Дисертації з теми "Métabolisme des dérivés du cholestérol"
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Leclerc, Thierry. "Anomalies du métabolisme lipoprotéique des transplantés cardiaques : mise en évidence d'un déficit du transfert des esters de cholestérol." Paris 5, 1992. http://www.theses.fr/1992PA05P008.
Descat, Amandine. "Développements de méthodes d'analyse des plastifiants de type phtalates et des acides biliaires dans des matrices biologiques : applications dans différents contextes physiopathologiques." Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILS054.
This thesis has two main focuses:1/ Plasticizers, including phthalates, have been identified as category 1b carcinogenic, mutagenic and reprotoxic (CMR) and as endocrine disruptors. Di-2-ethylhexyl phthalate (DEHP) is one of the most common plasticizers and is generally associated with polyvinyl chloride (PVC) in medical devices. As DEHP is not covalently bound to PVC, it can easily migrate into lipophilic matrices and then reach the bloodstream. It is metabolized by the liver into mono-2-ethylhexyl phthalate (MEHP), which is just as toxic. In recent years, alternative plasticizers to DEHP have been developed, notably di-2-ethylhexyl terephthalate (DEHT), which is metabolized in vivo to mono-2-ethylhexyl terephthalate (MEHT).The first part of this thesis involved developing methods for measuring plasticizers and their metabolites in various biological matrices, such as plasma. Two LC-MS/MS methods were developed for the determination of DEHP and MEHP as well as DEHT metabolites. As the ionization in mass spectrometry of DEHT is very low, a LC-UV method was developed to quantify this terephthalate. These methods have made it possible to estimate the release of DEHP and DEHT from blood bags and to measure their primary metabolites in blood products.2/ Bile acids (BA) are a large family of steroids made up of numerous species. They are synthesized in the liver and intestine and represent the main route of cholesterol catabolism. 7a-hydroxy-4-cholesten-3-one (C4) is the precursor of BA. BA play an essential role in lipid absorption but also in cell signaling, as they are ligands for the nuclear receptor 'Farnesoid X receptor' (FXR) and/or the G protein-coupled membrane receptor, TGR5. These receptors, and hence their ligands, are involved in glucose homeostasis, lipid homeostasis and energy expenditure. Any modulation of the BA profile can therefore lead to changes in metabolic homeostasis. The second part of this thesis involved developing two LC-MS/MS assay methods for 31 BA species and C4 in different biological matrices, including plasma. A specific method for the determination of recently described BA derived from LCA in caecal contents is currently being optimized. These methods have made it possible to analyze variations in the BA profile in various cardiometabolic disease contexts (obesity, insulin resistance, type 2 diabetes, NAFLD).In conclusion, the analytical methods developed for quantifying plasticizers and BA have been validated and applied in preclinical and clinical studies. Interestingly, data from the literature and preliminary transient transfection assays have shown that phthalates and their metabolites modulate the activity of the peroxisome proliferator-activated receptor alpha (PPARa), a key regulator of metabolic homeostasis and expression of CYP7A1 (a major enzyme in hepatic BA synthesis). The analytical tools developed in this thesis open up original perspectives for studying the effects of phthalates on metabolic homeostasis via the regulation of BA metabolism. All of this work has made it possible to link analytical developments and applications in the field of biology and health
Paillasse, Michaël. "Métabolisme du cholestérol et cancer." Toulouse 3, 2009. http://thesesups.ups-tlse.fr/766/.
This manuscript describes the study of deregulations of the metabolism of cholesterol occuring in cancerous processes. This includes first the importance of esters of cholesterol to the proliferation of cancer cells. Evidence is given the effects of cancer drugs such as Tamoxifen are concurrent to inhibition of the Cholesterol Epoxyde Hydrolase and potentially to the accumulation of 5, 6a-epoxycholestanol in the tissues. We postulated the existence of a new metabolism around this epoxyde, consisting in its aminolysis by biogenic amines and have shown that such products, the Dendrogenines, promote differenciation in different cell lines resulting in either anticancerous (Dendrogenine A) or neuroprotective (Dendrogénine B) activities. Finally we could explain the difference of reactivity toward nucleophiles between 5,6a- and 5,6beta- epoxycholestanol and could vouch for the stereospecificity of aminolysis reaction
Chériti, Abdelkrim. "Hémisynthèses de saponosides dérivés du cholestérol et des acides oléanolique et ursolique." Aix-Marseille 3, 1992. http://www.theses.fr/1992AIX30053.
Lauressergues, Emilie. "Antipsychotiques et métabolisme hépatique des lipides et du cholestérol." Lille 2, 2010. http://www.theses.fr/2010LIL2S020.
Schizophrenia is a psychiatric disorder that heavily impacts the mental functions and social relations of the patients concerned. More than 1 % of the world population suffers from this disease that is characterized by different kinds of symptoms which are commonly subclassified as either positive (hallucinations, illusions) or negative (loss of affect and motivation, social withdrawal). These symptoms can be controlled by treatment with antipsychotic drugs (APDs) which act primarily through the modulation of dopamine and serotonin receptors. Unfortunately, some of these drugs induce important metabolic side effects such as weight gain (as much as 10 kg the first year with clozapine for example), dyslipemia, alterations of glucose homeostasis and development of diabetes. The consequences of these disturbances are treatment disruption and an increase of cardiovascular risks which contributes to a death rate twice as high for schizophrenic patients versus the general population, associated with a reduction in the average life expectancy by 10 years. The mechanisms underlying the side effects by APDs are not completely understood. At the level of the central nervous system (CNS), actions on serotoninergic, dopaminergic or histaminergic receptors are believed to be implicated in metabolic side effects (particularly by modifying appetite or energy homeostasis). In the periphery, certain APDs perturb essential physiological functions such as insulin secretion by pancreatic b cells, glucose transport into skeletal muscle and lipogenesis at the adipose tissue level, as well as physiological parameters like the sensitivity of various tissues to insulin. Althoug the liver is an essential organ for maintaining the nutrients homeostasis, few studies show an interest for the direct impact of these molecules on this tissue. The main goal of this thesis is to characterise the impact of APDs on hepatic lipid and cholesterol metabolism using various markers from appropriate hepatocyte cellular models, such as de novo synthesis of lipids and cholesterol, the quantification of the mature transcription factors SREBP-1 and -2 (sterol regulatory element binding protein) as well as the evaluation of the expression of several genes of interest. In the first part, we selected hepatocyte cellular models (cells isolated from rat liver and the human IHH cell line) and showed their relevance for the study of the “potential adverse effects” of different compounds on lipid and cholesterol metabolism. For this, the physiological and sensitive character of these cultures was shown through their response to nutritional (or hormonal) changes and to pharmacological treatments. In the second part, we highlighted three profiles of APD molecules :-molecules strongly inducting de novo lipogenesis and cholesterogenesis (clozapine, olanzapine, risperidone and NDMC), -molecules with more moderate effects (haloperidol and paliperidone), -molecules with little or no effect(s) (aripiprazole, quetiapine, bifeprunox and chlorpromazine). Induction of de novo lipogenesis and cholesterogenesis by certain APDs is associated to the stimulation of the SREBP pathway (transcription factors and SREBP target genes) and correlate relatively well with the metabolic disturbances of schizophrenia patients under APD treatment. We therefore suggest that certain unfavourable effects of these APD molecules are due to a direct action on the liver. Furthermore we stated that those APDs that present the most unfavourable profiles in our in vitro models, activate the PERK pathway (protein kinase RNA-like ER kinase) of the UPR (unfolding protein response), illustrating the presence of endoplasmic reticulum (ER) stress. However, the ER stress is known to activate the SREBP pathways and to cause, in chronic, diseases such as steatosis, dyslipidemia and diabetes. This discovery opens new perspectives regarding the research for the action mechanisms of these molecules. More precisely, in our human hepatocyte model we show that the treatment with thapsigargine (inductive of ER stress by calcium depletion) stimulates the SREBP pathways. Whereas no detectable modification of the cytosolic calcium concentrations was observed following APD treatment, the use of calcium chelating agents reverses the effects of clozapine on the SREBP-1 and -2 pathways. We therefore presume that clozapine, by disturbing calcium homeostasis, generates ER stress which would activate the SREBPs pathways and lipogenesis and cholesterogenesis in consequence. To corroborate these findings, two experimental studies in rat and mouse were conducted that support our in vitro results. In the rat, a study employing acute drug administration confirms that clozapine, olanzapine and risperidone, at an early stage (1h, 3h), cause transcriptional deregulations of hepatic lipogenic, cholesterogenic and UPR genes. In the mouse, a study with chronic administration of risperidone indicates significant inductions of weight gain in relation to the activation of the SREBP-1c pathway and of FAS (fatty acid synthase). Altogether these data suggest that independent of their specific effects at the CNS level, APDs can modulate hepatic lipid metabolism. In conclusion, rat primary hepatocyte cultures and IHH cells are models of interest for the detection of potential unfavourable effects of molecules on hepatic lipid and cholesterol metabolism. Moreover, the SREBP pathways (proteins and target genes associated) are appropriate indicators of cellular metabolic disturbances and thus can be considered as pertinent markers of the respective processes. These models could therefore be integrated in the research process and in the selection of new chemical compounds destined to become APDs. With respect to the clinic, our results support the strategy to associate hypolipemic or hypocholesterolemic (statines) treatments to patients treated with clozapine, olanzapine and risperidone
Harmancey, Romain. "Caractérisation des propriétés de deux protéines associes à l'obésité : une nouvelle apolipoprotéine et l'adrénomedulline." Toulouse 3, 2006. http://www.theses.fr/2006TOU30195.
White adipose tissue is known to secrete a number of proteins named adipokines, whose dysregulations are suspected to play major roles in the development of several diseases commonly associated to obesity. Moreover, excess fat deposition in cardiomyocytes is believed to contribute to heart diseases through lipotoxicity and lipoapoptosis processes. The present data aimed to define the physiological functions of two secreted proteins up-regulated in obese patients. We demonstrate that one of these proteins, whose cardiac expression is increased with obesity, is a novel apolipoprotein (named Apo O) originally linked to a chondroitine sulfate chain, found mainly associated to HDL particles. Recombinant Apo O strongly stimulates cholesterol efflux from cells. Thus, Apo O could contribute to heart protection by preventing lipid accumulation in cardiomyocytes. The second protein studied, adrenomedullin (AM), is a multifunctional regulatory factor known for its natriuretic and vasodilating properties. Our results demonstrate that AM is a new adipokine that acts locally to modulate fat mass metabolism and development. First, we reported that AM inhibits isoproterenol-induced lipolysis through the nitric oxide-dependent oxidation of the beta-agonist. This reaction generates aminochromes, which is the product of catecholamines' oxidation and known to be cardiotoxic. Second, the molecular modulation of AM synthesis in a murine preadipocyte cell line showed that the peptide has anti-adipogenic properties. This last finding could be related to insulin proadipogenic effects since we found AM to be down-regulated by insulin at the transcriptional level through insulin-responsive elements
Viallard, Viviane. "Aspects du métabolisme énergétique et du métabolisme du cholestérol dans la cellule néoplasique du côlon." Toulouse 3, 1991. http://www.theses.fr/1991TOU30247.
Blanchard-Louis, Claire. "Effets de la chirurgie bariatrique sur le métabolisme du cholestérol." Thesis, Nantes, 2016. http://www.theses.fr/2016NANT1020/document.
Obesity is a major public health issue, with increasing prevalence. Metabolic complications such as type 2 diabetes, hypertension and dyslipidemia are frequently associated with morbid obesity. Bariatric surgery represents the therapeutic alternative of choice for these patients. Clinical studies show thatplasma cholesterol is clearly improved after surgery. Interestingly, the magnitude of reduction depends on the surgical techniques used suggesting that cellular and molecular mechanisms involved are different. Using mouse models,we demonstrated that Roux en Y Gastric Bypass (RYGB) strongly lowers plasma cholesterol compared to sleeve gastrectomy. RYGB increases fecal cholesterol excretion via the stimulation of trans intestinal cholesterol excretion (TICE) and a reduction of intestinal cholesterol absorption. In this context, and expanding in the management of hypercholesterolemia, TICE seems to be an interesting therapeutic target.In parallel with this work, we assessed, in collaboration with members of INSERM unit 913 (Dr Neunlist), the short-term effect of sleeve gastrectomy on intestinal barrier. We show that sleeve gastrectomy induces significant modifications of intestinal para and transcellular permeability by altering the expression of proteins involved in tight junctions. These changes favor plasma LPS translocation promoting a low grade pro-inflammatory state in adipose tissue. These effects of sleeve gastrectomy on intestinal permeability remain to be assessed after a longer post-surgical period
Kreit, Joseph. "Catabolisme microbien des stérols : caractérisation de la cholestérol oxydase, de la cholestérol ester hydrolase et d'une alcool secondaire deshydrogénase chez Rhodococcus Sp. CIP 105 335." Vandoeuvre-les-Nancy, INPL, 1999. http://www.theses.fr/1999INPL044N.
Jenty, Marion. "Rôle de la signalisation LRP1/Wnt5a dans le métabolisme du cholestérol." Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAJ025/document.
Protects against intracellular cholesterol accumulation and we identified the secreted protein Wnt5a as a partner of this inhibitory effect of LRP1. The aim of this thesis is to determine the molecular mechanisms by which the LRP1/Wnt5a signaling pathway prevents cholesterol accumulation in cells and to study the antiatherogenic potential of Wnt5a. We first showed in vitro and in vivo that Wnt5a decreases cellular cholesterol content by stimulating its efflux through the induction of cholesterol transporters expression and by down-regulating the expression of HMGCoA-reductase. Then we used mice deleted for Wnt5a specifically in smooth muscle cells, which present more atherosclerotic lesions than control mice after a high cholesterol diet. This confirms that Wnt5a protects against atherosclerosis and could be an interesting therapeutic target in the treatment of the disease
Bouvier, Jérôme. "Bis( Monoacylglycéro )Phosphate, acide docosahexaénoïque et cholestérol : relations métaboliques et fonctionnelles dans les macrophages." Lyon, INSA, 2008. http://theses.insa-lyon.fr/publication/2008ISAL0123/these.pdf.
Bis(monoacylglycero)phosphate (BMP) is a unique phospholipid preferentially found in late endosomes of mammalian cells. BMP is involved in the transport of macromolecules that transit through this compartment. We show that an anti-BMP antibody or the accumulation of BMP in cultured macrophages alters the redistribution of lipoprotein-derived cholesterol from late endosomes to plasma membrane and endoplasmic reticulum. Moreover, BMP selectively incorporates docosahexaenoic acid (DHA, 22:6n-3) whose cardiovascular benefits have been reported in Humans. We here report that high supplementation of DHA both in vitro and in vivo stimulate the formation of the 22:6/22:6-BMP molecular species. This molecule is very prone to peroxidation, and as such, is able to protect cholesterol against oxidation. We therefore propose that 22:6/22:6-BMP could act as a potential anti-oxidant in its immediate vicinity in endosomal membranes
Fraticelli, Jean. "Le cholestérol : données actuelles relatives à son métabolisme, influence de facteurs alimentaires." Paris 5, 1988. http://www.theses.fr/1988PA05P167.
Hudry, Eloïse. "Cholestérol et maladie d'Alzhiemer : le rôle de la cholestérol 24-hydroxylase." Paris 5, 2008. http://www.theses.fr/2008PA05T032.
Alzheimer disease (AD) is characterized by the presence of extracellular amyloid β (Aβ) deposits. Aβ peptides are produced through the successive cleavage of APP by β- and y-secretases. Several studies have demonstrated a clear link between AD and lipid metabolism. In the brain, cholesterol in excess can only be exported as 24S-hydroxycholesterol, this conversion being controlled by the cholesterol 24-hydroxylase. We studied the effects of the modulations of the cholesterol 24-hydroxylase activity in the APP23 mice, an AD mouse model. Our results suggest that the overexpression of the cholesterol 24-hydroxylase (though intracerebral gene transfer) may be a valuable therapeutic strategy for AD. On the contrary, its inhibition seems toxic and increases the production of Aβ peptides. A change of cholesterol 24-hydroxylase activity is therefore able to play a beneficial or noxious role on AEX
Sterjiades, Raja. "Oxydation de dérivés benzoi͏̈ques par Moraxella sp. , souche GU2." Grenoble 1, 1989. http://www.theses.fr/1989GRE10083.
Salvini, Séverine. "Influence des glucides alimentaires sur l'absorption intestinale du cholestérol : études chez l'homme sain et sur modèle entérocytaire humain Caco-2." Aix-Marseille 2, 2001. http://theses.univ-amu.fr.lama.univ-amu.fr/2001AIX20694.pdf.
Chanson, Nathalie. "Contribution à l'étude des interactions entre les lipoprotéines plasmatiques et les émulsions lipidiques intraveineuses." Paris 5, 2001. http://www.theses.fr/2001PA05P619.
In parenteral nutrition, lipids are delivered in the form of intravenous lipid emulsions (ILE),which contain triglycerid-rich particles (TGRP) and phospholipid-rich particles. In vitro and in the bloodstream, ILE particles interact with lipoproteins (apolipoprotein acquisition and lipid exchanges). In the present work, a new type of interaction between low-density lipoprotein (LDL) and ILE particles, was observed. After incubation, some apo B, was measured in the incubated emulsion fraction, despite they are structural non-exchangeable apolipoprotein of LDL. These results suggest the formation of LDL-TGRP complex, which are separated by ultracentrifugation and chromatography and this was confirmed by electron microscopy [. . . ]
Morozova, Svetlana. "Recherche du mécanisme d'action moléculaire de l'agent hypocholestérolémiant et anti-athéromateux, LF 08-0133." Université Louis Pasteur (Strasbourg) (1971-2008), 2003. http://www.theses.fr/2003STR13235.
Atherosclerosis is a disease characterised by lipid accumulation in the vascular wall leading to heart attack or stroke. Hypercholesterolemia is an important risk factor and current treatments are largely based on cholesterol lowering. In spite of proven efficacy of existing drugs, cardiovascular disease still remains the most common cause of death in industrialized countries. LF 08-0133 is an original compound from Fournier Laboratories with hypocholesterolemic and antiatherosclerotic properties. It has further been shown to be an intestinal cholesterol absorption inhibitor (ICAI) in vivo. The aim of this work is to determine the molecular mechanism of action of LF 08-0133. Firstly, the identification of target genes of this compound was attempted in the intestine, liver and aorta of mice. Among the numerous genes of cholesterol metabolism investigated, there was no direct modification of gene expression by LF 08-0133. Additionally, based on the broad gene expression technique employed (RAP-PCR), the compound did not modulate gene expression in the intestine. This does not totally exclude the hypothesis of modification of expression, as the technique employed did not permit a complete coverage of the transcriptome. Secondly, the ICAI mechanism of the drug was investigated by attempting to identify potential intestinal target proteins. LF 08-0133 column immobilisation and subsequent affinity chromatography resulted in the isolation of 11 intestinal protein bands, which are currently being identified. Finally, in an attempt to develop an in vitro model, the ICAI activity of LF 08-0133 was tested in Caco-2 cells (enterocyte) and the drug was found to be inactive. The LF 08-0133 molecular mechanism of action does not appear to involve the regulation of gene expression, but could result from drug – intestinal protein interactions. The Intestine appears to be one of target organs of the compound. Further studies are needed to identify molecular targets of LF 08-0133
Noguer, Emmanuel. "Étude du métabolisme de la dendrogénine A." Toulouse 3, 2014. http://www.theses.fr/2014TOU30286.
Our laboratory has recently demonstrated the existence of dendrogenine A (DDA), a new metabolite derived from cholesterol with tumor suppressor properties: DDA is present in healthy tissue while it is found in smaller amounts in tumors. These observations suggest a deregulation of the metabolism of the DDA in cancers, it seems important to identify the DDA synthetase. During my PhD I have: 1) identified the DDA synthetase studied its enzymatic parameters, its expression and localization in normal and cancerous human breast tissue; 2) developed a method for quantifying the DDA by coupling HPLC / MS; 3) Ioptimized the extraction and the purification of oxidized derivatives of cholesterol present in complex biological matrices for their quantification by mass spectrometry
Cachefo, Pereira de Souza Ana Célia. "Lipogénèse hépatique et synthèse du cholestérol au cours des malabsorptions sévères et de l'hyperthyroïdie humaine." Lyon 1, 2001. http://www.theses.fr/2001LYO1T224.
El, Asmar Zeina. "Rôle de Wnt5a dans l'homéostasie du cholestérol et deux pathologies l'athérosclérose et l'obésité." Strasbourg, 2011. http://www.theses.fr/2011STRA6201.
The imbalance of the cellular homeostasis of cholesterol in macrophages and VSMCs as well as adipose tissue has several adverse consequences in the organism. At the vessel wall, the imbalance of the cellular homeostasis of cholesterol induces the formation of foam cells secrete, many growth factors and cytokines. That amplifies the inflammatory response and contributes to the development of plate atherosclerosis. In adipose tissue, modulation of cellular homeostasis of cholesterol promotes the installation of obesity. Knowledge of target molecules and understanding of the mechanisms involved in regulating cellular homeostasis of cholesterol is essential to prevent the intracellular accumulation of cholesterol and the formation of atherosclerotic plaques. The role of Wnt5a protein in the regulation of cellular cholesterol accumulation had, to date, not been studied. In vitro, our results have shown for the first time we have shown in the presence of LRP1, Wnt5a is expressed and could reduce the cellular accumulation of cholesterol in MEFs after treatment with an adipogenic cocktail. In addition, we have shown in vivo in the presence of LRP1, Wnt5a induces the expression of genes Sox9 and Cart1 markers of chondrogenesis and thus contribute to the activation of chondrocyte differentiation program in terms of atherosclerotic lesions. In vivo, we showed that overexpression of Wnt5a in the white and brown adipose tissue in mice could reduce cholesterol accumulation in adipocytes. We demonstrated that Wnt5a induces a decrease the expression of genes encoding for enzymes involved in cholesterol synthesis (HMGCoA synthase and HMGCoA reductase 2) and the transporter involved in cholesterol efflux (ABCA1) in mice
Travert, Carine. "Rôle du cholestérol et de ses dérivés oxygénés dans la stéroi͏̈dogenèse leydigienne du rat mature." Caen, 2001. http://www.theses.fr/2001CAEN2014.
Bailhache, Edwige. "Étude du métabolisme des lipoprotéines chez le chien par les isotopes stables : effet de l'insulinorésistance associée à l'obésité." Nantes, 2003. http://www.theses.fr/2003NANT2009.
Our aim was to study lipoproteins metabolism and reverse cholesterol transport in healthy dogs, a species which has a low CETP activity, and then in insulin resistant (IR) dogs. In healthy dogs, apo B100 exclusively appears in VLDL, which high production is associated with a high catabolism (5-fold greater than that of human). LDL-apoB100 metabolism seems to be similar in dogs and humans. Our results showed that the healthy dog does not exhibit any CETP activity in vivo, and that a high level of reverse cholesterol transport is due to a very important LCAT activity and a high HDL cholesteryl ester selective uptake. Indeed, among species lacking of CETP activity, the dog could to be the best model for the study of the modulation of HDL cholesteryl ester selective uptake. Lipoprotein profiles obtained from FPLC in obese IR dog show that lipids abnormalities are similar to those observed in IR human. These results, confirmed by kinetics suggest that obese IR dogs could have a CETP activity. IR leads to an increase in VLDL-apo B100, as a consequence of a lower lipolysis, and to a decrease in LDL-apo B100 level as a consequence of a higher catabolism. The model we developed could thus be useful for studying some effects of IR in humans
Moreau, François. "Rôle de PCSK9 et conséquences des chirurgies bariatriques sur le métabolisme intestinal du cholestérol." Thesis, Nantes, 2017. http://www.theses.fr/2017NANT4069/document.
The intestine is a major actor of cholesterol metabolism from its role in absorption, secretion of lipoproteins and transintestinal cholesterol efflux (TICE). In addition, it is the second major organ, after the liver, to express the Proproteine Convertase Subtilisin Kexin type 9 (PCSK9), the natural inhibitor of the LDL receptor. Our analysis of molecular mechanism involved in hypocholesterolemia induced by bariatric surgeries shows that the gastrectomy sleeve induces a transient and moderate hypocholesterolemia linked to the modification of the food intake. In contrast, the Roux-Y by-pass (RYGB) strongly reduces cholesterol, significantly stimulates its fecal elimination by inducing TICE and decreasing intestinal absorption of cholesterol. The second part of my thesis consisted to elucidate the controversy around the faculty of the intestine to secrete PCSK9. In vivo (mice) and ex vivo (mice and human), it seems that mature enterocytes can’t secrete PCSK9. On the other hand, we confirm that the Caco2, an human intestinal cell line, is capable of secreting PCSK9, but this secretion is abolished when the cells become mature. Mechanisms responsible for this loss of secretion remain poorly defined and are, at least, due to: 1) a reduction in the intracellular content induced by increased lysosomal catabolism; 2) a post-translational modification of PCSK9 (glycosilation) altering post-Golgi secretion pathways. Caco2 cells are a powerfull tool for identify the mechanisms and partners required for the secretion of PCSK9. Their identifiers allow the development of new inhibitors to reduce the secretion of PCSK9, reduce hypercholesterolemia and fight more effectively against cardiovascular diseases
Leger-Charnay, Elise. "Régulation du métabolisme du cholestérol dans la rétine en conditions expérimentales associées au glaucome." Thesis, Bourgogne Franche-Comté, 2019. http://www.theses.fr/2019UBFCK090.
Cholesterol is a lipid found in every animal cell and is necessary for its survival. Among its multiple roles in the body, it is a component of cell membranes that is crucial for the maintenance of their structure and fluidity and is thus implicated in the modulation of many signalling pathways. Neurons are especially dependant on cholesterol input since the proper composition of their plasma membrane is required for vesicular exocytosis of neurotransmitters and transduction of the post-synaptic signal. It has been shown that both an excess and a lack of cholesterol is neurotoxic. Moreover, many neurodegenerative diseases, such as Alzheimer’s or Huntington’s disease, have been associated with dysregulation of cholesterol homeostasis, highlighting the need for a fine regulation of its metabolism in nervous tissues. Coordinated actions of neurons and glia, that exhibit complementary functions, are mandatory in that respect. In the brain, astrocytes, the main macroglial cells, may be the major source of cholesterol biosynthesis and export. Neurons, acting as consumers, may be specifically in charge of cholesterol elimination via conversion into 24S-OHC by the CYP46A1 enzyme. This metabolite is likely not only an elimination product of cholesterol but also a signalling molecule in glial cells. It might enable glial cholesterol metabolism to adjust as needed and avoid an overload in brain tissues. In the retina, cholesterol metabolism and its regulation under physiological and pathological conditions remain largely unknown. Müller cells, the major macroglial cells of the retina, could participate in cholesterol synthesis in this tissue even though evidence is still needed. Regarding 24S-OHC, its synthesis is mainly restricted to retinal ganglion cells, neurons responsible for nervous signal transmission from the retina to the brain. Studies performed in our laboratory suggest that CYP46A1 and its product could be implicated in the physiopathology of glaucoma, a disease characterized by ganglion cell degeneration.The present project aims to provide a better understanding of cholesterol metabolism in Müller cells and its potential regulation by 24S-OHC. The goal is also to unveil changes in cholesterol metabolism during the progression of glaucoma by characterizing, at different time points, the molecular players implicated in its biosynthesis, transport and elimination. Our experiments performed on primary Müller cell cultures indicate that these cells possess the molecular machinery to synthesize and export cholesterol and could therefore actively participate in its metabolism in the retina. We also reported a strong hypocholesterolemic effect of 24S-OHC in Müller cells, reinforcing the hypothesis that this compound could be a regulator of cholesterol metabolism in the retina. In an experimental glaucoma model, induced by an elevation in intraocular pressure in rats, we observed major changes in cholesterol metabolism. At the earliest time points, genes implicated in cholesterol biosynthesis and uptake in the retina were upregulated, and cholesterol precursor levels were consecutively and transiently elevated. An important component of our work was to demonstrate that counter-regulatory mechanisms were activated in response to these initial dysregulations, that enabled the maintenance of cholesterol homeostasis in the retina and likely participated in ganglion cell survival
Colonna, Ceccaldi Benoît. "Métabolisme de dérivés de lignine par des souches environnementales de Klebsiella." Compiègne, 1985. http://www.theses.fr/1985COMPI213.
Lemieux, Christian. "Effets et mécanismes d'action d'un modulateur sélectif des récepteurs des oestrogènes sur le métabolisme des lipides." Thesis, Université Laval, 2005. http://www.theses.ulaval.ca/2005/22502/22502.pdf.
Hajri, Tahar. "Effets de la nutrition parentérale sur la biodynamique du cholestérol et des lipoprotéines chez le rat." Paris 11, 1988. http://www.theses.fr/1988PA112181.
The effects of parenteral nutrition (PN) on cholesterol and lipoprotein biodynamics have been studied in rats. After 5 days of intravenous infusion of a nutritive mixture, with or without lipids (Intralipid 20 %), rats exhibit a reduction of the intestinal mass and plasma levels of HDL, apo-AIV and apo-AI decrease, whereas those of apo-E and apo-B48 increased. PN does not change the overall uptake rate of 14c-labelled-HDL: intestine becomes less active, and the liver and spleen more active to internalize the HDL. The more spectacular effect induced by infused emulsion, is the plasma accumulation of an abnormal lipoprotein (lipoprotein-X) in the density zone of LDL (1,006-1,040). This particle results from the uptake of endogenous cholesterol by residual phospholipids of the emulsion after Iipolysis. The compared effects of 2 emulsions clearly indicate that, at the same infusion rate, Intralipid 20 % (triglycerides/ phospholids, TG/PL=100/6) generates less Iipoprotein-X than lntralipid 10 % (TG/ PL=100/12). Phytosterols, initially present in the soya oil of the emulsion, have been detected in all the lipoproteins and the intestinal content in rats infused with lipids. The activity of cholesterol synthesis, in vivo assessed by measurement of the 14c-acetate incorporation into hepatic and intestinal sterols, is markedly stimulated by PN. In rats intravenously infused with lipids, this effect directly results from the formation of lipoprotein-X. Finally, an increase of the bile acid pool, that reflects bile stasis, has been shown by an isotopic equilibrium method
Zaghini, Isabelle. "Le gène de l'I-BABP : implication dans l'homéostasie du cholestérol ?" Dijon, 2001. http://www.theses.fr/2001DIJOS044.
Burlot, Marie-Anne. "Modulation du métabolisme du cholestérol dans un modèle murin de Tauopathie : évaluation de la cholestérol 24-hydroxylase comme cible thérapeutique dans la maladie d’Alzheimer." Thesis, Paris 5, 2014. http://www.theses.fr/2014PA05T058/document.
Alzheimer’s disease (AD) is characterized by a progressive memory loss and neuropathologically by senile plaques and neurofibrillary tangles (NFTs). Senile plaques are constituted of extracellular amyloid peptide (Aβ) deposits while NFTs result from the accumulation and the aggregation of intracellular hyperphosphorylated Tau proteins. Spatiotemporal progression of NFTs particularly correlates with cognitive impairments. To date, there is no curative treatment for this disease. Cholesterol plays a central role in AD physiopathology. Indeed, the ε4 allele of the apolipoprotein E, the brain’s principal cholesterol-carrier protein, is the main genetic risk factor for sporadic forms of AD. Numerous in vitro studies have shown that cholesterol overload induces production of pathogenic Aβ and conversely, cholesterol depletion causes a reduction of the amyloidogenic pathway. In adult, brain cholesterol is exclusively synthesized in situ. Brain cholesterol is not able to freely cross the blood brain barrier and its major exportable form is 24(S)-hydroxycholesterol generated by the cholesterol 24-hydroxylase (CYP46A1). Two previous thesis works in this laboratory highlighted narrow connections between cholesterol metabolism and AD in vivo. The intracerebral overexpression of CYP46A1 mediated by an adeno-associated viral (AAV) vector, in a murine amyloid model, led to the decrease of Aβ production, senile plaques and improvement of memory abilities. At the opposite, hippocampal CYP46A1 inhibition in wild-type (WT) mice induced Aβ production, Tau phosphorylation and memory impairments. The aim of this thesis work was to determine whether there was a direct link between CYP46A1 and Tau pathology and whether cholesterol metabolism modulation could have a beneficial effect on AD-like Tau pathology. In order to answer these questions, the THY-Tau22 mouse model, that develops AD-like Tau pathology, was used. In this model, the pathology mainly occurs in the hippocampus, it is progressive, and associated with memory deficits. In THY-Tau22 mice, total free cholesterol in the hippocampus was unchanged, whereas both CYP46A1 protein expression and 24(S)-hydroxycholesterol content were decreased. Furthermore, we also demonstrated that CYP46A1 protein expression was reduced in another murine model of Tau pathology, the THY-Tau30 model. Therefore, it may suggest that Tau pathology can be responsible for CYP46A1 decrease. We next determined whether CYP46A1 overexpression in the THY-Tau22 mouse could improve its biochemical, clinical and neuropathologic phenotype. For this purpose, an AAV vector encoding CYP46A1 was injected in the hippocampus of 3.5-month-old WT and THY-Tau22 mice. Two and a half months after injection, hippocampal CYP46A1 overexpression in THY-Tau22 mice induced restoration of hippocampal 24(S)-hydroxycholesterol content and increased expression of genes involved in cholesterol synthesis, more particularly in the mevalonate pathway. Two and a half and five and a half months post-injection, CYP46A1 overexpression resulted in a complete restoration of memory abilities and was accompanied by restoration of long-term depression, length of secondary dendrites, synaptic density and expression of immediate-early genes in hippocampus. Despite this, abnormal Tau hyperphosphorylation and gliosis, that characterizes this model, remained unchanged after CYP46A1 overexpression. Altogether, these results suggest a direct connection between Tau pathology and CYP46A1 in vivo. In other words, Tau pathology could lead to memory deficits via CYP46A1 decrease. These data, together with the fact that CYP46A1 overexpression can modulate the amyloid pathology in mice, suggest that CYP46A1 may be a relevant therapeutic target for AD
Thies, Frank. "Etude de l'influence de différentes formes d'apport d'acides gras insaturés sur le métabolisme cellulaire." Dijon, 1991. http://www.theses.fr/1991DIJO5069.
Ouguerram, Khadija. "Étude du métabolisme du cholestérol des lipoprotéines plasmatiques chez le rat normal et génétiquement hypercholestérolémique (RICO)." Paris 11, 1989. http://www.theses.fr/1989PA112134.
In the genetically hypercholesterolemic (RICO) rat, the high cholesterol results mainly from an increase in the cholesterol content of LDL and HDL. The input-output analysis method showed an increase in cholesterol inputs associated with a secondary stimulation of the output. By using two pools analysis we observed slower movements of plasma cholesterol to the tissues. A study of plasma lipoprotein cholesterol turnover has been undertaken. The use of analogs undegradable by cells (14C-Saccharose, 14C-Cholestéryl-linoléyl-éther) allowed to measure the LDL and HDL uptake rates. Our main results in the RICO versus normocholesterolemic are the following : a decrease in the fractional catabolic rate of chylomicrons cholesterol ester related to the lipoprotein modification. An increase in the plasma VLDL transformation to LDL. A slower LDL fractional catabolic rate which is due to a modified LDL composition and a diminished LDL uptake in all tissues. An elevated production of HDL esterified cholesterol without any change in their catabolism. The uptake of HDL esterified cholesterol was lower in the adrenals, liver and testis in the RICO than in the control rats suggesting a lowered phospholipasic activity in the hypercholesterolemic animal
Fourgeux, Cynthia. "Cholestérol-24S-hydroxylase (CYP46A1) et homéostasie du cholestérol dans la rétine en conditions physiologiques et pathologiques." Phd thesis, Université de Bourgogne, 2012. http://tel.archives-ouvertes.fr/tel-00905888.
Thomas, Charles. "Impact du cholestérol sur le cycle entérohépatique des acides biliaires : conséquences pour l'homéostasie lipidique." Dijon, 2006. http://www.theses.fr/2006DIJOS016.
Hypercholesterolemia is a major risk factor of cardiovascular diseases. Understanding of mechanisms ensuring the maintenance of body cholesterol homeostasis is crucial, since it can allow the development of new hypocholesterolemiant therapies. Bile Acids (BA) are end-products of cholesterol metabolism. These molecules, produced in the liver, participate to fat digestion and absorption in the intestine. Moreover, BA represent the main pathway of body cholesterol removal. The results presented in this thesis show that genes encoding intestinal, hepatic and renal BA transporters are coordinately regulated. This mechanism ensures efficient BA elimination through faecal and urinary route, and thus contributes to explain the resistance of mice to diet-induced hypercholesterolemia. The transcription factors SREBP-2 and HNF-1, and the nuclear receptor PPAR, play a key role in this adaptative process since they allow cholesterol-dependent regulation of several key BA transporters, particularly ASBT in the ileum and the kidney, and L-FABP in the liver
Dusserre, Eric. "Métabolisme et mouvements du cholestérol dans les différents compartiments du myocyte artériel : mécanismes impliqués et influence de la dédifférenciation cellulaire." Lyon 1, 1994. http://www.theses.fr/1994LYO1T009.
Forcheron, Fabien. "Métabolisme du cholestérol chez l'homme : effet du fénofibrate et expression des gènes régulateurs dans la plaque d'athérome." Lyon 1, 2005. http://www.theses.fr/2005LYO10084.
Ben, Ali Yassine. "Etude du mécanisme d'inhibition de la lipase hormono-sensible humaine, cible thérapeutique pour le traitement du diabète du type 2." Aix-Marseille 2, 2006. http://theses.univ-amu.fr.lama.univ-amu.fr/2006AIX22002.pdf.
Marill, Julie. "Identification et comparaison des activités catalytiques des cytochromes P450 humains impliqués dans le métabolisme des isomères d'acide rétinoïque." Paris 7, 2003. http://www.theses.fr/2003PA077226.
Racine, Radjini. "Etude des effets d'une ingestion chronique de radionucléides sur le métabolisme du cholestérol chez le rat : exemples de l'uranium appauvri et du césium 137." Clermont-Ferrand 2, 2009. http://www.theses.fr/2009CLF21969.
Diraison, Frédérique. "Étude du métabolisme des acides gras libres, des triglycérides et du cholestérol à l'aide d'isotopes stables, chez le sujet normal." Lyon 1, 1998. http://www.theses.fr/1998LYO1T002.
Bennis, Abdel-Haq. "Contribution à l'étude des lipides et lipoprotéines sériques ou plasmatiques de la chèvre." Toulouse, INPT, 1992. http://www.theses.fr/1992INPT013A.
Hilaire, Nathalie. "Métabolisme cellulaire des lipides neutres cytoplasmiques et myopathie à surcharge lipidique multisystémique." Toulouse 3, 1994. http://www.theses.fr/1994TOU30051.
Malaval, Camille. "Régulation de la captation hépatique des HDL : la voie F1-ATPase/P2Y13 : de la caractérisation cellulaire au modèle animal." Toulouse 3, 2008. http://thesesups.ups-tlse.fr/390/.
HDL mediate the elimination of cholesterol thanks to their internalization by hepatocytes. We identified in hepatocytes a new pathway for HDL endocytosis as following: stimulation of an ectopic cell surface F1-ATPase by the HDL apolipoprotein A-I, induces the production of ADP which in turn activates the purinergic receptor P2Y13, triggering HDL endocytosis through unknown low affinity receptor(s). In one hand, we identified a major role of the small GTPase RhoA and its effector ROCK1 downstream P2Y13. This cell signalling stimulates the HDL endocytosis by remodelling actin cytoskeleton. In other hand, the study in mice showed the crucial role of P2Y13 in HDL catabolism and in the subsequent cholesterol biliary elimination. Taking together, these results demonstrate the importance of the receptor P2Y13 in cholesterol metabolism. Thus, P2Y13 appears as a new pharmacological target to control reverse cholesterol transport and prevent hypercholesterolemia
Dugardin, Camille. "Rôle du récepteur nucléaire Rev-erbα dans le contrôle du métabolisme lipidique dans l'entérocyte". Thesis, Lille 2, 2016. http://www.theses.fr/2016LIL2S045.
The intestine plays a key role in the control of energy homeostasis. Enterocytes, which constitute the main cellular type of intestinal epithelium (> 90%), are polarized cells allowing exchanges between intestinal lumen (apical membrane) and lymph/blood compartment (basolateral membrane). In this thesis, cholesterol and lipid metabolism control by enterocytes was studied and particularly, trans intestinal cholesterol excretion (TICE) and dietary lipid absorption.Recently, it has been estimated that intestine contributes 20-30% of fecal neutral sterol excretion in chow-fed mice. This pathway called TICE involves the direct luminal secretion of plasma-derived cholesterol by enterocytes. Moreover, TICE can be pharmacologically modulated, for instance by ezetimibe and statins and so, represents a new therapeutic target in order to prevent atherosclerosis in type 2 diabetic patients. However, at present, the molecular mechanisms behind the trans-enterocytic process of TICE are still unknown, especially the steps sustaining cholesterol entry, trafficking and efflux in enterocytes. In the first study of this thesis, we highlighted the human enterocytic Caco-2/TC7 cell line as a suitable model to study the enterocyte-related processes of TICE. We have first shown that upon basolateral incubation with human plasma and apical incubation with lipid micelles, differentiated Caco-2/TC7 cells mimic some of the in vivo TICE features. Moreover, using this model, we have identified a key role of the microtubule network in the process.In the second study of this thesis, chylomicron secretion by enterocytes and its control by the nuclear receptor Rev-erbα were investigated. Indeed, although chylomicron remnant accumulation has been associated to a delayed clearance by the liver, some recent studies show that chylomicron overproduction by the intestine is a major contributor to dyslipidemia in insulin resistant patients. Dietary lipid absorption results from a balance between transient storage in enterocytes as cytosolic lipid droplets (LD) and secretion as triglyceride-rich lipoproteins (TRL). The nuclear receptor Rev-erbα is a transcriptional repressor involved in the energy metabolism and the circadian rhythm. Particularly, Rev-erbα controls lipid metabolism in the liver and thus the catabolism of TRL. The aim of this second study was to investigate the role of Rev-erbα in intestinal lipid metabolism and particularly in TRL secretion. To study that, Caco-2/TC7 cells infected with lentivirus encoding or not a shRNA targeting Rev-erbα (sh Rev-erbα) were grown on transwells. Compared to sh control, sh Rev-erbα Caco-2/TC7 cells secrete higher amounts of micelle-derived LRT in the basolateral medium and exhibit lower quantity of neutral lipids stored as cytosolic LD, whereas the apical uptake is not different. Activation of lipophagy in sh Rev-erbα compared to sh control cells was evidenced by a higher autophagic flux and an increased colocalization of the autophagy marker LC3 with LD. Finally, autophagy inhibition with bafilomycin in sh Rev-erbα cells restores lipid secretion to the same level as in sh control cells. This second study show that Rev-erbα knock-down in enterocytes leads to a higher lipophagy-mediated remobilization of intracellular lipids and an increased TRL secretion. Our hypothesis is that Rev-erbα may be a molecular gear in the control of chylomicron secretion and a major regulator of post-prandial triglyceridemia.In conclusion, these two studies allow to better understand lipid metabolism control by the intestine: the first one by identifying the contribution of the microtubule network in enterocytes for trans-enterocytic retrograde cholesterol transport; the second one by highlighting the nuclear receptor Rev-erbα as a regulator of TRL secretion by enterocytes. These two studies point out the intestine as a potential therapeutic target to treat dyslipidemia in type 2 diabetic patients
Duclos, Sandrine. "Effets des proliférateurs de péroxysomes sur la régulation du cholestérol et de son métabolisme dans des modèles cellulaires d'origine hépatique." Dijon, 1997. http://www.theses.fr/1997DIJOS077.
Leplaix-Charlat, Laurence. "Effets des acides gras et du cholestérol alimentaires sur le métabolisme des lipides et des lipoprotéines aux niveaux plasmatique et hépatique chez le veau préruminant : conséquences sur la composition lipidique des tissus." Aix-Marseille 3, 1995. http://www.theses.fr/1995AIX30085.
Daval, Marie. "Rôle de l'AMP-activated protein kinase dans la régulation du métabolisme hépatique et adipocytaire." Paris 6, 2007. http://www.theses.fr/2007PA066592.
Chorin, Anne-Claire. "Synthèse enzymatique de nouveaux dérivés dithiolopyrrolones par Saccharothrix algeriensis." Thesis, Toulouse, INPT, 2009. http://www.theses.fr/2009INPT009A/document.
Saccharothrix algeriensis is a filamentous bacterium that produces many dithiolopyrrolone compounds with antibiotic and anti-tumour properties. These metabolites possess a common bicyclic nucleus, the pyrrothine, amide linked with variable acyl groups R. During this PhD project, the enzymatic reaction of pyrrothine acylation, identified as pyrrothine N-acyltransferase, was studied in Sa. algeriensis to further our understanding of the regulation exerted by organic acids on the dithiolopyrrolone biosynthesis and to produce new dithiolopyrrolone compounds by enzymatic catalysis. Evidence for the presence in the crude cell free extract of Sa. algeriensis of two enzymatic activities, pyrrothine Nacetyltransferase and N-benzoyltransferase is provided. They catalyze respectively the formation of the two dithiolopyrrolones, thiolutin (R= CH3) and benzoyl-pyrrothine (BEP, R = C6H5). To study the regulation exerted by organic acids, these enzymatic activities were then assayed in crude cell free extracts of Sa. algeriensis obtained during cultures on media supplemented with organic acids. The results show that BEP-production is enhanced in the presence of benzoic acid partly because of an induction of pyrrothine N-benzoyltransferase. Differences in the expression time courses of pyrrothine N-acetyltransferase and Nbenzoyltransferase activities were also observed. It supports the idea that the transfer reactions of acetyl-CoA and benzoyl-CoA on pyrrothine are catalyzed by two different enzymes. Their purification was undertaken and the cell free extract, crude or semi-purified was used as catalyst to synthetize nine dithiolopyrrolones with biological activities potentially new and better
Robichon, Céline. "Aspects spécifiques du métabolisme du cholestérol dans l'adipocyte : régulation des flux adipocytaires de cholestérol par ABCA1 et SR-BI : analyse fonctionnelle de DnaJA4, une nouvelle cible de SREBP2." Paris 6, 2006. http://www.theses.fr/2006PA066406.
Lamant, Matthieu. "Caractérisation d’une nouvelle apolipoprotéine humaine, l’Apo O." Toulouse 3, 2006. http://thesesups.ups-tlse.fr/1/.
Labonté, Marie-Ève. "Comparaison de l'impact des acides gras trans laitiers et industriels sur l'homéostasie du cholestérol chez l'humain." Master's thesis, Université Laval, 2010. http://hdl.handle.net/20.500.11794/22185.
Notre groupe de recherche a récemment démontré que des apports très élevés en acides gras trans naturels (AGTn) et industriels (AGTi) avaient des effets comparables sur les lipides et lipoprotéines plasmatiques. L'impact des différents AGT sur les processus impliqués dans l'homéostasie du cholestérol demeure toutefois inconnu et il nous est apparu important d'investiguer dans cette voie. Ce mémoire présente les résultats d'une étude dont l'objectif était de comparer l'impact des AGTi et des AGTn sur les marqueurs de la synthèse endogène et de l'absorption intestinale du cholestérol. Les résultats démontrent que le niveau d'absorption du cholestérol est modifié de façon plus importante suite à la consommation d'AGTn que d'AGTi, mais cette différence ne se reflète pas dans les concentrations de LDL-C entre les deux sources d'AGT. Il semble également que la consommation d'AGT n'affecte pas la synthèse endogène de cholestérol, peu importe leur origine.