O-GlcNAcylation Involvement In Impairment Of Cardiomyocytes And Endothelial Cells Exposed In High Glucose

Diabetic cardiovascular disease is the most important cause of disabling and death in diabetic complications. Diabetic cardiomyopathy is defined as ventricular dysfunction occurring independently of a recognized cause, such as coronary artery disease or hypertension, which manifests as cardiac hypertrophy and subsequent heart failure. The lesion of myocardium occurs at the beginning and in the whole process of diabetes. The cardiac failure of end stage damages quality of life and increase mortality. Atherosclerosis in diabetes causes multiple ischemic events including stroke, myocardium infarction and lower extremity amputation. Angiogenesis and collateral vessel formation repair ischemic tissues and organs involved and improve prognosis. Diabetic complications of cardiovascular system act on wide range of organs and induced fatal consequences, therefore researchers kept enthusiasm on the mechanism of diabetic cardiovascular disease. Recent decade, increased hexosamine pathway and O-GlcNAcylation level induced by high glucose and subsequent oxidative stress attracted attention. The post-transcription modulation of proteins was shown mediated a seris of signaling transduction and physiology/pathology process. We aimed to disclose the role of O-GlcNAcylation induced by high glucose in diabetic cardiovascular disease, especially in cardiomyocytes and endothelial cells, and get a new sight and therapeutic target.Part Ⅰ O-GlcNAcylation Involvement in High Glucose-Induced Cardiomyocyte Hypertrophy via ERK1/2and Cyclin D2Continuous hyperglycemia is considered to be the most significant pathogenesis of diabetic cardiomyopathy, which manifests as cardiac hypertrophy and subsequent heart failure. O-GlcNAcylation has attracted attention as a post-translational protein modification in the past decade. The role of O-GlcNAcylation in high glucose-induced cardiomyocyte hypertrophy remains unclear. Therefore, we studied the effect of O-GlcNAcylation on neonatal rat cardiomyocytes (NRCMs) that were exposed to high glucose. High glucose (30mM) incubation for72hours induced a greater than2-fold increase in cell size and increased hypertrophy marker gene expression accompanied by elevated O-GlcNAcylation protein levels. High glucose increased ERK1/2but not p38MAPK or JNK activity, and cyclin D2expression was also increased. PUGNac, an inhibitor of β-N-acetylglucosaminidase, enhanced O-GlcNAcylation and imitated the effects of high glucose. OGT siRNA and ERK1/2inhibition with PD98059treatment blunted the hypertrophic response and cyclin D2upregulation. OGT inhibition also prevented ERK1/2activation. In conclusion, O-GlcNAcylation plays a role in high glucose-induced cardiac hypertrophy via ERK1/2and cyclin D2. Part Ⅱ Modification O-GlcNAcylation, ERK1/2and cyclin D2in myocardium of diabetic rats in early stageRat model of diabetes was induced by injecting streptozocin to confirm the effect of O-GlcNAcylation in diabetic cardiomyopathy. Pathological observation and protein and mRNA analysis of the cardium tissue from diabetic rats4weeks later indicated concentric hypertrophy of heart, hypertrophic cardiomyocytes, upregulated hypertrophic genes, accompanied by elevated O-GlcNAcylation protein levels, activated ERK1/2and increased expression of cyclin D2. The results supported the conclusion from cell culture study. Part Ⅲ O-GlcNAcylation Involvement in dysfunction of Human Umbilical Vein Endothelial Cells exposed to high glucoseHigh glucose inhibited angiogenesis in vivo and vitro which was based on proliferation and migration of endothelial cells. We observed proliferation and migration of human umbilical vein endothelial cells exposed to high glucose and effect of O-GlcNAcylation in the process. It was shown that high glucose inhibited the proliferation and migration, with was imitated by PUGNac and reverted by siRNA of OGT. Whereas activated ERK1/2and upregulated cyclin D2didn’t play a major role in the effect of high glucose on endothelial cells. Therefore, O-GlcNAcylation regulated the high glucose induced-dysfunction of endothelial cells, and the effect of activate EKR1/2and upregulated cyclin D2was covered.