Thiol-related genes in diabetic complications - A novel protective role for endogenous thioredoxin 2

Objective - Our laboratory and others have found that deficiencies in cellular thiols may be importantly involved in the development of diabetic complications. However, the role for specific thiol-related genes in diabetic complications is unclear. Methods and Results - We began the present study by systematically determining the expression level of 11 thiol- related genes in three tissues from rats with streptozotocin- induced diabetes. Several thiol- related genes were found to exhibit diabetes- associated, time- dependent differential expression. Thioredoxin 2, a mitochondrion- specific thioredoxin whose role in diabetes was unknown, was suppressed in the aorta from rats with two weeks of diabetes. When thioredoxin 2 expression in human umbilical vein endothelial cells was knocked- down by small interfering RNA, high- ambient glucose- elicited substantial injurious effects (n = 5 to 9, P < 0.05), including increases in cytosolic cytochrome c (by 2.2 +/- 0.6- fold), lipid peroxidation (by 40 +/- 8%), fibronectin expression (by 35 +/- 7%), and oxidized glutathione, and decreases in endothelial nitric oxide synthase expression (by 79 +/- 15%), basal accumulation of nitrite/nitrate (by 68 +/- 16%), total free thiols ( by 42 +/- 8%), and glutathione ( by 6 +/- 1%). In the absence of thioredoxin 2 knockdown, high- ambient glucose did not have significant effects on any of these measurements. The effect of thioredoxin 2 knockdown appeared to be associated with increases in glucose consumption and glucose transporter 1 expression. Conclusion - These results provided the first expression profile of thiol- related genes in a model of diabetes and demonstrated a novel role for endogenous thioredoxin 2 in protecting cells against high ambient glucose.