Mechanisms of Probiotics in Alcoholic Liver Disease

重症酒精性肝病(ALD)具有较高的发病率和死亡率。最近的研究表明， 益生菌逆转酒精诱导的动物肝脏脂肪变性和炎症，并改善肝酶 模特和病人。我们的实验室显示，给药的益生菌菌株，鼠李糖乳杆菌 Gorbach-Goldin(LGG)，显著改善酒精处理小鼠的肝酶和组织学。这些老鼠 也降低了肠道通透性和血浆内毒素水平。肠源性内毒素正常 由于受到严格调控的肠道屏障功能，穿透肠道上皮的量很少。然而， 在包括酗酒在内的病理条件下，内毒素泄漏会增加。我们最近报道了 小鼠长期饮酒导致MASTER在肠道的表达显著减少 转录因子、缺氧诱导因子(HIF)和两种HIF相关蛋白、凯瑟琳相关抗菌剂 肠道中的多肽(JUMP)和肠三叶因子(ITF)。ITF在形成和发展过程中起着关键作用 稳定肠粘液屏障，促进快速肠道修复(恢复)和调节 粘膜分化过程和免疫反应，而痉挛在阻塞肠道中起重要作用 细菌过度生长/生物失调。此外，我们的初步数据显示，做空显著减少 酒精暴露后肠道中的链脂肪酸(SCFA)，特别是丁酸 啮齿动物。我们的假设是，饮酒会导致肠道痉挛和ITF表达减少 和肠腔丁酸浓度过高，导致细菌过度生长/生物失调而中断 肠道屏障功能；补充lgg可减轻这些有害影响，并保护肝脏免受 酒精引起的伤害。为了验证这一假设，我们将有三个具体目标。具体目标1将决定 抽筋在酒精所致肠道微生物区系改变中的作用及免疫球蛋白的改善作用 动态平衡。这些实验将在抽筋基因敲除小鼠中使用元基因组学方法进行。 特异性目标2将确定LGG在促进ITF表达方面的作用，并将评估ITF 积极调节肠道紧密连接，作为改善肠道屏障完整性的一种机制。我们会 采用杯状培养、肠上皮细胞培养、重组ITF等方法观察ITF的作用。具体目标3 将确定丁酸在LGG改善肠紧张性疾病中的作用和机制 连接使用丁酸转运蛋白基因敲除小鼠模型。这项研究将对 开发以益生菌为基础的防治酒精性肝病的新治疗策略。

Severe alcoholic liver disease (ALD) has a high morbidity and mortality. Recent studies demonstrated that probiotics reversed alcohol-induced hepatic steatosis and inflammation, and improved liver enzymes in animal models and in patients. Our laboratory showed that administration of a probiotic strain, Lactobacillus rhamnosus Gorbach-Goldin (LGG), significantly improved liver enzymes and histology in alcohol treated mice. These mice also had reduced intestinal permeability and plasma endotoxin levels. Gut-derived endotoxins normally penetrate the gut epithelium only in trace amounts due to tightly regulated intestinal barrier function. However, endotoxin leakiness is increased under pathological conditions, including alcohol abuse. We recently reported that chronic alcohol intake in mice caused a marked reduction in the intestinal expression of the master transcription factor, hypoxia inducible factor (HIF), and two HIF related proteins, cathelin-related antimicrobial peptide (CRAMP) and intestinal trefoil factor (ITF), in the intestine. ITF plays a critical role in the formation and stabilization of the intestinal mucus barrier, enhancement of rapid intestinal repair (restitution), and modulation of mucosal differentiation processes and immune responses, while CRAMP is important in blocking intestinal bacterial overgrowth/dysbiosis. In addition, our preliminary data demonstrate a significant decrease of short chain fatty acids (SCFAs), in particular, butyric acid, in the intestinal lumen following alcohol exposure in rodents. Our hypothesis is that alcohol consumption causes decreased intestinal CRAMP and ITF expression and intestinal lumen butyric acid concentration, resulting in bacterial overgrowth/dysbiosis and disrupted gut-barrier function; LGG supplementation attenuates these deleterious effects and protects the liver from alcohol-induced injury. To test this hypothesis, we will have 3 specific aims. Specific aim 1 will determine the role of CRAMP and the beneficial effects of LGG on CRAMP in alcohol-mediated changes in gut microbiota homeostasis. The experiments will be performed using a metagenomic approach in CRAMP knockout mice. Specific aim 2 will determine the role of LGG in promoting ITF expression and will evaluate whether ITF positively modulates intestinal tight junctions as a mechanism for improved intestinal barrier integrity. We will use goblet and intestinal epithelial cell culture, and recombinant ITF to delineate the effect of ITF. Specific aim 3 will determine the role and mechanisms of butyric acid in the beneficial effects of LGG on intestinal tight junctions using a butyric transporter knockout mouse model. This study will have a major impact on the development of probiotic-based new therapeutic strategy for the prevention and treatment of ALD.