Despite its long history, the nutrient biology field is still facing a plethora of outstanding questions closely related to human health, two of which will be explored in this proposal. First, the nutrient value of many specific molecules in our diet, or the beneficial impact of many specific bacterial metabolites on human physiology (as predicted by the symbiotic relationship between commensal microbes and host animals), remain unclear. Second, whereas great advances have been made in the last decades on understanding signaling systems that sense the levels of glucose, amino acids and other well-studied nutrients to regulate various physiological events, the mechanisms that respond to the level of many other specific nutrients, including certain fatty acids, nucleotide variants and micronutrients, are largely unexplored. About 6 years ago, our lab boldly moved the major research direction to study problems related to nutrient functions and sensing, focusing mainly on under-explored fatty acid variants, nucleotides and bacterial metabolites, using the nematode C. elegans as the primary model with additional analysis in mice and mammalian cells. In one aspect, we developed innovative assays to identify the unknown beneficial impact of bacterial metabolites, including the siderophore enterobactin and bacterial cell wall components peptidoglycan (PG), on animal development and behaviors. Under this MIRA grant, we will carry out a thorough investigation of the newly discovered beneficial roles of PG fragments that have mainly been the subject of immune defense studies in the past. By analyzing the structure of potent PG fragments, their impacts on various aspects of animal physiology, and the interacting host factors, we aim to uncover the mechanism of this fascinating new role of bacterial PG. In the other aspect, our effort in recent years has uncovered four novel regulatory systems that sense the deprivation of specific fatty acid and nucleotide variants to regulate developmental and behavioral events to protect animals? reproductive fitness. In particular, our study under the existing GM R01 grant uncovered an intestine-initiated pathway that regulates germ cell proliferation and metabolism in response to pyrimidine deficiency. Under this MIRA grant, we will address critical mechanistic questions surrounding the roles of an obscure endonuclease that increases its expression in response to nucleotide imbalance and that acts in the intestine to regulate metabolic and developmental events. Past research in the C. elegans field has indicated that this organism is best used to make novel discoveries that present important conceptual advances in biology. With promising preliminary data, the projects described in this MIRA application have great potential to make paradigm-shifting discoveries that would impact our understanding of the nutritional value of microbiota-produced molecules and the diversity of nutrient-sensing mechanisms.
The proposed study will take multiple genetic and biochemical approaches to tackle two novel nutrient-related problems that are related to human health. The first is to uncover the unexpected beneficial roles of metabolites from the bacterial cell wall to animal development and behaviors, as well as understand the underlying mechanism. The second is to uncover a gut-initiated pathway that senses the imbalance of nucleotides to regulate germ cell proliferation and nucleotide metabolism.