PhD Dissertations - DO NOT EDIThttp://hdl.handle.net/10106/248732024-03-29T06:49:44Z2024-03-29T06:49:44ZPartitioning the Role of Myocardial Steatosis on Left Ventricular Functionhttp://hdl.handle.net/10106/317702023-11-09T22:41:26Z2023-08-07T00:00:00ZPartitioning the Role of Myocardial Steatosis on Left Ventricular Function
**Please note that the full text is embargoed until 8/1/2025** ABSTRACT: Preclinical studies have long suggested that excess lipid accumulation within cardiomyocytes (myocardial steatosis) leads to adverse cardiac remodeling and ventricular systolic and diastolic dysfunction. Whether myocardial steatosis negatively affects the human heart is less clear. Innovations in 1H magnetic resonance spectroscopy (MRS), introduced nearly 20 years ago, provide a method for in vivo quantification of myocardial triglyceride content that has been used to describe myocardial steatosis in obesity, type-2 diabetes, and across multiple disease states. However, most of this literature consists of cross-sectional observations. While these studies identify associations between myocardial steatosis and adverse remodeling and/or cardiac function, the presence of concurrent comorbidities may be confounding these results. Accordingly, this dissertation focused on studying myocardial steatosis and its effect on cardiac function, independent of underlying comorbidities, in humans. First, we utilized a 48-hour fasting model in young, healthy adults to elicit an acute increase in myocardial triglyceride content that contributed to left ventricular (LV) diastolic dysfunction. Although we were encouraged by these findings, we considered whether fasting-induced metabolic shifts (i.e., increased circulating ketones and non-esterified fatty acids[NEFAs]) may have influenced our results. Therefore, we performed separate studies manipulating each, independent of changes in myocardial triglyceride content, and demonstrated that neither metabolic shift influence LV diastolic function in young, healthy adults. We also maximized technical advancements in 1H MRS to highlight the complex lipid environment within the myocardium beyond that traditionally assessed as total myocardial triglyceride content. Together, the work performed herein supports the independent effect of myocardial steatosis on LV function and offers an opportunity for future research to expand our understanding of this deleterious effect.
2023-08-07T00:00:00ZReducing Disparities in Physical Activity and Early Child Development: A Systematic and Observational Approachhttp://hdl.handle.net/10106/314602023-07-01T08:27:36Z2022-08-15T00:00:00ZReducing Disparities in Physical Activity and Early Child Development: A Systematic and Observational Approach
**Please note that the full text is embargoed until 8/14/2024** ABSTRACT: Engaging in adequate (180 minutes per day) physical activity (PA) is an important component in positioning a young child towards optimal health. PA engagement has been linked to improved cardiovascular health, developmental outcomes (i.e., motor, social, and cognitive development), and weight status. Even with the known benefits PA posits, many young children do not receive enough PA during their day. More specifically, children that are of low socio-economic status (SES) pose a greater risk for inactivity, excessive sedentary behavior, and developmental delays. Knowing these disparities exist, even starting in the early childhood years, children’s PA and development remain complex. Using the social-ecological model as a foundation, uncovering these underlying determinants of children’s activity and development is needed. This dissertation will add to further reducing childhood disparities by systematically examining the available home environment literature to provide actionable strategies and recommendations for parents, practitioners, and community stakeholders, and by investigating the role of parenting practices and environment on PA and development in early childhood. Study 1 comprehensively examined and analyzed the effects of home/family- and community-based interventions on weight status (i.e., body mass index [BMI]), PA (i.e., moderate-to-vigorous PA [MVPA], sedentary behavior) and developmental outcomes (i.e., FMS) in early childhood (2-5 years old). After searching four electronic databases, 24 studies were retained that investigated outcomes relevant to weight status (i.e., BMI), physical activity, sedentary behavior, and/or motor proficiency in home/family, or community settings in 2-5 year old children. Distributing educational material to parents/families, maintaining direct contact with parents, and fostering community engagement were all identified as effective strategies to promote PA, reduce sedentary behavior, maintain healthy weight status, and enhance motor skills in children. Study 2 employed a cross-sectional approach to uncover environmental determinants towards childhood PA and development and investigate SES disparities. There were 138 toddlers (Mage=3.87±.88 years; 79 girls; 45 Hispanic) that were recruited from Northern Texas. Children’s PA was objectively measured by wearing an accelerometer (GT9X ActiGraph) for 7 consecutive days. Parent’s reported children’s PA, sedentary behavior, developmental outcomes (i.e., communication, gross and fine motor skills, problem solving, and personal social), PA parenting practices (i.e., encouraging or discouraging behaviors), home environment (i.e., affordances in the home environment that facilitate motor development), and physical activity neighborhood environment (i.e., physical environment, recreation facilities, and neighborhood safety) were assessed through validated questionnaires. Results showed parenting practices to emerge as a significant predictor towards parent-reported PA, accelerometer-measured sedentary behavior, and problem solving. PA neighborhood environment and home environment were significant predictors towards problem solving. There were no observed SES differences in PA or developmental outcomes. Overall, almost 100% of children met the PA guideline, however no children met the sedentary guideline (<1 hour per day) according to the accelerometer measures. On the other hand, via parent-report survey, over 50% of children were considered active and approximately 1/3 of children engaged in less than 1 hour of screen-based sedentary behavior. Only 66.7% of boys are typically developing in fine motor and problem solving and 75% or less toddlers are typically developing in all categories. These findings underscore the importance of enabling a supportive home environment through parenting practices and adequate outside space to potentially enhance activity and development in early childhood, regardless of SES.
2022-08-15T00:00:00ZELEVATED CARDIOVASCULAR DISEASE RISK IN BLACK FEMALES: THE IMPACT OF SOCIAL DETERMINANTS OF HEALTH AND NOVEL PREVENTIVE STRATEGIEShttp://hdl.handle.net/10106/314462023-07-01T08:26:46Z2022-08-15T00:00:00ZELEVATED CARDIOVASCULAR DISEASE RISK IN BLACK FEMALES: THE IMPACT OF SOCIAL DETERMINANTS OF HEALTH AND NOVEL PREVENTIVE STRATEGIES
**Please note that the full text is embargoed until 8/14/2024** ABSTRACT: Among females in the United States, Black females suffer from the highest rates of hypertension, coronary artery disease, stroke, and total cardiovascular disease (CVD) mortality. Blunted peripheral and cerebral vascular function contribute to the development of CVD and are predictive of CVD risk. Although the causes of disparate cardiovascular health among Black females are multifactorial, upstream contributors such as psychosocial stress attributable to structural and interpersonal racism are likely critical. However, the societal changes required to dismantle structural racism and thus improve health outcomes may take decades to implement. Therefore, in addition to such policy changes, populations who face health disparities should also know which personal and behavioral approaches might be efficacious for preventing and reversing CVD. Accordingly, the purpose of this dissertation was to 1) investigate the influence of psychosocial stress on blunted vascular function in Black females and 2) investigate the impact of novel preventive strategies for reducing CVD risk in Black females. Chapter 2 demonstrated that blunted vascular endothelial function in Black females may be due more to internalization of psychosocial stress and maladaptive coping mechanisms than exposure to psychosocial stressors alone. Chapter 3 demonstrated that Black individuals who adhere to a 100% plant-based diet may be afforded enhanced cardiovascular protection through lower peripheral and central blood pressure, a more optimal cholesterol profile, and potentially lower systemic inflammation, but not better vascular function. Chapter 4 demonstrated that one session of heat therapy acutely improves peripheral micro- and macrovascular but not cerebral vascular function in Black and White females. Taken together, this research contributes new knowledge regarding potential upstream causes as well as novel solutions to the ongoing disparity in cardiovascular health and function among Black females in the United States.
2022-08-15T00:00:00ZInvestigating the Short-term and Long-term Impact of COVID-19 on Cardiovascular Healthhttp://hdl.handle.net/10106/314202023-08-11T18:08:58Z2022-08-15T00:00:00ZInvestigating the Short-term and Long-term Impact of COVID-19 on Cardiovascular Health
Recent data indicates that the risk of developing cardiovascular disease (CVD) is augmented following coronavirus disease 2019 (COVID-19). Moreover, emerging data indicates that almost 50% of individuals who had COVID-19 experience persisting symptoms which are often debilitating, beyond the acute phase of the illness. This condition that is given the diagnosis post-acute sequalae of COVID-19 (PASC), also appears to be associated with cardiovascular complications. However, it is unclear what factors contribute to CVD risk following COVID-19 and PASC. Accordingly, the aim of this dissertation was to investigate potential factors that may contribute to adverse cardiovascular outcomes following COVID-19 with a focus on several key determinants of cardiovascular health, namely peripheral and cerebral vascular function, arterial stiffness, and blood pressure (BP). Given that young adults between 18 – 29 years account for almost 25% of the COVID-19 cases in the United States, study 1 and 2 focused on this population. In study 1, we tested the hypothesis that young, otherwise healthy adults who are beyond 4 weeks from a COVID-19 diagnosis would exhibit blunted peripheral and cerebral vasodilator function and increased central arterial stiffness compared with those who did not have COVID-19. The major novel findings from this study are that 1) peripheral macro- and microvascular vasodilator function are blunted in young adults still symptomatic from COVID-19, but not in those who were asymptomatic beyond the acute phase, and 2) cerebral vascular function and central arterial stiffness are unaffected beyond the acute phase irrespective of COVID-19 symptomology. Extending our findings, and those of others demonstrating detrimental effects of COVID-19 on vascular health in young adults, in study 2 we aimed to perform a comprehensive assessment of BP using ambulatory and laboratory techniques in this population. Findings from this study demonstrated that ambulatory and laboratory BP are higher in those closer to a COVID-19 diagnosis compared to those who are further out from diagnosis, suggesting a transient effect of COVID-19 to elevate BP in young adults. Finally, study 3 aimed to evaluate vascular health in PASC with a focus on investigating a potential link between cardiovascular health and symptomology. We show for the first time that patients with PASC have higher BP and central arterial stiffness whereas peripheral and cerebral vasodilator function appears to be unaffected. Moreover, although there were no associations between total symptom burden and measures of vascular function, we found that resting cerebral blood flow was inversely correlated with the severity of brain fog with those with the greatest severity of brain fog having the lowest cerebral blood flow. Collectively, the work described herein provides novel insight into the impact of COVID-19 on key determinants of cardiovascular health that may contribute to the greater CVD risk following COVID-19 in young adults and in PASC.
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