This study was conducted to assess the effects of specific oxysterols on the adipogenic differentiation and expression of adipogenic transcripts in C3H10T1/2 mouse stem cells. In the first study, four oxysterols namely; 20S, 22R, 22S and 25 hydroxycholesterol (25-HC) were tested to determine which one best inhibits adipogenesis in C3H10T1/2 mouse stem cells. Adipogenic differentiation was induced using an adipogenic media (DMITro) consisting of dexamethasone (DEX), 3-isobutyl-1-methyl-xanthine (IBMX), insulin and troglitazone (Tro). Inhibition of adipogenesis was assessed by treatment of cells with DMITro+20S, 22R, 22S or 25-HC for six days. Oil red O pictures and gene expression analysis showed that 25-HC was more effective in inhibiting the expression of adipogenic genes compared to the other oxysterols. Further investigation of the mechanisms of action of 25-HC showed that the inhibitory effects of 25-HC on adipogenesis are not mediated by hedgehog signalling. / October 2015

7-Oxysterols constitute the major component (40%) of oxidized low-density lipoprotein (oxLDL). They arise in the body via auto-oxidation of cholesterol and are known to induce endothelial dysfunction, oxidative stress and apoptosis in the vascular wall, prior to development of atherosclerosis. A novel pathway has been described for hepatic inter-conversion of 7-ketocholesterol (7-KC) and 7β -hydroxycholesterol (7β OHC) by the enzyme 11β-hydroxysteroid dehydrogenase type-1 (11β HSD1), better known for metabolizing glucocorticoids. Inhibition of 11βHSD1 is atheroprotective and the potential underlying mechanism for this may involve altered metabolism and actions of glucocorticoids. However, alterations in the metabolism of 7-oxysterols may also play an important role in this atheroprotective effect. The work described here addresses the hypotheses that (i) 7-oxysterols are substrates for murine 11βHSD1; (ii) inhibition of 11β HSD1 may abolish cellular metabolism of 7-oxysterols; (iii) this route of metabolism may modulate the actions of 7-oxysterols and glucocorticoids on murine vascular physiology. Murine 11β HSD1 inter-converted 7-oxysterols (Km=327.6±98ìM, Vmax=0.01±0.001pmol/ìg/min) but the regulation of reaction direction is different from that for glucocorticoids. Predominant dehydrogenation of 7β OHC to 7-KC was quantified in several models (recombinant protein, cultured cells stably transfected with 11β HSD1), in which predominant reduction of glucocorticoids was measured. Furthermore, in murine hepatic microsomes, dehydrogenation of 7β OHC occurred exclusively. In aortic rings in culture, however, both reduction and dehydrogenation of 7-oxysterols were evident. 7-Oxysterols and glucocorticoid substrates competed for metabolism by 11β HSD1, with 7β OHC inhibiting dehydrogenation of glucocorticoids (Ki=908±53nM). The circulating concentrations of 7-oxysterols in the plasma of C57Bl6 and 11β HSD1-/- mice were in the ìM range (0.02 – 0.13ìM). The disruption of 11β HSD1 has resulted in increased ratios of 7-KC and 7β OHC over total plasma cholesterol levels (*p<0.05). This finding suggested that 11β HSD1 is involved in metabolizing and determining the plasma levels of 7-KC and 7β OHC. To assess the consequences of these alterations for vascular function, studies were undertaken in aortic rings. Prolonged incubation with 7-oxysterols (20-25 ìM) showed a tendency to attenuate noradrenaline-mediated contractions of C57Bl6 aortae, but had no effect on contractions in response to 5-hydroxytryptamine or KCl. Similarly, endothelium-dependent and -independent relaxations of murine aortae were unaltered after exposure to 7-oxysterols. Thus in the mouse, 11β HSD1 may influence the balance of circulating and cellular 7-oxysterols which may have consequential effects on glucocorticoid action. Although this work suggests that concentrations present in murine tissues are unlikely to cause vascular dysfunction, they may influence further cellular events as yet undescribed. Under pathological conditions where high concentrations of 7-oxysterols occur, 11β HSD1 may influence the extracellular-transport and delivery of 7-KC and 7β OHC to the plaque. This work therefore proposes that inhibition of metabolism of 7-oxysterols by 11β HSD1 inhibitors, may contribute to the atheroprotective effects of these drugs.

No description available.

Pregestational and gestational diabetes (GDM) places the mother and her offspring at an increased risk for later development of insulin resistance and type 2 diabetes. Oxidative stress may mediate long-term disturbances in glucose homeostasis associated with type 2 diabetes and the metabolic syndrome. This thesis describes a cross-sectional study examining serum concentrations of free radical generated oxysterols as markers of oxidative stress in a cohort of teenage daughters from pregnancies with and without GDM. Daughters of GDM-pregnancies had a tendency of higher levels of serum oxysterols (7beta-hydroxycholesterol); however, this difference was not statistically significant after adjustment for total cholesterol. Serum oxysterols were significantly correlated with obesity measures such as waist circumference and BMI, which likely accounted for the tendency for higher measures of oxysterol concentrations in the GDM daughters. Oxysterols represent potentially important biomarkers for oxidative stress in adolescent girls as their levels track with the metabolic syndrome risk factors. / Le diabète pré-gestationnel et le diabète de gestation (DG) augmentent le risque dedéveloppement d'une future résistance à l'insuline et de diabète de type 2 autant pourla mère que pour l'enfant. Le stress oxydatif est un facteur potentiel impliqué dans ledéséquilibre du glucose sanguin associé au diabète de type 2 et au syndromemétabolique. La présente thèse est une étude sectionnelle croisée, ayant pour but demesurer des marqueurs du stress oxidatif, notamment la concentration des oxystérolsgénérés par les radicaux libres dans le sérum d'adolescentes, nées de mères ayantprésenté ou non un diabète de gestation. Nos résultats montrent des concentrationsd'oxystérols (7P-hydroxycholesterol) plus élevées dans le sérum de filles issues degestations diabétiques à comparer aux filles de mères n'ayant pas eu de DG.Cependant, la différence entre les deux groupes n'était pas statistiquementsignificative après un ajustement au cholestérol total. La concentration d'oxystérolsétait significativement corrélée aux marqueurs d'obésité, notamment la circonférencede la taille et l'index de masse corporelle, possiblement à l'origine de la tendance desoxystérols à être plus élevés dans le cas des adolescentes issues de gestationsdiabétiques.

Omega-3 polyunsaturated fatty acids can reduce the risk of cardiovascular disease and cancers. Enriching broiler meat opportunities lack research on product quality. The fatty acid (FA) profile of birds fed flaxseed for various periods was analyzed. Another experiment assessed FA profile and oxidation products in frozen-raw and cooked thigh meat in birds fed 20% linPRO (50% extruded flaxseed) with antioxidant combinations. Males deposited more omega-3 in breast meat than females. It required 26.2 d (10%flax) or 11.3 d (17%flax) feeding to achieve the 300 mg omega-3/100g of breast. Eicosapentaenoic and docosahexaenoic acids were deposited in the phospholipids whereas a-linolenic acid associated with triacylglycerols. Oxysterol appearance was reduced in thighs of high vitamin E birds while the high selenium treatment had no effect or even raised oxysterols during roasting. Antioxidants inhibited thiobarbuturic reactive acid substances in stored frozen-raw meat. Stability of omega-3 broiler meat was improved with increased dietary antioxidant levels. / Food Science and Technology

No description available.

No description available.

Hormonal therapy is a common part of breast carcinoma treatment in patients whose tumors express estrogen and progesterone receptors. The aim of hormonal therapy is to prevent proliferative effect of hormones througt their receptor proteins in order to inhibit tumor growth. However, certain number of tumors is resistant to hormonal therapy despite expression of hormonal receptors. Presently, the reasons of this resistance are not fully understood. Oxysterols are hydroxylated cholesterol derivates, which may play some role in development of the resistance. They may interfere with hormonal therapy effect and influence some signal pathways leading to cancer progression. This study comes with results of gene expression of proteins influenced by oxysterol action, metabolic and transport proteins, transcription factors and members of signaling pathways that may be related to oxysterol effect. This thesis identifies some candidate genes for future analysis on the basis of comparison of gene expression between estrogen receptor positive and negative tumors and correlation with clinopathological data. The final goal should lead to discovery of new diagnostic markers for breast cancer therapy. Powered by TCPDF (www.tcpdf.org)

L'athérosclérose est une complication cardiovasculaire majeure des maladies liées à une augmentation du stress oxydatif, comme le diabète de type 2 et le syndrome métabolique. Dans ces situations, les lipoprotéines de faible densité (LDL) subissent une oxydation et leur forte absorption induit une accumulation de cholestérol dans les macrophages sous-endothéliaux. D'autre part, les LDL oxydées sont enrichies en produits d'oxydation du cholestérol appelés oxystérols, dont certains sont impliqués dans la capacité des LDL oxydées à induire un stress oxydant cellulaire et une cytotoxicité, principalement par apoptose. Le Bis(Monoacylglycéro)Phosphate (BMP) est un phospholipide unique, localisé préférentiellement dans les endosomes tardifs, compartiment cellulaire clef dans le métabolisme du cholestérol dérivé des LDL. Lors de travaux antérieurs, l'équipe a démontré le rôle prépondérant du BMP dans la régulation de l'homéostasie du cholestérol dans les macrophages. L'objectif de ce travail a été de décrypter les mécanismes moléculaires intervenant dans le trafic intracellulaire du cholestérol. Ainsi, le BMP régule l'efflux de cholestérol par les HDL (high density lipoproteins) grâce à des mécanismes impliquant les LXRs (liver X receptors) et les transporteurs ABCA1/ABCG1 (ATP binding cassette-type A1/G1). De plus, notre étude indique que le BMP exerce également un rôle protecteur contre l'effet pro-apoptotique des LDL oxydées via la réduction de la production intracellulaire d'oxystérols. Comme une partie du trafic intracellulaire des stérols au sein des macrophages est régulé par OSBP (oxysterol binding protein) et ses protéines dérivées, les ORPs (OSBP-related proteins), nous montrons dans ce rapport que l'action de protection du BMP contre les effets cytotoxiques des oxystérols est fortement diminuée dans des cellules où la protéine ORP11 est supprimée, suggérant que le BMP exerce son rôle protecteur via un mécanisme utilisant la fonction d'ORP11 dans le transport intracellulaire de stérols / Atherosclerosis is a major cardiovascular complication in increased oxidative stress-related diseases such as type 2 diabetes and metabolic syndrome. In these situations, the low density lipoproteins (LDL) undergo oxidation and their high uptake induces cholesterol accumulation in subendothelial macrophages. On the other hand, oxidized LDL are enriched in cholesterol oxidation products called oxysterols, some of them are involved in the ability of oxidized LDL to induce cellular oxidative stress and cytotoxicity, mainly by apoptosis. Bis(Monoacylglycero)Phosphate (BMP) is a unique phospholipid localized preferentially in late endosomes, a central cellular compartment of LDL-cholesterol metabolism. In previous work, the team demonstrated the leading role of BMP in regulation of cholesterol homeostasis in macrophages. The aim of this work was to characterize the molecular mechanisms involved in the intracellular trafficking of cholesterol. Thus, BMP regulates cholesterol efflux to HDL (high density lipoproteins) by mechanisms involving liver X receptors (LXRs) and ABCA1/ABCG1 (ATP binding cassette-type A1/G1) transporters. Moreover, we report BMP also exerts a protective role against the pro-apoptotic effect of oxidized LDL via a reduced production of intracellular pro-apoptotic oxysterols.As part of macrophage intracellular sterol traffic is regulated by oxysterol binding protein (OSBP) and OSBP-related proteins (ORPs), we show that protective action of BMP against cytotoxic oxysterol effects in ORP11-silenced cells, was markedly abrogated, suggesting BMP exerts its protective role via a mechanism involving the function of ORP11 in intracellular sterol transport

O estresse oxidativo pode desempenhar um papel importante na etiologia das complicações no diabetes mellitus. O aumento da produção de espécies oxidantes promove modificações em moléculas endógenas, incluindo o colesterol. Os óxidos de colesterol (Cox) são formados a partir da oxidação do colesterol, por processos enzimáticos e por processos mediados por radicais livres, apresentando importantes efeitos biológicos que podem contribuir para o desenvolvimento do processo aterosclerótico no diabetes. Nesse estudo determinou-se as concentrações dos Cox, em pacientes diabéticos e indivíduos intolerantes à glicose, para estabelecer se os COx são marcadores sensíveis da lipoperoxidação na intolerância à glicose e no diabetes As concentrações plasmáticas dos COx foram determinadas por GC-FID nos seguintes grupos: diabéticos tipo 1 (DM1), diabéticos tipo 2 (DM2), intolerantes à glicose (IGT) e normoglicêmicos (controles). As concentrações dos óxidos de colesterol totais foram mais elevadas nos grupos DM1 e DM2 em relação aos controles normoglicêmicos (p<0,05). As concentrações plasmáticas do 7&#945;- hidroxicolesterol (7&#945;-OH), 7&#946;-hidroxicolesterol (7&#946;-OH) e 25- hidroxicolesterol (25-OH) foram mais elevadas no grupo DM1 comparado ao grupo DM2 (p<0.05). A comparação entre os grupos controle, IGT e DM 2 indicou aumento significativo das concentrações de 7&#946;-OH, colesterol-&#946;- epóxido e colesterol-&#945;-epóxido no grupo DM 2 (p<0.05). Portanto, os óxidos de colesterol podem ser considerados como um biomarcador sensível da lipoperoxidação para indicar a intensidade de modificação oxidativa dos lípides em pacientes diabéticos. / Oxidative stress can play an important role in the etiology of the complications of diabetes mellitus. The increase in the production of oxidant species promotes alterations in endogenous molecules, including cholesterol. Cholesterol oxides (COx) are formed by the oxidation of cholesterol by enzymatic processes or by processes involving free radicals. They present important biological effects that can contribute to the development of the atherosclerotic process in diabetes. In this study, the concentrations of the COx in diabetic patients and individuals who are intolerant to glucose was determined in order to establish whether the Cox are sensitive markers of lipoperoxidation in glucose intolerance and diabetes. Serum concentrations of the COx were determined by GC-FID in the following groups: Type 1 diabetics (DM1), type 2 diabetics (DM2), patients intolerant to glucose (IGT) and normoglycemic subjects (controls). The concentrations of total cholesterol oxides were found to be elevated in the DM1 and DM2 groups with respect to the normoglycemic subjects (p<0.05). The serum concentrations of 7&#9465- hydroxicholesterol (7&#945;-OH), 7&#946;-hydroxicholesterol (7&#$946;-OH) and 25-hydroxicholesterol (25-OH) were found to be increased in the DM1 group with respect to the DM2 group (p<0.05). The comparison between the control, IGT and DM2 groups indicated a significant increase in the concentrations of 7&#946;-OH, cholesterol-&#946;-epoxide and cholesterol-&#945;-epoxide in the DM2 group (p<0.05). In conclusion, cholesterol oxides could serve as suitable biomarker of lipoperoxidation to indicate the intensity of lipid oxidative mofications in diabetic patients.