Serum Inducible and Endothelial Nitric Oxide Synthase in Coronary Artery Disease Patients with Type 2 Diabetes Mellitus

Objective: Coronary artery disease (CAD) is a well-known cause of morbidity and mortality in type 2 diabetes mellitus (T2DM). The role of endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) in T2DM patients in relation to CAD is not well understood. We examined serum inducible and endothelial nitric oxide synthase activities in patients with T2DM in relation to the presence of coronary artery disease.

Patients And Methods: The present study was conducted in the Department of Physiology, King Saud University, Riyadh, Saudi Arabia. Subjects were grouped into control (Group A, n=87), T2DM without CAD (Group B, n=70), and T2DM patients with CAD (Group C, n=49). The selection of T2DM subjects was according to the American Diabetes Association (ADA). Serum iNOS, eNOS, hsCRP, nitrates and nitrites along with lipid profile were compared between different groups. Spearman's correlation and ROC analysis were also performed.

Results: Serum eNOS levels were significantly high in the control group (112.38±47.16 U/ml) than in DM without CAD (81.43±49.91 U/ml) and DM with CAD (84.80±43.32 U/ml, p<.001). Serum iNOS levels were significantly higher in DM with CAD (42.87±28.83 U/ml) compared to both control (22.08±11.77 U/ml) and DM without CAD (16.24±12.30 U/ml, p<.001). Additionally, the differences in nitrite and NO were not significant between the three groups (34.06±24.75, 33.02±21.50, 38.83±24.34 uM, p = .384), and (56.51±36.78, 49.89±28.83 vs. 55.77±30.34 uM, p=.416) respectively. ROC curve analysis revealed a sensitivity and specificity of 73.5% and 68.6% of iNOS level at a cutoff point of 21.1 U/ml to predict CAD in T2DM patients. The ROC analysis for iNOS, eNOS, and hs-CRP were .782 (p<.001), .574 (p=.170), and .726 (p<.001), respectively.

Conclusions: Patients with T2DM have significantly higher levels of serum iNOS and lower levels of eNOS. However, iNOS levels were significantly higher in T2DM patients with concomitant CAD. Moreover, iNOS activity positively correlated with glycemic control and hsCRP. Therefore, iNOS could be an emerging future marker for CAD in T2DM patients and its antagonists could be useful in the management of these patients.