Liver x receptor regulates arachidonic acid distribution and eicosanoid release in human macrophages: a key role for lysophosphatidylcholine acyltransferase 3.

OBJECTIVE: Liver X receptors (LXRs) are oxysterol-activated nuclear receptors that are highly expressed in macrophages and regulate lipid homeostasis and inflammation. Among putative LXR target genes, lysophosphatidylcholine acyltransferase 3 (LPCAT3) involved in the Lands cycle controls the fatty acid composition at the sn-2 position of glycerophospholipids and, therefore, the availability of fatty acids, such as arachidonic acid (AA), used for eicosanoid synthesis. The aim of our study was to determine whether LXRs could regulate the Lands cycle in human macrophages, to assess the consequences in terms of lipid composition and inflammatory response, and to work out the relative contribution of LPCAT3 to the observed changes. APPROACH AND RESULTS: Transcriptomic analysis revealed that LPCAT3 was upregulated by LXR agonists in human macrophages. Accordingly, LXR stimulation significantly increased lysophospholipid acyltransferase activity catalyzed by LPCAT3. Lipidomic analysis demonstrated that LXR activation increased the AA content in the polar lipid fraction, specifically in phosphatidylcholines. The LXR-mediated effects on AA distribution were abolished by LPCAT3 silencing, and a redistribution of AA toward the neutral lipid fraction was observed in this context. Finally, we observed that preconditioning of human macrophages by LXR agonist treatment increased the release of arachidonate-derived eicosanoids, such as prostaglandin E2 and thromboxane after lipopolysaccharide stimulation, with a significant attenuation by LPCAT3 silencing. CONCLUSIONS: Altogether, our data demonstrate that the LXR-mediated induction of LPCAT3 primes human macrophages for subsequent eicosanoid secretion by increasing the pool of AA, which can be mobilized from phospholipids.

Pravastatin reverses the membrane cholesterol reorganization induced by myocardial infarction within lipid rafts in CD14(+)/CD16(-) circulating monocytes.

Large numbers of monocytes are recruited in the infarcted myocardium. Their cell membranes contain cholesterol-rich microdomains called lipids rafts, which participate in numerous signaling cascades. In addition to its cholesterol-lowering effect, pravastatin has several pleiotropic effects and is widely used as secondary prevention treatment after myocardial infarction (MI). The aim of this study was to investigate the effects of pravastatin on the organization of cholesterol within monocyte membrane rafts from patients who had suffered myocardial infarction. Monocytes from healthy donors and acute MI patients were cultured with or without 4µM pravastatin. Lipid rafts were extracted by Lubrol WX, caveolae and flat rafts were separated using a modified sucrose gradient. Cholesterol level and caveolin-1 expression in lipid rafts were determined. In healthy donors, cholesterol was concentrated in flat rafts (63±3 vs 13±1%, p<0.001). While monocytes from MI patients presented similar cholesterol distribution in both caveolae and flat rafts. Cholesterol distribution was higher in flat rafts in healthy donors, compared to MI patients (63±3 vs 41±2%, p<0.001), with less distribution in caveolae (13±1 vs 34±2%, p<0.001). Pravastatin reversed the cholesterol distribution in MI patients cells between flat rafts (41±2 vs 66±3%, p<0.001) and caveolae (34±2 vs 18±1%, p<0.001). In conclusion, MI redistributes cholesterol from flat rafts to caveolae indicating monocyte membrane reorganization. In vitro pravastatin treatment restored basal conditions in MI monocytes, suggesting another effect of statins.

Substrate specificity overlap and interaction between adrenoleukodystrophy protein (ALDP/ABCD1) and adrenoleukodystrophy-related protein (ALDRP/ABCD2).

X-linked adrenoleukodystrophy (X-ALD) is a neurodegenerative disorder caused by mutations in the ABCD1 gene, which encodes a peroxisomal member of the ATP-binding cassette (ABC) transporter subfamily D called ALDP. ALDP is supposed to function as a homodimer allowing the entry of CoA-esters of very-long chain fatty acids (VLCFA) into the peroxisome, the unique site of their ß-oxidation. ALDP deficiency can be corrected by overexpression of ALDRP, its closest homolog. However, the exact nature of the substrates transported by ALDRP and its relationships with ALDP still remain unclear. To gain insight into the function of ALDRP, we used cell models allowing the induction in a dose-dependent manner of a wild type or a mutated non-functional ALDRP-EGFP fusion protein. We explored the consequences of the changes of ALDRP expression levels on the fatty acid content (saturated, monounsaturated, and polyunsaturated fatty acids) in phospholipids as well as on the levels of ß-oxidation of 3 suspected substrates: C26:0, C24:0, and C22:6n-3 (DHA). We found an inverse correlation between the fatty acid content of saturated (C26:0, C24:0) and monounsaturated (C26:1, C24:1) VLCFA and the expression level of ALDRP. Interestingly, we obtained a transdominant-negative effect of the inactive ALDRP-EGFP on ALDP function. This effect is due to a physical interaction between ALDRP and ALDP that we evidenced by proximity ligation assays and coimmunoprecipitation. Finally, the ß-oxidation assays demonstrate a role of ALDRP in the metabolism of saturated VLCFA (redundant with that of ALDP) but also a specific involvement of ALDRP in the metabolism of DHA.

PNPLA3 polymorphism influences liver fibrosis in unselected patients with type 2 diabetes.

CONTEXT: Recently, it has been shown that an allele in the adiponutrin (PNPLA3) gene was strongly associated with increased liver fat content (LFC) and liver fibrosis independent of visceral adiposity and insulin resistance. OBJECTIVE: In this study, we set out to determine whether the PNPLA3 rs738409 polymorphism was associated with liver fibrosis in unselected patients with type 2 diabetes. DESIGN, SETTING AND PARTICIPANTS: Two hundred and thirty-four patients with type 2 diabetes were included in this study. MAIN OUTCOME MEASURES: LFC was evaluated using (1) H-MR spectroscopy; fibrosis was measured using the non-invasive FibroTest(®). RESULTS: Advanced liver fibrosis (stage F2 or above) was observed in 10.2% of the patients while 149 (63.6%) patients had steatosis. The prevalence of steatosis and fibrosis was higher in minor G allele carriers than that in C allele homozygote carriers (70.3 vs 57.1%; P=0.04 and 14.7 vs 7.5%; P=0.07 respectively). In multivariate analysis, the predictive variables for advanced liver fibrosis were age (≥60) (P=0.005), sex (female) (P=0.004) and rs 738409 PNPLA3 polymorphism (P=0.01); body mass index (BMI) and LFC were not associated with liver fibrosis. CONCLUSIONS: This study confirms that in patients with type 2 diabetes who were not selected for liver abnormalities, liver fibrosis was related to the rs738409 polymorphism independent of BMI or LFC.

Induction of transglutaminase 2 by a liver X receptor/retinoic acid receptor alpha pathway increases the clearance of apoptotic cells by human macrophages.

RATIONALE: Liver X receptors (LXRs) are oxysterol-activated nuclear receptors that are involved in the control of cholesterol homeostasis and inflammatory response. Human monocytes and macrophages express high levels of these receptors and are appropriate cells to study the response to LXR agonists. OBJECTIVE: The purpose of this study was to identify new LXR targets in human primary monocytes and macrophages and the consequences of their activation. METHODS AND RESULTS: We show that LXR agonists significantly increase the mRNA and protein levels of the retinoic acid receptor (RAR)alpha in primary monocytes and macrophages. LXR agonists promote RARalpha gene transcription through binding to a specific LXR response element on RARalpha gene promoter. Preincubation of monocytes or macrophages with LXR agonists before RARalpha agonist treatment enhances synergistically the expression of several RARalpha target genes. One of these genes encodes transglutaminase (TGM)2, a key factor required for macrophage phagocytosis. Accordingly, the combination of LXR and RARalpha agonists at concentrations found in human atherosclerotic plaques markedly enhances the capabilities of macrophages to engulf apoptotic cells in a TGM2-dependent manner. CONCLUSIONS: These results indicate an important role for LXRs in the control of phagocytosis through an RARalpha-TGM2-dependent mechanism. A combination of LXR/RARalpha agonists that may operate in atherosclerosis could also constitute a promising strategy to improve the clearance of apoptotic cells by macrophages in other pathological situations.

Liver X receptor-mediated induction of cholesteryl ester transfer protein expression is selectively impaired in inflammatory macrophages.

OBJECTIVE: Cholesteryl ester transfer protein (CETP) is a target gene for the liver X receptor (LXR). The aim of this study was to further explore this regulation in the monocyte-macrophage lineage and its modulation by lipid loading and inflammation, which are key steps in the process of atherogenesis. METHODS AND RESULTS: Exposure of bone marrow-derived macrophages from human CETP transgenic mice to the T0901317 LXR agonist increased CETP, PLTP, and ABCA1 mRNA levels. T0901317 also markedly increased CETP mRNA levels and CETP production in human differentiated macrophages, whereas it had no effect on CETP expression in human peripheral blood monocytes. In inflammatory mouse and human macrophages, LXR-mediated CETP gene upregulation was inhibited, even though ABCA1, ABCG1, and SREBP1c inductions were maintained. The inhibition of CETP gene response to LXR agonists in inflammatory cells was independent of lipid loading (ie, oxidized LDL increased CETP production in noninflammatory macrophages with a synergistic effect of synthetic LXR agonists). CONCLUSIONS: LXR-mediated induction of human CETP expression is switched on during monocyte-to-macrophage differentiation, is magnified by lipid loading, and is selectively lost in inflammatory macrophages, which suggests that inflammatory cells may not increase the circulating CETP pool on LXR agonist treatment.

TRPC1 is regulated by caveolin-1 and is involved in oxidized LDL-induced apoptosis of vascular smooth muscle cells.

Oxidized low-density lipoprotein (oxLDL) induced-apoptosis of vascular cells may participate in plaque instability and rupture. We have previously shown that vascular smooth muscle cells (VSMC) stably expressing caveolin-1 were more susceptible to oxLDL-induced apoptosis than VSMC expressing lower level of caveolin-1, and this was correlated with enhanced Ca(2+) entry and pro-apoptotic events. In this study, we aimed to identify the molecular events involved in oxLDL-induced Ca(2+) influx and their regulation by the structural protein caveolin-1. In VSMC, transient receptor potential canonical-1 (TRPC1) silencing by ARN interference prevents the Ca(2+) influx and reduces the toxicity induced by oxLDL. Moreover, caveolin-1 silencing induces concomitant decrease of TRPC1 expression and reduces oxLDL-induced apoptosis of VSMC. OxLDL enhanced the cell surface expression of TRPC1, as shown by biotinylation of cell surface proteins, and induced TRPC1 translocation into caveolar compartment, as assessed by subcellular fractionation. OxLDL-induced TRPC1 translocation was dependent on actin cytoskeleton and associated with a dramatic rise of 7-ketocholesterol (a major oxysterol in oxLDL) into caveolar membranes, whereas the caveolar content of cholesterol was unchanged. Altogether, the reported results show that TRPC1 channels play a role in Ca(2+) influx and Ca(2+) homeostasis deregulation that mediate apoptosis induced by oxLDL. These data also shed new light on the role of caveolin-1 and caveolar compartment as important regulators of TRPC1 trafficking to the plasma membrane and apoptotic processes that play a major role in atherosclerosis.

Impact of asymmetric dimethylarginine on mortality after acute myocardial infarction.

OBJECTIVE: Asymmetrical dimethylarginine (ADMA) is an endogenous competitive inhibitor of nitric oxide (NO) synthases. From a prospective cohort of patients with acute myocardial infarction (MI), we aimed to analyze the predictive value of circulating ADMA concentrations on prognosis. METHODS AND RESULTS: Blood samples from 249 consecutive patients hospitalized for acute MI <24 hours were taken on admission. Serum levels of ADMA and its stereoisomer, symmetrical dimethylarginine (SDMA), were determined using high-performance liquid chromatography. The independent predictors of ADMA were glomerular filtration rate, female sex, and SDMA (R(2)=0. 25). Baseline ADMA levels were higher in patients who had died than in patients who were alive at 1 year follow-up (1.23 [0.98 to 1.56] versus 0.95 [0.77 to 1.20] micromol/L, P<0.001). By Cox multivariate analysis, the higher tertile of ADMA (median [interquartile range]: 1.45 [1.24 to 1.70] micromol/L) was a predictor for mortality (Hazard Ratio [95% CI], 4.83 [1.59 to 14.71]), when compared to lower tertiles, even when adjusted for potential confounders, such as acute therapy, biological, and clinical factors. CONCLUSIONS: Our study suggests that the baseline ADMA level has a strong prognostic value for mortality after MI, beyond traditional risk factors and biomarkers.

Differential regulation of cell death in head and neck cell carcinoma through alteration of cholesterol levels in lipid rafts microdomains.

Lipid rafts are cholesterol-enriched microdomains in the plasma membrane. They act as molecular platforms that spatially organize membrane receptor molecules and are involved in the transduction of various signaling pathways. We recently reported that in the radiosensitive squamous cell carcinoma SCC61 line, gamma-irradiation results in a rearrangement of the plasma membrane rafts and signaling platforms leading to radiation-induced apoptosis in a ceramide-dependent pathway. By contrast, this reorganization was found to be defective in the radioresistant counterpart cell line, SQ20B. As the cholesterol content of lipid rafts is two times higher in SQ20B compared with SCC61 cells, we investigated the modulation of these microdomains using methyl-beta-cyclodextrin (MbetaCDX), a widely used cholesterol-depleting agent, in order to disrupt raft organization in both cells. Here, we report that MbetaCDX treatment resulted in the triggering of apoptosis in SCC61 cells involving mitochondrial events and associated with the clustering of Fas, the formation of Fas-FADD complexes and the cleavage of procaspase 8. The ligand-independent activation of this death receptor was totally absent in SQ20B cells, which remained resistant to MbetaCDX-triggered apoptosis. However, treatment of SQ20B with MbetaCDX resulted in a ligand-independent activation of the epidermal growth factor receptor (EGFR) survival pathway, as evidenced by an increased tyrosine phosphorylation of EGFR. Taken altogether, our results indicate that lipid raft integrity is intimately involved in the triggering of apoptotic cell death and/or survival pathways in head and neck carcinoma cells.

Performance of N-terminal-pro-B-type natriuretic peptide in critically ill patients: a prospective observational cohort study.

INTRODUCTION: The purpose of this study was to assess the accuracy of N-terminal-pro-B-type natriuretic peptide (NT-proBNP) as a diagnostic tool to recognize acute respiratory failure of cardiac origin in an unselected cohort of critically ill patients. METHODS: We conducted a prospective observational study of medical ICU patients. NT-proBNP was measured at ICU admission, and diagnosis of cardiac dysfunction relied on the patient's clinical presentation and echocardiography. RESULTS: Of the 198 patients included in this study, 102 (51.5%) had evidence of cardiac dysfunction. Median NT-proBNP concentrations were 5,720 ng/L (1,430 to 15,698) and 854 ng/L (190 to 3,560) in patients with and without cardiac dysfunction, respectively (P < 0.0001). In addition, NT-proBNP concentrations were correlated with age (rho = 0.43, P < 0.0001) and inversely correlated with creatinine clearance (rho = -0.58, P < 0.0001). When evaluating the performance of NT-proBNP concentrations to detect cardiac dysfunction, the area under the receiver operating characteristic (ROC) curve was 0.76 (95% confidence interval (CI) 0.69 to 0.83). In addition, a stepwise logistic regression model revealed that NT-proBNP (odds ratio (OR) = 1.01 per 100 ng/L, 95% CI 1.002 to 1.02), electrocardiogram modifications (OR = 11.03, 95% CI 5.19 to 23.41), and severity assessed by organ system failure score (OR = 1.63 per point, 95% CI 1.17 to 2.41) adequately predicted cardiac dysfunction. The area under the ROC curve of this model was 0.83 (95% CI 0.77 to 0.90). CONCLUSIONS: NT-proBNP measured at ICU admission might represent a useful marker to exclude cardiac dysfunction in critically ill patients.

Asymmetric dimethylarginine (ADMA) and hyperhomocysteinemia in patients with acute myocardial infarction.

OBJECTIVES: We sought to investigate the association between increased levels of asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, and total plasma homocysteinemia (tHcy) in patients with acute myocardial infarction (AMI). DESIGN AND METHODS: In 138 patients hospitalized for AMI <24 h on admission, serum levels of ADMA, its symmetric stereoisomer (SDMA) and tHcy were measured. RESULTS: ADMA was positively associated with SDMA (p<0.001) and tHcy (p=0.03) but not with estimated glomerular filtration rates (eGFR, p=0.96), while tHcy strongly correlated with eGFR (p=0.002) and SDMA (p<0.001). By multiple linear regression, SDMA but not ADMA was independently associated with tHcy (p=0.005). CONCLUSION: Our findings suggest that, in AMI patients, hyperhomocysteinemia is indirectly related to ADMA levels via renal function. Moreover, ADMA level was independent of traditional cardiovascular risk factors in AMI patients. Interestingly, our findings suggest that SDMA could be a good risk indicator for cardiovascular disease in AMI patients.

The changes in NT-proBNP plasma concentrations during dialysis are highly dependent of the dialysis membrane ultrafiltration coefficient.

BACKGROUND: NT-proBNP is a powerful marker with diagnostic and pronostic value for heart failure. It is of particular interest in patients with end-stage renal disease who are at high risk for heart failure. The aim of this study was to investigate the effect of hemodialysis on plasma NT-proBNP concentrations. METHODS: NT-proBNP concentration was measured in 67 patients before and after hemodialysis. RESULTS: In the 20 patients dialyzed with a membrane whose ultrafiltration coefficient was below or equal to12, NT-proBNP concentration was comparable after and before dialysis (16611+/-21024 vs. 15216+/-19027 pg/ml, NS). At the opposite, in the 47 patients dialyzed with a membrane whose ultrafiltration coefficient was above or equal to 40, NT proBNP concentration was 35% lower after dialysis compared to before dialysis (11983+/-21819 vs. 18574+/-31862 pg/ml, p<0.0001). CONCLUSIONS: In patients dialyzed with a membrane whose ultrafiltration coefficient is high, dialysis is likely to decrease results by one third. Thus sampling blood before dialysis in hemodialyzed patients appears as the best time to stratify the cardiovascular risk in these patients.

Adiponectin is an important determinant of apoA-I catabolism.

OBJECTIVE: Plasma concentration of adiponectin is positively correlated with high-density lipoprotein (HDL) cholesterol level. However, the role of adiponectin on HDL metabolism remains unknown. This prompted us to perform an in vivo kinetic study of apoA-I, the main apolipoprotein of HDL, using stable isotopes, in 22 subjects with a wide range of plasma adiponectin, including 11 patients with metabolic syndrome (8 with type 2 diabetes, 3 without type 2 diabetes) and 11 normal individuals. METHODS AND RESULTS: In the 22 studied subjects, plasma adiponectin levels ranged from 2.57 to 14.44 microg/mL and apoA-I fractional catabolic rate (FCR) values ranged from 0.142 to 0.340 day(-1). A strong negative correlation was found between adiponectin and apoA-I FCR (r=-0.66, P<0.001) in the whole studied population and, to a similar extent, in patients with metabolic syndrome (r=-0.73, P=0.010) and normal subjects (r=-0.68, P=0.020), separately. In multivariable analysis, apoA-I FCR was associated negatively with adiponectin (P=0.005) and positively with HDL triglycerides/cholesterol ratio (P=0.006), but not with age, sex, body mass index (BMI), waist circumference, plasma triglycerides, HDL cholesterol, fasting glycemia, and QUICKI. Both adiponectin and HDL triglycerides/cholesterol ratio explained 62% of the variance of apoA-I FCR and adiponectin on its own explained 43%. CONCLUSIONS: Our kinetic study shows a strong negative correlation between adiponectin and apoA-I FCR, which can explain the positive link between HDL cholesterol and adiponectin. This association is independent of obesity, insulin resistance, and the content of triglycerides within HDL particles. These data suggest that adiponectin may have a direct role on HDL catabolism.

Evaluation of the VITROS chemistry products dHDL slides for direct measurement of high density lipoprotein cholesterol.

BACKGROUND: We evaluated the new VITROS direct high density lipoprotein cholesterol (dHDL) slide assay, based on the precipitation of apolipoprotein B-containing lipoproteins by phosphotungstic acid/magnesium chloride (PTA/MgCl2). METHODS: We determined linearity, within-run and between-run imprecision for the VITROS dHDL slide assay, and compared it to the RANDOX two-step PTA/MgCl2 method for 300 fresh sera. Moreover, triglyceride and cholesterol interference were tested. RESULTS: The VITROS dHDL slide assay was linear from 0 to 3.13 mmol/l. Within-run and between-run imprecision were 1.6%, 1.8%, 3.3% and 3.2% for target values at 1.00 and 1.40 mmol/l, respectively. For 300 fresh serum samples, the linear regression equation between the VITROS dHDL slide assay (y) and the RANDOX PTA/MgCl2 2 method (x) was: y (mmol/l)=0.934 x+0.043 (CI=0.916-0.952 for slope and 0.017-0.069 for intercept) . The bias of the VITROS assay compared to the RANDOX PTA/MgCl2 method was less than 5% for HDL cholesterol concentrations used for medical decision (1.04 and 1.50 mmol/l). Total error remained below 13% for triglyceride and LDL cholesterol concentrations below 6.6 mmol/l. CONCLUSION: The VITROS dHDL slide assay is rapid, linear over a broad range of concentrations, and satisfies the National Cholesterol Education Program goals for precision and accuracy.

Expression of the pregnane X receptor in mice antagonizes the cholic acid-mediated changes in plasma lipoprotein profile.

OBJECTIVE: Modification of lipoprotein metabolism by bile acids has been mainly explained by activation of the farnesyl X receptor (FXR). The aim of the present study was to determine the relative contribution of the pregnane X receptor (PXR), another bile acid-activated nuclear receptor to changes in plasma lipoprotein profile. METHODS AND RESULTS: Wild-type mice, Pxr-deficient mice, and Pxr-null mice expressing human PXR (Pxr-null SXR-Tg mice) were fed a cholic acid-containing diet, and consequences on plasma lipoprotein profiles and target gene expression were assessed. Cholic acid produced significant decreases in high-density lipoprotein (HDL) cholesterol, plasma apolipoprotein (apo)A-I and hepatic apoA-I mRNA in wild-type mice. Interestingly, the effect of cholic acid was significantly more pronounced in Pxr-deficient mice, indicating that PXR contributes to the weakening of the effect of bile acids on lipoprotein metabolism. Reciprocally, changes in HDL/apoA-I profiles were abolished in Pxr-null SXR-Tg mice in which PXR-responsive genes, particularly those involved in bile acid detoxification were readily activated after cholic acid treatment. CONCLUSIONS: PXR expression in mice antagonizes the cholic acid-mediated downregulation of plasma HDL cholesterol and apoA-I, and magnification of PXR/SXR-mediated changes may constitute a new mean to counteract the effects of bile acids on plasma lipoproteins.

Cisplatin-induced CD95 redistribution into membrane lipid rafts of HT29 human colon cancer cells.

We have shown previously that the death receptor CD95 could contribute to anticancer drug-induced apoptosis of colon cancer cells. In addition, anticancer drugs cooperate with CD95 cognate ligand or agonistic antibodies to trigger cancer cell apoptosis. In the present study, we show that the anticancer drug cisplatin induces clustering of CD95 at the surface of the human colon cancer cell line HT29, an event inhibited by the inhibitor of acid sphingomyelinase (aSMase) imipramine. The cholesterol sequestering agent nystatin also prevents cisplatin-induced CD95 clustering and decreases HT29 cell sensitivity to cisplatin-induced apoptosis and the synergy between cisplatin and anti-CD95 agonistic antibodies. CD95, together with the adaptor molecule Fas-associated death domain and procaspase-8, is redistributed into cholesterol- and sphingolipid-enriched cell fractions after cisplatin treatment, suggesting plasma membrane raft involvement. Interestingly, nystatin prevents the translocation of the aSMase to the extracellular surface of plasma membrane and the production of ceramide, suggesting that these early events require raft integrity. In addition, nystatin prevents cisplatin-induced transient increase in plasma membrane fluidity that could be required for CD95 translocation. Together, these results demonstrate that cisplatin activates aSMase and induces ceramide production, which triggers the redistribution of CD95 into the plasma membrane rafts. Such redistribution contributes to cell death and sensitizes tumor cells to CD95-mediated apoptosis.

Redistribution of CD95, DR4 and DR5 in rafts accounts for the synergistic toxicity of resveratrol and death receptor ligands in colon carcinoma cells.

The natural phytoalexin resveratrol (3, 5, 4'-trihydroxystilbene) exhibits both chemopreventive and antitumor activities through a variety of mechanisms. We have shown previously that resveratrol-induced apoptosis of a human colon cancer cell line involved the redistribution of CD95 (Fas/Apo-1) into lipid rafts. Here, we show that, in colon cancer cells that resist to resveratrol-induced apoptosis, the polyphenol also induces a redistribution of death receptors into lipid rafts. This effect sensitizes these tumor cells to death receptor-mediated apoptosis. In resveratrol-treated cells, tumor necrosis factor (TNF), anti-CD95 antibodies and TNF-related apoptosis-inducing ligand (TRAIL) activate a caspase-dependent death pathway that escapes Bcl-2-mediated inhibition. Resveratrol does not enhance the number of death receptors at the surface of tumor cells but induces their redistribution into lipid rafts and facilitates the caspase cascade activation in response to death receptor stimulation. The cholesterol sequestering agent nystatin prevents resveratrol-induced death receptor redistribution and cell sensitization to death receptor stimulation. Thus, whatever its ability to induce apoptosis in a tumor cell, resveratrol induces redistribution of death receptors into lipid rafts. This redistribution sensitizes the cells to death receptor stimulation. Such a sensitizing effect may be of therapeutic interest if TRAIL agonists are introduced in clinics.

Comparison of apolipoprotein B100 metabolism between continuous subcutaneous and intraperitoneal insulin therapy in type 1 diabetes.

OBJECTIVE: In type 1 diabetic patients, the replacement of s.c. insulin infusion with i.p. insulin infusion restores the normal physiological gradient between the portal vein and the peripheral circulation, which is likely to modify lipoprotein metabolism. DESIGN: To check this hypothesis, we performed two apolipoprotein (apo) B100 kinetic studies in seven type 1 diabetic patients, first under s.c. insulin infusion and then 3 months after the beginning of i.p. insulin infusion. RESULTS: Glycemic control was similar under s.c. insulin infusion and i.p. insulin infusion, as assessed by glycated hemoglobin A1c and the capillary glycemic curve determined during the kinetic study. Very low-density and intermediate-density lipoprotein apoB100 pool size, production rate, and fractional catabolic rate (FCR) were similar under s.c. insulin infusion and i.p. insulin infusion. The low-density lipoprotein apoB100 FCR tended to decrease under ip insulin (0.45 +/- 0.06 vs. 0.55 +/- 0.11 pool/d), but the difference did not reach statistical significance (95% confidence interval for the difference, -0.33, 0.11). The low-density lipoprotein apoB100 pool size and production rate remained unchanged under i.p. insulin infusion compared with s.c. insulin infusion. CONCLUSION: In type 1 diabetic patients, the replacement of s.c. insulin infusion with i.p. insulin infusion does not induce profound modifications of apoB100-containing lipoprotein production and FCRs.

Decreased plasma adiponectin concentrations are closely related to steatosis in hepatitis C virus-infected patients.

OBJECTIVES: The mechanisms underlying steatosis during hepatitis C virus (HCV) infection are complex and multifactorial. Obesity is a well-recognized risk factor for the development of steatosis in chronic hepatitis C infection. The aim of our study was to investigate the role of adipocytokines in HCV-related steatosis. Therefore, we hypothesized that the endocrine function of adipose tissue could be, in part, responsible for HCV-related steatosis. Seventy-one consecutive untreated chronic hepatitis C patients were studied to assess the effects of adipocytokines, body mass index (BMI), age, and HCV genotype on steatosis. We used ELISA to determine serum adiponectin, leptin, and soluble TNF receptors I and II concentrations. RESULTS: Steatosis was observed in 42 (59.1%) patients. BMI was significantly associated with leptin (r = 0.64; P = 0.0001) and was border significantly associated with adiponectin concentrations (r = -0.22; P = 0.06). In univariate analyses, age, HCV genotype 3, BMI, increased leptin level, increased insulin level, and decreased adiponectin concentration were associated with steatosis. In multivariate analysis, steatosis was significantly associated with low adiponectin concentration, age, HCV genotype 3, and aspartate aminotransferase (ASAT) level, whereas steatosis was not associated with leptin, insulin, and BMI. CONCLUSION: In chronic HCV patients, hypoadiponectinemia is significantly associated with the development of liver steatosis. The fact that the plasma levels of adiponectin inversely correlate with steatosis in HCV-infected subjects suggests that hypoadiponectinemia may contribute to hepatic steatosis progression and liver injury in this population. One practical implication is that therapy to increase circulating adiponectin concentration, such as overweight reduction or thiazolidinediones, provides the potential to improve steatosis in chronic hepatitis C infection.