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Heterocyclic aromatic amines: Microbial metabolism and interaction with fruit and vegetable dietary fiber

杂环芳香胺：微生物代谢及其与水果和蔬菜膳食纤维的相互作用

基本信息

批准号：
252157018
负责人：
Professor Dr. Mirko Bunzel
金额：
--
依托单位：
Institut für Sicherheit und Qualität bei Obst und Gemüse
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2014
资助国家：
德国
起止时间：
2013-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/252157018?language=en
关键词：
Heterocyclic aromatic amines Microbial metabolism

项目摘要

Heterocyclic aromatic amines (HAA) are mutagenic and potentially carcinogenic compounds, which can be found in thermally treated food products. After absorption in the small intestine, HAA are metabolically activated by a complex sequence of phase-I- and phase-II-enzyme reactions. Following N-hydroxylation of the exocyclic amino group, the N-hydroxy metabolites can be conjugated to form N-acetoxy- and N-sulfonyloxy esters. Heterolytic cleavage generates highly reactive aryl nitrenium ions, which can form DNA adducts. However, in the small intestine, HAA can be adsorbed to dietary fiber and bacteria, thus escaping absorption. Fiber/bacteria bound HAA reach the colon and are potentially metabolized by the gut microbiota, thus being activated or inactivated. However, to date, only two microbial HAA metabolites (PhIP-M1 und 7-OH-IQ) were identified both in vitro and in vivo. Preliminary data demonstrated that other HAA such as AalphaC can also be metabolized by the gut microbiota.The proposed project strives to identify unknown metabolites of AalphaC, MeIQx, MeIQ, Trp-P-1 and Harman/Norharman formed by human fecal microbiota in vitro. Structural elucidation of the metabolites is performed by LC-MS and NMR. Dominant metabolites are isolated on a semipreparative scale and tested for their mutagenic potential and absorption in the colon by using the Ames test and a Caco-2-model, respectively. In addition, the impact of the adsorption of HAA to lignified dietary fiber from fruits and vegetables on the formation of bacterial HAA metabolites is studied. Also, the adsorption of microbial HAA metabolites to partially fermented fiber will be analyzed. By using synthetically lignified model dietary fibers we previously demonstrated that HAA adsorption is dependent on both lignin concentration and composition. It was also shown that partial bacterial fermentation of the model dietary fibers led to a reduced fiber/HAA interaction. In this study we aim to isolate and structurally characterize lignified fruit and vegetable fibers with regard to the following characteristics: Carbohydrate contents and structures (HPAEC, GC-FID/MS), lignin contents and structures (DFRC-method, 2D-NMR). The isolated fibers are fermented in vitro with human fecal suspensions. Subsequently, the partially fermented fibers are used in binding studies with HAA metabolites. In addition, fiber-HAA-complexes are prepared by incubating HAA and dietary fibers under small intestine conditions. The formation of HAA-metabolites from these fiber-HAA-complexes is studied in fermentation experiments using fecal samples. The research proposed in this application is significant because the resulting data on the formation of microbial HAA metabolites and their interaction with dietary fiber from fruits and vegetables will contribute to a re-evaluation of an often suggested mechanism how dietary fiber can reduce the risk of various forms of cancer.

杂环芳香胺（HAA）是一种具有致突变性和潜在致癌性的化合物，可在热处理食品中发现。在小肠吸收后，HAA通过I相和II相酶反应的复杂序列代谢活化。环外氨基的N-羟基化后，N-羟基代谢物可结合形成N-乙酰氧基酯和N-磺酰氧基酯。异裂切割产生高反应性的芳基氮鎓离子，其可以形成DNA加合物。然而，在小肠中，HAA可以吸附到膳食纤维和细菌上，从而逃避吸收。纤维/细菌结合的HAA到达结肠并可能被肠道微生物群代谢，从而被激活或失活。然而，到目前为止，只有两个微生物HAA代谢产物（PhIP-M1和7-OH-IQ）在体外和体内都被确定。初步数据表明，其他HAA如AalphaC也可以被肠道微生物群代谢。拟议的项目致力于在体外鉴定由人类粪便微生物群形成的AalphaC，MeIQx，MeIQ，Trp-P-1和Harman/Norharman的未知代谢物。通过LC-MS和NMR对代谢产物进行结构解析。以半制备规模分离主要代谢物，并分别使用艾姆斯试验和Caco-2模型检测其致突变潜力和结肠吸收。此外，还研究了果蔬木质素膳食纤维吸附HAA对细菌HAA代谢产物形成的影响。此外，还将分析微生物HAA代谢产物对部分发酵纤维的吸附。通过使用合成木质素模型膳食纤维，我们先前证明了HAA吸附依赖于木质素浓度和组成。还表明，模型膳食纤维的部分细菌发酵导致减少的纤维/HAA相互作用。在这项研究中，我们的目的是分离和结构表征木质素水果和蔬菜纤维方面的以下特点：碳水化合物的含量和结构（HPAEC，GC-FID/MS），木质素含量和结构（DFRC方法，2D-NMR）。将分离的纤维与人粪便悬浮液一起在体外发酵。随后，将部分发酵的纤维用于与HAA代谢物的结合研究。此外，通过在小肠条件下孵育HAA和膳食纤维来制备纤维-HAA-复合物。在使用粪便样品的发酵实验中研究了从这些纤维-HAA-复合物形成HAA-代谢物。本申请中提出的研究具有重要意义，因为有关微生物HAA代谢物形成及其与水果和蔬菜膳食纤维相互作用的数据将有助于重新评估膳食纤维如何降低各种癌症风险的机制。