Loss of glucose-stimulated β-cell Nr4a1 expression impairs insulin secretion and glucose homeostasis.

Abstract

A central aspect of type 2 diabetes is decreased functional β-cell mass. The orphan nuclear receptor Nr4a1 is critical for fuel utilization, but little is known regarding its regulation and function in the β-cell. Nr4a1 expression is decreased in type 2 diabetes rodent β-cells and type 2 diabetes patient islets. We have shown that Nr4a1-deficient mice have reduced β-cell mass and that Nr4a1 knockdown impairs glucose-stimulated insulin secretion (GSIS) in INS-1 832/13 β-cells. Here, we demonstrate that glucose concentration directly regulates β-cell Nr4a1 expression. We show that 11 mM glucose increases Nr4a1 expression in INS-1 832/13 β-cells and primary mouse islets. We show that glucose functions through the cAMP/PKA/CREB pathway to regulate Nr4a1 mRNA and protein expression. Using Nr4a1^-/- animals, we show that Nr4a1 is necessary for GSIS and systemic glucose handling. Using RNA-seq, we define Nr4a1-regulated pathways in response to glucose in the mouse islet, including Glut2 expression. Our data suggest that Nr4a1 plays a critical role in the β-cells response to the fed state.NEW & NOTEWORTHY Nr4a1 has a key role in fuel metabolism and β-cell function, but its exact role is unclear. Nr4a1 expression is regulated by glucose concentration using cAMP/PKA/CREB pathway. Nr4a1 regulates Glut2, Ndufa4, Ins1, In2, Sdhb, and Idh3g expression in response to glucose treatment. These results suggest that Nr4a1 is necessary for proper insulin secretion both through glucose uptake and metabolism machinery.