Dietary Fructose-Induced Metabolic Reprogramming in Intestinal Epithelial Cells Results in Gut Microbiota Dysbiosis

非酒精性脂肪性肝病(NAFLD)现在是美国最常见的肝病。NAFLD的临床负担不仅限于与肝脏相关的发病率或死亡率，而且还增加了心血管疾病(CVD)、2型糖尿病和癌症的风险。到目前为止，还没有FDA批准的药物疗法。因此，NAFLD给美国带来了一个重要的健康问题和巨大的经济负担。膳食中果糖摄入量的增加是NAFLD发生和发展的重要危险因素。新的证据支持肠道微生物区系失调和肠道屏障功能障碍在NAFLD的发展中起关键作用的概念，包括饮食高果糖诱导的NAFLD。然而，饮食中的果糖摄入如何改变肠道微生物群还没有被阐明。宿主和肠道微生物区系之间的相互作用是维持肠道上皮细胞“生理性低氧”的关键，而“生理性低氧”对肠道健康和抗病能力非常重要。平衡的肠道微生物区系的特征是专性厌氧细菌的优势，而变形杆菌的增加通常被认为是微生态失调的标志。专性厌氧菌防止病原性兼性厌氧菌的扩张，部分是通过限制宿主来源的硝酸盐和氧气的产生。我们的初步数据显示，长期饮用10%葡萄糖(w/v)或10%果糖(w/v)的雄性大鼠会导致肠道微生物区系失调。我们假设肠上皮细胞中的果糖代谢导致代谢重编程，从而将宿主的代谢途径从线粒体β氧化切换到糖酵解。这会导致“生理性缺氧”和肠道氧合的破坏，从而抑制专性厌氧菌的生长，促进病原菌的扩张。我们将在三个具体目标上检验我们的假设。目的1.确定果糖是否诱导肠上皮细胞代谢重编程，并确定这是否导致肠道微生物区系失调。目的2.确定肠道上皮细胞糖酵解活性的调节是否改变肠道微生物区系组成。目的3.确定果糖诱导的肠道微生物区系失调是否由HIF-1介导。

Nonalcoholic fatty liver disease (NAFLD) is now the most common liver disease in the US. The clinical burden of NAFLD is not restricted to liver-related morbidity or mortality, but it also increases the risk of cardiovascular disease (CVD), type 2 diabetes and cancer. As yet, there currently is no FDA-approved drug therapy. Thus, NAFLD imposes an important health problem and huge economic burden in the US. Increased dietary fructose consumption is an important risk factor in the pathogenesis and progression of NAFLD. Emerging evidence supports the concept that gut microbiota dysbiosis and gut barrier dysfunction play critical roles in the development of NAFLD, including dietary high fructose-induced NAFLD. However, how dietary fructose intake alters the gut microbiome has not been elucidated. Cross-talk between host and gut microbiota is key for maintaining “physiologic hypoxia” in the intestinal epithelial cells, which is important for a healthy gut and disease resistance. A balanced gut microbiota is characterized by the dominance of obligate anaerobic bacteria of Firmicutes and Bacteroidetes phyla, whereas increased abundance of Proteobacteria is generally considered a signature of dysbiosis. Obligate anaerobic bacteria prevent pathogenic facultative anaerobic bacteria expansion, in part by limiting the generation of hostderived nitrate and oxygen. Our preliminary data showed that male rats fed chronically with either 10% glucose (w/v) or 10% fructose (w/v) in the drinking water results in gut microbiota dysbiosis. We hypothesize that fructose metabolism in the intestinal epithelial cells results in metabolic reprogramming which switches the host metabolic pathway from mitochondrial β-oxidation to glycolysis. This leads to the disruption of “physiologic hypoxia”, and intestinal oxygenation, thus inhibiting the growth of obligate anaerobic bacteria and facilitating the expansion of pathogenic bacteria. We will test our hypothesis in three specific aims. Aim 1. Determine whether fructose induces metabolic reprogramming in intestinal epithelial cells and determine if this results in gut microbiota dysbiosis. Aim 2. Determine whether modulation of glycolytic activity in intestinal epithelial cells alters gut microbiota composition. Aim 3. Determine whether fructose induced gut microbiota dysbiosis is mediated by HIF-1.