Tag: Hans Dreyer

Impact of a Single Bout of Blood Flow Restriction Exercise on Muscle Stem Cells

Presenter(s): Jaslena Gill — Human Physiology

Co-Presenter(s): Noah Lovgren

Faculty Mentor(s): Hans Dreyer

Session: (In-Person) Poster Presentation

Blood flow restriction exercise (BFR-Ex) is a form of low-load exercise that restricts extremity blood flow. BFR-Ex has been shown to cause an increase in muscle mass, strength, and muscle stem (satellite) cells. Satellite cells are critical for muscle homeostasis and regeneration. The loss of satellite cells precedes Type II muscle cell decline, a process called sarcopenia, affecting up to 50% of the elderly. The purpose of this study is to determine the effects of a single bout of BFR-Ex on muscle structure 24 hours and 7 days later in young and older adults. We expect satellite cell numbers will increase 24 hours post-exercise and return to normal by 7 days. We also expect signs of muscle cell denervation, cell membrane damage, and recent repair of muscle damage at 7 days post-exercise. Subjects (18-40 yo, 6 female, 6 male) will participate. Subjects will have a baseline biopsy on the left leg followed by a single bout of BFR-Ex on the right leg. Post-BFR-Ex biopsies will be obtained on the right leg after 24 hours and 7 days. Immunohistochemistry will be used to determine cross-sectional area, satellite cell number, fiber type, muscle nuclei, and centrally located nuclei. This will allow us to measure muscle cell denervation, cell membrane damage, and recent repair of muscle damage. To date, one subject has completed the protocol, one has consented, and another will be consented this week. Tissue samples are currently being processed.

Histological Characterization of Changes in Skeletal Muscle during Tourniquet Induced Ischemia and Reperfusion

Presenters: Aaron Boothby and Arman Ameripour

Mentor: Hans Dreyer

PM Poster Presentation

Poster 4

Orthopedic surgeons often utilize a tourniquet during surgical procedures to minimize blood loss and to maintain a clear surgical field. Current clinical dogma is that tourniquet use for up to two hours has no lasting negative impact on muscle tissue. However, our lab has recently shown that tourniquet use downregulates proteins regulating components of the cap-dependent translation initiation and elongation complex and upregulates proteins regulating catabolic pathways (MuRF1 and MAFbx) as well as stress activated protein kinases (SAPK/JNK). Tourniquet induced-anoxia reduces the rate of muscle cell metabolism. Studies have shown that the resultant ATP deficit leads to failure of the sodium potassium pump and subsequently to the building up of intracellular sodium and chloride ions. This change in ionic concentration causes water uptake and cell swelling. In this study, we used immunohistochemistry to analyze morpho- logical changes in muscle cells resulting from tourniquet-induced ischemia and subsequent reperfusion. We hypothesize that tourniquet use will result in muscle cell swelling. Preliminary data supports our hypothesis. Further research is needed to examine the role that cell swelling may play in post-surgical atrophy.

Dietary Intake and its Effect on Muscle Atrophy Post Total Knee Arthroplasty

Presenter: Alexander Robinson

Mentor: Hans Dreyer

AM Poster Presentation

Poster 39

Post-operative muscle loss has been singled out as the greatest contributor to long-term strength deficits, explaining 77% of muscle weakness 1-3 years after total knee arthroplasty (TKA). One possible factor contributing to significant and rapid loss of muscle occurring within two weeks of surgery is reduced dietary intake during which our body breaks down skeletal muscle protein in order to liberate amino acids for use as gluconeogenic precursors in the liver. Therefore, inadequate dietary intake may exacerbate muscle loss following surgery. I hypothesize that subjects who maintain a protein intake ≥ .8g/kg or ≥ 2000 calories a day will experience less muscle atrophy following surgery. For this study, subjects completed a total of three 3-day food logs at baseline, 2 and 6 weeks post-TKA. Furthermore, at these same time points bilateral quadriceps muscle volume was determined using MRI. Also baseline and 6-week whole body DEXA scans were performed to determine changes in lean tissue and fat mass. Our preliminary data show at two weeks following surgery caloric and protein ingestion has decreased. Also there is a 16% decrease in lean muscle mass of the quadriceps two weeks after surgery, and this decrease may be partially explained by insufficient dietary intake.

Ischemia Induced ER Stress in Skeletal Muscle Cells during Total Knee Arthroplasty Upregulates Proteins Involved with the Unfolded Protein Response

Presenter: Ryan Boileau

Mentor: Hans Dreyer

AM Poster Presentation

Poster 3

Estimated to be performed 3.48 million times annually by 2030, Total Knee Arthroplasty (TKA) is the most common surgery to remediate chronic osteoarthritis in older adults. During surgery, blood flow is occluded to the operative leg resulting in anoxic conditions within the distal tissues. We have previously shown that proteins regulating cap-dependent translation initiation and elongation are downregulated and components of the catabolic and cell stress pathways are upregulated during ischemia and reperfusion. The purpose of this study was to further characterize the effects of anoxia in muscle cells on proteins controlling components of the ER stress pathway, i.e., the unfolded protein response (UPR). Muscle biopsies were obtained at baseline (before TKA surgery), maximal ischemia (before tourniquet release), and reperfusion. Preliminary results suggest an increase in cytoplasmic levels of downstream targets of the UPR (ATF4, CHOP, JNK, and Bcl-2). Further research will elucidate protein targets for preconditioning therapies that may ameliorate the UPR in an attempt to mitigate the substantial muscle atrophy following this increasingly common procedure performed in older adults.

Determining the Effects of Essential Amino Acid Supplementation for Total Knee Arthroplasty Patients

Presenter : Caitlin Gibson

Mentor : Hans Dreyer

Major : Human Physiology

Poster 18

Osteoarthritis affects 60% of the US population over 65 years of age. Total Knee Arthroscopy (TKA), used to mitigate osteoarthritis knee pain, is the leading cause of hospitalization for adults, ages 45-84 years old. The most significant clinical barrier following TKA surgery is persistent muscle atrophy and weakness. Previous research has shown that essential amino acid (EAA) ingestion is a potent means to stimulate muscle protein synthesis in older adults. PURPOSE: To determine the effects of twice-daily ingestion of 20g of EAA for 1 week prior to, and for 2 weeks post-TKA, on muscle mass, strength, and functional mobility. METHODS: Magnetic resonance imaging (MRI), isometric quadriceps strength and functional mobility were obtained at baseline, 2 and 6 weeks post-TKA from older adults supplemented with EAA or placebo. RESULTS: Quadriceps muscle atrophy was greater in the placebo group at 2 and 6 weeks post-surgery. The intervention group had significantly less loss in quadriceps strength and performed significantly better at 2 and 6 weeks post-surgery on functional mobility tests. CONCLUSIONS: Our results show that TKA surgery is associated with significant muscle atrophy, declines in muscle strength and reductions in functional mobility. Our findings will help us to better understand the potential for EAA supplementation in order to attenuate muscle loss and boost recovery of muscle mass, strength and function follow- ing TKA in older adults.

The effects of leucine, arginine and lysine, and HMB stimulation of anabolic and catabolic mechanisms on myoblasts

Presenter(s): Lillian Wheary

Co Presenter(s): Sam Kirby, Nick Belair

Faculty Mentor(s): Hans Dreyer & Doug Foote

Poster 27

Session: Sciences

Total knee arthroplasty (TKA) procedures are projected to increase nearly seven-fold to 3.4 million per year in the U.S. by 2030. Nearly all patients undergoing this surgery experience some degree of muscle loss during the first two weeks after surgery. Although effective at eliminating osteoarthritic pain, muscle atrophy and functional deficits persist. Essential amino acid (EAA) supplementation has been successful used by us in mitigating muscle atrophy after TKA. To understand how EAAs work at the cellular level, we isolated myoblasts from biopsies. Our goal was to model the cellular responses to anabolic stimuli using cell culture methods. Our objectives were: 1) isolate myoblasts from biopsies with >80% purity, 2) measure changes in anabolic mTORC1 response to anabolic amino acids (leucine, lysine and arginine (LRK)) ± insulin, and 3) measure changes to the leucine metabolite hydroxy-beta-methylbutyrate (HMB). Cells were seeded and myogenic purity confirmed via immunocytochemistry (ICC). Phosphorylation status of anabolic and catabolic signaling were determined. Preliminary results: isolating myoblasts from older muscle is more difficult than young controls. LRK+I produced a significant increase in rpS6 and Akt phosphorylation while no change was detected when myoblasts were incubated with HMB. Additional research is needed to refine our isolation methods and to better understand the mechanism(s) through which amino acids can help to maximally preserve muscle mass after common orthopedic procedures in older adults. If successful, recovery strategies such as amino acid supplementation will improve functional mobility following surgery and enhance long-term quality of life for these older individuals.

Differences in Old and Young Patient-Derived Myotubes Response to Amino Acid Stimulation

Presenter(s): Jeanette Helgerson—Human Physiology

Faculty Mentor(s): Hans Dreyer, Doug Foote

Session 3: The Substance of Us

Human muscle cell growth is regulated through the protein complex mTOR, the mammalian target of rapamycin, which is activated by nutrients such as amino acids and growth factors such as insulin . We wanted to know if there were differences in how old and young patient derived muscle cells responded to amino acids, particularly how the mTOR cascade was affected . The mTOR response to amino acids has been studied in many types of cells, but this study’s approach using patient derived human skeletal muscle cells to analyze mTOR response has yet to be explored . Using purified samples of these patient derived cells, a mixture of amino acids (LRK) that are known to activate mTOR were given, and the cellular signaling of certain proteins were quantified to measure mTOR activation . Both young and old patient derived cells were given these conditions and the averages of the groups were compared . This research is currently ongoing, so not all of the data is available yet . Knowing the differences in how young and old patient derived cells respond to amino acids is important because it could help alleviate muscle loss . Muscle loss shortens lifespans and diminishes the quality of life for many people, so understanding the underlying mechanisms of how to gain muscle back after the aging process, injury, or surgery, is imperative .