Physiology/Pathophysiology of Vitamin B1 Transport in Pancreatic Acinar Cells

维生素B1(硫胺素)对胰腺细胞的正常功能/健康是不可或缺的，因为它在 氧化能量代谢、三磷酸腺苷的产生，以及维持细胞的正常氧化还原状态。低 细胞内硫胺素水平导致急性能量衰竭、氧化应激和线粒体损伤 功能。在器官水平上，新陈代谢活跃的胰腺维持高水平的硫胺素，并缺乏 维生素的缺乏会削弱它的功能。胰腺不能内源性合成硫胺素，而是获得硫胺素。 从流通领域。这一研究计划的总体目标从一开始就集中在开发 全面了解胰腺腺泡摄取硫胺素的分子机制 细胞(PAC)及其主要细胞内形式，即硫胺素的随后运输(区域化) 焦磷酸(TPP)进入线粒体，这些过程是如何调节的，以及它们是如何受到 暴露在已知会对人的正常生理/健康产生不利影响的外部/内部因素中 胰腺。我们已经解决了其中许多问题，并在目前的提案中旨在确定：i)作用 MicroRNAs在THTR-1、THTR-2和线粒体TPP转运蛋白转录后调控中的作用 (MTPPT)在PACS中的表达及其介导的摄取过程；ii)Thtr-1和Thtr-2是否 的PAC具有影响/调节其生理/细胞生物学的相互作用的伙伴；以及iii) PAC在某些病理生理条件下暴露的特定因素[促炎 细胞因子、细菌脂多糖和鞭毛对硫胺素摄取和TPP转运的影响 进入它们的线粒体。因此，在新的初步研究中，有证据表明microRNAs 调节PAC的THTR-1表达和硫胺素摄取，THTR-1具有相互作用的伙伴(S)，并且 PAC暴露于促炎细胞因子(特别是与IL-2等胰腺疾病有关的细胞因子) 6，肿瘤坏死因子-α和IL-1β)，以及脂多糖和鞭毛蛋白，抑制细胞对硫胺素的摄取和转移 线粒体。基于这些新的发现，我们的工作假设是：i)microRNAs发挥重要作用 在转录后调控PAC中Thtr-1、Thtr-2和MTPPT的表达及其摄取事件 它们起调节作用；ii)PAC THTR-1和THTR-2有相互作用的伙伴，影响/调节它们的生理/细胞 生物学；以及iii)促炎细胞因子、内毒素和鞭毛蛋白对PACs硫胺素运输产生负面影响 生理学。我们计划通过实现两个特定目标来测试这些假设，并将利用 ART细胞/分子方法、人类和小鼠PAC以及适当的转基因小鼠模型。结果 这些研究应该提供有关维生素B1细胞/分子转运的新信息 PAC的生理学以及内部/外部因素如何影响所涉及的运输事件。这样的知识 可能最终有助于设计有效的策略来优化胰腺硫胺素稳态，以及 因此，改善胰腺的健康状况。

Vitamin B1 (thiamin) is indispensable for normal function/health of pancreatic cells due its critical roles in oxidative energy metabolism, ATP production, and in maintaining normal cellular redox state. Low intracellular level of thiamin leads to acute energy failure, oxidative stress, and impairment in mitochondrial function. At the organ level, the metabolically active pancreas maintains high levels of thiamin, and deficiency of the vitamin impairs its functions. The pancreas cannot synthesis thiamin endogenously; rather it obtains it from circulation. The overall goal of this research program since its inception has been focused on developing a comprehensive understanding of the molecular mechanisms involved in thiamin uptake by pancreatic acinar cells (PACs) and the subsequent transport (compartmentalization) of its major intracellular form, i. e., thiamin pyrophosphate (TPP), into mitochondria, how these processes are regulated, and how they are affected by exposure to external/internal factors that are known to adversely affect the normal physiology/health of the pancreas. We have addressed many of these issues, and in the current proposal aim at determining: i) the role of microRNAs in post-transcriptional regulation of THTR-1, THTR-2, and the mitochondrial TPP transporter (MTPPT) expression in PACS, and the uptake processes that they mediate; ii) whether THTR- 1 and THTR-2 of PACs have interacting partners that affect/regulate their physiology/cell biology; and iii) the effect of specific factors that PACs are exposed to under certain pathophysiological conditions [pro-inflammatory cytokines, and the bacterial lipopolysaccharide (LPS) and flagellin] on thiamin uptake and on transport of TPP into their mitochondria. Thus, in new preliminary studies evidence were obtained to suggest that microRNAs regulate THTR-1 expression and thiamin uptake by PACs, that THTR-1 has interacting partner(s), and that exposure of PACs to pro-inflammatory cytokines (especially those implicated in pancreatic disorders like IL- 6, TNF-α and IL-1β), as well as to LPS and flagellin, inhibit cellular thiamin uptake and transport of TPP into mitochondria. Based on these new findings, our working hypotheses are: i) microRNAs play an important role in post-transcriptional regulation of THTR-1, THTR-2, and MTPPT expression in PACs and the uptake events they mediate; ii) PACs THTR-1 and THTR-2 have interacting partners that affect/regulate their physiology/cell biology; and iii) pro- inflammatory cytokines, LPS and flagellin negatively impact PACs thiamin transport physiology. We plan to test these hypotheses by accomplishing two specific aims and will utilize state-of the art cellular/molecular approaches, human and mouse PACs, and appropriate transgenic mouse models. Results of these investigations should provide novel information regarding vitamin B1 cellular/molecular transport physiology in PACs and how internal/external factors affect the involved transport events. Such knowledge may ultimately assist in the designing of effective strategies to optimize pancreatic thiamin homeostasis, and thus, improve the health of the pancreas.