Plasma antioxidants and lipid peroxidation in acute myocardial infarction and thrombolysis

A novel oxidative stress marker in acute myocardial infarction; thiol/disulphide homeostasis

BACKGROUND

The aim of this study was to investigate a novel oxidative stress marker (thiol/disulphide homeostasis) in patients with acute myocardial infarction (AMI) and compare the results with healthy controls for the first time in literature.

METHODS

A total of 450 participants including 300 patients with AMI and 150 healthy individuals were included in the study. Left ventricular ejection fraction, body mass index, peak troponin I levels, triglyceride, total cholesterol, low-density lipoprotein, high-density lipoprotein (HDL), native thiol, total thiol, and disulphide as well as disulphide/native thiol and disulphide/total thiol ratios were compared between the groups.

RESULTS

There were significant differences between AMI patients and the controls for left ventricular ejection fraction and troponin, HDL, native thiol, total thiol, and disulphide levels as well as disulphide/native thiol and disulphide/total thiol ratios (P < .05). Stepwise logistic regression model indicated that HDL (odds ratio [OR] = 0.923, P < .001) and disulphide levels (OR = 0.548, P < .001) and disulphide/total thiol ratio (OR = 0.356, P < .001) were significantly and independently related to AMI. The cutoff value of disulphide/total thiol ratio percentage on admission to predict AMI in all population was 4.3, with a sensitivity of 70% and a specificity of 69%.

CONCLUSION

Thiol/disulphide homeostasis may be used as a novel oxidative stress marker in patients with AMI because it is readily available, easily calculated, and relatively cheap. Further studies are needed to confirm the pathophysiologic role of thiol/disulphide homeostasis in AMI.

Lipid peroxidation and antioxidant vitamins prior to, during, and after correction of diabetic ketoacidosis

Oxidative stress plays an important role in the chronic complications of insulin-dependent diabetes mellitus (IDDM). Hyperketonemia, as well as hyperglycemia, is involved in the generation of oxygen-free radicals. We have studied the degree of oxidative stress in six patients before, during, and after correction of diabetic ketoacidosis (DKA) by determining the plasma ratios of C20 and C18 fatty acids to C16 fatty acids in the cholesteryl esters of the lipoproteins as well as in the plasma concentrations of the antioxidant vitamins A, C, and E. Lipid peroxidation was slightly increased prior to treatment. However, the C20/C16 ratio at 120 h was significantly decreased in comparison to the ratio at pretreatment (P<.025), at 6-8 h (P<.005), and at 24 h (P<.025). The C18/16 ratio at 120 h was also decreased in comparison to the ratio at 6-8 h (P<.025), indicating an increase in lipid peroxidation after correction of DKA. Vitamin A was below normal at pretreatment and was increased at 120 h (P<.05). Vitamin C was normal at pretreatment and decreased to low normal at 24 h (P<.005). Vitamin E was normal at pretreatment and decreased to below normal at 24 and 120 h, although the changes were not statistically significant. These data demonstrate that there is an increase in lipid peroxidation after the correction of DKA and therefore support the position that administering antioxidant vitamins during the treatment of DKA could be beneficial in minimizing oxidative stress and possibly both the acute and chronic complications of IDDM.

Antioxidant vitamins in the prevention of cardiovascular disease: a systematic review

Do antioxidant vitamins, in regular food or as food supplements, protect against myocardial infarction and stroke? In this systematic literature review on the effects of antioxidant vitamins in the primary prevention of cardiovascular disorders, studies with ischaemic heart disease, stroke or combined cardiovascular events as end-points have been included. Studies on the effects of antioxidant vitamins on intermediary end-points (such as blood lipids and blood pressure) and as secondary prevention in patients with manifest cardiovascular disease are reviewed in a conventional manner. In observational studies (case-control or cohort design), people with high intake of antioxidant vitamins by regular diet or as food supplements generally have a lower risk of myocardial infarction and stroke than people who are low-consumers of antioxidant vitamins. The associations in observation studies have been shown for carotene, ascorbic acid as well as tocopherol. In randomized controlled trials, however, antioxidant vitamins as food supplements have no beneficial effects in the primary prevention of myocardial infarction and stroke. Serious adverse events have been reported. After an initial enthusiasm for antioxidants in the secondary prevention of cardiovascular disease, recent reports from of several large randomized trials have failed to show any beneficial effects. Thus, the apparent beneficial results of high intake of antioxidant vitamins reported in observational studies have not been confirmed in large randomized trials. The discrepancy between different types of studies is probably explained by the fact that supplement use is a component in a cluster of healthy behaviour. Antioxidant vitamins as food supplements cannot be recommended in the primary or secondary prevention against cardiovascular disease.

Beta carotene: from biochemistry to clinical trials

Three large-scale clinical trials tested the effects of supplemental beta-carotene on the risk for chronic diseases such as cancer. The populations involved were Finnish male heavy smokers (the Alpha Tocopherol Beta Carotene [ATBC] trial), male asbestos workers and male and female heavy smokers (Beta-Carotene and Retinol Efficacy Trial [CARET]), and U.S. male physicians, 11% of whom were current smokers (Physician's Health Study). All three trials concluded that beta-carotene provided no protection against lung cancer; however, quite unexpectedly, two of the trials found a higher risk for lung cancer for those subjects given beta-carotene compared with those that were not. Several authors concluded from these beta-carotene trials that the protective effects of antioxidants against chronic disease are not as great as had been hoped. As reviewed here, however, beta-carotene may or may not be an antioxidant; it certainly differs in many respects from the prototypical antioxidant, vitamin E. In any case, the majority of beta-carotene's effects in vivo are probably not derived from any antioxidant properties that it may possess, but rather from its effect on a number of biochemical systems. Whether taking supplemental antioxidants can reduce the risk for chronic diseases remains to be established, although the case for vitamin E and heart disease appears strong. However, the association between eating a diet sufficient in fruits and vegetables and reduced risk for a number of diseases is consistent. There is no evidence at present that consuming small amounts of supplemental beta-carotene, i.e., amounts in foods or in a multivitamin tablet, is unwise for any population. The role of supplementation, however, particularly at high levels, with compounds that may be anti-oxidants but that are less well understood than vitamin E (e.g., carotenoids, plant polyphenols, and other phytochemicals), is less clear. The surprising results of the ATBC and CARET trials are a red flag, signaling the need for further research; a number of areas for future work are suggested here. Future research should lead to a clearer understanding of the effects of beta-carotene and other phytochemicals, as well as to more refined strategies for intervention, with important clinical and public health implications.

The state of lipid peroxidation and antioxidants following thrombolytic therapy with rt-PA and streptokinase in acute myocardial infarction

The role of reactive oxygen products in myocardial damage caused by ischemia-reperfusion has been established in a number of studies performed in animals models. However, studies showing the development of increased free radicals following effective myocardial reperfusion in humans are scarce. In the present study, both the increase of lipid peroxidation (LPO) following early stage thrombolytic therapy which is the current treatment issue performed after acute myocardial infarct (AMI) and the plasma levels of vitamin E and C (chain braker antioxidants) were investigated parallel to time. Forty patients with AMI who were admitted to hospital within six hours from the beginning of symptoms were included in the study and divided into two groups; group 1 (recombinant tissue-Plasminogen Activator, rt-PA group) and group 2 (streptokinase group). Serial serum specimens were drawn before and 30, 90 minutes and 24 hours after thrombolytic therapy for the investigation of LPO, vitamin E and C levels. Echocardiographic examination was performed on the tenth day to evaluate the functions of the left ventricle. Plasma levels of lipid peroxides (LPO) were found to increase 90 minutes after thrombolytic therapy in each group, while the levels of vitamins E and C showed significant decreases. The difference between the two groups was not significant. Similar to this finding, no significant difference in the ejection fraction values was observed between the groups. Further, no correlation was observed between the ejection fraction and LPO values at the 90th minute which is considered to be the time of successful thrombolysis. In conclusion, the occurrence of a series of biochemical changes confirming an increase in free radical development of peripheral blood was observed. Although the decrease in vitamin E and C levels suggests the need for supplementation of these vitamins along with the thrombolytic therapy, the fact that at least a week is needed for an increase of tissue levels of vitamin E confirms the opinion that the daily prophylactic doses of these vitamins is suitable for the decrease of AMI risk.