Skeletal effects of zinc deficiency in growing rats.

There is ample evidence that zinc plays an important role in bone metabolism and zinc deficiency has been implicated as a risk factor in the development of osteoporosis. It was the aim of the present study to investigate the skeletal effects of alimentary zinc deficiency in growing rats using quantitative bone histomorphometry. Twenty-four male Sprague Dawley rats with a mean initial body weight of 101 +/- 2 g were allocated in two groups of 12 rats each and had free access to a semi-synthetic, casein-based, zinc-deficient diet (0.76 mg zinc/kg) or to the same diet supplemented with 60 mg zinc per kg. All rats were sacrificed 42 days after the start of the experiment and the right distal femur was removed for bone histomorphometry. Relative to controls (+Zn), the zinc-deficient rats (-Zn) had a significantly lower body weight and about an 80% reduction in plasma and femur zinc concentration. The histomorphometric evaluation of the distal femoral metaphysis showed that zinc deficiency led to a 45% reduction (p < 0.01) in cancellous bone mass and to a deterioration of trabecular bone architecture, with fewer and thinner trabeculae. The osteopenia in -Zn rats was accompanied by significant reductions in osteoid perimeter (-31%, p < 0.05), osteoblast perimeter (-30%, p < 0.05), and osteoclast number (-38%, p < 0.01) relative to +Zn controls. We conclude that zinc deficiency induced low turnover osteopenia in femoral cancellous bone of growing rats. These results support the hypothesis that zinc deficiency during growth may impair the accumulation of maximal bone mass in humans; additionally, they suggest that zinc deficiency may play a role as a risk factor in the pathogenesis of osteoporosis.     

Moderate/subclinical calcium deficiency attenuates trabecular mass,microarchitecture and bone growth in growing rats

Adequate dietary calcium (Ca) intake is essential for bone accretion, peak bone mass (PBM) attainment, bone quality and strength during the mammalian growth period. Severe Ca deficiency during growing age results in secondary hyperparathyroidism (SHPT) and poor bone quality and strength. However, the impact of moderate Ca deficiency during rats early growth period on bone health and the reversibility with supplementing calcium later in adult life remains unclear. Female Sprague-Dawley (SD) rats (postnatal 28th day, P28) were initiated either with a moderate calcium-deficient diet (MCD, 0.25% w/w Ca) or a control diet (0.8% w/w Ca, control group) till P70. Thereafter, MCD rats were continued either with MCD diet or supplemented with calcium diet (0.8% w/w Ca, calcium supplemented group, CaS) till P150. Another group (control rats) were fed 0.8% w/w Ca containing diet from P28 till P150.MCD group, as compared to the control group, had significantly reduced serum ionized Ca and procollagen type 1 N-terminal propeptide (P1NP) at P70 while no significant change was observed in serum corrected Ca, inorganic phosphate (P), alkaline phosphatase (ALP), 25-hydroxy vitamin D [25(OH)D], intact parathyroid hormone (iPTH), and urinary C-terminal telopeptide of collagen 1 (CTX-1), Ca, and P. Femoral and tibial metaphysis in MCD rats had significantly reduced linear growth, cortical and trabecular volumetric BMD (vBMD), trabecular microarchitecture (BV/TV%, trabecular thickness, separation and number, structural model index and connectivity density), cortical thickness, and bone stiffness despite the absence of secondary hyperparathyroidism (SHPT). Continued MCD at P70–P150 results in persistence of compromised bone strength while calcium supplementation (CaS group) improved all the parameters related to bone strength and microarchitecture. Our results indicate that uncorrected moderate/subclinical calcium deficiency in growing rats can result in poor bone quality and strength despite the absence of SHPT. This finding could have relevance in children with poor calcium intake in childhood and adolescence.     

Bone and faecal minerals and scanning electron microscopic assessments of femur in rats fed phytic acid extract from sweet potato (<Emphasis Type="Italic">Ipomoea batatas</Emphasis>)

Phytic acid was extracted from sweet potato (Ipomoea batatas) and fed to Wistar rats with or without zinc for 3 weeks. Animals were then sacrificed and bone and faecal minerals were assessed. The ultra-structure of the bones was examined via scanning electron microscopy. Phytic acid extract or commercial phytic acid supplemented diets (D + Zn + PE or D + PE) displayed reduced bone calcium levels (101.27 ± 59.11 and 119.27 ± 45.36 g/kg) compared to the other test groups. Similarly, reduced calcium were observed in the control groups (D + Zn and D) fed formulated diets with or without zinc supplementation (213.14 ± 15.31 and 210 ± 6.88 g/kg) compared to the other test groups. The group fed supplemented commercial phytic acid diet (D + CP) demonstrated the lowest femur magnesium (3.72 ± 0.13 g/kg) while the group fed phytic acid extract supplementation (D + PE) recorded the highest level (4.84 ± 0.26 g/kg) amongst the groups. Femur iron was highest in the group fed commercial phytic acid supplemented diet (D + CP −115.74 ± 2.41 g/kg) compared to the other groups. Faecal magnesium levels were significantly higher in the two test groups fed phytic acid extract with or without zinc (D + Zn + PE or D + PE) compared to all other groups. All the groups which had phytic acid supplemented diets had significantly thinner bone in the trabecular region, compared to the groups fed formulated diet or zinc supplemented formulated diet (D or D + Zn). These observations suggest that the consumption of foods high in phytic acid may contribute to a reduction in the minerals available for essential metabolic processes in rats.     

CCAAT/enhancer binding protein β-deficiency enhances type 1 diabetic bone phenotype by increasing marrow adiposity and bone resorption

Bone loss in type 1 diabetes is accompanied by increased marrow fat, which could directly reduce osteoblast activity or result from altered bone marrow mesenchymal cell lineage selection (adipocyte vs. osteoblast). CCAAT/enhancer binding protein beta (C/EBPβ) is an important regulator of both adipocyte and osteoblast differentiation. C/EBPβ-null mice have delayed bone formation and defective lipid accumulation in brown adipose tissue. To examine the balance of C/EBPβ functions in the diabetic context, we induced type 1 diabetes in C/EBPβ-null (knockout, KO) mice. We found that C/EBPβ deficiency actually enhanced the diabetic bone phenotype. While KO mice had reduced peripheral fat mass compared with wild-type mice, they had 5-fold more marrow adipocytes than diabetic wild-type mice. The enhanced marrow adiposity may be attributed to compensation by C/EBPδ, peroxisome proliferator-activated receptor-γ2, and C/EBPα. Concurrently, we observed reduced bone density. Relative to genotype controls, trabecular bone volume fraction loss was escalated in diabetic KO mice (-48%) compared with changes in diabetic wild-type mice (-22%). Despite greater bone loss, osteoblast markers were not further suppressed in diabetic KO mice. Instead, osteoclast markers were increased in the KO diabetic mice. Thus, C/EBPβ deficiency increases diabetes-induced bone marrow (not peripheral) adipose depot mass, and promotes additional bone loss through stimulating bone resorption. C/EBPβ-deficiency also reduced bone stiffness and diabetes exacerbated this (two-way ANOVA P < 0.02). We conclude that C/EBPβ alone is not responsible for the bone vs. fat phenotype switch observed in T1 diabetes and that suppression of CEBPβ levels may further bone loss and decrease bone stiffness by increasing bone resorption.     

Combined Effects of Phytoestrogen Genistein and Silicon on Ovariectomy-Induced Bone Loss in Rat

This study was performed to evaluate the effect of concomitant supplementation of genistein and silicon on bone mineral density and bone metabolism-related markers in ovariectomized rat. Three-month-old Sprague Dawley female rats were subjected to bilateral ovariectomy (OVX) or sham surgery, and then the OVX rats were randomly divided into four groups: OVX-GEN, OVX-Si, OVX-GEN-Si, and OVX. Genistein and silicon supplementation was started immediately after OVX and continued for 10 weeks. In the OVX-GEN group, 5 mg genistein per gram body weight was injected subcutaneously. The OVX-Si group was given soluble silicon daily in demineralized water (Si 20 mg/kg body weight/day). The OVX-GEN-Si group was given subcutaneous injections of 5 mg genistein per gram body weight, at the same time, given soluble silicon daily (Si 20 mg/kg body weight/day). The results showed that the genistein supplementation in the OVX rats significantly prevented the loss of uterus weight; however, the silicon supplementation showed no effect on the uterus weight loss. The lumbar spine and femur bone mineral density was significantly decreased after OVX surgery; however, this decrease was inhibited by the genistein and/or silicon, and the BMD of the lumbar spine and femur was the highest in the OVX-GEN-Si-treated group. Histomorphometric analyses showed that the supplementation of genistein and/or silicon restored bone volume and trabecular thickness of femoral trabecular bone in the OVX group. Besides, the treatment with genistein and silicon for 10 weeks increased the serum levels of calcium and phosphorus in the OVX rats; serum calcium and serum phosphorus in the OVX-GEN-Si group were higher than those in the OVX-GEN and OVX-Si group (P < 0.05). At the same time, the treatment with genistein and/or silicon decreased serum alkaline phosphatase (ALP) and osteocalcin, which were increased by ovariectomy; serum ALP and osteocalcin in the OVX-GEN-Si group were lower than those in the OVX-GEN and OVX-Si groups (P < 0.05). The results above indicate that genistein and silicon have synergistic effects on bone formation in ovariectomized rats.     

Alfacalcidol prevents age-related bone loss and causes an atypical pattern of bone formation in aged male rats

The current study was designed to investigate the skeletal effects of alfacalcidol in aged rats. Eighteen-month-old male rats were treated with 0, 0.1, or 0.2 microg/kg/d of alfacalcidol by daily oral gavage, 5 days/week for 12 weeks. At the beginning of the treatments, one group of rats was euthanized to serve as a baseline control. At the end of the study, the second lumbar vertebrae and the right tibial diaphysess were processed for bone histomorphometric analysis. The fourth lumbar vertebrae were subjected to strength testing. The control group of rats at 21 months of age had decreased serum testosterone levels and decreased cancellous bone mass associated with increased bone turnover on the trabecular surface. The older rats had increased bone turnover on the endocortical surface and decreased bone formation on the periosteal surface compared with the 18-month group. In contrast, alfacalcidol treatment increased cancellous and cortical bone mass in aged male rats. Trabecular bone resorption was decreased whereas bone formation was maintained or increased in the rats treated with alfacalcidol. In addition, endocortical bone formation was decreased whereas periosteal bone formation was increased in the rats treated with alfacalcidol compared with vehicle-treated rats. Marrow trabecular bone area was increased by alfacalcidol treatment in tibial diaphyses. Furthermore, bone strength of the lumbar vertebral body was increased after alfacalcidol treatment. An atypical pattern of bone formation on endosteal bone surfaces was seen in the rats treated with alfacalcidol. The atypical bone formation is characterized by small, focal packets of newly formed bone on trabecular and endocortical bone surfaces. This gave the appearance of the formation of "bone buds" emanating from trabecular surfaces. These bony outgrowths were mineralized and demonstrated significant fluorochrome label indicating recent mineralization. Also, lamellae of the bony buds did not run parallel to those of the trabecular plate to which they are attached. Arrest lines presented in most of the "bone buds". In summary, alfacalcidol treatment increased cancellous and cortical bone mass and improved bone strength, resulting in the prevention of age-related bone loss in aged male rats. An atypical pattern of bone formation observed in this study may be a result of minimodeling based bone formation stimulated by alfacalcidol treatment.     

Vitamin D Supplementation Modulates Blood and Tissue Zinc, Liver Glutathione and Blood Biochemical Parameters in Diabetic Rats on a Zinc-Deficient Diet

Previous studies suggest a protective effect of vitamin D3 on zinc deficiency-induced insulin secretion and on pancreas β-cell function. The aim of this study was to investigate the effect of vitamin D on blood biochemical parameters, tissue zinc and liver glutathione in diabetic rats fed a zinc-deficient diet. For that purpose, Alloxan-induced diabetic rats were divided into four groups. The first group was fed a zinc-sufficient diet while the second group was fed a zinc-deficient diet. The third and fourth groups received zinc-sufficient or zinc-deficient diets plus oral vitamin D3 for 27 days. At the end of the experiment, blood, femur, pancreas, kidney and liver samples were taken from all rats. The serum, femur, pancreas, kidney and liver zinc concentrations, liver glutathione, serum alkaline phosphatase activity, daily body weight gain and food intake were lower in the zinc-deficient rats in comparison with those receiving adequate amounts of zinc. These values were increased in the zinc-deficient group that was supplemented with vitamin D3. The serum total cholesterol, triglycerides, total protein, urea, glutamate oxaloacetate transaminase, glutamate pyruvate transaminase and blood glucose values were higher in rats fed a zinc adequate diet, but their concentrations were decreased by vitamin D3 supplementation. The serum total protein levels were not changed by zinc deficiency and vitamin D3 supplementation. These results suggest that vitamin D3 modulates tissue zinc, liver glutathione and blood biochemical values in diabetic rats fed a zinc-deficient diet.     

Caspase-2 deficiency protects mice from diabetes-induced marrow adiposity

Type I (T1) diabetes is an autoimmune and metabolic disease associated with bone loss. Bone formation and density are decreased in T1-diabetic mice. Correspondingly, the number of TUNEL positive, dying osteoblasts increases in bones of T1-diabetic mice. Moreover, two known mediators of osteoblast death, TNFα and ROS, are increased in T1-diabetic bone. TNFα and oxidative stress are known to activate caspase-2, a factor involved in the extrinsic apoptotic pathway. Therefore, we investigated the requirement of caspase-2 for diabetes-induced osteoblast death and bone loss. Diabetes was induced in 16-week old C57BL/6 caspase-2 deficient mice and their wild type littermates and markers of osteoblast death, bone formation and resorption, and marrow adiposity were examined. Despite its involvement in extrinsic cell death, deficiency of caspase-2 did not prevent or reduce diabetes-induced osteoblast death as evidenced by a twofold increase in TUNEL positive osteoblasts in both mouse genotypes. Similarly, deficiency of caspase-2 did not prevent T1-diabetes induced bone loss in trabecular bone (BV/TV decreased by 30 and 50%, respectively) and cortical bone (decreased cortical thickness and area with increased marrow area). Interestingly, at this age, differences in bone parameters were not seen between genotypes. However, caspase-2 deficiency attenuated diabetes-induced bone marrow adiposity and adipocyte gene expression. Taken together, our data suggest that caspase-2 deficiency may play a role in promoting marrow adiposity under stress or disease conditions, but it is not required for T1-diabetes induced bone loss.     

Constitutively Elevated Blood Serotonin Is Associated with Bone Loss and Type 2 Diabetes in Rats

Reduced peripheral serotonin (5HT) in mice lacking tryptophan hydroxylase (TPH1), the rate limiting enzyme for 5HT synthesis, was reported to be anabolic to the skeleton. However, in other studies TPH1 deletion either had no bone effect or an age dependent inhibition of osteoclastic bone resorption. The role of 5HT in bone therefore remains poorly understood. To address this issue, we used selective breeding to create rat sublines with constitutively high (high-5HT) and low (low-5HT) platelet 5HT level (PSL) and platelet 5HT uptake (PSU). High-5HT rats had decreased bone volume due to increased bone turnover characterized by increased bone formation and mineral apposition rate, increased osteoclast number and serum C-telopeptide level. Daily oral administration of the TPH1 inhibitor (LX1032) for 6 weeks reduced PSL and increased the trabecular bone volume and trabecular number of the spine and femur in high-5HT rats. High-5HT animals also developed a type 2 diabetes (T2D) phenotype with increased: plasma insulin, glucose, hemoglobin A1c, body weight, visceral fat, β-cell pancreatic islets size, serum cholesterol, and decreased muscle strength. Serum calcium accretion mediated by parathyroid hormone slightly increased, whereas treatment with 1,25(OH)₂D₃ decreased PSL. Insulin reduction was paralleled by a drop in PSL in high-5HT rats. In vitro, insulin and 5HT synergistically up-regulated osteoblast differentiation isolated from high-5HT rats, whereas TPH1 inhibition decreased the number of bone marrow-derived osteoclasts. These results suggest that constitutively elevated PSL is associated with bone loss and T2D via a homeostatic interplay between the peripheral 5HT, bone and insulin.     

Amelioration of type I diabetes-induced osteoporosis by parathyroid hormone is associated with improved osteoblast survival

Type 1 diabetic osteoporosis results from impaired osteoblast activity and death. Therefore, anti-resorptive treatments may not effectively treat bone loss in this patient population. Intermittent parathyroid hormone (PTH) treatment stimulates bone remodeling and increases bone density in healthy subjects. However, PTH effects may be limited in patients with diseases that interfere with its signaling. Here, we examined the ability of 8 and 40 μg/kg intermittent PTH to counteract diabetic bone loss. PTH treatment reduced fat pad mass and blood glucose levels in non-diabetic PTH-treated mice, consistent with PTH-affecting glucose homeostasis. However, PTH treatment did not significantly affect general body parameters, including the blood glucose levels, of type 1 diabetic mice. We found that the high dose of PTH significantly increased tibial trabecular bone density parameters in control and diabetic mice, and the lower dose elevated trabecular bone parameters in diabetic mice. The increased bone density was due to increased mineral apposition and osteoblast surface, all of which are defective in type 1 diabetes. PTH treatment suppressed osteoblast apoptosis in diabetic bone, which could further contribute to the bone-enhancing effects. In addition, PTH treatment (40 μg/kg) reversed preexisting bone loss from diabetes. We conclude that intermittent PTH may increase type 1 diabetic trabecular bone volume through its anabolic effects on osteoblasts.     

Astragaloside IV prevents MPP+-induced SH-SY5Y cell death via the inhibition of Bax-mediated pathways and ROS production

Deficiency of zinc plays an important role in the pathogenesis of osteoporosis; however, the underlying mechanism is not well understood. Apoptosis of osteoblast causing the loss of bone mass is an important event in the osteoporosis. In this article, we investigated whether zinc deficiency would induce cell apoptosis in MC3T3-E1 cells and ask if it is involved in mitochondrial-mediated pathway. Significant increased apoptosis were observed in zinc deficiency group (ZnD: 5 μM TPEN and 1 μM zinc) compared with untreated control or zinc adequacy group (ZnA: 5 μM TPEN and 15 μM zinc). The mitochondrial membrane potential was strikingly reduced in ZnD group. Furthermore, we observed that the levels of Bax in mitochondria fraction and cyto c, AIF, and cleaved caspase-3/-9 in cytosol fraction were increased in ZnD group. We proposed that zinc deficiency would induce the translocation of Bax into mitochondria, which could lead to the reduction in mitochondrial membrane potential as well as the increase in mitochondrial membrane permeability. In addition, cyto c and AIF were released from mitochondria into the cytosol, which finally activated caspase-dependent and caspase-independent apoptosis processes in MC3T3-E1 cells. Our findings suggested that zinc deficiency is capable of inducing apoptosis through a mitochondria-mediated pathway in osteoblastic cells.     

缺锌对大鼠血液皮质醇和ACTH含量及大脑皮质NO合酶活性的影响

就缺锌对大鼠血液皮质醇和促肾上腺皮质激素（ACTH）含量以及大脑皮质NO合酶活性的影响进行了研究,生长大鼠随机分为3组,即缺锌组,对喂组和缺锌补锌组（先饲喂缺锌饲料21天后再补锌）,饲养实验的持续时间为35d。与对喂组比较,缺锌组大鼠血液中皮质醇含量显著升高,而血液ACTH浓度以及大脑皮质NO合酶活性明显降低,此结果提示锌可影响下丘脑－垂体一肾上腺皮质轴和NO合酶的代谢。     

Effect of zinc supplementation on type 2 diabetes parameters and liver metallothionein expressions in Wistar rats

Zinc is a trace metal and acts as an active component of various enzymes. Zinc deficiency has been suggested to be associated with the development of diabetes. The present study investigated the role of zinc supplementation on prevention of diabetic conditions. A double-disease model mimicking hyperlipidemia and type 2 diabetes was created by applying high-fat diet and streptozotocin (STZ) to Wistar rats. We demonstrated that zinc supplementation improved symptoms of diabetes such as polydipsia and increased serum level of high-density lipoprotein cholesterol, indicating that zinc supplementation has a potential beneficial effect on diabetic conditions. The level of maldondialdehyde (MDA), an oxidative stress marker, was reduced in liver by zinc supplementation in high fat-fed rats with or without STZ injection. Meanwhile, we observed an increase in the expression of metallothioneins (MTs) in liver of rats treated with zinc. This suggests that the induction of MTs in liver, which has been shown to be important in scavenging free radicals, could be one of the underlying mechanisms of zinc supplementation on reducing MDA levels in liver. Finally, we found that zinc levels in liver were increased while there was no change in serum zinc levels, indicating that local zinc level might be a critical factor for the induction of MTs. Also, the level of MTs could potentially be an index of zinc bioavailability. Taken together, these results suggest that both zinc and MT could play an important role in balancing nutrition and metabolism to prevent diabetic development.     

Dietary emu oil supplementation suppresses 5-fluorouracil chemotherapy-induced inflammation, osteoclast formation, and bone loss

Cancer chemotherapy can cause osteopenia or osteoporosis, and yet the underlying mechanisms remain unclear, and currently, no preventative treatments are available. This study investigated damaging effects of 5-fluorouracil (5-FU) on histological, cellular, and molecular changes in the tibial metaphysis and potential protective benefits of emu oil (EO), which is known to possess a potent anti-inflammatory property. Female dark agouti rats were gavaged orally with EO or water (1 ml·day(-1)·rat(-1)) for 1 wk before a single ip injection of 5-FU (150 mg/kg) or saline (Sal) was given. The treatment groups were H(2)O + Sal, H(2)O + 5-FU, EO + 5-FU, and EO + Sal. Oral gavage was given throughout the whole period up to 1 day before euthanasia (days 3, 4, and 5 post-5-FU). Histological analysis showed that H(2)O + 5-FU significantly reduced heights of primary spongiosa on days 3 and 5 and trabecular bone volume of secondary spongiosa on days 3 and 4. It reduced density of osteoblasts slightly and caused an increase in the density of osteoclasts on trabecular bone surface on day 4. EO supplementation prevented reduction of osteoblasts and induction of osteoclasts and bone loss caused by 5-FU. Gene expression studies confirmed an inhibitory effect of EO on osteoclasts since it suppressed 5-FU-induced expression of proinflammatory and osteoclastogenic cytokine TNFα, osteoclast marker receptor activator of nuclear factor-κB, and osteoclast-associated receptor. Therefore, this study demonstrated that EO can counter 5-FU chemotherapy-induced inflammation in bone, preserve osteoblasts, suppress osteoclast formation, and potentially be useful in preventing 5-FU chemotherapy-induced bone loss.     

Moderate Zinc Supplementation During Prolonged Steroid Therapy Exacerbates Bone Loss in Rats

The present study was conducted to understand the influence of zinc on bone mineral metabolism in prednisolone-treated rats. Disturbance in bone mineral metabolism was induced in rats by subjecting them to prednisolone treatment for a period of 8 weeks. Female rats aged 6–8 weeks weighing 150 to 200 g were divided into four treatment groups, viz., normal control, prednisolone-treated (40 mg/kg body weight orally, thrice a week), zinc-treated (227 mg/L in drinking water, daily), and combined prednisolone?+?zinc-treated groups. Parameters such as changes in mineral levels in the bone and serum, bone mineral density (BMD), bone mineral content (BMC), and bone 99m-technetium-labeled methylene diphosphonate (^99mTc-MDP) uptake were studied in various treatment groups. Prednisolone treatment caused an appreciable decrease in calcium levels both in the bone and serum and also in bone dry weight, BMC, and BMD in rats. Prednisolone-treated rats when supplemented with zinc showed further reduction in calcium levels, bone dry weight, BMD, and BMC. The study therefore revealed that moderate intake of zinc as a nutritional supplement during steroid therapy could enhance calcium deficiency in the body and accelerate bone loss.     

Effects of oral zinc and magnesium supplementation on serum thyroid hormone and lipid levels in experimentally induced diabetic rats

This study was designed to investigate the effects of oral zinc and magnesium supplementation on serum thyroid hormone and lipid levels in alloxan-induced diabetic rats. Thirty-two albino male rats, weighing 234±34 g, were divided into four experimental groups (control, diabetic, diabetic+zinc supplemented and diabetic+ magnesium supplemented). The experiment lasted for 60 d. The first 45 d of the experiment was the supplementation and last 15 d was the supplementation and diabetes-inducing period. Diabetic+zinc-supplemented and diabetic+magnesium-supplemented groups were given orally (by adding in their drinking water) 227 mg/L of zinc and 100 mg/kg body weight (bw) of magnesium, respectively throughout the experiment. Control and diabetic groups served as controls and did not receive zinc or magnesium supplementation. Diabetic, diabetic+zinc-supplemented, and diabetic+magnesium-supplemented groups were given a daily injection (ip) of 100 mg/kg bw of alloxan for 15 d starting on d 46 of the experiment. The control group was only injected with the same volume of isotonic NaCl as the diabetic group received. At the end of the of the experiment, rats in all four groups were fasted for 12 h and blood samples were taken from the heart under ether anesthesia for the determination of thyroid hormone, glucose, total cholesterol, and triglyceride concentrations. It was found that serum glucose, total cholesterol, and triglyceride concentrations were higher and serum T3 and T4 concentrations were lower in diabetic rats than those in the control group. Zinc supplementation did not change any parameter in diabetic rats. However, magnesium supplementation decreased the elevated total cholesterol and triglyceride concentrations of the diabetic rats to the control level. It was concluded that oral magnesium supplementation might decrease the diabetes-induced disturbances of lipid metabolism.     

Inflammation factors and element supplementation in cancer

The aim of the study was to evaluate the effect of dietary supplementation with chosen minerals (Zn, Se, Fe) on expression of selected cytokines (IL-1, IL-6, TNFα) in spleen of rats and on their concentrations in rat serum under inflammatory and pathological conditions obtained by implantation of prostate cancer cells (LnCaP). Serum levels of metabolites of arachidonic, eicosapentaenoic and linoleic acids (hydroxyeicosatetraenoic, hydroxyeicosapentaenoic and hydroxyoctadecadienoic acids, respectively), as compounds involved in inflammation and cancer development, were also investigated. Male rats were randomised into dietary groups supplemented with Zn, Se or Fe. Prostate cancer cells were implanted to some rats in each group.The study demonstrated that minerals supplemented with the diet may exert various effects on an organism. Selenium, zinc and iron influence pro-inflammatory cytokine expression, what leads to stimulation of inflammation. They also affect synthesis of arachidonic and linoleic acid metabolites that exert pro-inflammatory action and enable cancer development and metastasis.     

Adding zinc reduces bone strength of rats fed a low-calcium diet

This experiment examined skeletal effects of moderate zinc (Zn) supplementation of a low-calcium diet. Male weanling rats were fed experimental diets for about 4 wk. One diet was adequate (control), whereas two others were calcium-deficient, but otherwise adequate. One of the low-calcium (Ca) diets was supplemented with Zn. Dimensions, weight, mineral content, and mechanical properties of femurs were measured. Ca deficiency reduced bone mineral content and strength markedly. Adding Zn to the low-Ca diet further reduced bone strength and elasticity, compared with the unsupplemented low-Ca diet. When the Ca intake is low, possible benefits of Zn supplements should be weighed against risk of deterioration of mechanical properties of bone.     

Systemically administered bone morphogenetic protein-6 restores bone in aged ovariectomized rats by increasing bone formation and suppressing bone resorption

Although recombinant human bone morphogenetic proteins (BMPs) are used locally for treating bone defects in humans, their systemic effect on bone augmentation has not been explored. We have previously demonstrated that demineralized bone (DB) from ovariectomized (OVX) rats cannot induce bone formation when implanted ectopically at the subcutaneous site. Here we showed in vitro that 17beta-estradiol (E2) specifically induced expression of Bmp6 mRNA in MC3T3-E1 preosteoblastic cells and that bone extracts from OVX rats lack BMPs. Next we demonstrated that 125I-BMP-6 administered systemically accumulated in the skeleton and also restored the osteoinductive capacity of ectopically implanted DB from OVX rats. BMP-6 applied systemically to aged OVX rats significantly increased bone volume and mechanical characteristics of both the trabecular and cortical bone, the osteoblast surface, serum osteocalcin and osteoprotegerin levels, and decreased the osteoclast surface, serum C-telopeptide, and interleukin-6. E2 was significantly less effective, and was not synergistic with BMP-6. Animals that discontinued BMP-6 therapy maintained bone mineral density gains for another 12 weeks. BMP-6 increased in vivo the bone expression of Acvr-1, Bmpr1b, Smad5, alkaline phosphatase, and collagen type I and decreased expression of Bmp3 and BMP antagonists, chordin and cerberus. These results show, for the first time, that systemically administered BMP-6 restores the bone inductive capacity, microarchitecture, and quality of the skeleton in osteoporotic rats.     

Response of cortical and cancellous bones to mild calcium deficiency in young growing female rats: a bone histomorphometry study.

The purpose of the present study was to clarify the differences in the alterations of cellular activities of osteoblasts and osteoclasts, mineralization, and bone mass in cortical and cancellous bones of young growing rats with mild calcium deficiency. Twenty female Sprague-Dawley rats, 6 weeks of age, were randomized by the stratified method into two groups with 10 rats in each group: 0.5% (normal) calcium diet group and 0.1% (low) calcium diet group. After 10 weeks of feeding, bone histomorphometric analysis was performed on cancellous bone of the proximal tibia as well as cortical bone of the tibial shaft. Calcium deficiency increased eroded surface (ES/bone surface [BS]) and the number of osteoclast (N.Oc/BS) with an increase in osteoblast surface (ObS/BS), but decreased bone formation rate (BFR/BS) in cancellous bone. However, cancellous bone volume was preserved, while cortical bone area was decreased as a result of decreased periosteal bone gain and enlargement of the marrow cavity. These results suggest that short-term mild calcium deficiency in young growing female rats increased bone resorption by increasing osteoclastic recruitment, and suppressed mineralization followed by increased osteoblastic recruitment in cancellous bone, but cancellous bone loss was counteracted through redistribution of calcium from cortical bone to cancellous bone.