Effects of diet and hibernation in skeletal muscle performance
| dc.contributor.author | Krishnan, Jishnu K.S. | |
| dc.date.accessioned | 2023-02-03T22:30:46Z | |
| dc.date.available | 2023-02-03T22:30:46Z | |
| dc.date.issued | 2022-12 | |
| dc.identifier.uri | http://hdl.handle.net/11122/13123 | |
| dc.description | Dissertation (Ph.D.) University of Alaska Fairbanks, 2022 | en_US |
| dc.description.abstract | Hibernating animals, such as the arctic ground squirrel (AGS), are subjected to a wide range of temperature variations. During hibernation, when they are predominantly physically inactive, body temperature can drop as low as -3°C, while in summer, body temperature can climb as high as 40°C. Torpor is a state of inactivity in an animal induced by a lack of food, which is followed by a fall in body temperature and metabolic rate. Torpor lasts around 21 days in AGS, and the progression of torpor begins with early torpor, followed by mid and late torpor, and culminates with interbout arousal lasting less than 24 hours. AGS exhibit reduced muscular atrophy and protein loss despite lengthy periods of immobility, hypometabolism, and severe hypothermic conditions during hibernation. Skeletal muscle plasticity, unique to mammalian hibernators, may explain why cardiac and respiratory skeletal muscle can function at hypothermic temperatures during and after hibernation. As a result, understanding the effects of ambient temperature on muscle physiology and contractile function is critical. The focus of this research was to investigate skeletal muscle contractile performance and fatigue resistance in ex vivo muscle tissues during hypothermic temperature stress. Ex vivo tissue organ bath functional assays were performed in hibernator and/or non-hibernator rodent models to determine changes in performance and fatigue resistance in the AGS diaphragm induced by polyunsaturated fatty acid dietary modification or ambient hypothermic stress. This study lends support to the idea that diet and hypothermic stress might modify certain functional aspects of skeletal muscle, most likely via membrane lipid composition, ambient temperature, and torpor interaction. Furthermore, summer active AGS has a higher fatigue resistance than mid torpor AGS during the hibernating season. Furthermore, skeletal muscle fatigue resistance was significantly lower in Sprague Dawley rats than in both summer active and hibernating AGS. Preliminary data also suggested that hypothermic stress, to some extent, enhanced fatigue resistance regardless of torpor status or species difference. | en_US |
| dc.description.tableofcontents | Chapter 1. General introduction -- 1.1). Normal muscle physiology -- 1.1.1). Structure of skeletal muscle -- 1.1.2). Neuromuscular junction -- 1.1.3). Calcium buffering & transportation -- 1.1.4). Calcium release -- 1.1.5). Muscle contraction -- 1.1.6). Muscle relaxation -- 1.1.7). SERCA regulation -- 1.1.8). Calcium removal from sarcomere -- 1.2). Types of skeletal muscles fibers -- 1.2.1). Type I (slow oxidative) -- 1.2.2). Type II-A (fast oxidative) -- 1.2.3). Type II-B (fast glycolytic) -- 1.3). Types of muscle contraction -- 1.4). Difference in muscle type mechanisms -- 1.4.1). Cardiac vs SkM -- 1.4.2). Smooth muscles vs SkM -- 1.5). Hibernation -- 1.6). Scope and rationale -- 1.6.1). Diet and temperature -- 1.6.2). Clinical relevance -- 1.7). Research objectives -- 1.8). References. Chapter 2. Pre-hibernation diet alters skeletal muscle relaxation kinetics, but not force development in torpid arctic ground squirrels -- 2.1). Abstract -- 2.2). Introduction -- 2.3). Materials and methods -- 2.3.1). Animals -- 2.3.2). Trapping -- 2.3.3). PUFA diet -- 2.3.4). Husbandry -- 2.3.5). Tissue collection -- 2.3.6). Preparation of skeletal muscles and assessment of functional performance -- 2.3.7). Inhibition of SERCA and RyR -- 2.3.8). Western blotting -- 2.3.9). Data analysis -- 2.3.10). Statistical analysis -- 2.4). Results -- 2.4.1). Contractile properties during progression through a torpor bout -- 2.4.2). Contractile and dietary properties -- 2.4.3). The effect of diet on protein expression -- 2.4.4). Temperature effects on inherent contractile properties -- 2.4.5). No change in temperature resilience between diet and torpor -- 2.5). Discussion -- 2.5.1). Critique of approach -- 2.5.2). Influence of diet and torpor -- 2.5.3). Effects of hypothermia -- 2.5.4). Effects on the expression of the SERCA/SLN proteins -- 2.6). Conclusion -- 2.7). Prospectus -- 2.8). Declaration of competing interest -- 2.9). Acknowledgments -- 2.10). References. Chapter 3. Hibernation in arctic ground squirrels reduces skeletal muscle fatigue resistance and outperforms Sprague Dawley rats -- 3.1) Abstract -- 3.1) Introduction -- 3.2) Materials and methods -- 3.2.1) Animals -- 3.2.2) Trapping -- 3.2.3) Husbandry -- 3.2.4) Tissue collection -- 3.2.5) Preparation of skeletal muscles -- 3.2.6) Force frequency (identification) protocol (FFP) -- 3.2.7) Fatigue protocol (FP) -- 3.2.8) Equilibration protocol (EP) -- 3.2.9) Functional performance assay -- 3.2.10) Data analysis -- 3.2.11) Statistical analysis -- 3.3) Results -- 3.3.1) SkM fatigue resistance/ contractile performance across season & species -- 3.4) Discussion -- 3.4.1) Seasonal alteration in fatigue resistance -- 3.4.2) Effects of hypothermia on inherent fatigue resistance -- 3.5) Conclusion -- 3.6) Prospectus -- 3.7) Declaration of competing interest -- 3.8) Acknowledgments -- 3.9) References. Chapter 4. Method of Analysis -- 4.1) Abstract -- 4.2) What is muscle fatigue? -- 4.3) Muscle fatigue experimental protocols -- 4.4) Parameters of fatigue measurement -- 4.5) Surgical methods -- 4.5.1) Preoxygenated Ringer solution preparation -- 4.5.2) Euthanasia -- 4.5.3) Tissue harvest -- 4.5.4) Strip preparation -- 4.5.5) Temperature control -- 4.6) Contractile/ fatigue resistance parameter(s) -- 4.6.1) Max force production -- 4.6.2) Rate of force development -- 4.6.3) Time to peak -- 4.6.4) Rate of relaxation -- 4.6.5) Half relaxation time -- 4.6.6) Calcium/force transient -- 4.7) Raw data processing -- 4.7.1) Multi-point calibration -- 4.7.2) Data point selection -- 4.7.3) Normalization of the data -- 4.7.4) Ratio determination of fatigue resistance -- 4.8) Statistical analysis -- 4.8.1) Kruskal-Wallis test -- 4.8.1) Mann-Whitney U test -- 4.9) Strengths and limitations -- 4.9.1) Strengths -- 4.9.1) Limitations -- 4.10) References. Chapter 5. General conclusion and future directions -- 5.1) Conclusion -- 5.2) Future directions -- 5.3) References. | en_US |
| dc.language.iso | en_US | en_US |
| dc.subject | Muscle contraction | en_US |
| dc.subject | Nutrition | en_US |
| dc.subject | Musculoskeletal system | en_US |
| dc.subject | Unsaturated fatty acids | en_US |
| dc.subject | Muscles | en_US |
| dc.subject | Muscle performance | en_US |
| dc.subject | Arctic ground squirrel | en_US |
| dc.subject | Hibernation | en_US |
| dc.subject.other | Doctor of Philosophy in Biochemistry and Neuroscience | en_US |
| dc.title | Effects of diet and hibernation in skeletal muscle performance | en_US |
| dc.type | Dissertation | en_US |
| dc.type.degree | phd | en_US |
| dc.identifier.department | Department of Chemistry and Biochemistry | en_US |
| dc.contributor.chair | Oliver, S. Ryan | |
| dc.contributor.chair | Drew, Kelly L. | |
| dc.contributor.committee | Weltzin, Maegan D. | |
| dc.contributor.committee | Kuhn, Thomas B. |
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