Intestinal Regulation of Gut Microbiota and Metabolism

在过去的几十年里，美国的肥胖率急剧上升。肥胖是由于食物摄入量和能量消耗之间的不平衡造成的，并与几种并发症密切相关，包括2型糖尿病(T2D)和非酒精性脂肪肝(NAFLD)。不幸的是，目前的治疗方法在减轻肥胖及其并发症方面的能力有限。因此，迫切需要更好地了解能量平衡和代谢的机制，以便开发治疗肥胖及其并发症的新策略。哺乳动物5‘-AMP激活的蛋白激酶(AMPK)是细胞营养和能量动态平衡的重要感受器。由于AMPK在控制能量稳态方面的关键作用，它作为一种潜在的代谢性疾病的治疗靶点引起了广泛的兴趣，包括肥胖症、T2D和NAFLD。AMPK在包括肠道在内的几个组织中都有表达，这被认为是代谢调节和介导二甲双胍等药物治疗效果的关键。然而，与AMPK在其他组织中相对成熟的功能相比，肠道AMPK在调节能量和新陈代谢方面的作用仍然很大程度上尚不清楚。为了填补在了解肠道AMPK作用方面的知识空白，我们产生了肠上皮特异性AMPK基因敲除(AMPK-IKO)小鼠品系。我们在饮食诱导肥胖(DIO)AMPK-IKO小鼠中观察到一个令人惊讶的发现，即BAT产热功能受损，并加剧了胰岛素抵抗。有趣的是，我们发现AMPK-Iko小鼠的肠道微生物区系与AMPKfl/fl对照组小鼠相比发生了改变，来自AMPK-Iko小鼠的粪便微生物区系移植(FMT)重现了野生型小鼠的AMPK-Iko表型。更有趣的是，我们发现AMPK-Iko小鼠的肠道抗菌肽(AMP)的表达显著低于AMPKfl/fl小鼠，二甲双胍治疗诱导了AMPKf1/fl小鼠的AMP表达，但不诱导AMPK-Iko小鼠的AMP表达。基于这些和其他初步结果，我们假设肠道AMPK与BAT的串扰通过调节肠道微生物区系组成来调节产热和代谢。我们提出了三个特定的目标来验证我们的假设：1)确定肠道AMPK在调节能量和代谢中的作用；2)确定肠道微生物区系及其代谢产物在介导肠道AMPK对能量平衡和代谢的调节作用中的作用；以及3)研究肠道AMPK改变肠道微生物区系的机制。这些研究将确定和表征一种重要的新的肠道-蝙蝠通讯机制，这可能填补我们目前对肠道是AMPK作用的关键部位和二甲双胍在代谢调节中的关键部位的认识空白。我们还期待该项目将确定治疗肥胖症及其并发症的新靶点和潜在的新疗法。

The incidence of obesity in the US has increased dramatically over the last few decades. Obesity develops due to an imbalance between food intake and energy expenditure and is significantly associated with several complications, including type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD). Unfortunately, current treatments are limited in their ability to mitigate obesity and its complications. Therefore, there is an urgent need to better understand the mechanisms governing energy balance and metabolism in order to develop novel strategies to treat obesity and its complications. Mammalian 5′-AMP-activated protein kinase (AMPK) is an essential sensor of cellular nutrition and energy homeostasis. Given its key role in controlling energy homeostasis, AMPK has attracted widespread interest as a potential therapeutic target for metabolic diseases, including obesity, T2D, and NAFLD. AMPK is expressed in several tissues including the intestine, which is considered critical for metabolic regulation and mediating the therapeutic effects of drugs such as metformin. However, in contrast to the relatively well-established functions of AMPK in other tissues, the role of intestinal AMPK in regulating energy and metabolism remains largely unexplored. In order to fill the knowledge gap in understanding intestinal AMPK action, we generated an intestinal epithelium-specific AMPK knockout (AMPK- IKO) mouse strain. We observed a surprising finding of impaired BAT thermogenesis and exacerbated insulin resistance in the diet-induced obese (DIO) AMPK-IKO mice. Interestingly, we found that the gut microbiota profile of AMPK-IKO mice was shifted compared to that of AMPKfl/fl control mice, and fecal microbiota transplantation (FMT) from AMPK-IKO mice recapitulated the AMPK-IKO phenotype in wild-type mice. More interestingly, we found that expression of intestinal antimicrobial peptides (AMPs) was significantly lower in the intestines of AMPK-IKO mice compared to AMPKfl/fl mice, and metformin treatment induced AMP expression in AMPKfl/fl mice but not AMPK-IKO mice. Based on these and other preliminary results, we hypothesize that intestinal AMPK cross-talk with BAT regulates thermogenesis and metabolism through modulating gut microbiota composition. We propose three Specific Aims to test our hypothesis: 1) Determine the role of intestinal AMPK in regulating energy and metabolism; 2) Determine the role of gut microbiota and their metabolites in mediating the regulatory effects of intestinal AMPK on energy balance and metabolism; and 3) Investigate the mechanism by which intestinal AMPK modifies the gut microbiota profile. These studies will identify and characterize an important new mechanism of intestine-BAT communication, which may fill the gap of knowledge of our current understanding how intestine is a key site of AMPK action and metformin in metabolic regulation. We also expect that this project will identify novel targets and potential novel therapies for the treatment of obesity and its complications.