RESUMO
Insulin secretion from pancreatic beta-cells is dependent on zinc ions as essential components of insulin crystals, zinc transporters are thus involved in the insulin secretory process. Zip14 (SLC39a14) is a zinc importing protein that has an important role in glucose homeostasis. Zip14 knockout mice display hyperinsulinemia and impaired insulin secretion in high glucose conditions. Endocrine roles for Zip14 have been established in adipocytes and hepatocytes, but not yet confirmed in beta-cells. In this study, we investigated the role of Zip14 in the INS-1E beta-cell line. Zip14 mRNA was upregulated during high glucose stimulation and Zip14 silencing led to increased intracellular insulin content. Large-scale proteomics showed that Zip14 silencing down-regulated ribosomal mitochondrial proteins, many metal-binding proteins, and others involved in oxidative phosphorylation and insulin secretion. Furthermore, proliferation marker Mki67 was down-regulated in Zip14 siRNA-treated cells. In conclusion, Zip14 gene expression is glucose sensitive and silencing of Zip14 directly affects insulin processing in INS-1E beta-cells. A link between Zip14 and ribosomal mitochondrial proteins suggests altered mitochondrial RNA translation, which could disturb mitochondrial function and thereby insulin secretion. This highlights a role for Zip14 in beta-cell functioning and suggests Zip14 as a future pharmacological target in the treatment of beta-cell dysfunction.
Assuntos
Proteínas de Transporte de Cátions/metabolismo , Regulação da Expressão Gênica , Secreção de Insulina/genética , Células Secretoras de Insulina/metabolismo , Proteômica , Animais , Apoptose/efeitos dos fármacos , Apoptose/genética , Proteínas de Transporte de Cátions/genética , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/genética , Regulação para Baixo/efeitos dos fármacos , Regulação para Baixo/genética , Regulação da Expressão Gênica/efeitos dos fármacos , Inativação Gênica , Glucose/farmacologia , Insulina/genética , Insulina/metabolismo , Secreção de Insulina/efeitos dos fármacos , Metalotioneína/genética , Metalotioneína/metabolismo , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , RNA Interferente Pequeno/metabolismo , Ratos , Reprodutibilidade dos Testes , Regulação para Cima/efeitos dos fármacos , Regulação para Cima/genética , Transportador 8 de Zinco/genética , Transportador 8 de Zinco/metabolismoRESUMO
BACKGROUND: Magnetic Resonance Imaging (MRI) is often used in modern day radiotherapy (RT) due to superior soft tissue contrast. However, treatment planning based solely on MRI is restricted due to e.g. the limitations of conducting online patient setup verification using MRI as reference. In this study 3D/3D MRI-Cone Beam CT (CBCT) automatching for online patient setup verification was investigated. MATERIAL AND METHODS: Initially, a multi-modality phantom was constructed and used for a quantitative comparison of CT-CBCT and MRI-CBCT automatching. Following the phantom experiment three patients undergoing postoperative radiotherapy for malignant brain tumors received a weekly CBCT. In total 18 scans was matched with both CT and MRI as reference. The CBCT scans were acquired using a Clinac iX 2300 linear accelerator (Varian Medical Systems) with an On-Board Imager (OBI). RESULTS: For the phantom experiment CT-CBCT and MRI-CBCT automatching resulted in similar results. A significant difference was observed only in the longitudinal direction where MRI-CBCT resulted in the best match (mean and standard deviations of 1.85±2.68 mm for CT and -0.05±2.55 mm for MRI). For the clinical experiment the absolute difference in couch shift coordinates acquired from MRI-CBCT and CT-CBCT automatching, were ≤2 mm in the vertical direction and ≤3 mm in the longitudinal and lateral directions. For yaw rotation differences up to 3.3 degrees were observed. Mean values and standard deviations were 0.8±0.6 mm, 1.5±1.2 mm and 1.2±1.2 mm for the vertical, longitudinal and lateral directions, respectively and 1.95±1.12 degrees for the rotation (n=17). CONCLUSION: It is feasible to use MRI as reference when conducting 3D/3D CBCT automatching for online patient setup verification. For both the phantom and clinical experiment MRI-CBCT performed similar to CT-CBCT automatching and significantly better in the longitudinal direction for the phantom experiment.