Enteroendocrine Regulation of Intestinal Metabolism

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PROJECT SUMMARY Dr. Heather McCauley is mentored by Dr. James Wells at Cincinnati Children’s Hospital Medical Center (CCHMC), the largest pediatric research institution in the nation. CCHMC ranked 2nd in NIH support in 2017 and is home to an NIDDK-sponsored Digestive Diseases Research Center with a vibrant community of physicians and scientists. CCHMC provides a very supportive training environment for young investigators. Dr. McCauley proposes an innovative cross-disciplinary research plan which bridges developmental biology, stem cell and organoid medicine, gastroenterology and nutrition, endocrinology, and metabolism. Enteroendocrine cells (EECs) are specialized intestinal epithelial cells which secrete more than 20 bioactive peptides to regulate satiety, gut motility, glucose homeostasis, nutrient absorption, and whole-body metabolism in response to ingested nutrients. While the systemic targets of EEC hormones are well known, such as the brain and the pancreas, the role of EEC peptides in regulating the function of the intestine itself is surprisingly understudied. Our lab has developed a unique, high-throughput human model system to test the roles of individual EEC peptides on intestinal function by generating EEC-deficient human intestinal organoids from pluripotent stem cells. We recently used this model system to show that some EECs regulate ion-coupled nutrient absorption in neighboring cells. Because EECs are nutrient-sensing cells, we considered that they might coordinate other intestinal responses to nutrient availability. Most EEC peptides signal via G-protein coupled receptors which activate second messengers to modulate the function of their target cell. These second messengers are intimately linked to ancient regulators of cellular metabolism, such as mammalian target of rapamycin (mTOR), which are known to play essential roles in many intestinal functions. This proposal will test the hypothesis that EECs regulate cellular metabolism in the stem cell niche (Aim 1) and in the differentiated enterocyte (Aim 2), thus impacting both intestinal homeostasis and efficiency of nutrient absorption. As EECs are now common targets for the treatment of type 2 diabetes, understanding how EECs affect intestinal metabolism and function will inform how dietary or pharmacological manipulation of EECs will impact gut health, nutrient absorption, and whole-body metabolism. To ensure success of the proposed research strategy, Dr. McCauley requires additional mentored time to become fluent in metabolic and metabolomic assays. Dr. McCauley has obtained a co-mentor, Dr. Kenneth Setchell, an international expert in using Mass Spectrometry to understand nutrition- and digestive disease- related changes in metabolism. Dr. McCauley proposes a rigorous yet feasible schedule of formal and informal training opportunities in metabolomics. At the conclusion of the mentored portion of her training, Dr. McCauley will be established as a fully independent, leading young investigator in the field of gastrointestinal metabolism, a critically understudied niche in the GI community.