We recently discovered that pancreatic beta-cells express a signaling system complementary to the traditional glucose-induced metabolic pathway that participates in the stimulation of insulin release. Taste receptors (TRs) and their signaling machinery that are traditionally involved in taste perception on the tongue are also expressed in pancreatic islets. We found that TR agonists stimulate insulin secretion in primary pancreatic islets, and that these responses can be blocked using antagonists and knock out strategies targeting TR signaling components. This proposal addresses the physiological relevance of these findings. We hypothesize that the TR machinery in beta-cells is an important sensory system that modulates insulin secretion in response to ingested nutrients, such as monosaccharides and amino acids. We propose that TR signaling in beta-cells contributes to postprandial glucose homeostasis by modulating the effects of glucose-stimulated insulin secretion (GSIS). Our experimental plan evaluates the role of TRs in beta-cells, and elucidates the downstream signaling pathway induced by physiological TR agonists. We will use T1R3 knock out (KO) mice to investigate the role of TRs in the regulation of insulin secretion in vitro and glucose homeostasis in vivo. We will compare in vitro GSIS between wild type and T1R3 KO islets in static and perifusion experiments, and assess the in vivo metabolic phenotype of T1R3 KO mice subjected to beta-cell stress. We will also identify postprandial sweet taste nutrients that act through TRs to potentiate insulin release. Finally, we will elucidate the TR signaling pathway by evaluating the activation of PLC using a PLC-biosensor (PHPLC4-GFP), and analyze dynamic changes in ER calcium using a specific ER calcium biosensor (D1ER cameleon). Results from these studies will greatly enhance our understanding of the regulation of insulin release and confirm a novel regulatory pathway mediated by TRs present in beta-cells.
Type 2 diabetes involves the failure of pancreatic beta-cells to secrete insulin. Any mechanism that regulates insulin release is likely to prevent or delay the chronic complications of diabetes. We have shown that nutrients activate taste receptors present in beta-cells and synergize with glucose to stimulate insulin secretion. The proposed studies will increase our understanding of novel pathways that modulate insulin secretion and unveil potential therapeutic targets for the management of type 2 diabetes.
|Kyriazis, George A; Smith, Kathleen R; Tyrberg, BjÃ¶rn et al. (2014) Sweet taste receptors regulate basal insulin secretion and contribute to compensatory insulin hypersecretion during the development of diabetes in male mice. Endocrinology 155:2112-21|
|Kyriazis, George A; Soundarapandian, Mangala M; Tyrberg, Bjorn (2012) Sweet taste receptor signaling in beta cells mediates fructose-induced potentiation of glucose-stimulated insulin secretion. Proc Natl Acad Sci U S A 109:E524-32|