Intestinal Microbiota, Diet and Risk of Colorectal Adenomas

描述(申请人提供)：来自动物和人类研究的证据表明，肠道细菌可能导致结直肠癌(CRC)的发病，结直肠癌是美国癌症死亡的主要原因。肠道微生物区系和结直肠癌之间的潜在联系机制是通过饮食和炎症。我们提出了一个模型，即肠道细菌通过饮食、炎症和外源物质的代谢在结直肠癌的病因学中发挥重要作用。我们建议检验这一假设，即粘附性细菌(粘附性)与结直肠腺瘤的风险增加有关，并且这些细菌调节饮食、炎症和结直肠腺瘤之间的关联。我们认为，不同的共生定植模式或特定细菌种类的存在/不存在将与腺瘤风险相关。其具体目的是：1)确定腺瘤患者和非腺瘤患者之间粘附性(粘膜相关)细菌群落组成和结构(特征)是否不同；2)评价粘附性细菌特征与全身或局部炎症标志物(IL-12、IL-23、IL-4、IL-17、INF、IL-8、IL-10和TGF-(；巨噬细胞、NK细胞、T细胞-CD4+和CD8+；在患有和不患有腺瘤的受试者中，3)评估附着菌谱与饮食/生活方式之间的关系，例如纤维、肉类摄入量、肥胖(体重指数(BMI)、腰臀比)和非类固醇抗炎药使用与结直肠癌的关系。肠道细菌与人类疾病相关的多样性的评估在一定程度上受到在培养中生长这些细菌的困难的限制。分子方法的最新进展使评估肠道微生物区系在结肠癌等疾病中的作用成为可能。为了验证我们的假设，我们建议使用基于高度保守的16S细菌rRNA基因的分子系统学方法来评估肠道微生物区系对结直肠腺瘤发展的贡献。这些方法包括16S rRNA基因的PCR扩增、末端限制性片段长度多态性(TRFLP)、细菌克隆文库的构建和测序。这项研究将使用从600名患者(300名患者和300名对照)获得的结肠活检样本，以及来自一项由基金资助的正在进行的结直肠腺瘤研究-饮食与健康研究(NCI R01 CA 44684)的风险因素数据。目前关于肠道细菌在腺瘤发展中的作用的信息有限。这项研究将对微生物区系的组成和多样性以及它们与结直肠腺瘤的关系和已知的危险因素提供重要的见解。这项研究的发现可能会导致开发出操纵肠道微生物区系的策略，以预防结直肠腺瘤和癌症，以及识别高危个体。

DESCRIPTION (provided by applicant): Evidence from animal and human studies suggests that intestinal bacteria may contribute to the pathogenesis of colorectal cancer (CRC), a major leading cause of cancer mortality in the United States. Potential mechanisms for the link between gut microbiota and CRC is through diet and inflammation. We propose a model whereby intestinal bacteria play a prominent role in the etiology of CRC through diet, inflammation and metabolism of xenobiotics. We propose to test the hypothesis that adherent bacteria (adherent) are linked with elevated risk of colorectal adenoma and that these bacteria modulate the association between diet, inflammation and colorectal adenomas. We propose that distinct patterns of commensal colonization or presence/absence of specific bacteria species will correlate with adenoma risk. The specific aims are to 1) determine whether the adherent (mucosa-associated) bacteria community composition and structure (profiles) differ between subjects with adenomas and those without adenomas, 2) evaluate the associations of adherent bacteria profiles and systemic or local markers of inflammation (IL-12, IL-23, IL-4, IL-17, INF(, IL-8, IL-10 and TGF-(; macrophages, NK cells, T cells- CD4+ and CD8+; protein expression of NF-(B (p65) and STAT3) among subjects with and without adenomas, 3) assess the association between adherent bacteria profiles and diet/lifestyle such as fiber, meat intake, obesity (body mass index (BMI), waist-hip-ratio), and NSAID use in relation to colorectal adenomas. Evaluation of the diversity of gut bacteria in relation to disease in humans is limited in part, by the difficulty growing these organisms in culture. Recent advances in molecular methods have made it possible to assess the role of intestinal microbiota in diseases such as colon cancer. To test our hypothesis, we propose to use molecular-phylogenetic methods based on the highly conserved 16S bacteria rRNA gene to assess the contribution of intestinal microbiota to the development of colorectal adenomas. These methods include PCR amplification of the 16S rRNA gene, terminal restriction fragment length polymorphism (TRFLP), generation of bacteria clone libraries and sequencing. This study will use colonic biopsy specimens obtained from 600 patients (300 cases and 300 controls) and risk factor data such as diet and inflammation from a funded ongoing study of colorectal adenomas, the Diet and Health Study (NCI R01 CA 44684). Limited information exists on the role of gut bacteria in the development of adenomas. This study will provide critical insights on the composition and diversity of the microbiota and their association with colorectal adenomas and known risk factors. The findings from this study could lead to the development of strategies to manipulate the intestinal microbiota to prevent colorectal adenomas and cancer as well as identify individuals at high risk.