Lee Wing Sum. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 206-226). / Abstracts in English and Chinese. / Abstract --- p.i / Abstract (Chinese Version) --- p.iv / Acknowledgements --- p.vii / Table of Contents --- p.viii / List of Abbreviations --- p.xiv / List of Figures --- p.xvii / List of Tables --- p.xxiv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Literature review --- p.3 / Chapter 2.1 --- Peroxisomes --- p.3 / Chapter 2.2 --- Peroxisome proliferators --- p.5 / Chapter 2.3 --- Human exposure pathways to peroxisome proliferators --- p.5 / Chapter 2.4 --- Peroxisome proliferator-induced pleiotropic effects in rodents --- p.7 / Chapter 2.4.1 --- Short-term effects --- p.7 / Chapter 2.4.1.1 --- Hepatomegaly --- p.7 / Chapter 2.4.2.1 --- Peroxisome proliferation --- p.8 / Chapter 2.4.1.3 --- Alteration of gene transcriptions --- p.8 / Chapter 2.4.2 --- Long-term effect --- p.9 / Chapter 2.5 --- Mechanisms of actions of peroxisome proliferators --- p.9 / Chapter 2.5.1 --- Substrate overload --- p.9 / Chapter 2.5.2 --- Receptor-mediated --- p.11 / Chapter 2.6 --- Peroxisome proliferator-activated receptors (PPARs) --- p.11 / Chapter 2.6.1 --- Structure of PPARs --- p.11 / Chapter 2.6.2 --- Tissue-specific expression of PPARs --- p.15 / Chapter 2.6.3 --- Physiological functions of PPARs --- p.19 / Chapter 2.6.3.1 --- PPARα --- p.19 / Chapter 2.6.3.2 --- PPARγ --- p.21 / Chapter 2.6.3.3 --- PPARδ --- p.23 / Chapter 2.7 --- Role of PPARα involved in peroxisome proliferator-induced pleiotropic responses --- p.24 / Chapter 2.7.1 --- Short-term effects --- p.24 / Chapter 2.7.2 --- Long-term effect --- p.24 / Chapter 2.8 --- Mechanisms of peroxisome proliferator-induced hepatocarcinogenesis --- p.25 / Chapter 2.8.1 --- Oxidative stress --- p.25 / Chapter 2.8.2 --- Suppression of apoptosis --- p.26 / Chapter 2.8.3 --- Increased cell proliferation --- p.27 / Chapter 2.9 --- Species difference to peroxisome proliferator-induced pleiotropic effects --- p.28 / Chapter 2.10 --- Fluorescent differential display (FDD) --- p.32 / Chapter Chapter 3 --- Objectives --- p.35 / Chapter Chapter 4 --- Materials and methods --- p.37 / Chapter 4.1 --- Animals and treatments --- p.37 / Chapter 4.1.1 --- Materials --- p.37 / Chapter 4.1.2 --- Methods --- p.37 / Chapter 4.2 --- Serum triglyceride and cholesterol analyses --- p.39 / Chapter 4.2.1 --- Materials --- p.41 / Chapter 4.2.2 --- Methods --- p.41 / Chapter 4.2.2.1 --- Serum preparation --- p.41 / Chapter 4.2.2.2 --- Triglyceride determination --- p.41 / Chapter 4.2.2.3 --- Cholesterol determination --- p.42 / Chapter 4.3 --- Statistical analysis --- p.42 / Chapter 4.4 --- Tail-genotyping --- p.42 / Chapter 4.4.1 --- Materials --- p.44 / Chapter 4.4.2 --- Methods. --- p.44 / Chapter 4.4.2.1 --- Preparation of genomic tail DNA --- p.44 / Chapter 4.4.2.2 --- PCR reaction --- p.45 / Chapter 4.5 --- Total RNA isolation --- p.45 / Chapter 4.5.1 --- Materials --- p.48 / Chapter 4.5.2 --- Methods --- p.48 / Chapter 4.6 --- DNase I treatment --- p.48 / Chapter 4.6.1 --- Materials --- p.49 / Chapter 4.6.2 --- Methods --- p.49 / Chapter 4.7 --- Reverse transcription of mRNA and fluorescent PCR amplification --- p.50 / Chapter 4.7.1 --- Materials --- p.50 / Chapter 4.7.2 --- Methods --- p.53 / Chapter 4.8 --- Fluorescent differential display (FDD) --- p.53 / Chapter 4.8.1 --- Materials --- p.53 / Chapter 4.8.2 --- Methods --- p.54 / Chapter 4.9 --- Excision of differentially expressed cDNA fragments --- p.54 / Chapter 4.9.1 --- Materials --- p.57 / Chapter 4.9.2 --- Methods --- p.57 / Chapter 4.10 --- Reamplification of differentially expressed fragments --- p.57 / Chapter 4.10.1 --- Materials --- p.60 / Chapter 4.10.2 --- Methods --- p.60 / Chapter 4.11 --- Subcloning of reamplified cDNA fragments --- p.62 / Chapter 4.11.1 --- PCR-TRAP® cloning system --- p.62 / Chapter 4.11.1.1 --- Materials --- p.63 / Chapter 4.11.1.2 --- Methods --- p.63 / Chapter 4.11.2 --- AdvaTage´ёØ PCR cloning system --- p.65 / Chapter 4.11.2.1 --- Materials --- p.65 / Chapter 4.11.2.2 --- Methods --- p.66 / Chapter 4.12 --- Purification of plasmid DNA from recombinant clones --- p.69 / Chapter 4.12.1 --- Materials --- p.69 / Chapter 4.12.2 --- Methods --- p.69 / Chapter 4.13 --- DNA sequencing of differentially expressed cDNA fragments --- p.70 / Chapter 4.13.1 --- CEQ 2000 Dye Terminator Cycle Sequence system --- p.71 / Chapter 4.13.1.1 --- Materials --- p.71 / Chapter 4.13.1.2 --- Methods --- p.71 / Chapter 4.13.2 --- ABI PRISM´ёØ dRhodamine Terminator Cycle Sequencing system --- p.72 / Chapter 4.13.2.1 --- Materials --- p.72 / Chapter 4.13.2.2 --- Methods --- p.72 / Chapter 4.13.3 --- Homology search against computer databases --- p.73 / Chapter 4.14 --- Northern analysis of differentially expressed cDNA fragments --- p.73 / Chapter 4.14.1 --- Formaldehyde gel electrophoresis of total RNA --- p.74 / Chapter 4.14.1.1 --- Materials --- p.74 / Chapter 4.14.1.2 --- Methods --- p.74 / Chapter 4.14.2 --- Preparation of cDNA probes for hybridization --- p.74 / Chapter 4.14.2.1 --- PCR DIG labeling --- p.75 / Chapter 4.14.2.1.1 --- Materials --- p.75 / Chapter 4.14.2.1.2 --- Methods --- p.75 / Chapter 4.14.2.2 --- Random Prime cDNA DIG labeling --- p.75 / Chapter 4.14.2.2.1 --- Materials --- p.75 / Chapter 4.14.2.2.2 --- Methods --- p.76 / Chapter 4.14.3 --- Purification of DNA from agarose gel --- p.77 / Chapter 4.14.3.1 --- Materials --- p.77 / Chapter 4.14.3.2 --- Methods --- p.78 / Chapter 4.14.4 --- Hybridization --- p.78 / Chapter 4.14.4.1 --- Materials --- p.78 / Chapter 4.14.4.2 --- Methods --- p.73 / Chapter 4.14.5 --- Synthesis of mouse GAPDH probe from normalization --- p.80 / Chapter 4.14.5.1 --- Materials --- p.80 / Chapter 4.14.5.2 --- Methods --- p.80 / Chapter Chapter 5 --- Results --- p.82 / Chapter 5.1 --- Liver morphology --- p.82 / Chapter 5.2 --- Liver weight --- p.82 / Chapter 5.3 --- Serum triglyceride and cholesterol levels --- p.88 / Chapter 5.4 --- Confirmation of genotypes --- p.91 / Chapter 5.5 --- DNase I treatment --- p.91 / Chapter 5.6 --- FDD RT-PCR and band excision --- p.98 / Chapter 5.7 --- Reamplification of excised cDNA fragments --- p.111 / Chapter 5.8 --- Subcloning of reamplified cDNA fragments --- p.121 / Chapter 5.9 --- DNA sequencing of subcloned cDNA fragments --- p.124 / Chapter 5.10 --- Confirmation of the differentially expressed cDNA fragments by Northern blot analysis --- p.132 / Chapter 5.11 --- Temporal expression pattern of differentially expressed genes --- p.157 / Chapter 5.12 --- Tissue distribution pattern of differentially expressed genes --- p.171 / Chapter Chapter 6 --- Discussions --- p.183 / Chapter 6.1 --- "Lack of hepatomegaly, hypotriglyceridemia and hepatic nodule formation in PPARα (-/-) mice" --- p.184 / Chapter 6.2 --- "Identification of PPARα-dependent and Wy-14,643 responsive genes" --- p.185 / Chapter 6.3 --- Functional roles of the isolated cDNA fragments --- p.186 / Chapter 6.3.1 --- Fragments B14 and H4 --- p.187 / Chapter 6.3.2 --- Fragment H1 --- p.189 / Chapter 6.3.3 --- Fragment H5 --- p.192 / Chapter 6.3.4 --- Fragment H8 --- p.194 / Chapter 6.4 --- Temporal expression patterns of the isolated cDNA fragments --- p.196 / Chapter 6.5 --- Tissue distribution patterns of the isolated cDNA fragments --- p.197 / Chapter Chapter 7 --- Conclusions --- p.200 / Chapter Chapter 8 --- Future studies --- p.204 / Chapter 8.1 --- Subcloning and characterization of the other differentially expressed genes --- p.204 / Chapter 8.2 --- Overexpression and inhibition expression of specific genes --- p.204 / Chapter 8.3 --- Generating transgenic mice with target disruption of specific gene --- p.205 / References --- p.206

<p>Methylglyoxal (MG) is a reactive glucose metabolite and a known causative factor for hypertension and diabetes. Hydrogen sulfide (H₂S), on the other hand, is a gasotransmitter with multifaceted physiological functions, including anti-oxidant and vasodilatory properties. The present study demonstrates that MG and H₂S can interact with and modulate each other's functions. Upon <i>in vitro</i> incubations, we found that MG and H₂S can directly interact to form three possible MG-H₂S adducts. Furthermore, the endogenous production level of MG or H₂S was significantly reduced in a concentration-dependent manner in rat vascular smooth muscle cells (A-10 cells) treated with NaHS, a H₂S donor, or MG, respectively. Indeed, MG-treated A-10 cells exhibited a concentration-dependent down-regulation of the protein and activity level of cystathionine &gamma;-lyase (CSE), the main H₂S-generating enzyme in the vasculature. Moreover, H₂S can induce the inhibition of MG-generated ROS production in a concentration-dependent manner in A-10 cells. In 6-22 week-old CSE knockout male mice (CSE^-/-), mice with lower levels of vascular H₂S, we observed a significant elevation in MG levels in both plasma and renal extracts. Renal triosephosphates were also significantly increased in the 6-22 week-old CSE^-/- mice. To identify the source of the elevated renal MG levels, we found that the activity of fructose-1,6-bisphosphatase (FBPase), the rate-limiting enzyme in gluconeogenesis, was significantly down-regulated, along with lower levels of its product (fructose-6-phosphate) and higher levels of its substrate (fructose-1,6-bisphosphate) in the kidney of 6-22 week-old CSE^-/- mice. We have also observed lower levels of the gluconeogenic regulator, peroxisome proliferator-activated receptor-&gamma; coactivator (PGC)-1&alpha;, and its down-stream targets, FBPase-1 and -2, phosphoenolpyruvate carboxykinase (PEPCK), and estrogen-related receptor (ERR)&alpha; mRNA expression levels in renal extracts from 6-22 week-old CSE^-/- mice. Likewise, FBPase-1 and -2 mRNA levels were also significantly down-regulated in aorta tissues from 14-16 week-old CSE^-/- mice. Administration of 30 and 50 &#x00B5;M NaHS induced a significant increase in FBPase-1 and PGC-1&alpha; in rat A-10 cells. We have also observed a significant up-regulation of PEPCK and ERR&alpha; mRNA expression levels in 50 &#x00B5;M NaHS-treated A-10 cells, further confirming the involvement of H₂S in regulating the rate of gluconeogenesis and MG formation. Overall, this unique study demonstrates the existence of a negative correlation between MG and H₂S in the vasculature. Further elucidation of this cross-talk phenomenon between MG and H₂S could lead to more elaborate and effective therapeutic regimens to combat metabolic syndrome and its related health complications.</p>

Introduction: Fast and convenience foods are abundant, relatively inexpensive, and accommodating to the fast-paced lifestyle of many Americans. One popular method of cooking used by many fast food establishments is deep-fat frying. Soybean oil is commonly used for frying and is rich in polyunsaturated fatty acids (PUFA) such as linoleic acid (LA). When soybean oil is used for deep-fat frying, LA becomes oxidized (Ox-LA). Endogenous Ox-LA has the capacity to be a ligand to peroxisome proliferator-activated receptor gamma (PPAR¥ã), a nuclear transcription factor that regulates adipocyte maturation. It is not yet known whether or not dietary Ox-LA has the same capacity with respect to PPAR¥ã. Considering the fact that dietary oxidized lipids are abundant in the typical American diet, it is important to know if they regulate weight gain and especially adipose tissue mass. In this study, we investigate the effects of fresh and heated soybean oil on weight gain and adiposity in mice fed isocaloric low fat diets. Methods: Soybean oil was heated on a hot plate, under a hood, at 190¨¬C for three hours. Fresh soybean oil served as the source of unoxidized oil (Unox-oil) and the heated oil served as the source of oxidized oil (Ox-oil). Both the Ox-oil and Unox-oil were incorporated into a low-fat (10% of calories) mouse chow by Research Diets, Inc. (New Brunswick, NJ). Sixteen C57BL/6J mice were divided into two groups and fed low fat diets with Ox-oil (low fat oxidized, LFO) or with Unox-oil (low fat unoxidized, LFU). Another group of 8 mice were pair fed to the LFO group with the Unox-oil containing chow (PLU). Mice in the LFO and LFU groups were fed ad libitum and known amounts of fresh food was added to the cages every three days. Leftover food was weighed. Body weights were measured once a week. After 16 weeks mice were euthanized and epididymal white adipose tissue (EWAT), retroperitoneal white adipose tissue (RWAT), inguinal white adipose tissue (IWAT), and intrascapular brown adipose tissue (IBAT) samples were collected, weighed and stored at -80 degrees Celsius until further analysis. Fat pads were homogenized and cytosolic and nuclear proteins were extracted by standard methods. These extracts were subjected to Western blotting to determine the amount of PPAR¥ã in the cytosol and nuclear compartments of the fat pads. Differences in group means were analyzed by Mann Whitney U test. Comparisons were considered statistically significant at a p-value of < 0.05. Results: Final mean body weights were significantly different when comparing the mice in the LFU group to the pair fed mice (PLU) (mean ¡¾ SD; 29.52 ¡¾ 1.09 grams (g) and 26.85 ¡¾ 1.44 g, respectively; p < 0.05). Mice fed a low fat diet consisting of Ox-oil (LFO) had a final mean body weight of 27.88 ¡¾ 2.03 g. Mice in the LFU group gained significantly more weight on average than did mice in the LFO or PLU groups (mean ¡¾ SD; 8.86 ¡¾ 1.37g, 7.10 ¡¾ 1.47 g, and 5.71 ¡¾ 1.13 g, respectively). Although mean food intakes were not significantly different between any of the three groups, the average food intake was greatest for the LFU mice in comparison to the LFO and the PLU mice (mean ¡¾ SD; 20.65 ¡¾ 0.09 g/week, 18.40 ¡¾ 0.05 g/week, and 18.38 ¡¾ 0.19 g/week, respectively). Feeding efficiency (g of weight gain/g of food consumed) was the highest in the LFU mice compared to the PLU mice (mean ¡¾ SD; 0.031 ¡¾ 0.005 g/g and0.022 ¡¾ 0.004 g/g) and this difference was statistically significant. The LFO mice gained less weight per gram of food consumed than did the LFU mice (mean ¡¾ SD; 0.028 ¡¾ 0.006 g/g). Mean weights of all fat pads in the LFO group were significantly greater than those of the LFU and PLU mice (mean ¡¾ SD; 0.329 ¡¾ 0.109g, 0.199 ¡¾ 0.055g, and 0.219 ¡¾ 0.041 for EWAT, 0.091 ¡¾ 0.039g, 0.050 ¡¾ 0.026g, and 0.051 ¡¾ 0.017 for RWAT, 0.221 ¡¾ 0.065g, 0.135 ¡¾ 0.053g, and 0.144 ¡¾ 0.038 for IWAT, and 0.079 ¡¾ 0.012g, 0.055 ¡¾ 0.013g, and 0.062 ¡¾ 0.011 for IBAT, respectively). PPAR¥ã protein in the cytosol of EWAT fat pads was analyzed and quantified in comparison to the amount of Glyceraldehyde-3-phosphate dehydrogenase (GAPDH; loading control) present. Mean PPAR¥ã /GAPDH ratios for LFU mice was 0.226 ¡¾ 0.082, for LFO mice was 0.264 ¡¾ 0.122, and for PLU mice was 0.234 ¡¾ 0.108. Mean PPAR¥ã:GAPDH ratios were not significantly different between any of the groups. Conclusion: It appears that the consumption of oxidized oil caused a significant decrease in weight gain and food intake (although not significant) and a significant increase in fat pad mass in mice compared to those consuming a diet with unoxidized oil. The lack of difference in the amount of PPAR¥ã among the three groups of mice suggests that the changes in weight gain and fat pad mass among the oxidized oil consuming animals is not mediated through regulation of PPAR¥ã protein. To our knowledge, ours is the first study to report that mice consuming a low fat diet inclusive of dietary oxidized lipids exhibit greater adiposity than do mice consuming a low fat diet consisting of unoxidized lipids.

<p>Methylglyoxal (MG) is a reactive glucose metabolite and a known causative factor for hypertension and diabetes. Hydrogen sulfide (H₂S), on the other hand, is a gasotransmitter with multifaceted physiological functions, including anti-oxidant and vasodilatory properties. The present study demonstrates that MG and H₂S can interact with and modulate each other's functions. Upon <i>in vitro</i> incubations, we found that MG and H₂S can directly interact to form three possible MG-H₂S adducts. Furthermore, the endogenous production level of MG or H₂S was significantly reduced in a concentration-dependent manner in rat vascular smooth muscle cells (A-10 cells) treated with NaHS, a H₂S donor, or MG, respectively. Indeed, MG-treated A-10 cells exhibited a concentration-dependent down-regulation of the protein and activity level of cystathionine &gamma;-lyase (CSE), the main H₂S-generating enzyme in the vasculature. Moreover, H₂S can induce the inhibition of MG-generated ROS production in a concentration-dependent manner in A-10 cells. In 6-22 week-old CSE knockout male mice (CSE^-/-), mice with lower levels of vascular H₂S, we observed a significant elevation in MG levels in both plasma and renal extracts. Renal triosephosphates were also significantly increased in the 6-22 week-old CSE^-/- mice. To identify the source of the elevated renal MG levels, we found that the activity of fructose-1,6-bisphosphatase (FBPase), the rate-limiting enzyme in gluconeogenesis, was significantly down-regulated, along with lower levels of its product (fructose-6-phosphate) and higher levels of its substrate (fructose-1,6-bisphosphate) in the kidney of 6-22 week-old CSE^-/- mice. We have also observed lower levels of the gluconeogenic regulator, peroxisome proliferator-activated receptor-&gamma; coactivator (PGC)-1&alpha;, and its down-stream targets, FBPase-1 and -2, phosphoenolpyruvate carboxykinase (PEPCK), and estrogen-related receptor (ERR)&alpha; mRNA expression levels in renal extracts from 6-22 week-old CSE^-/- mice. Likewise, FBPase-1 and -2 mRNA levels were also significantly down-regulated in aorta tissues from 14-16 week-old CSE^-/- mice. Administration of 30 and 50 &#x00B5;M NaHS induced a significant increase in FBPase-1 and PGC-1&alpha; in rat A-10 cells. We have also observed a significant up-regulation of PEPCK and ERR&alpha; mRNA expression levels in 50 &#x00B5;M NaHS-treated A-10 cells, further confirming the involvement of H₂S in regulating the rate of gluconeogenesis and MG formation. Overall, this unique study demonstrates the existence of a negative correlation between MG and H₂S in the vasculature. Further elucidation of this cross-talk phenomenon between MG and H₂S could lead to more elaborate and effective therapeutic regimens to combat metabolic syndrome and its related health complications.</p>

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.

Ácidos graxos ácidos saturados induzem resistência à insulina, enquanto ácidos graxos poliinsaturados ômega-3 previnem. Camundongos Swiss foram tratados com dieta controle e dietas contendo óleo de peixe a 4% (NFO) e 40% (HFO) ou banha de suínos a 4% (NL) e 40% (HL) por oito semanas. O grupo HFO apresentou menor massa gorda e peso corpóreo em relação ao HL. Nos grupos NFO e HFO, a insulinemia, glicemia basal e aquela durante o teste de tolerância à glicose foi menor em relação ao HL. Apesar de não haver diferenças no conteúdo de triacilgliceróis no músculo esquelético, o grupo HFO apresentou 60% menos triacilgliceróis no fígado que nos grupos NL e HL. O menor consumo de oxigênio associado ao aumento da oxidação parcial do ácido palmítico e da atividade da acil CoA oxidase no fígado dos animais HFO, indicam maior oxidação peroxissomal de AG. Este processo demanda a metabolização de maior número de moléculas de AG, contribuindo para o menor acúmulo de gordura e preservação da tolerância à glicose. / Saturated fatty acids induce insulin resistance, while omega-3 polyunsaturated fatty acids prevent it. Swiss mice were fed on diets containing fish oil at 4% (NFO) and 40% (HFO) or lard at 4% and 40% for eight weeks. The HFO group showed smaller fat mass and body weight compared to HL. In the groups NFO and HFO, basal insulinemia and glycemia and the area under the curve during glucose tolerance test were lower, compared to HL. Despite no differences on skeletal muscle triacylglycerol content, the HFO group had 60% less triacylglycerols in the liver, compared to NL and HL. The lower oxigen consumption associated to the increase in partial oxidation of palmitic acid and activity of acyl CoA oxidase in the liver of the HFO group, indicate increased peroxisomal oxidation of fatty acids. This process demands the metabolization of more fatty acid molecules, contributing to the decresed fat acumulation and preservation of glucose tolerance.

No description available.

Le stress oxydant, les dysfonctions mitochondriaux et les altérations du métabolisme lipidique sont un dénominateur commun des maladies neurodégénératives (MN), comme la sclérose en plaques (SEP). Dans les conditions du stress oxydant, l’excès du cholestérol est éliminé par oxydation, produisant des oxystérols. Chez l'homme, le taux du 7β-hydroxycholestérol (7β-OHC) est souvent trouvé à des taux élevés dans le liquide céphalo-rachidien (LCR) et/ ou le plasma de patients atteints de MN, notamment la SEP.Dans ce contexte, une étude clinique préliminaire sur le LCR et le plasma de patients atteints de SEP RR a été réalisée dans le but de rechercher des biomarqueurs du métabolisme lipidique et du stress oxydant et de déterminer d‘éventuelles corrélations entre le 7β-OHC et les différents mécanismes associés à la pathogenèse de la SEP. Une étude in vitro a été réalisée afin d’évaluer les activités biologiques de trois molécules utilisées dans le traitement de la SEP, le diméthyle fumarate (DMF) et son métabolite le monométhyle fumarate (MMF), et la biotine sur des oligodendrocytes murins 158N, et à déterminer leurs potentialités cytoprotectrices en se focalisant sur leurs capacités à s’opposer à la toxicité du 7β-OHC. Pour cela, des techniques spectrophotométriques, analytiques et de biologies moléculaires ont été utilisées.Nos résultats ont révélé une augmentation du taux de HODE associée à une augmentation du taux plasmatiques d’oxystérols, notamment 7KC et 7β-OHC, ainsi qu’une altération du métabolisme d’acides gras au niveau du LCR et du plasma des patients atteints de SEP. L’étude in vitro a montré que le DMF, le MMF et la biotine présentent des capacités à atténuer les effets délétères du 7β-OHC à savoir; la mort cellulaire par oxiapoptophagie définie par l’association de l’apoptose, l’autophagie et le stress oxydant. De plus, ces molécules corrigent les modifications structurales et le déséquilibre du statut redox caractérisé par une surproduction d’espèces radicalaires d’oxygène, une activité accrue des principales enzymes anti-oxydantes et une amplification de l'oxydation de macromolécules induites par le 7β-OHC. Elles atténuent également les dysfonctionnements mitochondriaux et péroxysomaux, les altérations de l’expression de protéines de myéline ainsi que le désordre du profil lipidique, induits par le 7β-OHC.Notre étude apporte des arguments en faveurs de la capacité du DMF, du MMF et de la biotine, à atténuer les phénomènes majeurs associés à la mort des oligodendrocytes qui pourraient contribuer à la démyélinisation. Ceci renforce l'intérêt porté à ces molécules pour le traitement des maladies neurodégénératives incluant la SEP. / Oxidative stress, mitochondrial dysfunction, and alterations in lipid metabolism are a common denominator of neurodegenerative diseases (MN), such as multiple sclerosis (MS). Under oxidative stress conditions, excess cholesterol is removed by oxidation, producing oxysterols. In humans, the 7β-hydroxycholesterol (7β-OHC) is often found at increased levels in the cerebrospinal fluid (CSF) and/or plasma of patients with MN, including MS.In this context, a preliminary clinical study on CSF and plasma of patients with RR MS was carried out to search for lipid metabolism and oxidative stress biomarkers and to determine the possible correlations between 7β-OHC and the different mechanisms associated with the MS pathogenesis. An in vitro study was conducted to evaluate the biological activities of three molecules used in the treatment of MS, dimethyl fumarate (DMF) and its major metabolite, monomethyl fumarate (MMF), and biotin on 158N murine oligodendrocytes, and to determine their cytoprotective potentialities by focusing on their ability to oppose the toxicity of 7β-OHC. For this, spectrophotometric, analytical and molecular biology techniques were used.Our results have shown an increased level of HODE associated with an enhancement of oxysterol levels in the plasma, notably 7KC and 7β-OHC, as well an alteration in fatty acid metabolism in the CSF and plasma of patients with SEP. The in vitro study revealed that DMF, MMF, and biotin can counteract the deleterious effects of 7β-OHC namely; cell death by oxiapoptophagy defined by the association of apoptosis, autophagy and oxidative stress. Moreover, these molecules correct the structural modifications and the disequilibrium of the redox status characterized by an overproduction of radical oxygen species, an increased activity of the principal antioxidant enzymes and an amplification of the macromolecules oxidation induced by the 7β- OHC. They also attenuate the mitochondrial and peroxisomal dysfunctions, the alterations of myelin protein expression as well as the lipid profile disorder induced by 7β-OHC.Our study provides arguments in favor of the ability of DMF, MMF, and biotin, to attenuate the major events associated with the death of oligodendrocytes which could contribute to demyelination. This reinforces the interest in these molecules for the treatment of neurodegenerative diseases including MS.

Cardiac energy metabolism is the one of the most complex system in the body. To sustain life, but also to respond quickly to any sudden changes (e.g. running, emotional stress), the heart has developed a unique ability and has become a metabolic "omnivore". At physiological conditions, long chain fatty acids (LCFAs) present the major energetic source for the adult myocardium. However, the cardiac energy metabolism may be compromised during pathophysiological states. One of the most dangerous is, undoubtedly, ischaemia-reperfusion injury with its acute form, myocardial infarction. However, the adaptation to chronic hypoxia has been known for decades for its cardioprotective effect against I/R. Changes of cardiac energy metabolism induced by the adaptation have not been fully explored and the system conceals still too many secrets. This thesis has aimed to determine how adaptation to chronic hypoxia affects the cardiac metabolism of the rat LVs in the following set-ups: 1. The effect of chronic normobaric hypoxia (CNH; 3 weeks, 5500m) during a brief I/R protocol in vitro on the protein kinase B/hexokinase (Akt/HK) pathway, including the expression and phosphorylation of Akt, the expression and localization of HK, the expression of mitochondrial creatine kinase (mtCKS), and the level of Bcl-2 family...

Cardiac energy metabolism is the one of the most complex system in the body. To sustain life, but also to respond quickly to any sudden changes (e.g. running, emotional stress), the heart has developed a unique ability and has become a metabolic "omnivore". At physiological conditions, long chain fatty acids (LCFAs) present the major energetic source for the adult myocardium. However, the cardiac energy metabolism may be compromised during pathophysiological states. One of the most dangerous is, undoubtedly, ischaemia-reperfusion injury with its acute form, myocardial infarction. However, the adaptation to chronic hypoxia has been known for decades for its cardioprotective effect against I/R. Changes of cardiac energy metabolism induced by the adaptation have not been fully explored and the system conceals still too many secrets. This thesis has aimed to determine how adaptation to chronic hypoxia affects the cardiac metabolism of the rat LVs in the following set-ups: 1. The effect of chronic normobaric hypoxia (CNH; 3 weeks, 5500m) during a brief I/R protocol in vitro on the protein kinase B/hexokinase (Akt/HK) pathway, including the expression and phosphorylation of Akt, the expression and localization of HK, the expression of mitochondrial creatine kinase (mtCKS), and the level of Bcl-2 family...