Epigenetic determinants of beta cell development and function

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PROJECT SUMMARY/ABSTRACT Insulin produced by pancreatic β-cells is the key stimulus for glucose metabolism, and therefore it is critical that insulin secretion is adjusted to changes in energy state. Insulin secretion is acutely regulated by nutrients and hormones that change in response to feeding. If the fed state persists, as in overnutrition, adaptive control mechanisms increasingly sensitize the insulin secretory response to meet the increased insulin demand. However, long-term overnutrition can also become maladaptive and lead to β-cell failure and type 2 diabetes (T2D). How β-cells read nutrient signals and translate these signals into adaptive and maladaptive responses is poorly understood. Supported by this grant, we have shown that the nutrient-sensitive histone demethylase LSD1 mediates nutrient-induced changes to the β-cell epigenome to regulate adaptative insulin secretion. Specifically, we found that LSD1 modifies the epigenetic state of gene regulatory elements linked to β-cell nutrient response genes, thereby modulating the amplitude of the insulin secretory response. Thus, LSD1 functions as an integration hub between the β-cell’s nutrient environment, the epigenome and transcriptional output. Our preliminary studies further show that LSD1 inhibition is adaptive in a lean state, but becomes maladaptive and promotes β-cell failure in obesity. The objective of this proposal is to determine the mechanisms by which LSD1 senses nutrients and to gain insight into how metabolic cues converge on LSD1 and the epigenome to render the adaptive β-cell response maladaptive. We will employ state-of-the-art approaches, encompassing novel mouse models, human islet experiments, single cell resolved mapping of chromatin state and gene expression, and cutting-edge computational analyses. In Aim 1, we will determine how LSD1 senses nutrients and regulates chromatin state in β-cells. To investigate the nutrient sensing mechanism, we will manipulate LSD1’s metabolically regulated co-factor FAD and measure effects on LSD1- regulated processes in β-cells. Furthermore, we will dissect LSD1’s enzymatic and non-enzymatic functions in regulating the β-cell epigenome, using novel mouse models and in vitro experiments. In Aim 2, we will identify mechanisms by which LSD1 inhibition triggers maladaptive processes that accelerate β-cell decompensation in T2D. Employing genetic mouse and islet models of metabolic stress, we will manipulate LSD1 activity and study how these manipulations affect β-cell chromatin state, gene expression, and phenotypes. In Aim 3, we will examine the role of LSD1 in human β-cells. Here, we will leverage transcriptomic and chromatin maps we generated from a collection of nondiabetic, prediabetic, and T2D donor islets to determine whether the LSD1- regulated program contributes to β-cell failure in T2D. By unveiling fundamental mechanisms by which β-cells interpret nutrient signals, this proposal will prove critical for identifying strategies to prevent or reverse maladaptive processes and β-cell failure.