Sialic acid and oxidizability of lipid and proteins and antioxidant status in patients with coronary artery disease Zehra Serdar 1 * ,z , Dilek Yes ¸ilbursa 2,z , Melahat Dirican 1,y , Emre Sarando ¨l 1,z and Akın Serdar 2,y 1 Biochemistry Department, Faculty of Medicine, Uludag ˘ University, Bursa, Turkey 2 Cardiology Department, Faculty of Medicine, Uludag ˘ University, Bursa, Turkey The aim of this study was to investigate the possible relationship between serum total sialic acid (TSA) concentration, recently shown to be a cardiovascular risk factor, and lipid and protein oxidation and antioxidant status and the severity of coronary artery disease (CAD) according to the obstructive vessel number in patients. The study was carried out on a total of 200 patients (142 men and 58 women) who were hospitalized for elective coronary angiographic evaluation with complaint of typical angina pectoris. According to the results of angiography, 150 patients had angiographically proven CAD (CAD group) and 50 patients had a history suggestive of angina pectoris but normal coronary angiograms (control group). The CAD group was further divided into single-, double- and triple-vessel disease groups according to the number of vessels involved. Lipid parameters were determined by routine laboratory methods. Plasma malondialdehyde (MDA) and vitamin E concentrations were determined by high-performance liquid chromatography. TSA and other oxidant and antioxidant parameters were studied spectrophotometrically. Our results demonstrated significant increases both in TSA levels and in indicators of oxidative stress in the patients with CAD compared with the controls. However, antioxidant parameters were decreased in the patients with CAD. We found strong positive correlations between TSA and plasma MDA, D-MDA which represents the degree of oxidative modification of apolipoprotein B-containing lipoproteins, serum protein carbonyls and apolipoprotein B and weak correlations between TSA and low density lipoprotein cholesterol, triacylglycerol, paraoxonase, glutathione peroxidase (GPx), vitamin C and vitamin E. In conclusion, TSA is related to markers of lipid and protein oxidation, paraoxonase and GPx activities, vitamin C and E levels and the severity of CAD. Copyright # 2006 John Wiley & Sons, Ltd. key words — coronary artery disease; total sialic acid; malondialdehyde; protein carbonyls; paraoxonase; vitamin C; vitamin E INTRODUCTION Sialic acids are located at the terminal ends of many carbohydrate chains of glycolipids and glycoproteins, including apolipoprotein B (apo B). The functions of sialic acids in biological systems include confor- mational stabilization, protease resistance, charge, cellular recognation, protein targeting and develop- mental regulation. 1 Recently, interest has grown concerning the role of sialic acids in the pathogenesis of coronary artery disease (CAD) and elevated serum total sialic acid (TSA) concentration has been shown to be a cardiovascular risk factor. 2,3 Although it has been reported that serum levels of sialic acid are elevated in patients with CAD, the reason for this elevation remains obscure. 2–4 Some authors suggest that serum TSA reflects the degree of atherosclerotic progress and that serial measurements of serum TSA levels may be a useful indicator of the progression of CAD. 5,6 In contrast, Salomone et al. 7 and Wu et al. 8 demonstrated that there was no association between the severity of cell biochemistry and function Cell Biochem Funct 2007; 25: 655–664. Published online 27 September 2006 in Wiley InterScience (www.interscience.wiley.com) DOI: 10.1027/cbf.1369 * Correspondence to: Z. Serdar, Biochemistry Department, Faculty of Medicine, Uludag ˘ University, 16059, Bursa, Turkey. Tel: þ90 224 442 82 00/1310. Fax: þ 90 224 442 88 66. E-mail: zserdar@uludag.edu.tr y Professor. z Associate Professor. Copyright # 2006 John Wiley & Sons, Ltd. Received 3 April 2006 Revised 19 June 2006 Accepted 17 July 2006