Vitamin D3, Calcium and Biomarkers of Gut Barrier Function

描述(申请人提供)：补钙可导致散发性结直肠腺瘤复发，血清维生素D水平升高与结直肠癌风险降低有关，结直肠癌是美国癌症死亡的第二大原因。尽管有很强的生物学可信度和支持性的观察数据，但钙和维生素D在人类中的独立和协同抗肿瘤作用尚不清楚。已提出的机制包括保护结肠上皮免受胆汁酸的影响，直接影响细胞周期，调节生长因子信号，炎症和免疫功能。基于基础科学和有限的人类证据，我们建议检验一种新的假设，即补充钙和维生素D可以通过调节细胞周期、细胞黏附、对细菌成分的反应受体和肠道炎症标志物来增强肠道粘膜屏障。我们还假设，结肠中的这些变化将伴随着结肠高通透性和促炎细胞因子的循环生物标志物水平的下降。我们将在一项正在进行的多中心、随机、双盲、安慰剂对照、2×2因素化学预防临床试验(n=2,259)的辅助研究中对这一点进行调查。该临床试验是补充钙(每天1,200毫克元素钙作为碳酸钙)和维生素D3(每天1,000国际单位)的补充，持续3-5年，与安慰剂相比(“父母研究”)。在这项辅助研究中，选择了一组参与者(n=112)，他们在基线时进行了正常直肠黏膜的“非准备”活组织检查，并进行了一年的乙状结肠镜检查。这项研究的主要目的是：1)获得补充钙和维生素D3对正常直肠黏膜组织中肠道屏障功能生物标志物(Ki-67/mib-1、caspase-3、TLR4、TLR5、ZO-1、claudin-1、occludin、粘蛋白-17、E-钙粘蛋白和β-catenin)和炎症(NFkappaB和TNFpha)的单独和联合影响的初步数据；2)研究组织特异性生物标志物的发现是否与肠道屏障功能的循环生物标志物(对脂多糖和旗帜的特异性Ig G和A)、脂多糖结合蛋白[LBP]、和肠道脂肪酸 结合蛋白[I-FABP])和炎症(GM-CSF、IFNGamma、IL-6、IL-1β、IL-2、IL-8、IL-10、IL-12p70和TNFpha)。拟议的工作范围仅限于使用生物样本和“家长研究”的问卷数据进行的实验室和统计分析。这项辅助研究在一项正在进行的大型人体试验中提供了一个独特的、具有成本效益的机会，以探索钙和维生素D有益于调节肠道屏障功能的新假设，并阐明钙和维生素D对肠道屏障功能和炎症的生物标记物的联合影响。了解维生素D和钙在肠道屏障功能中的作用，不仅对大肠肿瘤的化学预防具有重要意义，而且对预防胃肠道的多种病理状态也具有重要意义。

DESCRIPTION (provided by applicant): Calcium supplementation educes sporadic colorectal adenoma recurrence, and higher serum vitamin D levels are associated with reduced risk for colorectal cancer, the second leading cause of cancer deaths in the U.S. Despite strong biological plausibility and supportive observational data, the independent and synergistic anti- neoplastic effects of calcium and vitamin D in humans are not clear. Proposed mechanisms have included protection of the colonic epithelium against bile acids, direct effects on the cell cycle, modulation of growth factors signaling, inflammation, and immune function. Based on basic science and limited human evidence, we propose to test a novel hypothesis that calcium and vitamin D supplementation strengthens the gut mucosal barrier as indicated by modulation of cell cycle, cell adhesion, receptors responsive to bacterial components, and markers of intestinal inflammation in humans. We also hypothesize that these changes in the colon will be accompanied by decreases in circulating levels of biomarkers of colonic hyperpermeability and pro-inflammatory cytokines. We will investigate this in an adjunct study to an ongoing multi-center, randomized, double-blind, placebo-controlled, 2 x 2 factorial chemoprevention clinical trial (n = 2,259) of supplemental calcium (1,200 mg elemental calcium daily as calcium carbonate) and vitamin D3 (1,000 IU daily), alone and in combination vs. placebo over 3 - 5 years (the 'parent study'). A sub-set of participants (n = 112) with "non-prep" biopsies of normal-appearing rectal mucosa taken at baseline and 1-year follow-up sigmoidoscopies is selected for this adjunct study. The primary aims of the proposed study are to 1) obtain preliminary data on the separate and joint effects of calcium and vitamin D3 supplementation on biomarkers of gut barrier function (Ki-67/MIB-1, caspase-3, TLR4, TLR5, ZO-1, claudin-1, occludin, mucin-17, E-cadherin, and beta-catenin) and inflammation (NFkappaB and TNFalpha) in biopsies of normal-appearing rectal mucosa, and 2) investigate whether the findings for the tissue-specific biomarkers are correlated with circulating biomarkers of gut barrier function (specific IgG and IgA to lipopolysaccharide [LPS] and flagellin, LPS binding protein [LBP], and intestinal fatty acid binding protein [I-FABP]) and inflammation (GM-CSF, IFNgamma, IL-6, IL-1beta, IL-2, IL-8, IL- 10, IL-12p70, and TNFalpha). The proposed scope of work is limited to laboratory and statistical analyses using biological samples and questionnaire data from the 'parent study'. This adjunct study offers a unique, cost-effective opportunity in a large, ongoing trial in humans to explore a novel hypothesis that calcium and vitamin D beneficially modulate gut barrier function, and to elucidate the combined effects of calcium and vitamin D on biomarkers of gut barrier function and inflammation. Understanding the role of vitamin D and calcium in gut barrier function is of great importance, not only to colorectal neoplasm chemoprevention, but also to the prevention of multiple pathological conditions of the gastrointestinal tract.