Selenoproteins are expressed in fetal human osteoblast-like cells

Effects of selenium and iodine on Kashin-Beck disease: an updated review

Kashin-Beck disease (KBD) is an endochondral osteogenesis disorder characterised by epiphysis damage and secondary deformable arthropathy induced by multiple external factors, among which selenium (Se) and iodine deficiency are important influencing factors. Iodine deficiency is usually accompanied by a low Se content in the soil in the KBD areas of China. Se can reverse oxidative damage to chondrocytes. In addition, Se is related to the bone conversion rate and bone mineral density. Low Se will hinder growth and change bone metabolism, resulting in a decrease in the bone conversion rate and bone mineral density. Thyroid hormone imbalance caused by thyroid dysfunction caused by iodine deficiency can damage bone homeostasis. Compared with Se deficiency alone, Se combined with iodine deficiency can reduce the activity of glutathione peroxidase more effectively, which increases the vulnerability of chondrocytes and other target cells to oxidative stress, resulting in chondrocyte death. Clinical studies have shown that supplementation with Se and iodine is helpful for the prevention and treatment of KBD.

Native thiol decreases in patients with asymptomatic primary hyperparathyroidism, especially in the presence of surgery indication

BACKGROUND

Oxidative stress increases in many systemic and endocrine diseases. The effect of increased parathyroid hormone levels (PTH) and the effects of this hormone on oxidative stress in patients with primary hyperparathyroidism (pHPT) is unknown. We aimed to investigate the change of Thiol-disulfide (SH-SS), one of the oxidative stress parameters, in patients diagnosed with pHPT and the usability of this parameter in patients with pHPT.

METHODS

Forty-six patients who recently diagnosed with asymptomatic pHPT and 40 healthy controls were included in this prospective study. In addition to routine examinations for pHPT, serum SH-SS measurements were recorded. The pHPT patients included in the study were divided into two groups as patients with and without surgical treatment indication.

RESULTS

It was observed that the pHPT group had lower total SH and native SH values and higher SS values compared to the control group (P<0.05 for each). Native SH values were found to be lower in pHPT patients who were indicated for surgical treatment compared to those who did not (P<0.05). An independent relationship was found between Native SH and serum calcium, urine calcium and T scores in DEXA level in asymptomatic pHPT patients with surgical treatment indication (P<0.05).

CONCLUSIONS

In our study, native SH level decreases in patients with pHPT, especially in patients with surgical treatment indication for pHPT. The decrease in SH levels, which is a natural antioxidant that protects the body against oxidative stress, and the increase in SS levels in pHPT patients may be another metabolic effect of this disease. Native SH may be helpful in determining the indication for surgical treatment in asymptomatic pHPT patients.

Development and Validation of Machine Learning Models for Prediction of Fracture Risk in Patients with Elderly-Onset Rheumatoid Arthritis

Objective

Fracture is a critical unfavorable prognostic factor in patients with rheumatoid arthritis(RA) and osteoporosis. At present, models involving clinical indices that accurately predict fracture are still uncommon. We addressed this gap by developing machine learning (ML)-based predictive models to individualize the risk of fracture in elderly patients with RA and osteoporosis and to identify a high-risk group for fracture.

Methods

487 patients diagnosed with RA and osteoporosis at the Central Hospital of Enshi Tujia and Miao Autonomous Prefecture were randomly divided into a training cohort (used for building the model) and a validation cohort (used for validating the model). Five ML-assisted models were developed from candidate clinical features using two-step estimation methods. The receiver operating characteristic curve (ROC), decision curve analysis (DCA), and clinical impact curve (CIC) were performed to evaluate the robustness and clinical practicability of each model.

Results

A total of twenty-two candidate variables were included, and the prediction model was established by an ML-based algorithm. The areas under the ROC curve (AUCs) of the random forest classifier (RFC) model, artificial neural network (ANN), support vector machine (SVM), eXtreme gradient boosting (XGBoost), decision tree (DT), probability of major osteoporotic fractures (PMOF), and probability of hip fracture (PHF) ranged from 0.695 to 0.878. Among them, RFC obtained the optimal prediction efficiency via adding serum selenium and clinical indices, that is, glucocorticoid, and erythrocyte sedimentation rate (ESR).

Conclusion

Based on the classic clinical parameters, the fracture risk of RA patients with osteoporosis can be accurately predicted. In particular, RFC prediction model shows good discrimination ability in identifying high-risk patients with fracture.

Selenoprotein K protects skeletal muscle from damage and is required for satellite cells-mediated myogenic differentiation

The regeneration of adult skeletal muscle after injury is primarily initiated by satellite cells (SCs), but the regulatory mechanisms of cells committed to myogenic differentiation remain poorly explored. Small molecular selenoprotein K (SelK) plays crucial roles in the modulation of endoplasmic reticulum (ER) stress and against oxidative stress. Here, we first showed that SelK expression is activated in myogenic cells during differentiation both in vivo and in vitro. Meanwhile, loss of SelK delayed skeletal muscle regeneration, inhibited the development of myoblasts into myotubes, and was accompanied by reduced expression of myogenic regulatory factors (MRFs). Moreover, ER stress, intracellular reactive oxygen species (ROS), autophagy and apoptosis under myogenesis induction were more severe in SelK-deficient mice and cells than in the corresponding control groups. Supplementation with specific inhibitors to alleviate excessive ER stress or oxidative stress partly rescued the differentiation potential and formation of myotubes. Notably, we demonstrated that Self-mediated regulation of cellular redox status was primarily derived from its subsequent effects on ER stress. Together, our results suggest that SelK protects skeletal muscle from damage and is a crucial regulator of myogenesis.

Glutathione Immobilized Polycaprolactone Nanofiber Mesh as a Dermal Drug Delivery Mechanism for Wound Healing in a Diabetic Patient

Glutathione (GSH) is an anti-inflammatory and antioxidant biomolecule. Polycaprolactone (PCL) nanofiber mesh (NFM) is capable of the attachment and release of biomolecules for prolonged periods and has the potential as a transdermal drug delivery system during wound healing for a diabetic patient. Our earlier study found that high levels of sugar in diabetic male mice were significantly decreased by daily doses of glutathione administered on the mice. Furthermore, oxidative stress found in diabetic male mice led to the total depletion of glutathione levels in the body’s organs (pancreas, spleen, epididymis, and testis). The objective of this study was to attach GSH with PCL NFM for the controlled release of GSH biomolecules for long periods of time from the fiber mesh into a diabetic body. This study produced PCL NFM using an electrospun technique and tested it on mice to evaluate its efficiency as a dermal drug delivery mechanism. This study dissolved GSH (2.5 mg/mL) with phosphate-buffered saline (PBS) and glutaraldehyde (GLU) solution to create GSH-PBS and GSH-GLU complexes. Each complex was used to soak PCL NFM for 24 h and dried to create PCL-GSH-PBS and PCL-GSH-GLU meshes. Fiber morphology, degradation, fibroblast cell proliferation, cytotoxicity, and GSH release activities from each mesh were compared. Fibroblast cell adhesion and cytotoxicity tests found excellent biocompatibility of both GSH-immobilized PCL meshes and no degradation until 20 days of the study period. The disk diffusion method was conducted to test the antibacterial properties of the sample groups. Release tests confirmed that the attachment of GSH with PCL by GSH-GLU complex resulted in a steady release of GSH compared to the fast release of GSH from PCL-GSH-PBS mesh. The disk diffusion test confirmed that PCL-GSH-GLU has antibacterial properties. The above results conclude that GSH-GLU immobilized PCL NFM can be a suitable candidate for a transdermal anti-oxidative and anti-bacterial drug delivery system such as bandage, skin graft for wound healing application in a diabetic patient.

Anti-Osteoporotic Mechanisms of Polyphenols Elucidated Based on In Vivo Studies Using Ovariectomized Animals

Polyphenols are widely known for their antioxidant activity, i.e., they have the ability to suppress oxidative stress, and this behavior is mediated by the autoxidation of their phenolic hydroxyl groups. Postmenopausal osteoporosis is a common health problem that is associated with estrogen deficiency. Since oxidative stress is thought to play a key role in the onset and progression of osteoporosis, it is expected that polyphenols can serve as a safe and suitable treatment in this regard. Therefore, in this review, we aimed to elucidate the anti-osteoporotic mechanisms of polyphenols reported by in vivo studies involving the use of ovariectomized animals. We categorized the polyphenols as resveratrol, purified polyphenols other than resveratrol, or polyphenol-rich substances or extracts. Literature data indicated that resveratrol activates sirtuin 1, and thereafter, suppresses osteoclastogenic pathways, such as the receptor activator of the nuclear factor kappa B (RANK) ligand (RANKL) pathway, and promotes osteoblastogenic pathways, such as the wingless-related MMTV integration site pathway. Further, we noted that purified polyphenols and polyphenol-rich substances or extracts exert anti-inflammatory and/or antioxidative effects, which inhibit RANKL/RANK binding via the NF-κB pathway, resulting in the suppression of osteoclastogenesis. In conclusion, antioxidative and anti-inflammatory polyphenols, including resveratrol, can be safe and effective for the treatment of postmenopausal osteoporosis based on their ability to regulate the imbalance between bone formation and resorption.

The Effects of Selenium on Bone Health: From Element to Therapeutics

Osteoporosis, characterized by low bone mass and a disruption of bone microarchitecture, is traditionally treated using drugs or lifestyle modifications. Recently, several preclinical and clinical studies have investigated the effects of selenium on bone health, although the results are controversial. Selenium, an important trace element, is required for selenoprotein synthesis and acts crucially for proper growth and skeletal development. However, the intake of an optimum amount of selenium is critical, as both selenium deficiency and toxicity are hazardous for health. In this review, we have systematically analyzed the existing literature in this field to determine whether dietary or serum selenium concentrations are associated with bone health. In addition, the mode of administration of selenium as a supplement for treating bone disease is important. We have also highlighted the importance of using green-synthesized selenium nanoparticles as therapeutics for bone disease. Novel nanobiotechnology will be a bridgehead for clinical applications of trace elements and natural products.

Selenium: A Trace Element for a Healthy Skeleton - A Narrative Review

Inadequate serum selenium levels may delay the growth and physiological changes in bone metabolism. In humans, reduced serum selenium concentrations are associated with both increased bone turnover and reduced bone mineral density. Moreover, a reduced nutritional intake of selenium may lead to an increased risk of bone disease. Therefore, selenium is an essential nutrient playing a role in bone health, probably due to specific selenium-proteins. Some selenium-proteins have an antioxidation enzymatic activity and participate in maintaining the redox cellular balance, regulating inflammation and proliferation/differentiation of bone cells too. At least nine selenium-proteins are known to be expressed by fetal osteoblasts and appear to protect bone cells from oxidative stress at bone microenvironment. Mutations of selenium-proteins and reduced circulating levels of selenium are known to be associated with skeletal diseases such as the Kashin-Beck osteoarthropathy and postmenopausal osteoporosis. In addition, the intake of selenium appears to be inversely related to the risk of hip fragility fractures. Recent data suggest that an altered selenium state may affect bone mass even in males and selenium-proteins and selenium concentrations were positively associated with the bone mass at femoral, total and trochanteric sites. However, selenium, but not selenium-proteins, seems to be associated with femoral neck bone mass after adjustment for many bone fracture risk factors. The present review summarizes the findings of observational and interventional studies, which have been designed for investigating the relationship between selenium and bone metabolism.

Selenium in Endocrinology-Selenoprotein-Related Diseases, Population Studies, and Epidemiological Evidence

Selenium (Se), apart from iodine, iron, and calcium, is one of the nutrient-derived key elements strongly affecting the endocrine system. However, no specific hormonal "feedback" regulation for Se status has yet been identified, in contrast to the fine-tuned hormone network regulating Ca2+ and phosphate balance or hepcidin-related iron status. Since its discovery as an essential trace element, the effects of Se excess or deficiency on the endocrine system or components of the hypothalamic-pituitary-periphery feedback circuits, the thyroid hormone axis, glucoregulatory and adrenal hormones, male and female gonads, the musculoskeletal apparatus, and skin have been identified. Analysis of the Se status in the blood or via validated biomarkers such as the hepatically derived selenoprotein P provides valuable diagnostic insight and a rational basis for decision making on required therapeutic or preventive supplementation of risk groups or patients. Endocrine-related epidemiological and interventional evidence linking Se status to beneficial or potentially adverse actions of selected selenoproteins mediating most of the (patho-) physiological effects are discussed in this mini-review. Autoimmune thyroid disease, diabetes and obesity, male fertility, as well as osteoporosis are examples for which observational or interventional studies have indicated Se effects. The currently prevailing concept relating Se and selenoproteins to "oxidative stress," reactive oxygen species, radical hypotheses, and related strategies of pharmacological approaches based on various selenium compounds will not be the focus. The crucial biological function of several selenoproteins in cellular redox-regulation and specific enzyme reactions in endocrine pathways will be addressed and put in clinical perspective.

Selenium and bone health: a protocol for a systematic review and meta-analysis

INTRODUCTION

Bone health affects the ability of human body to stay active, and its degradation can cause considerable morbidity and mortality. The factors related to bone health play an important role in preventing osteoporosis and its adverse consequences. However, the risk factors for osteoporosis have not been fully elucidated. Deficiency in the trace element selenium may be one of the risk factors for the development of osteoporosis. Previous studies have investigated the effects of selenium on osteoporosis; however, the results are inconclusive. Therefore, the present study aimed to systematically examine the existing literature on the associations between dietary or serum selenium and bone mineral density (BMD), osteoporosis or osteoporotic fractures, and to quantify such associations through meta-analysis.

METHODS AND ANALYSIS

PubMed, Embase and Cochrane Library will be searched using a specified search strategy to identify relevant studies up to October 2019. Both interventional and observational studies in humans will be included. The outcomes will include BMD and the prevalence or incidence of osteoporosis and osteoporotic fractures. For dietary or serum selenium and BMD, osteoporosis or osteoporotic fractures pooled analyses, estimates will be expressed as the mean difference, and the pooled OR, relative risk, HR or beta coefficient, and corresponding 95% CIs. Heterogeneity of the studies and publication bias will be investigated accordingly. To assess the quality and the risk of bias of the included studies, the Newcastle-Ottawa Quality Scale or the Cochrane risk of bias assessment tool will be used where appropriate.

ETHICS AND DISSEMINATION

Since no private and confidential patient data will be included in the reporting, approval from an ethics committee is not required. The results will be published in a peer-reviewed journal. The study raises no ethical issues.

PROSPERO REGISTRATION NUMBER

CRD42019147188.

The Impact of Trace Minerals on Bone Metabolism

Bone is a metabolically active tissue that responds to alterations in dietary intake and nutritional status. It is ~ 35% protein, mostly collagen which provides an organic scaffolding for bone mineral. The mineral is the remaining ~ 65% of bone tissue and composed mostly of calcium and phosphate in a form that is structurally similar to mineral within the apatite group. The skeletal tissue is constantly undergoing turnover through resorption by osteoclasts coupled with formation by osteoblasts. In this regard, the overall bone balance is determined by the relative contribution of each of these processes. In addition to macro minerals such as calcium, phosphorus, and magnesium which have well-known roles in bone health, trace elements such as boron, iron, zinc, copper, and selenium also impact bone metabolism. Effects of trace elements on skeletal metabolism and tissue properties may be indirect through regulation of macro mineral metabolism, or direct by affecting osteoblast or osteoclast proliferation or activity, or finally through incorporation into the bone mineral matrix. This review focuses on the skeletal impact of the following trace elements: boron, iron, zinc, copper, and selenium, and overviews the state of the evidence for each of these minerals.

Amniotic fluid minerals, trace elements, and prenatal supplement use in humans emerge as determinants of fetal growth

Amniotic fluid (AF), which is swallowed by the developing fetus, contains minerals and trace elements, but their association with fetal growth has not been explored. Our objectives were to assess (1) whether concentrations of AF minerals and trace elements were associated with changes in 5 fetal ultrasound measurements (estimated weight, bi-parietal diameter, head circumference, abdominal circumference, femur length) between 16-20 and 32-36 wks gestation and (2) whether a prenatal supplement was associated with concentrations of AF minerals and trace elements or the 5 fetal ultrasound measurements. We measured, using inductively coupled plasma-mass spectrometry (ICP-MS), 15 minerals and trace elements (aluminum, arsenic, calcium, chromium, copper, iron, lead, magnesium, nickel, potassium, rubidium, selenium, silver strontium, zinc) in amniotic fluid collected from 176 pregnant women undergoing age-related amniocentesis for genetic testing (15.7 ± 1.1 wks). AF mineral concentrations, prenatal supplement use, and determinants of ultrasound measurements during early and late pregnancy were used in models to assess their impact on change in fetal ultrasound measurements. Positive associations were identified for change in bi-parietal diameter with AF calcium, for change in head circumference with AF copper and nickel, and for change in femur length with AF selenium. Arsenic was negatively associated with estimated fetal weight, and this relationship was modified by prenatal supplement use. Additionally, AF chromium concentrations were lower in women taking prenatal supplements. In conclusion, AF minerals were associated with fetal ultrasound indices, supporting a biological role for calcium, copper, nickel and selenium in promoting in-utero fetal growth. Evidence of a mineral-vitamin interaction between arsenic and folic acid in prenatal supplements and mineral-mineral interaction between iron and chromium would suggest that attention be paid to mineral and trace element formulation of prenatal supplements.

Degradation of selenoprotein S and selenoprotein K through PPARγ-mediated ubiquitination is required for adipocyte differentiation

Adipocyte differentiation is known to be related with endoplasmic reticulum (ER) stress. We have reported that selenoprotein S (SelS) and selenoprotein K (SelK) have a function in the regulation of ER stress and ER-associated degradation. However, the association between adipocyte differentiation and the ER-resident selenoproteins, SelS and SelK, is unclear. In this study, we found that the levels of SelS and SelK were decreased during adipocyte differentiation and were inversely related to the levels of peroxisome proliferator-activated receptor γ (PPARγ), a central regulator of adipogenesis. It has been recently reported that PPARγ has E3 ubiquitin ligase activity. Here, we report that PPARγ directly interacts with both SelS and SelK via its ligand-binding domain to induce ubiquitination and degradation of the selenoproteins. Lysine residues at the 150th position of SelS and the 47th and 48th positions of SelK were the target sites for ubiquitination by PPARγ. We also found that adipocyte differentiation was inhibited when either SelS or SelK was not degraded by PPARγ. Thus, these data indicate that PPARγ-mediated ubiquitination and degradation of SelS and SelK is required for adipocyte differentiation.

Safety and efficacy of tocotrienol supplementation for bone health in postmenopausal women: protocol for a dose-response double-blinded placebo-controlled randomised trial

INTRODUCTION

Osteoporosis is a major health concern in postmenopausal women, and oxidative stress contributes to the development of bone loss. Cellular studies and ovariectomised rat model mimicking bone loss in postmenopausal women show the bone-protective effect of tocotrienols (TTs) with antioxidant capability. We aim to access the safety and efficacy of TT consumption for bone health in postmenopausal women.

METHODS AND ANALYSIS

In this 12-week randomised double-blinded placebo-controlled trial for the effects of dietary TT supplementation in postmenopausal women, postmenopausal women aged 45 years and older with at least 1 year after menopause and bone mineral density T-score at the spine and/or hip 2.5 or more below the reference values will be randomly assigned to 3 daily supplements: (1) placebo group receiving 860 mg olive oil, (2) low TT group receiving 430 mg of 70% pure TTs (containing 300 mg TT) and (3) high TT group receiving 860 mg of 70% pure TTs (600 mg TT). The primary outcome measure will be urinary N-terminal telopeptide. The secondary outcome measures will be serum bone-specific alkaline phosphatase, receptor activator of nuclear factor-κB ligand, osteoprotegerin, urinary 8-hydroxy-2'-deoxyguanosine and quality of life. At 0, 6 and 12 weeks, the following will be assessed: (1) primary and secondary outcome measures; (2) serum TT and tocopherol concentrations; (3) physical activity and food frequency questionnaires. Liver function will be monitored every 6 weeks for safety. 'Intent-to-treat' principle will be employed for data analysis. A model of repeated measurements with random effect error terms will be applied. Analysis of covariance, χ² analysis and regression will be used for comparisons.

ETHICS AND DISSEMINATION

This study was approved by the Bioethics Committee of the Texas Tech University Health Sciences Center. The findings of this trial will be submitted to a peer-reviewed journal in the areas of bone or nutrition and international conferences.

TRIAL REGISTRATION NUMBER

NCT02058420; results.

Protection of oxidative stress induced apoptosis in osteosarcoma cells by dihydromyricetin through down-regulation of caspase activation and up-regulation of BcL-2

Current study was aimed to investigate the effect of dihydromyricetin on hydrogen peroxide induced oxidative stress in the osteosarcoma cells. MTT assay showed that hydrogen peroxide treatment at a concentration of 100 μM caused a significant (p < 0.005) reduction in the viability of MG63 cells. However, reduction in cell viability caused by 100 μM concentration of hydrogen peroxide was completely prevented on incubation with 30 μM dose of dihydromyricetin. Treatment with 100 μM concentration of hydrogen peroxide for 24 h led to condensation of chromatin material, rounding of cell shape and detachment of cells. The results from flow cytometry using annexin V-FITC and PI double staining showed apoptosis induction in 47.84 ± 5.21% cells on treatment with 100 μM concentration of hydrogen peroxide compared to 2.32 ± 0.54% in controlcells. The apoptotic alterations in MG63 cell morphology were prevented significantly on pre-treatment with 30 μM doses of dihydromyricetin for 48 h. Annexin V-FITC and PI staining showed reduction of hydrogen peroxide induced apoptotic cell percentage to 3.07 ± 0.86% on pre-treatment of MG63 cells with 30 μM dose of dihydromyricetin. Western blot analysis showed a significant increase in the activation of caspase-3 and -9 on treatment of MG63 cells for 24 h with 100 μM concentration of hydrogen peroxide. The expression level of Bcl-2 was decreased significantly by 100 μM concentration of hydrogen peroxide in MG63 cells. However, pre-treatment of MG63 cells with 30 μM dose of dihydromyricetin for 48 h significantly prevented hydrogen peroxide induced increase in caspase-3 and -9 levels and reduction in Bcl-2 level. Thus dihydromyricetin prevents hydrogen peroxide induced reduction in viability and induction of apoptosis in MG63 cells through down-regulation of caspase activation and up-regulation of Bcl-2 levels.

Proteomics approach to analyze protein profiling related with ADME/Tox in rat treated with Scutellariae radix and Coptidis rhizoma as well as their compatibility

ETHNOPHARMACOLOGICAL RELEVANCE

Scutellariae radix (Scutellaria baicalensis Georgi) and Coptidis rhizoma (Coptis chinensis Franch), known as traditional Chinese medicine (TCM), have been widely used with the effects of suppressing fever, dispelling dampness, purging fire and removing toxicosis. Owing to their unimaginable complexity, it is difficult to understand their pharmacokinetic properties in detail. The aim of this study was to develop an optimal proteomics approach to analyze the protein profiling related with ADME/Tox in rat liver treated with S. radix and C. rhizoma as well as their compatibility.

MATERIALS AND METHODS

Male rats were respectively administered the extracts of S. radix, C. rhizoma and their mixture for 7 days, and their liver tissue samples were prepared for the comparative proteomic analysis. The significantly differentially expressed proteins between the experimental groups and the control group were found and identified by 2-DE and MALDI-TOF-MS analyses. To validate the proteomic analysis results, glutathion peroxidase, catalase and betaine homocysteine methyl transferase were selected and confirmed by western blotting.

RESULTS

Seventy eight significantly differentially expressed proteins between the experimental groups and the control group were found and identified. By querying the relational databases, the identified differentially expressed proteins were summarized and classified into three groups, phase I drug metabolic enzymes, phase II drug metabolic enzymes and the rest proteins which mainly involve in energy metabolism, signal transduction and cytoskeleton. These proteins involved in ADME/Tox may be the targets for metabolic studies or markers for toxicity.

CONCLUSIONS

Our findings indicated S. radix and C. rhizoma as well as their compatibility can assuredly influence the expression of the proteins in rat liver. After administration, the majority of these expressions presented a downward trend, which may be closely related to the pharmacological properties of the medicine. The method in this study may open up a new road for the complementary tests for ADME/Tox properties of S. radix and C. rhizoma as well as their compatibility.

Correlation between bone mineral density and oxidative stress in postmenopausal women

BACKGROUND

Postmenopausal osteoporosis affects large fraction of elderly women. Oxidative stress (OS) appears to be involved in its pathogenesis. The scarcity of human studies focusing on the correlation between bone mineral density (BMD) and OS in postmenopausal women has prompted us to study on this issue.

MATERIALS AND METHODS

We conducted a cross sectional study in 95 subjects, between 21-65 years of age, including postmenopausal osteoporotic females (n = 35), healthy postmenopausal females (n = 30) and healthy females in reproductive age group (n = 30). We measured serum antioxidant activity of superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), and total antioxidant power (TAP). BMD was obtained at lumbar spine and femur neck by dual-energy X-ray absorptiometry scan. Osteoporosis was considered when subjects had a BMD of 2.5 standard deviations or more below the mean value for young adults.

RESULTS

Serum GPx, SOD, catalase and TAP level were found significantly lower in osteoporotic postmenopausal group as compared to healthy postmenopausal women and women in healthy reproductive age group healthy reproductive women (P < 0.005). but correlation between BMD and serum antioxidants were not found to be statistically significant (P > 0.005).

CONCLUSION

These findings support that oxidative stress plays an important role in pathogenesis of postmenopausal osteoporosis. We did not find any significant association between BMD and serum level of antioxidants (P > 0.05). The failure to detect this association does not preclude the role of OS in osteoporosis because OS is complex and dynamic process.

A review of dietary selenium intake and selenium status in Europe and the Middle East

This is a systematic review of existing data on dietary selenium (Se) intake and status for various population groups in Europe (including the United Kingdom (UK)) and the Middle East. It includes English language systematic reviews, meta-analyses, randomised controlled trials, cohort studies, cross-sectional and case-control studies obtained through PUBMED searches from January, 2002, to November, 2014, for European data and from 1990 to November 2014, for Middle Eastern data. Reports were selected if they included data on Se intake and status. The search identified 19 European/UK studies and 15 investigations in the Middle East that reported Se intake and Se concentration in water and/or food and 48 European/UK studies and 44 investigations in the Middle East reporting Se status. Suboptimal Se status was reported to be widespread throughout Europe, the UK and the Middle East, and these results agreed with previous reports highlighting the problem. Eastern European countries had lower Se intake than Western European countries. Middle Eastern studies provided varying results, possibly due to varying food habits and imports in different regions and within differing socioeconomic groups. In conclusion, Se intake and status is suboptimal in European and Middle Eastern countries, with less consistency in the Middle East.

Selenoproteins and selenium status in bone physiology and pathology

BACKGROUND

Emerging evidence supports the view that selenoproteins are essential for maintaining bone health.

SCOPE OF REVIEW

The current state of knowledge concerning selenoproteins and Se status in bone physiology and pathology is summarized.

MAJOR CONCLUSIONS

Antioxidant selenoproteins including glutathione peroxidase (GPx) and thioredoxin reductase (TrxR), as a whole, play a pivotal role in maintaining bone homeostasis and protecting against bone loss. GPx1, a major antioxidant enzyme in osteoclasts, is up-regulated by estrogen, an endogenous inhibitor of osteoclastogenesis. TrxR1 is an immediate early gene in response to 1α,25-dihydroxyvitamin D3, an osteoblastic differentiation agent. The combination of 1α,25-dihydroxyvitamin D3 and Se generates a synergistic elevation of TrxR activity in Se-deficient osteoblasts. Of particular concern, pleiotropic TrxR1 is implicated in promoting NFκB activation. Coincidentally, TrxR inhibitors such as curcumin and gold compounds exhibit potent osteoclastogenesis inhibitory activity. Studies in patients with the mutations of selenocysteine insertion sequence-binding protein 2, a key trans-acting factor for the co-translational insertion of selenocysteine into selenoproteins have clearly established a causal link of selenoproteins in bone development. Se transport to bone relies on selenoprotein P. Plasma selenoprotein P concentrations have been found to be positively correlated with bone mineral density in elderly women.

GENERAL SIGNIFICANCE

A full understanding of the role and function of selenoproteins and Se status on bone physiology and pathology may lead to effectively prevent against or modify bone diseases by using Se.

Effects of dried plum supplementation on bone metabolism in adult C57BL/6 male mice

Dietary supplementation of dried plum (DP) prevents bone loss and restores bone mass in osteopenic animal models. This study was designed to determine the effects of DP supplementation on bone metabolic activity over time using adult (6-month-old) male C57BL/6 mice (n = 40) receiving control (CON = AIN93 M) or CON+DP 25 % (w/w) diets for 4 or 12 weeks. After 4 weeks of treatment, animals consuming the DP diet had a higher whole-body bone mineral density, vertebral trabecular bone volume (BV/TV), and femoral cortical thickness compared to the CON animals. In the distal metaphysis of the femur, BV/TV was increased in the DP-treated animals, but only after 12 weeks. Bone histomorphometric analyses revealed that DP decreased osteoblast surface (67 %) and osteoclast surface (62 %) at 4 weeks, but these surfaces normalized to the CON animals by 12 weeks. Coincident with these changes, the mineralizing surface (MS/BS) and cancellous bone formation rate (BFR/BS) were reduced at 4 weeks in the DP group compared to the CON, but by 12 weeks of DP supplementation, BFR/BS (~twofold) and MS/BS (~1.7-fold) tended to be increased (p < 0.10). The relative abundance of RNA for key regulators of osteoblast and osteoclast differentiation and indicators of osteoblast activity were reduced in the DP group at 4 weeks with no difference between groups at 12 weeks. These results indicate that supplementing the diet with DP initially suppressed cancellous bone turnover, but a biphasic response occurs over time, resulting in a positive effect on bone mass and structure.

The effect of epigallocatechin-3-gallate (EGCG) on human alveolar bone cells both in vitro and in vivo

OBJECTIVE

The effects of epigallocatechin-3-gallate (EGCG), a major catechin in green tea, on human and mouse osteoblasts remain controversial. This study investigated the direct effects of EGCG on human alveolar bone-derived cells (hABCs) both in vitro and in vivo.

DESIGN

hABCs which were collected from eight children (aged 7-9 years, seven males and one female) were treated with EGCG at various concentrations (1, 5, 10, 25, and 50μM), and a proliferation assay, flow cytometric analysis for apoptosis evaluation, migration assay, and in vitro osteogenic differentiation were performed. hABCs that were pretreated with 10μM EGCG and mixed with calcium phosphate carrier combined with EGCG (0.1, 0.5, or 1.5mg) in vivo were transplanted into immunodeficient mouse. Histological staining, quantitative gene expressions, and alkaline phosphatase activity were evaluated in the retrieved transplants.

RESULTS

The proliferation and migration were decreased when EGCG was present at over 25μM. The osteogenic differentiation increased slightly when EGCG was present at up to 10μM, and clearly decreased for higher concentrations of EGCG. In vivo, the potential for hard-tissue formation was slightly higher for the group with 0.1mg of EGCG than for the control group, and decreased sharply for higher concentrations of EGCG.

CONCLUSION

The present observations suggest that EGCG at a low concentration can slightly enhance the osteogenic effect in vivo, whereas at a higher concentration it can prevent the osteogenic differentiation of hABCs both in vitro and in vivo.

Dexamethasone-induced selenoprotein S degradation is required for adipogenesis

Although adipogenesis is associated with induction of endoplasmic reticulum (ER) stress, the role of selenoprotein S (SEPS1), an ER resident selenoprotein known to regulate ER stress and ER-associated protein degradation, is unknown. We found an inverse relationship between SEPS1 level in adipose tissue and adiposity in mice. While SEPS1 expression was increased during adipogenesis, a markedly reduced SEPS1 protein level was found in the early phase of adipogenesis due to dexamethasone (DEX)-induced proteosomal degradation of SEPS1. Overexpression of SEPS1 in the early phase of cell differentiation resulted in impairment of adipogenesis with reduced levels of CCAAT/enhancer binding protein α and other adipocyte marker genes during the course of adipogenesis. Conversely, knockdown of SEPS1 resulted in the promotion of adipogenesis. Additionally, altered SEPS1 expression was associated with changes in expression of ER stress marker genes in the early phase of adipogenesis, and ubiquitin-proteasome system (UPS)-related ubiquitination and proteasome function. Our study reveals that SEPS1 is a novel anti-adipogenic selenoprotein that modulates ER stress- and UPS-dependent adipogenesis. Our results also identifies a novel function of DEX in the regulation of adipogenesis through induction of SEPS1 degradation. Taken together, DEX-dependent degradation of SEPS1 in the early phase of adipogenesis is necessary for initiating ER stress- and UPS-dependent maturation of adipocytes.

Selenium in bone health: roles in antioxidant protection and cell proliferation

Selenium (Se) is an essential trace element for humans and animals, and several findings suggest that dietary Se intake may be necessary for bone health. Such findings may relate to roles of Se in antioxidant protection, enhanced immune surveillance and modulation of cell proliferation. Elucidation of the mechanisms by which Se supports these cellular processes can lead to a better understanding of the role of this nutrient in normal bone metabolism. This article reviews the current knowledge concerning the molecular functions of Se relevant to bone health.

Selenium protects bone marrow stromal cells against hydrogen peroxide-induced inhibition of osteoblastic differentiation by suppressing oxidative stress and ERK signaling pathway

Osteoporosis is a bone disease that leads to an increased risk of fracture. Oxidative stress may play a major role in the development of osteoporosis in part by inhibiting osteoblastic differentiation of bone marrow stromal cells (MSCs). Some evidence suggested that antioxidant selenium could prevent osteoporosis, but the underlying mechanism remains unclear. In this work, the effect of sodium selenite on H₂O₂-induced inhibition of osteoblastic differentiation of primary rat bone MSCs and the related mechanisms were examined. Pretreatment with selenite inhibited the adverse effect of H₂O₂ on osteoblastic differentiation of MSCs, based on alkaline phosphatase activity, gene expression of type I collagen and osteocalcin, and matrix mineralization. In addition, selenite pretreatment also suppressed the activation of extracellular signal-regulated kinase (ERK) induced by H₂O₂. The above effects were mediated by the antioxidant effect of selenite. Selenite enhanced the gene expression and activity of glutathione peroxidase, reversed the decreased total antioxidant capacity and reduced glutathione, and suppressed reactive oxygen species production and lipid peroxidation level in H₂O₂-treated MSCs. These results showed that selenite protected MSCs against H₂O₂-induced inhibition of osteoblastic differentiation through inhibiting oxidative stress and ERK activation, which provided, for the first time, the mechanistic explanation for the negative association of selenium status and risk of osteoporosis in terms of bone formation.

The effects of virgin coconut oil on bone oxidative status in ovariectomised rat

Virgin coconut oil (VCO) was found to have antioxidant property due to its high polyphenol content. The aim of this study was to investigate the effect of the virgin coconut oil on lipid peroxidation in the bone of an osteoporotic rat model. Normal female Sprague-Dawley rats aged 3 months old were randomly divided into 4 groups, with 8 rats in each group: baseline, sham, ovariectomised (OVX) control group, and OVX given 8% VCO in the diet for six weeks. The oxidative status of the bone was assessed by measuring the index of lipid peroxidation, which is malondialdehyde (MDA) concentration, as well as the endogenous antioxidant enzymes glutathione peroxidase (GPX) and superoxide dismutase (SOD) in the tibia at the end of the study. The results showed that there was a significant decrease in MDA levels in the OVX-VCO group compared to control group. Ovariectomised rats treated with VCO also had significantly higher GPX concentration. The SOD level seemed to be increased in the OVX-VCO group compared to OVX-control group. In conclusion, VCO prevented lipid peroxidation and increased the antioxidant enzymes in the osteoporotic rat model.

Thyroid hormone metabolism in skeletal development and adult bone maintenance

Metabolism of thyroid hormones by the type 2 and type 3 iodothyronine deiodinases (D2, D3) in T3-responsive target cells is a sophisticated mechanism that helps to maintain local T3 concentrations and facilitates T3 action in a cell-specific manner that is independent of circulating thyroid hormone concentrations. Recent findings have demonstrated an essential physiological role for the thyroid hormone-activating enzyme D2 in the optimization of bone mineralization and strength. Emerging population studies have also identified the genes encoding D2 and the thyroid hormone-inactivating enzyme D3 as susceptibility loci for osteoarthritis. These new data reveal an essential role for the local control of T3 availability in osteoblasts and chondrocytes during maintenance and repair of bone and cartilage.

Implantation of green tea catechin α-tricalcium phosphate combination enhances bone repair in rat skull defects

The purpose of the present study is to investigate effects of the combination of epigallocatechin-3-gallate (EGCG) and α-tricalcium phosphate (α-TCP) on bone regenerative capacity in a bilateral rat calvarial bone defect model.

MATERIALS AND METHODS

Bilateral 5-mm-diameter calvarial defects were created in adult male Wistar rats and filled with preparations of EGCG (0, 0.1, 0.2, 0.4 mg) combined with α-TCP particles. This was done by dissolving EGCG in 100% ethanol (50 μL/14 mg) and dropping under sterile condition. The control group was left unfilled (n = 8). The animals were sacrificed at 2 and 4 weeks. Radiological images were taken, and histological analysis was done. Six animals from control (0 mg EGCG + α-TCP) group and (0.2 mg EGCG+ α-TCP) group were labeled with fluorescent dyes and histomorphometrically analyzed (n = 6) at 2 and 4 weeks.

RESULTS

Histomorphometric analysis revealed that the combination of EGCG and α-TCP at doses of 0.1 and 0.2 mg yielded significantly more new bone formation than untreated control group at 2 and 4 weeks (p > 0.05). Mineral apposition rate at 0.2-TCP group was enhanced compared with the one of the positive control α-TCP group at 4 weeks (p > 0.05).

CONCLUSION

The combination of α-TCP particles and 0.2 mg EGCG stimulates maximum bone regeneration in rat calvarial defects, and this combination would be potentially effective as bone graft material.

Antioxidant defense and apoptotic effectors in ascorbic acid and β-glycerophosphate-induced osteoblastic differentiation

MC3T3-E1 cells grown in the presence of ascorbic acid and β-glycerophosphate (AA/β-GP) express alkaline phosphatase and produce an extensive collagenous extracellular matrix. Differentiated MC3T3-E1 cells are more sensitive to hydrogen peroxide-induced oxidative stress than undifferentiated cells. In this study, we compared the profile of antioxidant enzymes and molecular markers of apoptosis in undifferentiated and differentiated MC3T3-E1 cells (cell differentiation was induced by treatment with AA/β-GP). Differentiated osteoblasts showed lower expression and activity of catalase, glutathione S-transferase and glutathione peroxidase. The total superoxide dismutase activity and the expression of Cu/Zn superoxide dismutase were also lower, while the expression of Mn superoxide dismutase was higher in differentiated osteoblasts. The level of malondialdehyde, a widely used marker for oxidative stress, was lower in the AA/β-GP group compared with control cells, but this difference was not significant. Western blotting showed that treatment with AA/β-GP increased the Bax/Bcl-2 ratio used as an index of cellular vulnerability to apoptosis. In addition, the activities of caspases 3, 8 and 9 and cleaved poly (ADP) ribose polymerase were significantly higher in differentiated cells. These findings provide new insights into how changes in the activities of major antioxidant enzymes and in the signaling pathways associated with apoptosis may influence the susceptibility of bone cells to oxidative stress.

Green tea and bone health: Evidence from laboratory studies

Osteoporosis is a major health problem in the elderly. Epidemiological evidence has shown an association between tea consumption and the prevention of bone loss in the elderly population. Ingestion of green tea and green tea bioactive compounds may be beneficial in mitigating bone loss of this population and decreasing their risk of osteoporotic fractures. This review describes the effect of green tea with its bioactive components on bone health with an emphasis on the following: (i) the etiology of osteoporosis, (ii) evidence of osteo-protective impacts of green tea on bone mass and microarchitecture in various bone loss models in which induced by aging, sex hormone deficiency, and chronic inflammation, (iii) discussion of impacts of green tea on bone mass in two obesity models, (iv) observation of short-term green tea supplementation given to postmenopausal women with low bone mass, (v) possible mechanisms for the osteo-protective effects of green tea bioactive compounds, and (vi) a summary and future research direction of green tea and bone health.

Germain DL, Galton VA, Williams GR. Optimal bone strength and mineralization requires the type 2 iodothyronine deiodinase in osteoblasts

Hypothyroidism and thyrotoxicosis are each associated with an increased risk of fracture. Although thyroxine (T4) is the predominant circulating thyroid hormone, target cell responses are determined by local intracellular availability of the active hormone 3,5,3'-L-triiodothyronine (T3), which is generated from T4 by the type 2 deiodinase enzyme (D2). To investigate the role of locally produced T3 in bone, we characterized mice deficient in D2 (D2KO) in which the serum T3 level is normal. Bones from adult D2KO mice have reduced toughness and are brittle, displaying an increased susceptibility to fracture. This phenotype is characterized by a 50% reduction in bone formation and a generalized increase in skeletal mineralization resulting from a local deficiency of T3 in osteoblasts. These data reveal an essential role for D2 in osteoblasts in the optimization of bone strength and mineralization.

Green tea polyphenols and Tai Chi for bone health: designing a placebo-controlled randomized trial

BACKGROUND

Osteoporosis is a major health problem in postmenopausal women. Evidence suggests the importance of oxidative stress in bone metabolism and bone loss. Tea consumption may be beneficial to osteoporosis due to its antioxidant capability. However, lack of objective data characterizing tea consumption has hindered the precise evaluation of the association between tea ingestion and bone mineral density in previous questionnaire-based epidemiological studies. On the other hand, although published studies suggest that Tai Chi (TC) exercise can benefit bone health and may reduce oxidative stress, all studies were conducted using a relatively healthy older population, instead of a high-risk one such as osteopenic postmenopausal women. Therefore, this study was designed to test an intervention including green tea polyphenol (GTP) and TC exercise for feasibility, and to quantitatively assess their individual and interactive effects on postmenopausal women with osteopenia.

METHODS/DESIGN

One hundred and forty postmenopausal women with osteopenia (defined as bone mineral density T-score at the spine and/or hip between 1 to 2.5 SD below the reference database) were randomly assigned to 4 treatment arms: (1) placebo group receiving 500 mg medicinal starch daily, (2) GTP group receiving 500 mg of GTP per day, (3) placebo+TC group receiving both placebo treatment and TC training (60-minute group exercise, 3 times per week), and (4) GTP+TC group receiving both GTP and TC training for 24 weeks. The outcome measures were bone formation biomarker (serum bone alkaline phosphatase), bone resorption biomarker (serum tartrate resistant acid phosphatase), and oxidative DNA damage biomarker (urinary 8-hydroxy-2'-deoxyguanosine). All outcome measures were determined at baseline, 4, 12, and 24 weeks. Urinary and serum GTP concentrations were also determined at baseline, 4, 12, and 24 weeks for bioavailability. Liver function was monitored monthly for safety. A model of repeated measurements with random effect error terms was applied. Traditional procedures such as ANCOVA, chi-squared analysis, and regression were used for comparisons.

DISCUSSION

We present the rationale, design, and methodology of a placebo-controlled randomized trial to investigate a new complementary and alternative medicine strategy featuring a dietary supplement and a mind-body exercise for alleviating bone loss in osteopenic postmenopausal women.

Green tea and bone metabolism

Osteoporosis is a major health problem in both elderly women and men. Epidemiological evidence has shown an association between tea consumption and the prevention of age-related bone loss in elderly women and men. Ingestion of green tea and green tea bioactive compounds may be beneficial in mitigating bone loss of this population and decreasing their risk of osteoporotic fractures. This review describes the effect of green tea or its bioactive components on bone health, with an emphasis on (i) the prevalence and etiology of osteoporosis; (ii) the role of oxidative stress and antioxidants in osteoporosis; (iii) green tea composition and bioavailability; (iv) the effects of green tea and its active components on osteogenesis, osteoblastogenesis, and osteoclastogenesis from human epidemiological, animal, as well as cell culture studies; (v) possible mechanisms explaining the osteoprotective effects of green tea bioactive compounds; (vi) other bioactive components in tea that benefit bone health; and (vii) a summary and future direction of green tea and bone health research and the translational aspects. In general, tea and its bioactive components might decrease the risk of fracture by improving bone mineral density and supporting osteoblastic activities while suppressing osteoclastic activities.

Green tea polyphenols mitigate deterioration of bone microarchitecture in middle-aged female rats

Our previous study demonstrated that green tea polyphenols (GTP) benefit bone health in middle-aged female rats without (sham, SH) and with ovariectomy (OVX), because of GTP's antioxidant capacity. The current study further evaluates whether GTP can restore bone micro-structure in both gonad-intact and gonadal-hormone-deficient middle-aged female rats. A 16-week study was performed based on a 2 (SH vs. OVX)x3 (no GTP, 0.1% GTP, and 0.5% GTP in drinking water) factorial design using 14-month-old female rats (n=10/group). An additional 10 rats were euthanized at the beginning of study to provide baseline parameters. Analysis using dual-energy X-ray absorptiometry, histomorphometry, and micro-computed tomography showed that GTP supplementation resulted in (a) increased trabecular volume, thickness, number, and bone formation of proximal tibia, periosteal bone formation rate of tibia shaft, and cortical thickness and area of femur, and (b) decreased trabecular separation and bone erosion of proximal tibia, and endocortical bone eroded surface of tibia shaft. We concluded that drinking water supplemented with GTP mitigated deterioration of bone microarchitecture in both intact and ovariectomized middle-aged female rats by suppressing bone erosion, enhancing bone formation, and modulating endocortical and cancellous bone compartments, resulting in a larger net bone volume.

The influence of auranofin, a clinically established antiarthritic gold drug, on bone metabolism: analysis of its effects on human multipotent adipose-derived stem cells, taken as a model

Auranofin is a gold-based antiarthritic drug in clinical use for more that 25 years. However, in spite of a long established use, its specific effects on bone metabolism are still greatly controversial. We have analyzed in vitro the actions of auranofin on human multipotent adipose-derived stem (hMADS) cells, used as a model for bone metabolism, since these cells were reported to undergo osteogenesis both in vitro and in vivo. Cytotoxicity of auranofin on hMADS cells, differentiated into osteoblasts, was initially assessed. Thereafter, the consequences of exposure to nontoxic but clinically relevant auranofin concentrations were analyzed by monitoring the seleno-protein glutathione peroxidase 3 or alkaline phosphatase, a characteristic biomarker of osteogenesis. Notably, we found that chronic treatment with auranofin alters only weakly the levels of alkaline phosphatase, thus implying an overall modest effect on osteogenesis. In contrast, auranofin turned out to greatly affect glutathione peroxidase 3 activity. The possible medical implications of these findings are discussed.

Iodothyronine deiodinase enzyme activities in bone

Euthyroid status is essential for normal skeletal development and maintenance of the adult skeleton, but the mechanisms which control supply of thyroid hormone to bone cells are poorly understood. Thyroid hormones enter target cells via monocarboxylate transporter-8 (MCT8), which provides a functional link between thyroid hormone uptake and metabolism in the regulation of T3-action but has not been investigated in bone. Most circulating active thyroid hormone (T3) is derived from outer ring deiodination of thyroxine (T4) mediated by the type 1 deiodinase enzyme (D1). The D2 isozyme regulates intra-cellular T3 supply and determines saturation of the nuclear T3-receptor (TR), whereas a third enzyme (D3) inactivates T4 and T3 to prevent hormone availability and reduce TR-saturation. The aim of this study was to determine whether MCT8 is expressed in the skeleton and whether chondrocytes, osteoblasts and osteoclasts express functional deiodinases. Gene expression was analyzed by RT-PCR and D1, D2 and D3 function by sensitive and highly specific determination of enzyme activities. MCT8 mRNA was expressed in chondrocytes, osteoblasts and osteoclasts at all stages of cell differentiation. D1 activity was undetectable in all cell types, D2 activity was only present in mature osteoblasts whereas D3 activity was evident throughout chondrocyte, osteoblast and osteoclast differentiation in primary cell cultures. These data suggest that T3 availability especially during skeletal development may be limited by D3-mediated catabolism rather than by MCT8 mediated cellular uptake or D2-dependent T3 production.

Protective effect of green tea polyphenols on bone loss in middle-aged female rats

Recent studies have suggested that green tea polyphenols (GTP) are promising agents for preventing bone loss in women. Findings that GTP supplementation resulted in increased urinary GTP concentrations and bone mass via an increase of antioxidant capacity and/or a decrease of oxidative stress damage suggest a significant role of GTP in bone health of women.

INTRODUCTION

Recent studies suggested that green tea polyphenols (GTP) are promising agents for preventing bone loss in women. However, the mechanism related to the possible protective role of GTP in bone loss is not well understood.

METHODS

This study evaluated bioavailability, mechanisms, bone mass, and safety of GTP in preventing bone loss in middle-aged rats without (sham, SH) and with ovariectomy (OVX). A 16-week study of 2 (SH vs. OVX) x 3 (no GTP, 0.1% GTP, and 0.5% GTP in drinking water) factorial design using 14-month-old female rats (n = 10/group) was performed. An additional 10 rats in baseline group were euthanized at the beginning of study to provide baseline parameters.

RESULTS

There was no difference in femur bone mineral density between baseline and the SH+0.5% GTP group. Ovariectomy resulted in lower values for liver glutathione peroxidase activity, serum estradiol, and bone mineral density. GTP supplementation resulted in increased urinary epigallocatechin and epicatechin concentrations, liver glutathione peroxidase activity and femur bone mineral density, decreased urinary 8-hydroxy-2'-deoxyguanosine and urinary calcium levels, but no effect on serum estradiol and blood chemistry levels.

CONCLUSION

We conclude that a bone-protective role of GTP may contribute to an increase of antioxidant capacity and/or a decrease of oxidative stress damage.

Responses of differentiated MC3T3-E1 osteoblast-like cells to reactive oxygen species

MC3T3-E1 osteoblast-like cells represent a suitable model for studying osteogenic development in vitro. The current investigation extends our previous work on the response of these cells to hydrogen peroxide by considering the effects of reactive oxygen species from other sources, and by determining whether differentiation alters sensitivity to oxidative damage. Aspects of hydrogen peroxide-mediated apoptotic and necrotic death were also examined. Cell viability was determined using the Alamar Blue assay; and accompanying morphological changes monitored by phase-contrast microscopy. Sensitivity to hydrogen peroxide increased significantly in cultures which had been induced to differentiate. Hydrogen peroxide and copper (II) ions, when combined, produced greater damage than hydrogen peroxide alone, whilst the hydroxyl radical scavengers mannitol or dimethylsulphoxide had no effect. Cyclosporin A and nicotinamide afforded partial protection. The tryptophan metabolite, 3-hydroxykynurenine significantly reduced viability, although 3-hydroxyanthranilic acid did not. The xanthine/xanthine oxidase system also reduced cell viability, an effect prevented by catalase but potentiated by superoxide dismutase. S-nitroso-N-acetylpenicillamine did not impair viability at the concentrations tested. Cultures were resistant to mitochondrial poisoning by potassium cyanide, but succumbed to 24-h exposures to 3-nitropropionic acid (1 mM). The results reveal a differential sensitivity of MC3T3-E1 cells to hydrogen peroxide-induced oxidative stress, an enhancement of sensitivity by cellular differentiation, and a potential preference for the glycolytic pathway by MC3T3-E1 cells. This study gives new insight into how bone cells may succumb to the toxic effects of oxidative stress generated by different stimuli and has relevance to conditions such as osteoporosis.

Total oxidative/anti-oxidative status and relation to bone mineral density in osteoporosis

The aim of this study was to evaluate the total antioxidant status (TAS), total oxidative status (TOS) and oxidative stress index (OSI) in patients with postmenopausal osteoporosis. We also investigate the relation between bone mineral density and oxidative/antioxidative parameters. Thirty-nine patients with osteoporosis and 26 healthy controls were included in the study. Plasma TAS, TOS levels were determined by using a novel automated methods. Plasma TOS and OSI value were significantly higher, and plasma TAS level was lower in patients than in healthy controls (P < 0.001 for all). There was a significant negative correlation between OSI and BMD in lumbar and femoral neck region (r = -0.63, P < 0.001; r = 0.40, P = 0.018). The results of this study indicated that increased osteoclastic activity and decreased osteoblastic activity may be associated with an imbalance between oxidant and antioxidant status in postmenopausal osteoporosis. Therefore, supplementation of antioxidant-enriched diet to the therapy might shed light on the development of novel therapeutic strategies for osteoporosis.

Iodine deficiency mitigates growth retardation and osteopenia in selenium-deficient rats

Selenium deficiency is associated with impaired bone metabolism and osteopenia in rats. However, it is not known how combined selenium and iodine deficiency affects bone metabolism. Therefore, we investigated the effect of selenium and iodine deficiency on bone metabolism in 2nd-generation selenium- and iodine-deficient rats. Selenium-deficient (Se-), iodine-deficient (I-), selenium- and iodine-deficient (Se-/I-), and control rats (Se+/I+), were pair-fed their respective diets until they were 74 d old. Each pair-fed rat was fed a selenium-adequate diet in the same amount as that consumed the day before by its selenium-deficient counterpart, taking food spillage into account. The skeletal phenotype was analyzed by dual energy X-ray absorptiometry, histomorphometry, and bone metabolism markers. Erythrocyte glutathione peroxidase activity (Gpx) and plasma thyroid hormones were measured to assess selenium and iodine status, respectively. In both Se-/I+ and Se-/I- rats, Gpx was reduced by 99% compared with pair-fed Se+/I+ and Se+/I- rats (P < 0.001). Iodine deficiency reduced plasma thyroxine by 64% in the 2 iodine-deficient groups (P < 0.001). Body weight, tail length, plasma insulin-like growth factor, pituitary growth hormone concentration, and femur and tibia bone mineral density were significantly greater in the Se-/I- rats than in the Se-/I+ rats. This study shows that iodine deficiency mitigated growth retardation and osteopenia in 2nd-generation selenium-deficient rats and suggests that adequate selenium status should be ensured before measures are taken to correct iodine deficiency.

The effect of vitamin K2 on bone metabolism in aged female rats

Reactive oxygen species (ROS) may contribute to aging and osteoporosis resulting from marked decreases in plasma antioxidants in aged osteoporotic women. On the other hand, high-dose vitamin K2 (menaquinone-4: menatrenone, MK-4) supplementation has been reported to reduce ovariectomy-induced bone loss in rats and to decrease osteoporotic fracture in postmenopausal women. However, the mechanism by which vitamin K2 prevents osteoporosis is unclear. Recently, vitamin K2 has been suggested to preserve antioxidant activity as a novel function. Therefore, we investigated the effect of vitamin K2 on the osteoporosis of aged rats by evaluating the relationships between serum antioxidant levels and bone metabolism. Aged female rats exhibited significantly lower serum alkaline phosphatase activity and osteocalcin level, together with lower serum levels of antioxidants such as 17beta-estradiol, macrophage migration inhibitory factor (MIF) and glutathione peroxidase (GPx) activity, as compared with young female rats. On the other hand, vitamin K2 supplementation (500 mg/kg, food intake) for 98 days led to a significantly increased serum vitamin K2 level (3,045+/-915 ng/ml in the vitamin K2 supplemented group vs. 4.6+/-3.4 ng/ml in the control diet group; P<0.0001) with increased serum alkaline phosphatase activity and MIF level (P<0.05). Unexpectedly, however, it failed to increase the serum level of antioxidants such as GPx. Nor did it affect bone metabolism markers such as osteocalcin and osteopontin, which were significantly lower than in the young female rats (P<0.05). Finally, the histomorphometric properties of the proximal tibia in the femur were not altered by vitamin K2. These results suggest that high-dose vitamin K2 supplementation neither improves lowered antioxidant levels nor stimulates bone formation in aged rats.

Selenium, the thyroid, and the endocrine system

Recent identification of new selenocysteine-containing proteins has revealed relationships between the two trace elements selenium (Se) and iodine and the hormone network. Several selenoproteins participate in the protection of thyrocytes from damage by H(2)O(2) produced for thyroid hormone biosynthesis. Iodothyronine deiodinases are selenoproteins contributing to systemic or local thyroid hormone homeostasis. The Se content in endocrine tissues (thyroid, adrenals, pituitary, testes, ovary) is higher than in many other organs. Nutritional Se depletion results in retention, whereas Se repletion is followed by a rapid accumulation of Se in endocrine tissues, reproductive organs, and the brain. Selenoproteins such as thioredoxin reductases constitute the link between the Se metabolism and the regulation of transcription by redox sensitive ligand-modulated nuclear hormone receptors. Hormones and growth factors regulate the expression of selenoproteins and, conversely, Se supply modulates hormone actions. Selenoproteins are involved in bone metabolism as well as functions of the endocrine pancreas and adrenal glands. Furthermore, spermatogenesis depends on adequate Se supply, whereas Se excess may impair ovarian function. Comparative analysis of the genomes of several life forms reveals that higher mammals contain a limited number of identical genes encoding newly detected selenocysteine-containing proteins.

Bone metabolism and oxidative stress in postmenopausal rats with iron overload

Osteoporosis is associated with many etiological causes such as nutrition, cytokines, hormones, and aging. Recently, reactive oxygen species (ROS) are considered to be responsible for the aging process and osteoporosis. We investigated the relationship between ROS and bone metabolism in young female and postmenopausal rats, by using dietary iron overload and several indices including bone metabolic markers, oxidative stress and antioxidant markers, and cytokines. Postmenopausal rats exhibited significant decreases in serum alkaline phosphatase activity and the level of osteocalcin as bone formation markers compared with young female rats; however, urinary excretion of deoxypyridinoline, a bone resorption marker, did not change. On the other hand, a 5% iron lactate diet for 4 weeks in postmenopausal rats led to significantly increased excretion of urinary deoxypyridinoline and 8-hydroxy-2'-deoxyguanosine (8-OHdG) but not serum alkaline phosphatase activity. Interestingly, the diet induced significant increases of serum osteopontin and TGF-beta1, augumenting osteoclast-mediated bone resorption through the RANK/RANKL pathway [J. Clin. Invest. 112 (2003) 181]. TGF-beta1 showed a negative correlation with serum glutathione peroxidase (GPx) activity (r = -0.674, P < 0.003), but a positive correlation with the serum iron level (r = 0.836, P < 0.0001). Taken together, these results suggest for the first time that oxidative stress could be involved in the pathogenesis of metabolic bone diseases such as osteoporosis as demonstrated by analysis of the relationship between bone metabolism and oxidative stress.