This study evaluated the serum levels of vitamin C, UA and antioxidant condition in 44 angiographically-confirmed coronary artery stenosis patients and compared them with 44 controls. The findings revelaed that UA and vitamin C were significantly correlated to CAD while TAC and MDA showed no significant relationship with CAD.
Uric acid and CAD
Uric acid is the product of purine catabolism which can disturb the endothelial function of arteries and increase atherosclerosis by production of nitric oxide, proliferation of flat vascular muscles and increase of insulin resistance [14].
This study indicated that the mean uric acid level of the patients was higher than the healthy individuals (p<0.001) which is in line with the findings of Bagheri et al. [15]. According to Pearson correlation coefficient, the uric acid level had a direct relationship with the TAC (P<0.001). It however exhibited an inverse relationship with vitamin A (P=0.03) and zinc (P=0.004).
Although Framingham analysis and Aric study [16, 17] showed no relationship between the uric acid and CAD, numerous studies have reported a possible relationship between uric acid and emergence and severity of CAD [18-22].
Previous studies have reported the increased levels of uric acid in CAD patients.
Kim et al. investigated the relative risk of CAD with increase of blood UA in a meta-analysis on 26 cohort studies on about 400000 adults [23].
Ekici et al. (2015) showed that the serum level of UA is independently related to the severity and complexity of CAD [24].
In Iran, Goodarzinezhad et al. (2010) conducted an observational study in Tehran and showed the independent relationship of hyperuricemia with CAD only in men [25]. In some other studies, a significant relationship was observed in blood uric acid level and CAD just among women [26-28].
Despite these evidences and the complex relationship between uric acid and other known risk factors of CAD such as metabolic syndrome, obesity, diabetes and chronic renal disorders [29,30], it is not clear yet whether the elevated levels of uric acid is an independent risk factor or just a consequence or an index of CAD.
Vitamin C and CAD
Results of this study indicated that the mean serum level of vitamin C was significantly higher in healthy individuals compared to the patients. The vitamin intake of the patients was however higher than the healthy subjects while no significant difference was observed between the two groups in terms of vitamin E and A, beta-carotene, Zn and Se.
Better nutritional condition of the patients in this study could be due to higher dietary intake. As these people were aware of their disease, they might attempt to improve their condition by changing their diets.
Serdar et al. [31] and Delport et al. [32] showed the declined levels of plasma antioxidant (including vitamin A, C and E) in coronary artery stenosis patients.
Nojiri et al. studied the oxidative stress in coronary artery stenosis patients by evaluating the level of vitamin A, C and E as well as TAC in a case-control study. Their results indicated a decline in TAC and an increasein vitamin E [33].
Epidemiologic studies have revealed that treatment with antioxidants such as vitamin C and antioxidant-containing foods are related to decrease of inflammation markers and reduced risk of coronary hearth incidents [34, 35].
TAC and CAD
Increase of oxidative stress and defects in the antioxidant defense system plays a major role in endothelium function disorders and have been considered as the contributing factors in ateroscolisis progress [36].
Investigations on the relationship between the antioxidants and CAD are conflicting. In the present study, although the mean of TAC was higher in the patients group. This difference was not significant; hence it can’t be claimed that TAC is related to CAD. In a cross sectional study on 968 adults, no significant difference was observed in TAC and antioxidant enzymes activity of CAD group; uric acid and MDA were however increased in the CAD group [37].
In the work of Bagheri et al., CAD patients had higher UA and TAOC compared to the control group; their HDL chlestrol was however decreased. TAOC and its main factor (UA) were significantly associated with the prevalence and severity of CAD [15].
In a study by Gawron-Skarbek et al. [38], it was revealed that the CHD patients have higher levels of both TAC-FRAS and TAC-DPPH. In conterary, Khaki Khatibi et al. [39] showed that the TAC of the CAD patients is significantly lower than the healthy controls. One of the reasons for lack of significant relationship or increase of TAC in CAD patients could be due to the difference in the TAC measurment methods such as FRAP which is one of the causes of increase in UA level. Increase of UA level in CAD patients was reported in the previous studies.
MDA and CAD
MDA is the by-product of fatty acids oxidation with more than two double bonds. Enhanced lipid peroxidation and LDL oxidation are involved in CAD pathogenesis [40].
MDA was also measured. This study showed no significant difference in the plasma levels of MDA (as an index of lipid peroxidation) of the two groups. This is in line with the findings of Bagheri et al. [15]. Serdar et al. also reported enhanced levels of MDA in plasma and red blood cells in coronary artery stenosis patients [31].
Khaki Khatibi et al. [39] and Uppal et al. [41] also revealed the significant increase in MDA of the patients in comparison with the controls.
Lee et al. also indicated that MDA level of CAD patients was higher than the controls
Moreover, another study also reported an inceased level of plasma MDA among these patients [33,34].
The previous studies generally indicated a direct relationship between CAD and MDA.