Link between Intestinal CD36 Ligand Binding and Satiety Induced by a High Protein Diet in Mice

CD36 is a ubiquitous membrane glycoprotein that binds long-chain fatty acids. The presence of a functional CD36 is required for the induction of satiety by a lipid load and its role as a lipid receptor driving cellular signal has recently been demonstrated. Our project aimed to further explore the role of intestinal CD36 in the regulation of food intake. Duodenal infusions of vehicle or sulfo-N-succinimidyl-oleate (SSO) was performed prior to acute infusions of saline or Intralipid (IL) in mice. Infusion of minute quantities of IL induced a decrease in food intake (FI) compared to saline. Infusion of SSO had the same effect but no additive inhibitory effect was observed in presence of IL. No IL- or SSO-mediated satiety occurred in CD36-null mice. To determine whether the CD36-mediated hypophagic effect of lipids was maintained in animals fed a satietogen diet, mice were subjected to a High-Protein diet (HPD). Concomitantly with the satiety effect, a rise in intestinal CD36 gene expression was observed. No satiety effect occurred in CD36-null mice. HPD-fed WT mice showed a diminished FI compared to control mice, after saline duodenal infusion. But there was no further decrease after lipid infusion. The lipid-induced decrease in FI observed on control mice was accompanied by a rise in jejunal oleylethanolamide (OEA). Its level was higher in HPD-fed mice than in controls after saline infusion and was not changed by lipids. Overall, we demonstrate that lipid binding to intestinal CD36 is sufficient to produce a satiety effect. Moreover, it could participate in the satiety effect induced by HPD. Intestine can modulate FI by several mechanisms including an increase in OEA production and CD36 gene expression. Furthermore, intestine of mice adapted to HPD have a diminished capacity to modulate their food intake in response to dietary lipids

Influence de l expression de l ATP synthétase sur la composition lipidique des membranes bactériennes chez Escherichia coli (Identification et quantification relative des phospholipides et acides gras constitutifs par spectrométrie de masse)

Depuis quelques années, la recherche de préférences lipidiques de protéines et/ou d enzymes membranaires suscite un intérêt grandissant, ces phénomènes d affinité étant susceptibles d induire la formation de domaines lipidiques dans les membranes biologiques. C est pourquoi, nous avons cherché à savoir si l ATP-synthétase, protéine membranaire, était capable d induire des domaines lipidiques dans un modèle cellulaire, la bactérie d E. coli. Ainsi, l influence de l expression de cette protéine a été évaluée au moyen de 4 souches bactériennes; la souche sauvage ainsi que 3 souches génétiquement modifiées présentant des taux variables d enzyme. La méthodologie analytique développée fait appel à diverses techniques de MS. Les couplages LC-MS et GC-MS sont mis à profit pour l analyse des phospholipides et des acides gras constitutifs. Cette approche a permis d identifier l ensemble des phospholipides, de déterminer la structure fine des acides gras les constituants ainsi que de localiser chaque acide.For years, investigations of growing interest deal with the potential lipids preference of membrane proteins and/or enzymes, these affinity phenomenons are supposed to induce the formation of lipids domains also called lipids rafts inside biological membranes. This thesis focused on the ability of ATP-synthetase, a membrane protein, to induce lipids domains in a cellular model, the E. coli bacteria. Hence, 4 bacterial strains were studied to evaluate the influence of protein expression, a wild type and three genetically modified strains with variable enzyme rates. Analytical methodologies were developed for this purpose and involved various MS techniques. Then, LC-MS and GC-MS techniques were used for the analysis of phospholipids and constitutive fatty acids, respectively. This approach provided the identification of all the phospholipids. Moreover, the structure of the constitutive fatty acids and their location on the glycerol backbone were determined.ROUEN-BU Sciences (764512102) / SudocROUEN-BU Sciences Madrillet (765752101) / SudocSudocFranceF

Erratum: Lipid composition of membranes of Escherichia coli by liquid chromatography/tandem mass spectrometry using negative electrospray ionisation

International audienc

Lipid composition of membranes ofEscherichia coli by liquid chromatography/tandem mass spectrometry using negative electrospray ionization

International audienceA liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method using reversed-phase chromatography was developed for the analysis of phospholipids from bacterial extracts of a wild-type strain of Escherichia coli. Product ion mass spectra from [M--H](-) precursor ions allowed an identification of individual phospholipid species that includes both fatty acid composition and fatty acyl location on the glycerol backbone using diagnostic product ions. Thus, complete assignment, including sn-1/sn-2 fatty acyl position, was achieved for this strain of E. coli. In addition, the phospholipids were quantified relative to one another using an internal standard method

Overexpression of the epidermis-specific homeodomain-leucine zipper IV transcription factor OUTER CELL LAYER1 in maize identifies target genes involved in lipid metabolism and cuticle biosynthesis

L'article original est publié par The American Society of Plant BiologistsInternational audienceTranscription factors of the homeodomain-leucine zipper IV (HD-ZIP IV) family play crucial roles in epidermis-related processes. To gain further insight into the molecular function of OUTER CELL LAYER1 (OCL1), 14 target genes up- or down-regulated in transgenic maize (Zea mays) plants overexpressing OCL1 were identified. The 14 genes all showed partial coexpression with OCL1 in maize organs, and several of them shared preferential expression in the epidermis with OCL1. They encoded proteins involved in lipid metabolism, defense, envelope-related functions, or cuticle biosynthesis and include ZmWBC11a (for white brown complex 11a), an ortholog of AtWBC11 involved in the transport of wax and cutin molecules. In support of the annotations, OCL1-overexpressing plants showed quantitative and qualitative changes of cuticular wax compounds in comparison with wild-type plants. An increase in C24 to C28 alcohols was correlated with the transcriptional up-regulation of ZmFAR1, coding for a fatty acyl-coenzyme A reductase. Transcriptional activation of ZmWBC11a by OCL1 was likely direct, since transactivation in transiently transformed maize kernels was abolished by a deletion of the activation domain in OCL1 or mutations in the L1 box, a cis-element bound by HD-ZIP IV transcription factors. Our data demonstrate that, in addition to AP2/EREBP and MYB-type transcription factors, members of the HD-ZIP IV family contribute to the transcriptional regulation of genes involved in cuticle biosynthesis

Composition of the different diets.

<p>Composition of the different diets.</p

Experimental protocol and infusions.

<p>Experimental protocol and infusions.</p

Food intake and CD36-encoding mRNA level in segments of the small intestine after intra-duodenal infusions.

<p>(<b>A</b>): Food intakes were measured 30 min, 1hr and 2 hr after the end of the infusion and were not cumulated. Each type of infusion was performed several times on the same animal. * P<0.05 relatively to saline infusion (for each period of time). The dotted line corresponds to the reference value at each time (mice infused with saline). The number of experiments (n = 16) corresponds to different animals. (<b>B</b>): The expression of the gene encoding CD36 was measured by RT-qPCR on RNA samples obtained 45 min after the end of the infusion. Results were expressed as mean ± SEM (CD36 <i>versus</i> L19). * P<0.05 differences between saline and IL infusions for each part of the small intestine.</p

Wild-type and CD36-invalidated mice on Protein-enriched (HP) diet.

<p>(<b>A-B</b>): Food intake relative to body weight during 12 days of standard or HP diets. (A) corresponds to wild-type (WT) mice and (B) to CD36-invalidated mice (<b>C</b>): CD36-encoding mRNA level (relative to L19 gene) in the duodenum and proximal jejunum of WT mice fed standard or HP diet. (≠ P<0.05 relative to duodenum control; * P<0.05 relative to jejunum control; n = 5 to 8). (<b>D</b>): Western Blot analyses of proteins prepared from proximal jejunum of WT mice on standard (Control) or HP diet for 4 and 12 days<b>.</b> Each lane corresponded to a different mouse. (<b>E</b>): Plasma triglycerides measured in control and HPD-fed WT mice. a: P<0.05 differences between control and HPD mice at each period of time; b: P<0.05 relatively to HP 4days. (F): Plasma insulin measured in control and HPD-fed WT mice. a: P<0.05 differences between control and HPD mice at each period of time; b: P<0.05 relatively to HP 4days.</p

Comparison between WT mice on standard chow (control) and HPD after saline or IL infusion.

<p>Mice were fed either standard chow or HP diet 12 days before surgery. Saline and IL infusions were performed after one-week recovery. (<b>A</b>): Food intakes were measured 30 min after saline and IL infusions (n = 29 for CT and 17 for HP). (<b>B/C</b>): Duodenal CD36 mRNA level (B) and jejunal OEA concentration (C) were measured 45 min after the end of saline and IL infusions. a: P<0.05 relatively to saline infusion in control group.</p