Enhancement of NAFLD risk by vinyl chloride: interaction of gut-liver-adipose axi

描述(申请人提供)：肥胖及其代谢并发症是美国和世界范围内的主要健康问题。与肥胖相关的一种主要疾病是非酒精性脂肪性肝病(NAFLD)。事实上，肥胖可能会影响个体对其他环境暴露的敏感性，如氯乙烯(VC)。具体地说，我们假设实验性NAFLD使肝脏对VC作为第二次打击敏感。最近的研究表明，肠道屏障功能和胃肠道菌群在NAFLD的发生发展中起着关键作用。补充益生菌已被证明可以降低诱导的肠道通透性和肝脏损伤。因此，我们认为VC通过改变细胞内信号级联，损害NAFLD屏障功能的完整性，而益生菌补充剂[Lactobacillusrhamnosus Gorbach-Goldin(LGG)]将减弱这些影响。目的1.验证VC暴露可加重HFD肝损伤的假说。众所周知，高脂(HFD)饮食会增加肝脏损伤。已有研究表明，VC具有肝毒性。我们认为VC暴露会加重实验性非酒精性脂肪肝(HFD)所致的小鼠肝损伤。Subaims将确定：a)最低剂量的VC暴露条件会加剧HFD引起的脂肪肝；b)VC暴露会加剧HFD引起的肝脏损害的潜在机制。目的2.探讨维生素C加重高脂饲料所致脂肪性肝病的机制。众所周知，胃肠道之间存在着一个关键的串扰，脂肪组织和肝脏在NAFLD的发展中起着重要的作用(即肠道-肝脏-脂肪轴)。本研究的目的是确定VC代谢物对肠道-肝脏-脂肪轴的体外反应模式的影响。Subaims将描述以下方面的反应：a)肝细胞对细胞毒性刺激的反应，b)巨噬细胞对炎症刺激的反应，c)脂肪细胞刺激产生成脂介质。目的3.验证VC暴露可加重HFD引起的肠道通透性的假说。众所周知，喂食HFD后，肠道通透性增加。肠道上皮的屏障功能也依赖于肠道微生物区系。益生菌已被证明可以改善肠道上皮的屏障完整性。我们认为，VC暴露会加剧HFD引起的小鼠肠道通透性，肠道微生物区系在喂养HF小鼠的肠道通透性和VC诱导的毒性中起着重要作用。我们将进一步确定益生菌[例如，鼠李糖乳杆菌GG(LGG)]是否会通过改善肠道通透性和TJ完整性来减少VC对喂食HF小鼠的毒性。Subaims将确定：a)VC和HFD对体内(小鼠)和体外(Caco-2细胞)肠道完整性的联合作用；b)VC和膳食脂肪酸对Caco-2细胞关键紧密连接蛋白mRNA和表面表达的影响以及SAPK信号在这一过程中的作用；c)HFD和VC是否在体内协同损害TJ屏障功能；以及d)益生菌LGG对HFD和VC诱导的肠通透性的保护作用。

DESCRIPTION (provided by applicant): Obesity and its metabolic complications are major health problems in the United States and worldwide. A major disease associated with obesity is non-alcoholic fatty liver disease (NAFLD). Indeed, obesity may influence individual susceptibility to other environmental exposures such as vinyl chloride (VC). Specifically, we hypothesize that experimental NAFLD sensitizes the liver to VC as a 2nd hit. Recent studies indicate that intestinal barrier function and GI tract flora play a key role in the development of NAFLD. Supplementation with probiotics has been shown to decrease induced gut permeability and liver injury. We therefore propose that VC, via altering intracellular signaling cascades, impairs barrier function integrity in NAFLD and that probiotic supplementation [Lactobacillus rhamnosus Gorbach-Goldin (LGG)] will attenuate these effects. Aim 1. To test the hypothesis that VC exposure exacerbates liver injury caused by HFD. It is well-known that liver injury is increased by high fat (HFD) diet. It has been shown that VC is hepatotoxic. We propose here that VC exposure will exacerbate liver injury caused by experimental NAFLD (HFD) in mice. Subaims will determine: a) the minimal low dose VC exposure conditions that exacerbate fatty liver due to HFD; b) potential mechanisms by which VC exposure enhances liver damage caused HFD. Aim 2. To determine mechanisms by which VC accentuates fatty liver disease caused by HFD. It is known that there is a critical crosstalk between the GI tract, the adipose tissue and the liver tha plays an important role in the development of NAFLD (i.e., the 'gut-liver-adipose axis'). The purpose of this Aim is to determine the effect of VC metabolites on responses in in vitro paradigms of the gut-liver-adipose axis. Subaims will characterize the response of: a) hepatocytes to cytotoxic stimuli, b) response of macrophages to inflammatory stimuli, and c) stimulus of adipocytes to produce adipogenic mediators. Aim 3. To test the hypothesis that VC exposure exacerbates intestinal permeability caused by HFD. It is known that intestinal permeability is increased after HFD feeding. The barrier function of the intestinal epithelium is also dependent on the gut microbiota profile. Probiotic microorganisms have been shown to improve barrier integrity of the intestinal epithelium. We propose here that VC exposure will exacerbate gut permeability due to HFD in mice and that gut microbiota play an important role in gut permeability and VC-induced toxicity in HF-fed mice. We will further determine if probiotics [e.g., lactobacillus rhamnosus GG (LGG)] will decrease VC-induced toxicity in HF-fed mice via improvement of gut permeability and TJ integrity. Subaims will determine: a) the combined effect of VC and HFD on intestinal integrity in vivo (mice) and in vitro (Caco-2 cells); b) the effct of VC and dietary fatty acids on mRNA and surface expression of key tight junction proteins and the role of SAPK signaling in this process in Caco-2 cells; c) if HFD and VC synergistically impair TJ barrier functions in vivo; and d) the protective effect of probiotic LGG on HFD and VC-induced gut permeability.