Divalent Metal-ion Transporter 1 as a Therapeutic Target to Optimize Intestinal Iron Transport

二价金属离子转运蛋白 1 作为优化肠道铁转运的治疗靶点

• 批准号: 9314563
• 负责人: James F. Collins
• 金额: $ 51.35万
• 依托单位: UNIVERSITY OF FLORIDA
• 依托单位国家: 美国
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-15 至 2021-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9314563
• 关键词: Adult; Anemia; Arthritis; Binding; Biochemical; Cardiomyopathies; Chronic; Complex; Copper; Data; Development; Diabetes Mellitus; Dietary Iron; Disease; Duodenum; Enterocytes; Epithelium; Erythropoiesis; Fatigue; Future; Gene Silencing; Genes; Ginger; Globin; Goals; Hemorrhage; Hereditary hemochromatosis; Homeostasis; Hormones; Human; Hypoxia; Immune response; Immunologic Techniques; Impaired cognition; Impairment; Impotence; Individual; Infant; Inflammation; Inherited; Intestines; Investigation; Ions; Iron; Iron Overload; Knockout Mice; Lipids; Maintenance; Malignant neoplasm of liver; Mediating; Mediator of activation protein; Modality; Modeling; Molecular; Morbidity - disease rate; Mus; Mutate; Mutation; Nutrient; Nutritional; Osteoporosis; Oxides; Pathologic; Patients; Physiological; Play; Post-Translational Protein Processing; Pregnancy; Process; Production; Property; Proteins; Rat Cell Line; Rattus; Regulation; Risk; Rodent Model; Role; Small Interfering RNA; Small Intestines; Structure; Symptoms; System; Technology; Testing; Thalassemia intermedia; Therapeutic; Tissues; Transferrin; absorption; bariatric surgery; base; basolateral membrane; beta Thalassemia; brush border membrane; clinically significant; divalent metal; falls; hepcidin; in vivo; insight; iron deficiency; liver injury; mRNA Expression; metal transporting protein 1; mortality; mouse model; nanoparticle; novel; novel therapeutics; nutritional approach; pre-clinical; prevent; prophylactic; protein function; rapid growth; therapeutic target; uptake; vector; young woman

Project Summary Iron is an essential nutrient for humans, yet excess iron is toxic. As such, iron overload and iron deficiency result in severe homeostatic perturbations. Iron overload is most frequently associated with hereditary hemochromatosis (HH), which afflicts ~1:250 adults in the U.S. Tissue iron accumulation in patients with HH leads to arthritis, osteoporosis, liver damage and cancer, cardiomyopathy, diabetes mellitus, and impotence. HH results from impaired production of the iron-regulatory hormone hepcidin (HEPC) or as a result of mutations in the HAMP gene (encoding HEPC). HEPC limits intestinal iron absorption. Moreover, reduced HEPC synthesis underlies the iron loading that typifies disorders of ineffective erythropoiesis (e.g. β- thalassemia intermedia [βTI]). In HH and βTI, intestinal iron absorption is thus excessive. This leads to pathological iron overload since humans cannot excrete excess iron. Regulation of intestinal iron absorption is thus critical to properly control body iron levels. Dietary iron exists primarily as inorganic (or nonheme) iron. Ferric (Fe3+) nonheme iron is first reduced to Fe2+, imported into duodenal enterocytes by divalent metal-ion transporter 1 (DMT1), exported by ferroportin 1 (FPN1) and oxidized for binding to transferrin. DMT1 is the primary intestinal iron importer under basal conditions, but the relative contribution of DMT1 to iron accumulation in HH and βTI is unknown. In Aim 1, we will thus test the hypothesis that DMT1 is required for iron loading in mouse models of HH (HEPC KO) and βTI (Hbbd3th; with a mutated β major globin [Hbb- b1]) gene. We will thus generate HEPC and Hbb-b1 KO mice that are also lacking intestinal DMT1. We further hypothesize that decreasing DMT1 expression will prevent iron loading in HH and βTI. Accordingly, we have developed ginger nanoparticle-derived lipid vectors (GNLVs) which can deliver functional DMT1 siRNA to the mouse duodenum in vivo (~40% reduction in DMT1 expression). In Aim 2, this GNLV delivery system will be tested for its ability to prevent iron loading in rodent models of HH and βTI. Furthermore, iron deficiency (ID) is also common in the U.S., afflicting ~8 million young women, and 700,000 infants. ID frequently occurs when absorption of dietary iron does not meet the body’s demand. ID most commonly occurs as a consequence of rapid growth, pregnancy, menstrual blood loss, malabsorptive disorders, gastric bypass surgery and chronic inflammation. ID symptoms include anemia, impaired cognition, decreased immune response, and fatigue. During ID, DMT1 increases Cu transport into duodenal enterocytes and emerging data demonstrates that copper is critical to support iron repletion during states of deficiency. The mechanism that transforms DMT1 into a copper transporter is, however, unknown. Aim 3 will thus test the hypothesis that the DMT1 protein is post-translationally modified during iron deficiency, allowing Cu transport. Plausible alternative hypotheses may also be considered. Overall, this DMT1-focused investigation is likely to potentiate the development of novel therapeutic and nutritional approaches to modulate intestinal iron absorption in at-risk individuals.

项目概要 铁是人体必需的营养素，但过量的铁是有毒的。因此，铁过量和铁缺乏 导致严重的体内平衡紊乱。铁超载最常与遗传有关 血色素沉着病 (HH)，影响约 1:250 的美国成年人 HH 患者的组织铁蓄积 导致关节炎、骨质疏松症、肝损伤和癌症、心肌病、糖尿病和阳痿。 HH 是由于铁调节激素铁调素 (HEPC) 的产生受损或由于 HAMP 基因（编码 HEPC）突变。 HEPC 限制肠道铁的吸收。此外，还减少了 HEPC 合成是铁负荷的基础，铁负荷是无效红细胞生成障碍（例如 β- 中间型地中海贫血[βTI]）。在 HH 和 βTI 中，肠道铁吸收过多。这导致 病理性铁超载，因为人类无法排出多余的铁。肠道铁吸收的调节是 因此，正确控制体内铁水平至关重要。膳食铁主要以无机（或非血红素）铁的形式存在。 三价铁 (Fe3+) 非血红素铁首先还原为 Fe2+，通过二价金属离子输入十二指肠肠细胞 转运蛋白 1 (DMT1)，由铁转运蛋白 1 (FPN1) 输出并被氧化以与转铁蛋白结合。 DMT1 是 基础条件下主要肠道铁输入者，但 DMT1 对铁的相对贡献 HH 和 βTI 中的积累情况未知。在目标 1 中，我们将检验需要 DMT1 的假设 用于 HH (HEPC KO) 和 βTI (Hbbd3th；具有突变 β 主要球蛋白 [Hbb- b1]) 基因。因此，我们将产生同样缺乏肠道 DMT1 的 HEPC 和 Hbb-b1 KO 小鼠。我们进一步 假设降低 DMT1 表达将阻止 HH 和 βTI 中的铁负荷。据此，我们有 开发了生姜纳米颗粒衍生的脂质载体 (GNLV)，该载体可以将功能性 DMT1 siRNA 传递至 小鼠十二指肠体内（DMT1 表达减少约 40%）。在目标 2 中，该 GNLV 传输系统将是 测试了其在 HH 和 βTI 啮齿动物模型中防止铁负荷的能力。此外，缺铁（ID）是 这种疾病在美国也很常见，约 800 万年轻女性和 70 万婴儿受其困扰。 ID 经常出现在以下情况 膳食铁的吸收不能满足人体的需要。 ID 最常发生的原因是 快速生长、怀孕、月经失血、吸收不良、胃绕道手术和慢性 炎。 ID 症状包括贫血、认知受损、免疫反应下降和疲劳。 ID 期间，DMT1 增加铜转运至十二指肠肠细胞，新出现的数据表明 铜对于缺铁状态下补充铁至关重要。转化DMT1的机制 然而，进入铜转运蛋白的情况尚不清楚。因此，目标 3 将检验以下假设：DMT1 蛋白是 缺铁期间发生翻译后修饰，允许铜转运。合理的替代假设 也可以考虑。总体而言，这项以 DMT1 为重点的研究可能会促进 调节高危人群肠道铁吸收的新治疗和营养方法。