Browsing by Subject "Endothelial function"
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Item Aging, habitual exercise, and vascular ischemia-reperfusion injury(2009-12) DeVan, Allison Elizabeth; Tanaka, Hirofumi, Ph. D.Ischemia-reperfusion (IR) injury occurs during myocardial infarction and during some cardiovascular surgeries. Animal studies support the role of endurance exercise training in preventing myocardial IR injury and coronary endothelial dysfunction. In human and animal studies, habitual exercise has been shown to attenuate endothelial dysfunction caused by aging and disease. It is unknown; however, if exercise can protect against vascular IR injury in humans and if so, whether these effects persist with advancing age. Using 20 minutes of forearm ischemia and the response of the brachial artery as a noninvasive surrogate model for the heart, the association between the mode of exercise training (endurance versus resistance) and vascular IR injury was examined in young healthy adults in the first study. Endothelial function, as measured by flow-mediated dilation (FMD) in the brachial artery, decreased significantly after forearm ischemia, suggesting that this noninvasive model of the heart produces significant and measureable vascular injury. These measures returned to baseline levels within 30 minutes following ischemia, illustrating the transient nature of this form of IR injury. The magnitude of injury and recovery from ischemia were not significantly different among young sedentary, endurance-trained, and resistance-trained subjects, suggesting that exercise training is not associated with protection from vascular IR injury in a young, healthy population. In the second study, the association between aging, endurance exercise training, and vascular IR injury was studied. Twenty minutes of forearm ischemia was associated with a transient fall in brachial FMD in young and older sedentary and endurance-trained subjects. Young subjects recovered more quickly from IR injury than older subjects. Within 30 minutes of injury, the endothelial function of the young group was back to baseline while blunted endothelial function persisted in older subjects for greater than 45 minutes after injury. There was no association between endurance exercise training and enhanced recovery from IR injury. These findings suggest that aging is associated with delayed recovery from vascular IR injury and that endurance training does not appear to modulate the vascular IR injury responses.Item Hatha yoga and arterial stiffness and reactivity(2011-08) Hunter, Stacy Denise; Tanaka, Hirofumi, Ph. D.; Ivy, John; Coyle, Edward; Brown, Sharon; Silverthorn, DeeThis research assessed the role of Hatha yoga in the modulation of vascular health. In study one, Hatha yoga practitioners were compared to sedentary controls to whom they were matched for age and body mass index. Practitioners of Hatha yoga were no different from sedentary individuals in terms of arterial stiffness or vascular endothelial function. Yoga practitioners possessed lower HbA1c (P < 0.05) levels and lower pulse pressure (P < 0.05) than their sedentary counterparts. Practitioners of Hatha yoga had lower body fat percentages, but this observed trend did not reach statistical significance (P = 0.052). In study two, a 12-week Hatha yoga intervention resulted in reductions in HbA1c levels (P < 0.05) and total cholesterol (P < 0.05) in previously sedentary adults. No changes were observed in carotid artery compliance or brachial artery flow-mediated dilation as a result of the intervention. In study three, obese and lean, apparently healthy adults completed an 8-week Bikram yoga intervention. Reductions in total- and LDL-cholesterol were observed in the lean subjects (P < 0.05), with no changes in lipid profiles in the obese group. The homeostasis model assessment of insulin resistance (HOMA-IR) decreased in the lean subjects, but this trend did not attain statistical significance (P = 0.06). Although an observed trend was shown at 60 minutes during the oral glucose tolerance test (P = 0.07), glucose tolerance remained unchanged in the obese subjects. Brachial artery flow-mediated improved by approximately 2% in the obese subjects, but this observed change did reach statistical significance (P = 0.10). Flexibility increased in both groups as a result of the Bikram yoga intervention. Therefore Hatha yoga improved lipid profiles and glycemic control in sedentary adults, but no effects on vascular health were demonstrated.Item Mechanisms of cutaneous microvascular endothelial dysfunction in young black Americans(2016-12) Kim, Kiyoung, active 2013; Tanaka, Hirofumi, Ph. D.; Farrar, Roger P.; Castelli, Darla M.; Brothers, Robert Matthew; Davis, Scott L.Black Americans have an increased risk for developing a variety of cardiovascular disease (CVD) when compared to white Americans and other populations in the United States. It has also been demonstrated that the underlying impairments in black Americans manifest during early adulthood prior to any overt signs of risk, which leads to higher rates of CVD related morbidity and mortality in black Americans than other populations. Study 1 was designed to investigate the potential mechanisms of cutaneous microvascular dysfunction in young college-age black Americans. This was assessed by measuring the skin blood flow response to local heating while various vasoactive substances were delivered into the cutaneous interstitial space by intradermal microdialysis. We demonstrated that an attenuated nitric oxide (NO) mediated vasodilation due in part to a relative deficit of L-arginine in the endothelial cells is one mechanism by which microvascular dysfunction occurs in young black Americans. Study 2 conducted to investigate the effects of acute cocoa flavanol intake on cutaneous microvascular function in young black Americans. This was assessed by measuring the skin blood flow response to local heating and delivery of vasoactive substances (as described above) before and after consumption of a beverage high in flavanol content. Study 2 demonstrated that acute flavanol intake improved cutaneous microvascular function in response to local heating in young black Americans relative to young white Americans. Study 3 was designed to investigate the effects of acute flavonal intake on endothelium-dependent microvascular dilation in response to exogenous administration of methacholine (MCh) in young black Americans. This was assessed by skin blood flow responses to incremental dose of MCh, which was delivered by intradermal microdialysis, before and after consumption of a beverage high in polyphenol content. Study 3 identified that acute flavanol intake did not alter the dose-response curve of MCh-induced cutaneous vasodilation in either racial groups. Overall, the series of studies in this dissertation may provide evidence that young black Americans have attenuated microvascular function relative to young white Americans, and that a potential mechanism of decreased microvascular function is a decrease in NO bioavailability and/or NO mediated vasodilation, which is related to a deficit of L-arginine in the endothelial cells in young black Americans. Furthermore, our findings may provide evidence that the consumption of cocoa flavanols is an effective therapeutic strategy to prevent and/or delay the development of CVD at least in young black Americans.Item The effects of fluid milk in attenuating postprandial hyperglycemia and hypertriglyceridemia(2016-12) Leary, Miriam Elizabeth; Tanaka, Hirofumi, Ph. D.; Coyle, Edward F; Stone, Audrey; Davis, JamieThe increased risk of cardiovascular disease (CVD) and vascular dysfunction that is associated with postprandial hyperglycemia and hypertriglyceridemia may be reduced with consumption of non-fat dairy products. Due to the insulinotropic effect of milk-derived proteins, postprandial hyperglycemia has been shown to be reduced with the addition of dairy products. The purpose of Study 1 was to determine if one serving of non-fat milk added to an oral glucose tolerance test (OGTT) could attenuate postprandial hyperglycemia in individuals with elevated android adiposity independent of the effects of the milk’s protein content and whether these improvements would be associated with metabolic and/or peripheral hemodynamic effects. In this placebo controlled, randomized, crossover experimental study, twenty-nine overweight/obese adults consumed an OGTT combined with either non-fat milk or a placebo control. In the whole sample, blood glucose and insulin concentrations increased over time in both trials with no differences between trials. When the subjects were divided into tertiles of android body fat, the highest tertile displayed attenuated hyperglycemic responses as well as improvements in flow-mediated dilation during the milk intervention. Repeated exposure to elevated postprandial triglycerides, as seen with typical Western diets, contributes to atherosclerosis and vascular disease. The purpose of Study 2 was to determine if a single serving of non-fat milk added to a high fat meal could attenuate postprandial hypertriglyceridemia in individuals who consume a high fat diet. In this placebo controlled, randomized, crossover experimental study, thirty overweight/obese adults consumed a high fat meal combined with either non-fat milk, carbohydrate control, or caloric control. In the whole sample, plasma triglycerides increased over time with no differences between interventions. When participants were ranked and divided based on habitual dietary fat intake, the high fat diet group exhibited reduced triglycerides when supplemented with non-fat milk. No differences in hemodynamic measures (brachial flow-mediated dilation and femoral vascular conductance) were observed between the milk and caloric control trials for either the low fat or high fat diet groups. Taken together, the results indicate that a single serving of non-fat milk may attenuate acute hyperglycemia and hypertriglyceridemia in individuals that present with specific risk factors for CVD.