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No description available.

Once an animal is harvested for meat, skeletal muscle attempts to maintain ATP at or near antemortem levels. To maintain ATP levels postmortem, stored glycogen is catabolized to produce ATP through glycolysis and possibly oxidative metabolism. Hydrolysis of the produced ATP acidifies muscle until an ultimate pH is reached. The ultimate pH of meat directly impacts the quality characteristics of color, texture, and water holding capacity. Therefore, our research intends to describe the contributions glycolysis and oxidative metabolism play in determining ultimate pH and fresh meat quality. Traditionally, glycogen content at death was thought to be responsible for dictating ultimate pH. This was especially true in oxidative muscle with limited glycogen stores. Yet, our research indicated that in the presence of excess glycogen, oxidative muscle maintains a high ultimate pH. Rather, pH inactivation of phosphofructokinase is responsible for terminating postmortem glycolysis and brackets ultimate pH between 5.9 – 5.5. Meat with a pH below this range is uncommon. However, AMPK γ3R200Q mutant pigs produce meat with an ultimate pH near 5.3. Due to lower AMP deaminase abundance in their muscle, AMP levels are elevated late postmortem. Because AMP is a potent activator of phosphofructokinase, the aberrant meat quality from AMPK γ3R200Q mutant pigs is caused by extended postmortem glycolysis. Combined, these data further our understanding of the factors that contribute to the formation of fresh meat quality. We also characterized AMPK γ3R200Q muscle by investigating antemortem skeletal muscle lactate transport. Lactate is transported in or out of tissues by proton-linked iii monocarboxylate transporters (MCTs). Previous reports indicated that acute activation of AMPK increased monocarboxylate transporter expression in skeletal muscle of other species. Yet, it was unknown the impact chronic activation of AMPK will have on MCT1, MCT2, and MCT4 expression in pigs. Compared to wild-type pigs, the longissimus lumborum of AMPK γ3R200Q pigs increased both MCT2 and MCT4 protein expression. Our data suggest glycolytic skeletal muscle from the AMPK γ3R200Q pigs has increased capacity for antemortem lactate export from muscle and possibly increased pyruvate transport into the mitochondria. / Ph. D.

Os óxidos de colesterol modulam o desenvolvimento da aterosclerose por mediarem a síntese, captação e exportação de colesterol, além de inflamação e citotoxicidade na parede arterial. O exercício físico regular previne e regride a lesão aterosclerótica, por melhorar o perfil lipídico, transporte reverso de colesterol e defesas antioxidantes. A proteína cinase ativada por AMP (AMPK) é um importante mediador dos efeitos metabólicos do exercício físico. Em macrófagos, sua ativação vincula-se ao aumento no efluxo de colesterol e diminuição na captação de LDL. Entretanto, não está claro se o treinamento físico modula as concentrações de óxidos de colesterol, refletindo seu benefício sobre a prevenção da aterosclerose, e se esses efeitos podem ser mediados pela AMPK. O objetivo do presente estudo foi avaliar, em camundongos dislipidêmicos, o papel de 6 semanas de treinamento físico aeróbio sobre: o infiltrado de colesterol arterial e a distribuição de óxidos de colesterol no arco aórtico e no plasma; a expressão gênica de proteínas envolvidas na metabolização de óxidos de colesterol na parede arterial; e o efeito da ativação da AMPK em macrófagos, in vitro, sobre a concentração dos óxidos de colesterol e expressão de genes envolvidos na metabolização de óxidos de colesterol. Para tanto, camundongos machos knockout para apolipoproteína E, com 16 semanas de idade, alimentados com dieta padrão, foram incluídos no estudo. O treinamento físico foi realizado em esteira, 15 m/min, por 60 min, 5 dias/semana, durante 6 semanas. Lípides plasmáticos e glicose foram determinados por ensaio enzimático e glicosímetro, respectivamente, antes e após o treinamento físico. Colesterol arterial e óxidos de colesterol foram avaliados por cromatografia gasosa acoplada à espectrometria de massa. A expressão de genes envolvidos no metabolismo de lípides foi avaliada RT-qPCR. Os resultados foram comparados por ANOVA de um fator com pós-teste de Newman-Keuls ou teste t de Student. Peso corporal, colesterol total, TG, HDL-c, glicose e óxidos de colesterol no plasma foram semelhantes entre os grupos. O treinamento físico aumentou a concentração de 7alfa-OH C (70%) e reduziu a de colesterol (32%) na aorta. Além disso, o exercício físico aumentou a expressão gênica da Cyp27a1 (54%), Cd36 (75%), Cat (70%), Prkaa1 (AMPKalfa1) (40%) e Prkaa2 (AMPKalfa2) (51%) e reduziu Abcg1 (31%), Olr1 (LOX-1) (65%), Cyp7b1 (35%) e Ch25h (48%). Nenhuma alteração foi observada na expressão de Abca1, Nr1h3 (LXRalfa) e Nr1h2 (LXRbeta). Nos macrófagos, a ativação da AMPK por AICAR, reduziu o conteúdo de 7alfa-OH C após estimulo com HDL2. O tratamento com AICAR aumentou a expressão gênica de Abca1 (52%) e Cd36 (220%) e diminuiu Prkaa1 (19%) e Cyp27a1 (47%), e não alterou Abcg1, Nr1h3 e Nr1h2. Em conclusão, em camundongos dislipidêmicos, o treinamento físico aeróbio, por 6 semanas, aumentou a concentração de 7 beta -OH C, o que se vincula à maior expressão de Cd36 no arco aórtico. A rápida difusão de óxidos de colesterol, como via complementar ao transporte reverso de colesterol, pode também ser favorecida pelo aumento e redução, respectivamente, na expressão de Cyp27a1 e Cyp7b1, favorecendo maior liberação de 27-OH C das células. Juntamente com suas ações diretas que beneficiam o transporte reverso de colesterol, previamente descritas o treinamento físico diminui a concentração de colesterol na parede arterial, prevenindo a aterosclerose. Baseado nos ensaios in vitro a ativação da AMPK não parece contribuir para o aumento das concentrações de óxidos de colesterol após treinamento físico / Oxysterols modulate the development of atherosclerosis by mediating cholesterol synthesis, uptake and exportation as well as inflammation and cytotoxicity in the arterial wall. Regular physical exercise prevents and regresses atherosclerosis by improving lipid metabolism, reverse cholesterol transport and antioxidant defenses. AMP-activated protein kinase (AMPK) plays an important role in the beneficial metabolic adaptations of physical exercise. In macrophages, its activation is related to the enhancement in cholesterol efflux and reduction in LDL uptake. However, it is not clear whether exercise training benefits in atherosclerosis is mediated by its action in oxysterols concentrations, and whether this can be modulated by AMPK. The aim of this study was to evaluate the role of a 6-week aerobic exercise training program in dyslipidemic mice in the arterial and plasma accumulation of cholesterol and oxysterols subspecies; expression of genes related to oxysterols metabolisms in the aortic arch, and the effect of AMPK activation in macrophage on the concentration of oxysterols and expression of genes linked to oxysterols metabolism. Sixteen-week-old male apoE knockout mice fed a chow diet were included in the protocol. Animals were trained in a treadmill running, 15 m/min, 60 min, 5 days/week, during 6 weeks. Plasma lipids and glucose were determined by enzymatic techniques and glycosometer, respectively. Cholesterol in aortic arch and oxysterols were measured by gas chromatography/mass spectrometer. The expression of genes involved in lipid metabolism was determined by RT-qPCR. Results (mean ± SD) were compared by one-way ANOVA with Newman-Keuls posttest or Student\'s t-test. Body weight and plasma total cholesterol, TG, HDL-c, glucose, and oxysterols were similar among groups. The exercise training enhanced 7beta-hydroxycholesterol (70%) and reduced cholesterol (32%) in the aortic arch. In addition, exercise increased Cyp27a1 (54%), Cd36 (75%), cat (70%), Prkaa1 (AMPKalpha1) (40%) and Prkaa2 (AMPKalpha2) (51%) mRNA. No changes were observed in the expression of Abca1, Nr1h3 (LXRalpha) and Nr1h2 (LXRbeta). In macrophages, the activation of AMPK by AICAR, reduced 7beta-hydroxycholesterol level after stimulation by HDL2. Treatment with AICAR increased Abca1 (52%) and Cd36 (220%), decreased Prkaa1 (19%) e Cyp27a1 (47%), and did not change Abcg1, Nr1h3 e Nr1h2. In conclusion, in dyslipidemic mice aerobic exercise training increases the nonenzymatic-driven oxysterol, 7beta-hydroxycholesterol, which is related to the enhanced expression of Cd36. The rapid diffusion of oxysterols, as a complementary pathway for the reverse cholesterol transport, may also be favored by the increase and reduction of Cyp27a1 and Cyp7b1 expressions, respectively, which in turns favors 27-OH C desorption from cells. Together with its direct role in improving reverse cholesterol transport as previously reported, aerobic exercise training diminishes cholesterol accumulation in the arterial wall preventing atherosclerosis. Based on in vitro assays, the AMPK activation does not seem to contribute to the effect of exercise in increasing oxysterols

O câncer é considerado uma das principais causas de morte no mundo. Para o tratamento dessa doença, frequentemente são utilizadas estratégias farmacológicas baseadas na intervenção quimioterápica, no qual a doxorubicina (DOX) é largamente utilizada. Visto que, o músculo esquelético possui importante papel na captação de glicose, o objetivo do presente trabalho foi investigar o efeito da DOX na intolerância à glicose. Para isso foram utilizados ratos Wistar, os quais receberam uma dose única de DOX ou salina intraperitoneal (15mg/kg). Avaliamos a expressão de proteínas envolvidas na sensibilidade à insulina e captação de glicose. Os ensaios captação de glicose foram realizados em cultura de miócitos, no qual foi utilizado o agonista de AMPK. O tratamento com DOX causou resistência à insulina e hiperglicemia. No músculo EDL e em miócitos houve menor expressão de GLUT-4 e de AMPk. Em conclusão, o tratamento com DOX causou intolerância à glicose e redução da expressão de AMPk e GLUT-4. A utilização do agonista de AMPk foi capaz de recuperar à intolerância à glicose. / The cancer is considered a major cause of death worldwide. For the treatment of this disease, with frequency are used pharmacological strategies based in chemotherapeutic intervention, in which doxorubicin (DOX) is widely used. Since the skeletal muscle plays an important role in glucose uptake, the aim of this study was to investigate the effect of DOX in glucose intolerance. For this Wistar rats which received a single dose of DOX or saline intraperitoneally (15mg / kg). We evaluated the expression of proteins involved in insulin sensitivity and glucose uptake. The glucose uptake assays were performed on culture myocytes, which was used in the agonist of AMPK. The treatment with DOX caused insulin resistance and hyperglycemia. In the EDL muscle myocytes and there was less expression of GLUT4 and AMPK. In conclusion, treatment with DOX caused impaired glucose tolerance and reduction of expression of AMPK and GLUT-4. The use of AMPK agonist was able to recover glucose intolerance.

Au-delà de sa présence sur les microtubules stables, l'acétylation de l’-tubuline peut être augmentée après exposition des cellules aux UV ou après une carence en nutriments, phénomène que l’on appelle « hyperacétylation ». Cependant, le mécanisme d’induction de cette hyperacétylation est encore inconnu. Dans cette étude, nous montrons que l’hyperacétylation de la tubuline est une réponse générale aux stress cellulaire, et nous avons cherché à caractériser cette réponse, à identifier la voie de signalisation activée par le stress et conduisant à cette réponse, et à étudier la signification biologique de ce phénomène rapide et réversible. Nous avons trouvé que MEC-17/-TAT1, l’acétyltransférease majeure de l’ tubuline, est une enzyme nécessaire à l’induction de l’hyperacétylation en réponse aux stress, et qu'elle est régulée, à l’état basal par une autre acétyltransférase appelée p300. Au cours du stress, nous montrons que l'augmentation de la production des espèces réactives de l'oxygène (ROS), conduit à l'activation de la kinase « AMP-activated protein kinase (AMPK) », qui, à son tour provoque la phosphorylation de MEC-17, et probablement son activation. Enfin, nous montrons que l’hyperacétylation de la tubuline induite par le stress, participe à la survie des cellules dans des conditions de stress et à l'induction de l'autophagie de survie. / Beyond its presence in stable microtubules, -tubulin acetylation can be boosted after UV exposure or after nutrient deprivation but the mechanisms of this hyperacetylation are still unknown. In this study, we show that tubulin hyperacetylation is a general cell stress response, and aimed to characterize this response, to identify the stress-activated signaling pathway leading to its induction and the biological significance of this rapid and reversible phenomenon. We found that the major tubulin acetyltransferase MEC-17/-TAT1 is the main enzyme required for mediating tubulin hyperacetylation upon stress, and that it is regulated under normal conditions by the acetyltransferase p300. Upon stress, we show that the increased production of reactive oxygen species (ROS), leads to the activation of AMP-activated protein kinase (AMPK), which in turn mediates MEC-17 phosphorylation, and probably its subsequent activation. Finally, we show that tubulin hyperacetylation induced upon stress participate in cell survival under stress conditions and in the induction of protective autophagy.

Os óxidos de colesterol modulam o desenvolvimento da aterosclerose por mediarem a síntese, captação e exportação de colesterol, além de inflamação e citotoxicidade na parede arterial. O exercício físico regular previne e regride a lesão aterosclerótica, por melhorar o perfil lipídico, transporte reverso de colesterol e defesas antioxidantes. A proteína cinase ativada por AMP (AMPK) é um importante mediador dos efeitos metabólicos do exercício físico. Em macrófagos, sua ativação vincula-se ao aumento no efluxo de colesterol e diminuição na captação de LDL. Entretanto, não está claro se o treinamento físico modula as concentrações de óxidos de colesterol, refletindo seu benefício sobre a prevenção da aterosclerose, e se esses efeitos podem ser mediados pela AMPK. O objetivo do presente estudo foi avaliar, em camundongos dislipidêmicos, o papel de 6 semanas de treinamento físico aeróbio sobre: o infiltrado de colesterol arterial e a distribuição de óxidos de colesterol no arco aórtico e no plasma; a expressão gênica de proteínas envolvidas na metabolização de óxidos de colesterol na parede arterial; e o efeito da ativação da AMPK em macrófagos, in vitro, sobre a concentração dos óxidos de colesterol e expressão de genes envolvidos na metabolização de óxidos de colesterol. Para tanto, camundongos machos knockout para apolipoproteína E, com 16 semanas de idade, alimentados com dieta padrão, foram incluídos no estudo. O treinamento físico foi realizado em esteira, 15 m/min, por 60 min, 5 dias/semana, durante 6 semanas. Lípides plasmáticos e glicose foram determinados por ensaio enzimático e glicosímetro, respectivamente, antes e após o treinamento físico. Colesterol arterial e óxidos de colesterol foram avaliados por cromatografia gasosa acoplada à espectrometria de massa. A expressão de genes envolvidos no metabolismo de lípides foi avaliada RT-qPCR. Os resultados foram comparados por ANOVA de um fator com pós-teste de Newman-Keuls ou teste t de Student. Peso corporal, colesterol total, TG, HDL-c, glicose e óxidos de colesterol no plasma foram semelhantes entre os grupos. O treinamento físico aumentou a concentração de 7alfa-OH C (70%) e reduziu a de colesterol (32%) na aorta. Além disso, o exercício físico aumentou a expressão gênica da Cyp27a1 (54%), Cd36 (75%), Cat (70%), Prkaa1 (AMPKalfa1) (40%) e Prkaa2 (AMPKalfa2) (51%) e reduziu Abcg1 (31%), Olr1 (LOX-1) (65%), Cyp7b1 (35%) e Ch25h (48%). Nenhuma alteração foi observada na expressão de Abca1, Nr1h3 (LXRalfa) e Nr1h2 (LXRbeta). Nos macrófagos, a ativação da AMPK por AICAR, reduziu o conteúdo de 7alfa-OH C após estimulo com HDL2. O tratamento com AICAR aumentou a expressão gênica de Abca1 (52%) e Cd36 (220%) e diminuiu Prkaa1 (19%) e Cyp27a1 (47%), e não alterou Abcg1, Nr1h3 e Nr1h2. Em conclusão, em camundongos dislipidêmicos, o treinamento físico aeróbio, por 6 semanas, aumentou a concentração de 7 beta -OH C, o que se vincula à maior expressão de Cd36 no arco aórtico. A rápida difusão de óxidos de colesterol, como via complementar ao transporte reverso de colesterol, pode também ser favorecida pelo aumento e redução, respectivamente, na expressão de Cyp27a1 e Cyp7b1, favorecendo maior liberação de 27-OH C das células. Juntamente com suas ações diretas que beneficiam o transporte reverso de colesterol, previamente descritas o treinamento físico diminui a concentração de colesterol na parede arterial, prevenindo a aterosclerose. Baseado nos ensaios in vitro a ativação da AMPK não parece contribuir para o aumento das concentrações de óxidos de colesterol após treinamento físico / Oxysterols modulate the development of atherosclerosis by mediating cholesterol synthesis, uptake and exportation as well as inflammation and cytotoxicity in the arterial wall. Regular physical exercise prevents and regresses atherosclerosis by improving lipid metabolism, reverse cholesterol transport and antioxidant defenses. AMP-activated protein kinase (AMPK) plays an important role in the beneficial metabolic adaptations of physical exercise. In macrophages, its activation is related to the enhancement in cholesterol efflux and reduction in LDL uptake. However, it is not clear whether exercise training benefits in atherosclerosis is mediated by its action in oxysterols concentrations, and whether this can be modulated by AMPK. The aim of this study was to evaluate the role of a 6-week aerobic exercise training program in dyslipidemic mice in the arterial and plasma accumulation of cholesterol and oxysterols subspecies; expression of genes related to oxysterols metabolisms in the aortic arch, and the effect of AMPK activation in macrophage on the concentration of oxysterols and expression of genes linked to oxysterols metabolism. Sixteen-week-old male apoE knockout mice fed a chow diet were included in the protocol. Animals were trained in a treadmill running, 15 m/min, 60 min, 5 days/week, during 6 weeks. Plasma lipids and glucose were determined by enzymatic techniques and glycosometer, respectively. Cholesterol in aortic arch and oxysterols were measured by gas chromatography/mass spectrometer. The expression of genes involved in lipid metabolism was determined by RT-qPCR. Results (mean ± SD) were compared by one-way ANOVA with Newman-Keuls posttest or Student\'s t-test. Body weight and plasma total cholesterol, TG, HDL-c, glucose, and oxysterols were similar among groups. The exercise training enhanced 7beta-hydroxycholesterol (70%) and reduced cholesterol (32%) in the aortic arch. In addition, exercise increased Cyp27a1 (54%), Cd36 (75%), cat (70%), Prkaa1 (AMPKalpha1) (40%) and Prkaa2 (AMPKalpha2) (51%) mRNA. No changes were observed in the expression of Abca1, Nr1h3 (LXRalpha) and Nr1h2 (LXRbeta). In macrophages, the activation of AMPK by AICAR, reduced 7beta-hydroxycholesterol level after stimulation by HDL2. Treatment with AICAR increased Abca1 (52%) and Cd36 (220%), decreased Prkaa1 (19%) e Cyp27a1 (47%), and did not change Abcg1, Nr1h3 e Nr1h2. In conclusion, in dyslipidemic mice aerobic exercise training increases the nonenzymatic-driven oxysterol, 7beta-hydroxycholesterol, which is related to the enhanced expression of Cd36. The rapid diffusion of oxysterols, as a complementary pathway for the reverse cholesterol transport, may also be favored by the increase and reduction of Cyp27a1 and Cyp7b1 expressions, respectively, which in turns favors 27-OH C desorption from cells. Together with its direct role in improving reverse cholesterol transport as previously reported, aerobic exercise training diminishes cholesterol accumulation in the arterial wall preventing atherosclerosis. Based on in vitro assays, the AMPK activation does not seem to contribute to the effect of exercise in increasing oxysterols

O câncer é considerado uma das principais causas de morte no mundo. Para o tratamento dessa doença, frequentemente são utilizadas estratégias farmacológicas baseadas na intervenção quimioterápica, no qual a doxorubicina (DOX) é largamente utilizada. Visto que, o músculo esquelético possui importante papel na captação de glicose, o objetivo do presente trabalho foi investigar o efeito da DOX na intolerância à glicose. Para isso foram utilizados ratos Wistar, os quais receberam uma dose única de DOX ou salina intraperitoneal (15mg/kg). Avaliamos a expressão de proteínas envolvidas na sensibilidade à insulina e captação de glicose. Os ensaios captação de glicose foram realizados em cultura de miócitos, no qual foi utilizado o agonista de AMPK. O tratamento com DOX causou resistência à insulina e hiperglicemia. No músculo EDL e em miócitos houve menor expressão de GLUT-4 e de AMPk. Em conclusão, o tratamento com DOX causou intolerância à glicose e redução da expressão de AMPk e GLUT-4. A utilização do agonista de AMPk foi capaz de recuperar à intolerância à glicose. / The cancer is considered a major cause of death worldwide. For the treatment of this disease, with frequency are used pharmacological strategies based in chemotherapeutic intervention, in which doxorubicin (DOX) is widely used. Since the skeletal muscle plays an important role in glucose uptake, the aim of this study was to investigate the effect of DOX in glucose intolerance. For this Wistar rats which received a single dose of DOX or saline intraperitoneally (15mg / kg). We evaluated the expression of proteins involved in insulin sensitivity and glucose uptake. The glucose uptake assays were performed on culture myocytes, which was used in the agonist of AMPK. The treatment with DOX caused insulin resistance and hyperglycemia. In the EDL muscle myocytes and there was less expression of GLUT4 and AMPK. In conclusion, treatment with DOX caused impaired glucose tolerance and reduction of expression of AMPK and GLUT-4. The use of AMPK agonist was able to recover glucose intolerance.

Plusieurs études ont montré que certaines kinases situées dans le foie, « mammalian target of rapamycin » (mTOR), « adenosine monophosphate-activated protein kinase » (AMPK) et « general control non-depressible kinase 2 » (GCN2) répondent à la disponibilité en acides aminés.L’objectif de nos études a été de préciser le rôle de deux de ces voies, l’AMPK et GCN2, dans les adaptations du métabolisme énergétique et de la synthèse protéique en réponse aux variations en protéines du régime. Pour cela, des souris de type sauvage et des souris KO n’exprimant plus la voie AMPK ou GCN2 dans le foie ont été nourries pendant trois semaines avec un régime faible, normal ou fort en protéines. Les analyses ont montré que les souris KO-AMPK foie spécifique et nourries sous régime normoprotéique adaptent leur métabolisme hépatique notamment en sécrétant le facteur fibroblastique FGF21 ce qui leur permet de compenser l’absence d’AMPK et de présenter des profils d’oxydation normaux.Au contraire, les souris KO-AMPK foie spécifique nourries avec des régimes faibles ou forts en protéines présentent des altérations des profils d’oxydation des lipides et des glucides liées à une absence de modification du métabolisme hépatique.La délétion de GCN2 dans le foie, quant à elle, n’a d’effet que sous régime faible en protéines : les souris KO-GCN2 foie spécifique présentent une plus faible oxydation lipidique et une plus forte oxydation glucidique que les souris sauvages en période postprandiale dû à l’absence d’induction de la sécrétion de FGF21.Concernant le métabolisme des protéines, les kinases GCN2 et AMPK ne semblent pas impliquées dans l’intensité du flux de synthèse protéique dans le foie et en périphérie dans le muscle en période postprandiale.En conclusion, ces travaux montrent que les délétions de l’AMPK et de GCN2 hépatiques affectent le métabolisme énergétique mais pas le métabolisme protéique et que les conséquences dépendent de la composition du régime. / Several studies have reported that some kinases located in the liver respond to the availability of amino acids. These kinases are mammalian target of rapamycin '(mTOR), "adenosine monophosphate-activated protein kinase" (AMPK) and "general control non-depressible kinase 2" (GCN2).The aim of our study was to clarify the role of two of these signaling pathways, AMPK and GCN2 in the adaptations of energy and protein metabolism in response to the modulation of dietary protein content. Wild-type and liver AMPK-deficient or liver GCN2-deficient mice were fed either a low, a normal or high protein diet during three weeks. Analyzes showed that liver AMPK-deficient mice fed under a normo-protein diet exhibit an adapatation of liver metabolism and secret FGF21 which enables them to have normal postprandial oxidation profiles.In contrast, liver AMPK-deficient mice fed a low or a high protein diet exhibit an alteration in postprandial oxidation profiles. The deletion of GCN2 in the liver only has an effect under low protein diet as liver GCN2 deficient mice have a lower lipid oxidation and a higher carbohydrate oxidation linked to the absence of FGF21 secretion. Concerning protein metabolism, AMPK and GCN2 do not seem to be involved in protein synthesis rate in the posrprandial period in the liver and periphery in the postprandial muscle. In conclusion, these studies show that hepatic AMPK and GCN2 deletions affect energy metabolism, but not protein metabolism and that the consequences depend on diet composition.

La progression de l’espérance de vie observée au cours du XXième siècle a été accompagnée par une augmentation massive de l’incidence des maladies liées à l’âge et en particulier des maladies neurodégénératives. Malheureusement, les thérapeutiques actuelles ciblant principalement les anomalies d’agrégation protéique caractérisant ces maladies, tel que la maladie d’Alzheimer, ont échoué au niveau des essais cliniques. De récentes études épidémiologiques ont suggéré un lien entre la dysfonction métabolique et les maladies neurodégénératives. Par conséquent, une approche alternative pour développer des nouveaux médicaments serait se cibler les voies de signalisation métaboliques perturbées dans les modèles de maladie d’Alzheimer. L’AMPK (AMP activated protein kinase) est une enzyme activée par les bas niveaux d’énergie cellulaire via la détection du taux AMP : ATP. Une fois activée, l’AMPK allonge la durée de vie d’organismes modèles et protège contre le développement de pathologies liées à l’âge telle que les maladies neurodégénératives. De plus, l’AMPK régule l’homéostasie mitochondriale et les réseaux mitochondriaux chez les mammifères. Cependant, il reste à savoir si l’AMPK protège contre le développement de pathologies neurodégénératives via la régulation de la structure mitochondriale. Lors de ces travaux, nous avons utilisé un protocole d’apprentissage et de mémoire chez C. elegans pour mesurer la fonction neuronale. Nous avons montré que les nématodes exprimant le peptide amyloïde Aβ1-42 dans les neurones avait une capacité d’apprentissage détériorée. Ce déficit a pu être restauré par l’activation constitutionnelle de l’AMPK. Nous montrons également que l’activation de l’AMPK améliore les capacités d’apprentissage des nématodes sauvages en induisant la fusion des mitochondries. En effet, les vers mutés pour le gène responsable de la fusion mitochondriale ont une capacité d’apprentissage diminuée, laquelle peut être restaurée par le rétablissement de la fusion mitochondriale, spécifiquement dans les neurones. Des résultats supplémentaires suggèrent que l’AMPK induirait ses effets bénéfiques sur la fonction neuronale en inhibant le facteur de transcription CRTC-1 (CREB-regulated transcriptional co-activator 1). Nos résultats tendent à montrer que cibler le métabolisme cellulaire neuronal représenterait une option thérapeutique viable afin de maintenir les fonctions neuronales dans le cadre de pathologies neurodégénératives. / The dramatic increase in life expectancy during the 20th century was accompanied by a resultant epidemic of age-related pathologies including neurodegenerative diseases. Unfortunately, current therapeutics primarily focusing on protein misfolding aspects of diseases such as Alzheimer’s Disease (AD) have been unsuccessful in the clinical trials. Recent epidemiological studies have suggested a strong association between metabolic dysfunction and neurodegeneration. Therefore, an alternative approach is to target metabolic pathways disrupted in AD models for therapeutics. AMP activated protein kinase (AMPK) is activated in a low energy state via sensing the AMP: ATP ratio. Once active, AMPK promotes longevity in model organism and protects against a wide range of age related diseases including neurodegenerative diseases. In addition, AMPK regulates mitochondrial homeostasis and mitochondrial networks in mammals. However, whether mitochondrial regulation causally links AMPK to protection against neurodegenerative disease is unknown. Here we use a learning and memory protocol in C. elegans as readout of neuronal function. We show that nematodes expressing the toxic amyloid peptide Aβ1-42 in the neurons display impaired learning ability, which can be rescued by constitutive activation of AMPK (CA-AMPK). We further show that CA-AMPK enhances learning ability in wild type nematodes by promoting mitochondrial fusion. Indeed, fusion deficient worms show impaired learning, which can be rescued by restoring mitochondrial fusion specifically in the neurons. Additional results suggest that AMPK might promote its beneficial effects on neuronal function via inhibition of CREBregulated transcriptional co-activator 1 (CRTC-1). Our results show that targeting neuronal metabolism may be a viable therapeutic option to restore neuronal function in the context of neurodegenerative diseases.