Search results for "sterols"
showing 10 items of 174 documents
In vivo consequences of cholesterol-24S-hydroxylase (CYP46A1) inhibition by voriconazole on cholesterol homeostasis and function in the rat retina
2014
International audience; Cholesterol 24S-hydroxylase (CYP46A1) converts cholesterol into 24S-hydroxycholesterol in neurons and participates in cholesterol homeostasis in the central nervous system, including the retina. We aimed to evaluate the consequences of CYP46A1 inhibition by voriconazole on cholesterol homeostasis and function in the retina. Rats received daily intraperitoneal injections of voriconazole (60 mg/kg), minocycline (22 mg/kg), voriconazole plus minocycline, or vehicle during five consecutive days. The rats were submitted to electroretinography to monitor retinal functionality. Cholesterol and 24S-hydroxycholesterol were measured in plasma, brain and retina by gas chromatog…
Biosynthesis and transformation of 20α 21-dihydroxycholesterol by rat adrenal preparations
1979
Abstract The biosynthesis of [ 3 H]-20α, 21 dihydroxycholestderol from [ 3 H]-20α-hydroxycholesterol and its transformation to [ 3 H]-21-hydroxypregnenolone by rat adrenal preparations has been demonstrated. 20α-Hydroxycholesterol was transformed to 20α, 21-dihydroxycholesterol by microsomal preparations in the presence of NADPH and 20α-21-dihydroxycholesterol was metabolized to 21-hydroxypregnenolone by mitochondrial preparations in the presence of a NADPH-generating-system. Comparison of the Michaelis-Menten-Kinetics of the steps “20α, 21-dihydroxycholesterol → 21-hydroxycholesterol” and “20α-hydroxycholesterol → pregnenolone” revealed that both compounds behaved as analogue substrates of…
Evaluation of the therapeutic potential of PPARalpha agonists for X-linked adrenoleukodystrophy.
2003
Adrenoleukodystrophy protein (ABCD1), a peroxisomal membrane protein, is mutated in patients affected by X-linked adrenoleukodystrophy (X-ALD). Adrenoleukodystrophy-related protein (ABCD2) is the closest relative of ABCD1. Pharmacological induction of ABCD2 gene expression has been proposed as a novel therapy strategy for X-ALD. Fibrates induce peroxisome proliferation and Abcd2 expression in rodent liver. Here we evaluate the possibility of using peroxisome proliferator-activated receptor alpha (PPARalpha) agonists for pharmacological induction of ABCD2 expression. In the liver of PPARalpha-deficient mice, both the constitutive and the fenofibrate-inducible Abcd2 gene expression was found …
Effects of a phytosterol-enriched dairy product on lipids, sterols and 8-isoprostane in hypercholesterolemic patients: a multicenter Italian study.
2009
Abstract Background and aims Plant sterols, added to several food sources, lower serum cholesterol concentrations. Plant sterol-induced cholesterol lowering is paralleled by a mild decrease in plasma levels of the antioxidant β-carotene, the amount of this decrease being considered clinically non-significant. Whether the effect on lipid profile of daily consumption of plant sterol-enriched low-fat fermented milk (FM) is paralleled by a concomitant variation in a reliable marker of the oxidative burden like plasma isoprostane levels is unresolved. Methods and results The effect of plant sterol consumption on plasma lipid and isoprostane levels of hypercholesterolemic patients was evaluated i…
Relationship between ethanol tolerance, lipid composition and plasma membrane fluidity inSaccharomyces cerevisiaeandKloeckera apiculata
1994
The lipid composition of a strain of each of two yeasts, Saccharomyces csrevisiae and Kloeckera apiculata, with different ethanol tolerances, was determined for cells grown with or without added ethanol. An increase in the proportion of ergosterol, unsaturated fatty acid levels and the maintenance of phospholipid biosynthesis seemed to be responsible for ethanol tolerance. The association of ethanol tolerance of yeast cells with plasma membrane fluidity, measured by fluorescence anisotropy, is discussed. We propose that an increase in plasma membrane fluidity may be correlated with a decrease in the sterol: phospholipid and sterol: protein ratios and an increase in unsaturation index.
Revisiting Plant Plasma Membrane Lipids in Tobacco: A Focus on Sphingolipids
2016
International audience; The lipid composition of plasma membrane (PM) and the corresponding detergent-insoluble membrane (DIM) fraction were analyzed with a specific focus on highly polar sphingolipids, so-called glycosyl inositol phosphorylceramides (GIPCs). Using tobacco (Nicotiana tabacum) 'Bright Yellow 2' cell suspension and leaves, evidence is provided that GIPCs represent up to 40 mol % of the PM lipids. Comparative analysis of DIMs with the PM showed an enrichment of 2-hydroxylated very-long-chain fatty acid-containing GIPCs and polyglycosylated GIPCs in the DIMs. Purified antibodies raised against these GIPCs were further used for immunogold-electron microscopy strategy, revealing …
Mediation of Elicitin Activity on Tobacco Is Assumed by Elicitin-Sterol Complexes
2001
Elicitins secreted by phytopathogenic Phytophthora spp. are proteinaceous elicitors of plant defense mechanisms and were demonstrated to load, carry, and transfer sterols between membranes. The link between elicitor and sterol-loading properties was assessed with the use of site-directed mutagenesis of the 47 and 87 cryptogein tyrosine residues, postulated to be involved in sterol binding. Mutated cryptogeins were tested for their ability to load sterols, bind to plasma membrane putative receptors, and trigger biological responses. For each mutated elicitin, the chemical characterization of the corresponding complexes with stigmasterol (1:1 stoichiometry) demonstrated their full functionali…
Molecular modelling study of the role of cholesterol in the stimulation of the oxytocin receptor.
2001
Cholesterol, an integral component of membranes in Eucaryota, is a modifier of membrane properties. In vivo studies have demonstrated that cholesterol can also modulate activities of some G protein-coupled receptors (GPCRs), which are integral membrane proteins. This can result either from an effect of cholesterol on the membrane fluidity or from specific interactions of the membrane cholesterol with the receptor, as recently demonstrated for the cholecystokinin type beta (CCKRbeta) or the oxytocin receptor (OTR). Using molecular modelling, we studied conformational preferences of cholesterol and several of its analogues. Subsequently, we simulated the distributions of their preferred confo…
The 1.45 A resolution structure of the cryptogein-cholesterol complex: a close-up view of a sterol carrier protein (SCP) active site.
2002
Cryptogein is a small 10 kDa elicitor produced by the phytoparasitic oomycete Phytophthora cryptogea. The protein also displays a sterol carrier activity. The native protein crystallizes in space group P4(1)22, with unit-cell parameters a = b = 46.51, c = 134.9 A (diffraction limit: 2.1 A). Its complex with cholesterol crystallizes in space group C222(1), with unit-cell parameters a = 30.96, b = 94.8, c = 65.3 A and a resolution enhanced to 1.45 A. The large inner non-specific hydrophobic cavity is able to accommodate a large variety of 3-beta-hydroxy sterols. Cryptogein probably acts as a sterol shuttle helping the pathogen to grow and complete its life cycle.
Protective effect of antioxidants contained in milk-based fruit beverages against sterol oxidation products
2017
Abstract Sterol oxidation products (SOPs) have shown cytotoxic effect in human intestinal cells; however, their effect within a food matrix has not been assayed yet. This study evaluated the possible cytotoxic effect of SOPs within bioaccessible fractions (BFs) of two milk-based fruit beverages with (BFA)/without (BFB) plant sterols in differentiated Caco-2 cells and if the BFs counteracted the cytotoxic effect induced by COPs mixture (30 and 60 μM). BFs did not evoke cytotoxic effect in any of the tests carried out and they protected against the loss of intestinal cohesion, mitochondrial depolarization and necrosis induced by COPs mixture. Moreover, BFB sample protected from cell cycle arr…