Targeting PGC-1α by miRNA-374 Simultaneously Improve β-Cell Dysfunction and Suppress Hepatic Glucose Overproduction

In this study, we aimed to validate the potential of miR-374 in ameliorating hyperglycemia by regulating peroxisome proliferator-activated receptor γ coactivator-1 (PGC-1α) expression in pancreatic islets and liver.

To identify miRNAs targeting PGC-1α, we performed miRNA chip analysis in rat islets under hyperglycemic and euglycemic conditions. Luciferase reporter assay was performed to identify miR binding sites in the 3'-untranslated region (3' UTR) of PGC-1α. In db/db mice, miRNA-encapsulated adenoviruses were administered and intraperitoneal glucose tolerance test and glucose stimulated insulin secretion tests were performed. For enhanced delivery to β-cells, we developed exendin-4 (Ex-4) coated cationic lipoparticles (CCLs) encapsulating miRNAs. The therapeutic potential of Ex-4-CCL-miRNA was further evaluated in insulin-producing cells derived from induced pluripotent stem cells.

By analyzing miRNA expression in primary rat islets exposed under hyperglycemic environment, we identified miR-374 as a potential target. In vitro experiments confirmed that miR-374 significantly suppressed PGC-1α expression in β-cells and hepatocytes by binding to its 3'-UTR. In vivo experiments using adenovirus-mediated miR-374 (Ad-miR-374) delivering directly to the pancreas and liver of db/db mice demonstrated improved glycemic control, enhanced insulin secretion, and downregulated hepatic gluconeogenesis-related genes (G6Pase, Pepck, PC). To enhance the clinical applicability of miR-374, we developed Ex-4-CCLs. Ex-4-CCL-miR-374 successfully alleviated hyperglycemia, restored pancreatic islet function, and decreased gluconeogenesis gene expression in db/db mice. Furthermore, Ex-4-CCL-miR-374 improved insulin secretory function in glucotoxicity-exposed human induced pluripotent stem cell-derived insulin producing cells.

Based on these findings, we propose that Ex-4-CCL-miR-374 as a promising therapeutic approach to reverse β-cell dysfunction and improve hepatic insulin resistance in type 2 diabetes mellitus.