Mechanisms of Enteroendocrine Cell Adaptation to High Fat Diet in Zebrafish

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ABSTRACT Enteroendocrine cells (EECs) are key sensory cells in the intestinal epithelium that secrete diverse hormones important in many processes dysregulated in metabolic disease in humans, such as satiety signaling and glucose homeostasis. EECs are divided into subtypes based on their predominant hormone. As enteroendocrine hormones have different and sometimes antagonistic metabolic effects, this subdivision enables finely-tuned control of metabolism in response to a variety of dietary stimuli. Many reports have shown that this careful balance is disturbed in humans and mice with obesity and metabolic disease, including changes in the number of EECs, EEC subtype distribution, and circulating EEC hormone levels. Despite these advances, we still do not understand the processes that regulate EEC adaptation to diet and how these processes may differ across EEC subtypes. To address these gaps in knowledge, my mentors’ labs recently established zebrafish as a model system for studying EEC physiology. The optical transparency of larval zebrafish enables live imaging to observe EEC adaptations in vivo and in real time, a level of resolution not available in live mammals. Using the zebrafish, we discovered a novel phenomenon of acute change in EEC morphology and reduction in EEC nutrient sensitivity after high fat feeding we named “EEC silencing.” The objective of this proposal is to understand the molecular and cellular mechanisms underlying this high fat feeding-induced EEC adaptation. Specifically, I will test the contributions of lipid signaling from enterocytes and hormone signaling from an inhibitory EEC subtype in mediating high fat feeding-induced EEC silencing. This work is expected to significantly advance our understanding of the fundamental physiology of intestinal adaptation to diet with important implications for human metabolic disease.