Genetique moleculaire de l'hemochromatose idiopathique : approche par le polymorphisme de restriction des genes des sous-unites H de la ferritine, et des genes HLA de classe I

CNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

The human hepatocyte cell lines IHH and HepaRG:models to study glucose, lipid and lipoprotein metabolism

Metabolic diseases reach epidemic proportions. A better knowledge of the associated alterations in the metabolic pathways in the liver is necessary. These studies need in vitro human cell models. Several human hepatoma models are used, but the response of many metabolic pathways to physiological stimuli is often lost. Here, we characterize two human hepatocyte cell lines, IHH and HepaRG, by analysing the expression and regulation of genes involved in glucose and lipid metabolism. Our results show that the glycolysis pathway is activated by glucose and insulin in both lines. Gluconeogenesis gene expression is induced by forskolin in IHH cells and inhibited by insulin in both cell lines. The lipogenic pathway is regulated by insulin in IHH cells. Finally, both cell lines secrete apolipoprotein B-containing lipoproteins, an effect promoted by increasing glucose concentrations. These two human cell lines are thus interesting models to study the regulation of glucose and lipid metabolism

Retrograde cholesterol transport in the human Caco-2/TC7 cell line: A model to study trans-intestinal cholesterol excretion in atherogenic and diabetic dyslipidemia

The dyslipidemia associated with type 2 diabetes is a major risk factor for the development of atherosclerosis. Trans-intestinal cholesterol excretion (TICE) has recently been shown to contribute, together with the classical hepatobiliary route, to fecal cholesterol excretion and cholesterol homeostasis. The aim of this study was to develop an in vitro cell model to investigate enterocyte-related processes of TICE. Differentiated Caco-2/TC7 cells were grown on transwells and incubated basolaterally (blood side) with human plasma and apically (luminal side) with lipid micelles. Radioactive and fluorescent cholesterol tracers were used to investigate cholesterol uptake at the basolateral membrane, intracellular distribution and apical excretion. Our results show that cholesterol is taken up at the basolateral membrane, accumulates intracellularly as lipid droplets and undergoes a cholesterol acceptor-facilitated and progressive excretion through the apical membrane of enterocytes. The overall process is abolished at 4 A degrees C, suggesting a biologically active phenomenon. Moreover, this trans-enterocytic retrograde cholesterol transport displays some TICE features like modulation by PCSK9 and an ABCB1 inhibitor. Finally, we highlight the involvement of microtubules in the transport of plasma cholesterol from basolateral to apical pole of enterocytes. The human Caco-2/TC7 cell line appears a good in vitro model to investigate the enterocytic molecular mechanisms of TICE, which may help to identify intestinal molecular targets to enhance reverse cholesterol transport and fight against dyslipidemia

Liver X Receptor Regulates Triglyceride Absorption Through Intestinal Down-regulation of Scavenger Receptor Class B, Type 1

BACKGROUND &amp; AIMS: Reducing postprandial triglyceridemia may be a promising strategy to lower the risk of cardiovascular disorders associated with obesity and type 2 diabetes. In enterocytes, scavenger receptor class B, type 1 (SR-B1, encoded by SCARB1) mediates lipid-micelle sensing to promote assembly and secretion of chylomicrons. The nuclear receptor subfamily 1, group H, members 2 and 3 (also known as liver X receptors [LXRs]) regulate genes involved in cholesterol and fatty acid metabolism. We aimed to determine whether intestinal LXRs regulate triglyceride absorption. METHODS: C57BL/6J mice were either fed a cholesterol-enriched diet or given synthetic LXR agonists (GW3965 or T0901317). We measured the production of chylomicrons and localized SR-B1 by immunohistochemistry. Mechanisms of postprandial triglyceridemia and SR-B1 regulation were studied in Caco-2/TC7 cells incubated with LXR agonists. RESULTS: In mice and in the Caco-2/TC7 cell line, LXR agonists caused localization of intestinal SR-B1 from apical membranes to intracellular organelles and reduced chylomicron secretion. In Caco-2/TC7 cells, LXR agonists reduced SR-B1-dependent lipidic-micelle-induced Erk phosphorylation. LXR agonists also reduced intracellular trafficking of the apical apolipoprotein B pool toward secretory compartments. LXR reduced levels of SR-B1 in Caco-2/TC7 cells via a post-transcriptional mechanism that involves microRNAs. CONCLUSION: In Caco-2/TC7 cells and mice, intestinal activation of LXR reduces the production of chylomicrons by a mechanism dependent on the apical localization of SR-B1.</p

The PPARγ pathway determines electrophysiological remodelling and arrhythmia risks in DSC2 arrhythmogenic cardiomyopathy

International audienceNo abstract availabl

Physiological and metabolic responses of freshwater and brackish strains of Microcystis aeruginosa acclimated to a salinity gradient: insight into salt tolerance

International audienceProliferation of microcystin (MC)-producing Microcystis aeruginosa in brackish waters has been described in several locations and represents a new concern for public and environmental health. While the impact of a sudden salinity increase on M. aeruginosa physiology has been studied, less is known about the mechanisms involved in salt tolerance after acclimation. This study aims to compare the physiological responses of two strains of M. aeruginosa (PCC 7820 and PCC 7806), which were isolated from contrasted environments, to increasing salinities. After acclimation, growth and MC production rates were determined and metabolomic analyses were conducted. For both strains, salinity decreased the biovolume, growth, and MC production rates and induced the accumulation of polyunsaturated lipids identified as monogalactosyldiacylglycerol. The distinct salt tolerances (7.5 and 16.9) obtained between the freshwater (PCC 7820) and the brackish-water (PCC 7806) strains suggested different strategies to cope with the osmotic pressure, as revealed by targeted and untargeted metabolomic analyses. An accumulation of trehalose as the main compatible solute was obtained in the freshwater strain, while sucrose was mainly accumulated in the brackish one. Moreover, distinct levels of glycine betaine and proline accumulation were noted. Altogether, metabolomic analysis illustrated a strain-specific response to salt tolerance, involving compatible solute production. IMPORTANCE Blooms of Microcystis aeruginosa and the production of microcystins are major issues in eutrophic freshwater bodies. Recently, an increasing number of proliferations of M. aeruginosa in brackish water has been documented. The occurrence of both M. aeruginosa and microcystins in coastal areas represents a new threat for human and environmental health. In order to better describe the mechanisms involved in Microcystis sp. proliferation in brackish water, this study used two M. aeruginosa strains isolated from fresh and brackish waters. High salinity reduced the growth rate and microcystin production rate of M. aeruginosa. In order to cope with higher salinities, the strains accumulated different cyanobacterial compatible solutes, as well as unsaturated lipids, explaining their distinct salt tolerance

The oral Ca/calmodulin‐dependent kinase II inhibitor RA608 improves contractile function and prevents arrhythmias in heart failure

Aims Excessive activation of Ca/calmodulin-dependent kinase II (CaMKII) is of critical importance in heart failure (HF) and atrial fibrillation. Unfortunately, lack of selectivity, specificity, and bioavailability have slowed down development of inhibitors for clinical use. We investigated a novel CaMKII delta/CaMKII-selective, ATP-competitive, orally available CaMKII inhibitor (RA608) on right atrial biopsies of 119 patients undergoing heart surgery. Furthermore, we evaluated its oral efficacy to prevent deterioration of HF in mice after transverse aortic constriction (TAC). Methods and results In human atrial cardiomyocytes and trabeculae, respectively, RA608 significantly reduced sarcoplasmic reticulum Ca leak, reduced diastolic tension, and increased sarcoplasmic reticulum Ca content. Patch-clamp recordings confirmed the safety of RA608 in human cardiomyocytes. C57BL6/J mice were subjected to TAC, and left ventricular function was monitored by echocardiography. Two weeks after TAC, RA608 was administered by oral gavage for 7 days. Oral RA608 treatment prevented deterioration of ejection fraction. At 3 weeks after TAC, ejection fraction was 46.1 +/- 3.7% (RA608) vs. 34.9 +/- 2.6% (vehicle), n = 9 vs.n = 12, P < 0.05, ANOVA, which correlated with significantly less CaMKII autophosphorylation at threonine 287. Moreover, a single oral dose significantly reduced inducibility of atrial and ventricular arrhythmias in CaMKII delta transgenic mice 4 h after administration. Atrial fibrillation was induced in 6/6 mice for vehicle vs. 1/7 for RA608,P < 0.05, 'n - 1' chi(2) test. Ventricular tachycardia was induced in 6/7 for vehicle vs. 2/7 for RA608,P < 0.05, 'n - 1' chi(2) test. Conclusions RA608 is the first orally administrable CaMKII inhibitor with potent efficacy in human myocytes. Moreover, oral administration potently inhibits arrhythmogenesis and attenuates HF development in micein vivo

Genotoxicant accumulation and cellular defence activation in bivalves chronically exposed to waterborne contaminants from the Seine River

International audienc

P2Y13 Receptor is Critical for Reverse Cholesterol Transport

A major atheroprotective functionality of high-density lipoproteins (HDLs) is to promote "reverse cholesterol transport" (RCT). In this process, HDLs mediate the efflux and transport of cholesterol from peripheral cells and its subsequent transport to the liver for further metabolism and biliary excretion. We have previously demonstrated in cultured hepatocytes that P2Y(13) (purinergic receptor P2Y, G protein coupled, 13) activation is essential for HDL uptake but the potential of P2Y(13) as a target to promote RCT has not been documented. Here, we show that P2Y(13)-deficient mice exhibited a decrease in hepatic HDL cholesterol uptake, hepatic cholesterol content, and biliary cholesterol output, although their plasma HDL and other lipid levels were normal. These changes translated into a substantial decrease in the rate of macrophage-to-feces RCT. Therefore, hallmark features of RCT are impaired in P2Y(13)-deficient mice. Furthermore, cangrelor, a partial agonist of P2Y(13), stimulated hepatic HDL uptake and biliary lipid secretions in normal mice and in mice with a targeted deletion of scavenger receptor class B type I (SR-BI) in liver (hypomSR-BI- knockout(liver)) but had no effect in P2Y(13) knockout mice, which indicate that P2Y(13)-mediated HDL uptake pathway is independent of SR-BI mediated HDL selective cholesteryl ester uptake. Conclusion: These results establish P2Y(13) as an attractive novel target for modulating RCT and support the emerging view that steady-state plasma HDL levels do not necessarily reflect the capacity of HDL to promote RCT. (HEPATOLOGY 2010;52:1477-1483