368-OR: Activation of a Yap1-Dependent Mesenchymal Program Promotes ß-Cell Failure

Abstract

A critical contributor to the pathogenesis of type 2 diabetes is the failure of insulin-secreting β-cells due to loss of cell number or identity. However, the signaling pathways that trigger these events remain unclear. While β-cells are of endodermal origin, recent studies show endocrine cells that coexpress the mesenchymal marker vimentin in the pancreas with diabetes, although the functional features of these cells are not known. Here, we identify an epithelial-to-mesenchymal (EMT) -like program that is activated in islets of mice and humans with type 2 diabetes. Characteristics of this EMT-like program include increased protein and mRNA abundance of the EMT transcription factor Snail and the mesenchymal adhesion molecule N-cadherin. Lineage-tracing techniques demonstrate that this mesenchymal program is initiated in β-cells that become multi-hormonal, a hallmark of dysfunctional endocrine cells. Interestingly, EMT-like cells minimally express Aldh1a3, a marker of dedifferentiated β-cells. To determine the mechanism driving EMT-like activation in β-cells, we tested stressors that phenocopy the effects of diabetes in islets. Treatment of islets with mitochondrial decouplers as well as oxidative stress increased expression of EMT markers. The transcription factor Yap1 is a known inducer of EMT. While Yap1 is expressed at minimal levels in β-cells, its abundance increased in db/db islets and in primary cells with impaired mitochondrial function. Importantly, chemical inhibition of Yap1 in db/db islets reversed activation of EMT-like factors. Yap1 inhibition also improved insulin secretion. Taken together, we found activation of an EMT-like program in the endocrine pancreas of mice and humans with type 2 diabetes. This program is dependent on increases in Yap1 due to oxidative stress and impaired mitochondrial function, and results in disrupted β-cell function. Disclosure W.Mckimpson: n/a. N.Hoque: None. J.Son: None. A.Y.Lee: None. D.Accili: Advisory Panel; Lilly Diabetes. Funding NIDDK (1K01DK121873)