Thesis--University of Wisconsin--Madison. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 66-75).

Thèses (M.Sc.)--Université de Sherbrooke (Canada), 2004. / Titre de l'écran-titre (visionné le 20 juin 2006). Publié aussi en version papier.

Thesis (M.S.)--University of Wisconsin--Madison, 1980. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 64-66).

Ingestion of proteins with high leucine content during resistance training (RT) can augment hypertrophy. There are data suggesting that a leucine metabolite, β-hydroxy, β-methylbutyrate (HMB), may, however, be substantially more anabolic than leucine. Purpose: We aimed to test whether supplementation with HMB versus leucine, added to whey protein, would result in different muscle hypertrophy and strength gains in young men performing resistance training (RT). Methods: Twenty-six resistance-trained men (23 ± 2 y) performed 12 wk of RT with 3 phases. Phase 1: 8 wk of periodized RT (3 training sessions/wk). Phase 2: 2 wk overreaching period (5 sessions/wk). Phase 3: 2 wk taper (3 sessions/wk). Participants were randomly assigned to twice daily ingestion of: whey protein (25 g) plus HMB (1.5 g) (Whey+HMB; n=13) or whey protein (25 g) plus leucine (1.5 g) (Whey+Leu; n=13). Skeletal muscle biopsies were performed before and after RT. Measures of fat and bone-free mass (FBFM), vastus lateralis (VL) muscle thickness and muscle cross-sectional area (CSA – both by ultrasound), muscle fiber CSA, and 1-repetition maximum (1-RM) strength tests were determined. Results: We observed increases in FBFM, VL muscle thickness, muscle CSA and fiber type CSA and 1-RM strength, with no differences between HMB and leucine at any phase. Furthermore, no differences were observed in hormone concentrations between groups, or in time-by-group interactions in hormone concentrations at any phase of the RT program. Conclusion: HMB did not result in greater increases in any measure of muscle mass, strength, or hormonal concentration compared to leucine during 12 weeks of RT. / Thesis / Master of Science in Kinesiology / Whey protein supplementation following resistance training (RT) is an effective strategy to enhance RT-induced gains in skeletal muscle mass and strength. The anabolic properties of whey protein are attributed, in part, to the branched-chain amino acid leucine. Leucine is a substrate for protein synthesis and a potent signal that turns on the protein synthetic machinery. A metabolite of leucine, β-hydroxy, β-methylbutyrate (HMB) has been claimed to share similar or greater anabolic properties of leucine. Recently, supplementation with HMB during RT has been shown to result in large gains in muscle mass and strength. The purpose of this study was to examine whether HMB, versus leucine, added to whey protein, would result in different muscle hypertrophy and strength gains in young men during RT. Body composition and maximum strength tests were performed before, during and after 12 weeks of RT. Following 12 weeks of RT, both groups experienced similar gains in muscle mass and strength. We observed that HMB is no more effective in stimulating RT-induced hypertrophy and strength gains than its parent amino acid, leucine.

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A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2012 / The thioredoxin-like (Trx-like) fold is preserved in various protein families with diverse functions despite their low sequence identity. Glutathione transferases (GSTs) are characterised by a conserved N-terminal domain with a thioredoxin–like βαβαββα secondary structure topology and an all alpha-helical domain. GSTs are the principal phase II enzymes involved in protecting cellular macromolecules from a wide variety of reactive electrophilic compounds. It catalyses the conjugation of reduced glutathione (GSH) to an electrophilic substrate to form a hydrophilic and non-toxic compound. The binding site for GSH (G-site) is located in the N-terminal domain of GSTs. The sequence identity within members of the Trx-like superfamily is low; however, the members of this family fold into a conserved βαβαββα topology. It, therefore, seems reasonable that there are topologically conserved residues within this fold whose main role is to drive folding and/or maintain the structural integrity of the Trx-like fold. Structural alignments of the N-subdomain (βαβ motif) of the GST family shows that Leu7 in β1 and Leu23 in α1 are topologically conserved residues. The Leu7 side chain is involved in the packing of α1β1α2 and α3, whilst Leu23 is mainly involved in van der Waals interactions with residues in α1 and the loop region connecting α1 and β2. Taking into account the types of interaction that both Leu7 and Leu23 are involved in, as well their location in close proximity to the G-site, it was postulated that both these residues may play a role in the structure, function and stability of the GST family of proteins. Leu7 and Leu23 are not directly involved in the binding of GSH but they could be important in maintaining the G-site in a functional conformation via correct packing of the Nsubdomain. The homodimeric human class Alpha of GST (hGSTA1-1) was used as the representative of the GST family to test this hypothesis. The bulky side chains of Leu7 and Leu23 were replaced with a less bulky alanine residue to prevent altering the hydrophobicity of the βαβ motif. The effect of the mutation on the structure, function and stability of hGSTA1-1 was, therefore, studied in comparison with the wild-type using spectroscopic tools, X-ray crystallography, functional assays and conformational stability studies. The impact of the mutations on the structure of the enzyme was determined using spectroscopic tools and X-ray crystallography. The X-ray structures of the L7A and L23A mutants were resolved at 1.79 Å and 2.2 Å, respectively. Analysis of both X-ray structures shows that the mutation did not significantly perturb the global structure of the protein, which correlates with far-UV CD and intrinsic fluorescence spectroscopic data. In addition, structural alignments using the C-alpha gave root mean square deviation (r.m.s.d) values of 0.63 Å (L7A) and 0.67 Å (L23A) between the wild-type and mutant structures. However, both the L7A and L23A structures showed the presence of a cavity within the local environment of each mutation. The functional properties of the mutants were also similar to those of the wild-type as determined by specific activity and 8-anilino-1-naphthalene sulfonate (ANS)-binding, indicating that Leu7 and Leu23 are not involved in the function of hGSTA1- 1. The conformational stability of L7A and L23A proteins was probed using thermal-induced unfolding, pulse proteolysis and urea-induced equilibrium unfolding studies. The thermal stability of L7A and L23A hGSTA1-1 was reduced in comparison to the wild-type protein. This was consistent with proteolytic susceptibility of L7A and L23A proteins which indicates that both mutants are more prone to thermolysin digestion when compared to wild-type hGSTA1-1. This also correlates with urea-induced equilibrium studies. The ΔG(H2O) value (23.88 kcal.mol-1) for the wild-type protein was reduced to 12.6 and 10.49 kcal.mol-1 in L7A and L23A hGSTA1-l, respectively. Furthermore, the m-values obtained for the L7A and L23A proteins were 1.46 and 1.06 kcal.mol-1.M-1 urea, respectively; these were much lower than that obtained for the wild-type protein (4.06 kcal.mol-1.M-1 urea). The low m-values obtained for the mutant proteins indicated that the cooperativity of hGSTA1-1 unfolding was significantly diminished in both mutations. The results obtained in this study indicate that the topologically conserved Leu7 and Leu23 in the N-subdomain of hGSTA1-1 play a crucial role in maintaining the structural stability of the thioredoxin-like domain and are not involved in the function of the enzyme.

Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / Alterations in protein metabolism (determined by the utilization of DL-Leucine-4,5-H3HCl) were studied autoradiographically in the ventral and dorsal cochlear nuclei of rats, following partial destruction of the cochlea and intense acoustic stimulation. The auditory stimulation of 600 cps at 99-103 db was presented chronically (one hour a day for six weeks) and acutely (two hours only). Each animal was injected intraperitoneally 1.87 mc of radioleucine in two doses (1.00 mc and 0.87 mc) with an interval of 30 minutes. After the second injection 30 minutes were allowed, thus permitting a total of 60 minutes for exchange of the radiochemical. Animals from the surgical, chronic stimulation and control groups rested during the exchange period, whereas animals from the acute stimulation group were subjected to the intense auditory stimulation [TRUNCATED] / 2031-01-01

Leucine injections directly into the brain decrease food intake whereas supplementation of this amino acid in a diet has a negligible effect on food intake. We sought to investigate why orally supplemented leucine is ineffective as an anorexigen. We found that mice consuming leucine exhibited increased cFos immunoreactivity in the ARC and PVN of hypothalamus, areas controlling energy balance. However, real time- PCR analysis of the hypothalamic tissue in mice that were exposed to oral leucine showed changes in expression of genes involved in the regulation of energy balance as well as those mediating feeding reward (TMEM18, MC4R, CRH, FTO, SLC6A15, DOR). This suggests that leucine consumption affects activity of not only brain pathways that control calorie intake, but also those that mediate eating for pleasure. Hence the lack of feeding response to leucine supplementation in a diet may stem from the simultaneous action of this amino acid at brain circuit promoting reward and energy homeostasis.

There is a saturable, dose-response relationship between the amount of protein ingested at a meal, the ensuing hyperaminoacidemia, and the subsequent skeletal muscle protein synthesis (MPS) response. Imposition of an external load, usually practiced as resistance exercise, on skeletal muscle is also a potent stimulus for increasing MPS and adds synergistically to the hyperaminoacidemia-induced rise in MPS. The current thesis examined the potential for meal-focused protein/leucine intake strategies, alone and in combination with resistance exercise, to augment MPS in older men. MPS was measured acutely (hours) using the continuous infusion of L-[ring-13C6]phenylalanine (Study 1) or over longer-term, integrated periods via ingestion of deuterated water (Study 2: 2-wk and Study 3: 3-d) while participants were free-living. In Studies 1 and 2 we examined whether a balanced versus a skewed pattern of protein intake across daily meals would enhance MPS during energy restriction (ER) in overweight/obese older men. Study 1 showed that a balanced consumption of protein during ER stimulated acute (%/h) myofibrillar protein synthesis (MyoPS) more effectively than a traditional, skewed distribution. Combining resistance training (RT) with a balanced protein intake pattern restored the lower acute rates of MyoPS during ER to the higher levels observed in energy balance. Study 2 showed no effect of daily protein intake pattern during ER on longer-term integrated MyoPS (%/d). However, the inclusion of RT during ER enhanced integrated MyoPS and the synthesis of numerous individual contractile, sarcoplasmic and mitochondrial skeletal muscle proteins with both protein intake patterns. Study 3 showed that leucine co-ingestion with daily meals enhanced integrated (%/d) MyoPS in healthy older men who were in energy balance and was equally effective among those consuming higher (1.2 g/kg/d) and lower (0.8 g/kg/d) protein intakes. Furthermore, the stimulatory effect of leucine co-ingestion on integrated MyoPS was further potentiated with the performance of resistance exercise. Collectively, these studies support the potential for per-meal recommendations, optimizing the protein dose consumed on a per-meal basis and leucine co-ingestion with meals, to augment MyoPS in older men, especially when combined with RT. These data have implications for recommendations to optimize MyoPS and possibly muscle mass in aging persons. / Thesis / Doctor of Philosophy (PhD)

No description available.