基于代谢组学探索动物性腌制食品N-亚硝基化合物（NOC）的安全性问题

N- nitroso compounds(NOC) are extremely harmful to human health. Human intake of NOC mixtures which including a variety of complex precursors and metabolism regulator through food intake and endogenous synthesis. Foreign scholars and domestic scientists paid more attention to the carcinogenic effect and mechanism of NOC. The pollution situation of NOC and its precursor, especially in many animal pickled products is unclear. Metabolic transformation of NOC and its precursor after entering the body is unclear too. Research on how to minimize the harm of N-nitroso compounds to human health has important practical significance and theoretical value. At present, using the dietary ingredient or nutrition means to limit the levels of NOC in food, finding NOC metabolic markers for effective food restriction of NOC has become one of the most important early preventive measures to control NOC pollution. There are many types of NOC. Single NOC detection is hard to reflect the exposure level of total NOC. The concept of metabolism group provides a new idea and method of an overall research on the toxicity of NOC and its precursors. In the study of this topic, through the determination total N- nitroso compounds (TNOC) of the commercially available common animal pickles food, we master NOC contamination in food. We study on the generating ways of NOC in animal food by metabonomics methods. The whole research mode can fully understand the changes of NOC and its precursor in the body and in the occurrence and development of disease. It is of great significance to explore the measures and methods of hazard control NOC on health. In this study, we establish animal liver injury rat model induced by pickled food and NDMA. Using liquid chromatography-mass spectrometry analysis technique (LC-MS), we study on changes of metabolic components in plasma and liver tissue of animal model. We also use the animal model to observe the protective effect of antioxidants in the diet. Through the screening of metabolites, comparison of plasma metabolomics data of gastric carcinoma, esophageal cancer and hepatocellular carcinoma patients, we finally find the potential related metabolic biomarkers. This study is of great significance for the early prevention of NOC pollution and toxic effects.

N-亚硝基类化合物(NOC)对人类健康危害性极大，目前，国内外研究较多的是其“三致”作用，尤其是致癌作用及机理。有关NOC污染现状尤其是动物性腌制品中NOC及其前体物污染情况、NOC进入机体后的代谢转化等研究不多。目前，利用膳食成分或营养方式限制食品中NOC水平、寻找有效的NOC代谢标识物，已成为早期预防控制食品中NOC污染所致健康危害的最重要措施之一。本课题通过测定市售常见动物性腌制品中TNOC，掌握相关食品的NOC污染情况；利用动物模型结合代谢组学方法，研究动物性腌制品进入机体后NOC生成途径及其影响因素，观察膳食中抗氧化成分联合作用对腌肉制品在体内NOC的生成及其毒作用的影响，寻找潜在有效的NOC代谢标识物并找出评价人体接触NOC的具有关键意义的指标；并将潜在血浆代谢产物分子标志物在肝癌、食管癌及胃癌病人血浆中进行验证及筛选，对早期预防和控制NOC污染所致的毒性作用具有重要意义。

背景：2015年国际癌症研究机构（IARC）将加工肉制品列为致癌物（1类），其潜在致癌性与腌制、烟熏等加工过程中产生的污染物相关。腌肉制品中的N-亚硝基化合物（N-nitroso compounds，NOC）毒性问题引起重点关注。我国居民有腌肉食用习惯，但目前腌肉制品中NOC及其前体物污染现状报道不多，NOC进入机体后的健康危害及代谢转化途径尚不清楚。主要内容：本课题测定了市售常见动物性腌制品（腊肠、咸鱼）中9种VNAs及其前体物；利用动物模型研究不同数量、不同二甲基亚硝胺（NDMA）污染程度腊肠长期摄入对大鼠消化系统尤其是肝脏影响，利用阳性对照（NDMA）组大鼠肝脏损害模型，探索NOC对肝脏的损害及其机制；基于代谢组学研究腊肠长期摄入对大鼠血清代谢组学影响以及补充抗坏血酸对大鼠肝脏损害的保护作用及其机制，分析NOC污染肉制品的长期摄入导致肝脏损害的潜在代谢生物标志物，并解析NOC代谢途径、寻找NOC代谢标识物。结果：建立了基于QuEChERS结合GC-MS/MS分析方法，检测市售腊肠、咸鱼中NOC，发现NDMA和总挥发性亚硝胺及其前体物污染情况不容忽视，我国应建立总挥发性亚硝胺食品安全标准并加以监测。成功建立了经口摄入NDMA诱导大鼠肝癌模型；长期摄入NDMA污染腊肠影响大鼠血清生化、抗氧化指标并导致大鼠肝脏损害，损害程度与腊肠摄入量、NDMA含量及摄入时间有关，NDMA超标腊肠的长期摄入会导致大鼠发生肝炎、肝纤维化、肝硬化风险增加。血清代谢组学研究发现，长期腊肠摄入可引起大鼠血清代谢产物显著变化，在3个剂量的腊肠组大鼠血清出现了7个代谢物4个时间点均显著降低，以及3个代谢物显著增加。这些差异代谢物主要与血脂、氨基酸和能量代谢紊乱有关，肝脏病理学检测结果与血清代谢组学结果一致，提示可能与肝脏损害有关。补充抗坏血酸有助于长期NDMA超标腊肠摄入大鼠的肝脏保护、改善体内抗氧化水平和部分血清生化指标，病理检查发现抗坏血酸对NDMA超标腊肠的长期摄入保护作用微弱，提示抗氧化因素对腌肉制品中NOC健康危害的保护作用有限，食品中NOC污染监控十分重要。