The injurious effect of hyperglycemia has been attributed to biochemical consequences of intracellular metabolism of excess glucose. HIF-1alfa switches the glucose metabolism from oxidative phosphorylation to glycolysis under both hypoxic and normoxic (Warburg effect) conditions. Metabolic changes resembling the Warburg effect also occur in the process of inflammation. However, the role of HIF1-alfa in high glucose (HG)-mediated endothelial and macrophage cell activation is unknown. We have shown that Carnosine (CAR) protects from experimental diabetic atherosclerosis and prevents the associated increase of HIF-1alfa expression in the aorta. This project is aimed at investigating: 1) the role of HIF-1alfa in endothelial (HUVEC) and monocyte/macrophage (HMac) cell dysfunction induced by HG and the protective effect of CAR through modulation of HIF-1alfa activity; 2) the molecular processes driving HG-mediated HIF-1alfa induction, modification in cell energetics, and the protection provided by CAR; 3) the relevance of HIF-1alfa in human pathology by ex vivo studies. By means of loss of function studies and transfection for reporter gene assay, we will evaluate the effects of HG and methyglyoxal (MGO), a toxic by product of glycolysis, on HIF-1alfa regulation, changes in cell glucose metabolism and markers of cell activation and inflammation in HUVEC and HMac cells. Moreover we will investigate the effects of CAR in the prevention of HIF-1alfa induction by HG. mRNA and protein levels of HIF-1alfa will be also evaluated in monocytes and carotid endarterectomy from diabetic and non-diabetic subjects. This study deals with a novel mechanistic link between the toxic by-products of glycolysis and HIF-1alfa induction, which would provide new explanation for the changes in cell energetics induced by the diabetic milieu in vascular cells and has the potential to provide a novel paradigm and therapeutic opportunity for the prevention and treatment of diabetic atherosclerosis.
Biochemical mechanisms of hyperglycaemic injury are potential targets for novel therapeutic intervention aimed at reducing glucose toxicity, which is decreased but not completely prevented by current glucose-lowering treatment strategies. This research project investigates a novel mechanistic link between the toxic by-products of glycolysis alfa-oxoaldehydes and HIF-1alfa induction, providing new explanation for the changes in glucose energy metabolism induced by the diabetic milieu in endothelial and monocyte/macrophage cells, i.e., the main cell type involved in the initiation of atherosclerosis. Moreover, we postulate that carnosine, which has been shown to be highly effective in preventing diabetes-associated atherosclerosis and HIF-1alfa upregulation, might help to protect from these biochemical changes by trapping the toxic glucose metabolites of glycolysis, thus preventing HIF-1alfa induction and consequent alterations in cell energetics. Development of therapeutic strategies capable of protecting vascular cells from abnormalities in cell glucose metabolism caused by hyperglycemia may abate residual long-term glucose toxicity resulting from insufficient glycaemic control.
In more detail, the role of HIF1-alfa in the initiation and promotion of endothelial cell dysfunction and macrophage activation triggered by hyperglycemia is not known; in particular, it is unknown if, and through which mechanism(s), HIF1-alfa participates in the alterations in intracellular glucose metabolism induced by the diabetic milieu. Moreover, there is no evidence in the literature to demonstrate a direct effect of carnosine on the regulation of intracellular glucose metabolism in endothelial and inflammatory cells exposed to high glucose levels. Information about this potential effect of carnosine may contribute to identify a novel molecular mechanism (i.e., preservation of a normal cell glucose metabolism through modulation of HIF-1alfa activity), underlying the protection provided by this agent against the unfavorable cell response to high glucose levels.
In conclusion, this study deals with a novel mechanistic link between the toxic by-products of glycolysis and HIF-1alfa induction, which would provide new explanation for the changes in cell energetics induced by the diabetic milieu in endothelial and monocyte/macrophage cells. Therefore, this study has the potential to provide a novel paradigm and therapeutic opportunity for the prevention and treatment of diabetic atherosclerosis.