Regulation of Vascular Smooth Muscle Cell Dysfunction Under Diabetic Conditions By miRNA-504

Diabetes promotes pro-atherogenic and pro-inflammatory phenotype of VSMC associated with vascular complications. Emerging evidence shows that miRNAs play key roles in VSMC, but their role in diabetes induced effects is unclear. We profiled novel diabetes induced miRNAs in VSMC from diabetic mice and examined their role in VSMC dysfunction. High throughput small RNA-sequencing identified 135 differentially expressed miRNAs in VSMC from type 2 diabetic db/db mice (db/dbVSMC) versus non-diabetic db/+ mice. Several of these miRNA were known to regulate VSMC functions. We further focused on miR-504, because it was highly upregulated in db/dbVSMC, but its function in VSMC is unknown. We demonstrated that miR-504 and its host gene Fgf13 were upregulated in VSMC and in vivo in aortas from db/db mice. Bioinformatics analysis predicted that miR-504 targets, including a signaling adaptor Grb10 and a transcription factor Egr2, could regulate growth factor signaling. We experimentally verified that miR-504 targets Grb10 and Egr2, and it enhanced ERK1/2 activation, proliferation and migration in VSMC. Silencing Grb10 by small interfering RNA also enhanced ERK1/2 activation, inflammatory gene expression and migration. Whereas, Egr2 silencing downregulated anti-inflammatory SOCS1 and increased inflammatory genes. Furthermore, treatment with high-glucose and palmitic acid upregulated miR-504, inhibited Grb10 and enhanced inflammatory genes in VSMC. Diabetes mis-regulates expression of several miRNAs including miR-504 involved in VSMC functions. Changes in miRNAs are sustained in non-diabetic conditions suggesting involvement of miRNA dependent mechanisms in metabolic memory implicated in vascular complications. Targeting such mechanisms could offer novel therapies strategies. Vascular smooth muscle cells (VSMC) were isolated from the thoracic aortas of 10-12 week old male type 2 diabetic db/db mice and control db/+ mice. Total RNA was extracted from VSMC cultures to profile differentially expressed miRNAs in VSMC from diabetic db/db mice versus control db/+ mice.