Deficits in skeletal muscle mitochondrial metabolism are associated with a wide variety of chronic skeletal muscle and metabolic-related diseases, including diabetes and sarcopenia. Even in patients with advanced skeletal muscle-related diseases, exercise is a well-established method to improve skeletal muscle mitochondrial metabolism, culminating in enhanced whole-body metabolism and decreased disease severity. In response to exercise, there is an increase in reactive oxygen species (ROS) production. Historically, ROS were solely considered to drive disease development. However, ROS are also required for physiological adaptation and many questions still remain regarding their downstream pathways. One significant producer of skeletal muscle ROS with exercise is Nadph oxidase 4 (Nox4). Nox4 is unique compared to other Nox members as it predominantly produces hydrogen peroxide (H2O2), an effective signaling molecule. Here we demonstrate an essential role for Nox4 in mediating the beneficial effects of exercise. This work will contribute to our understanding of physiological ROS and their downstream targets by identifying a novel role for Nox4 in exercise adaptation. Further defining the molecular events that promote exercise adaptation will be essential for formulating new treatment strategies for patients with chronic metabolic diseases. / Doctor of Philosophy / Exercise is a widely effective tool for both preventing and reversing disease. Even patients with advanced skeletal muscle and metabolic-related diseases can benefit from continual and repeated exercise training. While decades of work have supported the effectiveness of exercise as a therapeutic intervention, the mechanistic understanding of what occurs at the cellular level remains incomplete. Here, we elucidate a novel pathway mediating important metabolic adaptations to exercise. In response to exercise stress, reactive oxygen species (ROS) are produced in skeletal muscle. ROS facilitate metabolic adaptations to meet the body's need for increased energy. One significant source of ROS comes from Nadph oxidase 4 (Nox4) which plays an essential role in metabolic regulation. The skeletal muscle metabolic response to stress is largely dependent on adaptations that include changes in gene expression, substrate oxidation, and mitochondrial metabolic adaptations. These mitochondrial adaptations include mitochondrial recycling after exercise in skeletal muscle (referred to as mitophagy). We have shown that Nox4 increases the expression of a subset of metabolic genes, is required for substrate oxidation after exercise, and is important for exercise-induced mitophagy.

Consumers are often confused and reluctant to purchase products from fresh retail meat counters that exhibit significant color variations. This hesitation to purchase results in annual profit loss to the pork industry. Processes to minimize color variation remain a major focus of the industry and many meat science programs across the globe. Previously, we found inherent muscle characteristics contribute to variations in pork quality but these characteristics fail to explain the high frequency of two-toning and other pork quality defects routinely occurring in many hog processing facilities. Therefore, we hypothesized harvesting practices, such as scald alter color across muscles of the ham. Scald time was initially investigated using 32 carcasses subjected to either a 4 (n=16) or 8 (n=16) min scald time. Samples were collected before or after scalding and at 24 hrs. A 50% reduction in scald time resulted in (p < 0.0001) lighter muscle color (L*) early postmortem, although the 8 min scald treatment was lighter (p < 0.005) at 24 hrs. Although differences in pH (p < 0.0001) and color were noted, ultimate carcass temperature was not affected. To that end, we moved to validate our hypothesis in an industrial plant setting. Carcasses (n=200) were assigned treatments of 6.5 or 7.5 min scald times, and SM muscle samples were collected at 24 hrs. Surprisingly, the shorter scald time resulted in (p < 0.05) a lighter color, contradicting our first study. To explore this color issue further, we uncoupled scald from the dehairing process. To achieve this goal, carcasses (n=24) were assigned to either an 8 or 16 min time to dehair, with or without scalding. Protracted time to dehair resulted in higher ultimate pH (p < 0.005) and less color variation across the muscle (p < 0.05). Though a color gradient remained, the variation across the muscle was reduced by increasing time to dehair. These data show time to dehair affects pork quality development and suggest that delaying time to physical manipulation of the carcass may improve pork color, thus increasing consumer acceptance. / Master of Science

Commercial hams display variation in color uniformity across the cut surface, especially the semimembranosus (SM) muscle. This variation in fresh ham color, or two-toning, persists through further processing and contributes to production of a less desirable end product. In an attempt to understand the underlying source of this color variation, we evaluated the differences in muscle fiber-type composition and glycolytic metabolism in the SM muscle of fresh hams differing in color uniformity. Fifty-eight fresh SM muscles, ranging in color, were selected at 24 h postmortem and each partitioned into four distinct regions and three color classes based on color uniformity in the caudal region. The L* (lightness) values were greatest and a* (redness) values lowest in the most caudal portions of the muscle. The caudal portion also exhibited the lowest ultimate pH (P < 0.0001), lowest myoglobin (P < 0.05), greatest glycolytic potential (GP) (P < 0.0001) and the lowest myosin heavy chain type I isoform (P < 0.0001) abundance of all regions in 'normal' colored hams. After segregating based on L* values, the caudal region had identical pH, GP, LDH, and MyHC-I, despite significant differences in L* (P < 0.0001). These data show the most caudal aspects of the SM are indeed more prone to adverse postmortem metabolism and suggest that inherent differences in muscles of the ham may make some areas of the ham more vulnerable to temperature abuse during harvesting. / Master of Science

Title: Muscle metabolism and its effect on physical condition in patients with chronic renal failure receiving hemodialysis Objective: Assess the status of muscle metabolism in patients starting hemodialysis and patients receiving hemodialysis long time, to determine some changes in muscle metabolism in both groups in the time period and ultimately assess its impact on physical condition and quality of life of hemodialysis patients. Method: Fill anamnestic questionnaire and examination of body composition using bioimpedence device (BCM) in the group of patients with chronic renal failure who are beginning to be treated with hemodialysis and a group of patients treated with hemodialysis for several years. Compare the results of both groups. To obtain additional information from medical records. Results: It was found that hemodialysis therapy affects the status of muscle metabolism in terms of reducing muscle mass (LTM). The dependence of LTM, however, the duration of hemodialysis treatment assays. The study showed that if patients are nutritionally stable and regularly engaged in some physical activity, loss of muscle mass is lower than in individuals who have a passive way of life. Keywords: chronic renal failure, hemodilysis, muscle metabolism, physical condition

No músculo esquelético (ME) resistente à insulina, a disponibilidade elevada de ácidos graxos (AGs) livres observada na obesidade provoca alterações na função mitocondrial. Sendo os microRNAs (miRs) moléculas recentemente apontadas na regulação gênica de vias metabólicas, nosso objetivo foi investigar em ME de camundongos com resistência à insulina (RI) induzida por dieta hiperlipídica durante 8 semanas, tratados com fenofibrato (CF e HF) ou metilcelulose (veículo; grupos C e H) nas duas semanas antes do sacrifício, se os miRs-1a, 133a/b, 206, 208b, 499 e miR-223 participam da patogênese da RI. O quadro de RI foi induzido no grupo H e o fenofibrato reverteu parcialmente a RI (grupo HF) observada através das alterações em parâmetros metabólicos e enzimáticos, que parecem ser mediados pelo miR-1a regulando a proteína AMPK&#945;2. O aumento na transcrição de AMPK&#945;2 ativa processos catabólicos tais como a captação de glicose e oxidação de AGs, sendo considerada a principal enzima reguladora do metabolismo celular ao estimular a expressão de genes mitocondriais via PGC-1&#945;. / In skeletal muscle (SM) tissue, evidences suggest that the high availability of free fatty acids (FFAs) observed in obesity plays a central role in the development of insulin resistance (IR) by causing changes in mitochondrial function. Since microRNAs (miRs) are recently identified molecules acting as gene regulators of metabolic pathways, we aimed to investigate in SM of insulin resistant mice induced by 8 weeks of high-fat diet (HFD) feeding, treated with fenofibrate (CF and HF) or metilcelulose (vehicle, C and H) two weeks before euthanasia, if miRs-1a, 133a/b, 206, 208b, 499 and 223 are involved in IR pathogenesis. IR was induced after 8 weeks of HFD (H), and fenofibrate treatment (HF) partially reverted this condition by causing alterations on metabolic and enzymatic parameters, which seems to be mediated by miR-1a regulating AMPK&#945;2 protein. AMPK&#945;2 increased translation active catabolic processes such as glucose uptake and FFAs oxidation, being considered the main regulator of cell metabolism by stimulating mitochondrial genes expression via PGC-1&#945;.

No músculo esquelético (ME) resistente à insulina, a disponibilidade elevada de ácidos graxos (AGs) livres observada na obesidade provoca alterações na função mitocondrial. Sendo os microRNAs (miRs) moléculas recentemente apontadas na regulação gênica de vias metabólicas, nosso objetivo foi investigar em ME de camundongos com resistência à insulina (RI) induzida por dieta hiperlipídica durante 8 semanas, tratados com fenofibrato (CF e HF) ou metilcelulose (veículo; grupos C e H) nas duas semanas antes do sacrifício, se os miRs-1a, 133a/b, 206, 208b, 499 e miR-223 participam da patogênese da RI. O quadro de RI foi induzido no grupo H e o fenofibrato reverteu parcialmente a RI (grupo HF) observada através das alterações em parâmetros metabólicos e enzimáticos, que parecem ser mediados pelo miR-1a regulando a proteína AMPK&#945;2. O aumento na transcrição de AMPK&#945;2 ativa processos catabólicos tais como a captação de glicose e oxidação de AGs, sendo considerada a principal enzima reguladora do metabolismo celular ao estimular a expressão de genes mitocondriais via PGC-1&#945;. / In skeletal muscle (SM) tissue, evidences suggest that the high availability of free fatty acids (FFAs) observed in obesity plays a central role in the development of insulin resistance (IR) by causing changes in mitochondrial function. Since microRNAs (miRs) are recently identified molecules acting as gene regulators of metabolic pathways, we aimed to investigate in SM of insulin resistant mice induced by 8 weeks of high-fat diet (HFD) feeding, treated with fenofibrate (CF and HF) or metilcelulose (vehicle, C and H) two weeks before euthanasia, if miRs-1a, 133a/b, 206, 208b, 499 and 223 are involved in IR pathogenesis. IR was induced after 8 weeks of HFD (H), and fenofibrate treatment (HF) partially reverted this condition by causing alterations on metabolic and enzymatic parameters, which seems to be mediated by miR-1a regulating AMPK&#945;2 protein. AMPK&#945;2 increased translation active catabolic processes such as glucose uptake and FFAs oxidation, being considered the main regulator of cell metabolism by stimulating mitochondrial genes expression via PGC-1&#945;.

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<p>Under hypoxia mammals face many challenges, especially in terms of energy production. To conserve O2, mammals may enter a hypometabolic state or rely more heavily on anaerobic metabolism. However, the latter strategy is not a viable option during chronic hypoxia and other cellular changes are needed. Under chronic hypoxia, mammals have been predicted to alter their metabolic machinery in an attempt to increase the efficiency of ATP production to reduce the amount of O2 used by the mitochondria. One way efficiency is believed to increase is through a change in the composition of cytochrome c oxidase (COX). Cell culture experiments have shown a decrease in the COX4-1 isoform and an increase in the COX4-2 isoform under hypoxia, leading to an increase in the reaction efficiency of COX. In the present study, I observed an increase in the mRNA levels of COX4-2 after 24hrs of hypoxia. However, this change was not mirrored by corresponding changes at the protein level. Further, I examined the phosphorylation state of pyruvate dehydrogenase (PDH) as an indicator of PDH activity. Under chronic hypoxia resting mice exhibited a significant rise in PDH phosphorylation. This increase may represent a decrease in PDH activity and a decreased reliance on carbohydrate derived acetyl-CoA.</p> <p>I also explored the effects plastic changes in muscle during chronic hypoxia had on muscle metabolism during acute exercise. In hypoxic post-exercise mice, a significant increase in muscle lactate levels was observed compared to rest. This rise was not present in control mice, suggesting that acclimated mice were relying more heavily on anaerobic metabolism. However, there were no significant changes in PDH phosphorylation in post-exercise mice which could help to explain elevated muscle lactate levels.</p> / Master of Science (MSc)

Está bem estabelecido que o diabetes melito está associado a uma série de distúrbios clínicos que envolvem a alteração no metabolismo de carboidratos, proteínas e lipídios. Tem-se observado aumento importante da morbidade e mortalidade associadas a esta doença, sendo que dentre as causas, em ambos os tipos de diabetes (1 e 2), têm-se o aumento de fatores de risco, como o sobrepeso ou obesidade e o estilo de vida sedentário. A erva-mate (Ilex paraguariensis) tem apresentado grande potencialidade para utilização preventiva e terapêutica no diabetes graças à atividade biotiva dos seus compostos (metilxantinas, polifenóis e saponinas), capazes de alterar o metabolismo tecidual energético tanto em protocolos experimentais com animais de laboratório quanto humanos. Assim sendo, o objetivo deste trabalho foi elucidar o efeito da administração do chá de mate em ratos Wistar diabéticos, tendo como foco o metabolismo tecidual muscular e hepático. Para tanto, ratos Wistar machos foram submetidos a indução do diabetes experimental com injeção de estreptozotocina (65 mg/kg, i.p.) e posteriormente tratados com o extrato aquoso de erva-mate através da água de beber por 30 dias. Ao final do tratamento, os animais foram eutanasiados e os tecidos (soro, músculo, fígado e tecido adiposo retroperitoneal e epididimal) foram coletados para análise. / There is a well known relationship between metabolic disturbances and clinical events related to diabetes and a dangerous prevalence increase worldwide for both types of this disease (diabetes type 1 and 2). This enhancement is caused by overweight, sedentary lifestyle and other risk factors associated to occidental habits. Yerba-mate (Ilex paraguariensis) has been presented a potential use to preventive and therapeutical aspects of diabetes due to its bioactive fractions (methylxanthines, saponins and polyphenols), which have a capability to improve energetic metabolism in murine models and human. The aim of this study was to elucidate the effect of yerba-mate on hepatic and muscle energetic metabolism of diabetic rats. To perform the diabetes inducing protocol Wistar rats received streptozotocin (65mg/kg i.p.), then the mate treatment protocol was performed daily and offered as a drink tea. After a 30-day treatment, the animals were weighed and euthanized to evaluate metabolic parameters on liver, adipose tissue, muscle and serum.

Ácidos graxos w-3 são conhecidos por melhorar a sensibilidade à insulina e a homeostase da glicose em modelos animais de resistência à insulina (RI). Esses efeitos tem sido relacionados a diferentes mecanismos e estudos recentes sugerem um papel importante da mitocôndria. Por isso, avaliamos a influência da suplementação com óleo de peixe (fonte rica em w-3) sobre a fisiologia mitocondrial no músculo esquelético resistente à insulina. Camundongos C57B1/6 machos, 8 semanas/idade, foram distribuídos em 4 grupos: dieta normolipídica (C), dieta hiperlipídica (H), C + óleo de peixe (CP) and H + óleo de peixe (HP). O menor consumo de O2 induzido pela dieta hiperlipídica foi associado à elevada produção de EROs, à menor trancrição de PGC1a, ATM, NRF1 e TFAM, e também à redução da fosforilação de Akt. Esses efeitos foram parcialmente prevenidos pelo óleo de peixe, que elevou a respiração, bem como o conteúdo de ICATs, a ativação de Akt e AMPK, e expressão de ATM, catalase e proteínas envolvidas na biogênese e função mitocondrial (PGC1a, PPARa, CPT1). A suplementação com óleo de peixe protege contra a RI no músculo esquelético reduzindo a produção de EROs, que parece exercer papel central na regulação da função mitocondrial através de mecanismo envolvendo a proteína ATM. / Omega-3 fatty acids are suggested to improve insulin sensitivity and glucose homeostasis in animal models of insulin resistance. These beneficial effects have been linked to different mechanisms and recent studies suggest that it may also converge to mitochondria. So we evaluated the influence of fish oil (FO), a dietary source of w-3, on mitochondrial physiology in skeletal muscle of high-fat fed mice. C57B1/6 male mice, 8 weeks-old, were randomly divided in 4 groups: control diet (C), high-fat diet (H), C + FO (CP) and H + FO (HP). The lower O2 consumption induced by high-fat diet was associated with elevated ROS production, decreased transcription of PGC1a, ATM, NRF1 and TFAM, and also reduced Akt phosphorylation. These effects were partially prevented by FO, increasing muscle O2 consumption, as well as ICAT content, activation of Akt, AMPK, and up-regulating mRNA expression of ATM, catalase and mitochondrial proteins (PGC1a, PPARa, CPT1). Dietary FO protected mice from diet-induced insulin resistance in skeletal muscle by reducing ROS production, which may exert a key role in the regulation of mitochondrial function through a mechanism involving the protein ATM.