Role of mesenteric lymphatics and dietary endotoxin in metabolic syndrome

描述（由申请方提供）：尽管超过95%的膳食脂质通过肠循环从小肠吸收，并通过肠系膜收集循环通过淋巴网络转运至血液，但淋巴转运在脂质代谢调节中的作用尚不清楚。我们最近发现，高果糖饮食诱导的代谢综合征（MetSyn）大鼠表现出受损的肠系膜淋巴功能。膳食内毒素容易与乳糜微粒结合，并主要通过肠系膜淋巴管与许多其他肠肽和激素一起沿着吸收，这表明膳食内毒素如脂多糖（LPS）的主要运输是通过淋巴管。 因此，重要的问题仍然没有答案：1）淋巴功能在饮食内毒素中的作用和对饮食内毒素的反应性是什么，以及2）这如何影响MetSyn的进展。我们的初步数据表明，免疫细胞，嗜酸性粒细胞和嗜中性粒细胞存在于淋巴管壁上或附近，并且在LPS诱导的炎症肠系膜组织中，淋巴管壁上这些免疫细胞的数量减少。这些数据为我们的中心假设提供了基础：饮食内毒素改变了肠系膜环境中的局部线索（嗜酸性粒细胞和中性粒细胞的主要细胞因子：IL-4、IL-5、IL-8和IL-13），损害了淋巴功能和乳糜微粒转运，导致血脂异常和肠系膜脂肪蓄积，这两者都是MetSyn发展的关键病理决定因素。我们将使用高果糖和高脂肪饮食诱导的MetSyn大鼠模型和LPS诱导的炎症模型来确定淋巴系统在MetSyn病理生理学中的作用。具体目标是：1）证明饮食内毒素、促炎细胞因子和MetSyn发展过程中淋巴功能之间的联系; 2）确定MetSyn发展中淋巴转运减少的功能后果和分子机制;和3）为了测试将IL-8，IL-4，IL-5和IL-13在MetSyn发育过程中调节淋巴功能。我们将使用全肠系膜标本进行免疫组织化学研究，原位标本进行淋巴流量和淋巴收缩性研究，分离/插管血管进行血管收缩特性研究，钢丝肌描记术研究进行长度-张力和力-钙测量。这些实验将具体说明饮食内毒素如何影响M1和M2巨噬细胞对淋巴细胞的极化，以及淋巴肌细胞中嗜酸性粒细胞和嗜中性粒细胞白介素、IL-4、IL-5、IL-8和IL-13以及miR-19 a、93、200 c和203调节淋巴结构和功能的机制。因此，该提案将确定连接肠系膜环境和淋巴功能的重要靶点，这可能提供诊断工具和/或治疗方法来改善淋巴转运，从而改善MetSyn等慢性炎症性疾病的健康状况。

DESCRIPTION (provided by applicant): Although more than 95% of dietary lipids are absorbed from the small intestine via the intestinal lymphatics, transported via the mesenteric collecting lymphatics through the lymphatic network en route to the blood, the role of lymph transport in the regulation of lipid metabolism is poorly understood. We have recently shown that high fructose diet-induced metabolic syndrome (MetSyn) rats exhibit impaired mesenteric lymphatic function. Dietary endotoxin readily associates with chylomicrons and are primarily absorbed through the mesenteric lymphatics along with many other gut peptides and hormones, suggesting that the primary trafficking of dietary endotoxins, such as, lipopolysaccharide (LPS) is via lymphatics. Hence, important questions remain unanswered: 1) what are the roles of lymphatic function in and responsiveness to dietary endotoxin and 2) how does that affect the progression of MetSyn. Our preliminary data show that immune cells, eosinophils and neutrophils are present on or adjacent to the lymphatic wall, and that the number of these immune cells on the lymphatic wall is decreased in LPS-induced inflamed mesenteric tissue. These data provide the basis for our central hypothesis: That dietary endotoxins alters the local cues (major cytokines of eosinophil and neutrophil: IL-4, IL-5, IL-8 and IL-13) in the mesenteric milieu that impairs lymphatic function and chylomicron transport, which leads to dyslipidemia and mesenteric adipose accumulation, both key pathologic determinants of the development of MetSyn. We will use the high-fructose and high-fat diet-induced MetSyn rat models and a LPS-induced inflammation model to determine the roles of the lymphatic system in the pathophysiology of MetSyn. Specific Aims are: 1) To demonstrate the linkages between dietary endotoxins, pro-inflammatory cytokines and lymphatic function during the development of MetSyn; 2) To determine the functional consequences and molecular mechanisms of reduced lymph transport in the development of MetSyn; and 3) To test the roles of micro RNAs (miRs) that interconnect the regulation of IL-8, IL-4, IL-5 and IL-13 in modulating lymphatic function during the development of MetSyn. We will use whole-mount mesenteric preparations for immunohistochemical studies, in situ preparations for lymph flow and lymphatic contractility, isolated/cannulated vessels for contractile characteristics of lymphatics, wire-myograph studies for length- tension and force-calcium measurements. These experiments will specifically address how dietary endotoxins effect the M1 and M2 macrophage polarization on lymphatics and the mechanisms by which the eosinophil and neutrophil interleukins, IL-4, IL-5, IL-8 and IL-13, and miR-19a, 93, 200c and 203 in lymphatic muscle cells regulate the lymphatic structure and function. Thus, this proposal will identify important targets bridging the mesentery milieu and lymphatic function, which could potentially provide diagnostic tools and/or therapies to improve lymph transport, and thus improve health in chronic inflammatory conditions such as MetSyn.