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

描述（由申请人提供）：肥胖及其代谢并发症是美国和全球的主要健康问题。与肥胖相关的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（如氯乙烯）的敏感性。具体来说，我们假设实验性NAFLD使肝脏对VC敏感，作为第二次打击。近年来的研究表明，肠道屏障功能和胃肠道植物群在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损伤。因此，我们认为VC通过改变细胞内信号级联，损害NAFLD中屏障功能的完整性，而益生菌补充剂[鼠李糖乳杆菌Gorbach-Goldin（LGG）]将减弱这些影响。目标1.检验VC暴露加重HFD引起的肝损伤的假设。众所周知，高脂肪（HFD）饮食会增加肝损伤。已表明VC具有肝毒性。我们在这里提出，VC暴露会加重实验性NAFLD（HFD）引起的小鼠肝损伤。Subaims将决定：a）最小低剂量VC暴露条件会加重HFD引起的脂肪肝; B）VC暴露增强HFD引起的肝损伤的潜在机制。目标2.确定VC加重HFD引起的脂肪肝的机制。已知在胃肠道、脂肪组织和肝脏之间存在关键串扰，其在NAFLD的发展中起重要作用（即，“肠-肝-脂肪轴”）。本研究的目的是确定VC代谢产物对肠-肝-脂肪轴体外范例反应的影响。Subaims将表征以下反应：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，以及c）刺激脂肪细胞产生脂肪生成介质。目标3：检验VC暴露加剧HFD引起的肠道通透性的假设。已知在HFD喂养后肠通透性增加。肠上皮的屏障功能也取决于肠道微生物群特征。益生菌微生物已被证明可以改善肠上皮的屏障完整性。我们在这里提出，VC暴露将加剧肠道通透性由于HFD在小鼠和肠道微生物群在肠道通透性和VC诱导的毒性在HF喂养的小鼠中发挥重要作用。我们将进一步确定是否益生菌[例如，鼠李糖乳杆菌GG（LGG）]通过改善肠道通透性和TJ完整性，降低HF喂养小鼠中VC诱导的毒性。Subaims将决定：a）VC和HFD对体内（小鼠）和体外肠完整性的联合作用（Caco-2细胞）; B）VC和膳食脂肪酸对Caco-2细胞中关键紧密连接蛋白的mRNA和表面表达的影响以及SAPK信号传导在该过程中的作用; c）HFD和VC是否协同损害体内TJ屏障功能;和d）益生菌LGG对HFD和VC诱导的肠道通透性的保护作用。

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.