In vitro and in vivo pimonidazole labelling of glucose-induced hypoxia in beta-cells

Details

Supervisors

Jonas, Jean-Christophe

Degree label

Master en Sciences Pharmaceutiques

Abstract

Pancreatic beta-ceils synthesize and secrete insulin in response to a rise in plasma glucose levels to maintain glucose homeostasis of the organism. Glucose is the main physiological regulator of beta-cell function. However, prolonged exposure to high glucose levels both in vitro and in vivo induce the loss of beta-ceil differentiation, alter the stimulus-secretion coupling, and increase the rate of beta-cell apoptosis, a concept known as “glucotoxicity”. Nevertheless, the molecular mechanisms underlying the latter are not fully understood. Based on a previous study in the laboratory showning that glycolytic genes and other hypoxia-response genes are induced by high glucose in rat islets, as well as previous observation that glucose stimulation increased oxygen consumption in beta-cells, the propose of my thesis was to test whether these changes in gene expression resulted from high glucose-induced beta-cell hypoxia using the hypoxia marker pimonidazole. I have shown by western blot analysis that glucose in a concentration-dependent manner increased pimonidazole protein adducts formation in rat islets and INS 1 cells. Immunohistochemistry on rat islet sections revealed that pimonidazole-protein adducts staining was heterogeneous. Finally, we observed increased HIF1a and pimonidazole-protein adducts staining in few islet cells of diabetic Leprdb/db mice. These results suggest that high glucose-induced beta-ceil hypoxia may be an important mechanism that contributes to the deterioration of the beta celi phenotype under prolonged hyperglycemia.