Les mutations germinales activatrices de la voie RAS sont responsables de maladies rares regroupées sous le nom de RASopathies : le Syndrome de Noonan, le Syndrome de Noonan avec de Multiples Lentigines, la Neurofibromatose de type 1, le Syndrome de Malformations Capillaires et Malformations Artério-Veinseuses, le Syndrome Cardio-Facio-Cutané, le Syndrome de Legius et le Syndrome de Costello. Cette thèse s’intéresse au syndrome de Costello causé par une mutation hétérozygote de novo du gène HRAS. Ce syndrome est révélé dans les premiers mois de la vie et se caractérise par un retard de croissance postnatal, des traits du visage épais, un déficit intellectuel, des anomalies cutanées, ainsi qu’une prédisposition à développer des tumeurs. De plus, les patients atteints du syndrome de Costello développent une cardiomyopathie hypertrophique, de l’hypertension, une hypotonie et une myopathie d'origine moléculaire inconnue. En lien avec une association de malade et le service de génétique du CHU de Bordeaux, nous avons mené une exploration des anomalies protéomiques dans les tissus d’une souris modèle du syndrome de Costello ainsi que dans des fibroblastes de patients et des cellules modèles exprimant les formes mutées de HRASG12S et HRASG12A. Cette analyse globale et sans a priori a révélé des altérations au niveau du métabolisme énergétique et plus particulièrement de la composition des mitochondries. Le déficit fonctionnel des mitochondries, centrale énergétique du corps humain, a été caractérisé par des approches de biochimie, de bioénergétique et de biologie cellulaire. De plus, l’analyse des données ‘omiques’ a permis de suggérer une nouvelle hypothèse dans la physiopathologie du syndrome de Costello. Cette hypothèse considère l’implication d’un micro-ARN, le miR-221* dans l’inhibition du métabolisme oxydatif. Les analyses génétiques réalisées sur les cellules de patients et les cellules modèles ont démontré l’inhibition de l’expression de la protéine AMPK, un régulateur majeur du métabolisme mitochondrial, par le miR-221* sous le contrôle de HRASG12S et HRASG12A. Ces découvertes ont permis d’élaborer une stratégie thérapeutique visant à réduire la cardiomyopathie dans le syndrome de Costello. Les analyses précliniques effectuées sur les modèles cellulaires et le modèle murin ont permis d’évaluer l’efficacité d’une stimulation pharmacologique du métabolisme mitochondrial. Cette thèse révèle donc l’implication des mitochondries dans le syndrome de Costello et l’analyse moléculaire réalisée propose une série de données ‘Omiques’ qui permettront de progresser dans la compréhension de cette maladie rare. / Germline activating mutations of the RAS pathway are responsible for rare diseases grouped under the name of RASopathies: Noonan Syndrome, Noonan Syndrome with multiple Lentigines, Type 1-neurofibromatosis, Capillaries malformations and arteriovenous malformations syndrome, Cardio-Facio-Cutaneous Syndrome, Legius Syndrome and Costello Syndrome. This Ph.D thesis focuses on Costello syndrome that is caused by a heterozygous de novo mutation of the HRAS gene. This syndrome is revealed in the first months of life and is characterized by postnatal growth retardation, thick facial features, intellectual deficit, skin abnormalities, and a predisposition to developing tumors. In addition, patients with Costello syndrome develop hypertrophic cardiomyopathy, hypertension, hypotonia and myopathy of unknown molecular origin. In connection with a patients association and the genetics department of Bordeaux University Hospital, we conducted an exploration of proteomic abnormalities in the tissues of a mouse model of the Costello syndrome as well as in patients’ fibroblasts and cell models expressing mutated forms of HRASG12S and HRASG12A. This global and unbiased analysis revealed alterations in energy metabolism and more particularly in the composition of mitochondria. The functional deficiency of mitochondria, energy plants of the human body, has been characterized by biochemistry, bioenergetics and cell biology approaches. In addition, the 'omic' analysis of Costello syndrome suggested a new pathophysiology hypothesis that considered the involvement of a microRNA, miR-221* in the alteration of oxidative metabolism. Functional genetic analyzes performed on patient cells and cell models demonstrated the inhibition of the expression of the major mitochondrial metabolism regulator AMPK protein by miR-221* under the control of HRASG12S and HRASG12A. These findings led to the development of a preclinical therapeutic strategy to reduce cardiomyopathy in Costello syndrome. Preclinical investigations performed on the cellular models and the murine model made it possible to evaluate the efficacy of a pharmacological stimulation of mitochondrial metabolism. This thesis thus reveals the involvement of mitochondria in Costello syndrome and the molecular analysis carried out makes available a series of 'Omics' data that will allow progress in the understanding of this rare disease.

O acúmulo de lipídeos associado à obesidade, resistência à insulina (RI) e diabetes mellitus tipo 2 (DM2) pode levar ao desenvolvimento de danos renais, e diversos mecanismos podem estar envolvidos neste processo, dentre os quais: 1) redução na atividade da proteína ativada por AMP (AMPK); 2) hiperativação do sistema renina angiotensina (SRA) e consequente aumento na produção de angiotensina II (Ang II). O treinamento físico aeróbio (TFA) promove melhora metabólica significativa, no entanto, pouco se sabe sobre os mecanismos celulares induzidos pelo TFA contra o desenvolvimento de danos renais associados com doenças metabólicas. Sendo assim, o objetivo deste estudo foi avaliar o potencial do TFA para a prevenção de danos renais induzidos por dieta de cafeteria, e a participação do SRA e da proteína AMPK nessa resposta. Para isso, camundongos machos adultos C57BL6/J foram separados em grupos (n=13/grupo) sedentários (SED) alimentados com dieta normocalórica (NO) ou de cafeteria (CAF) (SED-NO e SED-CAF, respectivamente) e treinados (TF) alimentados com dieta NO ou CAF (TF-NO e TF-CAF, respectivamente). O TFA foi realizado a 60% da capacidade máxima, simultaneamente com as dietas durante 8 semanas. A dieta de cafeteria causou maior adiposidade, intolerância à glicose e RI no grupo SED-CAF, enquanto o TFA preveniu esses prejuízos no grupo TF-CAF. Os animais SED-CAF apresentaram 88% de aumento no ritmo de filtração glomerular (RFG), maior deposição lipídica renal e redução do espaço de Bowman comparado ao SED-NO, as quais foram prevenidas no grupo TF-CAF. Não houve alteração no conteúdo de colágeno IV e fibronectina, entretanto o TNF-alfa aumentou em ambos os grupos alimentados com dieta de cafeteria. Houve aumento de 27% da expressão proteica da p-AMPK no grupo TF-CAF, sem diferenças na expressão de t-ACC, p-ACC, PGC1-alfa e SIRT-1. A expressão gênica do SREBP-1 não diferiu entre os grupos, porém a expressão do SREBP-2 aumentou nos grupos SED-CAF e TF-CAF comparado aos grupos SED-NO e TF-NO. No soro, apenas a atividade da ECA2 aumentou nos grupos TF-NO e TF-CAF comparados aos sedentários. No rim, a atividade da ECA aumentou 46% no grupo SED-CAF comparado ao SED-NO, e o TFA foi capaz de prevenir esse aumento. No entanto, a Ang II renal aumentou nos grupos SED-CAF, TF-NO e TF-CAF comparados ao grupo SED-NO. Não houve diferença nos componentes do SRA ECA2/Ang 1-7/Mas renal. Em conclusão, o TFA preveniu os danos renais causados pela dieta de cafeteria, tais como acúmulo de lipídeos nos rins, aumento do RFG e redução do espaço de Bowman, e essa resposta está associada, pelo menos em parte, com a maior ativação da AMPK independente da contribuição do SRA / Lipid accumulation observed in the obesity, insulin resistance (IR) and Diabetes Mellitus type 2 (DM2) may lead to the development of renal damage, and several mechanisms may be involved in this process, such as: 1) reduction in the AMP-activated protein (AMPK) activity; 2) hyperactivation of the renin angiotensin system (RAS) and consequent increase in the production of Angiotensin II (Ang II). Aerobic exercise training (AET) promotes significant metabolic improvement, however, little is known about the cellular mechanisms induced by AET against the development of kidney damage associated with metabolic diseases. Thus, the present study aimed to evaluate the potential of AET to prevent kidney damage induced by cafeteria diet, and the participation of RAS and AMPK protein in this response. Adult male C57BL6/J mice were separated into sedentary (SED) groups fed a normocaloric (NO) or cafeteria (CAF) (SED-NO and SED-CAF, respectively) and trained (TF) fed a NO or CAF diet (TF-NO and TF-CAF, respectively). The AET was performed at 60% of the maximum capacity simultaneously with the diets during 8 weeks. The cafeteria diet induced adiposity increase, glucose intolerance and IR, while AET prevented these changes. Animals SED-CAF increased 88% of glomerular filtration rate (GFR), increased renal lipid deposition and reduced Bowman\'s space compared to SED-NO, which were prevented by AET in the TF-CAF group. There was no change in the collagen IV and fibronectin, however TNF-alpha increased in both cafeteria diet fed groups. There was a 27% increase in the protein p-AMPK expression in the TF-CAF group, with no changes in t-ACC, p-ACC, PGC1-alpha and SIRT-1 expression. The SREBP-1 gene expression did not change among groups, but SREBP-2 gene expression increased in the SED-CAF and TF-CAF groups compared to the SED-NO and TF-NO groups. In the serum, only the activity of ACE 2 increased in TF-NO and TF-CAF groups compared to sedentary groups. In the kidney, ACE activity increased 46% in the SED-CAF group compared to SED-NO, nevertheless the AET was able to prevent this increase. Renal Ang II concentration increased in SED-CAF, TF-NO and TF-CAF groups compared to the SED-NO. No differences were observed in the components of renal RAS ACE2/Ang 1-7/Mas. In conclusion, AET prevented the renal damage caused by cafeteria diet, such as lipid accumulation, increased GFR and reduced Bowman space, and these responses are associated, at least in part, with greater activation of the AMPK protein independent of the RAS contribution

Objetivamos investigar o papel da quinase ativada por adenosina monofosfato (AMPK) na doença renal crônica. Induzimos nefrite túbulo-intersticial (NTI) em camundongos C57BL/6 e LyzM-cre AMPKflox/flox através de ração com adenina, e tratamos com metformina (Met) 200 mg/kg/dia. Avaliamos ainda o efeito da Met sobre a transição epitélio-mesenquimal (TEM) em células tubulares epiteliais renais murinas (linhagem MM55.K). Os C57BL/6 tratados apresentaram preservação da função renal; maior frequência de macrófagos (MØ) M1, em detrimento dos M2; e redução de marcadores de fibrose. Os LyzM-cre AMPK-/- não diferiram dos LyzM-cre AMPK+/+ quanto à intensidade da lesão, por a molécula já se encontrar infrarregulada na NTI. Contudo, ao serem tratados com Met, os LyzM-cre AMPK+/+ evoluíram melhor do que os não tratados, o mesmo não se verificando nos LyzM-cre AMPK-/-, sugerindo que a ação da Met nos MØ é dependente de AMPK. As MM55.K, após estímulo com Met, exibiram maior captação de glicose, expressão do transportador Glut-2, ativação da glicólise, e resistência à TEM. / We aimed to investigate the role of adenosine monophosphate activated kinase (AMPK) on chronic kidney disease. We induced tubulointerstitial nephritis (TIN) in C57BL/6 and LyzM-cre AMPKflox/flox mice by feeding them adenine diet, and then treating with metformin (Met) 200 mg/kg/day. We also evaluated the effect of Met on epithelium-to-mesenchyma transition (EMT) of murine epithelial renal tubular cells (lineage MM55.K). Met-treated C57BL/6 mice presented preserved kidney function, greater frequency of M1 macrophages (MØ) compared to M2 ones, and reduced markers of fibrosis. Disease severity on LyzM-cre AMPK-/- and AMPK+/+ mice did not differ, since the molecule was already downregulated on TIN. However, by treating them with Met, LyzM-cre AMPK+/+ improved in comparison to the non-treated mice. The same did not happen with LyzM-cre AMPK-/- mice, suggesting that Met effect on MØ is AMPK-dependent. MM55.K cells, after stimulus with Met, showed increased glucose uptake, greater expression of the transporter Glut-2, activation of glycolysis, and resistance to EMT.

LKB1 est un gène suppresseur de tumeur qui code une kinase « maitre » dont l’activité contrôle la polarité et la prolifération cellulaire en les coordonnant avec l’état métabolique de la cellule. Ce travail a abouti à l’identification d’une nouvelle isoforme LKB1 appelée ∆N-LKB1 qui est générée par transcription alternative et initiation interne de la traduction de l'ARNm LKB1. La protéine ∆N-LKB1 est délétée de sa partie N-terminale incluant une partie de son domaine kinase. Bien que la protéine N-LKB1 soit catalytiquement inactive, elle potentialise l'effet activateur de la protéine LKB1 sur sa cible principale l’APMK, senseur énergétique de la cellule, via une interaction directe avec le domaine d'auto-inhibition de l’AMPK. En revanche, ∆N-LKB1 interfère négativement avec la capacité de LKB1 à induire la polarité cellulaire. Enfin, en utilisant des approches in vitro et in vivo, nous avons montré que N-LKB1 possède une propriété oncogénique intrinsèque. N-LKB1 est exprimée seule dans la lignée NCI-H460 issue du cancer du poumon. L’inhibition de l’expression de N-LKB1 dans les cellules NCI-H460 induit une diminution de la survie de ces cellules et inhibe leur pouvoir oncogénique quand elles sont greffées dans la souris nude. Nous avons donc identifié une nouvelle isoforme LKB1 qui stimule l’adaptation métabolique LKB1-dépendante, mais qui inhibe la polarité cellulaire contrôlée par LKB1. Le suppresseur de tumeur LKB1 ainsi que l’oncogène N-LKB1 sont codé par le même gène, ce qui peut expliquer certains des effets paradoxaux de LKB1 durant la tumorigenèse. / The LKB1 tumor suppressor gene encodes a master kinase that coordinates the regulation of energetic metabolism, cell growth and cell polarity. We now report the identification of a novel isoform of LKB1 named N-LKB1 that is generated through alternative transcription and internal initiation of translation of the LKB1 mRNA. The N-LKB1 protein lacks the N-terminal region and a portion of the kinase domain. Although N-LKB1 is catalytically inactive, it potentiates the stimulating effect of LKB1 on the AMP-activated protein kinase (AMPK) metabolic sensor through a direct interaction with the regulatory auto-inhibitory domain of AMPK. Contrasting, N-LKB1 negatively interferes with the LKB1 polarizing activity. Finally, combining in vitro and in vivo approaches, we showedthat N-LKB1 has an intrinsic oncogenic property. N-LKB1 is expressed solely in the lung cancer cell line, NCI-H460. Silencing of N-LKB1 decreased survival of NCI-H460 cells and inhibited their tumorigenicity when engrafted in nude mice. In conclusion, we have identified a novel LKB1 isoform that enhances the LKB1-controlled AMPK metabolic activity but inhibits LKB1-induced polarizing activity. Both, the LKB1 tumor suppressor and the oncogene, N-LKB1, are expressed from the same locus and this may account for some of the paradoxical effects of LKB1 during tumorigenesis.

O acúmulo de lipídeos associado à obesidade, resistência à insulina (RI) e diabetes mellitus tipo 2 (DM2) pode levar ao desenvolvimento de danos renais, e diversos mecanismos podem estar envolvidos neste processo, dentre os quais: 1) redução na atividade da proteína ativada por AMP (AMPK); 2) hiperativação do sistema renina angiotensina (SRA) e consequente aumento na produção de angiotensina II (Ang II). O treinamento físico aeróbio (TFA) promove melhora metabólica significativa, no entanto, pouco se sabe sobre os mecanismos celulares induzidos pelo TFA contra o desenvolvimento de danos renais associados com doenças metabólicas. Sendo assim, o objetivo deste estudo foi avaliar o potencial do TFA para a prevenção de danos renais induzidos por dieta de cafeteria, e a participação do SRA e da proteína AMPK nessa resposta. Para isso, camundongos machos adultos C57BL6/J foram separados em grupos (n=13/grupo) sedentários (SED) alimentados com dieta normocalórica (NO) ou de cafeteria (CAF) (SED-NO e SED-CAF, respectivamente) e treinados (TF) alimentados com dieta NO ou CAF (TF-NO e TF-CAF, respectivamente). O TFA foi realizado a 60% da capacidade máxima, simultaneamente com as dietas durante 8 semanas. A dieta de cafeteria causou maior adiposidade, intolerância à glicose e RI no grupo SED-CAF, enquanto o TFA preveniu esses prejuízos no grupo TF-CAF. Os animais SED-CAF apresentaram 88% de aumento no ritmo de filtração glomerular (RFG), maior deposição lipídica renal e redução do espaço de Bowman comparado ao SED-NO, as quais foram prevenidas no grupo TF-CAF. Não houve alteração no conteúdo de colágeno IV e fibronectina, entretanto o TNF-alfa aumentou em ambos os grupos alimentados com dieta de cafeteria. Houve aumento de 27% da expressão proteica da p-AMPK no grupo TF-CAF, sem diferenças na expressão de t-ACC, p-ACC, PGC1-alfa e SIRT-1. A expressão gênica do SREBP-1 não diferiu entre os grupos, porém a expressão do SREBP-2 aumentou nos grupos SED-CAF e TF-CAF comparado aos grupos SED-NO e TF-NO. No soro, apenas a atividade da ECA2 aumentou nos grupos TF-NO e TF-CAF comparados aos sedentários. No rim, a atividade da ECA aumentou 46% no grupo SED-CAF comparado ao SED-NO, e o TFA foi capaz de prevenir esse aumento. No entanto, a Ang II renal aumentou nos grupos SED-CAF, TF-NO e TF-CAF comparados ao grupo SED-NO. Não houve diferença nos componentes do SRA ECA2/Ang 1-7/Mas renal. Em conclusão, o TFA preveniu os danos renais causados pela dieta de cafeteria, tais como acúmulo de lipídeos nos rins, aumento do RFG e redução do espaço de Bowman, e essa resposta está associada, pelo menos em parte, com a maior ativação da AMPK independente da contribuição do SRA / Lipid accumulation observed in the obesity, insulin resistance (IR) and Diabetes Mellitus type 2 (DM2) may lead to the development of renal damage, and several mechanisms may be involved in this process, such as: 1) reduction in the AMP-activated protein (AMPK) activity; 2) hyperactivation of the renin angiotensin system (RAS) and consequent increase in the production of Angiotensin II (Ang II). Aerobic exercise training (AET) promotes significant metabolic improvement, however, little is known about the cellular mechanisms induced by AET against the development of kidney damage associated with metabolic diseases. Thus, the present study aimed to evaluate the potential of AET to prevent kidney damage induced by cafeteria diet, and the participation of RAS and AMPK protein in this response. Adult male C57BL6/J mice were separated into sedentary (SED) groups fed a normocaloric (NO) or cafeteria (CAF) (SED-NO and SED-CAF, respectively) and trained (TF) fed a NO or CAF diet (TF-NO and TF-CAF, respectively). The AET was performed at 60% of the maximum capacity simultaneously with the diets during 8 weeks. The cafeteria diet induced adiposity increase, glucose intolerance and IR, while AET prevented these changes. Animals SED-CAF increased 88% of glomerular filtration rate (GFR), increased renal lipid deposition and reduced Bowman\'s space compared to SED-NO, which were prevented by AET in the TF-CAF group. There was no change in the collagen IV and fibronectin, however TNF-alpha increased in both cafeteria diet fed groups. There was a 27% increase in the protein p-AMPK expression in the TF-CAF group, with no changes in t-ACC, p-ACC, PGC1-alpha and SIRT-1 expression. The SREBP-1 gene expression did not change among groups, but SREBP-2 gene expression increased in the SED-CAF and TF-CAF groups compared to the SED-NO and TF-NO groups. In the serum, only the activity of ACE 2 increased in TF-NO and TF-CAF groups compared to sedentary groups. In the kidney, ACE activity increased 46% in the SED-CAF group compared to SED-NO, nevertheless the AET was able to prevent this increase. Renal Ang II concentration increased in SED-CAF, TF-NO and TF-CAF groups compared to the SED-NO. No differences were observed in the components of renal RAS ACE2/Ang 1-7/Mas. In conclusion, AET prevented the renal damage caused by cafeteria diet, such as lipid accumulation, increased GFR and reduced Bowman space, and these responses are associated, at least in part, with greater activation of the AMPK protein independent of the RAS contribution

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The physiological state of menopause is characterized by an irreversible loss of ovarian function, with a resulting decrease in estrogen production, leading to the appearance of metabolic, cognitive, and behavioral alterations. For this reason, understanding how the decrease in the estrogen production contributes to the progress of menopausal symptoms can be very useful for the development of alternative therapies than hormone replacement therapy. In this context, the data show that ovariectomized Wistar rats treated with (PhSe)2 at a dose of 5 mg/kg once a day for 30 days presented lower plasma triglyceride levels and increased HDL levels when compared to control ones. Moreover, (PhSe)2 administration reduced the weight gain and fat abdominal accumulation induced by ovariectomy. It was also observed that (PhSe)2 treatment improved hepatic oxidative stress parameters in ovariectomized rats (ascorbic acid and reduced glutathione levels, and glutathione S-transferase and catalase activities). Additionally, (PhSe)2 treatment at a dose of 5 mg/kg once a day for 30 days improved the performance of ovariectomized Wistar rats in the Morris Water Maze test, possibly by inhibiting the increase in brain acetylcholinesterase activity induced by ovariectomy. The present results suggest a promising role of (PhSe)2 against the cognitive decline related to menopause. The transition to menopause is associated with an increased risk of depressed mood. On this bases, the obtained results demonstrate that the prolongation of immobility time in the tail suspension test and forced swimming test in ovariectomized mice submitted to subchronic stress protocol was prevented by (PhSe)2 treatment at a dose of 10 mg/kg. It was also found a possible involvement of the serotonin system in this effect, demonstrated by the modulation of 5-HT2A/2C and 5-HT3 receptor subtypes. Although (PhSe)2 had inhibited in vitro monoamine oxidase A and B activities, treatment of ovariectomized mice with (PhSe)2 did not alter neither MAO-A nor MAO-B ex vivo activity. These findings suggest that (PhSe)2 treatment could influence mood and behavior in postmenopausal women. In order to investigate a possible mechanism of action for the hypocholesterolemic effect of (PhSe)2 it was observed that (PhSe)2 treatment increases the LDL receptor levels and augment the adenosine monophosphate (AMP)-activated kinase (AMPK) activation state without inhibiting directly 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR) enzyme activity in HepG2 cell cultures. These findings are in accordance with those from in vivo studies previously published. In addition, L6 skeletal muscle cells treated with (PhSe)2 presented an augment in glucose transporter 4 (GLUT4) translocation from the cytosol to the cell membrane via an increase in AMPK phosphorylation state, which could be linked to the hypoglycemic properties presented by (PhSe)2 in other studies. In conclusion, the body of evidence presented in this thesis points to the use of (PhSe)2 as a promising alternative therapy for the management of postmenopausal symptoms. However, it is important to mention that the global net effects of (PhSe)2 still need to be better described in order to identify possible negative side effects. / A menopausa caracteriza-se pela suspensão irreversível da função ovariana, com declínio da produção de hormônios estrogênicos. A falta desses hormônios culmina no aparecimento de alterações metabólicas, cognitivas e comportamentais. Por essa razão, entender de que maneira a depleção de hormônios ovarianos contribui para o surgimento dos sintomas característicos da menopausa pode ser extremamente útil para o desenvolvimento de tratamentos alternativos à terapia de reposição hormonal. Nesse contexto, os dados aqui apresentados demonstram que ratas Wistar ovariectomizadas que foram tratadas com disseleneto de difenila [(PhSe)2] na dose de 5 mg/kg uma vez ao dia durante um período de 30 dias possuíam reduzidos níveis plasmáticos de triglicerídeos e aumentados níveis de HDL quando comparadas as ratas controle não ovariectomizadas. Além disso, a administração de (PhSe)2 foi capaz de reduzir o ganho de peso e o acúmulo de gordura abdominal nas ratas ovariectomizadas. Também foi observado que o tratamento com (PhSe)2 melhorou parâmetros hepáticos relacionados a estresse oxidativo nas ratas ovariectomizadas (níveis de ácido ascórbico e glutationa reduzida (GSH) e atividade das enzimas glutationa S-transferase e catalase). O tratamento com (PhSe)2 na dose de 5 mg/kg uma vez ao dia durante um período de 30 dias também melhorou o desempenho das ratas Wistar ovariectomizadas no teste do Labirinto Aquático de Morris, possivelmente por impedir o aumento da atividade da enzima acetilcolinesterase cerebral observado nas ratas ovariectomizadas. Dessa forma, os resultados sugerem um possível efeito benéfico do (PhSe)2 para o tratamento do declínio cognitivo associado a menopausa. Ainda com relação aos sintomas apresentados pelas mulheres durante a menopausa, dados da literatura mostram que a transição para a menopausa associa-se a um risco aumentado para o aparecimento de sintomas do tipo depressivos. Com base nisso, foi evidenciado que fêmeas ovariectomizadas de camundongos Swiss submetidas a um protocolo de estresse sub-crônico apresentavam aumento no tempo de imobilidade nos testes de Suspensão da Cauda e do Nado Forçado, ambos preditivos de comportamento do tipo depressivo.Também foi observado que esse prolongamento no tempo de imobilidade apresentado pelas fêmeas ovariectomizadas foi prevenido pelo tratamento com (PhSe)2 na dose de 10 mg/kg administrado 30 minutos antes de cada exposição ao protocolo de estresse. Além disso, evidenciou-se o envolvimento dos receptores de serotonina do tipo 5-HT2A/2C e 5-HT3 no efeito do tipo antidepressivo apresentado pelo (PhSe)2. Embora o (PhSe)2 tenha inibido a atividade de ambas isoformas da enzima monoamino oxidase (MAO-A e MAO-B) in vitro, não foi observada inibição da atividade de tais enzimas quando sua atividade foi determinada ex vivo. Com base nesses resultados sugere-se que o tratamento com (PhSe)2 pode influenciar aspectos relacionados ao humor e ao comportamento em mulheres no período pós-menopausa. No intuito de elucidar os mecanismos envolvidos no efeito hipocolesterolêmico do (PhSe)2 em culturas de células HepG2 observou-se que este composto orgânico de selênio leva a um aumento nos níveis de receptores de LDL e a um aumento no estado de ativação da enzima adenosina monofosfato (AMP) quinase (AMPK), sem inibir diretamente a atividade da HMG-CoA redutase. Esses resultados corroboram com os achados de outros trabalhos, os quais demonstram um efeito hipocolesterolêmico do (PhSe)2 in vivo. Além disso, também foi buscado um possível mecanismo para o efeito hipoglicemiante apresentado pelo (PhSe)2 em trabalhos anteriores: resultados obtidos a partir de culturas de células L6 (células de músculo esquelético de ratos), sugerem que o (PhSe)2 aumenta a translocação do transportador de glicose 4 (GLUT4) do citosol para a membrana celular devido a um aumento no estado de ativação da enzima AMPK. Em conclusão, o conjunto de resultados apresentado nesta tese aponta o uso do (PhSe)2 como uma terapia alternativa bastante promissora para o tratamento de algumas das principais conseqüências da menopausa, a saber aumento no ganho de peso, dislipidemia, prejuízos cognitivos e ocorrência de episódios depressivos. Entretanto, faz-se importante mencionar que os efeitos globais do (PhSe)2 ainda precisam ser melhor caracterizados no intuito de verificar a existência de possíveis efeitos adversos.

Les tumeurs solides sont souvent confrontées à un environnement déficient en oxygène, dit hypoxique. Hypoxia-Inducible Factor 1 (HIF1) est le facteur de transcription clé de l’adaptation cellulaire à l’hypoxie, régulant de nombreux gènes impliqués dans l’angiogenèse, le métabolisme cellulaire ou la régulation du pH. Ma thèse s’articule en trois axes autour de HIF1 et de la reprogrammation métabolique hypoxique. J’ai d’abord étudié Factor-Inhibiting HIF1 (FIH), l’un des deux senseurs d’oxygène régulant HIF1. Nous avons montré que FIH est essentiel dans le développement tumoral en inhibant à la fois l’activité transcriptionnelle de HIF1 et la voie p53-p21. J’ai ensuite étudié le « shift » du métabolisme cellulaire vers la glycolyse induit par HIF1, générant une addiction pour le glucose. Nos travaux ont montré que paradoxalement, les cellules hypoxiques synthétisent du glycogène via HIF1 constituant ainsi une réserve de glucose intracellulaire. Le glycogène confère alors une résistance accrue des cellules tumorales suite à une carence en glucose. Enfin, j’ai pu montrer que l’AMPK, « gardien de la balance énergétique », n’est pas nécessaire au maintien d’un niveau viable d’ATP suite à l’inhibition de la glycolyse, via le blocage de l’export de lactate, mais exerce, un effet protecteur en absence de glucose. Cependant, l’inhibition conjointe du transporteur de lactate, MCT4, et de l’AMPK réduit fortement le développement tumoral dans un modèle de xénogreffes chez la souris, suggérant un rôle crucial de ces deux acteurs dans ce contexte. L’ensemble de ces travaux a permis d’identifier plusieurs cibles potentielles impliquées dans la plasticité métabolique en hypoxie. / Cells of solid tumors are often exposed to an environment deficient in oxygen, i.e. hypoxic. The Hypoxia-Inducible Factor-1 (HIF-1) is the major transcription factor involved in cellular adaptation to hypoxia. HIF-1 regulates a wide array of genes involved in angiogenesis, cellular metabolism or pH regulation. My thesis is organized into three axes around HIF-1 and metabolic reprogramming in hypoxia. I first studied Factor-Inhibiting HIF-1 (FIH), one of two oxygen sensors regulating HIF-1. We showed that FIH is essential for tumor development through inhibition of the HIF-1 transcriptional activity as well as through the suppression of the p53-p21 axis. I then studied the HIF-1-induced « shift » in cellular metabolism toward glycolysis, which generates a type of “glucose addiction”. We showed that paradoxically, tumor cells store glycogen in hypoxia through a HIF-1 dependant mechanism. Glycogen served as a reservoir of intracellular glucose, which allows hypoxic cells to survive periods of glucose starvation. Finally, I studied AMPK «the guardian of energy », and showed that surprisingly, this kinase is not necessary in maintaining a viable level of ATP when glycolysis is inhibited (by blockade of lactate export). However, as expected, AMPK protected cells during glucose starvation. Moreover, combined inhibition of the lactate transporter MCT4 and of AMPK reduced dramatically tumor development in a xenograft model, suggesting a crucial role for these two actors in the context of growth of tumor cells in a hostile environment. Taken together these results identified several potential drug targets involved in the metabolic plasticity of hypoxic cells.

La stéatose hépatique affecte 20 à 40% de la population et progresse de façon constante. Il s’agit d’une pathologie chronique fortement associée au syndrome métabolique. Sa pathogenèse est mal comprise. Une altération du métabolisme des lipides dans le foie entraînant une accumulation intra-hépatique de lipides est probablement la cause majeure de la stéatose hépatique. A ce jour, il n’existe pas de traitement spécifique de la stéatose hépatique. La protéine kinase activée par l’AMP (AMPK) est un régulateur clé du métabolisme énergétique. Notamment, l’AMPK contrôle le métabolisme des lipides en inhibant la synthèse des acides gras et du cholestérol, et en stimulant l'oxydation des acides gras. Plusieurs études ont montré l’existence d’une association entre l’accumulation intracellulaire de lipides et une perte d’activité de l’AMPK dans le foie. Ces observations suggèrent que l’AMPK pourrait être un facteur impliqué dans la physiopathologie de la stéatose hépatique. Pour étudier cette hypothèse, nous avons généré un nouveau modèle de souris knockout dépourvu des sous-unités catalytiques α1 et α2 de l’AMPK spécifiquement dans le foie. Nous avons analysé les conséquences de cette délétion sur le métabolisme lipidique dans différentes situations nutritionnelles. La délétion de l’AMPK dans le foie ne modifie pas le contenu hépatique en triglycérides et en cholestérol au cours d’un jeûne ou après une réalimentation riche en glucides. Egalement, l’expression des gènes de la lipogenèse n’est pas modifiée dans le foie de ces animaux. De plus, l’oxydation des acides gras n’est pas altérée même après un jeûne de 24h. Etonnamment, l’absence de l’AMPK dans le foie n’amplifie pas la stéatose hépatique, ni l’hyperglycémie ou l’intolérance au glucose lorsque les souris sont nourries avec un régime riche en lipides. Cependant, l’activation de l’AMPK in vivo avec l'activateur direct, A-769662, normalise la stéatose hépatique chez des souris lipodystrophiques aP2-SREBP-1c et chez des souris obèses nourries avec un régime riche en lipides. Cet effet est dépendant de l’AMPK car il est totalement perdu chez des souris dépourvues d’AMPK dans le foie. Dans des hépatocytes de souris en culture primaire, l’activation de l'AMPK par un activateur direct (A-769662) ou par des activateurs indirects (metformine et AICAR) réduit le flux lipogénique et augmente l’oxydation des acides gras. Ces effets sont totalement abolis dans des hépatocytes AMPK KO, démontrant l’action spécifique de l'AMPK sur le métabolisme lipidique en réponse à ces composés. Ces résultats obtenus chez la souris sont extrapolables à l'homme puisque nous avons montré que l'activation de l'AMPK dans des hépatocytes humains en culture primaire inhibe de manière efficace la synthèse des acides gras et du cholestérol. En conclusion, nos résultats démontrent que l’inactivation de l’AMPK dans le foie n’est pas un facteur déclenchant ou aggravant dans la physiopathologie de la stéatose hépatique. En revanche, l’activation pharmacologique de l’AMPK améliore efficacement la stéatose hépatique. Ainsi, l’AMPK est une cible potentielle pour le développement d'activateurs dans le but de traiter la stéatose hépatique chez l’homme. / Fatty liver disease affects between 20-40% of the population. This pathology is usually associated with metabolic disease. Its pathogenesis is poorly understood. Altered lipids metabolism in the liver resulting on hepatic fat accumulation is probably due to fatty liver. There is no specific treatment for fatty liver disease. AMP-activated protein kinase (AMPK) is a key regulator of energy metabolism. In particular, AMPK regulates lipid metabolism by inhibiting fatty acids and cholesterol synthesis, and stimulating fatty acids oxidation. Several studies have shown an association between intracellular lipid accumulation and loss of AMPK activity in the liver. These observations suggest that AMPK may be a factor involved in the pathogenesis of hepatic steatosis. To investigate this hypothesis, we generated a new model of knockout mice lacking the catalytic subunits of AMPK α1 and α2 specifically in the liver. We analyzed the consequences of this deletion on lipid metabolism in different nutritional conditions. Deletion of AMPK in the liver does not affect hepatic triglyceride and cholesterol content in fasted or in refed conditions with a high carbohydrate diet. Also, lipogenic genes expression is not altered in the liver of these animals. Moreover, the oxidation of fatty acids is not impaired after 24 hour of fasting. Surprisingly, lacking AMPK specifically in the liver does not aggraving fatty liver, hyperglycemia, or impaired glucose tolerance when the mice are on high fat diet condition. However, the activation of AMPK in vivo with a direct activator, A-769662, normalizes hepatic steatosis in lipodystrophyc aP2-SREBP-1c mice and in obese mice placed on high-fat diet. This effect is AMPK dependent because it is completely abolished in mice lacking AMPK specifically in liver. In primary mice hepatocytes, AMPK activation by a direct activator (A-769662) or by indirect activators (metformin and AICAR) reduces lipogenesis rates and increases fatty acids oxidation rates. These effects were completely abolished in hepatocytes lacking AMPK, showing the specific action of AMPK on lipid metabolism in response to these compounds. These results obtained in mice can be extrapolated to humans. Indeed, we have shown that AMPK activation in primary humain hepatocytes inhibits effectively fatty acid and cholesterol synthesis rates. In conclusion, our results showed that inactivation of AMPK in the liver is not a triggering or an aggraving factor in the pathogenesis of hepatic steatosis. Nevertheless, AMPK re-activation has a therapeutic benefit for the treatment of fatty liver disease. Thus, AMPK is a potential target to treat fatty liver disease in human.

Rapidly growing tumor cells outgrow their blood supply resulting in a microenvironment with reduced oxygen and nutrients. Using an in vitro transformation model we found that cancer cells expressing the SV40 ST antigen (+ST cells) are more resistant to glucose deprivation-induced cell death than cells lacking the SV40 ST antigen (−ST cells). Mechanistically, we found that the ST antigen mediates this effect by activating a nutrient-sensing kinase, AMP-activated protein kinase (AMPK). We further show that AMPK mediates its effects, at least in part, by inhibiting mTOR (mammalian target of rapamycin), thereby shutting down protein translation, and by inducing autophagy as an alternate energy source. Resistance to anoikis upon anchorage-deprivation is yet another form of stress tolerated by both normal stem/progenitor cells of various tissues in our body and by cancer cells. Using mammospheres as a model to enrich for stem/progenitor cells we found that mammosphere formation is accompanied with increased activation of AMPK. Concomitant with AMPK activation, we detected increased phosphorylation of the anti-apoptotic protein PED/PEA15. We further demonstrate that AMPK directly interacts with and phosphorylates PEA15 at Ser116, thus establishing PEA15 as a new AMPK target. Thus, our study has identified AMPK-PEA15 signaling as a key component of sphere formation by both normal and cancerous breast tissues. During metastasis, epithelial cells lose attachments to their neighbors, acquire a mesenchymal-like morphology, a process termed as epithelial-mesenchymal transition (EMT) and become motile. Our results indicate that AMPK regulates EMT by both transcriptional and post-translational modification of EMT-inducing transcription factor, Twist. Thus, our study has identified a role for AMPK in nutrient deprivation, anchorage-independent growth, and epithelial-mesenchymal transition involved in metastasis. In addition, we have identified two novel substrates of AMPK, PEA15 and Twist, that may play key roles in cancer progression. Thus, our study suggests that targeting AMPK, or its newly identified substrates, can be explored as possible anti-cancer mechanisms.

Le déficit héréditaire en Carnitine Palmitoyl Transférase 2 (CPT2), l’un des déficits de l’oxydation mitochondriale des acides gras (OAG) les plus fréquents, est caractérisé dans sa forme adulte par une myopathie métabolique avec des épisodes récurrents de douleurs musculaires, de myoglobinurie et de rhabdomyolyse, habituellement déclenchés par un exercice prolongé ou un jeûne. A l’heure actuelle, il n’y a pas de traitement pharmacologique efficace pour la correction de ce déficit à l’exception de prise en charge nutritionnelle. Mon travail de thèse a porté sur l’étude du potentiel thérapeutique du composé GSK773 un activateur direct de l’AMP-activated Protein Kinase (AMPK), un senseur énergétique de la cellule, dans des myotubes de quatre patients déficitaires en CPT2. En effet, l'AMPK est considérée comme une cible thérapeutique potentielle dans de nombreux troubles métaboliques ou neurodégénératifs courants associés aux dysfonctionnements mitochondriaux. Nous montrons que le composé GSK773 est capable de stimuler les capacités résiduelles de l’OAG et de corriger le flux d’OAG dans des myotubes déficitaires en CPT2 (n=4) après un traitement par 30µM pendant 48h. L’étude par western-blot et par immunofluorescence montre que le GSK773 augmente la quantité de protéine mutante CPT2. L'analyse des intermédiaires C16-acylcarnitines montre que les myotubes déficients en CPT2 présentent, comme prévu, une accumulation de C16-acylcarnitines significativement diminuée après le traitement par le GSK773. De manière intéressante, l'IF et l’xCELLigence, une nouvelle technique basée sur la mesure de l’impédance électrique en temps réel, montrent un processus de différenciation altéré dans les myotubes de patients déficitaires en CPT2 par rapport aux cellules témoins, qui est corrigé par le GSK773. Nous avons également montré que le GSK773 induit une conversion des fibres musculaires vers les fibres de type I lentes/oxydatives, mais aussi une amélioration générale de la qualité du réseau mitochondrial accompagnée d’une biogenèse mitochondriale et une augmentation du niveau de ROS suggérant que le GSK773 agirait sur la plasticité musculaire. D’un point de vue mécanistique, nous avons montré que les effets du GSK773 passent par l’AMPK, PGC-1α, p38 MAPK et les ROS. Ainsi, ces résultats suggèrent que le GSK773 améliore les paramètres métaboliques et structuraux dans les myotubes déficients en CPT2 et que l'AMPK pourrait représenter une cible thérapeutique hautement pertinente pour la correction pharmacologique du déficit en CPT2. / Carnitine Palmitoyl Transferase 2 (CPT2) deficiency is among the most common inherited defects of mitochondrial fatty acid oxidation (FAO). A frequent phenotype is an early adult-onset myopathy characterized by recurrent episodes of muscle pain, myoglobinuria and rhabdomyolysis usually triggered by prolonged exercise or fasting. To date, there is no treatment of this disorder other than dietary management. AMPK is considered as a potential therapeutic target in many common metabolic or neurodegenerative disorders associated to mitochondrial dysfunctions. Thus, we tested the therapeutic potential of the direct AMPK activator GSK773 in myotubes from four CPT2-deficient patients. We show that GSK773 is able to stimulate residual FAO capacities in a dose- and time-dependent manner. Correction of CPT2 defect is achieved after treatment with GSK773 at 30µM for 48h. Western-blots analysis and Immunostaining shows that GSK773 increases the amount of CPT2 mutant protein. Analysis of acylcarnitine intermediates in the culture media shows that CPT2-deficient myotubes exhibit, as expected, an accumulation of C16-acylcarnitines that is significantly decreased after GSK773 treatment. Surprisingly, immunofluorescence and xCELLigence (a real-time monitoring of cell culture technic) show an impaired differentiation process in CPT2-deficient myotubes that is corrected by GSK773. We also show that GSK773 induces a shift in myosin-heavy-chain isoforms toward slow oxidative fiber types, improves the quality of mitochondrial network with an induction of mitochondrial biogenesis and increases ROS levels, suggesting that GSK773 might induce muscle plasticity. Finally, from a mechanistic point of view, siRNAs experiments showed that the effects triggered by GSK773 implicate AMPK, PGC-1α, ROS and p38 MAPK. Altogether these results suggest that GSK773 improves metabolic and structural parameters in CPT2-deficient myotubes and that AMPK might represent a highly relevant therapeutic target for pharmacological correction of inborn CPT2 deficiency.