School of Public Health
Permanent URI for this communityhttp://hdl.handle.net/1903/1633
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
Note: Prior to July 1, 2007, the School of Public Health was named the College of Health & Human Performance.
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Item Effects of exercise and inflammation on circulating microparticles(2024) Heilman, James; Prior, Steven J.; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Circulating microparticles (MPs), a subset of extracellular vesicles, have been implicated as novel biomarkers connected to vascular dysfunction. As such, they may contribute to atherosclerosis, hypertension, and other conditions leading to cardiovascular disease. MPs are involved in cell-to-cell communication in response to apoptosis and activation of the immune and inflammatory response, transferring their contents to nearby cells and effectively spreading each condition. The objective of this dissertation was to explore how circulating MP number and function are affected by stimuli such as diet and exercise. Our first study examined how post-prandial inflammation caused by a high-fat meal affects circulating MP number and function in young, healthy adults. We determined that a high fitness level may have a protective effect against the inflammatory load posed by a high-fat meal. The second study determined the effects of acute high-intensity interval aerobic exercise versus acute moderate intensity continuous aerobic exercise on circulating MP number and function in overweight versus lean recreationally active adults. We found that MPs and arterial stiffness in overweight individuals are differentially impacted by the type of acute exercise. Our findings suggest that overweight individuals undergo a greater inflammatory response following high-intensity exercise compared to lean. The third study investigated the effects of a 6-month aerobic exercise training program on circulating MP counts and function in previously sedentary older adults. While we found no effect of the exercise training program on MPs, we provide insight into how improvements in cardiovascular fitness as well as higher exercise intensities may be needed to see changes in MP number and function following aerobic exercise training in older adults. For the first time, we have shown that both dietary inflammation and acute exercise can significantly impact MP function. Furthermore, we have shown that fitness status and body composition play important roles in determining MP number and function after each stimulus. Our findings provide novel insight into how MPs contribute to various types of inflammation as well as how they may be used as biomarkers to measure the progression of cardiovascular disease.Item Sex- and Race-Based Differences in the Effects of Acute and Chronic Exercise on Vascular Function and Circulating MicroRNA(2021) Sapp, Ryan M; Hagberg, James M; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Cardiovascular disease (CVD) is the leading global cause of death. Disparities in CVD development exist, with greater rates observed in men than women and in African Americans (AA) than Caucasian Americans (CA). It is crucial to determine the molecular mechanisms underlying these disparities in order to formulate preventative strategies. Regular aerobic exercise reduces CVD risk, while acute exercise is a useful stimulus to reveal impairments in cardiovascular function not apparent at rest. This dissertation utilizes approaches to identify sex- and race-based differences in vascular function within young, healthy individuals, indicative of future CVD risk, including the use of acute exercise as a cardiovascular stimulus and the exercise-trained individual as a model of superior cardiovascular health. Aim #1 shows that exercise training is associated with beneficial effects of the circulating factors in serum on vascular endothelial cells, in a sex-specific manner, suggesting that circulating factors are differently affected by exercise training in men and women. Aim #2 shows that endothelial function and central arterial stiffness respond similarly to acute exercise in AA and CA. Carotid arterial compliance, however, is increased only in CA during exercise recovery. MicroRNAs (miRs) are epigenetic modulators of gene expression implicated in CVD development. Blood-borne circulating miRs (ci-miRs) are paracrine/endocrine molecules and preclinical biomarkers, yet sex- and race-based differences in ci-miRs are understudied. Additionally, ci-miRs are altered with exercise and may mediate training-induced vascular adaptations. Aim #3 of this dissertation reveals that the resting concentrations of select vascular-related ci-miRs differ based on sex and exercise training status, but not race. In response to acute exercise however, several anti-inflammatory ci-miRs increased significantly in CA, but not AA. Additionally, the changes in one anti-inflammatory ci-miR exhibited race-specific correlations with the changes in carotid arterial compliance identified in Aim #2. Aim #4 investigates the hypothesis that exercise elicits endothelial integral damage, and that this may mediate changes in vascular function and endothelial-derived ci-miRs. By measuring different endothelial-derived circulating factors, we show that exercise likely does not cause endothelial cell detachment or apoptosis. Thus, ci-miR are likely released via a selective method of secretion, rather than passively leaking from damaged endothelium.Item Understanding and Retraining the Causal Attributions for Exercise Intenders(2019) Singpurwalla, Darius; Iso-Ahola, Seppo E; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Given that ~50% of all exercise intenders will fall into the intention-behavior gap (i.e., a situation where people fail to act on their intentions), it is necessary to identify the constructs and/or theories that can explain the discord between intention and behavior (i.e., the intention-behavior gap). For this purpose, the present research was conducted through two studies that were designed to test the efficacy of causal attributions as a means to reduce the intention-behavior discord. The first study collected information from 952 individuals on their exercise behavior and their associated causal attributions over a six-week period. The findings from this study included: (1) those individuals who fell into the intention-behavior gap made self-serving attributions for their exercise failure; (2) Weiner’s model accurately predicted several of the affective and cognitive responses to exercise behavior for the sample of exercise intenders; and (3) causal attributions were not found to be effective moderators of the intention-behavior relationship. The second study was an experiment that tested whether an attribution retraining intervention could improve exercise behavior for a sample of sedentary, exercise intenders (n=200). Results of this study were mixed as the intervention appeared to have been able to modify one of the targeted attributional dimensions (control), but the effect was not strong enough to change the exercise behavior of the participants in the experimental group. It is suggested that attributions may not be able to reduce the gap because they represent conscious deliberations of the behavior, while sustained exercise is based on nonconscious processing of relevant information to make exercise an automatic behavior.Item EXERCISE IS MEDICINE? A CRITICAL EXAMINATION OF THE PROMOTION OF EXERCISE FOR MENTAL HEALTHCARE(2018) Maier, Julie; Jette, Shannon L; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Increasingly, physical activity is being promoted as a way to prevent or treat a range of chronic health conditions, including mental illness. In this dissertation, I utilize an ecological framework and draw upon feminist theories to explore why it is that physical activity is being used as a form of (mental health) therapy in this current moment, as well as the benefits and shortcomings of physical activity in preventing or treating mental illness. In particular, I focus on the ways in which gendered discourses and norms shape the physical activity experiences of women with mental illness. The project entails three separate, yet related, phases: 1) Extensive review of popular and academic literature to contextualize the “exercise is medicine” movement; 2) Assessment of the American College of Sports Medicine and American Medical Association’s “Exercise is Medicine” initiative; and 3) In-depth qualitative interviews with women with obsessive compulsive disorder (OCD). The results of my three empirical examinations suggest that physical activity can be a beneficial form of mental health treatment, or a valued part of one’s life and identity more generally. However, too often the limits to physical activity’s effectiveness in treating particular mental illnesses is downplayed, as is attention to the potential harms that can come from being physically active. At times, exercise is even positioned as a “cure”, or superior to psychopharmaceuticals in treating mental illnesses, such as depression. Such enthusiasm toward exercise’s potential therapeutic value can be seen to be, in part, the result of the current neoliberal, healthist moment in which individual responsibility, hard work, and natural remedies are valued over that which is considered easy, quick, or synthetic (Crawford, 1980, Lupton, 1995, Fullagar, 2017). This is not to suggest that physical activity cannot play a vital role in helping people with mental illness, but better messages and more resources are needed to make it accessible, safe, and meaningful to this population. I conclude the dissertation by providing suggestions as to how this can be accomplished.Item Exercise training-associated differences in circulating microRNAs and serum-induced endothelial cell migration rate(2015) Sapp, Ryan M.; Hagberg, James M; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Cardiovascular Diseases (CVDs) are the primary source of global mortality and morbidity. The initial steps of CVD development occur in the endothelium. MicroRNAs (miRNAs) have recently emerged as novel regulators of cardiovascular physiology and pathology. Interestingly, regular aerobic exercise acts to prevent CVDs and also regulates miRNAs in the circulation (ci-miRNAs). The purpose of this study was to determine the effects of serum from highly active and sedentary, young, healthy individuals on migration rate of endothelial cells in vitro. Secondarily, CVD-associated ci-miRNAs in serum were compared between groups. The results of this study represent a novel way by which sedentary behavior may act as an early risk for CVD development before the appearance of other classic risk factors. RT-qPCR array analysis identified nine ci-miRNAs as > 4-fold differentially expressed in serum of trained versus inactive subjects, though more subjects are needed before any conclusions about ci-miRNA differences can be made.Item Breast Cancer Type 1 Susceptibility Protein is a Critical Regulator of Skeletal Muscle Lipid Metabolism(2013) Jackson, Kathryn Campbell; Spangenburg, Espen E; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation research consists of three investigations in an effort to determine how circulating estrogens affect skeletal muscle lipid metabolism. Loss of circulating estrogens results in significant increases in visceral fat mass and intramuscular lipids (IMCL). These increases in lipid storage are strongly associated with an elevated risk of developing type 2 diabetes. The first investigation examined how the loss of circulating estrogens alters skeletal muscle metabolic function. Ovariectomy (OVX) resulted in significantly higher visceral fat mass and fatty acid sarcolemmal transporter content, which corresponded with elevated IMCL. Skeletal muscle in the OVX group exhibited lower acyl carnitine species suggesting impaired lipid flux through the mitochondria. Lastly, mitochondrial oxygen consumption rates were impaired in OVX skeletal muscle fibers. The results from this study gave rise to a search to identify an estrogen- sensitive mechanism that regulated lipid transport into the mitochondria. Study two determined for the first time that the BRCA1 protein, which is encoded by an estrogen-sensitive gene, is present and functions as an integral regulator of lipid metabolism in skeletal muscle. Specifically, BRCA1 binds to acetyl CoA carboxylase in response to acute exercise. The in vitro induction of decreases in BRCA1 expression resulted in higher IMCL content, reduced mitochondrial oxygen consumption rates, and elevated reactive oxygen species production. Surprisingly, no differences in BRCA1 content were detected between males and females. In the final study, an inducible, skeletal-muscle specific, BRCA1 KO mouse was developed. Ablation of BRCA1 in skeletal muscle resulted in exercise intolerance and the development of kyphosis. Contrary to our hypothesis, loss of functional BRCA1 in skeletal muscle attenuated the negative metabolic consequences of chronic high fat diet exposure. Collectively, these data provide strong rationale that BRCA1 is an important regulator of skeletal muscle metabolic function and further provide evidence that BRCA1 function is critical in multiple tissues across the body.Item Effects of chronic exercise on global DNA methylation and epigenetic factors in sperm and testes of mice.(2012) Marini, Michael Paul; Roth, Stephen M; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Epigenetic alterations of DNA affect DNA transcription and translation. These alterations occur frequently, however environmental exposures induce epigenetic changes to DNA that would otherwise remain in autoregulatory stasis. This study aimed to look at exercise as a possible environmental factor causing epigenetic change. The study also assessed global DNA methylation in sperm, which may transmit such epigenetic changes via the paternal germ line. Measurements were compared between groups of mice that engaged in chronic exercise or remained sedentary. This study also examined enzymes causing methylation shifts in sperm by comparing levels of mRNA expression of genes responsible for new DNA methylation - DNMT3A, DNMT3B and DNMT3L - in testes. These results were compared between exercise and sedentary cohorts, and in progeny to assess heritability of epigenetic change. The results showed a significant difference in global methylation in the sperm between exercise and sedentary cohorts and a concomitant increase in gene expression in multiple DNMT3 genes.Item TELOMERE DYNAMICS AND REGULATION: EFFECTS OF CHRONIC EXERCISE, ACUTE EXERCISE, AND OXIDATIVE STRESS(2011) Ludlow, Andrew Todd; Roth, Stephen M; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation research is comprised of three studies each examining the effects of chronic exercise, acute exercise, or oxidative stress on telomere biology. Exercise training and physical activity have previously been associated with telomere maintenance, but the underlying mechanisms of this association are unclear. The majority of studies to date have been performed in immune cells; however, the findings from these cells may not reflect telomere biology in other tissues. Since exercise is a multi-organ stimulus we sought to describe the effect of exercise on telomere biology in multiple tissues, with a particular focus on skeletal muscle. Study #1 showed that the effect of chronic voluntary exercise on telomere length in CAST/Ei mice is tissue specific. Exercise was `telo-protective' (i.e., maintained telomere length) in cardiac and liver tissues, while telomere shortening was observed in skeletal muscle of exercised animals compared to sedentary and young mice. Study #2 was performed to elucidate the responses to acute exercise that could underlie the paradoxical response of telomere length in skeletal muscle to exercise training. This study revealed that the MAPK pathway appears to be related to the expression of telomere binding proteins in response to acute exercise. In skeletal muscle, p38 MAPK mediated a decrease in gene expression of telomere binding proteins, providing insight into a possible mechanism for eventual telomere shortening in response to chronic exercise. The results of study #2 indicate that the early cellular responses to exercise may accumulate (i.e., repeat bout effect) and underlie the shortened telomere length in skeletal muscle. Study #3 sought to determine if reactive oxygen species were a plausible mechanism of telomere shortening in adult skeletal muscle fibers, as no mechanism to date has been elucidated for telomere shortening in this tissue. Study #3 showed that oxidative stress is a potent telomere- shortening stimulus in skeletal muscle fibers of mice and that telomere binding protein expression was also significantly affected by oxidative stress. In total these results indicate that although chronic exercise attenuates telomere shortening in most tissues, skeletal muscle demonstrates a unique contradictory response likely due to its reaction to oxidative stress.Item Relationship between physical activity and telomere maintenance in peripheral blood mononucleocytes(2007-07-24) Ludlow, Andrew Todd; Roth, Stephen M; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The purpose of this study was to examine the relationship between exercise energy expenditure (EEE) and telomere length, telomerase activity, and hTERT genotype. Sixty-nine male (n = 34) and female (n = 35) participants 50-70 yr. were assessed for weekly EEE level using the Yale Physical Activity Survey. Subjects were grouped according to EEE. Telomere length and telomerase activity were measured in peripheral blood mononuclear cells (PBMCs). Relative telomere length was significantly higher in the Middle EEE group compared to both the low and high EEE groups (p<0.05). Telomerase activity was not different among the three EEE groups. The TT hTERT genotype had significantly greater telomerase enzyme activity than both the CT and CC genotypes (P = 0.013). In conclusion, moderate exercise energy expenditure levels may provide a protective effect on PBMC telomere length compared to both low and high EEE levels. hTERT genotype was associated with telomerase activity.Item The Effects of Strength Training on Regional Body Composition in Older Adults: Sex and Race Comparisons(2007-05-22) Walts, Cory; Hurley, Ben F; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Purpose: To examine the influence of sex and race on the effects of strength training (ST) on thigh muscle volume (MV), mid-thigh subcutaneous fat (SCF) and intermuscular fat (IMF). Methods: One hundred and eighty-one previously inactive healthy Caucasian (N=117), African-American (N=54), and other (N=10) men (N=82) and women (N=99), aged 50-85 yrs, underwent ~10 weeks of unilateral knee extension ST. Results: Training-induced increases in absolute MV were significantly greater (P < 0.01) in men than in women. There were significant increases in MV within each race (P < 0.001); but no significant differences between races. There were no significant changes in SCF and IMF whether sex and racial groups were separated or combined. In addition, there was no sex by race interaction for changes in MV, SCF, or IMF with ST. Conclusion: Ten weeks of unilateral strength training does not alter subcutaneous or intermuscular fat regardless of sex or racial differences. Although men exhibit a greater muscle hypertrophic response to strength training compared to women, the difference is small. Race does not influence this response.