Effects of Oral Antioxidant Cocktail in Cardiovascular Disease Patients

Overview

Title: Effects of oral antioxidant cocktail on vascular function and muscle function in cardiovascular disease patients Cardiovascular disease (CVD) generally refers to various conditions involving narrowed or blocked dysfunctional blood vessels that often lead to heart attack or stroke. One of the main contributors to blood vessel dysfunction is damage to the vascular endothelium. This often results from the accumulation of oxidative stress (OS) and inflammation due to a decrease in blood flow and oxygen transport to the body's organs and skeletal muscle. The body's natural antioxidant defense system cannot keep up with the high level of OS clearance necessary to maintain proper vascular homeostasis. Previous research has addressed the use of single antioxidants (e.g. vitamin E, beta-carotene, ascorbic acid) in CVD patients, but the use of a combination of antioxidants has yet to be examined. Therefore, the purpose of this study is to examine the effects of acute oral antioxidant cocktail administration (containing vitamin C, E, and alpha-lipoic acid) on oxidative stress, vascular function, autonomic function (heart rate variability), leg blood flow, leg muscle tissue oxygenation, and walking capacity in CVD patients. This is a parallel study design that will assess the effects of oral antioxidant cocktail administration on CVD patients ages 50-85. Subjects will be required to visit the lab 1 time. This visit will consist of 1) obtaining informed consent and questions, 2) baseline blood sampling and baseline measurements of endothelial function, arterial stiffness, autonomic function (heart rate variability), leg blood flow, leg muscle oxygenation, and a walking test, 3) first dose oral antioxidant cocktail administration followed by a 2-hour break, 4) second dose oral antioxidant cocktail 30 minutes after the first dose, 5) post-consumption blood sampling and measurements of endothelial function, arterial stiffness, autonomic function (heart rate variability), leg blood flow, leg muscle oxygenation, and a walking test.

Cardiovascular disease (CVD) is one of the leading causes of death in the United States. CVD is attributed to a combination of major risk factors including hypertension, dyslipidemia, obesity, poor diet, low physical activity levels, and vascular endothelial cell dysfunction. The vascular endothelial cells (VECs) have significant control over vascular homeostatic regulation. In the case of mechanical and chemical stimuli, VECs can release vasoactive substances to regulate vascular tone, cell adhesion, and vascular smooth muscle cell (VSMC) proliferation. When the endothelium is damaged and becomes dysfunctional, atherosclerotic changes take place that can contribute to the development of CVD and atherosclerosis. Endothelial dysfunction has been partially attributed to high levels of reactive oxygen species (ROS) causing significant oxidative stress (OS). OS is defined as an imbalance between the rate of ROS production and the rate of ROS clearance by the antioxidant defense system, with insufficient clearance leading to oxidative damage of the vasculature. High levels of OS have been shown to negatively affect the vascular endothelium by increasing VSMC proliferation and inflammation, which may result in vascular remodeling. Increased OS also attenuates the bioavailability of nitric oxide, a potent vasodilator, and can further exacerbate the structural and functional changes of the vascular endothelium that are associated with the development of CVD. When the vascular endothelium becomes dysfunctional (partially due to OS), blood flow and vascular tone regulation become impaired, which then negatively affects O2 transport. Without proper blood flow and O2 transport, exercise capacity becomes attenuated. This is a major concern for CVD patients, because exercise is an effective non-pharmacological therapeutic treatment for many of the CVD risk factors including obesity, dyslipidemia, hypertension, and metabolic syndrome. Therefore, improvement of the antioxidant defense system could alleviate high OS, and improve vasodilatory capacity of blood vessels, blood flow and O2 transport, and by extension, can increase exercise capacity. This would make exercise a more viable treatment option for CVD patients. The antioxidant defense system contains numerous enzymatic and non-enzymatic antioxidants, including catalase, superoxide dismutase, glutathione peroxidase, vitamins A, E, and C, along with glutathione, ubiquinone, and flavanoids. The antioxidant defense system has been found to be attenuated in CVD patients, particularly in those with peripheral arterial disease. However, as ROS production increases, this antioxidant defense system can be overwhelmed, leading to OS and damage to the tissues. Antioxidant capacity may be improved through supplementation in order to provide better OS clearance in the body, which could then result in better blood flow and O2 delivery to the muscles and other organs in the body. Previous research has shown that blood flow increases after antioxidant intake. Leg blood flow increased significantly in chronic obstructive pulmonary disease (COPD) patients during knee extension exercise in watts (W) in comparison to healthy age-matched controls (3W: 1,798±128 vs. 1,604±100 mL/min, 6W: 1,992±120 vs. 1,832±109 mL/min, 9W: 2,187±136 vs. 2,035±114 mL/min, P \< 0.05, antioxidant supplement vs. control, respectively) following acute antioxidant supplementation (\~2 hours prior). In patients with open-angle glaucoma, antioxidant supplementation for one month significantly increased biomarkers of ocular blood flow within the retina and retrobulbar vascular beds, where peak systolic velocity increased by 7.3% (P=0.013) and end diastolic velocity increased by 11% (P=0.014). Cerebral blood flow has also been shown to increase following 12 weeks of antioxidant supplementation. Overall, the use of antioxidant intake, acute and chronic, has shown to improve blood flow to various areas within the vasculature. Previous research also indicates that the increase in blood flow is indicative of greater O2 supply to the measured area. During knee extension exercise in COPD patients, leg O2 consumption increased significantly in comparison to age-matched controls following acute antioxidant intake (3W: 210±15 vs. 173 ± 12 mL O2/min, 6W: 237±15 vs. 217±14 mL O2/min, 9W: 260±18 mL vs. 244±16 mL O2/min, P\< 0.05, antioxidant supplement vs. control, respectively). Following 12 weeks of antioxidant use, oxygen utilization in the right prefrontal cortex increased and was strongly associated with the increase in cerebral blood flow (SO2, from 68.21±1.65% to 66.58±1.58%, P=0.001, pre vs. post, respectively). Pharmacological interventions are often aimed toward controlling cholesterol and blood pressure; however, OS reduction and vascular endothelial function are not common therapeutic targets. Previous research has addressed the use of antioxidants in CVD patients, but it has focused on the intake of a single antioxidant (e.g. vitamin E, beta-carotene, ascorbic acid) and not a combination of antioxidants. The utilization of a combination of antioxidants and their effects on blood flow and oxygen transport in CVD are as of yet unclear. The purpose of this proposed study is to examine the effects of acute administration of an oral antioxidant cocktail (containing vitamin C, E, and a-lipoic acid E) on oxidative stress, vascular endothelial function, autonomic function, blood flow, and oxygen delivery during a walking test. It is hypothesized that oral antioxidant cocktail administration will reduce oxidative stress markers, and will increase both vascular endothelial function and blood flow, thus increasing oxygen delivery to the muscles and improving walking capacity. This pending data from acute antioxidant administration will give insight to long-term antioxidant use in CVD patients and its effects on oxidative stress, blood flow, and the integration of O2 transport and utilization in the body.