The long range goal of my research program is to elucidate the pathogenesis of the late complications of diabetes. Several lines of evidence indicate that many, if not all, of the metabolic imbalances currently linked to early vascular and neural complications of diabetes either contribute to or are the consequence of glucose-induced metabolic hypoxia (""""""""hyperglycemic hypoxia""""""""), i.e., an increase in the ratio of NADH/NAD+ despite normal tissue p02. Previous studies have established that increased oxidation of sorbitol to fructose, which is coupled to reduction of NAD+ to NADH, is associated with an increased ratio of lactate/pyruvate (a reliable parameter of the cytosolic ratio of NADH/NAD+) and increased blood flow and vascular permeability. These redox changes and vascular dysfunction are similar to corresponding changes in ischemic/hypoxic myocardium and to redox and vascular changes associated with cyanide poisoning. Several lines of evidence support the hypothesis that these redox changes may initiate increased synthesis of nitric oxide (NO), a potent vasodilator, which could mediate the vascular dysfunction associated with all three of these conditions.
The specific aims of the experiments outlined in this proposal are to: (1) elucidate the role of increased NO production the pathogenesis of diabetic complications, (2) assess the effects of aminoguanidine, a newly discovered novel inhibitor of NO synthase, on metabolism of glucose via glycolysis and the sorbitol pathway, and (3) investigate the effects of elevated glucose levels and sorbitol pathway metabolism on NO synthesis from L-arginine. No synthase activity in cell free extracts and in tissues incubated in vitro will be monitored by the conversion of L- [guanidino14 C]-arginine to L-citrulline, measurement of cGMP levels, and measurement of NO2 (an oxidation product of NO). The potential significance of this research is that the insights it may provide regarding the pathogenesis of late complications of diabetes may contribute to the development of new approaches for the prevention and treatment of diabetic complications.
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