both RAW 264.7 cell and primary cell cultures. HA and 3-3-PPA, but not 3–4-PPA, had dose-dependent suppressive effects on osteoclastogenesis and osteoclast resorptive activity in Corning osteo-assay plates. Signaling pathway analysis showed that after pretreatment with HA or 3-3-PPA, RANKL-stimulated increase of osteoclastogenic markers, such as nuclear factor of activated T-cells, cytoplasmic 1 and matrix metallopeptidase 9 gene/protein expression were blunted. Inhibitory effects of HA and 3-3-PPA on osteoclastogenesis utilized RANKL/RANK independent mediators. The study revealed that HA and 3-3-PPA significantly inhibited osteoclastogenesis and bone osteoclastic resorptive activity.