7,051 research outputs found

    SLC30A3 Responds to Glucose- and Zinc Variations in ß-Cells and Is Critical for Insulin Production and In Vivo Glucose-Metabolism During ß-Cell Stress

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    BACKGROUND:Ion transporters of the Slc30A- (ZnT-) family regulate zinc fluxes into sub-cellular compartments. beta-cells depend on zinc for both insulin crystallization and regulation of cell mass. METHODOLOGY/PRINCIPAL FINDINGS:This study examined: the effect of glucose and zinc chelation on ZnT gene and protein levels and apoptosis in beta-cells and pancreatic islets, the effects of ZnT-3 knock-down on insulin secretion in a beta-cell line and ZnT-3 knock-out on glucose metabolism in mice during streptozotocin-induced beta-cell stress. In INS-1E cells 2 mM glucose down-regulated ZnT-3 and up-regulated ZnT-5 expression relative to 5 mM. 16 mM glucose increased ZnT-3 and decreased ZnT-8 expression. Zinc chelation by DEDTC lowered INS-1E insulin content and insulin expression. Furthermore, zinc depletion increased ZnT-3- and decreased ZnT-8 gene expression whereas the amount of ZnT-3 protein in the cells was decreased. Zinc depletion and high glucose induced apoptosis and necrosis in INS-1E cells. The most responsive zinc transporter, ZnT-3, was investigated further; by immunohistochemistry and western blotting ZnT-3 was demonstrated in INS-1E cells. 44% knock-down of ZnT-3 by siRNA transfection in INS-1E cells decreased insulin expression and secretion. Streptozotocin-treated mice had higher glucose levels after ZnT-3 knock-out, particularly in overt diabetic animals. CONCLUSION/SIGNIFICANCE:Zinc transporting proteins in beta-cells respond to variations in glucose and zinc levels. ZnT-3, which is pivotal in the development of cellular changes as also seen in type 2 diabetes (e.g. amyloidosis in Alzheimer's disease) but not previously described in beta-cells, is present in this cell type, up-regulated by glucose in a concentration dependent manner and up-regulated by zinc depletion which by contrast decreased ZnT-3 protein levels. Knock-down of the ZnT-3 gene lowers insulin secretion in vitro and affects in vivo glucose metabolism after streptozotocin treatment


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    Alzheimer’s disease (AD), one of the major causes of disability and mortality in Western societies, is a progressive age-related neurodegenerative disorder. Increasing evidence suggests the etiology of AD may involve disruptions of zinc (Zn) homeostasis. We hypothesize that disruption of Zn homeostasis leads to alterations of Zn transporter (ZnT) proteins, resulting in increased production of neurotoxic amyloid beta (Aβ) peptide in AD brain. To address this hypothesis we carried out the following studies. 1. We characterized alterations of ZnT-1, ZnT-4 and ZnT-6 in the brain of preclinical AD (PCAD) subjects, who show no overt clinical manifestations of AD but demonstrate significant AD pathology at autopsy. 2. We identified the presence of ZnT-2 in human brain and compared protein levels in the brains of subjects with PCAD, mild cognitive impairment (MCI), early (EAD), and late-stage AD (LAD) to those in age matched normal control (NC) subjects. 3. We examined the relationship between protein levels of ZnT-1, ZnT-2, ZnT-4, ZnT-6 and Aβ produced by H4 human neuroglioma cells (H4-APP) transfected to overexpress amyloid precursor protein (APP), treated with short interfering RNA (siRNA) against each ZnT. Our data show a significant decrease (P \u3c 0.05) of ZnT-1 and a significant increase of ZnT-6 in hippocampus/parahippo-campal gyrus (HPG) of PCAD subjects. In PCAD cerebellum (CER) the data show a significant increase of ZnT-4 and ZnT-6 compared to NC subjects. Levels of ZnT-2 were also significantly decreased in HPG of PCAD subjects compared to NC subjects. In addition, levels of ZnT-2 were significantly (P \u3c 0.05) elevated in SMTG of PCAD and MCI subjects, compared to NC subjects. ZnT-2 was significantly (P \u3c 0.05) elevated in HPG of EAD and LAD, and in SMTG of LAD brains, but was significantly (P \u3c 0.05) decreased in LAD CER compared to NC subjects. siRNA mediated attenuation of each ZnT protein studied (ZnT-2, ZnT-4 and ZnT-6) led to significantly (P \u3c 0.05) decreased production of Aβ compared to controls. Our results suggest alterations in Zn transport may play a role in Aβ processing and contribute to the neuropathology of AD

    Localization of zinc transporter-3 (ZnT-3) in mouse retina

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    AbstractStudies of the central nervous system have localized the zinc-transporter-3 (ZnT-3) protein to synaptic vesicles containing glutamate and zinc. We have examined the distribution of the ZnT-3 protein in the light-adapted mouse retina using immunohistochemical techniques. Light microscopic analysis of 15–30-μm retinal sections revealed a rich band of ZnT-3 protein in the region of the outer limiting membrane and photoreceptor inner segments. ZnT-3 reactivity was also present in the outer plexiform, inner nuclear, inner plexiform, and ganglion cell layers. The outer nuclear layer and photoreceptor outer segments did not exhibit ZnT-3 immunoreactivity. In the light-adapted murine retina, ZnT-3 appears localized in regions which have been found reactive for ionic zinc

    ZnT‐1 expression in the preimplantation mouse embryo and its effect on calcium influx

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    ZnT-1 expression in the pre-implantation mouse embryo and its effect on calcium influx Pre-implantation embryos develop into 9 stages over the first 5 days post-fertilisation. Calcium influx from the external environment via calcium channels, including the L-type and T-type calcium channels, is critical for embryonic gene activation and cell proliferation. In cardiomyocytes these channels are regulated by the ubiquitously expressed zinc-transporter protein ZnT-1. When plasma membrane bound, ZnT-1 facilitates zinc-efflux. Free cellular zinc regulates ZnT-1 expression, with an increase in zinc inducing transcription. In this study, ZnT-1 mRNA and protein expression were investigated in pre-implantation embryo stages using qPCR and immunofluorescence. Embryos were cultured in vitro in zinc-supplemented media and compared to embryos cultured in the absence of zinc and to in vivo developed embryos. ZnT-1 mRNA was expressed at all stages and the presence of zinc increased mRNA expression a the late 2-cell stage only. There was no difference in expression between in vivo developed and cultured embryos. ZnT-1 protein was expressed from the early 2-cell stage onwards; not affected by zinc culture and localized to the plasma membrane at the late 2-cell stage only. Calcium imaging was performed to examine whether ZnT-1 membrane localization altered calcium influx. Experiments on early and late 2-cell embryos showed that there was no difference in calcium influx when ZnT-1 was localized to the plasma membrane. In summary ZnT-1 transcription was induced by zinc at the late 2-cell stage. Protein expression was not affected by zinc culture but was developmentally regulated, localizing to the plasma-membrane at the late 2-cell stage without effect on calcium influx

    Variables Affecting ZNT Implementation in Communities Semarang City

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    The Land and Building Tax Imposition Base (NJOP) is used to determine the basis for Land and Building Taxes. But in reality, NJOP sometimes does not match fair market values. By land valuation experts, a method was formed which approached real land prices, namely the Land Value Zone (ZNT). ZNT in its application and development raises diverse responses. For that, we need to study variables affecting the implementation of ZNT in the community. Therefore, the city of Semarang is considered suitable for case studies on the implementation of ZNT because it is the center of economic activity in Central Java Province. This research is expected to provide benefits regarding the implementation of ZNT as a method to determine the amount of NJOP. The level of acceptance of ZNT implementation in society is measured by 10 variables. The data in this study were obtained using a questionnaire sampling to community. Questionnaire results are then analyzed so as to help further explain statistical results that have been obtained. Facts on the ground show that the people of Semarang City feel the ease and accuracy as well as the fair transparency of market prices for land in ZNT. The analysis results that have been found, there are 3 variables that most influence, namely politics, communication with the parties concerned, and socialization of ZNT. Those improvements are needed on the internal and external factors of the ZNT method and coordination, communication and cooperation between the government and the community


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    Pertumbuhan jumlah penduduk mendorong kenaikan permintaan pada tanah yang berakibat pada penawaran harga tanah yang semakin tinggi dari tahun ke tahun. Pembuatan Zona Nilai Tanah (ZNT) dalam Keputusan Direktur Jenderal Pajak Nomor Kep- 16/PJ.6/1998 terdiri dari enam tahapan, yakni tahap persiapan, pengumpulan data harga jual, kompilasi data, rekapitulasi data dan memplot data transaksi pada peta kerja ZNT, analisis data, dan pembuatan peta ZNT akhir. Pembuatan ZNT kecenderungan dengan melakukan pendekatan individu (survei lapangan) dan mengintegrasikan setiap variabel dalam penentuan nilai tanah sehingga membutuhkan waktu dan tahapan yang cukup lama. Oleh karena itu, diperlukan suatu metode lain untuk membuat peta ZNT untuk mempersingkat proses pembuatan peta ZNT. Salah satu alternatif untuk mebuat peta ZNT adalah dengan melakukan proses interpolasi data harga tanah. Pada penelitian ini dikaji kelayakan metode interpolasi Inverse Distance Weighted (IDW) untuk pembuatan peta ZNT. Metode ini dipengaruhi oleh inverse jarak yang diperoleh dari persamaan matematika dan kita dapat menyesuaikan pengaruh relatif dari titik – titik sampel. Pembuatan ZNT dibuat dengan memanfaatkan data survei lapangan terhadap harga penawaran dengan 31 sampel harga tanah. Pembentukan ZNT yang bertujuan untuk mengelompokkan bidang-bidang tanah sesuai dengan Nilai Indikasi Rata-rata (NIR). Data yang digunakan adalah sampel data harga tanah di Kelurahan Gedong Meneng, Kota Bandarlampung. Berdasarkan perhitungan standar deviasi dan nilai Mean Square Error, yang memiliki ketelitian data yang paling baik dan semakin mirip data hasil prediksi dari suatu pemodelan dengan data sebenarnya adalah hasil interpolasi IDW dengan power 5, input 12, dan radius 2000 meter. Dengan demikian, metode interpolasi IDW layak digunakan untuk pembuatan peta ZNT.Kata kunci : IDW, Nilai Tanah, SIG, ZN

    In vivo expression and functional characterization of the zinc transporter ZnT8 in glucose-induced insulin secretion.

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    International audienceInsulin-secreting pancreatic beta cells are exceptionally rich in zinc. In these cells, zinc is required for zinc-insulin crystallization within secretory vesicles. Secreted zinc has also been proposed to be a paracrine and autocrine modulator of glucagon and insulin secretion in pancreatic alpha and beta cells, respectively. However, little is known about the molecular mechanisms underlying zinc accumulation in insulin-containing vesicles. We previously identified a pancreas-specific zinc transporter, ZnT-8, which colocalized with insulin in cultured beta cells. In this paper we studied its localization in human pancreatic islet cells, and its effect on cellular zinc content and insulin secretion. In human pancreatic islet cells, ZnT-8 was exclusively expressed in insulin-producing beta cells, and colocalized with insulin in these cells. ZnT-8 overexpression stimulated zinc accumulation and increased total intracellular zinc in insulin-secreting INS-1E cells. Furthermore, ZnT-8-overexpressing cells display enhanced glucose-stimulated insulin secretion compared with control cells, only for a high glucose challenge, i.e. >10 mM glucose. Altogether, these data strongly suggest that the zinc transporter ZnT-8 is a key protein for both zinc accumulation and regulation of insulin secretion in pancreatic beta cells

    Rhetoric in legislative bargaining with asymmetric information

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    We analyze a three-player legislative bargaining game over an ideological and a distributive decision. Legislators are privately informed about their ideological intensities, i.e., the weight placed on the ideological decision relative to the weight placed on the distributive decision. Communication takes place before a proposal is offered and majority rule voting determines the outcome. We show that it is not possible for all legislators to communicate informatively. In particular, the legislator who is ideologically more distant from the proposer cannot communicate informatively, but the closer legislator may communicate whether he would \compromise "or flight" on ideology. Surprisingly, the proposer may be worse off when bargaining with two legislators (under majority rule) than with one (who has veto power), because competition between the legislators may result in less information conveyed in equilibrium. Despite separable preferences, the proposer is always better off making proposals for the two dimensions together