Kinesiology
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Item THE EFFECTS OF AGE, SARCOPENIA, AND RESISTANCE EXERCISE TRAINING ON MITOCHONDRIAL STRUCTURAL DYNAMICS IN SKELETAL MUSCLE(2024) Sapp, Catherine; Prior, Steven J; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Sarcopenia, the progressive, age-related loss of skeletal muscle mass, contributes to older adults’ risk of falls, hospitalization, and loss of independence. Mitochondrial dysfunction is a hallmark trait of aging and sarcopenia that may be mediated by changes to mitochondrial structure and location through the involvement of mitochondrial fusion, fission, and mitophagy (collectively referred to as mitochondrial quality control). Therefore, the purpose of this dissertation was to investigate whether mitochondrial quality control is altered by age or sarcopenia. The first study performed in a rat model of aging demonstrated that expression of proteins regulating fusion and mitophagy was higher in skeletal and cardiac muscle from old vs. young rats, and this was accompanied by reduced expression of fission proteins in skeletal muscle in the old rats. The second study included older humans and revealed no differences in mitochondrial quality control protein expression in skeletal muscle from sarcopenic vs. non-sarcopenic older adults. Furthermore, twelve weeks of resistance exercise training did not alter the expression of mitochondrial quality control proteins in the sarcopenic individuals. The third study investigated morphological differences in mitochondrial subpopulations and lipid droplets from the sarcopenic individuals from study two, both before and after resistance exercise training. Peripherally located and intermyofibrillar mitochondrial content and morphology did not change significantly after resistance exercise training. Lipid droplets from the intermyofibrillar region were similarly unchanged, but lipid droplets from the peripheral region had minor morphological changes after resistance exercise training. Together, this dissertation indicates that mitochondrial quality control proteins in skeletal and cardiac muscle are altered in response to aging and may contribute to mitochondrial dysfunction, but mitochondrial structural dynamics in skeletal muscle do not appear to be altered in older adults with a moderate degree of sarcopenia. This suggests that other, non-mitochondrial factors may play larger roles in the pathophysiology of sarcopenia. While the sarcopenic participants did improve muscular strength after resistance training, this was not accompanied by changes in mitochondrial content, morphology, or quality control. Therefore, resistance exercise training may not be an effective strategy to enhance mitochondrial structural dynamics in sarcopenia.Item HIPPOCAMPAL GLUCOSE TRANSPORT AND OXIDATION IN RESPONSE TO DISRUPTED BLOOD FLOW IN AN AGING RAT MODEL OF HEART FAILURE(2023) Pena, Gabriel Santiago; Smith, J. Carson; Kuzmiak-Glancy, Sarah; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The primary objective of this dissertation was to investigate, in a rodent model of cardiovascular disease promoted by transverse aortic constriction (TAC), whether cerebral hypoperfusion stemming from chronic high pulsatile blood flow, and cerebral hypoperfusion stemming from low cerebral blood flow differentially affected hippocampal glucose transport and hippocampal mitochondrial function. We first, characterized the changes in right and left carotid hemodynamics and diameter in response to TAC and in a SHAM control group at three different time points (20-, 30-, and 40 weeks) post-surgery. Then, right, and left hippocampal mitochondrial content and substrate oxidation were investigated, and protein expression of glucose transporters and mitochondrial quality control markers were quantified. In this study, both the SHAM and TAC conditions included male and female rats to address possible sex differences. We report that all time points within TAC, right carotid blood flow velocities and pulsatility were greater than the left, but did not worsen over time. No differences in mitochondrial content were found within TAC nor between TAC and SHAM, but within TAC animals there were impairments in right hippocampal coupled and uncoupled respiration when compared to the left. When compared to the SHAM controls, right and left hippocampi of TAC animals had higher protein expression of mitochondrial quality control markers, but no differences in glucose transporter expression were found. Thus, while both high blood flow and/or pulsatility as well as low cerebral blood flow may lead to brain hypoperfusion, the metabolic consequences of the two may not be the same. The results from this dissertation contribute to the expanding literature characterizing the intersection between cardiovascular disease and neurodegeneration.Item FUNCTIONAL CONNECTIVITY PATTERNS ASSOCIATED WITH AGING, PHYSICAL ACTIVITY, AND GENETIC RISK FOR ALZHEIMER’S DISEASE IN HEALTHY HUMAN BRAIN NETWORKS.(2017) Chirles, Theresa Jeanne; Smith, Carson J; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Leisure time physical activity (PA) and exercise training help to improve and maintain cognitive function in healthy older adults and in adults with the APOE-ε4 allele, a genetic risk for Alzheimer’s Disease (AD). Earlier work finding increased functional connectivity in the Default Mode Network (DMN) after a 12-week walking intervention in 16 older adults with mild cognitive impairment is presented in Chapter 3. The primary dissertation study investigating differences in brain function depending on PA level and genetic risk for AD prior to changes in cognition is presented in Chapters 4-6. Useable resting state and anatomical MRI scans were collected from 69 healthy adults (22-51 years) as well as saliva for APOE genotyping (carriers defined as homozygotes or heterozygotes of the ɛ4 allele) and responses to the Paffenbarger Physical Activity Questionnaire (High PA >1500 kcal, Low PA <1500 kcal per week). The following network measures of functional connectivity were calculated: global efficiency; node strength of Default Mode Network (DMN) and Fronto-Parietal Network (FPN) hubs and hippocampal subsections; and long-range connectivity of the medial prefrontal cortex (mPFC) and posterior cingulate cortex (PCC) in the DMN. Multiple linear regression analysis revealed statistically significant results for the long-range connectivity of the left PCC, a prominent hub of the DMN, and left mPFC. The differences in projected trajectories of the connectivity are potentially reflective of the compensatory time-course in our participants based on interactions of PA level and APOE status. The Low PA non-carriers had a positive slope indicating increased connectivity with age while carriers and non-carriers in the High PA category had horizontal aging trajectories. PA is associated with cognitive reserve (CR), a term describing the protection and adaptation of cognitive processes through neural efficiency and compensation mechanisms, and it is possible the Low PA non-carriers exhibited compensatory increases in connectivity of the left mPFC-PCC earlier than High PA study participants due to lower levels of CR. The promising findings that rs-fMRI can be used as an early detection of brain changes sensitive to PA levels and APOE-ɛ4 status are critical to the research and treatment of AD.Item Aging Related Differences in Hand Intrinsic and Extrinsic Muscles for Hand Dexterity: An MRI Investigation(2009) Hsu, Jeffrey; Shim, Jae Kun; Kinesiology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Hand dexterity is crucial for humans to interactions with the external environment. Many activities of daily living (ADLs) such as pressing, grasping, writing and typing would be unattainable without a skillfully and proficiently functioning hand. Sexagenarians and older often experience difficulties in hand dexterity, which seriously impair their ability to perform ADLs. This study described the aging-related changes in hand muscle size and dexterity; and addressed the conflicting literature regarding the extent of atrophy to either the intrinsic or extrinsic hand muscles in the elderly. The overall hypotheses for this study were 1) that elderly adults show an aging-related decrease in hand muscle size and strength, especially a greater decrease in the intrinsic hand muscles, 2) elderly adults show an aging-related decrease in hand dexterity and 3) hand muscle size and strength are positively related to hand dexterity. This study examined hand muscle sizes with magnetic resonance imaging (MRI) and examined hand strength and other functional measures. This study found aging-related decreases in muscle size, muscle strength, hand dexterity. Furthermore, intrinsic muscles showed a greater aging-related decrease in volume and strength as compared to the extrinsic muscles. When examining relationships, muscle strength was positively correlated to multi-finger synergy and finger dependence. Also, muscle size was positively related to performance on clinical hand dexterity tests. This supports the strength-dexterity equivalence hypothesis.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.