Molecular characterization of trace element uptake in the gastrointestinal tract

必需微量元素（TE）如硒（Se）、锰（Mn）、锌（Zn）、铁（Fe）、碘(I)和铜（Cu）是各种生理活动不可或缺的元素，参与酶促反应、蛋白质结构稳定以及内分泌和细胞内信号传导。TE缺乏和超生理暴露与多种生理、形态和功能变化有关，这些变化与许多不同疾病的发病率和严重程度有关。因此，充足的TE供应是预防医学的基石，监测和潜在地纠正老年人TE失衡有助于健康老龄化。这些进程中的两个基本方面将是本建议的主题。首先，尽管有明确的迹象表明对肠吸收有重要影响，但到目前为止，不同TE在肠吸收过程中可能相互作用的分子事件，特别是它们与黏液层的化学相互作用的竞争，一直被广泛忽视。因此，工作包1研究了TE单独与粘蛋白的结合，以及它们在与Traceage动物日粮相当的浓度下的相互依赖性。在工作包2中，TE与黏液层糖蛋白之间的相互作用对TE摄取的影响将在小肠体外模型中得到阐明。因此，炎症也将被考虑在内，因为炎症是衰老过程中病理变化的中心因素，胃肠道屏障完整性、TE摄取和缺乏与炎症之间存在着相互交织的关系。其次，目前用于Cu和Zn状态的生物标志物存在相当大的局限性，特别是当涉及到解决TE供应充足和略微不足之间的细微界限时。我们将重点测量血清中游离离子的浓度，因为它们代表了这些TE的生物可利用部分。因此，在工作包3中，我们将开发一种使用低分子量荧光探针测定血清样品中游离铜的程序。与Traceage第一期资助阶段成功建立的用Zinpyr-1测定游离锌的方法一起，我们将使用它来测定人类队列EPIC-DZD （P1, Schulze）和WONDER （P2, Norman）以及Traceage第二期资助阶段动物实验中获得的血清中Zn和Cu的生物可利用组分的浓度（P3, Kipp; P6, Grune）。总之，本项目的结果将有助于更好地了解TE摄取过程中的复杂相互作用，从而改善饮食，以获得足够的TE供应。

Essential trace elements (TE) such as selenium (Se), manganese (Mn), zinc (Zn), iron (Fe), iodine (I) and copper (Cu) are indispensable for various physiological events, being involved in enzymatic reactions, structural stabilization of proteins, and endocrine and intracellular signaling. TE deficiencies as well as supraphysiological exposures are associated with a multitude of physiological, morphological, and functional changes that are contributing to the incidence and severity of many different diseases. Therefore, adequate TE supply is a cornerstone of preventive medicine, and monitoring and potentially correcting TE imbalances in the elderly can contribute to healthy ageing. Two fundamental aspects in these processes will be subject of this proposal. Firstly, despite clear indication for a crucial impact on intestinal resorption, molecular events by which different TE might interact during intestinal uptake, and in particular their competition for chemical interaction with the mucus layer, have been widely disregarded, so far. Consequently, work package 1 investigates the binding of TE with mucins alone, as well as their interdependence when being present in concentrations comparable to the Traceage animal diet. In work package 2 the impact of interactions between TE and the glycoproteins of the mucus layer on TE uptake will be elucidated in an in vitro model for the small intestine. Hereby, inflammation will also be considered, as inflammation is a central element of the pathological changes during aging, and there is an intertwined relationship between gastrointestinal barrier integrity, TE uptake and deficiency, and inflammation.Secondly, there are considerable limitations for the presently used biomarkers for the status of Cu and Zn, especially when it comes to addressing the fine line between adequate and marginally deficient supply with TE. We will focus on measuring the concentration of the free ions in serum, because they represent the biologically available fraction of these TE. Therefore, in work package 3 we will develop a procedure for determining free Cu in serum samples by using low molecular weight fluorescent probes. Together with the method for determining free zinc with Zinpyr-1, which has been successfully established in the first funding phase of Traceage, we will use it to determine the concentrations of the bioavailable fractions of Zn and Cu in sera from the human cohorts EPIC-DZD (P1, Schulze) and WONDER (P2, Norman) as well as sera obtained during the animal experiments from the second funding phase of Traceage (P3, Kipp; P6, Grune).Together, the results from this project shall contribute to a better understanding of the complex interactions during TE uptake, enabling dietary improvements towards adequate TE supply.