Treatment with glucokinase activator, YH-GKA, increases cell proliferation and decreases glucotoxic apoptosis in INS-1 cells

Abstract

Glucokinase (GK), an enzyme that phosphorylates glucose to form glucose-6-phosphate, has a role in regulating insulin secretion and proliferation in beta cells. GK activators (GKAs) have been developed as new therapies for type 2 diabetes. In this study, we evaluated the proliferation and anti-apoptotic actions of YH-GKA, a novel and potent GKA, in INS-1 pancreatic β-cells. YH-GKA treatment increased cell numbers at 3 mM glucose via upregulation of insulin receptor substrate-2 and subsequent activation of AKT/protein kinase B phosphorylation. YH-GKA also increased beta-catenin and cyclin D2 mRNA expression and inactivated GSK3β by increasing phosphorylation. These proliferative effects of YH-GKA were attenuated by IRS-2 downregulation. Moreover, YH-GKA reduced annexin-V-stained cells and expression levels of cleaved poly (ADP-ribose) polymerase and caspase-3 induced by glucotoxicity. YH-GKA inhibited apoptotic signaling via induction of ATP content, mitochondrial membrane potential, and citrate synthase activity and was correlated with changes of the mitochondrial function-related genes. YH-GKA also increased interaction between GK and voltage-dependent anion-selective channel protein. Our results suggest that the novel GKA, YH-GKA, promotes beta cell growth and prevents glucotoxic beta cell apoptosis. Therefore, YH-GKA may provide a therapy that compensates for beta cell loss in patients with type 2 diabetes.

Keywords: Apoptosis; B-cell lymphoma; Bax; Bcl; Bcl-2-associated X protein; Beta-cell proliferation; CS; GKA; GSK; Glucokinase activator; Glucotoxicity; INS-1 cells; IRS-2; PARP; PGC-1α; TFAM; Type 2 diabetes; VDAC; citrate synthase; glucokinase activator; glycogen synthase kinase; insulin receptor substrate-2; mitochondrial transcription factor A; mitochondrial transmembrane potential; peroxisome proliferator-activated receptor gamma coactivator 1-alpha; poly (ADP-ribose) polymerase; voltage-dependent anion-selective channel protein; ΔΨm.