KD025 Is a Casein Kinase 2 Inhibitor That Protects Against Glucolipotoxicity in ß-Cells.

Glucolipotoxicity (GLT), in which elevated levels of glucose and fatty acids have deleterious effects on ß-cell biology, is thought to be one of the major contributors in progression of type 2 diabetes. In search of novel small molecules that protect ß-cells against GLT, we previously discovered KD025, an inhibitor of Rho-associated coiled-coil-containing kinase isoform 2 (ROCK2), as a GLT-protective compound in INS-1E cells and dissociated human islets. To further understand the mechanism of action of KD025, we found that pharmacological and genetic inhibition of ROCK2 was not responsible for the protective effects of KD025 against GLT. Instead, kinase profiling revealed that KD025 potently inhibits catalytic subunits of casein kinase 2 (CK2), a constitutively active serine/threonine kinase. We experimentally verified that the inhibition of one of the catalytic subunits of casein kinase 2, CK2A1, but not CK2A2, improved cell viability when challenged with GLT. We conclude that KD025 inhibits CK2 to protect ß-cells from GLT.

Phenotypic Screening for Small Molecules that Protect ß-Cells from Glucolipotoxicity.

Type 2 diabetes is marked by progressive ß-cell failure, leading to loss of ß-cell mass. Increased levels of circulating glucose and free fatty acids associated with obesity lead to ß-cell glucolipotoxicity. There are currently no therapeutic options to address this facet of ß-cell loss in obese type 2 diabetes patients. To identify small molecules capable of protecting ß-cells, we performed a high-throughput screen of 20,876 compounds in the rat insulinoma cell line INS-1E in the presence of elevated glucose and palmitate. We found 312 glucolipotoxicity-protective small molecules (1.49% hit rate) capable of restoring INS-1E viability, and we focused on 17 with known biological targets. 16 of the 17 compounds were kinase inhibitors with activity against specific families including but not limited to cyclin-dependent kinases (CDK), PI-3 kinase (PI3K), Janus kinase (JAK), and Rho-associated kinase 2 (ROCK2). 7 of the 16 kinase inhibitors were PI3K inhibitors. Validation studies in dissociated human islets identified 10 of the 17 compounds, namely, KD025, ETP-45658, BMS-536924, AT-9283, PF-03814735, torin-2, AZD5438, CP-640186, ETP-46464, and GSK2126458 that reduced glucolipotoxicity-induced ß-cell death. These 10 compounds decreased markers of glucolipotoxicity including caspase activation, mitochondrial depolarization, and increased calcium flux. Together, these results provide a path forward toward identifying novel treatments to preserve ß-cell viability in the face of glucolipotoxicity.