Effects of Tributyltin (TBT) on Rat Bone and Mineral Metabolism.

BACKGROUND/AIMS: Tributyltin (TBT) is an organotin (OTs) and biohazard organometallic pollutant. Recently our group has shown that TBT, even in very low doses, has deleterious effects on several tissues most likely due to its role as an endocrine-disrupting molecule. Other studies have confirmed that OT exposure could be responsible for neural, endocrine, and reproductive dysfunctions via in vitro and in vivo models. However, TBT effects on bone lack concise data despite the fact that bone turnover is regulated by endocrine molecules, such as parathormone (PTH), estrogen (E2), etc. Our group has already shown that TBT disrupts adrenal and female gonadal functions. METHODS: We studied the effects of TBT on bone metabolism and structure using DXA, microCT scan, and SEM. We also determined the calcium (Ca²âº) and phosphate (Pi) metabolism in TBT-treated rats as well as some biomarkers for bone formation and resorption. RESULTS: Surprisingly, we found that TBT leads to higher bone mineral density (BMD) although lesions in spinal bone were observed by either microCT scan or SEM. Biomarkers for bone resorption, such as the urinary deoxipyridinolines (DPD) excretion ratio was increased in TBT-treated animals versus mock-treated controls. Osteocalcin (OC) and alkaline phosphatase (AP) are markers of bone formation and are also elevated suggesting that the bone matrix suffers from a higher turnover. Serum Ca²âº (total and ionized) do not changed by TBT treatment although hypercalciuria is observed. CONCLUSION: It is known that Sn atoms have three valence states (Sn²âº, Sn³âº, and Sn4⁺); hence, we hypothesized that Sn (more likely Sn²âº) could be competing with Ca²âº and/or Mg²âº in hydroxyapatite mineral matrix to disturb bone turnover. Further work is needed to confirm this hypothesis.

Vitamin K Supplementation Modulates Bone Metabolism and Ultra-Structure of Ovariectomized Mice.

BACKGROUND/AIMS: Osteoporosis is a bone metabolic disease that affects mostly post-menopausal women. There has been shown that vitamin K (VK) supplementation during menopause may decrease bone loss as well as risk of bone breaking. Aiming to clarify the beneficial role of VK in bone metabolism during menopause, we investigated mineral metabolism and bone ultrastructure of ovariectomized (OVX) mice. METHODS: To determine the effects chronic use of VK in bone structure and mineral metabolism in OVX mice, we used several methods, such as DXA, µCTScan, and SEM as well as biomolecular techniques, such as ELISA and qRT-PCR. In addition, complete analysis of serum hormonal and other molecules associated to bone and lipid metabolism were evaluated overview the effects of VK in menopause murine model. RESULTS: VK treatment significantly affects Pi metabolism independently of OVX, changing Pi plasma, urinary output, balance, and Pi bone mass. Interestingly, VK also increased VLDL in mice independently of castration. In addition, VK increased compact bone mass in OVX mice when we evaluated it by DXA, histomorphometry, µCTScanning. VK increased bone formation markers, osteocalcin, HYP- osteocalcin, and AP whereas it decreased bone resorption markers, such as urinary DPD/creatinine ratio and plasmatic TRAP. Surprisingly, SEM images revealed that VK treatment led to amelioration of microfractures observed in OVX untreated controls. In addition, SHAM operated VK treated mice exhibited higher number of migrating osteoblasts and in situ secretion of AP. OVX led to decreased to in situ secretion of AP that was restored by VK treatment. Moreover, VK treatment increased mRNA expression of bone Calbindin 28KDa independently of OVX. CONCLUSION: VK treatment in OVX mice exhibited beneficial effects on bone ultrastructure, mostly by altering osteoblastic function and secretion of organic bone matrix. Therefore, VK could be useful to treat osteopenic/osteoporotic patients.

Role of APOE Gene in Bone Mineral Density and Incidence of Bone Fractures in Brazilian Postmenopausal Women.

Osteoporosis is one of the major diseases that affects mostly postmenopausal women. Despite being a multifactorial disease, some genes have been shown to play an important role in osteoporosis. Bone mineral density (BMD) is still largely used to diagnose it, although many other biomarkers are used to better follow the disease onset. It has been shown that the apolipoprotein E (APOE) gene could be a biomarker for risk of fractures as well as to predict lower BMD in patients with osteoporosis. The human APOE gene encodes 3 protein isoforms called ApoE2, ApoE3, and ApoE4, resulting in 4 possible genotypes, because they are a product of a single nucleotide polymorphism found in this gene. So far, the APOE4 allele has been associated with low BMD in postmenopausal women and to incidence of bone breaking in older women. This study aimed to investigate the role of ApoE isoforms in a cohort of 413 postmenopausal Brazilian women. These patients were randomly recruited, clinically examined, and subjected to dual-energy X-ray absorptiometry to measure their BMD. Patients were further grouped as normal BMD (T-score < 0.5) or low BMD (T-score > 1.0, osteopenic or osteoporotic). Patients with osteopenia or osteoporosis were further genotyped for APOE alleles as well as tested for many serum bone turnover biomarkers. Our data showed that presence of the APOE3 allele was associated with both higher BMDs and higher serum concentrations of osteocalcin and alkaline phosphatase, biomarkers for bone formation. On the other hand, the APOE2 and APOE4 alleles were associated with lower BMD as well as higher levels of serum C-terminus collagen peptide and urinary deoxipyridinolines, biomarkers for bone resorption. However, these effects on lower BMD and bone resorption biomarkers observed in either APOE2 or APOE4 alleles were eliminated when patients' genotype carried the APOE3 allele. Codominance of the APOE3 allele was also associated with lesser cases of bone fractures in these patients within a 5-year follow-up. In conclusion, our data show that APOE4 may be associated with lower bone formation as well as increased risk of osteoporosis and bone fractures, whereas APOE3 seems to decrease lowering BMD in postmenopausal women, and its presence seemed to lower the incidence of bone breaking in patients with osteoporosis.

Estrogen receptor α polymorphism is associated with dementia in a Brazilian cohort.

The growth of the elderly population is a worldwide phenomenon and it is associated with chronic diseases, including dementia. In this scenario, the present study aimed to evaluate a possible association of estrogen receptor α polymorphisms with dementia in a Brazilian cohort. The subject sample was divided into two groups, control (n = 105) and case (n = 73), according to analysis of two predictive dementia tests (MMSE and CDR). The genotyping for the ERα PvuII (c.454-397T>C, rs2234693) and XbaI (c.454-351A>G, rs9340799) polymorphisms were performed by polymerase chain reaction-restriction fragment length polymorphism. The ERα PvuII pp genotype was associated with higher odds ratio for dementia (OR = 3.42, 95% CI = 1.33-8.77, p = 0.01, in a model including covariates. A linear regression model identified significant associations of the ERα PvuII genotypes (independent variable) with CDR scale (dependent variable), ß = 0.26 and p = 0.001. In conclusion, estrogen receptor α PvuII polymorphism is associated with dementia in a Brazilian cohort. This finding may be useful for the identification of a possible set of significant genetic and clinical biomarkers for better understanding pathophysiology, early diagnosis and management of dementia.

Association of PvuII and XbaI polymorphisms on estrogen receptor alpha (ESR1) gene to changes into serum lipid profile of post-menopausal women: Effects of aging, body mass index and breast cancer incidence.

Estrogen is a steroidal hormone involved in several physiological functions in the female body including regulation of serum lipid metabolism and breast cancer (BC). Estrogen actions on serum lipids mostly occur through its binding to intracellular Estrogen Receptor alpha (ERalpha) isoform, expressed in most of tissues. This gene (ESR1) exhibit many polymorphic sites (SNPs) located either on translated and non-translated regions that regulate ERalpha protein expression and function. This paper aimed to investigate the association of two intronic SNPs of ESR1 gene, namely c454-397T>C (PvuII) and c454-351A>G (XbaI) to alterations in serum levels of total cholesterol (T-chol), total lipid (TL), low density lipoprotein cholesterol (LDL), high density lipoprotein (HDL), and triglycerides (TG) in a cohort of post-menopausal women. In addition, we aimed to associate presence of these SNPs to development of BC along 5 years period. To do so, a group of healthy 499, highly miscigenated, post-menopausal Brazilian women, were carried using PCR-FRLP technique and further confirmed by automatic sequence analysis as well followed through 5 years for BC incidence. Measurements of serum lipid profile by standard commercial methods were carried individually whereas Dual Energy X-ray Absorciometry (DXA) measured Body Mass Indexes (BMI), Fat Mass (FM), Lean Body Mass (LBM), and Body Water Content (BWC). No effects of PvuII SNP on ESR1 gene were observed on patient´s serum T-chol, TL, LDL, HDL, and TG. However, c454-397T>C PvuII SNP is associated to lower body fat and higher levels of lean mass and body water and lower incidence of BC. On the other hand, statistically significant effect of XbaI c454-351A>G SNP on serum TG and TL levels. Patients homozygous for X allele were followed up from 2010-2015. They showed higher incidence of breast cancer (BC) when compared to either heterozygous and any P allele combination. Moreover, the increasing of TG and TL serum concentrations associated to SNP XbaI c454-351A>G on ESR1 gene is enhanced in both obese (higher BMI) and elder women. Taken together, these results suggested that XbaI c454-351A>G SNP is associated to changes in lipid profile, particularly in serum TG and TL, in this cohort of post-menopausal woman. Also, this paper shows another link between obesity and BC corroborating the current thesis that both diseases are interlinked.

Effect of lead on physiological and antioxidant responses in two Vigna unguiculata cultivars differing in Pb-accumulation.

Lead (Pb) is one of the most toxic anthropogenic pollutants, occurring widely in both terrestrial and aquatic ecosystems, where it impairs plant growth and development. In this work, the effect of 0.5 mM EDTA-Pb was evaluated in two Vigna unguiculata cultivars (SV and SET), with the aim of detecting genotype/cultivar dependent changes in the physiological and anti-oxidant responses (CAT and APX) of a leguminous plant. The data showed that SV accumulated more Pb in roots while SET accumulated more in leaves, indicating differential regulation in Pb-translocation/accumulation. Lead affected the growth of SV less severely than SET, mainly associated with reduced inhibition in photosynthetic parameters. Furthermore, CAT and APX activities increased or were sustained at elevated levels in both cultivars in response to lead. However, gene expression analyses revealed that CAT1 was the main lead responsive gene in SET while CAT2 was more responsive in SV. APX1 was higher expressed in tissues with higher Pb-accumulation while APX2 was ubiquitously responsive to lead in both cultivars. Taken together, these results reveal differential ability of V. unguiculata cultivars in Pb-accumulation in different tissues affecting distinctly physiological and anti-oxidant responses. In addition, the existence of cultivars with predominant Pb-accumulation in aerial tissues invokes a need for studies to identify pollution-safe cultivars of leguminous plants to ensure food safety.