Exercise training improves endothelial nitric oxide synthase (eNOS) dimerization in diabetic Goto‐Kakizaki (GK) rats

Abstract

eNOS is an enzyme that exists in both monomeric and dimeric conformations. The dimeric form catalyzes the rate-limiting step in the synthesis of nitric oxide, while the monomeric form catalyzes the synthesis of peroxynitrite (ONOO), a highly reactive oxidant species (ROS). An increase in the monomer form in the hearts of diabetic animals has previously been reported. Chronically elevated ROS exists with diabetes and may be a major underlying cause of many diabetic-related complications. Exercise has been useful in the management of diabetes. Although exercise-induced increased expression of eNOS has been reported, it is unclear if exercise may alter the functional coupling of eNOS. To investigate this question, Goto-Kakizaki (a model of type II diabetes) rats were randomly assigned to a 6-week running program (train) or sedentary (sed) groups. At the end of training, indices of glycemic control were determined prior to sacrifice, and tissues harvested for determination of eNOS conformation, using the low-temperature polyacrylamide gel electrophoresis (LT-PAGE) followed by western blot analysis. Exercise significantly (p<.05) increased plantaris cytochrome oxidase activity (sed: 0.31±0.02; train: 0.39±0.03 nmole/min/mg), and also significantly improved HbA1c (sed: 7.33±0.56%; train: 6.1±0.18%). Exercise increased both total eNOS expression and the ratio of dimer to total eNOS in both LV (sed: 6.4±2.7%; train: 24.8±5.3%) and kidney (sed: 12±2%; train: 20.7±3%). Exercise significantly improved the eNOS functional state; a shift that could serve to decrease diabetic-related oxidative stress and that may serve to lessen diabetic-related complications. Supported in part by NIH PO1HL43023 and the New York Medical College Research Endowment Fund.