Une question fondamentale de la biologie évolutive porte sur la compréhension des mécanismes sous-tendant les processus évolutifs et l’évolution des compromis entre les traits d’histoire de vie. Parmi ces mécanismes, les télomères suscitent un intérêt particulier. Les télomères sont localisés à l’extrémité des chromosomes eucaryotes et participent à la sénescence cellulaire et au vieillissement des individus. La longueur des télomères est susceptible de donner des indications sur le mode de vie et l’état physiologique des organismes. Le but de cette thèse a été de comprendre quels sont les facteurs déterminant la longueur des télomères et leur implication dans les compromis évolutifs, ceci en établissant : si la taille des télomères est-elle héritable? Le taux de perte des télomères est-il affecté par des facteurs environnementaux? Quel lien entre les télomères, la maintenance individuelle et la qualité des individus? Il résulte de ce travail que la longueur des télomères est partiellement déterminée par les facteurs génétiques, elle semble aussi influencée par les facteurs environnementaux. En effet, le coût de la reproduction, ainsi que la modification des trajectoires de croissance, ont des effets néfastes sur la longueur des télomères. L’effet de la manipulation expérimentale de l’activité télomérase indique un lien entre les télomères et la maintenance individuelle, suggérant que les télomères sont susceptibles de donner des indications sur la qualité des individus. Ce travail de thèse montre que la dynamique des télomères est un mécanisme sous-jacent des compromis évolutifs, et présente un intérêt considérable pour la compréhension des processus évolutifs. / Evolutionary pathways through which life histories may have evolved are numerous. Consequently identifying the underlying mechanisms of those processes is crucial for our overall comprehension of the origin of life diversity. Thus, there is clearly a great potential in the study of repetitive DNA sequences that cap eukaryotic chromosomes, the telomeres. Telomeres are structures involved in cell senescence and determine the rate of ageing. They are thought to reflect more than just the effects ofage and to play an important role in linking life conditions and senescence. Indeed, telomeres could act as markers of life style and of past-historical levels of stress and inform on individuals’ current physiological quality. This thesis aims to determine whether telomeres could act as a mechanism underlying life history trade-offs by establishing the pattern of heritability of telomere length; characterising telomere length’s determinants; testing the nature of the relationship between telomerelength and individual maintenance, and ultimately with individual quality. The present work shows that telomere dynamics is determined by genetic factors, but is probably predominantly affected by lifestyle factors. As such, environmental conditions experienced during the growth period, as well as during adulthood (i.e. level of reproductive effort) have a strong impact on individuals’ telomere length. Experimental manipulation of telomerase activity showed that telomere length could be linked to individual maintenance and thus might be indicative of individual quality. Altogether, these results highlight that telomere dynamics might provide a functional link between life history traits.

The blood-brain barrier (BBB) is a dynamic interface, mainly consisting of highly specialized brain microvascular endothelial cells (BMECs) that segregate the central nervous system (CNS) from the peripheral circulation. Impairment of the BBB, due to disruption of tight junction (TJ) proteins and inflammatory responses, may initiate and/or contribute to the progress of CNS disorders, including stroke. Stroke is the second leading cause of death worldwide. It has been shown that aging and environmental pollutants can induce brain endothelium dysfunction, and are considered as risk factors for stroke. Deficiency of telomerase is highly linked with aging-associated vascular diseases. Evidence indicates that patients with shorter telomere length are at higher risk of heart disease or stroke. Results in this dissertation address the influence of telomerase reverse transcriptase (TERT), a key component of telomerase, on the BBB integrity in the context of ischemic stroke induced brain injury. Our results indicate that aging-related BBB alterations aggregate the stroke outcomes by inducing oxidative stress and stimulating proinflammatory responses on the brain microvessels. The ability of the BBB to protect the brain from harmful compounds indicates that the BBB may be targeted by chemical toxicants in the peripheral circulation. Polychlorinated biphenyls (PCBs) are persistent organic pollutants that frequently bind to nanoparticles (NPs) in the environment. Our results demonstrate that binding PCB153, one of the most abundant PCB congeners in the environment, to silica nanoparticles (PCB153-NPs) potentiates cerebrovascular toxicity and stroke outcomes via stimulation of inflammatory responses and disruption of BBB integrity. These events are mediated by activation of toll-like receptor 4 (TLR4), which subsequently recruits tumor necrosis factor-associated factor 6 (TRAF6) and initiates the production of multiple inflammatory mediators. Research presented in this dissertation demonstrates that aging and environmental pollutants play crucial roles in modifying the function of the BBB through alterations of inflammatory responses and TJ protein expression, which further contribute to the progression of stroke-induced cerebral ischemic injury.

TRF1 est une protéine télomérique essentielle pour la stabilité et la régulation de la longueur des télomères. Son expression est altérée dans de nombreux cancers humains, et son inhibition, dans un contexte p53 déficient, favorise le développement de tumeurs chez la souris. Nous montrons ici que l'inhibition de TRF1 dans les fibroblastes primaires humains conduit à une accumulation télomérique de γ-H2AX et à une activation de la voie de réponse aux dommages de l'ADN dépendante des kinases ATR/Chk1, menant rapidement les cellules vers la sénescence. En revanche, lorsque les voies p53 et pRb sont défaillantes, les cellules échappent à la sénescence. L'érosion accrue des télomères engendre alors une fragilité télomérique et une instabilité chromosomique, caractérisées par la présence de fusions entres chromatides soeurs et de signaux multi-télomériques (MTS). Un niveau élevé de MTS, associés à la présence de télomères courts, est également retrouvé après la surexpression de TRF1. Cette fragilité télomérique conduit à une extension de la capacité proliférative des cellules, due à une stabilisation de la longueur des télomères par réactivation de la télomérase. Nous proposons que la fragilité des télomères, induit par l'altération de la charge télomérique de TRF1, conduit à une instabilité chromosomique qui facilite la réactivation de la télomérase et à des anomalies chromosomiques comparables à celles retrouvées dans les tumeurs. La dérégulation de l'expression de TRF1 joueraient un rôle dans la progression tumorale des cellules p53 et pRb déficientes. / TRF1 is a telomere-binding protein which is essential for both telomere stability and telomere length regulation. TRF1 depletion in the context of p53 deficiency promotes tumor development in the mouse, and TRF1 expression is altered in some human cancers. We report here that inhibition of TRF1 in human primary fibroblast results in rapid induction of senescence, which is concomitant with telomeric accumulation of γ-H2AX and phosphorylation of the ATR downstream checkpoint kinase Chk1. Abrogation of p53 and pRb pathways bypasses senescence but leads to accelerated telomere shortening and early onset of chromosomal instability, including sister chromatid fusions and the occurrence of multi-telomeric signals (MTS) related to telomere fragility. MTS are also elevated in TRF1-overexpressing cells and are coincident with the presence of short telomeres. Elevated telomere fragility was associated with greater immortalization potential and resultant cells maintained their telomeres via telomerase reactivation. We propose that changes in TRF1 occupancy at telomeres lead to telomere-fragility driven chromosome instability, which facilitates the reactivation of telomerase and engenders cancer-relevant chromosomal aberrations. These events would occur at early stages of the tumor progression process in the context of an impaired p53 and pRb response.

The primary aim of this study was to determine the effectiveness of array-based technology for detecting and quantifying the presence of mosaicism. This aim was achieved by studying individuals having mosaicism for Down syndrome. SNP arrays were performed on 13 samples from individuals with mosaicism for trisomy 21, 13 samples from individuals with normal chromosome 21complements (negative controls) and 5 samples from individuals with full or partial trisomy 21 (positive controls). In addition, BAC arrays were processed on 6 samples from individuals with mosaicism for trisomy 21, 3 negative controls and 1 positive control. These studies have shown that array-based technology is effective for detecting mosaicism that is present in 20% or more cells with the results being consistent for both platforms. We also demonstrated the strength of array-based technology to identify previously unrecognized chromosomal mosaicism. A second aim of this study was to gain insight regarding the effect that trisomy 21 has on telomere attrition and the frequency of chromosomal instability. This study provides the first reported measure of both chromosome-specific telomere lengths and the frequency of acquired chromosome abnormalities in trisomic cells and isogenic euploid cells obtained from the same individuals. A chromosome-specific telomere length assay was performed on lymphocytes obtained from 24 young individuals with mosaicism for Down syndrome. While differences in overall telomere signal intensities were observed between the euploid and trisomic cells within a person, strikingly similar profiles for chromosome-specific telomere intensities were observed between the cell types within a person. Analyses were also completed on lymphoblast samples obtained from 8 older individuals with mosaicism for Down syndrome, including 5 individuals without dementia and 3 individuals with dementia. In the older study subjects, a significant inverse correlation was observed between telomere length and the frequency of micronuclei, suggesting that telomeric shortening is leading to an increased frequency of chromosomal instability, possibly through dicentric chromosome formation. However, further studies of more individuals, especially additional analyses of older individuals, are needed. These future studies may help to identify genomic regions of interest and serve to inform investigators of potential candidate genes in the etiology of dementia.

Différents rôles de l'hélicase Pif1 ont été décrit dont le plus documenté est de décrocher la télomérase des télomères en déroulant les hybrides ARN/ADN formés entre l'ARN de la télomérase et l'ADN télomérique. Plus récemment, une nouvelle voie de signalisation des dommages à l'ADN a été mise en évidence, qui inhibe l'action de la télomérase au niveau d'une cassure de l'ADN via la phosphorylation de l'hélicase Pif1. Cette phosphorylation, dépendante de la kinase ATR (Mec1), inhibe la réparation aberrante de la cassure d'ADN par la télomérase. Nous étudions au sein de l’équipe la protéine RPA (Replication Protein A), affine de l'ADN simple-brin, qui recrute à la fois la protéine de recombinaison homologue Rad52 et la protéine Mec1 impliquée dans la cascade de signalisation des dommages de l'ADN. Lors de l'étude de différentes fonctions de l'hélicase Pif1, j'ai mis en évidence une interaction robuste entre Pif1 et RPA. J'ai identifié un allèle de RFA1, rfa1-D228Y, affectant l'interaction Pif1/RPA et montré, grâce à cet allèle, que cette interaction est impliquée dans le recrutement de Pif1 au niveau d'une cassure double-brins (CDB) induite de l'ADN. Enfin, il a été récemment mis en évidence un nouveau rôle de Pif1 dans la stabilité des G-Quadruplexes durant la réplication du brin avancé. En effet, les cellules pif1 présentent un taux d'instabilité du minisatellite CEB1 inséré sur le brin avancé d'environ 56%, correspondant à des réarrangements de l'ADN de type contractions ou expansions. Lors de l'étude de l'interaction Pif1/RPA, j'ai montré que la mutation rfa1-D228Y entraîne une instabilité du minisatellite CEB1 présent sur le brin avancé, similaire à celle observée avec la délétion pif1∆. Nous suggérons un modèle selon lequel RPA recruterait Pif1 au cours de différents processus cellulaires tels que la réponse des dommages à l'ADN ou la réplication des structures particulières de l'ADN telles que les G-Quadruplexes.En parallèle de cette étude, j’ai étudié le rôle de l'histone méthyltransférase Set1 spécifique de la lysine 4 de l'histone H3 dans la régulation de la taille des télomères. J’ai mis en évidence que le raccourcissement des télomères observé dans un mutant set1 est lié à l'absence de di- et tri-méthylation de H3K4 alors que la perte de monométhylation n'a aucun effet. Cependant, le défaut de la taille des télomères dans les cellules set1∆ n'est pas uniquement lié au défaut de méthylation de H3K4 mais semble impliquer une autre activité de Set1 qu’il reste à déterminer. Etonnamment, nous avons observé que la délétion de SET1 aggrave le raccourcissement des télomères des mutants dont les gènes sont impliqués dans la régulation positive de la taille des télomères et inversement, aggrave le rallongement des télomères de mutants dont les gènes sont impliqués dans la régulation négative des télomères. Nous postulons que l’inactivation de Set1 pourrait à la fois inhiber l’activation précoce des origines de réplication des régions subtélomériques et conduire à un sur-raccourcissement de la taille des télomères, à la fois affecter la synthèse du brin complémentaire dans un contexte où celle-ci est affectée (mutant rif1) et conduire à un sur-allongement des télomères. Une seconde hypothèse propose que Set1 régulerait la transcription deTERRA dans des cellules ayant les télomères déprotégés (mutant rif) entraînant le sur-allongement des télomères. / Different roles of Pif1 helicase have been described, the best documented being to remove telomerase from telomeres by unwinding the RNA/DNA hybrid between telomerase RNA and telomeric DNA. Recently, it was shown that the DNA damage signaling down-regulates telomerase action at a DNA break via Pif1 phosphorylation. Pif1 phosphorylation is dependent of the checkpoint kinase ATR (Mec1) and prevents the aberrant healing of broken DNA ends by telomerase. In our laboratory, we study RPA (Replication Protein A), a single-strand DNA binding protein which recruits the proteins involved in the DNA damage response and checkpoint regulation, such as the homologous recombination protein Rad52 and Mec1 involved in the DNA damage response. I have identified an allele of RFA1, rfa1-D228Y, that affects the Pif1/RPA interaction and showed using this allele that this interaction is implicated in the Pif1 recruitment at an induced double-strand break. Recently, a new role of Pif1 in the stability of G-quadruplex DNA during the leading strand replication has been described. pif1 cells show an instability about 56% of the human minisatellite CEB1 inserted on the leading strand. During my study of the Pif1/RPA interaction, I showed that the rfa1-D228Y mutant induced a similar instability of CEB1 minisatellite on the leading strand. We suggested that RPA would recruit Pif1 for many cellular processes such as DNA damage response or replication of secondary DNA structures such as G-Quadruplexes.In parallel, I have studied the role of the Set1 Histone methyltransferase which catalyse the methylation of the lysine 4 of histone H3, in the regulation of telomere length. I showed that the telomere shortening observed in set1 mutant is due to the loss of di- and tri-methylation of H3K4 while the loss of monomethylation has no effect. However, the short telomeres in set1∆ cells is not only due to the methylation defect shedding light on a new Set1 activity that remains to be fully characterized.. The SET1 deletion aggravates the telomere shortening of mutants which genes are involved in positive regulation of telomere length and conversely, aggravates the lengthening of mutants which genes are involved in negative regulation of telomere length. We postulated that inactivation of Set1 could affect at once activation of early-replication origins and leads to a telomere shortening, and affect synthesis of complementary strand in a context where this one is affected (mutant rif1) and leads to a telomere lengthening. A second hypothesis propose that Set1 would regulate TERRA transcription in cells with deprotected-telomere (rif mutant) leading to the lengthening of telomeres.

A instabilidade genômica tem sido implicada como um dos principais fatores relacionados ao processo de envelhecimento. Esta é consequência do acumulo de danos no DNA em células somáticas continuamente expostas a fatores endógenos e exógenos. Um grupo de proteínas que desempenha diversos papéis na manutenção e estabilidade do genoma é formado pelas RecQ helicases, atuando em vários processos do metabolismo celular, tais como replicação do DNA, recombinação, reparo do DNA e manutenção dos telômeros. Algumas evidencias relacionam a expressão aberrante destas proteínas ao envelhecimento precoce. Com o objetivo de determinar os perfis de expressão transcricional de genes da família RecQ helicase e alguns genes envolvidos na via BER (Base excision repair), como PARP1, POL e APEX1 em células mononucleares do sangue periférico (PBMCs, do inglês Peripheral Blood Mononuclear Cells), comparamos grupos de indivíduos jovens (n = 20), idosos (n = 17) e centenários (n = 27). Além disso, foi também foi avaliado o comprimento telomérico em amostras de DNA desses indivíduos, buscando uma comparação entre os mesmos. Foi observada uma diminuição no nível de expressão transcricional do gene BLM nos grupos idoso e centenário quando comparados ao grupo jovem (p<0,05). Também foi observado uma diminuição na expressão do gene RECQL5 no grupo idoso comparado ao grupo jovem. Para os genes da via BER, foi observada uma repressão na expressão transcricional de PARP1 no grupo idoso em relação ao grupo jovem (p<0,05). Em relação ao comprimento telomérico, nossos resultados demonstraram associação entre a diminuição do comprimento telomérico e a idade. Obtivemos diferença significativa na comparação do comprimento telomérico de idosos e centenários comparados ao grupo jovem. Porém, não foi observada diferença entre os grupos idosos e centenários. Assim, nossos resultados mostram uma associação do processo de envelhecimento com a modulação de alguns genes da família RecQ helicase e participantes da via BER, e com o encurtamento telomérico. Os resultados gerados nesse trabalho são inéditos, sendo que relevantes para melhor compreensão do processo de envelhecimento. / Genomic instability plays a major role in the aging process due to the accumulation of DNA damage in somatic cells continuously exposed to endogenous and exogenous factors. A group of proteins essential in maintaining genome stability is composed by RecQ helicase, acting in several cell metabolism processes such as DNA replication, recombination, DNA repair and telomere maintenance. Some evidence related the aberrant expression of these proteins to premature aging. In order to determine the transcriptional expression profile of RecQ helicase gene family and some genes involved in the BER (Base excision repair) pathway, such as PARP1, POL and APEX1 in peripheral blood mononuclear cells (PBMCs), we compared groups of young (n = 20), elderly (n = 17) and centenarians (n = 27). Furthermore, it was also evaluated telomere length in DNA samples from these individuals. It was observed a decrease in the transcriptional expression of BLM gene in elderly and centenarians compared to the young group (p <0.05). It was also observed a decrease in expression of RECQL5 gene in the elderly compared to the younger group. For the BER genes, it was observed a transcriptional repression of PARP1 in the elderly group compared to the young group (p <0.05). Regarding the telomere length, our results demonstrated an association between reduction of telomere length and age. We obtained significant difference in comparing the telomere length of the elderly and centenarians compared to the younger group. However, no difference was observed between the elderly and centenarians groups. Thus, our results show an association of aging process with the modulation of certain genes from RecQ helicase family and participants of the BER pathway and the telomere shortening. The results generated in this study are promising, and relevant to better understanding the aging process.

Telômeros são estruturas localizadas nas extremidades dos cromossomos associadas a um conjunto de proteínas, o complexo shelterin, as quais são responsáveis pela proteção e preservação do material genético. O complexo shelterin é formado por seis proteínas denominadas TRF1, TRF2, RAP1, TIN2, TPP1 e POT1. O comprimento dos telômeros (CT) diminui progressivamente a cada divisão celular e evidências recentes sugerem que o estilo de vida pode acarretar em um encurtamento dos telômeros. Nos indivíduos com obesidade, o excesso de tecido adiposo exerce um papel fundamental ao induzir um estado inflamatório crônico e sistêmico, capaz de gerar o encurtamento do CT. Neste contexto, a cirurgia bariátrica é uma das modalidades de tratamento mais eficaz na melhora do controle metabólico da obesidade. Assim, o presente estudo teve como objetivo avaliar o comprimento dos telômeros e a expressão dos genes POT1, TRF1 e TRF2 em mulheres com obesidade antes e após seis meses da cirurgia bariátrica e em mulheres eutróficas. A amostra foi composta por 48 indivíduos do sexo feminino com obesidade submetidas à derivação gástrica em Y de Roux (DGYR) e 16 mulheres eutróficas. Tratou-se de um estudo longitudinal prospectivo no qual foram coletadas medidas antropométricas de peso e altura para cálculo do índice de massa corporal (IMC), circunferência abdominal (CA), composição corporal [massa livre de gordura (MLG) e massa gorda (MG)], ingestão alimentar e coleta de sangue para avaliação bioquímica, análise do CT (DNA) e expressão gênica (RNA). As mulheres com obesidade foram avaliadas antes e após seis meses do procedimento cirúrgico e as eutróficas em um único momento. Como principal resultado, observou-se, após seis meses do procedimento cirúrgico, redução do peso, IMC, CA, MLG, MG, assim como dos parâmetros bioquímicos. Ainda, verificou-se um menor CT entre as pacientes com obesidade quando comparada as mulheres eutróficas e um aumento no CT após a cirurgia quando comparado ao período pré-operatório, entretanto, permaneceu significante menor em relação ao grupo controle. Adicionalmente, observou-se que as modificações das concentrações de triglicérides influenciaram o comprimento dos telômeros, mesmo quando ajustado por idade. Com relação à expressão gênica, observou-se maior expressão dos genes POT1, TRF1 e TRF2 em mulheres eutróficas quando comparadas as pacientes com obesidade antes da DGYR; e aumento da expressão do gene TRF1 após o procedimento cirúrgico. Conclui-se que o CT de mulheres com obesidade é significante menor em relação às mulheres eutróficas. A intervenção cirúrgica mostrou ser eficaz na melhora da composição corporal, dos indicadores bioquímicos e capaz de aumentar o comprimento dos telômeros. Nossos resultados também demonstraram expressão aumentada de POT1, TRF1 e TRF2 em mulheres eutróficas e aumento na expressão de TRF1 após a cirurgia / Telomeres are structures located at the ends of chromosomes associated with proteins, the shelterin complex, which are responsible for the protection and preservation of the genetic material. The shelterin complex is formed by six proteins: TRF1, TRF2, RAP1, TIN2, TPP1 and POT1. The telomere length (TL) progressively decreases with each cell division and recent evidence suggests that lifestyle can lead to telomere shortening. In individuals with obesity, excess adipose tissue plays a key role in inducing a chronic and systemic inflammatory state, which can cause TL shortening. In this context, bariatric surgery is one of the most effective treatment modalities in improving the metabolic control of obesity. Thus, the present study aimed to evaluate the telomere length and expression of the POT1, TRF1 and TRF2 genes in obese women before and after six months of bariatric surgery and in eutrophic women. The sample consisted of 48 obese female subjects submitted to Roux-en-Y gastric bypass (RYGB) and 16 eutrophic women. This was a prospective longitudinal study in which anthropometric measures of body weight and height (BMI), abdominal circumference (AC), body composition [fat free mass (FFM) and fat mass (FM) were collected], food intake and blood collection for biochemical evaluation, TL analysis (DNA) and gene expression (RNA). Women with obesity were evaluated before and after six months of the surgical procedure and the eutrophic ones in a single moment. As a main result, was observed reduction of the weight, BMI, AC, FFM, FM, as well as the biochemical parameters after six months of the surgical procedure. Also, there was a lower TL among obese patients when compared to eutrophic women and a higher TL after surgery when compared to the preoperative period. However, even with a sixmonth stretch of the RYGB, patients with obesity remained with the TL lower than the control group. In addition, changes in triglyceride concentrations influenced telomere length, even when adjusted for age. Regarding the gene expression evaluated, the expression of POT1, TRF1 and TRF2 genes was higher in eutrophic women when compared to patients with obesity before RYGB; and increased expression of the TRF1 gene after the surgical procedure. It is concluded that the TL of obese women is less significant in relation to eutrophic women. The surgical intervention showed to be effective in the improvement of the body composition, the biochemical indicators and able to increase the telomere length. Our results also demonstrated increased expression of POT1, TRF1 and TRF2 in eutrophic women and increased expression of TRF1 after surgery

Telômeros são estruturas localizadas nas extremidades dos cromossomos associadas a um conjunto de proteínas, o complexo shelterin, as quais são responsáveis pela proteção e preservação do material genético. O complexo shelterin é formado por seis proteínas denominadas TRF1, TRF2, RAP1, TIN2, TPP1 e POT1. O comprimento dos telômeros (CT) diminui progressivamente a cada divisão celular e evidências recentes sugerem que o estilo de vida pode acarretar em um encurtamento dos telômeros. Nos indivíduos com obesidade, o excesso de tecido adiposo exerce um papel fundamental ao induzir um estado inflamatório crônico e sistêmico, capaz de gerar o encurtamento do CT. Neste contexto, a cirurgia bariátrica é uma das modalidades de tratamento mais eficaz na melhora do controle metabólico da obesidade. Assim, o presente estudo teve como objetivo avaliar o comprimento dos telômeros e a expressão dos genes POT1, TRF1 e TRF2 em mulheres com obesidade antes e após seis meses da cirurgia bariátrica e em mulheres eutróficas. A amostra foi composta por 48 indivíduos do sexo feminino com obesidade submetidas à derivação gástrica em Y de Roux (DGYR) e 16 mulheres eutróficas. Tratou-se de um estudo longitudinal prospectivo no qual foram coletadas medidas antropométricas de peso e altura para cálculo do índice de massa corporal (IMC), circunferência abdominal (CA), composição corporal [massa livre de gordura (MLG) e massa gorda (MG)], ingestão alimentar e coleta de sangue para avaliação bioquímica, análise do CT (DNA) e expressão gênica (RNA). As mulheres com obesidade foram avaliadas antes e após seis meses do procedimento cirúrgico e as eutróficas em um único momento. Como principal resultado, observou-se, após seis meses do procedimento cirúrgico, redução do peso, IMC, CA, MLG, MG, assim como dos parâmetros bioquímicos. Ainda, verificou-se um menor CT entre as pacientes com obesidade quando comparada as mulheres eutróficas e um aumento no CT após a cirurgia quando comparado ao período pré-operatório, entretanto, permaneceu significante menor em relação ao grupo controle. Adicionalmente, observou-se que as modificações das concentrações de triglicérides influenciaram o comprimento dos telômeros, mesmo quando ajustado por idade. Com relação à expressão gênica, observou-se maior expressão dos genes POT1, TRF1 e TRF2 em mulheres eutróficas quando comparadas as pacientes com obesidade antes da DGYR; e aumento da expressão do gene TRF1 após o procedimento cirúrgico. Conclui-se que o CT de mulheres com obesidade é significante menor em relação às mulheres eutróficas. A intervenção cirúrgica mostrou ser eficaz na melhora da composição corporal, dos indicadores bioquímicos e capaz de aumentar o comprimento dos telômeros. Nossos resultados também demonstraram expressão aumentada de POT1, TRF1 e TRF2 em mulheres eutróficas e aumento na expressão de TRF1 após a cirurgia / Telomeres are structures located at the ends of chromosomes associated with proteins, the shelterin complex, which are responsible for the protection and preservation of the genetic material. The shelterin complex is formed by six proteins: TRF1, TRF2, RAP1, TIN2, TPP1 and POT1. The telomere length (TL) progressively decreases with each cell division and recent evidence suggests that lifestyle can lead to telomere shortening. In individuals with obesity, excess adipose tissue plays a key role in inducing a chronic and systemic inflammatory state, which can cause TL shortening. In this context, bariatric surgery is one of the most effective treatment modalities in improving the metabolic control of obesity. Thus, the present study aimed to evaluate the telomere length and expression of the POT1, TRF1 and TRF2 genes in obese women before and after six months of bariatric surgery and in eutrophic women. The sample consisted of 48 obese female subjects submitted to Roux-en-Y gastric bypass (RYGB) and 16 eutrophic women. This was a prospective longitudinal study in which anthropometric measures of body weight and height (BMI), abdominal circumference (AC), body composition [fat free mass (FFM) and fat mass (FM) were collected], food intake and blood collection for biochemical evaluation, TL analysis (DNA) and gene expression (RNA). Women with obesity were evaluated before and after six months of the surgical procedure and the eutrophic ones in a single moment. As a main result, was observed reduction of the weight, BMI, AC, FFM, FM, as well as the biochemical parameters after six months of the surgical procedure. Also, there was a lower TL among obese patients when compared to eutrophic women and a higher TL after surgery when compared to the preoperative period. However, even with a sixmonth stretch of the RYGB, patients with obesity remained with the TL lower than the control group. In addition, changes in triglyceride concentrations influenced telomere length, even when adjusted for age. Regarding the gene expression evaluated, the expression of POT1, TRF1 and TRF2 genes was higher in eutrophic women when compared to patients with obesity before RYGB; and increased expression of the TRF1 gene after the surgical procedure. It is concluded that the TL of obese women is less significant in relation to eutrophic women. The surgical intervention showed to be effective in the improvement of the body composition, the biochemical indicators and able to increase the telomere length. Our results also demonstrated increased expression of POT1, TRF1 and TRF2 in eutrophic women and increased expression of TRF1 after surgery

A injúria renal aguda representa um estado de senescência precoce induzida por estresse, e as células-tronco mesenquimais podem ser uma alternativa para seu tratamento. Células-tronco jovens reduzem o fenótipo de envelhecimento em rins quando comparadas a células idosas. O objetivo deste estudo foi avaliar se o tratamento com jovens células-tronco mesenquimais derivadas de cordão umbilical humano podem interferir na senescência renal induzida por lesão de isquemia-reperfusão em ratos. Ratos machos foram submetidos ao modelo de isquemia de artérias renais bilateralmente por 45 minutos, com reperfusão após, e alguns animais receberam 1 X 106 células por via intraperitoneal após 6 horas da indução da lesão. Os animais foram eutanasiados no segundo ou no sétimo dia pós-isquêmico. No segundo dia após a lesão de isquemia-reperfusão, o tratamento com as células melhorou a filtração glomerular e a função tubular, melhorou a expressão renal de aquaporina-2 e reduziu a infiltração de macrófagos nos rins. Proteínas relacionadas à senescência (-galactosidase, p21, p16 e fator de transformação do crescimento ) e microRNAs (mir-29a e miR-34a) estiveram com a expressão aumentada após a isquemia-reperfusão, e houve redução nesses parâmetros com o tratamento. A redução na expressão de Klotho e o estado pró-oxidativo gerados pela isquemia-reperfusão também foram revertidos pelo tratamento. A senescência induzida pela injúria renal aguda é um processo independente de telômeros. Ao sétimo dia pós-lesão, os ratos isquêmicos mantinham defeito de concentração urinária, que foi revertido nos animais tratados. Além disso, o tratamento reduziu o índice de necrose tubular aguda em tecido renal e reduziu o infiltrado macrofágico túbulo-intersticial. O marcador pró-senescência p16 foi completamente restabelecido nos animais tratados. Nossos dados demonstram que o tratamento com jovens células-tronco mesenquimais derivadas de cordão umbilical humano atenua a resposta inflamatória e de estresse oxidativo que ocorre na injúria renal aguda, e reduz a expressão de proteínas e microRNAs relacionados à senescência. Nossos achados expandem as perspecivas para o tratamento da injúria renal aguda / Acute kidney injury represents a status of premature stress-induced senescence, and mesenchymal stem cells are an alternative for treatment. Young stem cells reduce aging phenotype in kidneys when compared to old cells. The objective of this study was to evaluate if treatment with young human umbilical cord mesenchymal stem cells could interfere in kidney senescence induced by renal ischemia-reperfusion in rats. Male rats were induced to ischemia-reperfusion injury by 45-minutes clamping of both renal arteries; some rats received 1X106 cells intraperitonally six hours later. Rats were euthanatized on post-renal ischemia reperfusion days two and seven. At day 2 after ischemia-reperfusion injury, treatment with cells improved glomerular filtration, tubular function, improved renal expression of aquaporin 2 and decreased macrophage kidney infiltration. Senescence-related proteins (?-galactosidase, p21, p16 and transforming growth factor ?) and microRNAs (miR-29a and miRNA-34a) were overexpressed after ischemia-reperfusion, and reversed by the treatment. The Klotho reduced expression and the pro-oxidative status induced by ischemia-reperfusion were reversed by the treatment. Senescence induced acute kidney injury is a telomere-independent process. At day 7, ischemic rats maintained urinary concentrating defect, which is reversed in treated animals. Moreover, treatment decreased the index of acute tubular necrosis in kidney tissue and decreased macrophage kidney infiltration. Senescence marker p16 was completely restored in treated animals. Our data demonstrate that young human umbilical mesenchymal stem cells treatment attenuates the inflammatory and oxidative stress response occurring in acute kidney injury, and reduces the protein and microRNA expression related to senescence. Our findings broaden the perspectives for the treatment of AKI

A instabilidade genômica tem sido implicada como um dos principais fatores relacionados ao processo de envelhecimento. Esta é consequência do acumulo de danos no DNA em células somáticas continuamente expostas a fatores endógenos e exógenos. Um grupo de proteínas que desempenha diversos papéis na manutenção e estabilidade do genoma é formado pelas RecQ helicases, atuando em vários processos do metabolismo celular, tais como replicação do DNA, recombinação, reparo do DNA e manutenção dos telômeros. Algumas evidencias relacionam a expressão aberrante destas proteínas ao envelhecimento precoce. Com o objetivo de determinar os perfis de expressão transcricional de genes da família RecQ helicase e alguns genes envolvidos na via BER (Base excision repair), como PARP1, POL e APEX1 em células mononucleares do sangue periférico (PBMCs, do inglês Peripheral Blood Mononuclear Cells), comparamos grupos de indivíduos jovens (n = 20), idosos (n = 17) e centenários (n = 27). Além disso, foi também foi avaliado o comprimento telomérico em amostras de DNA desses indivíduos, buscando uma comparação entre os mesmos. Foi observada uma diminuição no nível de expressão transcricional do gene BLM nos grupos idoso e centenário quando comparados ao grupo jovem (p<0,05). Também foi observado uma diminuição na expressão do gene RECQL5 no grupo idoso comparado ao grupo jovem. Para os genes da via BER, foi observada uma repressão na expressão transcricional de PARP1 no grupo idoso em relação ao grupo jovem (p<0,05). Em relação ao comprimento telomérico, nossos resultados demonstraram associação entre a diminuição do comprimento telomérico e a idade. Obtivemos diferença significativa na comparação do comprimento telomérico de idosos e centenários comparados ao grupo jovem. Porém, não foi observada diferença entre os grupos idosos e centenários. Assim, nossos resultados mostram uma associação do processo de envelhecimento com a modulação de alguns genes da família RecQ helicase e participantes da via BER, e com o encurtamento telomérico. Os resultados gerados nesse trabalho são inéditos, sendo que relevantes para melhor compreensão do processo de envelhecimento. / Genomic instability plays a major role in the aging process due to the accumulation of DNA damage in somatic cells continuously exposed to endogenous and exogenous factors. A group of proteins essential in maintaining genome stability is composed by RecQ helicase, acting in several cell metabolism processes such as DNA replication, recombination, DNA repair and telomere maintenance. Some evidence related the aberrant expression of these proteins to premature aging. In order to determine the transcriptional expression profile of RecQ helicase gene family and some genes involved in the BER (Base excision repair) pathway, such as PARP1, POL and APEX1 in peripheral blood mononuclear cells (PBMCs), we compared groups of young (n = 20), elderly (n = 17) and centenarians (n = 27). Furthermore, it was also evaluated telomere length in DNA samples from these individuals. It was observed a decrease in the transcriptional expression of BLM gene in elderly and centenarians compared to the young group (p <0.05). It was also observed a decrease in expression of RECQL5 gene in the elderly compared to the younger group. For the BER genes, it was observed a transcriptional repression of PARP1 in the elderly group compared to the young group (p <0.05). Regarding the telomere length, our results demonstrated an association between reduction of telomere length and age. We obtained significant difference in comparing the telomere length of the elderly and centenarians compared to the younger group. However, no difference was observed between the elderly and centenarians groups. Thus, our results show an association of aging process with the modulation of certain genes from RecQ helicase family and participants of the BER pathway and the telomere shortening. The results generated in this study are promising, and relevant to better understanding the aging process.