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Exercise induces morphological and metabolic adaptations that are highly specific to the mode of exercise training. These specific phenotypical changes are due to an equally specific molecular response that may depend on the activation and coordination intramuscular signaling pathways. Just as metabolic and morphological changes are influenced by the mode of exercise training, the signaling pathways that mediate exercise adaptation may also be directly related to the training status of skeletal muscle. For example, pre-conditioned skeletal muscle may exhibit a specific intracellular signaling response to an acute bout of exercise that is dependent on past training history. Both Akt (protein kinase B) and extra-cellular signal-related kinase (ERK 1 /2) have been shown to be phosphorylated in response to an acute bout of resistance exercise in human skeletal muscle and have been suggested to mediate the adaptive response to exercise. The purpose of this investigation was to examine the response of Akt and ERKI/2 to an acute bout of resistance exercise in three groups with distinctly different exercise training backgrounds. Twenty one subjects performed 3 sets of 10 repetitions of knee extension exercise at 70% 1-RM. The subjects consisted of a resistance-trained group (RE) (n=7), endurance trained group (END) (n=7) and a sedentary group (SED) (n=7). Muscle biopsies were taken from the vastus lateralis muscle before, immediately after, and 10 min post-exercise and were analyzed for phosphorylation of Akt and ERK1/2. ERK1/2 phosphorylation increased 47%, and 54% from pre-exercise to immediately post-exercise in the SED and RE groups respectively (p < 0.05). ERK1/2 phosphorylation increased 95%, 196%, and 47% from pre-exercise to 10 min post-exercise in the SED, RE, and END groups, respectively. (p < 0.05). The magnitude of ERK1/2 phosphorylation 10 min post-exercise was different between each group and may be linked to the group's training status. (p < 0.05) Akt phosphorylation decreased 42% and 37% from pre-exercise to immediately post-exercise in the SED and END group, respectively (p < 0.05). There was a 40 % increase in Akt phosphorylation from immediate post-exercise to 10 min post-exercise in the END group. In conclusion, training status appears to influence the magnitude and time course of activation of both Akt and ERK1/2 in response to an acute bout of resistance exercise. The immediate response of both ERK1/2 and Akt may play a key role in the adaptive response of skeletal muscle ultimately resulting in metabolic and morphological changes that are dependent on the past training history of the individual. / School of Physical Education, Sport, and Exercise Science

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Little is known about protein profiles in slow-twitch (MHC I) and fast-twitch (MHC IIa and MHC IIx) human skeletal muscle fibers. Therefore we developed a method of assessing fiber type specific protein content across the continuum of human skeletal muscle fiber types. The method presented here combines the advantages of SDS-PAGE for fiber typing with the common Western Blot (WB) technique. Individual vastus lateralis muscle fibers (n = 264) were isolated and clipped into two portions, one for fiber-typing and one for protein identification. Following fiber type determination, WB destined fiber segments were combined into fiber type specific pools (20 fibers/pool) and assessed for GAPDH, actin, Citrate Synthase, and total p38 content. GAPDH expression was 69%, 92%, 159%, and 200% more abundant in MHC I/IIa, MHC IIa, MHC IIa/IIx, and MHC IIx pools when compared to MHC I, respectively. Inversely, Citrate synthase content was 526%, 497%, 316%, and 47% more abundant in MHC I, MHC I/IIa, MHC IIa, and MHC IIa/IIx when compared to MHC IIx, respectively. Similar to GAPDH, total p38 expression was 67% greater in MHC IIa versus MHC I fibers. These data establish a novel application of WB combined with SDS-PAGE for fiber type specific protein analysis in human skeletal muscle. These initial results show content of particular proteins exist in a hierarchal fashion throughout the continuum of human skeletal muscle fiber types. Application of these methods will enhance our understanding of skeletal muscle health profiles among physically active and clinically based populations. / Access to thesis permanently restricted to Ball State community only / School of Physical Education, Sport, and Exercise Science

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Cyclooxygenase (COX) is the enzyme that catalyzes the rate-limiting step in prostaglandin (PG) synthesis. In skeletal muscle, PGF2a, has been shown to regulate protein synthesis, and ibuprofen and acetaminophen have been shown to block the normal increase in PGF2a and muscle protein synthesis following resistance exercise in humans. The purpose of this investigation was to determine the expression of the COX-1 (COX-1 variants: COX-1 v1, -1v2, -1 b,, -1 b2, and -1b3) and COX-2 isoforms following resistance exercise to help elucidate the isoform or variant through which PGF2a, ibuprofen, and acetaminophen regulate muscle protein synthesis. Human skeletal muscle biopsy samples were taken from 16 individuals (8M, 8F) before, 4 h, and 24 h following a single bout of resistance exercise and analyzed using real-time RT-PCR. COX-Iv1 and COX-1v2 were the most abundant COX mRNA before exercise and remained unchanged (P>0.05) following exercise (i.e., constitutively expressed). Relatively few individuals expressed the intron 1-retaining COX-1 b variants (COX-1 b,, - 1b2, and -1 b3) at any time point, and when expressed these variants were in very low abundance. COX-2 was not expressed in any subject before exercise, but increased significantly (P<0.05) at 4 and 24 h following exercise. These results suggest that the intron 1-retaining COX-1 b,, -1 b2, and -lb3 variants are likely not the COX through which PGF2a is produced to stimulate skeletal muscle protein synthesis. PGF2a, stimulation, as well as ibuprofen and acetaminophen inhibition of skeletal muscle protein synthesis likely work through COX-2, or one of the constitutively expressed COX-1 variants (COX-lv1 or -1v2). / School of Physical Education, Sport, and Exercise Science

Intramuscular connective tissue is critical in maintaining muscle structure and the transfer of force from contractile elements to the bone. We examined intramuscular connective tissue characteristics in young and old men and women, as well as men and women subjected to simulated microgravity. We hypothesized that intramuscular collagen content, collagen cross-linking and formation of advanced glycation endproducts of old individuals would be greater than young, and that intramuscular collagen content would be elevated following prolonged periods of unloading spanning 35, 60 and 90 days. Vastus lateralis muscle biopsies revealed that intramuscular collagen (Young: 9.6±1.1, Old: 10.2±1.2 ug•mg muscle wet wf-') and collagen cross-links (hydroxylysylpyridinoline, HP) (Young: 395±65, Old: 351±45 mmol HP•mol collagen-1) were unchanged (p>0.05) with aging. The advanced glycation endproduct, pentosidine, was increased (p<0.05) by 203% (Young: 5.2±1.3, Old: 15.9±4.5 mmol pentosidine•mol collagen"') with aging. With unloading, collagen content of the vastus lateralis was unchanged (p>0.05) following all time periods but was found to be elevated (p<0.05) in the soleus following 90 days of unloading. Furthermore, baseline collagen content was found to greater (p<0.05) in the soleus compared to the vastus lateralis. These results suggest the age related decline in whole muscle function is not related to increases in intramuscular collagen content or cross-linking but may be related to the accumulation of advanced glycation endproducts. Muscle function following unloading does not appear to be impacted by collagen content in the vastus lateralis but may play a role in the soleus. / School of Physical Education, Sport, and Exercise Science

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Thesis (MSc)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: Introduction: Exercise increases skeletal muscle glucose uptake via AMP-activated protein kinase (AMPK) activation and GLUT4 translocation from cytosol to cell membrane. It also promotes glucose utilisation in type 2 diabetic patients via increased insulin sensitivity. Insulin stimulates GLUT4 translocation by activating P13- kinase and protein kinase B (PKB/Akt). We therefore postulated that a connection exists between these two pathways upstream of GLUT4 translocation. Understanding this connection is important in the development of treatment strategies for type 2 diabetes. This exercise-induced increase in AMP-activated protein kinase (AMPK) activation can be mimicked by a pharmacological agent, 5'-aminoimidazole-4- carboxamide ribonucleoside (AlGAR), which is converted intracellularly into 5'- aminoimidazole-4-carboxamide-ribonucleosidephosphate (ZMP), an AMP analogue. Aim: To investigate the effect of two pharmacological AMPK-activating compounds, ZMP and AlGAR, on the phosphorylation of AMPK, the phosphorylation of PKB/Akt as well as possible feedback on insulin-stimulated glucose uptake and GLUT4 translocation. Materials and Methods: Adult ventricular cardiomyocytes were isolated from male Wistar rats by collagenase perfusion and treated with 1 mM AlGAR or 1 mM ZMP in the presence or absence of 100 nM insulin or 100 nM wortmannin, an inhibitor of P13- kinase. Glucose uptake was measured via eH]-2-deoxyglucose (2DG) accumulation. PKB/Akt and AMPK phosphorylation and GLUT4 translocation was detected by Western blotting. Purinergic receptors were blocked with 8-cyclopentyl-1,3- dipropylxanthine (8CPT) and the effect on AMPK phosphorylation noted. Certain results were confinned or refuted by repeating experiments using the isolated rat heart model. Results: AICAR and ZMP promoted AMPK phosphorylation. Neither drug increased glucose uptake but in fact inhibited basal glucose uptake, although GLUT4 translocation from cytosol to membrane occurred. Both compounds also attenuated insulin stimulated glucose uptake. Wortmann in abolished glucose uptake and PKB/Akt phosphorylation elicited by insulin while, in the presence of wortmannin, AICAR and ZMP increased levels of PKB/Akt phosphorylation. Although AICAR and ZMP increased glucose uptake in skeletal muscle, this was not seen in cardiomyocytes. However both compounds increased GLUT4 translocation, clearly demonstrating that translocation and activation of GLUT4 are separate processes. 8CPT had no effect on the phosphorylation of AMPK by either AICAR or ZMP indicating that there was no involvement of the purinergic receptors. Conclusion: Although AICAR and ZMP increase glucose uptake in skeletal muscle, this was not seen in cardiomyocytes. Conversely, both compounds inhibited both basal and insulin stimulated glucose uptake despite increasing GLUT4 translocation. Inhibition of PI3-kinase in presence or absence of insulin unmasked hitherto unknown effects of AICAR and ZMP on PKB phosphorylation. / AFRIKAANSE OPSOMMING: Agtergrond: Oefening verhoog skeletspier glukose opname via AMP-geaktiveerde protein kinase (AMPK) aktivering en GLUT4 translokering vanaf die sitosol na die selmembraan. Dit verbeter ook glukose verbruik in tipe 2 diabetes pasiënte via verhoogde insulien sensitiwiteit. Insulien stimuleer GLUT4 translokering deur P13- kinase en protein kinase B (PKB/Akt) te aktiveer. Dit word dus gepostuleer dat daar 'n verbinding tussen hierdie twee paaie, wat beide betrokke is by GLUT4 translokering, bestaan. Dit is belangrik om hierdie verbinding te verstaan aangesien dit in behandelingstrategieë van tipe 2 diabetes geteiken kan word. Die oefening geïnduseerde verhoging in AMPK aktivering, kan deur 'n farmakologiese middel 5'- aminoimidasool-4-karboksamied ribonukleosied (AICAR), wat intrasellulêr omgesit word na 5'-aminoimidasool-4-karboksamied-ribonukleosiedfosfaat (ZMP), 'n AMP analoog, nageboots word. Doel: Om die effek van twee farmakologiese AMPK-aktiveringsmiddels, AICAR en ZMP, op die fosforilering van AMPK en PKB/Akt, sowel as moontlike effekte daarvan op insulien-gestimuleerde glukose opname en GLUT4 translokering, te ondersoek. Materiale en Metodes: Volwasse ventrikulêre kardiomiosiete is uit manlike Wistar rotharte geïsoleer d.m.v kollagenase perfusies en behandel met 1 mM AICAR of 1 mM ZMP in die teenwoordigheid of afwesigheid van 100 nM insulien of 100 nM wortmannin. Glukose opname is gemeet via intrasellulêre [3H]-2-deoksiglukose akkumulasie; PKB/Akt en AMPK fosforilering sowel as GLUT4 translokering is bepaal deur Western blot analises. Purinergiese reseptore is geblokkeer met 8-siklopentiel- 1,3-dipropielxanthien (8CPT) en die effek daarvan op AMPK fosforilering genoteer. Ten einde resultate wat in die geïsoleerde kardiomiosiet-model verkry is, te bevestig, is sekere eksperimente in die geïsoleerde rothart herhaal. Resultate: Beide AIGAR en ZMP stimuleer AMPK fosforilering. Die middels kan nie glukose opname verhoog nie, inteendeel, basale glukose opname is onderdruk alhoewel GLUT4 translokering vanaf die sitosol na die selmembraan wel plaasgevind het. Wortmannin kon insulien gemedieerde glukose opname en PKB/Akt fosforilering onderdruk. In die teenwoordigheid van wortmannin het beide AIGAR en ZMP PKB/Akt fosforilering verhoog. Alhoewel beide AIGAR en ZMP glukose opname in skeletspier verhoog, was dit nie die geval in kardiomiosiete nie. Beide middels het wel GLUT 4 translokering verhoog, wat duidelik demonstreer dat die translokering en aktivering van GLUT4, verskillende prosesse is. 8GPT het geen effek gehad op die fosforilering van AMPK deur AIGAR of ZMP nie, wat bewys dat daar geen betrokkenheid van die purinergiese reseptore was nie. Gevolgtrekking: Alhoewel AIGAR en ZMP glukose opname in skeletspier verhoog is dit nie die geval in kardiomiosiete nie. Beide middels inhibeer basale en insuliengestimuleerde glukose opname maar stimuleer GLUT4 translokeering. Inhibisie van PI3-kinase in die teenwoordigheid of afwesigheid van insulien, ontmasker voorheen onbekende effekte van AIGAR en ZMP op PKB/Akt fosforilering.

The primary focus of this study was to determine basal levels of myogenic (MRF4, myogenin, MyoD), proteolytic (FOXO3A, atrogin-1, MuRF-1), myostatin, and mitochondrial (PGC-1α & Tfam) mRNA in elderly women before and after aerobic training. This approach was taken to gain insight into the molecular adaptations associated with our observed increases in whole muscle cross sectional area (CSA) (11%, p<0.05), knee extensor muscle function (25%, p<0.05) and aerobic capacity (30%, p<0.05) with training. Nine elderly women (71±2y) underwent muscle biopsies obtained from the vastus lateralis before and after 12-weeks of aerobic training on a cycle ergometer. Post training biopsy samples were acquired 48 hours after the last exercise session. Aerobic training reduced (p < 0.05) resting levels of MRF4 by 25% while myogenin showed a trend to decrease (p = 0.09) after training. FOXO3A expression was 27% lower (p < 0.05) while atrogin-1 and MuRF-1 were unaltered after training. Additionally, myostatin gene expression was decreased (p < 0.05) by 57% after training. Lastly, aerobic training did not alter PGC-1α or Tfam mRNA. These findings suggest that aerobic training alters basal transcript levels of growth related genes in skeletal muscle of older women. Further, the reductions in FOXO3A and myostatin indicate the aerobic training induced muscle hypertrophy in older women may be due to alterations in proteolytic machinery. / School of Physical Education, Sport, and Exercise Science