Increased NADH oxidase activity in the retina of the BBZ/Wor diabetic rat.

This morphological study demonstrates a role for endothelial cells in generating reactive oxygen species in early stages of retinopathy in the BBZ/Wor rat, an obese, noninsulin dependent model of diabetes. Hyperglycemia induced pseudohypoxia results in an imbalance in cytosolic NADH/NAD+. In the oxygen-rich environment of the retina, NADH oxidase generates superoxide radical which is dismutated to hydrogen peroxide. Localization of hydrogen peroxide by the cerium NADH oxidase enzyme activity cytochemical localization technique shows a statistically significant increase of peroxide localization in the central retina of diabetic rats as compared to age-matched, nondiabetic controls. Endothelial cell dysfunction, indicated by leakage of endogenous serum albumin, coincided with areas of NADH oxidase activity localization. In diabetic rats there are increased levels of fibronectin in areas of hydrogen peroxide localization. This in vivo, morphological study is the first demonstration of oxidative injury and endothelial cell dysfunction in the retina of a spontaneous, noninsulin dependent model of diabetes.

Pioglitazone: in vitro effects on rat hepatoma cells and in vivo liver hypertrophy in KKAy mice.

Pioglitazone increases insulin sensitivity in vivo and in vitro. The effects of this agent on insulin-induced DNA synthesis and hepatic cell growth have not been determined. We examined the ability of pioglitazone to enhance basal and insulin-stimulated DNA synthesis in rat H4IIE (H4) hepatoma cells, and to alter liver weight and histology in diabetic KKAy mice. Treatment of H4 cells with increasing concentrations of pioglitazone for 30 h increased basal DNA synthesis 1.6- to 1.8-fold. With pioglitazone pretreatment and submaximal insulin concentrations, DNA synthesis was significantly increased from 2.1-fold (insulin 10(-12) mol/l alone) to 3.9-fold (insulin 10(-12) mol/l + pioglitazone 10(-6) mol/l). At maximal concentrations of insulin, the enhancement of DNA synthesis increased from 7.4-fold (insulin 10(-8) mol/l alone) to 16.2-fold (insulin 10(-8) mol/l + pioglitazone 10(-6) mol/l). Glyburide did not increase basal or insulin-stimulated DNA synthesis. In diabetic KKAy mice, serum glucose levels decreased and body weight, liver weight and liver weight as a percentage of body weight increased following pioglitazone treatment. Histological studies demonstrated marked hepatocyte distension. Our findings suggest that pioglitazone acts as an insulin sensitizer in rat hepatoma cells, increasing basal and insulin-stimulated DNA synthesis, and stimulating fat synthesis and liver hypertrophy in diabetic KKAy mice.