Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O sobrepeso e a obesidade na adolescência atingiram proporções epidêmicas na maior parte dos países industrializados bem como as alterações no metabolismo da glicose e dos triglicérides. As alterações no perfil do estado nutricional têm sido acompanhadas no aumento do consumo de bebidas açucaradas por adolescentes nos últimos anos. Algumas revisões sistemáticas recentes identificaram que o consumo de bebidas açucaradas associa-se ao ganho de peso entre a população em geral, inclusive em adolescentes e o efeito de tais bebidas vem sendo demonstrado não só na ocorrência do sobrepeso e obesidade, como também em associação com alterações metabólicas, hipertensão, esteatose e a ocorrência de diabetes tipo 2. Um efeito plausível do aumento no consumo de bebidas açucaradas seria a alteração nos triglicérides e no controle glicêmico, mas somente dois estudos seccionais, em adolescentes americanos, foram encontrados e ambos concluíram pelo efeito deletério do consumo de tais bebidas nesses parâmetros metabólicos. A presente tese teve como objetivo realizar uma revisão bibliográfica sobre consumo de bebidas açucaradas e alterações metabólicas em adolescentes. E avaliar essa associação em uma amostra probabilística de escolares da cidade de Niterói, RJ, com 610 adolescentes de 12 a 19 anos. Na revisão foram resgatados apenas dois artigos. No primeiro encontrou-se que para cada porção adicional de bebidas açucaradas consumidas por dia, houve aumento de 7% nos valores de HOMA-IR, aumento de 2,25mg/dL nas concentrações de triglicérides, diminuição de 0,73mg/dL de HDL-C nas meninas e redução de 0,35mg/dL de HDL-C nos meninos (p-valor<0,05). No segundo, foi observada uma tendência das bebidas açucaradas a explicar 2,4% da variância em AIR (&#946;=-0,219, p-valor=0,07), sem diferença entre os sexos. Com relação às analises apresentadas com os adolescentes da cidade de Niterói, as meninas apresentaram, em média, menor consumo de bebidas açucaradas do que os meninos (222 vs. 262mL), sendo a prevalência de consumo diário acima de 75% para ambos os sexos. A ingestão total de calorias e carboidratos entre os meninos que consomem bebidas açucaradas foi maior comparada aos que não consomem (2.183 vs. 2.787kcal e 286,3 vs. 376,6g; respectivamente). No modelo final de regressão, o consumo de bebidas açucaradas apresentou uma associação positiva, apenas para triglicérides, nos meninos após ajuste por idade, IMC, energia e carboidrato, (&#61538;=0,06; p=0,04). Em conclusão, tanto na revisão da literatura, quanto na análise dos dados, encontrou-se associação positiva entre o consumo de bebidas açucaradas e alterações metabólicas / Overweight and obesity among adolescents, as well as changes in the metabolism of glucose and triglycerides, have reached epidemic proportions in most industrialized countries. Changes in nutritional status have been followed by increased consumption of sugar beverages. Some systematic reviews have identified that the consumption of sugar beverages is associated with weight gain among general population, including adolescents. The effect of these beverages seems to influence not only the occurrence of overweight and obesity, but also in other diseases associated to obesity, as hypertension, hepatic steatosis and occurrence of type 2 diabetes. A reasonable effect of the increase in the sugar drink consumption would be the alteration in triglicérides and the glicêmico control, but two studies you only part, in American adolescents, had been found and both had concluded for the deleterious effect of the consumption of such drinks in these metabolic parameters.The present thesis had as objective to carry through a bibliographical revision on sugar drink consumption and metabolic alterations in adolescents. E to evaluate this association in pertaining to school a probabilist sample of the city of Niterói, Rio de Janeiro, with 610 adolescents of 12 the 19 years. In the revision only two articles had been rescued. In the first one one met that for each additional portion of sugar drinks consumed per day, it had increase of 7% in the values of HOMA-IR, increase of 2,25mg/dL in the concentrations of triglicérides, reduction of 0,73mg/dL of HDL-C in the girls and reduction of 0,35mg/dL of HDL-C in the boys (p-valor<0,05). In as, insulin was observed a trend of sugar drinks to explain 2.4% of the variance in AIR - Acute response (&#946;=-0,219, p-valor=0,07), without difference between the sexos. With the adolescents of the city of Niterói, girls reported, on average, a lower sugar beverage consumption than boys (222 vs. 262mL), and the prevalence of daily consumption was grether than 75% for both sexes. Boys who drink sugar beverages presented higher energy and carbohydrates intakes than those who did not drink sweetened beverages (2.183 vs. 2.787kcal and 286.3 vs. 376.6 g, respectively). In the final regression model the consumption of sweetened beverages showed a positive association only for triglycerides in boys, after adjusting for age, BMI, energy and carbohydrate inatke, (&#61538;= 0.06, p = 0.04). In conclusion, both the literature reviewed and the data analysis from adolescents of Niterói revealed a positive association between sugar beverage consumption and metabolic changes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O sobrepeso e a obesidade na adolescência atingiram proporções epidêmicas na maior parte dos países industrializados bem como as alterações no metabolismo da glicose e dos triglicérides. As alterações no perfil do estado nutricional têm sido acompanhadas no aumento do consumo de bebidas açucaradas por adolescentes nos últimos anos. Algumas revisões sistemáticas recentes identificaram que o consumo de bebidas açucaradas associa-se ao ganho de peso entre a população em geral, inclusive em adolescentes e o efeito de tais bebidas vem sendo demonstrado não só na ocorrência do sobrepeso e obesidade, como também em associação com alterações metabólicas, hipertensão, esteatose e a ocorrência de diabetes tipo 2. Um efeito plausível do aumento no consumo de bebidas açucaradas seria a alteração nos triglicérides e no controle glicêmico, mas somente dois estudos seccionais, em adolescentes americanos, foram encontrados e ambos concluíram pelo efeito deletério do consumo de tais bebidas nesses parâmetros metabólicos. A presente tese teve como objetivo realizar uma revisão bibliográfica sobre consumo de bebidas açucaradas e alterações metabólicas em adolescentes. E avaliar essa associação em uma amostra probabilística de escolares da cidade de Niterói, RJ, com 610 adolescentes de 12 a 19 anos. Na revisão foram resgatados apenas dois artigos. No primeiro encontrou-se que para cada porção adicional de bebidas açucaradas consumidas por dia, houve aumento de 7% nos valores de HOMA-IR, aumento de 2,25mg/dL nas concentrações de triglicérides, diminuição de 0,73mg/dL de HDL-C nas meninas e redução de 0,35mg/dL de HDL-C nos meninos (p-valor<0,05). No segundo, foi observada uma tendência das bebidas açucaradas a explicar 2,4% da variância em AIR (&#946;=-0,219, p-valor=0,07), sem diferença entre os sexos. Com relação às analises apresentadas com os adolescentes da cidade de Niterói, as meninas apresentaram, em média, menor consumo de bebidas açucaradas do que os meninos (222 vs. 262mL), sendo a prevalência de consumo diário acima de 75% para ambos os sexos. A ingestão total de calorias e carboidratos entre os meninos que consomem bebidas açucaradas foi maior comparada aos que não consomem (2.183 vs. 2.787kcal e 286,3 vs. 376,6g; respectivamente). No modelo final de regressão, o consumo de bebidas açucaradas apresentou uma associação positiva, apenas para triglicérides, nos meninos após ajuste por idade, IMC, energia e carboidrato, (&#61538;=0,06; p=0,04). Em conclusão, tanto na revisão da literatura, quanto na análise dos dados, encontrou-se associação positiva entre o consumo de bebidas açucaradas e alterações metabólicas / Overweight and obesity among adolescents, as well as changes in the metabolism of glucose and triglycerides, have reached epidemic proportions in most industrialized countries. Changes in nutritional status have been followed by increased consumption of sugar beverages. Some systematic reviews have identified that the consumption of sugar beverages is associated with weight gain among general population, including adolescents. The effect of these beverages seems to influence not only the occurrence of overweight and obesity, but also in other diseases associated to obesity, as hypertension, hepatic steatosis and occurrence of type 2 diabetes. A reasonable effect of the increase in the sugar drink consumption would be the alteration in triglicérides and the glicêmico control, but two studies you only part, in American adolescents, had been found and both had concluded for the deleterious effect of the consumption of such drinks in these metabolic parameters.The present thesis had as objective to carry through a bibliographical revision on sugar drink consumption and metabolic alterations in adolescents. E to evaluate this association in pertaining to school a probabilist sample of the city of Niterói, Rio de Janeiro, with 610 adolescents of 12 the 19 years. In the revision only two articles had been rescued. In the first one one met that for each additional portion of sugar drinks consumed per day, it had increase of 7% in the values of HOMA-IR, increase of 2,25mg/dL in the concentrations of triglicérides, reduction of 0,73mg/dL of HDL-C in the girls and reduction of 0,35mg/dL of HDL-C in the boys (p-valor<0,05). In as, insulin was observed a trend of sugar drinks to explain 2.4% of the variance in AIR - Acute response (&#946;=-0,219, p-valor=0,07), without difference between the sexos. With the adolescents of the city of Niterói, girls reported, on average, a lower sugar beverage consumption than boys (222 vs. 262mL), and the prevalence of daily consumption was grether than 75% for both sexes. Boys who drink sugar beverages presented higher energy and carbohydrates intakes than those who did not drink sweetened beverages (2.183 vs. 2.787kcal and 286.3 vs. 376.6 g, respectively). In the final regression model the consumption of sweetened beverages showed a positive association only for triglycerides in boys, after adjusting for age, BMI, energy and carbohydrate inatke, (&#61538;= 0.06, p = 0.04). In conclusion, both the literature reviewed and the data analysis from adolescents of Niterói revealed a positive association between sugar beverage consumption and metabolic changes

Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-04-07T11:46:13Z No. of bitstreams: 1 renatamariadesouzaoliveiraesilva.pdf: 3447227 bytes, checksum: 5920ec03fc90e5a13eeef897064fe686 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-04-24T03:53:13Z (GMT) No. of bitstreams: 1 renatamariadesouzaoliveiraesilva.pdf: 3447227 bytes, checksum: 5920ec03fc90e5a13eeef897064fe686 (MD5) / Made available in DSpace on 2016-04-24T03:53:13Z (GMT). No. of bitstreams: 1 renatamariadesouzaoliveiraesilva.pdf: 3447227 bytes, checksum: 5920ec03fc90e5a13eeef897064fe686 (MD5) Previous issue date: 2013-06-27 / FAPEMIG - Fundação de Amparo à Pesquisa do Estado de Minas Gerais / A obesidade na adolescência tem sido considerada um problema de saúde pública, visto que a associação do excesso de peso com alterações metabólicas, como dislipidemia, hipertensão arterial, intolerância à glicose e doenças cardiovasculares, já podem ser observadas neste grupo em questão. Estudos recentes investigam o papel do cálcio e da vitamina D na prevenção de doenças crônicas, como hipertensão arterial, diabetes melitus e obesidade. Desta forma, o objetivo deste trabalho foi investigar a relação da ingestão de cálcio e vitamina D e níveis séricos de vitamina D com composição corporal e alterações metabólicas em adolescentes do município de Juiz de Fora. O estudo transversal foi realizado nas escolas de ensino médio da região central de Juiz de Fora com adolescentes de 15 a 17 anos de idade. Uma amostra de 302 estudantes foi selecionada após triagem e classificação do estado nutricional. Foram analisadas variáveis antropométricas, consumo alimentar, pressão arterial, nível de atividade física e variáveis comportamentais. Além disso, foram colhidas amostras de sangue para avaliação do perfil lipídico, glicemia e insulina de jejum. Valores de vitamina D e paratormônio foram analisados em uma sub-amostra. O banco de dados e as análises estatísticas foram realizados no software SPSS 17.0. Dentre os avaliados, 150 eram eutróficos e 152 (50,3%) apresentavam excesso de peso. A avaliação da composição corporal demonstrou que 97,4% e 52% dos adolescentes com sobrepeso/obesidade e eutróficos, respectivamente, apresentaram elevado percentual de gordura corporal. De acordo com a análise bioquímica, a maior alteração do perfil lipídico observada foi o aumento do colesterol total (40,4%). Com exceção da glicemia, os adolescentes com excesso de peso apresentaram maiores valores bioquímicos. A inadequação do percentual de macronutrientes em relação ao valor energético total (VET) denota semelhanças entre os sexos e entre adolescentes com e sem excesso de peso. Verificou-se maior percentual de adolescentes com excesso de peso com consumo de lipídios acima da AMDR (Acceptable Macronutrients Distribution Range), em relação aos eutróficos (62,9 vs 44,6%, p = 0,006). A análise de regressão logística demonstrou que a ingestão de alimentos diet/light (OR = 2,95; IC = 1,48–5,89; p=0,002), integrais (OR = 2,21; IC=1,25–3,91; p =0,006) e o elevado consumo de lipídeos (OR =1,81 (1,03–3,15; p=0,036) se comportaram como fatores associados ao excesso de peso. A partir da análise do QFCA, observou-se 23,9% e 16,5% de consumo diário de frutas e vegetais, respectivamente, não tendo sido encontrada associação significativa entre os grupos, perfil lipídico e sexo. Em relação ao consumo de leite e derivados, 59,5% dos adolescentes relataram ingerir diariamente, sendo este consumo maior entre os meninos (p = 0, 029). Somente 5,3% dos adolescentes apresentaram ingestão de cálcio acima da EAR -Estimated Average Requirement - (1100 mg/d). Indivíduos com excesso de peso apresentaram menor ingestão de cálcio que os eutróficos (p = 0,019). Foram observadas correlações negativas entre a ingestão de cálcio e IMC, circunferência da cintura e do quadril, relação cintura/quadril, percentual de gordura corporal, insulina, HOMA-IR e pressão arterial sistólica; e correlação positiva com HDL-colesterol (p < 0,05). Na análise bivariada, indivíduos com ingestão reduzida de cálcio apresentaram maiores chances de terem excesso de peso (OR= 1,85; p = 0,017), alto percentual de gordura corporal (OR= 2,08; p = 0,015), elevada razão cintura/estatura (OR = 1,91; p = 0,012) e hiperinsulinemia(OR = 1,94; p = 0,036). A deficiência e insuficiência de vitamina D foi observada em 1,25 e 70,6% dos adolescentes, respectivamente. Os níveis séricos de 25 (OH)D foram estatisticamente menores em indivíduos com excesso de peso, CC aumentada, hipercolesterolemia e hiperinsulinemia (P <0,05). A média de ingestão de vitamina D (2,18 mg/dia) foi menor do que a EAR. Menores valores de IMC e CC foram observadas entre indivíduos que se encontravam no 3º tercil de ingestão de vitamina D. Este é um dos poucos estudos que investiga a relação da ingestão de cálcio e vitamina D com adiposidade e alterações metabólicas em adolescentes. Esses resultados suportam a função extra-esquelética destes micronutrientes no grupo. Apesar do Brasil ser um país de clima tropical, elevada frequência de insuficiência desta vitamina foi encontrada neste trabalho. / Adolescent obesity has been considered a public health problem, since the association of excess weight with metabolic abnormalities such as dyslipidemia, hypertension, glucose intolerance, and cardiovascular disease can be readily observed in the group in question here. Recent studies investigate the role of calcium and vitamin D in the prevention of chronic diseases such as hypertension, diabetes, and obesity. Thus, the aim of this study was to investigate the relation of calcium and vitamin D intake, and serum vitamin D, with body composition and metabolic alterations, in adolescents from the Juiz de For a city. The cross-sectional study was conducted in high schools in the central city area of Juiz de Fora with adolescents from 15 to 17 years of age. A sample of 302 students was selected after screening and classification of nutritional status. The analysis included anthropometric variables, nutrient intake, arterial blood pressure, physical activity level, and behavioral variables. In addition, blood samples were collected to evaluate lipid profile, fasting glucose, and fasting insulin. Levels of vitamin D and parathyroid hormone were analyzed on a sub-sample. The database and the statistical analyses were processed using SPSS 17.0. Among the participants, 150 were eutrophic and 152 (50.3%) were overweight. According to biochemical analysis, the highest observed lipid profile alteration was increased total cholesterol (40.4%). With the exception of blood glucose, the overweight teens showed higher biochemical levels. The inadequacy in the percentage of macronutrients in relation to the TEI indicates similarities between the groups and across gender. A higher percentage of overweight adolescents with a fat intake above the AMDR was seen in comparison with eutrophic individuals (62.9 vs. 44.6%, p = 0.006). Logistic regression analysis showed that the ingestion of diet / light foods (OR = 2.95; CI = 1.48-5.89; p = 0.002), whole foods (OR = 2.21; CI = 1.25-3.91; p = 0.006), and high fat diets (OR = 1.81; CI = 1.03-3.15; p = 0.036) serve as factors associated with excess weight. Based on the analysis of the FFQ, a 23.9% and 16.5% daily consumption of fruits and vegetables, respectively, was observed, with no significant association between the groups, lipid profile, and gender. Regarding the consumption of milk and dairy products, 59.5% of the adolescents reported a daily intake, being higher among boys (p = 0.029). Only 5.3% of the adolescents had adequate calcium intake (1100 mg/d). Overweight individuals had a lower calcium intake than those with normal weight (p = 0.019). Negative correlations were observed for calcium intake with BMI, waist and hip circumference, waist / hip ratio, body fat percentage, insulin, HOMA-IR, and systolic blood pressure; and a positive correlation with HDL-cholesterol (p < 0.05). In the bivariate analysis, individuals with low calcium intake were more likely to be overweight (OR = 1.85; p = 0.017), have a high body fat percentage (OR = 2.08; p = 0.015), an elevated waist / height ratio (OR = 1.91; p = 0.012), and hyperinsulinemia (OR = 1.94; p = 0.036). Vitamin D deficiency and insufficiency was observed in 1.25% and 70.6% of the adolescents, respectively. Serum levels of 25 (OH) D were significantly lower in individuals with excess weight, increased WC, hypercholesterolemia, and hyperinsulinemia (p < 0.05). Mean Vitamin D intake (2.18 mg/day) was lower than the EAR. Lower values for BMI and WC were observed among individuals who were in the 3rd tertile of vitamin D intake. This is one of the few studies investigating calcium and vitamin D intake along with adiposity and metabolic alterations in adolescents. This results verify the extra-skeletal function of these micronutrients in the group. Though Brazil is a tropical country, a high frequency of insufficiency of this vitamin was found in this study.

La séquence des événements moléculaires engendrés par des perturbations de signaux externes qui peuvent affecter les horloges circadiennes, et générer des pathologies restait peu connue. Durant ma thèse, j’ai démontré au niveau moléculaire, comment déplacer l’horaire de l'alimentation chez la souris de la phase active à la phase de repos, altère le métabolisme à la suite d’une hypoinsulinémie durant la phase active, ce qui provoque une activation de PPARα qui reprogramme le métabolisme et l'expression de RevErbα et qui de ce fait décale l’horloge de 12h dans les tissus périphériques. Notamment, l’absence de PPARα dans le noyau suprachiasmatique empêche le décalage de l’horloge centrale. Ainsi, les phases d’activité et de repos contrôlées par l’horloge centrale ne sont plus alignées avec l'expression des gènes contrôlée par les horloges périphériques. Ce non-alignement crée un syndrome métabolique similaire à celui observé chez des individus soumis à des horaires de travail décalés. / The sequence of molecular events through which alterations in externals cues may impinge on circadian clocks, and generate pathologies, was mostly unknown. During my thesis work, I have molecularly deciphered, how switching feeding in mice, from the “active” to the "rest" phase [Restricted Feeding (RF)] , alters the metabolism through hypoinsulinemia during the “active” phase, leading to increased PPARα activity, thereby reprograming both metabolism and RevErbα expression and leads to a 12h circadian clock-shift in peripheral tissues.Most notably, the lack of PPARα expression in the suprachiasmatic nuclei (SCN) prevents a shift of the central clock. Therefore, the “active” and “rest” phases controlled by the SCN clock and gene expression controlled by the peripheral circadian clocks are misaligned. Most interestingly, this misalignment generates a metabolic syndrome-like pathology, similar to that associated with shiftwork schedules.

La sénescence cellulaire est une barrière à la progression tumorale qui est contournée par les cellules cancéreuses. Elle se met en place suivant différents événements tels que l’activation constante d’oncogènes comme H-RAS et correspond à un arrêt stable du cycle cellulaire. Un autre aspect des cellules sénescentes est la dégradation spécifique des protéines impliquées dans la régulation du cycle cellulaire, la biogenèse des ribosomes, l’homéostasie mitochondriale et le métabolisme cellulaire. Dans cette étude, nous voulions identifier quelles sont les contributions de la dégradation des protéines spécifiques à l’homéostasie mitochondriale, au métabolisme cellulaire ainsi qu’à la biogenèse des ribosomes. De plus, nous voulons voir comment la dégradation des protéines impliquées dans ces voies affecte la sénescence cellulaire. Afin de répondre à ces questions, nous avons divisé nos travaux en 2 parties. La première s’est concentrée sur les ribosomes et les altérations de la biogenèse ribosomale dans la sénescence. La deuxième partie s’est focalisée sur la contribution de la dégradation des protéines importantes pour le métabolisme cellulaire et l’homéostasie mitochondriale. Premièrement, nous avons identifié que la mise en place de la sénescence s’accompagne d’une désynchronisation de la biogenèse des ribosomes. Plus précisément, certains ARNr sont moins transcrits alors que la transcription de certaines protéiques ribosomiques n’est pas altérée. Ceci entraîne un déséquilibre entre la quantité des protéines ribosomiques et celle des ARN ribosomiques. Il provoque l’accumulation de ribo protéines en dehors des ribosomes. Ces protéines acquièrent en conséquence de nouvelles fonctions. Nous avons identifié RPL29 comme une ribo protéine libre du ribosome. Elle est accumulée dans les cellules sénescentes et peut être utilisée comme nouveau biomarqueur afin d’identifier les cellules senescent in vitro et in vivo. L’identification d’un nouveau biomarqueur de cellules sénescentes est cruciale car aucun marqueur spécifique de la sénescence n’est encore disponible. Par ailleurs, nous avons identifié RPS14 comme une protéine qui peut interagir avec le complexe CDK4-cyclin D1 et ainsi, en inhibant son activité, elle limite la prolifération cellulaire. L’arrêt du cycle cellulaire initié par cette protéine ribosomqiue hors du ribosome est indépendant de la protéine suppressive p53. Ceci pourrait offrir une opportunité thérapeutqiue pour le traitement des tumeurs déficientes pour l’expression de p53. La deuxième partie de ce travail s’est concentrée sur les altérations du métabolisme cellulaire en particulier le métabolisme du NAD et l’homéostasie mitochondriale. Dans un premier temps, nous avons confirmé que la perte d’expression de protéines impliquées dans l’homéostasie mitochondriale favorise la mise en place de la sénescence via l’accumulation de NADH et la stabilisation de p53. De plus, nous avons observé que la diminution des régulateurs de l’homéostasie redox NAD+ et NADPH est suffisante pour induire l’entrée en sénescence. A l’inverse la normalisation de ce paramètre est à l’origine d’un contournement de la sénescence. Dans ce cadre, nous avons identifié un nouveau complexe protéique formé par l’enzyme malique, la malate déshydrogénase et la pyruvate carboxylase dont les actions concertées transfèrent l’ion hydrure du NADH vers le NADPH. Nous avons nommé ce complexe HTC pour complexe de transfert d’hydrure. Les réactions métaboliques des protéines de l’HTC permettent la normalisation des niveaux de NAD+ et de NADPH. L’augmentation des niveaux de NAD+ et de NADPH a déjà été associé à la tumorigénèse. A travers ces travaux, nous avons constaté que la surexpression des protéines qui forment le complexe HTC coopère avec l’oncogène Ras à la transformation de cellules primaires. Par ailleurs, les enzymes du complexe HTC sont fortement exprimées in vivo au niveau des cancers de la prostate d’origine murine ou humaine. De plus, inactivation d’une proteine du complexe HTC déclenche l’entrée en sénescence des cellules tumorales y compris en l’absence de p53. Nous avons ainsi caractérisé un nouveau complexe multi-enzymatique qui peut reprogrammer le métabolisme et empêcher la mise en place de la sénescence cellulaire. L’inhibition de la formation du complexe HTC pourrait permettre de cibler spécifiquement sa fonction de novo tout en limitant de bloquer l’activité physiologique normale des ces enzymes en dehors de ce complexe. Par l’ensemble de ces travaux, nous avons mis en évidence l’importance des défauts de biogénèse des ribosomes ainsi que des altérations métaboliques dans la mise en place et le maintien de la sénescence. D’une part, l’accumulation de RPS14 en dehors des ribosomes constitue un nouveau mécanisme de régulation du cycle cellulaire. De plus, l’accumulation de RPL29 dans le nucleole constitue un nouveau biomarker de la senescence. D’autre part, l’identification du complexe HTC a mise en évidence une nouvelle façon de contourner la sénescence et ainsi de contribuer à la transformation de cellules primaires. Ces observations renforcent l’importance de la sénescence cellulaire en tant que mécanisme de suppression tumorale. Ces découvertes créent de nouvelles opportunités thérapeutiques afin de réactiver la sénescence dans les cellules cancéreuses. / Cellular senescence is a barrier to tumor progression that is circumvented in cancer cells. Senescence is a stable cell cycle arrest and can be triggered by various oncogenic events, such as constant activation of the oncogene H-RAS. Other critical aspects of senescent cells include a specific degradation of proteins implicated in cell cycle regulation, ribosome biogenesis, mitochondrial homeostasis, and cellular metabolism. In this study, we wanted to identify the contributions of the specific protein degradation to mitochondrial homeostasis, cellular metabolism, and ribosome biogenesis and how the degradation of proteins implicated in those pathways affects the senescence response. In order to answer our question, we divided our research into two aspects. The first aspect was focused on ribosomes and the alterations in ribosome biogenesis in senescence. The second aspect was the contribution of degradation of proteins implicated in cellular metabolism and mitochondrial homeostasis. First, we identified that a desynchronization of ribosome biogenesis accompanies senescence, meaning that certain rRNA are less transcribed, whereas specific ribosomal proteins do not decrease their transcription leading to an imbalance in ribosomal protein and ribosomal RNA. This imbalance causes an accumulation of ribosomal free riboproteins. Those accumulated riboproteins acquire novel functions. We identified RPL29 as a ribosomal free riboprotein that accumulated in senescent cells and can be used as a novel biomarker to identify senescent cells in vitro and in vivo. Identification of novel senescent cell biomarkers is crucial as no specific marker of senescence is available. Furthermore, we identified RPS14 as a protein that can interact with the CDK4-cyclinD1 complex and decrease cell cycle progression. Of utmost importance is that cell cycle repression was even possible in cancer cells devoided of p53 highlighting novel strategies for p53 null cancer treatments. In the second part, we focused on alterations in cellular metabolism, particularly in light of NAD metabolism and mitochondria homeostasis. We could confirm that the degradation of proteins implicated in mitochondrial homeostasis can induce senescence via the accumulation of NADH and p53 stabilization. Furthermore, we confirmed that the decrease in redox homeostasis regulators, namely NAD+ and NADPH, can trigger senescence. In the same idea, we showed that the normalization of those redox potentials could bypass the senescence response. Most importantly, we identified a novel protein complex formed by malic enzyme, malate dehydrogenase,and pyruvate carboxylase. The concerted actions of those three metabolic enzymes can transfer the hydride ion from NADH towards NADPH. Thus, we coined this complex HTC for hydride transfer complex. These metabolic reactions in HTC allow for two things, the normalization of NAD+ levels and the normalization of NADPH levels. Intruguenlty, both NAD+ and NADPH level increase were previously linked to transformation, and indeed, we were able to show that expression of HTC in combination with oncogenic Ras is sufficient to transform primary cells. Moreover, HTC enzymes are highly expressed in vivo in mouse and human prostate cancer models, and their inactivation triggers senescence even in the absence of p53. We provide evidence for a new multi-enzymatic complex, with de novo functions that reprogram metabolism and prevent cellular senescence. Inhibition of formation of the HTC complex might allow targeting specifically the de novo function of this complex with fewer effects on normal enzyme function. All in all, we highlighted the contributions of ribosome biogenesis and metabolic alterations in inducing and maintaining the senescence response. Furthermore, RPS14 accumulation allows for a novel cell cycle regulation mechanism, and the accumulation of RPL29 in the nucleolus can be used as a novel biomarker for cellular senescence. Moreover, the expression of HTC demonstrated a novel way of avoiding senescence, thus promoting cellular transformation. Both pathways highlight the importance of cellular senescence as a tumor suppressors mechanism, and these discoveries allow for novel strategies for cancer drug development. / Krebs ist eine der häufigsten Todesursachen in der westlichen Welt. Aus diesem Grund ist es von hoher Bedeutung die molekularen Prozesse die eine Zelle entarten, also zum Krebs werden lassen besonders genau zu untersuchen. Im Allgemeinen haben Zellen Mechanismen, die das Entarten verhindern sollen, jedoch sind diese Mechanismen nicht immer fehlerfrei. Ein solcher Mechanismus ist die Zellseneszenz. Dieser Schutzmechanismus kann auf verschiedene Weise, wie zum Beispiel durch das Mutieren eines Onkogenes, aktiviert werden. Die Zellseneszenz ist dadurch charakterisiert, dass sie potentielle Krebszellen an ihrer Zellteilung hindert und es deswegen zu keiner Entstehung eines Karzinoms kommt. Wie bereits angedeutet sind die Mechanismen, welche die Entartung von Zellen stoppen sollen nicht fehlerfrei und die Inaktivität dieser Schutzmechanismen kann zur Entartung - auch maligne Transformation genannt - einer Zelle führen. In dieser Doktorarbeit haben wir aufgezeigt, welche molekularen Prozesse in der Zelle aktiviert bzw. verändert werden und dann dazu führen, dass der Schutzmechanismus der Zellseneszenz umgangen wird. Im Allgemeinen haben wir zwei Prozesse, die während der malignen Transformation verändert werden, untersucht. Dies ist auf der einen Seite die Veränderung von ribosomer Entwicklung und auf der anderen Seite sind es die Veränderungsprozesse im Zellstoffwechsel. Ribosome sind makromolekulare Komplexe in Zellen, die aus speziellen Proteinen und RNA aufgebaut sind und besonders wichtig für die Zelle sind, da sie die Produktion von Proteinen ermöglichen. Wir haben aufgezeigt, dass während der Aktivierung von Zellseneszenz die Produktion von Ribosomen ungleichmäßig in der Zelle heruntergefahren wird. Dies führt dazu, dass bestimmte Proteine, die wichtig für die Ribosomen sind sich im Zellkern bzw. im Kernkörperchen ansammeln. Hier seien besonders zwei Protein zu nenen, RPS14 and RPL29. Wir haben festgestellt, dass diese Ansammlung von RPL29 im Kernkörperchen als Biomarker für die Ermittlung von Zellseneszenz in vivo dienen kann. Außerdem haben wir dargestellt, dass die Ansammlung von dem Protein RPS14 dazu führt, dass der Zellzyklus gestoppt wird. Die Entdeckung von RPS14 als Regulator für den Zellzyklus ist insofern wichtig, da dieser Prozess unabhängig von p53, einem Protein welches in über 50 Prozent aller Krebsarten inaktiv ist, stattfinden kann. Bisher waren zwei Mechanismen zur Zellzyklus Regulierung bekannt. Die Beschreibung von RPS14 im Zellzyklus erlaubt uns einen weiteren Mechanismus hinzuzufügen. Die ist ein wichtiger Schritt zur Erforschung von neuen Inhibitoren der Zellteilung. Im zweiten Teil der Arbeit haben wir untersucht inwiefern der Zellstoffwechsel sich während der Zellseneszenz verändert. Wir haben herausgefunden, dass sich das Niveau von wichtigen Co- Faktoren, die den Redoxstatus der Zelle regulieren währender Zellseneszenz verändert. Insbesondere das Molekül NAD+ zeigte eine starke Verringerung im Niveau. Weiterhin wussten wir, dass das Niveau von NAD+ und auch das Niveau von NADPH, ein Molekül ähnlich dem NAD, in Krebszellen besonders hoch ist. Wir haben festgestellt, dass in der Zelle ein Proteinkomplex aus Stoffwechsel Proteinen entstehen kann, welcher die Level von NAD+ und NADPH durch die Stoffwechselaktion dieser Proteine wieder normalisiert. Dieser Komplex besteht aus drei Proteinen Malic Enzyme 1, Malate Dehydrogenase 1 und Pyruvate Carboxylase. Besonders hervorzuheben hierbei ist unsere Entdeckung, dass Pyruvate Carboxylase in Krebszellen nicht nur in den Mitochondrien vorhanden ist, sondern auch im Zellplasma. Die Aktivierung dieses Proteinkomplexes ermöglicht Zellen die normalerweise in die Zellseneszenz gehen würden, diesen Schutzmechanismus zu umgehen und dabei bösartig zu entarten. Diese Entdeckung ist besonders interessant, da der Zellstoffwechsel von Krebszellen seit langem untersucht wird, es jedoch bisher noch nicht bekannt war das dieser Proteinkomplex in der Lage ist die Zelle bösartig zu transformieren. Wir konnten nachweisen, dass die Proteinlevel von unserem Komplex in Prostatakrebs im Vergleich zu normalem Prostatagewebe erhöht sind. Darüber hinaus waren wir in der Lage zu zeigen, dass die Inaktivierung von einem der Proteine aus dem Komplex dazu führt, dass die Zelle ihren Zellzyklus verlangsamt und weniger aggressiv in einem Kanzerogenitätstest ist. Dies ist selbst dann möglich, wenn die Krebszelle über kein aktives p53 Protein mehr verfügt. Besonders hervorzuheben diese Entdeckung, weil das p53 Protein eines der wichtigsten Proteine ist, welches die Zelle vor einer bösartigen Transformation schützt. Zusammenfassend ist zu sagen, dass wir zwei neue Mechanismen aufgezeigt haben die Veränderung der Ribosomenproduktion und die Stoffwechselprozesse, die sich während der malignen Transformation von Zellen verändern. In der Zukunft wird unsere Forschung versuchen zu verstehen inwiefern diese neuen Erkenntnisse dazu genutzt werden können neue Moleküle zu entwickeln die speziell die beschriebenen Prozesse nutzen, um den Zellzyklus von Krebszellen zu verlangsamen.