Introdução: A doxorrubicina (DOX) é um quimioterápico que gera efeitos tóxicos no tecido adiposo (T.A.) e reduz a qualidade de vida dos pacientes. Objetivos: Investigar os efeitos metabólicos do tratamento com DOX no T.A. branco e propor terapia adjuvante que atenue efeitos deletérios. Métodos: Procedimento experimental 1: ratos Wistar foram tratados com dose única de DOX (15mg/kg). Cultura de células: 3T3L1 foram incubadas por 24h, 96h e 12 dias com DOX. Procedimento experimental 2: animais C57/BL6 receberam doses fracionadas de DOX associado ao uso de metformina (MET) (300mg/kg, diário) ou não. Conclusão: A DOX gera um alto impacto sobre a homeostasia do T.A. branco tanto no tratamento agudo com dose única, como no tratamento crônico com doses mais baixas. Os processos fisiológicos do tecido adiposo sofreram profundas alterações, o que resultou em menor tamanho do adipócito, maior fibrose, diminuição das vias metabólicas e redução da adiponectina e leptina circulantes, e o tratamento com MET não reverteu esses efeitos, só prevenindo o processo de fibrose do TA. / Introduction: Doxorubicin (DOX) is a chemotherapy that generates toxic effects on adipose tissue (AT) and reduces the quality of life of patients. Objectives: To investigate the metabolic effects of treatment with DOX on AT white and to propose adjuvant therapy to mitigate deleterious effects. Methods: Experimental Procedure 1: Wistar rats were treated with a single dose of doxorubicin (15mg/ kg). Cell Culture: 3T3-L1 were incubated for 24h, 96h and 12 days with doxorubicin. Experimental procedure 2: C57/BL6 mice received fractionated doses of DOX associated with the use of metformin (MET) (300 mg/kg daily) or not. Conclusion: DOX generates a high impact on the homeostasis of white AT in both acute single dose treatment, such as in chronic treatment with lower doses. The physiological processes of AT have undergone major changes, resulting in a smaller of adipocytes, increased fibrosis, reduction in metabolic pathways and decreased circulating adiponectin and leptin, and the treatment with MET did not reverse these effects, only prevent the fibrosis process on AT.

Submitted by Angela Maria de Oliveira (amolivei@uepg.br) on 2018-05-14T14:39:42Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Janete Machozeki.pdf: 3460027 bytes, checksum: 87b38a12a4dede2c42dbef87dd9de037 (MD5) / Made available in DSpace on 2018-05-14T14:39:42Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Janete Machozeki.pdf: 3460027 bytes, checksum: 87b38a12a4dede2c42dbef87dd9de037 (MD5) Previous issue date: 2018-03-28 / A obesidade é uma doença multifatorial, com fisiopatologia complexa e atua como fator de risco para outras doenças, principalmente diabetes mellitus tipo 2 e doença cardiovascular. Quando a resistência insulínica está presente, caracteriza a síndrome metabólica, constituída por inflamação crônica de baixo grau, estresse oxidativo e disfunção de adipócitos. Esta pesquisa interdisciplinar avalia o efeito do uso precoce da metformina ou do orlistat na prevenção da disfunção de adipócitos em ratos wistar machos, adultos, submetidos à dieta hiperglicídica e hiperlipídica. Neste estudo foram avaliados quatro grupos de 10 animais, sendo que o grupo controle recebeu ração padrão balanceada. Outros 3 grupos receberam ração de cafeteria modificada, sendo que em 2 grupos houve intervenção farmacológica, 1 com metformina (40mg/dia) e outro com orlistat (10 mg/dia). As doses foram calculadas fundamentadas na taxa metabólica basal. Foram comparados evolução ponderal, parâmetros bioquímicos, e avaliação histomorfométrica da gordura visceral. Não houve diferença estatisticamente significativa na média de peso e nem nos parâmetros bioquímicos na comparação entre os grupos (p>0,05). Na avaliação histomorfométrica evidenciou-se hiperplasia de adipócitos em todos os grupos, porém foi mais significativo no grupo que usou a dieta padrão comparado aos que usaram dieta de cafeteria modificada, com ou sem intervenção terapêutica (p<0,001). Ocorreu maior hipertrofia de adipócitos no grupo que utilizou a dieta de cafeteria modificada (p<0,001). Os grupos com intervenção terapêutica não apresentaram diferença estatística quando em relação ao grupo de dieta balanceada (p>0,05). Este estudo demonstrou que doses pequenas de metformina ou orlistat preveniram a hipertrofia de adipócitos na gordura visceral, que é a etapa determinante para o desenvolvimento da síndrome metabólica. Esta pesquisa demonstrou que pode ser possível a prevenção de doenças crônicas não transmissíveis relacionadas à disfunção de adipócitos. / Obesity is a disease with a complex multifactorial pathophysiology and acts as a risk factor for other diseases, particularly type 2 diabetes mellitus and cardiovascular disease. When insulin resistance is present, the metabolic syndrome, consisting of chronic low-grade inflammation, oxidative stress and dysfunction of adipocytes. This interdisciplinary research evaluates the effect of early use of metformin or orlistat in preventing dysfunction of adipocytes in male wistar rats, adults, submitted to hiperglicídica and hiperlipídica diet. In this study we evaluated four groups of 10 animals, and the control group received standard balanced ration. Other 3 groups received cafeteria modified ration, and in 2 groups there was drug intervention, 1 with metformin (40 mg/day) and another with orlistat (10 mg/day). The doses were calculated based on basal metabolic rate. Were compared weight, biochemical parameter, and histomorphometry evaluation of visceral fat. There was no statistically significant difference in weight and nor in biochemical parameters in comparison between the groups (p > 0.05). Histomorphometry evaluation showed hyperplasia of adipocytes in all groups but was most significant in the group that used the standard diet compared to that used modified cafeteria diet, with or without therapeutic intervention (p < 0.001). Occurred more in the adipocytes of hypertrophy group that used the cafeteria diet modified p < 0.001). The therapeutic intervention groups showed no statistical difference when compared to the balanced diet Group (p > 0.05). This study has shown that small doses of metformin or orlistat prevented the hypertrophy of adipocytes in visceral fat, which is the decisive step for the development of the metabolic syndrome. This research demonstrated that it may be possible to the prevention of non-communicable chronic diseases related to dysfunction of adipocytes.

O câncer de mama representa um grave problema de saúde pública. Dentre os fármacos empregados, destaca-se o paclitaxel, um agente citotóxico eficaz, porém associado a severos efeitos colaterais. A metformina hidrocloreto tem obtido resultados promissores para o tratamento de neoplasias, porém é bastante hidrofílica, fator limitante da biodisponibilidade. A rapamicina tem demonstrado sinergismo com paclitaxel e potente atividade antitumoral. Todavia, é um fármaco lipofílico e possui desvantagens. Sistemas nanoestruturados de fármacos como lipossomas PEGlados são largamente empregados para a melhora da farmacocinética e potencialização da ação terapêutica. Ademais, a funcionalização de lipossomas com anticorpos monoclonais pode permitir a entrega seletiva do fármaco encapsulado à célula alvo. No presente trabalho objetivou-se desenvolver e caracterizar lipossomas e imunolipossomas funcionalizados com trastuzumabe, contendo paclitaxel, metformina hidrocloreto e/ou rapamicina, bem como avaliar as formulações através de estudos in vitro e in vivo. Os resultados mostraram que a metformina hidrocloreto foi encapsulada com baixa eficiência, menor que 20%, ao passo que paclitaxel e rapamicina puderam ser co-encapsulados com adequados valores de eficiência de encapsulação, equivalente a 56,32% para paclitaxel e 73,31% para rapamicina, e tamanho de partícula nanométrico, de 136,95 nm em composição biocompatível baseada em SPC:Col:DSPE-PEG(2000). Os dois fármacos apresentaram liberação lenta, e foram convertidos às formas molecular e amorfa, respectivamente para paclitaxel e rapamicina quando encapsulados. Os imunolipossomas foram funcionalizados com elevada eficiência com trastuzumabe e mantiveram o tamanho nanométrico, com adequados valores de encapsulação dos fármacos. Ainda, mostrou-se o sinergismo entre paclitaxel e rapamicina coencapsulados em lipossomas em células triplo negativas (4T1) e houve sinergismo entre os dois fármacos, mediado pelo anticorpo em imunolipossomas frente à linhagem celular HER2 positiva (SKBR3), em virtude do aumento do uptake celular mediado pelo trastuzumabe. Finalmente, os resultados obtidos in vitro foram confirmados in vivo, sendo que os lipossomas com paclitaxel e rapamicina coencapsulados foram capazes de controlar o crescimento tumoral em modelo de câncer de mama triplo negativo, ao passo que o imunolipossoma com os dois fármacos permitiu o controle do crescimento de tumores xenográficos HER2 positivos, cuja média de volume tumoral correspondeu a 25,27%, 44,38% e 47,78% das médias dos volumes tumorais de controle negativo, positivo e lipossoma, respectivamente. Portanto, a formulação desenvolvida nesse trabalho tem potencial para ser avaliada em estudos clínicos. / Breast cancer represents a severe public health problem. Among the drugs used in the treatment, paclitaxel is an effective cytotoxic drug, but associated with side effects. Hydrocloride metformin has shown promising results for cancer treatment, however it is very hydrophilic, a limiting factor for bioavailability. Rapamycin has demonstrated synergism with paclitaxel and potent anticancer activity, though it is a lipophilic drug with drawbacks that compromise its bioavailability. Nanostructured drug delivery systems, such as PEGylated liposomes are largely employed for pharmacokinetics improvement and enhancement of therapeutic effect. Furthermore, the functionalization of liposomes with monoclonal antibodies enables the selective delivery of the loaded drug to the target cell. In the present work, we aimed to develop and characterize liposomes and immunoliposomes functionalized with trastuzumab, containing paclitaxel, hydrocloride metformin and/or rapamycin, as well as to evaluate the formulations through in vitro and in vivo studies. The results showed that hydrocloride metformin was encapsulated with low efficiency, less than 20%, on the other hand paclitaxel and rapamycin could be co-loaded with suitable values of encapsulation efficiency, 56.32% for paclitaxel and 73.31% for rapamycin and nanometric particle size, 136.95 nm, based on a SPC:Chol:DSPE-PEG(2000) composition. The two drugs displayed slow release, and were converted to molecular and amorphous form, respectively for paclitaxel and rapamycin when encapsulated. The immunoliposomes were developed with high efficiency with trastuzumab and kept the nanometric size, with adequate encapsulation of drugs. Moreover, herein it was shown the synergism between paclitaxel and rapamycin co-loaded in liposomes in triple negative cells (4T1) and there was synergism between the two drugs mediated by the antibody in immunoliposomes in the HER2-positive cell line (SKBR3), due to the improved cell uptake mediated by trastuzumab. Finally, the results obtained in vitro were confirmed in vivo. Co-loaded paclitaxel and rapamycin were able to control tumor growth in a triple negative breast cancer animal model, while the immunoliposome containing the two drugs allowed for better control of tumor growth in a HER2-positive breast xenograft model, whose average tumor volume corresponded to 25.27%, 44.38% and 47.78% of the tumor volumes of positive control, negative control and liposome, respectively. Therefore, the formulation developed herein has potential to be evaluated in clinical trials.

Aims: Thiazolidinediones have been advocated as second or third line insulin sensitizing agents in the management of type 2 diabetes (T2DM). Their widespread use has been hampered by concerns about their cardiovascular safety, including fluid retention. Metformin is established as first-line glucose-lowering pharmacotherapy in T2DM. It has also been suggested that it may have benefits in alleviating insulin resistance in type 1 diabetes (T1DM). This thesis examined: (i) cardiovascular, renal and metabolic differences between individuals with T2DM ‘tolerant’ or ‘intolerant’ of TZDs; (ii) risk factors for TZD-associated oedema in T2DM; and (iii) the potential for metformin as adjunct therapy in T1DM. Methods: (i) A small clinical study characterising TZD tolerant and intolerant individuals with T2DM; (ii) A population-based epidemiological study of TZD induced oedema in individuals with T2DM in Tayside, Scotland (using incident loop diuretic prescription as a surrogate); (iii) A systematic review and meta-analysis of published studies of adjunct metformin in T1DM. Results (i) During a five-day high sodium diet, two known TZD-intolerant individuals with T2DM had reductions in haematocrit, aldosterone, and diastolic BP and increases in ANP and central and peripheral augmentation indices which were outwith reference ranges derived from nine TZD-tolerant individuals; (ii) Predictors of time to loop diuretic prescription included age, body mass index, systolic BP, haematocrit, ALT and macrovascular disease but rates of this outcome did not differ by therapy: 4.3% (TZDs) vs 4.7% (other agents) [unadjusted OR 0.909 (95% CI 0.690, 1.196); p = 0.493]; (iii) In meta-analysis of nine small studies in T1DM (192.8 patient-years of follow-up), metformin was associated with a reduction in total daily insulin dose (6.6 units/day; p < 0.001) but no studies examined cardiovascular surrogates or outcomes. Conclusions: Hypotheses were generated for several potential biomarkers predictive of TZD-induced oedema but the clinical importance of TZDs as a risk factor for oedema in individuals with T2DM was questioned. As there is some evidence for the safety of metformin as an adjunct therapy in T1DM but little evidence of efficacy, larger studies are warranted.

Non-alcoholic fatty liver disease (NAFLD) results from an unequal uptake/storage and export/oxidation of lipids within the liver and is often a secondary disease to type II diabetes (22). NAFLD causes this imbalance of lipids by altering glucose and lipid metabolism, which corresponds to a decrease in mitochondrial function leading to failure of the liver. One established treatment for type II diabetes and NAFLD is the drug metformin, which has similar properties to the newly discovered CTRP 3 protein which is part of a group of bioactive molecules secreted by adipose tissue, collectively termed adipokines (2-4). Both have similar effects on hepatic glucose and lipid metabolism and both specifically suppress hepatic gluconeogenesis (11, 17, 27, 29). The revolutionary Seahorse extracellular flux analyzer was used to measure the metabolism of H4IIE hepatocytes without use of radiolabeling (1). By detecting the Oxygen Consumption Rate (OCR) of hepatocytes the level of metabolic function within mitochondria can be measured. Once an effective protocol was established using this new technology, hepatocytes treated with metformin had a significantly lower OCR compared to control treated hepatocytes treated. However, H4IIE hepatocytes treated with metformin and palmitate had a significant increase in OCR and eventually equilibrated with the lower OCR of hepatocytes solely treated with metformin. With similar effect, hepatocytes treated with CTRP3 and palmitate caused a drastic increase in OCR while hepatocytes treated with only CTRP3 had a decrease in OCR. This suggests that CTRP3 increases fatty acid oxidation which decreases lipid concentrations within hepatocytes which could mean future protection of liver against NAFLD. In conclusion, our Seahorse XF analyzer models compare metformin and CTRP3’s similarities and suggest the possible liver protective functions of CTRP3. Our results will aid in future research of CTRP3 to further determine its possible uses as a treatment for liver-associated diseases.

Modulation of mitochondrial complex I during reperfusion reduces cardiac injury. Complex I exists in two structural states: active (A) and deactive (D) with transition from A→D during ischemia. Reperfusion reactivates D→A with an increase in ROS production. Metformin preserves the D-Form. Our aim was to study the contribution of maintenance of deactivation of complex I during early reperfusion by metformin to protect against ischemia reperfusion injury. Our results showed that metformin decreased H9c2 cardiomyoblast apoptosis and total cell death following simulated ischemia for six hours followed by reoxygenation for twenty four hours compared to untreated cells. Reactive oxygen species (ROS) generation was reduced at the onset of reoxygenation with metformin treatment. Metformin also prevented the acute reactivation of complex I during reoxygenation following 10 minutes of hypoxia accompanied by decreased ROS generation. In addition, the content of C/EBP homologous protein was decreased in metformin treated cells, suggesting that metformin treatment decreased endoplasmic reticulum stress. 5' adenosine monophosphate-activated protein kinase was activated in our model independent of metformin treatment. Intriguingly, metformin protects in 5' adenosine monophosphate-activated protein kinase knock down system. Surprisingly, we found that metformin successfully downregulated p53 compared to untreated simulated ischemia reoxygenation. We sought potential metformin related impact on anti-apoptotic protein B-cell lymphoma 2. Our results showed the expression of the anti-apoptotic protein B-cell lymphoma 2 was markedly decreased in SI6/RO24 and metformin increased expression of B-cell lymphoma 2. Metformin, likely by partial inhibition of complex I with decreased ROS generation, resulted in less sulfhydryl modification and decreased modification of thiol groups by nitrosylation. We propose that the slowing down of activation of complex I at early stage of reperfusion by acute use of high dose metformin would be protective in cells and hearts against ischemia reperfusion injury. This potential new mechanism of protection is relevant at the onset of reperfusion to directly modulate electron transport to achieve cardiac protection and to decrease cardiac cell injury. Modulation of mitochondrial complex I during reperfusion reduces cardiac injury. Complex I exists in two structural states: active (A) and deactive (D) with transition from A→D during ischemia. Reperfusion reactivates D→A with an increase in ROS production. Metformin preserves the D-Form. Our aim was to study the contribution of maintenance of deactivation of complex I during early reperfusion by metformin to protect against ischemia reperfusion injury. Our results showed that metformin decreased H9c2 cardiomyoblast apoptosis and total cell death following simulated ischemia for six hours followed by reoxygenation for twenty four hours compared to untreated cells. Reactive oxygen species (ROS) generation was reduced at the onset of reoxygenation with metformin treatment. Metformin also prevented the acute reactivation of complex I during reoxygenation following 10 minutes of hypoxia accompanied by decreased ROS generation. In addition, the content of C/EBP homologous protein was decreased in metformin treated cells, suggesting that metformin treatment decreased endoplasmic reticulum stress. 5' adenosine monophosphate-activated protein kinase was activated in our model independent of metformin treatment. Intriguingly, metformin protects in 5' adenosine monophosphate-activated protein kinase knock down system. Surprisingly, we found that metformin successfully downregulated p53 compared to untreated simulated ischemia reoxygenation. We sought potential metformin related impact on anti-apoptotic protein B-cell lymphoma 2. Our results showed the expression of the anti-apoptotic protein B-cell lymphoma 2 was markedly decreased in SI6/RO24 and metformin increased expression of B-cell lymphoma 2. Metformin, likely by partial inhibition of complex I with decreased ROS generation, resulted in less sulfhydryl modification and decreased modification of thiol groups by nitrosylation. We propose that the slowing down of activation of complex I at early stage of reperfusion by acute use of high dose metformin would be protective in cells and hearts against ischemia reperfusion injury. This potential new mechanism of protection is relevant at the onset of reperfusion to directly modulate electron transport to achieve cardiac protection and to decrease cardiac cell injury.

Le cancer de la prostate est un véritable problème de santé publique qui se situe au premier rang des cancers incidents chez l’homme. Les cellules tumorales ont un métabolisme différent des cellules normales, et cibler le métabolisme des cellules cancéreuses est devenu une stratégie thérapeutique prometteuse. La metformine est un médicament couramment prescrit contre le diabète de type II, qui possède des propriétés anti-tumorales et affecte le métabolisme des cellules cancéreuses. L'augmentation de la lipogenèse est observée dans nombreux cancers dont le cancer de la prostate. Nous montrons que la metformine inhibe la lipogenèse dans les cellules cancéreuses de prostate via un déficit énergétique cellulaire. En effet, l’ATP est diminuée de façon dose dépendante par la metformine et cette diminution est significativement corrélée avec l'inhibition de la lipogenèse. De plus, la metformine induit un gonflement des mitochondries et une désorganisation des crêtes mitochondriales dans les cellules cancéreuses de prostate. De façon intéressante, nous observons que la metformine provoque une augmentation des flux calciques et un relargage du calcium du réticulum endoplasmique. Nous émettons l'hypothèse que ce calcium s'accumule dans la mitochondrie ce qui pourrait générer un gonflement de celles-ci. En réponse à ces signaux calciques ou à la diminution de la fonctionnalité des mitochondries, la metformine stimule la biogenèse mitochondriale dans les cellules cancéreuses de prostate. En conclusion, cette étude a permis de mieux comprendre les mécanismes moléculaires et cellulaires induits par la metformine dans le cancer de la prostate. / Prostate cancer is a major public health problem. Tumor cells have a different metabolism than normal cells, and targeting cancer cells metabolism becomes a promising therapeutic strategy. Metformin is a commonly prescribed anti-diabetic drug which has anti-tumor properties. Increased lipogenesis is a common feature of cancer cells including prostate cancer. We show that metformin effect on lipogenesis is due to a cellular energy deficit. Lipogenesis requires ATP and the decrease in ATP induced by metformin is significantly correlated with the inhibition of lipogenesis. Furthermore, we demonstrate that metformin induces mitochondrial swelling and disruption of cristae in prostate cancer cells. Interestingly, we show that metformin triggers a calcium flux and the release of calcium from the endoplasmic reticulum. We hypothesize that the accumulation of calcium into the mitochondria generates its swelling. In addition, we show that metformin stimulates mitochondrial biogenesis in prostate cancer cells. In conclusion, this study allowed to better understand the molecular and cellular mechanisms induced by metformin in prostate cancer.

Formation of advanced glycation endproducts (AGEs) on proteins has been linked to the pathogenesis of diabetic complications. Importantly, elevated levels of methylglyoxal (MG) occur in type 2 diabetes mellitus (T2DM), and the resulting site-specific formation of stable adducts on arginine residues can cause protein damage. Using MG, site-specific modifications on the plasma protein plasminogen (Pg) were determined following protein digestion into peptides and liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis, and 30 arginine sites were identified on the protein. Investigation into three of the most highly modified sites, R504, R530, and R561, using molecular modeling, identified likely functional changes to the Pg cleavage and the lysine binding pocket as a result of adduct formation at these sites. Overall functional changes to Pg were examined using silver staining and kinetic assays to examine normal protein cleavage by activator enzymes streptokinase (STK), tissue plasminogen activator (tPA) and urokinase plasminogen activator (uPA). MG-modified Pg exhibited decreased activation into plasmin (Pn), which is the active enzyme that forms via normal Pg cleavage, by all three activator enzymes. Activation into Pn by STK was significantly delayed by MG modification on plasminogen. Similar effects were observed with tPA and uPA. Efforts to identify the primary sites of MG adduction on Pg by two dimensional gel electrophoresis (2DGE) identified six sites, including R504 and R530, as the earliest modified sites. In order to probe MG site specific modification effects on lysine binding, MG-modified protein was run through a lysine-sepharose binding column and fractions were collected. The results indicated that MG-modified Pg bound more weakly to the column and eluted easier than unmodified Pg and LC-MS/MS using a LTQ Orbitrap Velos of the fraction indicated that R504 and R530 were the primary sites of MG adduction within the eluate. To assess MG-modification of Pg in humans, 12 plasma samples were immunodepleted of the top 14 abundant proteins and samples were analyzed by LC-MS/MS using a LTQ Orbitrap Velos. Nine of the 12 patient samples indicated the presence of MG-modified peptides. The antihyperglycemic drug metformin, a drug that scavenges MG and lowers formation of AGEs, was studied in order to better elucidate this scavenging mechanism. A novel reaction imidazolinone product, IMZ, was determined to be the primary product formed in the reaction between metformin and MG, confirmed unequivocally through x-ray diffraction analysis. In order to determine levels of IMZ in human patients on metformin therapy, multiple reaction monitoring (MRM) was employed to quantify the compound. Human urine samples from 92 patients on metformin treatment were analyzed. 66 of the 68 patients to exhibit high concentrations of metformin also indicated the presence of IMZ in their urine. The remaining samples either exhibited no metformin, or levels of metformin too low to detect the presence of IMZ. Importantly, IMZ was never identified in patients without a metformin signal, indicating the validity and quality of the assay. This dissertation builds upon the current knowledge of site-specific MG modifications, both in vitro, identifying for the first time Pg as a sensitive site-specific target of glycation, with functional effects, and importantly in humans, as this is the first identification of MG-modified Pg in vivo. The functional effects associated with this modification may provide a link between elevated MG in T2DM, and resulting cardiovascular complications. Additionally, the identification of the novel reaction product IMZ is important, as it helps to fully elucidate the role metformin plays in treating T2DM patients. The detection of IMZ in the urine of human patients on metformin therapy indicates that metformin plays a role in the reducing MG levels through scavenging in vivo, and the developed MRM method allows for future rapid, sensitive study of cohorts to better understand this mechanism and the role it plays in reducing AGEs and diabetic complications.

Neurons perform complex computations, communications and precise transmissions of information in the form of action potentials (APs). The high level of heterogeneity and complexity at all levels of organization within a neuron and the functional requirement of highly permeable cell membranes leave neurons exposed to damage when energy levels are insufficient for the active maintenance of ionic gradients. When energy is limiting the ionic gradient across a neuron’s cell membrane risks being dissipated which can have dire consequences. Other researchers have advocated “generalized channel arrest” and/or “spike arrest” as a means of reducing the neuronal permeability allowing neurons to adjust the demands placed on their electrogenic pumps to lower levels of energy supply. I investigated the consequences of hypoxia on the propagation of a train of APs down the length of a fast conducting axon capable of transmitting APs at very high frequencies. Under normoxic conditions I found that APs show conduction velocities and instantaneous frequencies nearly double that of neurons experiencing energy limiting hypoxic conditions. I show that hypoxia affects AP conduction differently for different lengths of axon and for APs of different instantaneous frequencies. Action potentials of high instantaneous frequency in branching lengths of axon within ganglia were delayed more significantly than those in non-branching lengths contained within the connective and fail preferentially in branching axon. I found that octopamine attenuates the effects of hypoxia on AP propagation for the branching length of axon but has no effect on the non-branching length of axon. Additionally, for energetically stable cells, application of the anti-diabetic medication metformin or the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel blocker ZD7288 resulted in a reduced performance similar to that seen in neurons experiencing energetic stress. Furthermore both metformin and ZD7288 affect the shape of individual APs within an AP train as well as the original temporal sequence of the AP train, which encodes behaviourally relevant information. I propose that the reduced performance observed in an energetically compromised cell represents an adaptive mechanism employed by neurons in order to maintain the integrity of their highly heterogeneous and complex organization during periods of reduced energy supply. / Thesis (Master, Biology) -- Queen's University, 2011-10-07 14:41:46.972

L'AMPK est un senseur cellulaire des réserves énergétiques de l’organisme. Les spermatozoïdes, mobilisent beaucoup d’énergie pour leur mobilité et la fécondation de l’ovocyte. L’objectif de ce travail était de caractériser et décrire des éléments clés de la voie de signalisation de l'AMPK, de comprendre leur implication dans les spermatozoïdes de coq et d’étudier comment leurs modulateurs peuvent impacter les fonctions des gamètes conservés in vitro. Nous avons montré une augmentation de la mobilité et de la réaction acrosomique dans les spermatozoïdes exposés à l'AICAR et à la metformine, des activateur de l’AMPK, y compris après avoir été congelés. Ces activateurs ont partiellement restauré les activités des enzymes antioxydantes (SOD, GPx, GR): et diminué les ROS et la LPO dans les spermatozoïdes décongelés. Nous avons établi la présence des CaMKKs (α et β) et de CaMKI dans les spermatozoïdes et leur rôle lié au calcium extracellulaire (via les canaux calcique SOCs) dans la voie de régulation de l'AMPK et dans la mobilité et la réaction acrosomique des spermatozoïdes. En conclusion, ce travail confirme le rôle de différents acteurs de signalisation liés au métabolisme énergétique et aux flux calciques dans les fonctions des spermatozoïdes. / AMPK is a cellular sensor of body energy reserves. Spermatozoa mobilize a lot of energy for their motility and the fertilization of the oocyte. The objective of this work was to characterize and describe key elements of the signaling pathway of AMPK, understand their involvement in chicken spermatozoa and study how their modulators may impact the functions of in vitro preserved gametes. We showed an increase in mobility and acrosome reaction in spermatozoa exposed to AICAR and metformin, activators of AMPK, including after freezing. These activators have partially restored the activities of antioxidant enzymes (SOD, GPx, GR): and decreased ROS and LPO in thawed spermatozoa. We have established the presence of CaMKKs (α and β) and CaMKI in sperm and their role related to extracellular calcium (via calcium channels SOCs) in the control channel of AMPK and in motility and acrosome reaction of spermatozoa. In conclusion, this work confirms the role of different signaling actors related to energy metabolism and calcium fluxes in spermatozoa functions.