Metabolic energy is most efficiently stored as triacylglycerol (TAG). This neutral lipid accumulates mainly within adipose tissues, but it can be stored and used in all types of cells. Within cells it is packed in organelles called lipid droplets (LDs). They consist of a core of neutral lipids like TAG and cholesterol esters, which is surrounded by a phospholipid monolayer that mainly consists of phosphatidylcholine (PC). Attached to or inserted into this monolayer are various proteins, mainly LD specific structural proteins or lipid metabolic enzymes. Though excess uptake of nutrition leads to lipid accumulation in all kinds of body tissues, which is accompanied by the augmentation of LDs and results in cellular dysfunction and the development of metabolic diseases, relatively little is known about the biogenesis and growth of LDs. This thesis focuses on diacylglycerol acyltransferase 2 (DGAT2), an enzyme of the TAG biosynthetic pathway, and on lyso-phosphatidylcholine acyltransferases 1 and 2 (LPCAT1 and LPCAT2), both enzymes of one of the PC biosynthetic pathways called Lands cycle. The data presented in this thesis show that these enzymes can localize to LDs and that they actively synthesize TAG and PC at the surface of LDs. While the LPCATs reside on LDs independent from the nutrition status of the cell, DGAT2 accumulates on LDs upon excess availability of oleic acid. DGAT2, LPCAT1 and LPCAT2 differ in their structure from other iso-enzymes that catalyze the same reactions. This thesis shows that they exhibit a monotopic conformation and that they contain a hydrophobic stretch that presumably forms a hairpin. This topology enables them to localize to both a phospholipid bilayer like the membrane of the endoplasmic reticulum and to a phospholipid monolayer like the surface of LDs. The different biophysical properties of the structures of iso-enzymes might be responsible for their subcellular localization and the formation of distinct TAG or PC pools that are destined for different purposes. This would explain, why the iso-enzymes are often not able to replace each other. Knock-down and overexpression experiments performed in this thesis show that the activity of LPCAT1, LPCAT2 and DGAT2 influence the packaging of lipids within LDs. Knock-down of LPCAT1 and LPCAT2 leads to an increase in LD size without concomitant increase in the amount of TAG. Combined with the finding that the profile of the PC species of the LD surface reflects the substrate preferences of LPCAT1 and LPCAT2, the results suggest that these enzymes are responsible for the formation of the LD surface. Therefore, the increase in LD size upon LPCAT1 and LPCAT2 knock-down results from an adjustment of the surface-to-volume ratio in response to reduced availability of surface lipids. The connection between LPCATs and LD size was corroborated in the model organism Drosophila melanogaster. Three different knockout fly strains of the Drosophila homologue of LPCAT1 and LPCAT2, CG32699, exhibit enlarged LDs in the fat body of the L3 larvae. Furthermore, the data presented suggest that the morphology of LDs is important for the secretion of stored lipids. The reduction of LPCAT1 in liver cells leads to a reduction in lipoprotein particle release. This was shown by measuring the amount of released apolipoproteinB with two different methods, by measuring the release of lipids and by quantification of the amount of released hepatitis C virus, which is known to rely on LD interaction for replication and on lipoprotein particles for cellular release. DGAT2 is recruited to LDs upon excess availability of oleic acid and its overexpression leads to the formation of many, but relatively small LDs. Here, it is shown that DGAT2 interacts with acyl-CoA synthetase ligase 1 (ACSL1), an enzyme that catalyzes the activation of free fatty acids with Coenzyme A. This interaction does not influence the stability of DGAT2 nor does it seem to affect lipid synthesis. Nevertheless, it shows an influence on lipid packaging in LDs. While overexpression of DGAT2 results in the appearance of smaller LDs, overexpression of ACSL1 leads to an increase in LD size. Coexpression of ACSL1 and DGAT2 reverses the phenotypes obtained by single overexpression and normalizes the mean LD diameter to values observed at normal conditions. In conclusion, this thesis shows that LDs are able to synthesize the components of their core and their surface, which underlines their independent function in metabolism. Additionally, the results show that LDs can grow by local synthesis and that the responsible enzymes exhibit a monotopic membrane topology, which might be crucial for LD localization. Furthermore, the obtained data suggest that the localization and the ratio between different enzyme activities influence the packaging of lipids and affects lipid secretion and therefore impact the whole body lipid metabolism.

No / The Flinders Sensitive Line (FSL) rat is a genetic animal model of depression. Following recent findings that the brain fatty acid composition of FSL is characterised by increased arachidonic acid (AA), we used electrospray tandem mass spectrometry and 1H-NMR to examine lipid species in different brain areas. Cholesterol and sphingolipids were increased in the hypothalamus of the FSL rats. Furthermore, arachidonic acid-containing phosphatidylcholine species (AA-PC) were elevated with PC16:0/20:4, PC18:1/20:4 and PC18:0/20:4 (p<0.003) increased in the hypothalamus and striatum. In contrast, there was a decrease in some docosahexaenoic acid (DHA)-containing species, specifically PC18:1/22:6 (p<0.003) in the striatum and PE18:1/22:6 (p<0.004) in the prefrontal cortex. Since no significant differences were observed in the erythrocyte fatty acid concentrations, dietary or environmental causes for these observations are unlikely. The increase in AA-PC species which in this animal model may be associated with altered neuropathy target esterase activity, an enzyme involved in membrane PC homeostasis, may contribute to the depressive phenotype of the FSL rats.

A astaxantina (AST) é um carotenóide derivado do &#946;-caroteno produzido por algas e cianobactérias, mas que também pode ser encontrada em animais marinhos. Em animais, é reportada como interceptadora de radicais de oxigênio mais eficiente que o &#946;-caroteno. O objetivo central dessa dissertação foi avaliar a capacidade antioxidante da AST em lipossomos enriquecidos com citocromo c (cit c) desafiados com 3-morfolinosidnonimina (SIN-1), um doador de óxido nítrico, em diferentes microambientes (pH e composição das vesículas). Diferenças na interação destas vesículas com o cit c periférico, com reflexos na atividade antioxidante da AST também foram avaliadas. O SIN-1 gera, por termólise, quantidades equimolares de radical superóxido e óxido nítrico, quando há oxigênio no meio. Vesículas unilamelares de fosfatidilcolina (PC), PC contendo 5% ou 10% de fosfatidilglicerol (PG), com ou sem AST, foram incubadas com SIN-1 e/ou cit c. Medidas do índice de lipoperoxidação pelo teste das substâncias reativas ao ácido tiobarbitúrico (TBARS) revelaram que SIN-1 não causa aumento de TBARS, enquanto o cit c foi capaz de aumentar significativamente este índice. Este fato pode ser explicado pela atividade peroxidásica do cit c. Apenas em vesículas de PCPG10%, ao realizar a incubação do cit c concomitantemente com SIN-1, o índice de TBARS foi maior ao observado em vesículas incubadas apenas com cit c. É conhecido que a interação entre cit c e membranas aniônicas pode alterar a conformação da proteína, aumentando sua atividade peroxidásica. A presença da AST fez com que os índices de lipoperoxidação chegassem a valores próximos aos do controle. A alteração no pH do meio revelou que a AST possui ação antioxidante mais pronunciada em pHs 7,4 e 8,0, em comparação com pHs levemente ácidos. A presença de PG evidenciou ainda mais esta tendência e em pH 6,2, a AST apresentou inclusive pequena atividade próoxidante. Estes resultados podem ser discutidos à luz de alterações da permeabilidade da membrana e da reatividade de espécies reativas induzidas por mudanças da fluidez e de pH. O efeito dos produtos gerados por SIN-1 sobre o cit c foi estudado em condições de normóxia e hipóxia. Resultados de EPR e de fluorescência demonstram que a presença do radical superóxido previne lesões oxidativas causada por peróxido orgânico (t-butOOH) tanto no cit c quanto nas membranas, pois é capaz de reduzir o ferro hemínico do cit c. Através de CD e espectrofotometria UV-Vis e EPR, foi observado que a incubação com SIN-1 promove alterações estruturais no cit c causando ruptura na sexta coordenação do ferro hemínico, levando à geração de uma espécie de cit c com rombicidade menor em comparação ao cit c nativo e que apresenta maior atividade peroxidásica. Este trabalho contribui com informações para entendimento do mecanismo antioxidante da AST em diferentes microambientes, além de demonstrar o efeito paradoxal do superóxido que é capaz de proteger o cit c, através da redução do ferro hemínico, mas também pode expor a proteína à oxidação promovida por peroxinitrito. / Astaxanthin (AST) is a &#946;-carotene derived carotenoid, produced by algae and cyanobacteria, but can also be found in marine animals. In phytoplankton it has the function to absorb light radiation for photosinthesys occurence. In animals AST acts as a scavenger of oxygen free radicals, even more efficiently than &#946;-carotene itself. The main objective of this work is to evaluate the antioxidant capacity of AST over cytochrome c (cyt c) incorporated in liposomes and challenged with 3-morpholinosidnonimine (SIN-1), a nitric oxide donor, under different experimental conditions, namely vesicles composition and pH. Distinct interactions between cyt c and vesicles affecting the AST antioxidant activity were also evaluated. SIN-1 spontaneously generates equal amount of nitric oxide and superoxide anion when oxygen is present. Unilamellar vesicles made from phosphatidylcholine (PC) or PC with 5% or 10% of phosphatidylglycerol (PG), with or without AST, were incubated with SIN-1 and/or cyt c. The extent of lipid peroxidation was evaluated by the classical method of thiobarbituric reactive substances (TBARS). Control experiments with SIN-1 alone showed no increase in TBARS content, whereas cyt c significantly increased TBARS. Concomitant addition of cyt c, SIN-1 to PCPG10% vesicles led to lipid peroxidation indices even higher than those found when cyt c was incubated with PCPG10% vesicles. A peroxidase activity of cyt c resulting from the interaction between this protein and anionic membranes can explain this result. In this system, the presence of AST inhibited formation of TBARS, whose levels were near the control values. Astaxanthin was found to exhibit a more effective antioxidant capacity under basic pH (7.4 and 8.0), in comparison with pH 6.2 and 6.8. In the presence of PG, this trend became more evident. Interestingly, at pH 6.2, AST showed a slight pro-oxidant activity. These results can be explained by differences in membrane permeability and reactivity of reactive species, caused by pH and membrane fluidity alterations. The effects of products of SIN-1 decomposition on cyt c structure and its peroxidase activity were investigated under hypoxia and normoxia. EPR and fluorescence experiments revealed that superoxide anion radical, due to its ability to reduce heme iron, prevents oxidative damage of cyt c and membrane lipids by peroxide-derived free radicals. By means of CD and UV-Visible spectroscopy, we have found that concomitant incubation of SIN-1 and cyt c promoted structural alterations in the protein which changes the irons sixth axial coordination, leading to generation of a less rhombic cyt c, which is reportedly a better peroxidase than native cyt c. This work contributes with information aiming to better understand the antioxidant mechanism of AST under different membrane microenvironments and unveil a paradoxal effect of superoxide ion, which can protect cyt c from oxidative lesions by transferring electron to ferricyt c, but can also expose cyt c to oxidation by peroxynitrite.

Der obligat intrazelluläre Parasit Toxoplasma gondii ist der Erreger der Toxoplasmose, und dient zugleich als wichtiger Modellorganismus für weitere Human- und Tierpathogene, wie z.B. Plasmodium oder Eimeria. Die Vermehrung von T. gondii erfordert eine effiziente Biosynthese von Phospholipiden für die Herstellung neuer Membranen, was durch die de novo Synthese durch den Parasiten, und/oder den Import von Lipiden aus der umgebenden Wirtszelle gewährleistet werden kann. Während der Parasit zahlreiche Möglichkeiten für Synthese oder Import von PtdEtn und PtdSer verwendet, scheint die Biosynthese des abundantesten Membranlipids PtdCho auschließlich über den CDP-Cholin Weg zu erfolgen. Dieser erstreckt sich in T. gondii über 3 zelluläre Kompartimente, mit einer cytosolischen Cholin-Kinase (TgCK), einer im Zellkern lokalisierenden Cholin-Cytidylyltransferase (TgCCT) und einer Cholin-Phosphotransferase (TgCPT) im ER. Anders als die substrat-spezifische Ethanolamin-Kinase (TgEK), kann TgCK neben Cholin außerdem Ethanolamin phosphorylieren. TgCK zeigt eine geringe Affinität zu Cholin (Km ~0.77 mM), während eine verkürzte TgCK (TgCKS), welcher eine als Signalpeptid vorhergesagte N-terminale Sequenz (20 Aminosäuren) fehlt, eine etwa 3-fach höhere Aktivität aufweist (Km ~0.26 mM). Während jedoch die Wildtyp-TgCK cytosolische Cluster in Toxoplasma bildet, zeigt die verkürzte TgCK eine gleichmäßigere cytosolische Lokalisierung. Wir schlussfolgern daraus, dass der hydrophobe N-Terminus nicht notwendig ist für eine funktionale TgCK, sondern eine strukturelle Funktion bei der Protein-Lokalisierung hat. Eine konitionelle Mutante, in welcher der TgCK Promoter gegen den Tetracyclin-regulierbaren Promoter pTetO7Sag4 ausgetauscht wurde (Deltatgcki), zeigt erstaunlicherweise normales Wachstum und PtdCho Biosynthese. Die TgCK Aktivität und die daraus resultierende PtdCho Synthese sind nur zu ~30% regulierbar. Unsere Ergebnisse deuten auf die Verwendung eines alternativen Startcodons bzw. Promoters hin, welcher zur Expression einer verkürzten (~53-kDa) aber vermutlich aktiven Cholin Kinase führt, wodurch der Verlust der TgCK (~70-kDa) kompensiert wird. Der konditionelle Knockout von TgCCT, dem regulatorischen Enzym des CDP-Cholin Wegs, hatte einen 50%igen Wachstumsdefekt zur Folge. Diese Studie zeigt eine erstaunliche Flexibilität des Parasiten bezüglich seiner Membranzusammensetzung, und bestätigt zugleich die Annahme, dass PtdCho nicht von der Wirtszelle importiert werden kann. Diese Anpassungsfähigkeit stellt einen möglichen Faktor dar, der es T. gondii erlaubt sich in einem breiten Spektrum von Wirten zu vermehren. / Toxoplasma gondii is an obligate intracellular apicomplexan parasite that causes life-threatening disease in neonates and in immunocompromised people. Successful replication of Toxoplasma requires substantial membrane biogenesis, which must be satisfied irrespective of the host-cell milieu. Like in other eukaryotes, the two most abundant phospholipids in the T. gondii membrane are phosphatidylcholine (PtdCho) and phosphatidylethanolamine (PtdEtn). Bioinformatics and precursor labeling analyses confirm their synthesis via the CDP-choline and CDP-ethanolamine pathway, respectively. This work shows that the 3-step CDP-choline pathway, involving the activities of TgCK, TgCCT and TgCPT, localizes to the cytosol, nucleus and ER membrane, respectively. The initial reaction is catalyzed by a dual-specificity choline kinase (TgCK, ~70-kDa), capable of phosphorylating choline as well as ethanolamine. The purified full-length TgCK displayed a low affinity for choline (Km ~0.77 mM). TgCK harbors a unique N-terminal hydrophobic peptide that is required for the formation of enzyme oligomers in the parasite cytosol but not for activity. The displacement of the TgCK promoter in a conditional mutant of T. gondii (deltatgcki) attenuated the enzyme expression by ~80%. Unexpectedly, the ?tgcki mutant was not impaired in intracellular growth, and exhibited a normal PtdCho biogenesis. To recompense for the loss of full-length TgCK, the mutant appears to make use of an alternative promoter and/or start codon, resulting in the expression of a shorter but active TgCK isoform identified by the anti-TgCK antiserum, which correlated with its persistent choline kinase activity. Accordingly, the ?tgcki showed an expected incorporation of choline into PtdCho, and susceptibility to dimethylethanolamine (a choline analog). Interestingly, the conditional mutant displayed a regular growth in off state despite a 25% decline in PtdCho content, which suggests a compositional flexibility in T. gondii membranes and insignificant salvage of host-derived PtdCho. The two-step conditional mutagenesis of TgCCT, which caused a reduced growth rate to about 50%, further substantiated this finding. The enzymatic activity of TgCCT and its role in PtdCho synthesis remain to be proven, however. Taken together, the results demonstrate that the CDP-route is likely essential in T. gondii. The competitive inhibition of choline kinase to block the parasite replication appears a potential therapeutic application.The work also reveals a remarkably adaptable membrane biogenesis in T. gondii, which may underly the evolution of Toxoplasma as a promiscuous pathogen.

Introdução. A criopreservação de oócitos é importante, tanto para a tentativa de preservação da fertilidade feminina, como nos tratamentos de reprodução assistida. Hipotetizamos que novas formulações de meios crioprotetores, contendo biomoléculas que participam da estrutura e funcionalidade celular, em particular da função mitocondrial e da dinâmica do sistema de membranas, poderiam melhorar a criotolerância e segurança da vitrificação. Objetivos. Este estudo teve como objetivo investigar os efeitos do meio padrão de vitrificação (T4) e T4 suplementado com L-carnitina (LC), LC-ácidos graxos (T4-AG) e LC-AGfosfatidilcolina (T4-PC) sobre a sobrevida e qualidade de oócitos criopreservados, mensurada por parâmetros do desenvolvimento in vitro de embriões, como número de núcleos totais (NT), de células na massa celular interna (MCI) e trofectoderma (TE) dos blastocistos oriundos de oócitos vitrificados nestes meios, assim como sobre os padrões de atividade mitocondrial oocitária. Materiais e métodos. Estudo experimental usando o camundongo da cepa C57BL/6 como modelo. Oócitos maturados in vivo, foram distribuídos em 5 grupos: controle a fresco (CT) e 4 grupos vitrificados: T4, T4-LC, T4-AG e T4-PC. Após a desvitrificação, foi analisada a sobrevida oocitária e os oócitos viáveis foram submetidos a fertilização in vitro ou utilizados para análise da atividade mitocondrial, por meio da análise de espécies reativas de oxigênio (EROs) intracelular por Intensidade de Fluorescência emitida pelo diacetato de 2,7- diclorodihidrofluoresceína, metabolismo oxidativo pela autofluorescência de dois fluoróforos endógenos [dinucleótideo de flavina adenina oxidado e o dinucleotideo reduzido de nicotinamida adenina (fosfato)] e potencial de membrana mitocondrial por Intensidade de Fluorescência (IF) emitida pelo JC1. Os oócitos dos 5 grupos submetidos a FIV foram cultivados por 96 horas, sendo comparados entre os grupos: taxa de fertilização e formação de blastocisto, assim como o número de NT, células MCI e TE e tamanho dos blastocistos. Resultados. A taxa de sobrevivência dos oócitos vitrificados em T4 foi superior a dos demais grupos T4-LC, T4-AG e T4-PC (respectivamente 100%, 97,07%, 96,75% e 97,95%). A taxa de fertilização do grupo CT (77,5%) foi superior a dos grupos T4, T4-LC e T4-PC, não diferindo do grupo T4-AG. Não foram evidenciadas diferenças estatisticamente significativas nas taxas de formação de blastocistos entre os grupos CT, T4, T4-LC, T4-AG e T4-PC (58,07%, 48,05%, 47,44%, 57,89% e 51,06%,respectivamente). Comparando-se o número NT e de células do TE dos blastocistos, observou-se que o os valores do grupo controle foram maiores do que o dos outros 4 grupos, que não apresentaram diferenças entre si. O número de células da MCI dos blastocistos do grupo controle foi superior ao dos grupos T4 e T4-LC e similar ao dos grupos T4-AG e T4- PC. Para o perfil de atividade mitocondrial, foram analisados 15 oócitos/grupo. Os níveis de EROs foram maiores no grupo CT comparado ao grupo T4 e menor quando comparado aos grupos T4-LC e T4-AG, mas sem diferença significativa em relação ao grupo T4-PC. Para Resumo analise do estado redox, o grupo CT teve maiores valores do que a dos grupos T4, T4-LC e T4- AG e o grupo T4-PC foi maior do que a dos outros quatro grupos. Para o potencial de membrana mitocondrial, o grupo CT teve maiores valores do que a do grupo T4-LC, menor do que a do grupo T4 e sem diferença estatisticamente significativa com a dos grupos T4-AG e T4-PC. Conclusão. O número de NT, células do TE e tamanho do blastocistos foram inferiores nos grupos vitrificados/desvitrificados em meio padrão e suplementados comparados ao controle. Porém, o número de células da MCI não foi diferente entre o grupo controle e os vitrificados T4- AG e T4-PC, sugerindo que a suplementação dos meios padrão com LC, AG e PC possa melhorar a competência do oócito e a subsequente qualidade embrionária, o que precisa ser melhor investigado antes da aplicação clínica dos novos meios. Apesar dos oócitos vitrificados no meio T4 terem apresentado taxa de sobrevivência estatisticamente superior a dos demais grupos, sugerimos que estas diferenças não apresentariam potencial relevância clínica. Os resultados de atividade mitocondrial revelam que há uma diferença importante entre oócitos controle e vitrificados com ou sem suplementos na eficiência da função mitocondrial, regulação do estado redox e controle intracelular das EROs, demonstrando que mais trabalhos são necessários para entender esta via metabólica e os diferentes efeitos dos meios de vitrificação. / Introduction. Cryopreservation of oocytes is important, both for the attempt to preserve female fertility and for assisted reproduction treatments. We hypothesize that novel cryoprotective formulations containing biomolecules that participate in cellular structure and functionality, particularly mitochondrial function and membrane system dynamics, could improve cryotolerance and safety of vitrification. Objeticve. The objective of this study was to investigate the effects of the standard vitrification medium (T4) and T4 supplemented with L-carnitine (LC), LC-fatty acids (T4-AG) and LC-AGphosphatidylcholine (T4-PC) on survival and quality of cryopreserved oocytes, measured by in vitro embryo development parameters, such as number of total nuclei (NT), cells in the internal cell mass (ICM) and trophoectoderma (TE) of the blastocysts derived from vitrified oocytes in these media, as well as on the patterns of oocyte mitochondrial activity. Materials and methods. Experimental study using the C57BL/6 mouse as a model. Matured in vivo oocytes were distributed into 5 groups: fresh (CT) control and four vitrified groups: T4, T4-LC, T4-AG and T4-PC. After devitrification, oocyte survival was analyzed and viable oocytes were submitted to in vitro fertilization or used for analysis of mitochondrial activity, through the analysis of intracellular reactive oxygen species (ROS) by Fluorescence Intensity emitted by diacetate of 2, 7-dichlorodihydrofluorescein, oxidative metabolism by the autofluorescence of two endogenous fluorophores [oxidized flavin adenine dinucleotide and the reduced dinucleotide of nicotinamide adenine (phosphate)] and mitochondrial membrane potential by Fluorescence Intensity (FI) emitted by JC1. The oocytes of the 5 groups submitted to IVF were cultured for 96 hours, being compared between the groups: fertilization rate and blastocyst formation, as well as number of NT, MCI and TE cells and size of blastocysts. Results. The survival rate of vitrified oocytes in T4 was higher than in the other groups T4-LC, T4-AG and T4-PC (respectively 100%, 97.07%, 96.75% and 97.95%). The fertilization rate of the CT group (77.5%) was higher than that of the T4, T4-LC and T4-PC groups, not differing from the T4-AG group. There were no statistically significant differences in the rates of blastocyst formation between the groups CT, T4, T4-LC, T4-AG and T4-PC (58.07%, 48.05%, 47.44%, 57.89% and 51.06%, respectively). Comparing the NT and TE cells of the blastocysts, it was observed that the values of the control group were higher than that of the other 4 groups, which did not present differences between them. The number of MCI cells from the blastocysts of the control group was higher than that of the T4 and T4-LC groups and similar to that of the T4-AG and T4-PC groups. For the mitochondrial activity profile, 15 oocytes/group were analysed. The levels of EROs were higher in the CT group compared to the T4 group and lower when compared to the T4-LC and T4-AG groups, but without significant difference in relation to the T4-PC group. For the analysis of the redox state, the CT group had higher values than the T4, T4-LC and T4-AG groups and the T4-PC group was higher than the other four groups. For the mitochondrial membrane potential, the CT group had higher values than the T4-LC group, lower than the T4 group and without a statistically significant difference with the T4-AG and T4-PC groups. Conclusion. The number of NT, TE cells and blastocyst size were lower in the vitrified/devitrified groups in standard medium and supplemented compared to control. However, the MCI cell number was not different between the control group and the vitrified T4-AG and T4-PC, suggesting that the supplementation of the standard media with LC, GA and CP could improve oocyte competence and subsequent embryo quality, which needs to be better investigated before the clinical application of the new media. Although vitrified oocytes in the T4 medium had a statistically higher survival rate than the other groups, we suggested that these differences would not present potential clinical relevance. The results of mitochondrial activity reveal that there is an important difference between control and vitrified oocytes with or without supplements in the efficiency of mitochondrial function, regulation of the redox state and intracellular control of ROS, demonstrating that more work is needed to understand this metabolic pathway and the different effects of the vitrification media.

Obesity-associated metabolic disorders are amongst the most prevalent causes of death worldwide. Understanding how obesity leads to the development of the Metabolic Syndrome (MetS) and cardiovascular disease (CVD) will enable the development of novel therapies that dissociate obesity from its cardiometabolic complications. Our laboratory views the functional capacity of white adipose tissue (WAT), the organ designed for safe lipid storage, as a key factor in the development of MetS and CVD. At a genetically-defined stage of the aberrant WAT expansion that occurs during obesity, adipocytes undergo a functional failure, resulting in an impaired control of serum free fatty acid (FFA) concentration. In such setting, FFAs and their metabolic derivatives accumulate in other organs, where they cause lipotoxicity, leading to the development of insulin resistance and CVD. We therefore aim to understand the pathophysiological mechanisms that induce adipocyte dysfunction. The past two decades of research have established the immune system as an important regulator of WAT function. The number of adipose tissue macrophages (ATMs), the most abundant immune cell type in WAT, increases during obesity, resulting in WAT inflammation. Multiple genetic and pharmacological intervention studies of murine models of obesity have assigned a causal link between ATM pro-inflammatory activation and WAT dysfunction. However, while the propagation of inflammation in ATMs during obesity has been extensively studied, factors triggering ATM inflammatory activation are less clear. Recently, our lab has observed lipid accumulation in the ATMs isolated from obese mice. Lipid-laden ATMs were pro-inflammatory, leading us to hypothesise that aberrant lipid build-up in macrophages triggers WAT inflammation during obesity. This thesis expands on the initial findings from our lab and describes two novel mechanisms that potentially contribute to lipid-induced inflammatory activation of ATMs. In chapter 3, the role of de novo phosphatidylcholine (PC) synthesis pathway during lipotoxicity in macrophages is addressed. The first part of the chapter demonstrates that lipotoxic environment increased de novo PC synthesis rate in bone marrow-derived macrophages (BMDMs) and ATMs, and that loss of rate-limiting enzyme in de novo PC synthesis pathway, CTP:phosphocholine cytidylyltransferase a (CCTa) diminished saturated FFA-induced inflammation in BMDMs. In the second part, I show that macrophage-specific CCTa deletion did not impact on the development of WAT inflammation or systemic insulin resistance, but had a minor benefitial effect on hepatic gene transcription during obesity. Chapter 4 develops on recent observations of interactions between sympathetic nerves and macrophages in WAT. In the first part of the chapter, I demonstrate that stimulating B2-adrenergic receptor (B2AR), the main receptor for sympathetic neurotransmitter norepinephrine in macrophages, enhanced intracellular triglyceride storage by up-regulating diacylglycerol O-acyltransferase 1 (Dgat1) gene expression in BMDMs. The second part of the chapter shows that macrophage-specific B2AR deletion did not modulate systemic glucose and lipid metabolism during obesity, but mice lacking B2ARs in macrophages demonstrated augmented hepatic glucose production on a chow diet. Furthermore, systemic B2AR blockade or macrophage-specific B2AR deletion in mice did not affect the thermogenic response to cold exposure. Chapter 5 includes the characterisation of B2AR stimulation-induced changes to the global cellular proteome of BMDMs, and a subsequent validation of the role of candidate transcription factors in regulating B2AR agonism-induced gene expression in BMDMs.

Introdução. A criopreservação de oócitos é importante, tanto para a tentativa de preservação da fertilidade feminina, como nos tratamentos de reprodução assistida. Hipotetizamos que novas formulações de meios crioprotetores, contendo biomoléculas que participam da estrutura e funcionalidade celular, em particular da função mitocondrial e da dinâmica do sistema de membranas, poderiam melhorar a criotolerância e segurança da vitrificação. Objetivos. Este estudo teve como objetivo investigar os efeitos do meio padrão de vitrificação (T4) e T4 suplementado com L-carnitina (LC), LC-ácidos graxos (T4-AG) e LC-AGfosfatidilcolina (T4-PC) sobre a sobrevida e qualidade de oócitos criopreservados, mensurada por parâmetros do desenvolvimento in vitro de embriões, como número de núcleos totais (NT), de células na massa celular interna (MCI) e trofectoderma (TE) dos blastocistos oriundos de oócitos vitrificados nestes meios, assim como sobre os padrões de atividade mitocondrial oocitária. Materiais e métodos. Estudo experimental usando o camundongo da cepa C57BL/6 como modelo. Oócitos maturados in vivo, foram distribuídos em 5 grupos: controle a fresco (CT) e 4 grupos vitrificados: T4, T4-LC, T4-AG e T4-PC. Após a desvitrificação, foi analisada a sobrevida oocitária e os oócitos viáveis foram submetidos a fertilização in vitro ou utilizados para análise da atividade mitocondrial, por meio da análise de espécies reativas de oxigênio (EROs) intracelular por Intensidade de Fluorescência emitida pelo diacetato de 2,7- diclorodihidrofluoresceína, metabolismo oxidativo pela autofluorescência de dois fluoróforos endógenos [dinucleótideo de flavina adenina oxidado e o dinucleotideo reduzido de nicotinamida adenina (fosfato)] e potencial de membrana mitocondrial por Intensidade de Fluorescência (IF) emitida pelo JC1. Os oócitos dos 5 grupos submetidos a FIV foram cultivados por 96 horas, sendo comparados entre os grupos: taxa de fertilização e formação de blastocisto, assim como o número de NT, células MCI e TE e tamanho dos blastocistos. Resultados. A taxa de sobrevivência dos oócitos vitrificados em T4 foi superior a dos demais grupos T4-LC, T4-AG e T4-PC (respectivamente 100%, 97,07%, 96,75% e 97,95%). A taxa de fertilização do grupo CT (77,5%) foi superior a dos grupos T4, T4-LC e T4-PC, não diferindo do grupo T4-AG. Não foram evidenciadas diferenças estatisticamente significativas nas taxas de formação de blastocistos entre os grupos CT, T4, T4-LC, T4-AG e T4-PC (58,07%, 48,05%, 47,44%, 57,89% e 51,06%,respectivamente). Comparando-se o número NT e de células do TE dos blastocistos, observou-se que o os valores do grupo controle foram maiores do que o dos outros 4 grupos, que não apresentaram diferenças entre si. O número de células da MCI dos blastocistos do grupo controle foi superior ao dos grupos T4 e T4-LC e similar ao dos grupos T4-AG e T4- PC. Para o perfil de atividade mitocondrial, foram analisados 15 oócitos/grupo. Os níveis de EROs foram maiores no grupo CT comparado ao grupo T4 e menor quando comparado aos grupos T4-LC e T4-AG, mas sem diferença significativa em relação ao grupo T4-PC. Para Resumo analise do estado redox, o grupo CT teve maiores valores do que a dos grupos T4, T4-LC e T4- AG e o grupo T4-PC foi maior do que a dos outros quatro grupos. Para o potencial de membrana mitocondrial, o grupo CT teve maiores valores do que a do grupo T4-LC, menor do que a do grupo T4 e sem diferença estatisticamente significativa com a dos grupos T4-AG e T4-PC. Conclusão. O número de NT, células do TE e tamanho do blastocistos foram inferiores nos grupos vitrificados/desvitrificados em meio padrão e suplementados comparados ao controle. Porém, o número de células da MCI não foi diferente entre o grupo controle e os vitrificados T4- AG e T4-PC, sugerindo que a suplementação dos meios padrão com LC, AG e PC possa melhorar a competência do oócito e a subsequente qualidade embrionária, o que precisa ser melhor investigado antes da aplicação clínica dos novos meios. Apesar dos oócitos vitrificados no meio T4 terem apresentado taxa de sobrevivência estatisticamente superior a dos demais grupos, sugerimos que estas diferenças não apresentariam potencial relevância clínica. Os resultados de atividade mitocondrial revelam que há uma diferença importante entre oócitos controle e vitrificados com ou sem suplementos na eficiência da função mitocondrial, regulação do estado redox e controle intracelular das EROs, demonstrando que mais trabalhos são necessários para entender esta via metabólica e os diferentes efeitos dos meios de vitrificação. / Introduction. Cryopreservation of oocytes is important, both for the attempt to preserve female fertility and for assisted reproduction treatments. We hypothesize that novel cryoprotective formulations containing biomolecules that participate in cellular structure and functionality, particularly mitochondrial function and membrane system dynamics, could improve cryotolerance and safety of vitrification. Objeticve. The objective of this study was to investigate the effects of the standard vitrification medium (T4) and T4 supplemented with L-carnitine (LC), LC-fatty acids (T4-AG) and LC-AGphosphatidylcholine (T4-PC) on survival and quality of cryopreserved oocytes, measured by in vitro embryo development parameters, such as number of total nuclei (NT), cells in the internal cell mass (ICM) and trophoectoderma (TE) of the blastocysts derived from vitrified oocytes in these media, as well as on the patterns of oocyte mitochondrial activity. Materials and methods. Experimental study using the C57BL/6 mouse as a model. Matured in vivo oocytes were distributed into 5 groups: fresh (CT) control and four vitrified groups: T4, T4-LC, T4-AG and T4-PC. After devitrification, oocyte survival was analyzed and viable oocytes were submitted to in vitro fertilization or used for analysis of mitochondrial activity, through the analysis of intracellular reactive oxygen species (ROS) by Fluorescence Intensity emitted by diacetate of 2, 7-dichlorodihydrofluorescein, oxidative metabolism by the autofluorescence of two endogenous fluorophores [oxidized flavin adenine dinucleotide and the reduced dinucleotide of nicotinamide adenine (phosphate)] and mitochondrial membrane potential by Fluorescence Intensity (FI) emitted by JC1. The oocytes of the 5 groups submitted to IVF were cultured for 96 hours, being compared between the groups: fertilization rate and blastocyst formation, as well as number of NT, MCI and TE cells and size of blastocysts. Results. The survival rate of vitrified oocytes in T4 was higher than in the other groups T4-LC, T4-AG and T4-PC (respectively 100%, 97.07%, 96.75% and 97.95%). The fertilization rate of the CT group (77.5%) was higher than that of the T4, T4-LC and T4-PC groups, not differing from the T4-AG group. There were no statistically significant differences in the rates of blastocyst formation between the groups CT, T4, T4-LC, T4-AG and T4-PC (58.07%, 48.05%, 47.44%, 57.89% and 51.06%, respectively). Comparing the NT and TE cells of the blastocysts, it was observed that the values of the control group were higher than that of the other 4 groups, which did not present differences between them. The number of MCI cells from the blastocysts of the control group was higher than that of the T4 and T4-LC groups and similar to that of the T4-AG and T4-PC groups. For the mitochondrial activity profile, 15 oocytes/group were analysed. The levels of EROs were higher in the CT group compared to the T4 group and lower when compared to the T4-LC and T4-AG groups, but without significant difference in relation to the T4-PC group. For the analysis of the redox state, the CT group had higher values than the T4, T4-LC and T4-AG groups and the T4-PC group was higher than the other four groups. For the mitochondrial membrane potential, the CT group had higher values than the T4-LC group, lower than the T4 group and without a statistically significant difference with the T4-AG and T4-PC groups. Conclusion. The number of NT, TE cells and blastocyst size were lower in the vitrified/devitrified groups in standard medium and supplemented compared to control. However, the MCI cell number was not different between the control group and the vitrified T4-AG and T4-PC, suggesting that the supplementation of the standard media with LC, GA and CP could improve oocyte competence and subsequent embryo quality, which needs to be better investigated before the clinical application of the new media. Although vitrified oocytes in the T4 medium had a statistically higher survival rate than the other groups, we suggested that these differences would not present potential clinical relevance. The results of mitochondrial activity reveal that there is an important difference between control and vitrified oocytes with or without supplements in the efficiency of mitochondrial function, regulation of the redox state and intracellular control of ROS, demonstrating that more work is needed to understand this metabolic pathway and the different effects of the vitrification media.

<p>This thesis covers a wide range of analytical method development for lipid analysis in complex biological samples; from sample preparation using pressurized fluid extraction (PFE) and separation with reversed phase capillary liquid chromatography (RP-LC) to detection by electrospray ionization mass spectrometry (ESI/MS) and tandem MS.</p><p>The requirements for fast, reliable and selective extraction methods with minimal usage of solvents have accelerated the development of new extraction techniques. PFE is one of the new automated, fast and efficient liquid extraction techniques which use elevated temperature and pressure with standard liquid solvents. In this thesis the reliability and efficiency of the PFE technique was investigated for the extraction of total lipid content from cod, herring muscle and human brain tissue as well as for pesticides from fatty foodstuffs. Improved or comparable efficiencies were achieved with reduced time and solvent consumption as compared to traditional methods. </p><p>A RP-LC coupled online to ESI/MS for the analysis of phosphatidylcholine (PC) and sphingomyelin (SM) molecular species was developed and used for the analysis of brain lipids from eight groups of mice treated with vehicle and various neuroleptics. The effect of postnatal iron administration in lipid composition and behavior was investigated. Whether or not these effects could be altered by subchronic administration of the neuroleptics (clozapine and haloperidol) were examined. The results support the hypothesis that an association between psychiatric disorders, behavior abnormalities and lipid membrane constitution in the brain exists.</p><p>Finally, a tandem MS precursor ion scan was used to analyze the developmental profile of brain sulfatide accumulation in arylsulfatase A (ASA) deficient (ASA -/-) as compared to wild type control (ASA +/+) mice. The ASA -/- mice were developed as a model of the monogenic disease metachromatic leukodystrophy with an established deficiency of the lysosomal enzyme ASA. The results showed that an alteration in the composition of sulfatide molecular species was observed between the ASA -/- and ASA +/+ mice.</p><p>This thesis shows that modern analytical methods can provide new insights in the extraction and analysis of lipids from complex biological samples.</p>

<p>One of the main obstacles to maintaining patients with short bowel syndrome on parenteral nutrition, or successfully transplanting these patients with a small bowel graft, is the many severe infections that occur. Evidence is accumulating that translocating bacteria from the patient’s bowel causes a significant part of these infections. In this thesis bacterial translocation is studied in a Thiry-Vella loop of defunctionalised small bowel in the rat. </p><p>Bacterial translocation to the mesenteric lymph nodes (MLNs) occurs in almost 100% of the rats after three days. No systemic spread of bacteria is observed unless there is additional immunosupression with depletion of Kupffer cells in the liver. However, blocking the function of α/β T cells does not increase the translocation. Removal of MLNs does not either aggravate bacterial translocation in the Thiry-Vella loop model. Conversely, after small bowel transplantation translocating bacteria spread systemically if the MLNs are removed. </p><p>The Thiry-Vella loop should also be a suitable model for the testing of potentially translocation-inhibiting substances. Reinforcement of the intestinal barrier with glutamine or phosphatidylcholine proved insufficient in decreasing bacterial translocation. Even selective bowel decontamination with tobramycin failed to abolish bacterial translocation. Thus, it seems that the driving force for translocation in this model is strong regardless of the relatively small trauma of intestinal defunctionalisation.</p><p>Flow cytometric studies of the immune cells in the spleen MLNs showed a decrease in MHC class II positive T cells in the MLNs of the Thiry-Vella loop. Concurrently the number of macrophages increased with time as observed by immunohistochemistry. The fraction of MHC class II negative macrophages increased in the spleens of rats treated with glutamine. </p><p>In conclusion, the Thiry-Vella loop model offers possibilities of immunological as well as mechanistic studies on bacterial translocation from small intestine.</p>

This thesis covers a wide range of analytical method development for lipid analysis in complex biological samples; from sample preparation using pressurized fluid extraction (PFE) and separation with reversed phase capillary liquid chromatography (RP-LC) to detection by electrospray ionization mass spectrometry (ESI/MS) and tandem MS. The requirements for fast, reliable and selective extraction methods with minimal usage of solvents have accelerated the development of new extraction techniques. PFE is one of the new automated, fast and efficient liquid extraction techniques which use elevated temperature and pressure with standard liquid solvents. In this thesis the reliability and efficiency of the PFE technique was investigated for the extraction of total lipid content from cod, herring muscle and human brain tissue as well as for pesticides from fatty foodstuffs. Improved or comparable efficiencies were achieved with reduced time and solvent consumption as compared to traditional methods. A RP-LC coupled online to ESI/MS for the analysis of phosphatidylcholine (PC) and sphingomyelin (SM) molecular species was developed and used for the analysis of brain lipids from eight groups of mice treated with vehicle and various neuroleptics. The effect of postnatal iron administration in lipid composition and behavior was investigated. Whether or not these effects could be altered by subchronic administration of the neuroleptics (clozapine and haloperidol) were examined. The results support the hypothesis that an association between psychiatric disorders, behavior abnormalities and lipid membrane constitution in the brain exists. Finally, a tandem MS precursor ion scan was used to analyze the developmental profile of brain sulfatide accumulation in arylsulfatase A (ASA) deficient (ASA -/-) as compared to wild type control (ASA +/+) mice. The ASA -/- mice were developed as a model of the monogenic disease metachromatic leukodystrophy with an established deficiency of the lysosomal enzyme ASA. The results showed that an alteration in the composition of sulfatide molecular species was observed between the ASA -/- and ASA +/+ mice. This thesis shows that modern analytical methods can provide new insights in the extraction and analysis of lipids from complex biological samples.