Elucidation of Intracellular Pathways Mediating Myricetin-induced Insulin Secretion in Pancreatic INS-1 β-cells

Abstract

Background: Myricetin (MyR), a bioflavonoid known for its broad therapeutic spectrum, has shown promising anti-diabetic potential, making it a viable candidate for managing Type 2 Diabetes Mellitus (T2DM). While numerous in-vitro and in-vivo studies support its role in glucose homeostasis, the precise molecular mechanisms underlying its action remain inadequately explored. Objective: To identify the intracellular signaling pathways involved in MyR-induced insulin secretion in INS-1 β-cells, with a focus on identifying key molecular effectors and their pharmacological modulation Methods: A rigorous experimental approach was used, incorporating the MTT assay (50,000 INS- 1 cells/well) to assess cell viability, and a static glucose-stimulated insulin secretion (GSIS) assay (100,000 INS-1 cells/well) under 2 mM and 20 mM glucose to quantify insulin secretion after exposure to MyR (5-160 μM). Pharmacological inhibitors, including H-89 (PKA inhibitor, 50μM), KN-62 (CaMKII inhibitor, 10 μM), GO6976 (PKC inhibitor, 1μM), U0126 (MEK inhibitor, 10 mM), Nifedipine (L-type VGCC blocker, 10 μM), EGTA (extracellular Ca²⁺chelator, 2 mM), and Diazoxide (K_ATP channel opener, 50 μM) were used to dissect the signaling pathways modulated by MyR. Results: MyR significantly enhanced insulin secretion in a glucose-dependent manner, with peaking at a non-toxic dose of 80 μM (7.652±0.3315% μg/100,000 INS-1cells/hour) in 20 mM glucose. Insulin secretion levels remained unchanged in the presence of L-type VGCC and K_ATP channel inhibitors, indicating that MyR’s insulinotropic effect is independent of these pathways. In contrast, the response was markedly reduced upon inhibition of PKA, CaMKII, PKC, and MEK pathways, indicating their pivotal roles in MyR-mediated β-cell signaling. Conclusions: MyR induces insulin secretion in a glucose-dependent manner and activating multiple kinase pathways. Further investigations using β-cells and animal models are warranted to fully elucidate the physiological relevance of these mechanisms. These insights could pave the way for uncovering MyR-based therapies that are both effective and affordable for managing T2DM.