The relation of serum thiol levels and thiol/disulphide homeostasis with the severity of coronary artery disease

Background: The balance of oxidant and antioxidant status plays a key role in the coronary artery diseases (CAD). Thiol is one of the most important antioxidant barriers in humans, and thiol/disulphide homeostasis is a novel oxidative stress marker. Aim: We aimed to investigate the relation of serum thiol levels and thiol/disulphide homeostasis with the presence and severity of CAD. Methods: A total of 161 patients who underwent coronary angiography owing to stable angina pectoris were consecutively enrolled. They were divided into three groups. Group I - 47 age- and gender-matched subjects with normal coronary angiography (control); group II - 71 newly diagnosed CAD patients with noncritical stenosis; and group III - 43 newly diagnosed CAD patients with critical stenosis. Serum native thiol, total thiol, and disulphide levels were measured, and disulphide/thiol ratios were calculated. Gensini scores were calculated in CAD patients. Results: While the highest thiol levels were found in group I, the lowest one was observed in group III (p < 0.001). Total and native thiol levels were significantly lower in group II than in group I (p < 0.001 for each), but they increased considerably in group II compared with group III (p = 0.031 and p = 0.028, respectively). Disulphide levels decreased in group II and III compared with group I (p < 0.001 for each). No statistically significant changes were observed in disulphide/thiol ratios (p > 0.05). Gensini scores were negatively correlated with total and native thiols, and positively with age and dyslipidaemia. Stepwise linear regression analyses showed that native thiol was an independent predictor in the final model for Gensini score. Receiver operating characteristic curve analysis demonstrated that thiol values of 310.7 or below could predict CAD with 89% sensitivity and 85% specificity (AUC = 0.918; 95% CI 0.870-0.965). Conclusions: While the disulphide/thiol ratio did not change significantly, decreased native thiol levels were associated with the presence and severity of CAD. This result indicates that the reduction of thiols may be an important factor in the development of CAD.