Effect of beta-alanyl-L-histidinato zinc on protein components in osteoblastic MC3T3-El cells: increase in osteocalcin, insulin-like growth factor-I and transforming growth factor-beta

The Role of Zinc in Bone Tissue Health and Regeneration-a Review

Zinc is a micronutrient of key importance for human health. An increasing number of studies indicate that zinc plays a significant role in bone tissue's normal development and maintaining homeostasis. Zinc is not only a component of bone tissue but is also involved in the synthesis of the collagen matrix, mineralization, and bone turnover. It has been demonstrated that zinc can stimulate runt-related transcription factor 2 (Runx2) and promote the differentiation of osteoblasts. On the other hand, zinc has been found to inhibit osteoclast-like cell formation and to decrease bone resorption by stimulating osteoclasts' apoptosis. Moreover, zinc regulates the RANKL/RANK/OPG pathway, thereby facilitating bone remodeling. To date, not all mechanisms of Zn activity on bone tissue are well understood and documented. The review aimed to present the current state of research on the role of zinc in bone tissue, its beneficial properties, and its effects on bone regeneration. Since calcium phosphates as bone substitute materials are increasingly enriched in zinc ions, the paper included an overview of research on the potential role of such materials in bone filling and regeneration.

Local zinc treatment enhances fracture callus properties in diabetic rats

The effects of locally applied zinc chloride (ZnCl₂ ) on early and late-stage parameters of fracture healing were evaluated in a diabetic rat model. Type 1 Diabetes has been shown to negatively impact mechanical parameters of bone as well as biologic markers associated with bone healing. Zinc treatments have been shown to reverse those outcomes in tests of nondiabetic and diabetic animals. This study is the first to assess the efficacy of a noncarrier mediated ZnCl₂ on bony healing in diabetic animals. This is a promising basic science approach which may lead to benefits for diabetic patients in the future. Treatment and healing were assessed through quantification of callus zinc, radiographic scoring, microcomputed tomography (µCT), histomorphometry, and mechanical testing. Local ZnCl₂ treatment increased callus zinc levels at 1 and 3 days after fracture (p ≤ 0.025). Femur fractures treated with ZnCl₂ showed increased mechanical properties after 4 and 6 weeks of healing. Histomorphometry of the ZnCl₂ -treated fractures found increased callus cartilage area at Day 7 (p = 0.033) and increased callus bone area at Day 10 (p = 0.038). In contrast, callus cartilage area was decreased (p < 0.01) after 14 days in the ZnCl₂ -treated rats. µCT analysis showed increased bone volume in the fracture callus of ZnCl₂ -treated rats at 6 weeks (p = 0.0012) with an associated increase in the proportion of µCT voxel axial projections (Z-rays) spanning the fracture site. The results suggest that local ZnCl₂ administration improves callus chondrogenesis leading to greater callus bone formation and improved fracture healing in diabetic rats.

Spatial Delivery of Triple Functional Nanoparticles via an Extracellular Matrix-Mimicking Coaxial Scaffold Synergistically Enhancing Bone Regeneration

It remains a major challenge to simultaneously achieve bone regeneration and prevent infection in the complex microenvironment of repairing bone defects. Here, we developed a novel ECM-mimicking scaffold by coaxial electrospinning to be endowed with multibiological functions. Lysophosphatidic acid (LPA) and zinc oxide (ZnO) nanoparticles were loaded into the poly-lactic-co-glycolic acid/polycaprolactone (PLGA/PCL, PP) sheath layer of coaxial nanofibers, and deferoxamine (DFO) nanoparticles were loaded into its core layer. The novel scaffold PP-LPA-ZnO/DFO maintained a porous nanofibrous architecture after incorporating three active nanoparticles, showing better physicochemical properties and eximious biocompatibility. In vitro studies showed that the bio-scaffold loaded with LPA nanoparticles had excellent cell adhesion, proliferation, and differentiation for MC3T3-E1 cells and synergistic osteogenesis with the addition of ZnO and DFO nanoparticles. Further, the PP-LPA-ZnO/DFO scaffold promoted tube formation and facilitated the expression of vascular endothelial markers in HUVECs. In vitro antibacterial studies against Escherichia Coli and Staphylococcus aureus demonstrated effective antibacterial activity of the PP-LPA-ZnO/DFO scaffold. In vivo studies showed that the PP-LPA-ZnO/DFO scaffold exhibited excellent biocompatibility after subcutaneous implantation and remarkable osteogenesis at 4 weeks post-implantation in the mouse alveolar bone defects. Importantly, the PP-LPA-ZnO/DFO scaffold showed significant antibacterial activity, prominent neovascularization, and new bone formation in the rat fenestration defect model. Overall, the spatially sustained release of LPA, ZnO, and DFO nanoparticles through the coaxial scaffold synergistically enhanced biocompatibility, osteogenesis, angiogenesis, and effective antibacterial properties, which is ultimately beneficial for bone regeneration. This project provides the optimized design of bone regenerative biomaterials and a new strategy for bone regeneration, especially in the potentially infected microenvironment.

Shareability of antibacterial and osteoblastic-proliferation activities of zinc-doped hydroxyapatite nanoparticles in vitro

Four types of zinc (Zn)-doped hydroxyapatite (Zn-HAp) nanoparticles were prepared using calcium nitrate tetrahydrate as an anti-sintering agent during calcination at 600°C for 1 hr, to prevent calcination-induced aggregation. The Zn content of the nanopowders was determined at 0, 4.3, 9.2, and 14.7% [Zn/(Ca + Zn) × 100] using inductively coupled plasma atomic emission spectroscopic analysis. Based on X-ray diffraction analysis, the products were shown to possess an apatite structure without other crystalline impurities. The cell parameters of Zn-HAp nanoparticles decreased with increasing of Zn content in the HAp structures. This tendency implies that Zn ions substituted for Ca sites in the HAp crystal lattices. To investigate the biological effects of Zn-HAp nanoparticles, cell proliferation activity of MC3T3-E1 osteoblasts and antibacterial activity against Escherichia coli were evaluated in vitro. According to the results obtained, Zn-HAp nanoparticles containing of 14.7% Zn ions was noticeable shown shareability of the conflicting activities at 0.1 mg/mL.

Zinc Pharmacotherapy for Elderly Osteoporotic Patients with Zinc Deficiency in a Clinical Setting

Although there have been reported associations between zinc and bone mineral density (BMD), no reports exist on the effect of zinc treatment in osteoporotic patients. Therefore, we investigated the efficacy and safety of zinc pharmacotherapy in Japanese elderly patients. The present investigation included 122 osteoporotic patients with zinc deficiency, aged ≥65 years, who completed 12 months of follow-up. In addition to standard therapy for osteoporosis in a clinical setting, the subjects received oral administration of 25 mg zinc (NOBELZIN^®, an only approved drug for zinc deficiency in Japan) twice a day. BMD and laboratory data including bone turnover markers were collected at 0 (baseline), 6, and 12 months of zinc treatment. Neither serious adverse effects nor incident fractures were seen during the observation period. Serum zinc levels were successfully elevated by zinc administration. BMD increased significantly from baseline at 6 and 12 months of zinc treatment. Percentage changes of serum zinc showed significantly positive associations with those of BMD. Bone formation markers rose markedly from the baseline values, whereas bone resorption markers displayed moderate or no characteristic changes. Additive zinc supplementation may contribute to BMD augmentation ensuing the prevention of fracture occurrence in elderly osteoporotic patients with zinc deficiency.

Synergistic effects of immunoregulation and osteoinduction of ds-block elements on titanium surface

Ds-block elements have been gaining increasing attention in the field of biomaterials modification, owing to their excellent biological properties, such as antibiosis, osteogenesis, etc. However, their function mechanisms are not well understood and conflicting conclusions were drawn by previous studies on this issue, which are mainly resulted from the inconsistent experimental conditions. In this work, three most widely used ds-block elements, copper, zinc, and silver were introduced on titanium substrate by plasma immersion ion implantation method to investigate the rule of ds-block elements in the immune responses. Results showed that the implanted samples could decrease the inflammatory responses compared with Ti sample. The trend of anti-inflammatory effects of macrophages on samples was in correlation with cellular ROS levels, which was induced by the implanted biomaterials and positively correlated with the number of valence electrons of ds-block elements. The co-culture experiments of macrophages and bone marrow mesenchymal stem cells showed that these two kinds of cells could enhance the anti-inflammation and osteogenesis of samples by the paracrine manner of PGE2. In general, in their steady states on titanium substrate (Cu2+, Zn2+, Ag), the ds-block elements with more valence electrons exhibit better anti-inflammatory and osteogenic effects. Moreover, molecular biology experiments indicate that the PGE2-related signaling pathway may contribute to the desired immunoregulation and osteoinduction capability of ds-block elements. These findings suggest a correlation between the number of valence electrons of ds-block elements and the relevant biological responses, which provides new insight into the selection of implanted ions and surface design of biomaterials.

Serum zinc levels and multiple health outcomes: Implications for zinc-based biomaterials

BACKGROUND

Zinc-based biomaterials, including biodegradable metal, nanoparticles, and coatings used in medical implants release zinc ions that may increase the whole-body and serum zinc concentrations. The impact of serum zinc concentrations on major health outcomes can provide insights for device design and clinical transformation of zinc-based biomaterials.

METHODS

This nationally representative cross-sectional study enrolled participants from the National Health and Nutrition Examination Survey (NHANES, 2011-2014) including 3607 participants. Using unadjusted and multivariate-adjusted logistic regression analyses, two-piecewise linear regression model with a smoothing function and threshold level analysis, we evaluated the associations between elevated serum zinc levels and major health outcomes.

RESULTS

Elevated serum zinc levels were significantly associated with an increase in total spine and total femur bone mineral density (BMD). Every 10 μg/dL increase was associated with a 1.12-fold increase in diabetes mellitus (DM) and 1.23-fold and 1.29-fold increase in cardiovascular diseases (CVD) and coronary heart disease (CHD), in participants with serum zinc levels ≥ 100 μg/dL. It had no significant linear or nonlinear associations with risk of fractures, congestive heart failure, heart attack, thyroid disease, arthritis, osteoarthritis, rheumatoid arthritis, dyslipidemia and cancer.

CONCLUSION

Serum zinc levels are significantly associated with increased BMD in the total spine and total femur, and risk of DM, and CVD/CHD among participants with serum zinc levels ≥100 μg/dL.

Anomalous in Vitro and in Vivo Degradation of Magnesium Phosphate Bioceramics: Role of Zinc Addition

In vitro and in vivo degradation behavior and biocompatibility of magnesium phosphate (MgP) bioceramics and the potential role of zinc (Zn) on degradation were compared. Samples were prepared by conventional solid-state sintering at 1200 °C for 2h. Zn-doped MgP (0.5 wt %) showed 50% less degradation than that of pure MgP after immersion into simulated body fluid (SBF) for 8 weeks. Osteoblast-like cell (MG-63) proliferation was evident in MgP ceramics, which was significantly enhanced upon Zn addition. Both Alamar Blue assay and Live/Dead imaging showed the highest cell attachment and proliferation for 0.5 wt % Zn-doped MgP. In vivo biocompatibility of these MgP ceramics were studied after implantation in the rabbit femur. The micro computed tomography (μ-CT) analysis showed that in vivo degradability increased with the increase in the Zn content which is in contradiction to in vitro degradability. Histological evaluation showed large influx of osteoclast cells to the implantation site for Zn-doped MgP samples compared to that of undoped MgP, which is the primary reason of increased degradability of these samples. After 90 days of implantation, large sections of 0.5 wt % Zn-doped MgP samples were replaced by newly formed bones. Fluorochrome labeling showed 78 ± 3% new bone formation for 0.5 wt % Zn-doped MgP ceramics compared to 56 ± 3% for pure MgP samples. Our findings suggest that the addition of Zn in MgP ceramics alters their sintering and degradation kinetics that leads to decreased in vitro degradation, however, when Zn-doped MgP ceramics were implanted in rabbits, higher degradability was observed due to lower Mg²⁺ ion concentration in the degradation media.

Local Zinc Chloride Release From a Calcium Sulfate Carrier Enhances Fracture Healing

BACKGROUND

This study examined the efficacy of calcium sulfate (CaSO4) as a carrier for intramedullary delivery of zinc chloride (ZnCl2) to treat fracture healing in a BB Wistar rat model. A non-carrier-mediated injection of 3.0 mg/kg of ZnCl2 has previously been shown to enhance fracture healing.

METHODS

A heterogeneous mixture of ZnCl2 and CaSO4 was administered into the intramedullary femoral canal and a mid-diaphyseal femur fracture was created unilaterally. Early and late parameters of fracture healing were assessed using biomechanical testing, radiographic scoring, quantitative histomorphometry (for percentage of new cartilage and bone within the fracture callus), and long-term histologic evaluation.

RESULTS

Fractures treated with 1.0 mg/kg of ZnCl2/CaSO4 demonstrated a significantly higher maximum torque to failure compared with both CaSO4 (P = 0.048) and saline (P = 0.005) controls at 4 weeks postfracture (396.4 versus 251.3 versus 178.7 N mm, respectively). Statistically significant increases in torsional rigidity, effective shear modulus, and effective shear stress were also found, as well as a 3.5 times increase in radiographic score (based on bone union). Histologic examination of the fracture callus indicated enhanced chondrogenesis at day 14 postfracture, with increased percent cartilage for the ZnCl2/CaSO4 group compared with saline (P = 0.0004) and CaSO4 (P = 0.0453) controls. Long-term radiographic and histologic evaluation revealed no abnormal bone formation or infection up to 12 weeks postoperatively.

CONCLUSIONS

The effective dose of ZnCl2 augmentation for the enhancement of fracture healing in rats was reduced 3-fold in this study compared with previous findings. Furthermore, CaSO4 acted synergistically with ZnCl2 to increase the mechanical strength and stability at the fracture site.

Diosmectite-zinc oxide composite improves intestinal barrier restoration and modulates TGF-β1, ERK1/2, and Akt in piglets after acetic acid challenge

The present study evaluated the beneficial effect of diosmectite-zinc oxide composite (DS-ZnO) on improving intestinal barrier restoration in piglets after acetic acid challenge and explored the underlying mechanisms. Twenty-four 35-d-old piglets (Duroc × Landrace × Yorkshire), with an average weight of 8.1 kg, were allocated to 4 treatment groups. On d 1 of the trial, colitis was induced via intrarectal injection of acetic acid (10 mL of 10% acetic acid [ACA] solution for ACA, DS-ZnO, and mixture of diosmectite [DS] and ZnO [DS+ZnO] groups) and the control group was infused with saline. Twenty-four hours after challenged, piglets were fed with the following diets: 1) control group (basal diet), 2) ACA group (basal diet), 3) DS-ZnO group (basal diet supplemented with DS-ZnO), and 4) DS+ZnO group (mixture of 1.5 g diosmectite [DS]/kg and 500 mg Zn/kg from ZnO [equal amount of DS and ZnO in the DS-ZnO treatment group]). On d 8 of the trial, piglets were sacrificed. The results showed that DS-ZnO supplementation improved (P < 0.05) ADG, ADFI, and transepithelial electrical resistance and decreased (P < 0.05) fecal scores, crypt depth, and fluorescein isothiocyanate-dextran 4 kDa (FD4) influx as compared with ACA group. Moreover, DS-ZnO increased (P < 0.05) occludin, claudin-1, and zonula occluden-1 expressions; reduced (P < 0.05) caspase-9 and caspase-3 activity and Bax expression; and improved (P < 0.05) Bcl2, XIAP, and PCNA expression. Diosmectite-zinc oxide composite supplementation also increased (P < 0.05) TGF-β1 expression and ERK1/2 and Akt activation. These results suggest that DS-ZnO attenuates the acetic acid-induced colitis by improving mucosa barrier restoration, inhibiting apoptosis, and improving intestinal epithelial cells proliferation and modulation of TGF-β1 and ERK1/2 and Akt signaling pathway.

Effect of Zinc Supplementation on GH, IGF1, IGFBP3, OCN, and ALP in Non-Zinc-Deficient Children

OBJECTIVE

Because most publications on growth and development deal with children with zinc deficiency, we decided to study the effects of this micronutrient on the secretion of growth hormone (GH), insulin-like growth factor 1 (IGF1), insulin-like growth factor binding protein 3 (IGFBP3), osteocalcin (OCN), and alkaline phosphatase (ALP) in healthy and eutrophic children. This study is original because the methodology was unique.

METHODS

Forty schoolchildren participated in the study, 17 females and 23 males, aged 8 and 9 years. The study was carried out during a 3-month period. It was characterized as a triple-blind randomized controlled trial. The children were divided in a control group (20 schoolchildren using 10% sorbitol) and experimental group (20 schoolchildren using zinc). All were submitted to oral zinc supplementation (10 mg Zn/day) and venous zinc administration (0.06537 mg Zn/kg of body weight). Blood samples were collected at 0, 60, 120, 180, and 210 min. All schoolchildren were also submitted to anthropometric, clinical, and dietetic assessments as well as biochemistry analyses.

RESULTS

Oral zinc supplementation in the experimental group (1) stimulated an increase in the consumption of protein and fat (p = 0.0007, p < 0.0001, p < 0.0001, respectively), (2) increased basal serum zinc (p < 0.0001), (3) increased plasma ALP (p = 0.0270), and (4) showed a positive correlation for IGF1, IGFBP3, and OCN, comparing before and after oral zinc supplementation (p = 0.0011, p < 0.0001, p < 0.0446, respectively). During zinc administration, plasma IGF1 and IGFBP3 increased significantly in the experimental group (p = 0.0468, p < 0.0001, respectively). Plasma GH increased in the experimental group but without statistical difference comparing before and after oral zinc supplementation.

CONCLUSIONS

Zinc supplementation stimulated an increase in the consumption of some macronutrients and basal serum zinc and improved plasma alkaline phosphatase levels. Zinc administration increased hormones of the GH-IGF1 system.

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 ((99m)Tc-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.

Zinc oxide influences mitogen-activated protein kinase and TGF-β1 signaling pathways, and enhances intestinal barrier integrity in weaned pigs

Weaning is the most significant event in the life of pigs and is always related with intestinal disruption. Although it is well known that zinc oxide (ZnO) exerts beneficial effects on the intestinal barrier, the mechanisms underlying these effects have not yet been fully elucidated. We examined whether ZnO protects the intestinal barrier via mitogen-activated protein kinases and TGF-β1 signaling pathways. Twelve barrows weaned at 21 d of age were randomly assigned to two treatments (0 verus 2200 mg Zn/kg from ZnO) for 1 wk. The results showed that supplementation with ZnO increased daily gain and feed intake, and decreased postweaning scour scores. ZnO improved intestinal morphology, as indicated by increased villus height and villus height:crypt depth ratio, and intestinal barrier function, indicated by increased transepithelial electrical resistance and decreased mucosal-to-serosal permeability to 4-ku FITC dextran. ZnO decreased the ratios of the phosphorylated to total JNK and p38 (p-JNK/JNK and p-p38/p38), while it increased the ratio of ERK (p-ERK/ERK). Supplementation with ZnO increased intestinal TGF-β1 expression. The results indicate that supplementation with ZnO activates ERK ½, and inhibits JNK and p38 signaling pathways, and increases intestinal TGF-β1 expression in weaned pigs.

Local ZnCl2 accelerates fracture healing

This study evaluated the effect of local zinc chloride (ZnCl2 ), an insulin mimetic agent, upon the early and late parameters of fracture healing in rats using a standard femur fracture model. Mechanical testing, radiographic scoring, histomorphometry, qualitative histological scoring, PCNA immunohistochemistry, and local growth factor analysis were performed. Fractures treated with local ZnCl2 possessed significantly increased mechanical properties compared to controls at 4 weeks post fracture. The radiographic scoring analysis showed increased cortical bridging at 4 weeks in the 1.0 (p=0.0015) and 3.0 (p<0.0001) mg/kg ZnCl2 treated groups. Histomorphometry of the fracture callus at day 7 showed 177% increase (p=0.036) in percent cartilage and 133% increase (p=0.002) in percent mineralized tissue with local ZnCl2 treatment compared to controls. Qualitative histological scoring showed a 2.1× higher value at day 7 in the ZnCl2 treated group compared to control (p = 0.004). Cell proliferation and growth factors, VEGF and IGF-I, within fracture calluses treated with local ZnCl2 were increased at day 7. The results suggest local administration of ZnCl2 increases cell proliferation, causing increased growth factor production which yields improved chondrogenesis and endochondral ossification. Ultimately, these events lead to accelerated fracture healing as early as 4 weeks post fracture.

SiO2 and ZnO dopants in three-dimensionally printed tricalcium phosphate bone tissue engineering scaffolds enhance osteogenesis and angiogenesis in vivo

Calcium phosphate (CaP) scaffolds with three-dimensionally-interconnected pores play an important role in mechanical interlocking and biological fixation in bone implant applications. CaPs alone, however, are only osteoconductive (able to guide bone growth). Much attention has been given to the incorporation of biologics and pharmacologics to add osteoinductive (able to cause new bone growth) properties to CaP materials. Because biologics and pharmacologics are generally delicate compounds and also subject to increased regulatory scrutiny, there is a need to investigate alternative methods to introduce osteoinductivity to CaP materials. In this study silica (SiO2) and zinc oxide (ZnO) have been incorporated into three-dimensional printed β-tricalcium phosphate (β-TCP) scaffolds to investigate their potential to trigger osteoinduction in vivo. Silicon and zinc are trace elements that are common in bone and have also been shown to have many beneficial properties, from increased bone regeneration to angiogenesis. Implants were placed in bicortical femur defects introduced to a murine model for up to 16 weeks. The addition of dopants into TCP increased the capacity for new early bone formation by modulating collagen I production and osteocalcin production. Neovascularization was found to be up to three times more than the pure TCP control group. The findings from this study indicate that the combination of SiO2 and ZnO dopants in TCP may be a viable alternative to introducing osteoinductive properties to CaPs.

IGF-1, the cross road of the nutritional, inflammatory and hormonal pathways to frailty

The decline in functional capacity is a heterogeneous phenomenon in the elderly. An accelerated ageing determines a frail status. It results in an increased vulnerability to stressors for decreased physiological reserves. The early identification of a frail status is essential for preventing loss of functional capacity, and its clinical consequences. Frailty and mobility limitation result from an interplay of different pathways including multiple anabolic deficiency, inflammation, oxidative stress, and a poor nutritional status. However, the age-related decline in insulin-like growth factor 1 (IGF-1) bioactivity deserves special attention as it could represent the ideal crossroad of endocrine, inflammatory, and nutritional pathways to frailty. Several minerals, namely magnesium, selenium, and zinc, appear to be important determinants of IGF-1 bioactivity. This review aims to provide an overview of the potential usefulness of nutrients modulating IGF-1 as potential therapeutic targets in the prevention of mobility limitation occurring in frail older subjects.

In vitro and in vivo evaluation of zinc-modified ca-si-based ceramic coating for bone implants

The host response to calcium silicate ceramic coatings is not always favorable because of their high dissolution rates, leading to high pH within the surrounding physiological environment. Recently, a zinc-incorporated calcium silicate-based ceramic Ca2ZnSi2O7 coating, developed on a Ti-6Al-4V substrate using plasma-spray technology, was found to exhibit improved chemical stability and biocompatibility. This study aimed to investigate and compare the in vitro response of osteoblastic MC3T3-E1 cells cultured on Ca2ZnSi2O7 coating, CaSiO3 coating, and uncoated Ti-6Al-4V titanium control at cellular and molecular level. Our results showed Ca2ZnSi2O7 coating enhanced MC3T3-E1 cell attachment, proliferation, and differentiation compared to CaSiO3 coating and control. In addition, Ca2ZnSi2O7 coating increased mRNA levels of osteoblast-related genes (alkaline phosphatase, procollagen α1(I), osteocalcin), insulin-like growth factor-I (IGF-I), and transforming growth factor-β1 (TGF-β1). The in vivo osteoconductive properties of Ca2ZnSi2O7 coating, compared to CaSiO3 coating and control, was investigated using a rabbit femur defect model. Histological and histomorphometrical analysis demonstrated new bone formation in direct contact with the Ca2ZnSi2O7 coating surface in absence of fibrous tissue and higher bone-implant contact rate (BIC) in the Ca2ZnSi2O7 coating group, indicating better biocompatibility and faster osseointegration than CaSiO3 coated and control implants. These results indicate Ca2ZnSi2O7 coated implants have applications in bone tissue regeneration, since they are biocompatible and able to osseointegrate with host bone.

Synergistic or antagonistic effect of MTE plus TF or icariin from Epimedium koreanum on the proliferation and differentiation of primary osteoblasts in vitro

3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide test and alkaline phosphatase activity assay were employed to assess the effects of mixed trace elements including Zn(2+), Ca(2+), and Mn(2+) plus total flavonoids or icariin from Epimedium koreanum on the proliferation and differentiation of primary osteoblasts in vitro. The results indicated that icariin (0.1, 1, and 10 μmol/L) and total flavonoids (0.06, 0.6, and 6 μg/mL) inhibited the proliferation and promoted the differentiation of primary osteoblasts. Mixed trace elements including Zn(2+), Ca(2+), and Mn(2+) (0.1, 1, and 10 μmol/L) inhibited the proliferation and promoted the differentiation at 0.1 and 1 μmol/L, but inhibited the differentiation at 10 μmol/L. The effects of mixed trace elements including Zn(2+), Ca(2+), and Mn(2+) plus total flavonoids or icariin from E. koreanum on the proliferation and differentiation of primary osteoblasts in vitro are complicated, and both synergistic and antagonistic effects are generated. The results suggest that there may be a potential cooperative action between flavonoids and trace metal elements on the proliferation and differentiation of primary osteoblasts by forming metal complexes. The combination model between flavonoids and trace metal elements is a pivotal factor for switching the biological effects from toxicity to activity, from damage to protection.

Role of nutritional zinc in the prevention of osteoporosis

Zinc is known as an essential nutritional factor in the growth of the human and animals. Bone growth retardation is a common finding in various conditions associated with dietary zinc deficiency. Bone zinc content has been shown to decrease in aging, skeletal unloading, and postmenopausal conditions, suggesting its role in bone disorder. Zinc has been demonstrated to have a stimulatory effect on osteoblastic bone formation and mineralization; the metal directly activates aminoacyl-tRNA synthetase, a rate-limiting enzyme at translational process of protein synthesis, in the cells, and it stimulates cellular protein synthesis. Zinc has been shown to stimulate gene expression of the transcription factors runt-related transcription factor 2 (Runx2) that is related to differentiation into osteoblastic cells. Moreover, zinc has been shown to inhibit osteoclastic bone resorption due to inhibiting osteoclast-like cell formation from bone marrow cells and stimulating apoptotic cell death of mature osteoclasts. Zinc has a suppressive effect on the receptor activator of nuclear factor (NF)-kappaB ligand (RANKL)-induced osteoclastogenesis. Zinc transporter has been shown to express in osteoblastic and osteoclastic cells. Zinc protein is involved in transcription. The intake of dietary zinc causes an increase in bone mass. beta-Alanyl-L: -histidinato zinc (AHZ) is a zinc compound, in which zinc is chelated to beta-alanyl-L: -histidine. The stimulatory effect of AHZ on bone formation is more intensive than that of zinc sulfate. Zinc acexamate has also been shown to have a potent-anabolic effect on bone. The oral administration of AHZ or zinc acexamate has the restorative effect on bone loss under various pathophysiologic conditions including aging, skeletal unloading, aluminum bone toxicity, calcium- and vitamin D-deficiency, adjuvant arthritis, estrogen deficiency, diabetes, and fracture healing. Zinc compounds may be designed as new supplementation factor in the prevention and therapy of osteoporosis.

Does promoter methylation of the SLC30A5 (ZnT5) zinc transporter gene contribute to the ageing-related decline in zinc status?

A decline in Zn status with ageing may contribute to the development of frailty, including impaired immune function, and increased incidence of age-related degenerative diseases. This decline may be a result of reduced dietary Zn intake and/or impaired Zn absorption in the gut. The Zn transporter ZnT5 may play a key role in the absorption of dietary Zn. The corresponding gene (SLC30A5) has a CpG island in its promoter region, so could be regulated by epigenetic mechanisms. It is hypothesised that methylation of the SLC30A5 promoter region is increased with age and that a resulting reduction in ZnT5 expression contributes to the decline in Zn status observed with ageing. This hypothesis has been addressed through (1) studies of effects of SLC30A5 promoter methylation on gene expression in vitro and (2) in vivo measurements of the DNA methylation status of this gene domain. It has been established in vitro that methylation of the human SLC30A5 promoter region results in reduced expression of an associated reporter gene. Second, this gene region shows variable levels of methylation in vivo. Correlation between the level of methylation at this locus and age would support the hypothesis that age-related hypermethylation of this region has the potential to modulate dietary Zn absorption. This premise is being investigated by analysis of additional samples from a human adult cohort to test the hypothesis that methylation of the SLC30A5 promoter region contributes to the age-related decline in Zn status.

Zinc intake and biochemical markers of bone turnover in type 1 diabetes

OBJECTIVE

To examine the relationship between Zn nutritive status and biochemical markers of bone turnover in type 1 diabetes.

RESEARCH DESIGN AND METHODS

Serum osteocalcin, urine N-telopeptides, and dietary intake data, obtained by 3-day food records, were assessed for 66 individuals with type 1 diabetes.

RESULTS

Zn intake correlated with osteocalcin in the group overall (r = 0.48; P < 0.001) but not with N-telopeptides. Examined by sex, both Zn and osteocalcin correlated for men (r = 0.57; P < 0.001), but the correlation did not reach statistical significance for women (r = 0.34; P = 0.09). A direct-entry linear regression model with osteocalcin as the dependent variable was performed. Duration, sex, A1C, insulin use per kilogram, total calorie intake, and Zn intake were entered as potential independent variables. The model was statistically significant (R(2) = 0.32; P < 0.01). Zn intake (P < 0.001), however, was the only independent correlate of osteocalcin.

CONCLUSIONS

This study provides evidence of a positive relationship between Zn intake and osteocalcin in type 1 diabetes.

Genistein and zinc synergistically stimulate apoptotic cell death and suppress RANKL signaling-related gene expression in osteoclastic cells

The effects of the combination of genistein and zinc, which have an anabolic effect on bone metabolism, on osteoclastic cells in mouse marrow culture system in vitro was investigated. The macrophage colony-stimulating factor (M-CSF)-dependent bone marrow macrophages were cultured in the presence of M-CSF (10 ng/ml) and receptor activator of nuclear factor kappaB (NF-kB) ligand (RANKL; 50 ng/ml) for 4 days. The osteoclastic cells formed were further cultured in medium containing either vehicle, genistein, zinc sulfate (zinc), or genistein plus zinc with or without M-CSF (10 ng/ml) and RANKL (50 ng/ml) for 24 or 72 h. The number of osteoclastic cells was significantly decreased with culture of genistein (10(-6) M) plus zinc (10(-5) M) in presence or absence of M-CSF and RANKL for 24 or 72 h as compared with the value for genistein or zinc alone. Agarose gel electrophoresis showed the presence of low-molecular weight deoxyribonucleic acid (DNA) fragments of adherent cells cultured with genistein (10(-6) M) plus zinc (10(-5) M) for 24 or 72 h, indicating that the combination of two chemicals induces apoptotic cell death. Such an effect was not seen in the case of each chemical. Genistein plus zinc-induced decrease in osteoclastic cells were significantly inhibited in the presence of caspase-3 inhibitor (10(-8) or 10(-7) M). Culture with genistein (10(-6) M) plus zinc (10(-5) M) for 72 h caused a significant increase in caspase-3 mRNA expression in the presence or absence of M-CSF and RANKL as compared with the value for each chemical alone. Genistein plus zinc-induced increase in caspase-3 mRNA expression was completely inhibited in the presence of cycloheximide (10(-7) M), an inhibitor of protein synthesis, or 5, 6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB; 10(-6) M), an inhibitor of transcription activity. The mRNA expression of tartrate-resistant acid phosphatase (TRACP) or cathepsin K was significantly decreased with culture of genistein plus zinc in the presence of M-CSF and RANKL for 72 h as compared with genistein or zinc alone. Nuclear factor of activated T cells c1 (NFATc1) mRNA expression was significantly decreased with culture of genistein plus zinc in the presence of M-CSF and RANKL for 24 or 72 h as compared with each chemical alone, while NF-kB mRNA expression was significantly changed. This study demonstrates that the combination of genistein and zinc has potent stimulatory effects on apoptotic cell death and suppressive effects on osteoclastic cell function.

Effects of copper on bone component in the femoral tissues of rats: anabolic effect of zinc is weakened by copper

The effects of copper on biochemical components in the femoral-diaphyseal (cortical bone) and -metaphyseal (trabecullar bone) tissues of rats in vivo and in vitro were investigated. Rats were orally administered copper sulfate (50, 100, or 200 microg Cu/100 g body weight) once daily for 7 d. Calcium content in the diaphyseal and metaphyseal tissues was significantly decreased with the administration of copper (200 microg/100 g), while alkaline phosphatase activity in these tissues was not significantly changed by copper administration. The diaphyseal DNA content was significantly decreased with the administration of copper (50, 100, or 200 microg/100 g). Moreover, the femoral-diaphyseal and -metaphyseal tissues were cultured for 48 h in serum-free medium containing either vehicle or copper (10(-7) - 10(-4) M). Culture with copper (10(-7) - 10(-4) M) caused a significant decrease in alkaline phosphatase activity in the diaphyseal and metaphyseal tissues, while calcium and DNA contents in these tissues were not significantly changed. Culture with parathyroid hormone [PTH (1-34); 10(-7) M], a bone-resorbing factor, caused a significant decrease in calcium content in the diaphyseal and metaphyseal tissues. This decrease was completely inhibited in the presence of copper (10(-6) or 10(-5) M). Culture with zinc sulfate (10(-4) M) caused a significant increase in calcium content and alkaline phosphatase activity in the diaphyseal and metaphyseal tissues. The effects of zinc (10(-4) M) in increasing femoral calcium content and alkaline phosphatase activity were not seen in the presence of cycloheximide (10(-6) M), an inhibitor of protein synthesis, suggesting that the effects of zinc are involved in newly synthesized protein components. The effects of zinc in increasing calcium content and alkaline phosphatase activity in the diaphyseal and metaphyseal tissues were significantly weakened in the presence of copper (10(-4) M). The inhibitory effects of copper were further enhanced in the presence of cycloheximide. This study demonstrates that supplementation with copper in adequate copper nutrition does not have anabolic effects on bone components in vivo and in vitro and that copper weakens the anabolic effects of zinc in vitro.

Oral Administration in Combination with Zinc Enhances .BETA.-Cryptoxanthin-Induced Anabolic Effects on Bone Components in the Femoral Tissues of Rats in Vivo

The effects of combined beta-cryptoxanthin and zinc on bone components in the femoral-diaphyseal (cortical bone) and -metaphyseal (trabecular bone) tissues of rats in vivo were investigated. Rats were orally administered either vehicle, beta-cryptoxanthin (5 or 10 microg/100 g body weight), zinc sulfate (0.1 or 0.5 mg Zn/100 g), or their combination once a day for 7 d. Calcium content, alkaline phosphatase activity, and DNA content in the femoral-diaphyseal tissues was not significantly altered by the administration of beta-cryptoxanthin (5 microg/100 g) or zinc (0.1 or 0.5 mg/100 g). Combined administration of beta-cryptoxanthin (5 microg/100 g) and zinc (0.1 or 0.5 mg/100 g) caused a synergistic increase in calcium content, alkaline phosphatase activity, and DNA content in the diaphyseal tissues. The effect of beta-cryptoxanthin (5 or 10 microg/100 g) in increasing calcium and DNA contents in the metaphyseal tissues was significantly enhanced by the combined administration of zinc (0.1 or 0.5 mg/100 g), but did not have a significant effect on the metaphyseal components. The metaphyseal alkaline phosphatase activity was markedly increased by the combination of beta-cryptoxanthin (5 microg/100 g) and zinc (0.1 or 0.5 mg/100 g). This study demonstrates that the oral administration of the combination of zinc at lower doses synergistically enhances beta-cryptoxanthin-induced anabolic effects on bone components in the femoral tissues of rats in vivo.

Synergistic effect of beta-cryptoxanthin and zinc sulfate on the bone component in rat femoral tissues in vitro: the unique anabolic effect with zinc

The effect of the combination of beta-cryptoxanthin and zinc sulfate (zinc) on bone components in the femoral-diaphyseal and -metaphyseal tissues of young rats in vitro was investigated. Bone tissues were cultured for 48 h in a serum-free Dulbecco's modified Eagle's medium containing either vehicle, beta-cryptoxanthin (10(-9)-10(-7) M) or zinc sulfate (10(-6)-10(-4) M). The presence of beta-cryptoxanthin (10(-9) M) or zinc (10(-6) M) did not have a significant effect on calcium content in the femoral-diaphyseal or -metaphyseal tissues. However, culture which combined beta-cryptoxanthin (10(-9) M) and zinc (10(-6) M) caused a significant increase in calcium content in the femoral-diaphyseal and -metaphyseal tissues. Such an effect was not observed by the combination of beta-cryptoxanthin (10(-9) M) plus genistein (10(-6) M) or menaquinone-7 (10(-6) M), or zinc (10(-6) M) plus genistein (10(-6) M) or menaquinone-7 (10(-6) M). Also, the combination of beta-cryptoxanthin (10(-9) M) plus zinc (10(-6) M) caused a remarkable increase in alkaline phosphatase activity and deoxyribonucleic acid (DNA) in the femoral-diaphyseal and -metaphyseal tissues, while their application alone did not have an effect on the enzyme activity or DNA content in the femoral tissues. The effect of the combination of beta-cryptoxanthin (10(-9) M) plus zinc (10(-6) M) in increasing calcium content, alkaline phosphatase activity, and DNA content in the femoral-diaphyseal and -metaphyseal tissues was completely prevented in the presence of cycloheximide (10(-6) M), an inhibitor of protein synthesis, or 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DBR), an inhibitor of transcriptional activity. This study demonstrates that the combination of beta-cryptoxanthin and zinc at a lower concentration has a synergistic effect on bone components in vitro.

Role of zinc in regulation of protein tyrosine phosphatase activity in osteoblastic MC3T3-E1 cells: zinc modulation of insulin-like growth factor-I's effect

Zinc, an essential trace element, has been demonstrated to stimulate bone growth in animal and human. The cellular mechanism by which zinc stimulates bone growth has not been fully clarified. The effect of hormone and zinc on protein tyrosine phosphatase activity in osteoblastic MC3T3-E1 cells was investigated. Cells were cultured for 72 h in medium containing 10% fetal bovine serum (FBS) to obtain subconfluent monolayers, and then exchanged to culture medium containing either vehicle, zinc sulfate or various hormones in the absence of 10% FBS. After medium change, cells were cultured for 48 h. Protein tyrosine phosphatase activity in the lysate of cells was significantly increased by culture with zinc (10(-6) - 10(-4) M). The effect of zinc in increasing the enzyme activity was completely blocked by culture with cycloheximide (10(-7 )M), an inhibitor of protein synthesis, or 5, 6-dichloro-l-beta-D- riboifuranosylbenzimidarzole (DRB) (10(-6) M), an inhibitor of translational activity. Addition of calcium chloride (10 microM) into the reaction mixture caused a significant increase in protein tyrosine phosphatase activity; this increase was completely blocked in the presence of trifluoperazine (50 microM), an antagonist of calmodulin. Culture with zinc caused a significant increase in Ca2+/calmodulin-dependent protein tyrosine phosphatase activity in osteoblastic cells. Protein tyrosine phosphatase activity was significantly raised by culture with parathyroid hormone (human PTH [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33]; 10(-7) M), 17beta-estradiol (10(-7) M), insulin-like growth factor-I (IGF-I; 10(-8) M) or insulin (10(-8) M). The enzyme activity was not significantly enhanced by the addition of calcium (10 microM) into the reaction mixture. The effect of PTH or IGF-I in increasing protein tyrosine phosphatase activity was completely blocked by culture with DRB. The IGF-I-induced increase in enzyme activity was significantly enhanced by culture with zinc. Such an effect was not seen in the case of PTH. Moreover, the effect of IGF-I in increasing proliferation of osteoblastic cells was significantly enhanced by culture with zinc. The effect of PTH was not enhanced by zinc. This study demonstrates that protein tyrosine phosphatase activity in osteoblastic cells is enhanced by various bone anabolic factors, and that zinc modulates the effect of IGF-I on protein tyrosine phosphatase activity and cell proliferation.

Zinc-induced sodium-dependent vitamin C transporter 2 expression: potent roles in osteoblast differentiation

Zinc is an essential trace element that increases osteoblast numbers and bone formation. However, the mechanisms involved in the Zn-induced differentiation of osteoblasts are poorly understood. We examined the roles of L-ascorbic acid (AA) and its transporter, sodium-dependent vitamin C transporter (SVCT) 2, in the Zn-induced expression of osteoblastic differentiation markers. Zinc time- and dose-dependently induced SVCT2 mRNA expression in the absence or presence of AA. Western blotting and kinetic assays showed that Zn increased functional SVCT2 protein levels and AA transport. In the presence of AA, 50 microM Zn enhanced mRNA expression of the osteoblastic differentiation markers alkaline phosphatase, alpha(1)(I) procollagen, osteopontin (OPN), and osteocalcin (OCN) by 3.9-, 3.8-, 3.3-, and 3.5-fold, respectively; in the absence of AA, the Zn-induced increase was 2.8-, 2.5-, 1.3-, and 1.1-fold, respectively. These findings suggest that AA and SVCT2 mediate Zn-induced OPN and OCN expression and partly regulate Zn-induced osteoblastic differentiation.

Influence of dietetic and anthropometric factors and of the type of sport practised on bone density in different groups of women

OBJECTIVE

The aim of this work was to analyse the influence of dietetic and anthropometric data, as well as the sport practised, on the bone density of different groups of sportswomen.

SUBJECTS AND METHODS

Dietetic, anthropometric and bone density data were collected from 74 women who practised different sports (15 skiers, 26 basketball players and 33 ballet dancers), and compared to those of 90 women who led sedentary lifestyles.

RESULTS

The sportswomen had higher bone mineral contents and bone densities than controls. However, the dancers showed similar spinal and hip values as those of controls, and lower forearm values. Low body weight and body mass index, and insufficient energy intake-characteristic of the dancers-were associated with poorer bone mineralisation status. Increased energy, protein, vitamin D, calcium, zinc and magnesium intakes were associated with greater bone density and mineral content at different sites.

CONCLUSIONS

The worst bone density status was that of the dancers, who, as a group, displayed characteristics that have negative impacts in this respect (low energy intakes and low body weight). Dancers should therefore take steps to avoid suffering fractures and skeleto-muscular lesions which could negatively influence their health and physical performance. The greater consumption of milk products and calcium and better Ca/P ratio seen in the dancers could help this group to avoid bone deterioration.

Zinc supplementation increases bone alkaline phosphatase in healthy men

Zinc takes part in the metabolism of bone as a constituent of the matrix and as an activator of several metallo-enzymes. Animal in vitro and in vivo studies strongly suggest that zinc supplementation could stimulate bone formation and inhibit bone resorption but data in humans remain rare. The biological effects of 50 mg zinc given orally as gluconate in 20 healthy male volunteers were investigated in a 12 weeks double-blind placebo-controlled randomized trial. To investigate bone turnover, total alkaline phosphatases activity (ALP), bone specific alkaline phosphatase activity (BAPE) and BAP mass (BAP-M) concentration were measured as parameters of bone formation while urine calcium and C-terminal collagen peptide were determined as parameters of bone resorption. Samples were obtained in fasting subjects at baseline and after 6 and 12 weeks. In zinc treated subjects, a significant increase was observed at least after 12 weeks in total ALP (p < 0.01), BAP-M (p < 0.05) and BAP-E (p < 0.02). These parameters did not significantly change in the placebo group. Urine zinc/creatinine ratio significantly increased after 6 (p < 0.03) and 12 weeks (p < 0.04) in the zinc-treated group and was significantly different from the placebo group (p < 0.002). There was no significant effect of zinc supplementation on parameters of bone resorption. In conclusion, zinc supplementation at supraphysiological doses increased parameters of bone formation in healthy men while parameters of bone resorption remained unchanged.

The role of zinc in growth and cell proliferation

The inhibition of growth is a cardinal symptom of zinc deficiency. In animals fed a zinc-inadequate diet, both food intake and growth are reduced within 4-5 d. Despite the concomitant reduction in food intake and growth, reduced energy intake is not the limiting factor in growth, because force-feeding a zinc-inadequate diet to animals fails to maintain growth. Hence, food intake and growth appear to be regulated by zinc through independent, although well coordinated, mechanisms. Despite the long-term study of zinc metabolism, the first limiting role of zinc in cell proliferation remains undefined. Zinc participates in the regulation of cell proliferation in several ways; it is essential to enzyme systems that influence cell division and proliferation. Removing zinc from the extracellular milieu results in decreased activity of deoxythymidine kinase and reduced levels of adenosine(5')tetraphosphate(5')-adenosine. Hence, zinc may directly regulate DNA synthesis through these systems. Zinc also influences hormonal regulation of cell division. Specifically, the pituitary growth hormone (GH)-insulin-like growth factor-I (IGF-I) axis is responsive to zinc status. Both increased and decreased circulating concentrations of GH have been observed in zinc deficiency, although circulating IGF-I concentrations are consistently decreased. However, growth failure is not reversed by maintaining either GH or IGF-I levels through exogenous administration, which suggests the defect occurs in hormone signaling. Zinc appears to be essential for IGF-I induction of cell proliferation; the site of regulation is postreceptor binding. Overall, the evidence suggests that reduced zinc availability affects membrane signaling systems and intracellular second messengers that coordinate cell proliferation in response to IGF-I.

Regulatory roles of zinc in matrix vesicle-mediated mineralization of growth plate cartilage

Zinc (Zn2+) has long been known to play important roles in mineralization and ossification of skeletal tissues, but the mechanisms of Zn2+ action are not well understood. In this study we investigated the effects of Zn2+ on mineralization in a cell culture system in which terminal differentiation and mineralization of hypertrophic growth plate chondrocytes was induced by retinoic acid (RA) treatment. Addition of Zn2+ to RA-treated cultures decreased mineralization in a dose-dependent manner without affecting alkaline phosphatase (APase) activity. Characterization of matrix vesicles (MVs), particles that initiate the mineralization process, revealed that vesicles isolated from RA-treated and RA/Zn2+-treated cultures showed similar APase activity, but vesicles from RA/Zn2+-treated cultures contained significantly less Ca2+ and Pi. MVs isolated from RA-treated cultures were able to take up Ca2+ and mineralize in vitro, whereas vesicles isolated from RA/Zn2+-treated cultures were not able to do so. Detergent treatment, which ruptures the MV membrane and exposes preformed intravesicular Ca2+-Pi-phospholipid complexes, did not restore the Ca2+ uptake abilities of MVs isolated from RA/Zn2+-treated cultures, suggesting that vesicles from RA/Zn2+-treated cultures did not contain functional Ca2+-Pi-phospholipid complexes. Zn2+ treatment did not affect the content of annexins II, V, and VI in MVs or the Ca2+-dependent, EDTA-reversible binding of these molecules to the membrane surface. However, Zn2+ treatment did affect the EDTA-nonreversible binding of these molecules to the MV membrane, suggesting that Zn2+ interferes with the assembly of annexins in the MV membrane. In addition, Zn2+ inhibited annexin II-, V-, and VI-mediated Ca2+ influx into liposomes. In conclusion, Zn2+ inhibits the mineralizing competence of intravesicular Ca2+-Pi-phospholipid complexes and function of annexin channels, thereby controlling Ca2+ influx into MVs, the formation of the first crystal phase inside the vesicles and initiation of mineralization.

Stimulatory effect of zinc acexamate administration on fracture healing of the femoral-diaphyseal tissues in rats

The effect of zinc acexamate on fracture healing of the femoral-diaphyseal tissues in rats was investigated in vivo. Zinc acexamate (0.3 and 10.0 mg Zn/100 g body weight per day) was orally administered to rats (4 weeks old) surgically fractured the femoral diaphysis for 14 to 28 days. Calcium content and alkaline phosphatase activity in the femoral-diaphyseal tissues were significantly decreased in rats with fracture healing, while bone acid phosphatase activity and protein content were markedly increased. The administration of zinc acexamate (10.0 mg Zn/100 g) for 28 days caused a significant increase in calcium content, alkaline and acid phosphatases activities, protein and deoxyribonucleic acid (DNA) contents in the femoral-diaphyseal tissues of rats with fracture healing. With the lower dose (3.0 mg Zn/100 g), zinc compound had a partial effect on bone components. Femoral mineral density in rats with fracture healing was significantly increased by the administration of zinc acexamate (10.0 mg Zn/100 g) for 28 days. Femoral-diaphyseal zinc content was significantly decreased in rats with fracture healing. This decrease was completely restored by the administration of zinc acexamate (10.0 mg Zn/100 g) for 28 days. The present study suggests that the supplement of zinc compound stimulates fracture healing of the femoral-diaphyseal tissues in rats.

Zinc enhancement of genistein's anabolic effect on bone components in elderly female rats

1. The effect of genistein on the bone components in the femoral-metaphyseal and diaphyseal tissues of elderly female rats was investigated. 2. The oral administration of genistein (100 and 200 microg/kg body weight) for 3 days to rats caused a significant increase in alkaline phosphatase activity, deoxyribonucleic acid (DNA) and calcium contents in the femoral-metaphyseal and diaphyseal tissues. A dose of 50 microg genistein/kg appreciably increased alkaline phosphatase activity and DNA content in the metaphyseal but not the diaphyseal tissues. 3. Alkaline phosphatase activity, DNA and calcium contents in the femoral-metaphyseal and diaphyseal tissues were significantly elevated by the oral administration of zinc sulfate (5.5 mg Zn/kg) for 3 days. The effect of zinc on increasing bone DNA and calcium contents was synergistically enhanced by the simultaneous administration of genistein (100 microg/kg). 4. The stimulatory effect of zinc sulfate (10(-5) M) or genistein (10(-5) M) on bone calcium content was also seen in a culture system using the femoral-metaphyseal and diaphyseal tissues in vitro. This effect was completely prevented by the presence of cycloheximide (10(-6) M). 5. The present findings suggest that genistein has an anabolic effect on bone components and that the effect is enhanced by zinc, owing to its stimulating effect on bone protein synthesis.

Potent effect of zinc acexamate on bone components in the femoral-metaphyseal tissues of elderly female rats

1. The effect of zinc compounds on bone components in the femoral-metaphyseal tissues from elderly female rats (50 weeks old) was investigated in vitro. Bone tissues were cultured for 24 hr in Dulbecco's modified Eagle medium containing either vehicle or zinc compounds (10[-7] to 10[-5] M). 2. Zinc content, alkaline phosphatase activity, deoxyribonucleic acid (DNA) and calcium contents in the metaphyseal tissues were significantly increased by the presence of zinc sulfate (10[-6] and 10[-5] M), beta-alanyl-L-histidinato zinc (AHZ; 10[-6] and 10[-5] M) and zinc acexamate (10[-7] to 10[-5] M). At 10[-5] M, the effect of zinc acexamate on the increase of bone components was more potent than that of zinc sulfate or AHZ. 3. The effect of zinc acexamate (10[-5] M) on the increase of alkaline phosphatase activity in the metaphyseal tissues was remarkable as compared with that of insulin (10[-8] M), estrogen (10[-9] M), insulin-like growth factor-I (10[-8] M), transforming growth factor-beta (10[-10] M), sodium fluoride (10[-3] M), dexamethasone (10[-7] M) and vitamin K2 (menaquinone-4; 10[-5] M) with an effective concentration. 4. The stimulatory effect of zinc acexamate (10[-5] M) on alkaline phosphatase activity and calcium content in the metaphyseal tissues was completely blocked by the presence of dipicolinate (10[-3] M), a chelator of zinc ion, and of cycloheximide (10[-6] M), an inhibitor of protein synthesis. 5. The present study demonstrates that zinc acexamate has a potent anabolic effect on bone components in the femoral-metaphyseal tissues from female elderly rats in vitro. The effect of zinc acexamate may be based in part on protein synthesis related to zinc ion in bone cells.

Anabolic effect of genistein and genistin on bone metabolism in the femoral-metaphyseal tissues of elderly rats: the genistein effect is enhanced by zinc

The effect of genistein and genistin on bone components in the femoral-metaphyseal tissues obtained from elderly female rats was investigated in vitro. The metaphyseal tissues were cultured for 24 h in a medium containing either vehicle, genistein (10(-8)-10(-5) M) or genistin (10(-7)-10(-5) M). The presence of genistein or genistin caused a significant increase in alkaline phosphatase activity, deoxyribonucleic acid (DNA) and calcium contents in the metaphyseal tissues. The effect of genistein was greater than that of genistin. The bone components increased by genistein (10(-5) M) or genistin (10(-5) M) were completely blocked by the presence of cycloheximide (10(-6) M). The presence of zinc sulfate (10(-5) M) caused a significant increase in the genistein (10(-5) M)-elevated alkaline phosphatase activity, DNA and calcium contents. The enhancement with zinc was not seen by genistin (10(-5) M). The stimulatory effect of zinc on the genistein-induced increase in bone components of the metaphyseal tissues was completely blocked by the presence of cycloheximide (10(-6) M). The present results suggest that genistein and genistin have an anabolic effect on bone metabolism in the femoral-metaphyseal tissues of elderly rats, and that the genistein effect is enhanced by zinc, an essential trace element.

Zinc stimulates protein synthesis in the femoral-metaphyseal tissues of normal and skeletally unloaded rats

The effect of zinc on protein synthesis in the femoral-metaphyseal tissues of normal and skeletally unloaded rats was investigated. Skeletal unloading was designed using the model of hindlimb suspension in rats. Animals were fed for 2 or 4 days during the unloading. [3H]Leucine was added to the reaction mixture containing the 5500 g supernatant fraction of the homogenate prepared from the femoral-metaphyseal tissues. In vitro protein synthesis was significantly decreased in the bone tissues from the rats which had undergone unloading for 2 or 4 days. When the metaphyseal tissues were cultured for 24 h in the presence of zinc sulfate (10(-5) M) or beta-alanyl-L-histidinato zinc (AHZ, 10(-5) M), zinc compounds clearly stimulated protein synthesis in the metaphyseal tissues from the 4-day unloaded rats. The zinc effect was also seen in the metaphyseal tissues from normal rats. The addition of zinc sulfate (10(-5) M) or AHZ (10(-7) to 10(-5) M) into the reaction mixture containing the 5500 g supernatant fraction of metaphyseal homogenate from normal or unloaded rats produced a significant increase in protein synthesis. This increase was clearly inhibited in the presence of cycloheximide (10(-7) M). The present result demonstrates that protein synthesis is impaired in the femoral-metaphyseal tissues of rats with skeletal unloading, and that this impairment is clearly restored by zinc supplementation.

Effect of vitamin K2 (menaquinone-7) on bone metabolism in the femoral-metaphyseal tissues of normal and skeletal-unloaded rats: enhancement with zinc

The effect of vitamin K2 (menaquinone-7) on bone metabolism in the femoral-metaphyseal tissues of normal and skeletal-unloaded rats was investigated. Skeletal unloading was designed using a model of hindlimb suspension; the rats were fed for the 4 days of unloading. The metaphyseal tissues obtained from normal and skeletal-unloaded rats were cultured for 48 h in medium containing either vehicle or vitamin K2 (10(-6) and 10(-5) M). The presence of vitamin K2 (10(-5) M) caused a significant increase in alkaline phosphatase activity and calcium content in the metaphyseal tissues from normal rats. Such an effect was not seen in the bone tissues from skeletal-unloaded rats. Additionally, the presence of zinc sulfate (10(-5) M) in effective concentration produced a significant increase in alkaline phosphatase activity and calcium content in the metaphyseal tissues from normal and skeletal-unloaded rats. In the presence of vitamin K2 (10(-5) M), the stimulatory effect of zinc sulfate on bone calcium content was appreciably enhanced; although this effect was completely abolished by cycloheximide (10(-6) M), an inhibitor of protein synthesis. This study demonstrates that the effect of vitamin K2 (menaquinone-7) on trabecular bone calcification in rats with skeletal unloading-induced osteopenia is enhanced by zinc in vitro. The enhancement with zinc may be based on a newly synthesized protein in the bone tissues.

Histomorphological confirmation of bone loss in the femoral-metaphyseal tissues of rats with skeletal unloading

The alteration of mineral content in the femoral metaphysis of rats with skeletal unloading was investigated using a model of hindlimb suspension. Animals were fed for 4 days during the unloading. The femoral length, femoral dry weight and femoral mineral density were significantly decreased by the unloading. The calcium, phosphorus and zinc contents in the femoral metaphysis were appreciably reduced by the unloading, although, except for zinc, similar decreases were not seen in the femoral diaphysis. Moreover, the trabecular bone at the femoral metaphysis was clearly reduced by the unloading. Skeletal unloading caused a decrease in osteoid tissue in the primary and secondary spongiosa, indicating that osteoblastic bone formation may be inhibited. The present results clearly demonstrate that skeletal unloading can induce bone loss in the femoral metaphysis.

Stimulatory effect of zinc-chelating dipeptide on deoxyribonucleic acid synthesis in osteoblastic MC3T3-E1 cells

Whether deoxyribonucleic acid (DNA) synthesis in osteoblastic MC3T3-E1 cells is stimulated by zinc, an activator of bone formation, was investigated in vitro. After subculture for 3 days, the cells were cultured for up to 3 days (72 h) with zinc sulfate or zinc-chelated dipeptide (beta-alanyl-L-histidinato zinc; AHZ) in the range of 10(-7) to 10(-5) M. The culture with zinc compounds (10(-5) M) produced a significant increase of cell number, DNA content, and protein concentration in the cells, as reported previously. The culture with zinc compounds (10(-6) and 10(-5) M) clearly stimulated DNA synthesis in the homogenate, when it was estimated by the incorporation of [3H]deoxythymidine 5'-triphosphate into the DNA in the homogenate of cells. The AHZ effect was greater than that of zinc sulfate. The culture together with cycloheximide (19(-6) M) completely abolished the zinc compounds (10(-5) M)-induced increase of DNA synthesis in the cells, suggesting that the zinc compound effect is based on a newly synthesized protein component. Moreover, when zinc sulfate (10(-7) and 10(-6) M) or AHZ (10(-8) to 10(-5) M) was added into the reaction mixture with the homogenate of cells cultured without zinc compounds, the DNA synthesis was clearly increased. The effect of addition of zinc compounds (10(-6) M) on the DNA synthesis was completely inhibited by the presence of staurosporine (10(-8) M), an inhibitor of protein kinase C, or okadaic acid (10(-7) M), an inhibitor of protein phosphatase. The present study demonstrates that zinc compounds have a stimulatory effect on DNA synthesis in osteoblastic cells.

Differential effects of transforming growth factor-beta on osteoclast-like cell formation in mouse marrow culture: relation to the effect of zinc-chelating dipeptides

The effect of transforming growth factor-beta (TGF-beta) on osteoclast-like cell formation in mouse marrow culture in vitro was investigated. The bone marrow cells were cultured for 7 days in alpha-minimal essential medium containing a well-known bone resorbing agent. Osteoclast-like cell formation was estimated with staining for tartrate-resistant acid phosphatase (TRACP), a marker enzyme of osteoclasts. The presence of TGF-beta (10(-13)-10(-11) M) caused a significant increase in the number of osteoclast-like multinucleated cells (MNCs); the maximum effect was seen with 10(-12) MTGF-beta. With a higher concentration (10(-10) M) of TGF-beta, the growth factor dramatically inhibited the 1,25-dihydroxyvitamin D5 [1,25(OH)2D3; 10(-8) M]-induced formation of osteoclast-like MNCs. This inhibitory effect was also seen in the formation of osteoclast-like MNCs stimulated by parathyroid hormone (10(-8) M), prostaglandine E2 (10(-6) M), and interleukin-1 alpha (50 U/ml). The stimulatory effect of TGF-beta (10(-12) M) on osteoclast-like MNCs formation was inhibited by zinc sulfate (10(-6) M) or zinc-chelating dipeptide [beta-alanyl-L-histidinato zinc (AHZ), 10(-6) M]. The stimulating effect of TGF-beta was markedly weakened by the presence of EGTA (0.5 mM), a chelator of Ca2+. The inhibitory effect of zinc compounds was not seen in the presence of EGTA. Moreover, the inhibitory effect of TGF-beta (10(-10) M), zinc sulfate (10(-6) M), or AHZ (10(-6) M) on osteoclast-like MNCs formation was not demonstrated in mature osteoclastic cells, although calcitonin (3 x 10(-8) M) significantly inhibited the osteoclastic formation. The present study demonstrates that TGF-beta has a stimulating and an inhibiting effect on osteoclast-like cell formation in mouse marrow culture, and that zinc can inhibit the stimulatory effect of TGF-beta.

Zinc modulation of insulin-like growth factor's effect in osteoblastic MC3T3-E1 cells

Whether the anabolic effect of insulin-like growth factor-I (IGF-I) in osteoblastic MC3T3-E1 cells is modulated by zinc, an activator of bone formation, was investigated in vitro. After subculture for 3 days, the cells were cultured for 72 h with IGF-I (10(-8) M). The peptide produced a significant increase of protein concentration, deoxyribonucleic acid (DNA) content, and cell number in the cells. These increases were markedly enhanced by the presence of zinc sulfate (10(-5) M), but not zinc-chelating dipeptide (beta-alanyl-L-histidinato zinc; 10(-5) M). Also, the cellular alkaline phosphatase activity was synergistically increased by the presence of both IGF-I and zinc sulfate. Thus, effect was not seen in the presence of both insulin (10(-8) M) and zinc sulfate (10(-5) M). The effect of zinc sulfate to enhance the IGF-I-increased alkaline phosphatase activity and protein concentration in the cells was clearly prevented by the presence of cycloheximide (10(-6) M), staurosporin (10(-8) M), or okadaic acid (10(-7) M) with an effective concentration. However, staurosporin had a partial inhibiting effect on the IGF-I or the IGF-I plus zinc-induced increases in cellular protein, although okadaic acid entirely blocked the IGF-I or the IGF-I plus zinc effect. The present study demonstrates that the anabolic effect of IGF-I in osteoblastic cells is enhanced by zinc ion. The enhancement by zinc may be mediated through the signaling pathway of protein kinase C and protein phosphatase in the cells.

Differential effects of insulin and insulin-like growth factor-I in the femoral tissues of rats with skeletal unloading

The alteration of bone metabolism in the femur of rats with skeletal unloading for 4 days was investigated. Skeletal unloading was designed using the model of hindlimb hang in rats. Skeletal unloading caused a significant decrease in femoral weight, calcium, and phosphorus contents in the metaphysis but not diaphysis. Also, the unloading induced a significant decrease of zinc content, alkaline phosphatase activity, and deoxyribonucleic acid (DNA) content in the femoral diaphysis and metaphysis. When the femoral-diaphyseal and metaphyseal tissues from normal and skeletal-unloading rats were cultured in the presence of insulin (10(-9) and 10(-8) M) for 24 hours in vitro, the hormonal effect to increase alkaline phosphatase activity and DNA content in the diaphysis, but not metaphysis, was lost in the bone tissues from unloading rats. However, the culture with insulin-like growth factor-I (IGF-I; 10(-8) and 10(-7) M) produced a significant increase of alkaline phosphatase activity and DNA content in both the diaphyseal and metaphyseal tissues from normal and unloading rats. These results demonstrate that skeletal unloading causes an impairment of insulin effect, but not IGF-I effect, on bone metabolism in femoral tissues.