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‣ Cholesterol oxides inhibit cholesterol esterification by lecithin: cholesterol acyl transferase

PINCINATO, Eder de Carvalho; MORIEL, Patricia; ABDALLA, Dulcinéia Saes Parra
Fonte: Universidade de São Paulo, Faculdade de Ciências Farmacêuticas Publicador: Universidade de São Paulo, Faculdade de Ciências Farmacêuticas
Tipo: Artigo de Revista Científica
Português
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36.76033%
Cholesterol oxides are atherogenic and can affect the activity of diverse important enzymes for the lipidic metabolism. The effect of 7β-hydroxycholesterol, 7-ketocholesterol, 25-hydroxycholesterol, cholestan-3β,5α,6β-triol,5,6β-epoxycholesterol, 5,6α-epoxycholesterol and 7α-hydroxycholesterol on esterification of cholesterol by lecithin:cholesterol acyl transferase (LCAT, EC 2.3.1.43) and the transfer of esters of cholesterol oxides from high density lipoprotein (HDL) to low density lipoproteins (LDL) and very low density lipoproteins (VLDL) by cholesteryl ester transfer protein (CETP) was investigated. HDL enriched with increasing concentrations of cholesterol oxides was incubated with fresh plasma as source of LCAT. Cholesterol and cholesterol oxides esterification was followed by measuring the consumption of respective free sterol and oxysterols. Measurements of cholesterol and cholesterol oxides were done by gas-chromatography. 14C-cholesterol oxides were incorporated into HDL2 and HDL3 subfractions and then incubated with fresh plasma containing LCAT and CETP. The transfer of cholesterol oxide esters was followed by measuring the 14C-cholesterol oxide-derived esters transferred to LDL and VLDL. All the cholesterol oxides studied were esterified by LCAT after incorporation into HDL particles...

‣ Efeito Hipocolesterolemizante da Proteína de Amaranto (Amaranthus cruentus BRS-Alegria) em Hamsters ; Cholesterol-lowering effect of amaranth protein (Amaranthus cruentus L. BRS-Alegria) in hamsters.

Mendonça, Simone
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 09/03/2006 Português
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Objetivo. Amaranto é considerado um alimento funcional devido às suas propriedades de redução de colesterol plasmático. Um possível componente do amaranto responsável por este efeito é a proteína.Métodos. Neste estudo, foi produzido isolado protéico de amaranto através da solubilização da proteína em pH 11 e precipitação em pH 5,7, obtendo-se o isolado com pureza de 96% de proteína. Este isolado protéico foi utilizado como fonte de proteínas em dietas experimentais para hamsters que tiveram hipercolesterolemia induzida, previamente, por dieta contendo 30% de caseína e 0,05% de colesterol, durante 3 semanas. Os animais foram, então, distribuídos em três grupos (n=11 animais/grupo) e foram alimentados com dietas contendo: (A) 20% caseína (controle), (B) 20% proteína de amaranto purificada (grupo substituição) e (C) 20% caseína + 10% proteína de amaranto purificada (grupo suplementação). Resultados. Comparando-se com a dieta controle, o grupo da suplementação e o da substituição tiveram dramáticas reduções do nível de colesterol plasmático, 30% (p<0,05) e 51% (p<0,05) respectivamente, enquanto o controle apresentou redução de apenas 7% após os 28 dias de dieta. Já na primeira semana este comportamento de redução para as duas dietas contendo amaranto foi percebido...

‣ Albumina modificada por glicação avançada no diabete melito tipo 1 e 2 prejudica o transporte reverso de colesterol e favorece o acúmulo de lípides em macrófagos; Impairment in reverse cholesterol transport and macrophage lipid accumulation induced by advanced glycated albumin drawn from uncontrolled type 1 and type 2 diabetes mellitus patients

Lima, Adriana Machado Saldiba de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 24/02/2011 Português
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Produtos de glicação avançada (AGE) são prevalentes no diabete melito e alteram o metabolismo de lípides e lipoproteínas. Neste estudo, avaliou-se a influência da albumina, isolada do soro de indivíduos controles (C, n =12) e de portadores de diabete melito tipo 1 (DM 1, n=13) e tipo 2 (DM 2, n=11), com controle glicêmico inadequado, sobre a remoção de colesterol de macrófagos, o acúmulo intracelular de lípides, o conteúdo do receptor de HDL, ABCA-1 e a captação seletiva de colesterol esterificado de HDL. Além disso, foi determinada a expressão diferencial de genes em macrófagos tratados com albumina C, DM 1 ou DM 2. A concentração plasmática de albumina glicada foi superior no grupo DM 1 e DM 2 em relação ao C e correlacionou-se positivamente com glicemia, hemoglobina glicada e frutosamina. Albumina sérica foi isolada por cromatografia para separação rápida de proteínas e purificada por extração alcoólica. Albumina DM 1 e DM 2 apresentaram maior conteúdo de carboximetil-lisina e apo A-I quando comparada à albumina C. Macrófagos enriquecidos com LDL acetilada e 14C-colesterol foram tratados com albumina C, DM 1 ou DM 2 e, a seguir, incubados na presença ou ausência de apo A-I, HDL3 ou HDL2 para determinação do efluxo de colesterol. Apesar de removerem maior quantidade de colesterol celular...

‣ High cholesterol intake modifies chylomicron metabolism in normolipidemic young men

César, Thais B.; Oliveira, Maria Rita M.; Mesquita, Carlos H.; Maranhão, Raul C.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 971-976
Português
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Whether the consumption of egg yolk, which has a very high cholesterol content without excess saturated fats, has deleterious effects on lipid metabolism is controversial. Absorbed dietary cholesterol enters the bloodstream as chylomicrons, but the effects of regular consumption of large amounts of cholesterol on the metabolism of this lipoprotein have not been explored even though the accumulation of chylomicron remnants is associated with coronary artery disease (CAD). We investigated the effects of high dietary cholesterol on chylomicron metabolism in normolipidemic, healthy young men. The plasma kinetics of a chylomicron-like emulsion, doubly-labeled with 14C-cholesteryl ester ( 14C-CE) and 3H-triolein ( 3H-TG) were assessed in 25 men (17-22 y old, BMI 24.1 ± 3.4 kg/m 2). One group (n = 13) consumed 174 ± 41 mg cholesterol/d and no egg yolk. The other group (n = 12) consumed 3 whole eggs/d for a total cholesterol intake of 804 ± 40 mg/d. The nutritional composition of diets was the same for both groups, including total lipids and saturated fat, which comprised 25 and 7%, respectively, of energy intake. Serum LDL and HDL cholesterol and apoprotein B concentrations were higher in the group consuming the high-cholesterol diet (P < 0.05)...

‣ Oxidos de coleterol, colesterol, lipidios totais e acidos graxos em produtos caneos processados.; Oxides of cholesterol, total and acid cholesterol, greasy lipídios in processed cárneos products.

Sueli Regina Baggio
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 26/07/2004 Português
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Produtos cárneos processados como lingüiça, salsicha, mortadela, presunto e salame são muito apreciados pela população, mas, em geral, são considerados alimentos que apresentam altos teores de colesterol, lipídios totais e ácidos graxos saturados. O alto teor de colesterol sangüíneo é uma das causas das doenças cardíacas coronarianas e o colesterol sangüíneo é influenciado não só pelo teor de colesterol dos alimentos como também pela quantidade de ácidos graxos saturados. Além disso, o colesterol é um lipídio insaturado susceptível à oxidação, levando à formação de vários produtos de oxidação, os quais são considerados mais prejudiciais que o próprio colesterol na formação de placas ateroscleróticas e estão associados a vários efeitos biológicos indesejáveis. Os ácidos graxos trans também estão relacionados com o desenvolvimento de ateroscleroses e doenças cardiovasculares, são mais preocupantes que os ácidos graxos saturados porque além de aumentarem o nível de lipoproteínas de baixa densidade (LDL), diminuem o nível de lipoproteínas de alta densidade (HDL). Assim, o presente trabalho teve por objetivo determinar os teores de óxidos de colesterol, colesterol, lipídios totais e composição de ácidos graxos em produtos cárneos processados e verificar o efeito do preparo térmico e do armazenamento sobre estes componentes. Foram analisados produtos processados de carne de peru (salsicha...

‣ Efeito do processamento termico e tempo de estocagem na formação de oxidos de colesterol e na alteração da composição de acidos graxos em ovos.; The effect of heat treatment and storage time in the formation of cholesterol oxides and alteration of the fatty acids composition in eggs.

Monica Roberta Mazalli
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 21/02/2006 Português
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Um novo método foi desenvolvido para determinação simultânea de colesterol e óxidos de colesterol em ovos, utilizando cromatografia líquida de alta eficiência (CLAE) com detectores ultra violeta (UV) e índice de refração (IR). A quantificação foi realizada por padronização externa e a confirmação do colesterol e dos óxidos de colesterol foi feita com cromatógrafo líquido com interface de ionização química à pressão atmosférica e espectro de massas (APCI-MS). Através de planejamentos fatoriais completos com pontos centrais foram definidas as melhores condições de saponificação das amostras e extração da matéria insaponificável. Nas condições cromatográficas utilizadas, foram separados o colesterol e os seguintes óxidos: 19-hidroxicolesterol (19- OH), 20a-hidroxicolesterol (20a-OH), 22(R)-hidroxicolesterol (22(R)-OH), 24(S)-hidroxicolesterol (24(S)-OH), 22(S)-hidroxicolesterol (22(S)-OH), 25-OH, 7-ceto, 7b-OH, 7a-OH, 5,6a-epoxi, 5,6b-epoxi e triol. O método proposto mostrou ter alta sensibilidade e precisão, com recuperações de colesterol variando de 92 a 102% e dos óxidos de colesterol de 93 a 96%. Os LD encontrados para os óxidos de colesterol variaram de 0,002 a 0,079 mg/g e para o colesterol o LD foi de 0...

‣ Dietary raw peas (Pisum sativum L.) reduce plasma total and LDL cholesterol and hepatic esterified cholesterol in intact and ileo-rectal anastomosed pigs fed cholesterol-rich diets

Martins, J.M.; Riottot, M.; de Abreu, M.C.; Lança, M.J.; Viegas-Crespo, A.M.; Almeida, J.A.; Freire, J.B.; Bento, O.
Fonte: American Society for Nutritional Sciences Publicador: American Society for Nutritional Sciences
Tipo: Artigo de Revista Científica
Português
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ABSTRACT Although the cholesterol-lowering effect of some dietary legumes is well established from animal and human studies, the mechanism by which they exert this effect is not completely understood. The present study was undertaken to investigate the effect of raw pea seeds on cholesterol metabolism and steroids output of intact and ileo-rectal anastomosed (IRA) pigs. Twenty-four growing pigs were divided in four groups and allocated to cholesterol-rich semi-purified casein (C) (pigs with and without IRA) and raw pea seeds (RP) diets (pigs with and without IRA). Diet-induced hypercholesterolemia was inhibited by RP diet through a significant decrease in plasma LDL-cholesterol. LDL receptors activity was significantly higher in intact RP-fed pigs. RP diet was also responsible for liver triacylglycerols and free cholesterol increases and liver esterified cholesterol reduction. RP-fed pigs higher gallbladder bile free and total cholesterol were not accompanied by significantly higher fecal and ileal digesta neutral sterols output, but increased bile acids were detected in bile and fecal and ileal digesta of these animals. Meanwhile, no differences were detected between cholesterol 7α-hydroxylase and sterol 27-hydroxylase activities. IRA effects were mainly registered on the inhibition of cholesterol and phytosterols bacterial transformation...

‣ A multicommuted flow procedure for the determination of total and free cholesterol in eggs and human blood serum by chemiluminescence

Leite,Oldair D; Vieira,Heberth J; Fatibello-Filho,Orlando; Rocha,Fábio R. P
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 Português
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A multicommuted flow-based procedure with detection by chemiluminescence for the determination of total and free cholesterol without changes in the flow manifold is proposed. Cholesterol esterase and cholesterol oxidase were both immobilized on glass beads via glutaraldehyde/(3-aminopropyl)-triethoxysilane and mini-columns containing the enzymes were used for online sample treatment. Cholesterol esters were cleaved to cholesterol and fatty acids at the packed reactor containing cholesterol esterase. The reactor containing cholesterol oxidase converted cholesterol to cholest-4-en-3-one also yielding hydrogen peroxide. Detection was based on the chemiluminescence produced by H2O2 in the hexacyanoferrate(III)-luminol system. Influence of both chemical and hydrodynamic variables on the chemiluminescence signals were investigated. The analytical curves were linear from 250 to 2500 mg L-1 and from 500 to 4000 mg L-1, for free and total cholesterol, respectively. Detection limits for both analytes were estimated as 60 mg L-1 at 99.7% confidence level. The sampling rate was 55 h-1 and reagent consumption was 350 µg of luminol and 2.6 mg of potassium hexacyanoferrate(III) per determination. The procedure developed was successfully applied for determination of cholesterol in eggs and in human blood serum with results in agreement with the reference spectrophotometric method at the 95% confidence level.

‣ Cholesterol oxides inhibit cholesterol esterification by lecithin: cholesterol acyl transferase

Pincinato,Eder de Carvalho; Moriel,Patricia; Abdalla,Dulcinéia Saes Parra
Fonte: Universidade de São Paulo, Faculdade de Ciências Farmacêuticas Publicador: Universidade de São Paulo, Faculdade de Ciências Farmacêuticas
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2009 Português
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Cholesterol oxides are atherogenic and can affect the activity of diverse important enzymes for the lipidic metabolism. The effect of 7β-hydroxycholesterol, 7-ketocholesterol, 25-hydroxycholesterol, cholestan-3β,5α,6β-triol,5,6β-epoxycholesterol, 5,6α-epoxycholesterol and 7α-hydroxycholesterol on esterification of cholesterol by lecithin:cholesterol acyl transferase (LCAT, EC 2.3.1.43) and the transfer of esters of cholesterol oxides from high density lipoprotein (HDL) to low density lipoproteins (LDL) and very low density lipoproteins (VLDL) by cholesteryl ester transfer protein (CETP) was investigated. HDL enriched with increasing concentrations of cholesterol oxides was incubated with fresh plasma as source of LCAT. Cholesterol and cholesterol oxides esterification was followed by measuring the consumption of respective free sterol and oxysterols. Measurements of cholesterol and cholesterol oxides were done by gas-chromatography. 14C-cholesterol oxides were incorporated into HDL2 and HDL3 subfractions and then incubated with fresh plasma containing LCAT and CETP. The transfer of cholesterol oxide esters was followed by measuring the 14C-cholesterol oxide-derived esters transferred to LDL and VLDL. All the cholesterol oxides studied were esterified by LCAT after incorporation into HDL particles...

‣ Lack of Cholesterol Awareness among Physicians Who Smoke

Scranton, Richard E.; Farwell, Wildon Randal; Gaziano, John Michael
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Português
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Cigarette use is a known risk factor for the development of coronary artery disease (CAD) as it adversely affects HDL cholesterol levels and promotes thrombogenesis. Smoking may also be associated with behavioral characteristics that potentiate the risk of CAD. A lack of cholesterol knowledge would indicate an aversion to a prevention-oriented lifestyle. Thus, our goal was to determine the association between tobacco use and knowledge of self-reported cholesterol among male physicians. Using the 1982 and follow-up questionnaires from the physician health study, we report the changes in the frequencies of awareness of self-reported total cholesterol and cardiovascular risk factors among the 22,067 participants. We classified physicians as being aware of their cholesterol if they reported a cholesterol level and unaware if the question was left unanswered. In 1997, 207 physicians were excluded, as the recorded cholesterol was not interpretable, leaving 21,860 for our follow up analyses. Using unadjusted logistic models, we determined the odds ratios (OR) and 95% confidence intervals (CI) of not reporting a cholesterol level in either 1982 or 1997 for each specified risk factor. We then evaluated whether the lack of cholesterol awareness at both time points was associated with the use of tobacco throughout the study. After 14-years of follow up...

‣ Awareness, Accuracy, and Predictive Validity of Self-reported Cholesterol in Women

Huang, Peng-yun A.; Buring, Julie Elizabeth; Ridker, Paul M.; Glynn, Robert J.
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
Português
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Background: Although current guidelines emphasize the importance of cholesterol knowledge, little is known about accuracy of this knowledge, factors affecting accuracy, and the relationship of self-reported cholesterol with cardiovascular disease (CVD). Methods: The 39,876 female health professionals with no prior CVD in the Women’s Health Study were asked to provide self-reported and measured levels of total and high-density lipoprotein (HDL) cholesterol. Demographic and cardiovascular risk factors were considered as determinants of awareness and accuracy. Accuracy was evaluated by the difference between reported and measured cholesterol. In addition, we examined the relationship of self-reported cholesterol with incident CVD over 10 years. Results: Compared with women who were unaware of their cholesterol levels, aware women (84%) had higher levels of income, education, and exercise and were more likely to be married, normal in weight, treated for hypertension and hypercholesterolemia, nonsmokers, moderate drinkers, and users of hormone therapy. Women underestimated their total cholesterol by 9.7 mg/dL (95% CI: 9.2–10.2); covariates explained little of this difference (R(^2) < .01). Higher levels of self-reported cholesterol were strongly associated with increased risk of CVD...

‣ Les transporteurs sélectifs de cholestérol SR-BI, SR-BII, CD36 et ABCA1 contribuent au maintien de l’homéostasie du cholestérol intratesticulaire

Akpovi, D. Casimir
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
Português
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Le testicule assure la production des spermatozoïdes et la sécrétion de la testostérone. Chaque fonction est assumée par un compartiment cellulaire distinct: l’épithélium séminifère et le tissu interstitiel. Le cholestérol, présent dans les deux compartiments, est un composé indispensable aux membranes cellulaires et un précurseur essentiel de la testostérone. Dans le compartiment interstitiel, environ 40 % du cholestérol utilisé pour la production hormonale est importé du sang à partir des lipoprotéines HDL et/ou LDL. Dans l’épithélium séminifère, la cellule de Sertoli assure le contrôle et le maintien de la spermatogenèse. Elle a la capacité de synthétiser du cholestérol à partir de l’acétate in vitro, néanmoins, il n’y a pas d’évidence qu’elle le fait in vivo. De plus il existe, au niveau des tubules séminifères, une barrière hémato-testiculaire qui empêche le libre passage de plusieurs composés sanguins, y compris le cholestérol. Nous avons testé l’hypothèse qu’il existe des moyens d’importation du cholestérol sanguin, mais aussi l’exportation du cholestérol intra-tissulaire, qui contourneraient cette barrière et qui contribueraient au maintien du taux intratubulaire du cholestérol compatible avec le bon déroulement de la spermatogenèse. Nous avons comparé les taux de variation de l’expression de l’ARNm et de la protéine des transporteurs sélectifs de cholestérol SR-BI...

‣ Le rôle de la dysrégulation du métabolisme du cholestérol par le retrait des estrogènes sur la stéatose hépatique

Côté, Isabelle
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
Português
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36.729407%
Les estrogènes confèrent aux femmes une protection cardiovasculaire jusqu’à la ménopause. En effet, la perte des fonctions ovariennes engendre plusieurs désordres du profil lipidique qui s’accompagnent d’une accumulation de triglycérides au foie appelée stéatose hépatique. Le retrait des estrogènes perturbe de nombreuses voies de contrôle de la cholestérolémie, provoquant simultanément une hypercholestérolémie et une stéatose hépatiques. Toutefois, à ce jour, les mécanismes d’action du retrait des estrogènes sur le métabolisme du cholestérol favorisant le stockage de triglycérides au foie demeurent imprécis. À cet égard, les travaux de cette thèse visaient à clarifier l’ensemble des effets du retrait des estrogènes sur le métabolisme du cholestérol pouvant mener à la pathogenèse de la stéatose hépatique. Lors de la première étude, l’ovariectomie (Ovx) chez la rate, un modèle bien établi de la stéatose, avait permis d’identifier la voie d’assemblage des lipoprotéines à très faible densité (VLDL) comme élément contributif à la stéatose. La voie des VLDL reliant étant également une voie de transport du cholestérol, l’étude suivante a été réalisée afin de comprendre le rôle du cholestérol alimentaire sur les lipides hépatiques. Dans cette deuxième étude...

‣ Restricted fetal growth and the response to dietary cholesterol in the guinea pig

Kind, K.; Clifton, P.; Katsman, A.; Tsiounis, M.; Robinson, J.; Owens, J.
Fonte: AMER PHYSIOLOGICAL SOC Publicador: AMER PHYSIOLOGICAL SOC
Tipo: Artigo de Revista Científica
Publicado em //1999 Português
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Epidemiological studies suggest that retarded growth before birth is associated with increased plasma total and low-density lipoprotein (LDL) cholesterol concentrations in adult life. Thus perturbations of prenatal growth may permanently alter cholesterol metabolism. To determine directly whether restriction of prenatal nutrition and growth alters postnatal cholesterol homeostasis, the plasma cholesterol response to cholesterol feeding (0.25% cholesterol) was examined in adult guinea pig offspring of ad libitum-fed or moderately undernourished mothers. Maternal undernutrition (85% ad libitum intake throughout pregnancy) reduced birth weight (-13%). Plasma total cholesterol was higher prior to and following 6 wk cholesterol feeding in male offspring of undernourished mothers compared with male offspring of ad libitum-fed mothers (P < 0.05). The influence of birth weight on cholesterol metabolism was examined by dividing the offspring into those whose birth weight was above (high) or below (low) the median birth weight. Plasma total cholesterol concentrations prior to cholesterol feeding did not differ with size at birth, but plasma total and LDL cholesterol were 31 and 34% higher, respectively, following cholesterol feeding in low- compared with high-birth weight males (P < 0.02). The response to cholesterol feeding in female offspring was not altered by variable maternal nutrition or size at birth. Covariate analysis showed that the effect of maternal undernutrition on adult cholesterol metabolism could be partly accounted for by alterations in prenatal growth. In conclusion...

‣ Rapid screening for potential cholesterol-lowering peptides using naturally derived micelle preparation

Kirana, Chandra; Rogers, P. F.; Bennett, Louise E.; Abeywardena, Mahinda Y.; Patten, Glen Stephen
Fonte: Australian Society of Dairy Technology Publicador: Australian Society of Dairy Technology
Tipo: Artigo de Revista Científica
Publicado em //2005 Português
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Several food constituents have been shown to reduce blood cholesterol levels and promote cardiovascular health via different mechanisms, such as inhibition of cholesterol synthesis and suppression of cholesterol uptake. Inhibition of cholesterol solubilization into micelles and cellular cholesterol absorption are target sites of interventions for cholesterol reduction. Artificial micelles have been used as a model system for in vitro cholesterol solubilization and/or cholesterol absorption assays to evaluate hypocholesterolemic activity of potential bioactive compounds, including milk whey protein. This study aimed to compare the efficacy of artificially prepared micelles with naturally derived micelles from pig's bile on micellar solubility of cholesterol and cellular cholesterol absorption assays to identify potential cholesterol-lowering compounds. Green tea catechins and IIAEK with previously reported inhibitory effects on cholesterol uptake were used as reference compounds. Tea catechins, e.g. epigallocatechin gallate (EGCG), significantly reduced the solubility of cholesterol in pig's bile-derived micelle preparations (56%, p<0.001), which was comparable with those in artificially prepared micelles (65%, p<0.001). Suppression of cholesterol absorption in Caco-2 cells by IIAEK was also noted when using either artificially-prepared or pig's bile-derived micelle preparations (24%...

‣ Statut des transporteurs du cholestérol au niveau de l'intestin et du foie dans le diabète de type 2

Lalonde, Geneviève
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
Português
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La résistance à l’insuline et le diabète de type 2 (DT2) sont caractérisés par une hyperlipidémie. Le but de cette étude est de déterminer si le DT2 contribue au dérèglement du métabolisme du cholestérol au niveau du petit intestin et du foie du Psammomys obesus, un modèle animal nutritionnel d’induction de la résistance à l’insuline et du DT2. L’absorption intestinale du cholestérol est diminuée chez les animaux diabétiques. Cette diminution est associée à une baisse (i) de l’expression génique et protéique de NPC1-L1 qui joue un rôle primordial dans l’absorption du cholestérol au niveau des entérocytes; et (ii) de l’ARNm de l’ABCA1 responsable de l’efflux de cholestérol des cellules intestinales à l’apolipoprotéine A-I et aux HDLs. En ce qui a trait aux transporteurs SR-B1 et Annexin II, aucune différence n’a été observée au niveau intestinal. Toutefois, une diminution significative de l’expression génique de l’ABCG5, un intervenant majeur dans la sécrétion du cholestérol des entérocytes vers la lumière intestinale, est mesurée chez les animaux diabétiques. De plus, l’expression protéique est diminuée pour le PCSK9 et augmentée pour le LDLr au niveau du jéjunum...

‣ Regulation of HMG-CoA reductase, HSL and ACAT expression and activity in testicular cholesterol metabolism in mink and in mouse following experimental genetic deletion

Chen, Li
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
Português
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Introduction: L'homéostasie du cholestérol est indispensable à la synthèse de la testostérone dans le tissu interstitiel et la production de gamètes mâles fertiles dans les tubules séminifères. Les facteurs enzymatiques contribuent au maintien de cet équilibre intracellulaire du cholestérol. L'absence d'un ou de plusieurs enzymes telles que la HMG-CoA réductase, la HSL et l'ACAT-1 a été associée à l'infertilité masculine. Toutefois, les facteurs enzymatiques qui contribuent au maintien de l'équilibre intra-tissulaire du cholestérol n'ont pas été étudiés. Cette étude a pour but de tester l'hypothèse que le maintien des taux de cholestérol compatibles avec la spermatogenèse nécessite une coordination de la fonction intracellulaire des enzymes HMG-CoA réductase, ACAT1 et ACAT2 et la HSL. Méthodes: Nous avons analysé l'expression de l’ARNm et de la protéine de ces enzymes dans les fractions enrichies en tubules séminifères (STf) de vison durant le développement postnatal et le cycle reproductif annuel et dans les fractions enrichies en tissu interstitiel (ITf) et de STf durant le développement postnatal chez la souris. Nous avons développé deux nouvelles techniques pour la mesure de l'activité enzymatique de la HMG-CoA réductase et de celle de l'ACAT1 et ACAT2. En outre...

‣ Carence en œstrogènes et bases moléculaires du métabolisme des triglycérides et du cholestérol dans le foie et l'intestin : effet de l'exercice physique

Ngo Sock, Emilienne Tudor
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
Português
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La stéatose hépatique et la détérioration du profil lipidique plasmatique sont des pathologies métaboliques favorisées par la carence œstrogénique post-ménopausique. Cependant les mécanismes à la base de ces pathologies n’ont été que très peu étudiés. Le but de cette thèse a été d’investiguer les mécanismes moléculaires possibles à l’origine de l’hypercholestérolémie et de l’accumulation des lipides (triglycérides : TG et cholestérol) dans le foie en utilisant un modèle animal de la ménopause, la rate Sprague Dawley ovariectomisée (Ovx). Nous avons également examiné si le changement des habitudes de vie comme la pratique de l’exercice physique pouvait prévenir ou corriger les modifications induites par l’Ovx. Enfin, rosuvastatine (statine) a été utilisée comme thérapie pharmacologique de l’hypercholestérolémie dans le but de comprendre son effet au niveau moléculaire chez la rate Ovx. L’objectif de la première étude était de déterminer comment l’Ovx peut affecter les niveaux de TG et de cholestérol dans le foie des rates nourries avec une diète riche en lipides (HF : 42% gras). Les rates ont été soumises à la diète HF ou normale pendant 6 semaines avant d’être Ovx ou Sham (ovariectomie simulée)...

‣ Regulation of cholesterol intake by the corpus luteum

Miranda, Leonor
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
Português
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Résumé L’approvisionnement en cholestérol est un facteur limitant la stéroïdogenèse ovarienne. Pour cette raison, la majorité du cholestérol requis pour la synthèse des stéroïdes est importé de la circulation via les récepteurs des lipoprotéines de haute (HDL) et de basse densité (LDL) nommés scavenger receptor (SR-BI) et low-density lipoprotein receptor (LDLr). L’ARN messager de SR-BI est exprimé dans les ovaires de porcs durant toutes les étapes de la folliculogenèse ainsi que dans le corps jaune (CL). L’expression de la protéine SR-BI a également été détectée dans les follicules de souris lors du cycle œstral. Chez les deux espèces, l’expression est concentrée dans le cytoplasme et en périphérie des cellules du follicule. Les gonadotrophines induisent l'expression de SR-BI dans les cellules de la granulosa porcines, avec une expression cytoplasmique qui augmente durant la période périovulatoire, et avec une migration aux périphéries cellulaires durant la maturation du CL. Une conformation de 82 kDa de SR-BI est fortement exprimée dans le CL porcin, avec une conformation moins abondante de 57 kDa. Les différences entre les conformations sont attribuables à la glycosylation. La culture in vitro de follicules porcins avec des gonatrophines chorioniques humaines (hCG) a induit une hausse de régulation dépendante du temps du SR-BI de 82 kDa dans les cellules du granulosa. SR-BI et LDLr ont été exprimés réciproquement...

‣ Cholesterol oxides inhibit cholesterol esterification by lecithin: cholesterol acyl transferase

Pincinato, Eder de Carvalho; Moriel, Patricia; Abdalla, Dulcinéia Saes Parra
Fonte: Universidade de São Paulo. Faculdade de Ciências Farmacêuticas Publicador: Universidade de São Paulo. Faculdade de Ciências Farmacêuticas
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ; ; ; ; Formato: application/pdf
Publicado em 01/09/2009 Português
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Cholesterol oxides are atherogenic and can affect the activity of diverse important enzymes for the lipidic metabolism. The effect of 7β-hydroxycholesterol, 7-ketocholesterol, 25-hydroxycholesterol, cholestan-3β,5α,6β-triol,5,6β-epoxycholesterol, 5,6α-epoxycholesterol and 7α-hydroxycholesterol on esterification of cholesterol by lecithin:cholesterol acyl transferase (LCAT, EC 2.3.1.43) and the transfer of esters of cholesterol oxides from high density lipoprotein (HDL) to low density lipoproteins (LDL) and very low density lipoproteins (VLDL) by cholesteryl ester transfer protein (CETP) was investigated. HDL enriched with increasing concentrations of cholesterol oxides was incubated with fresh plasma as source of LCAT. Cholesterol and cholesterol oxides esterification was followed by measuring the consumption of respective free sterol and oxysterols. Measurements of cholesterol and cholesterol oxides were done by gas-chromatography. 14C-cholesterol oxides were incorporated into HDL2 and HDL3 subfractions and then incubated with fresh plasma containing LCAT and CETP. The transfer of cholesterol oxide esters was followed by measuring the 14C-cholesterol oxide-derived esters transferred to LDL and VLDL. All the cholesterol oxides studied were esterified by LCAT after incorporation into HDL particles...