Role of Esrrg in the Fibrate-Mediated Regulation of Lipid Metabolism Genes in Human ApoA-I Transgenic Mice

We have used a new ApoA-I transgenic mouse model to identify by global gene expression profiling, candidate genes that affect lipid and lipoprotein metabolism in response to fenofibrate treatment. Multilevel bioinformatical analysis and stringent selection criteria (2-fold change, 0% false discovery rate) identified 267 significantly changed genes involved in several molecular pathways. The fenofibrate-treated group did not have significantly altered levels of hepatic human APOA-I mRNA and plasma ApoA-I compared with the control group. However, the treatment increased cholesterol levels to 1.95-fold mainly due to the increase in high-density lipoprotein (HDL) cholesterol. The observed changes in HDL are associated with the upregulation of genes involved in phospholipid biosynthesis and lipid hydrolysis, as well as phospholipid transfer protein. Significant upregulation was observed in genes involved in fatty acid transport and β-oxidation, but not in those of fatty acid and cholesterol biosynthesis, Krebs cycle and gluconeogenesis. Fenofibrate changed significantly the expression of seven transcription factors. The estrogen receptor-related gamma gene was upregulated 2.36-fold and had a significant positive correlation with genes of lipid and lipoprotein metabolism and mitochondrial functions, indicating an important role of this orphan receptor in mediating the fenofibrate-induced activation of a specific subset of its target genes.National Institutes of Health (HL48739 and HL68216); European Union (LSHM-CT-2006-0376331, LSHG-CT-2006-037277); the Biomedical Research Foundation of the Academy of Athens; the Hellenic Cardiological Society; the John F Kostopoulos Foundatio

Transcriptional Profiling Uncovers a Network of Cholesterol-Responsive Atherosclerosis Target Genes

Despite the well-documented effects of plasma lipid lowering regimes halting atherosclerosis lesion development and reducing morbidity and mortality of coronary artery disease and stroke, the transcriptional response in the atherosclerotic lesion mediating these beneficial effects has not yet been carefully investigated. We performed transcriptional profiling at 10-week intervals in atherosclerosis-prone mice with human-like hypercholesterolemia and a genetic switch to lower plasma lipoproteins (Ldlr−/−Apo100/100 Mttpflox/flox Mx1-Cre). Atherosclerotic lesions progressed slowly at first, then expanded rapidly, and plateaued after advanced lesions formed. Analysis of lesion expression profiles indicated that accumulation of lipid-poor macrophages reached a point that led to the rapid expansion phase with accelerated foam-cell formation and inflammation, an interpretation supported by lesion histology. Genetic lowering of plasma cholesterol (e.g., lipoproteins) at this point all together prevented the formation of advanced plaques and parallel transcriptional profiling of the atherosclerotic arterial wall identified 37 cholesterol-responsive genes mediating this effect. Validation by siRNA-inhibition in macrophages incubated with acetylated-LDL revealed a network of eight cholesterol-responsive atherosclerosis genes regulating cholesterol-ester accumulation. Taken together, we have identified a network of atherosclerosis genes that in response to plasma cholesterol-lowering prevents the formation of advanced plaques. This network should be of interest for the development of novel atherosclerosis therapies

Molecular characterization of new selective peroxisome proliferator–activated receptor {gamma} modulators with angiotensin receptor blocking activity

Selective peroxisome proliferator–activated receptor (PPAR) {gamma} modulation is a new pharmacological approach that, based on selective receptor-cofactor interactions and target gene regulation, should result in potent insulin sensitization in the absence of PPAR{gamma}-mediated adverse effects. Here, we characterize two angiotensin receptor blockers (ARBs), telmisartan and irbesartan, as new selective PPAR modulators (SPPARMs). Analysis of PPAR{gamma} protein conformation using protease protection showed that telmisartan directly interacts with the receptor, producing a distinct conformational change compared with a glitazone. Glutathione S-transferase pull-down and fluorescence resonance energy transfer assays revealed selective cofactor binding by the ARBs compared with glitazones with an attenuated release of the nuclear receptor corepressor and absence of transcriptional intermediary factor 2 recruitment by ARBs. Consistently, selective cofactor binding resulted in differential gene expression profiles in adipocytes (ARB versus glitazone treated) assessed by oligo microarray analysis. Finally, telmisartan improved insulin sensitivity in diet-induced obese mice in the absence of weight gain. The present study identifies two ARBs as new SPPARMs. SPPARM activity by ARBs could retain the metabolic efficacy of PPAR{gamma} activation with reduction in adverse effects exerting in parallel AT1 receptor blockade. This may provide a new therapeutic option for better cardiovascular risk management in metabolic diseases and may initiate the development of new classes of drugs combining potent antihypertensive and antidiabetic actions

The farnesoid X receptor modulates hepatic carbohydrate metabolism during the fasting-refeeding transition

The liver plays a central role in the control of blood glucose homeostasis by maintaining a balance between glucose production and utilization. The farnesoid X receptor (FXR) is a bile acid-activated nuclear receptor. Hepatic FXR expression is regulated by glucose and insulin. Here we identify a role for FXR in the control of hepatic carbohydrate metabolism. When submitted to a controlled fasting-refeeding schedule, FXR-/- mice displayed an accelerated response to high carbohydrate refeeding with an accelerated induction of glycolytic and lipogenic genes and a more pronounced repression of gluconeogenic genes. Plasma insulin and glucose levels were lower in FXR-/- mice upon refeeding the high-carbohydrate diet. These alterations were paralleled by decreased hepatic glycogen content. Hepatic insulin sensitivity was unchanged in FXR-/- mice. Treatment of isolated primary hepatocytes with a synthetic FXR agonist attenuated glucose-induced mRNA expression as well as promoter activity of L-type pyruvate kinase, acetyl-CoA carboxylase 1, and Spot14. Moreover, activated FXR interfered negatively with the carbohydrate response elements regions. These results identify a novel role for FXR as a modulator of hepatic carbohydrate metabolism

Molecular characterization of new selective peroxisome proliferator–activated receptor {gamma} modulators with angiotensin receptor blocking activity

Selective peroxisome proliferator–activated receptor (PPAR) {gamma} modulation is a new pharmacological approach that, based on selective receptor-cofactor interactions and target gene regulation, should result in potent insulin sensitization in the absence of PPAR{gamma}-mediated adverse effects. Here, we characterize two angiotensin receptor blockers (ARBs), telmisartan and irbesartan, as new selective PPAR modulators (SPPARMs). Analysis of PPAR{gamma} protein conformation using protease protection showed that telmisartan directly interacts with the receptor, producing a distinct conformational change compared with a glitazone. Glutathione S-transferase pull-down and fluorescence resonance energy transfer assays revealed selective cofactor binding by the ARBs compared with glitazones with an attenuated release of the nuclear receptor corepressor and absence of transcriptional intermediary factor 2 recruitment by ARBs. Consistently, selective cofactor binding resulted in differential gene expression profiles in adipocytes (ARB versus glitazone treated) assessed by oligo microarray analysis. Finally, telmisartan improved insulin sensitivity in diet-induced obese mice in the absence of weight gain. The present study identifies two ARBs as new SPPARMs. SPPARM activity by ARBs could retain the metabolic efficacy of PPAR{gamma} activation with reduction in adverse effects exerting in parallel AT1 receptor blockade. This may provide a new therapeutic option for better cardiovascular risk management in metabolic diseases and may initiate the development of new classes of drugs combining potent antihypertensive and antidiabetic actions

4,4-Dimethyl-1,2,3,4-tetrahydroquinline-based PPARΑ/Γ agonists. Part I: Synthesis and pharmacological evaluation,

International audienc

Neuroprostanes, produced by free-radical mediated peroxidation of DHA, inhibit the inflammatory response of human macrophages

National audienc

Contribution of neuroprostanes to the anti-inflammatory properties of the omega-3 fatty acid DHA

National audienc

Bioactive oxylipins derived from DHA: neuroprostanes contribute to the anti-inflammatory action of DHA through the inhibition of NFkB and independently to PPARy

Oxylipins is a generic term representing the whole oxygenated metabolites produced through the enzymatic and non-enzymatic oxygenation of PUFAs. Oxylipins generated by free radical mediated peroxidation such as iso- and neuroprostanes have been restricted for a long time to oxidative stress biomarkers but several lines of evidence now suggest interesting signalling actions. In the present study, we aimed at investigating the anti-inflammatory properties of Neuroprostanes, a specific class of non-enzymatic oxylipins derived from DHA. Human peripheral blood mononuclear cells were isolated from healthy donors by Ficoll density gradient centrifugation. Monocytes were differentiated into resting macrophages (RM) for 6 days (37°C, 5% CO2) which were then exposed to 2 different types of NeuroPs (i.e. 14-A4-NeuroP and 4-F4t-NeuroP, 10 μM) or vehicle (ethanol 0.15%) during 30 min. Inflammatory response was induced by LPS (100 ng/mL) for 6 hrs. When RM macrophage were pre-exposed with 14-A4-NeuroP and 4-F4t-NeuroP, significant decrease of mRNA abundance for IL-6 (-49% and -26% respectively) and MCP-1 (-55% and -24 % respectively) were measured after LPS activation. Secretion of TNFα and MCP-1 was also reduced when RM were pre-exposed to 14-A4-NeuroP (-10%, ns and -34%, p<0.05) and 4-F4t-NeuroP (-12%, p<0.01 and 25%, ns). Preliminary results regarding the expression and phosphorylation of IkBa show a reduced level of phosphorylated IkBa with 4-F4t-NeuroP suggesting the inhibition of NFkB pathway. Finally, co-transfection of luciferase reporter vector with hPPARg expression vector performed on Cos-7 cells showed a weak interaction of NeuroPs with PPARg indicating that NeuroPs probably act independently of PPARg.In conclusion, these results suggest that the anti-inflammatory properties of DHA could be mediated, at least in part, by NeuroPs which corroborates the role of free-radical mediated reactions in cell signaling

Contribution of neuroprostanes to the anti-inflammatory properties of the omega-3 fatty acid DHA

National audienc