Regulation between the fed and fasted states in mammals is partially controlled by peroxisome proliferator-activated receptor-alpha (PPAR-alpha). Expression of the receptor is high in the liver, heart and skeletal muscle, but decreases with age. A combined (1)H nuclear magnetic resonance (NMR) spectroscopy and gas chromatography-mass spectrometry metabolomic approach has been used to examine metabolism in the liver, heart, skeletal muscle and adipose tissue in PPAR-alpha-null mice and wild-type controls during ageing between 3 and 13 months. For the PPAR-alpha-null mouse, multivariate statistics highlighted hepatic steatosis, reductions in the concentrations of glucose and glycogen in both the liver and muscle tissue, and profound changes in lipid metabolism in each tissue, reflecting known expression targets of the PPAR-alpha receptor. Hepatic glycogen and glucose also decreased with age for both genotypes. These findings indicate the development of age-related hepatic steatosis in the PPAR-alpha-null mouse, with the normal metabolic changes associated with ageing exacerbating changes associated with genotype. Furthermore, the combined metabolomic and multivariate statistics approach provides a robust method for examining the interaction between age and genotype.

The peroxisome proliferator (PP) ciprofibrate stimulates gastrin-producing cells (G-cells) in the rat stomach by an unknown mechanism, inducing hypergastrinemia and secondary enterochromaffin-like (ECL) cell hyperplasia. Ciprofibrate is a specific ligand for the nuclear peroxisome proliferator-activated receptor alpha (PPAR alpha). To see whether the effects of ciprofibrate could be imitated, rats were given another PPAR alpha ligand WY-14643 or the PPAR gamma ligand troglitazone by gastric intubations daily for 28 and 56 days. Troglitazone failed to raise gastrin levels. WY-14643 increased gastrin mRNA abundance, G-cell density and induced hypergastrinemia, but to a lesser extent than ciprofibrate. ECL cell parameters increased in proportion with the relative hypergastrinemia. Ciprofibrate and WY-14643 altered the levels of acyl CoA-oxidase mRNA and PPAR alpha mRNA in antrum, but had no effect in corpus. The PPAR alpha receptor was found in at least some G-cells by immunostaining. This study supports the hypothesis that PPAR alpha specific ligands could stimulate the G-cells by acting locally from the stomach lumen through antral PPAR alpha.

Nicotinic acetylcholine receptors (nAChRs) are involved in seizure mechanisms. Hence, nocturnal frontal lobe epilepsy was the first idiopathic epilepsy linked with specific mutations in α4 or β2 nAChR subunit genes. These mutations confer gain of function to nAChRs by increasing sensitivity toward acetylcholine. Consistently, nicotine elicits seizures through nAChRs and mimics the excessive nAChR activation observed in animal models of the disease. Treatments aimed at reducing nicotinic inputs are sought as therapies for epilepsies where these receptors contribute to neuronal excitation and synchronization. Previous studies demonstrated that peroxisome proliferator-activated receptors-α (PPARα), nuclear receptor transcription factors, suppress nicotine-induced behavioral and electrophysiological effects by modulating nAChRs containing β2 subunits. On these bases, we tested whether PPARα agonists were protective against nicotine-induced seizures. To this aim we utilized behavioral and electroencephalographic (EEG) experiments in C57BL/J6 mice and in vitro patch clamp recordings from mice and rats. Convulsive doses of nicotine evoked severe seizures and bursts of spike-waves discharges in ∼100% of mice. A single dose of the synthetic PPARα agonist WY14643 (WY, 80 mg/kg, i.p.) or chronic administration of fenofibrate, clinically available for lipid metabolism disorders, in the diet (0.2%) for 14 days significantly reduced or abolished behavioral and EEG expressions of nicotine-induced seizures. Acute WY effects were reverted by the PPARα antagonist MK886 (3 mg/kg, i.p.). Since neocortical networks are crucial in the generation of ictal activity and synchrony, we performed patch clamp recordings of spontaneous inhibitory postsynaptic currents (sIPSCs) from frontal cortex layer II/III pyramidal neurons. We found that both acute and chronic treatment with PPARα agonists abolished nicotine-induced sIPSC increases. PPARα within the CNS are key regulators of neuronal activity through modulation of nAChRs. These effects might be therapeutically exploited for idiopathic or genetically determined forms of epilepsy where nAChRs play a major role.

The application of high-throughput genomic tools in nutrition research is a widespread practice. However, it is becoming increasingly clear that the outcome of individual expression studies is insufficient for the comprehensive understanding of such a complex field. Currently, the availability of the large amounts of expression data in public repositories has opened up new challenges on microarray data analyses. We have focused on PPARalpha, a ligand-activated transcription factor functioning as fatty acid sensor controlling the gene expression regulation of a large set of genes in various metabolic organs such as liver, small intestine or heart. The function of PPARalpha is strictly connected to the function of its target genes and, although many of these have already been identified, major elements of its physiological function remain to be uncovered. To further investigate the function of PPARalpha, we have applied a cross-species meta-analysis approach to integrate sixteen microarray datasets studying high fat diet and PPARalpha signal perturbations in different organisms.

Diabetes mellitus is a public health problem worldwide. For this reason, ethanolic extract of Miconia sp. from Oaxaca, Mexico, was selected in search of an alternative against this disease. The effect of Miconia sp. on mRNA expression of PPARγ on cell line 3T3-L1, its effect on alpha amylase and alpha glucosidase, lipid accumulation during adipogenesis, and cell viability on VERO cells were evaluated. The mRNA levels of PPARγ increased on 1.393 ± 0.008 folds, lipid accumulation was increased by 29.55% with Miconia sp. extract and 34.57% with rosiglitazone, and α-amylase and α-glycosidase were inhibited with IC50 values from 28.23 ± 2.15 μg/mL and 1.95 ± 0.15 μg/mL, respectively; the IC50 on antiproliferative activity on VERO cells was 314.54 ± 45.40 μg/mL. In case of α-amylase and α-glycosidase assays, IC50 (inhibitory concentration 50) refers to necessary extract amounts to inhibit 50% of enzymatic activity. On the other hand, on antiproliferative activity, IC50 (inhibitory concentration 50) refers to necessary extract amounts to inhibit 50% of cell proliferation. It was concluded that the compounds present in Miconia sp. ethanolic extract increase mRNA expression of PPARγ, inhibit α-amylase and α-glucosidase, and increase lipid accumulation. It constitutes an alternative as adjuvant in diabetes mellitus treatment; therefore, we recommend continuing identifying the compounds responsible for its promising in vivo antidiabetic activity.

Dicer is a crucial RNase III enzyme in miRNA biogenesis pathway. Although numerous studies have been carried out to investigate the role of miRNAs and Dicer in the regulation of biological processes, few studies have examined proteomic alterations upon knockout of Dicer. We employed a Cre-loxP-based inducible knockout mouse system to investigate the proteome regulated by Dicer-dependent miRNAs. We utilized spiked liver lysates from metabolically labeled mice to quantify the subtle changes in the liver proteome upon deletion of Dicer. We identified 2137 proteins using high resolution tandem mass spectrometry analysis. The upregulated proteins included several enzymes involved in peroxisomal β-oxidation of fatty acids and a large majority of the upregulated proteins involved in lipid metabolism were known PPARα targets. MRM-based assays were carried out to confirm the upregulation of enzymes including peroxisomal bifunctional enzyme, phosphoenolpyruvate carboxykinase 1, cytochrome P450 3A13, cytochrome P450 3A41 and myristoylated alanine-rich protein kinase C substrate. Further, miRNA-124 which is predicted to regulate expression of peroxisomal bifunctional enzyme was confirmed to be downregulated in the Dicer knockout mice. Our study demonstrates the strength of coupling knockout mouse models and quantitative proteomic strategies to investigate functions of individual proteins in vivo.

Mice with inactivation of the D-specific multifunctional protein 2 (MFP2), a crucial enzyme of peroxisomal beta-oxidation, develop multiple pathologies in diverse tissues already starting in the postnatal period. Gene expression profiling performed on liver of 2-day-old pups revealed up-regulation of PPAR alpha responsive genes in knockout mice. Surprisingly, also genes involved in cholesterol biosynthesis were markedly induced. Real-time PCR confirmed the induction of PPAR alpha target genes and of HMGCR and SREBP2, both involved in cholesterol synthesis, in lactating and in adult MFP2 knockout mice. In accordance, the rate of cholesterol biosynthesis was significantly increased in liver of knockout mice but the hepatic cholesterol concentration was unaltered. In MFP2/PPAR alpha double knockout mice, up-regulations of SREBP2 and HMGCR were markedly attenuated. These data demonstrate a tight interrelationship between induction of PPAR alpha by endogenous ligands and up-regulation of genes of cholesterol biosynthesis through increased expression of SREBP2.

Maintenance of metabolic homeostasis is secured by metabolite-sensing systems, which can be overwhelmed by constant macronutrient surplus in obesity. Not only the uptake processes but also the consumption of energy substrates determine the cellular metabolic burden. We herein describe a novel transcriptional system in this context comprised of peroxisome proliferator-activated receptor alpha (PPARα), a master regulator for fatty acid oxidation, and C-terminal binding protein 2 (CtBP2), a metabolite-sensing transcriptional corepressor. CtBP2 interacts with PPARα to repress its activity, and the interaction is enhanced upon binding to malonyl-CoA, a metabolic intermediate increased in tissues in obesity and reported to suppress fatty acid oxidation through inhibition of carnitine palmitoyltransferase 1. In line with our preceding observations that CtBP2 adopts a monomeric configuration upon binding to acyl-CoAs, we determined that mutations in CtBP2 that shift the conformational equilibrium toward monomers increase the interaction between CtBP2 and PPARα. In contrast, metabolic manipulations that reduce malonyl-CoA decreased the formation of the CtBP2-PPARα complex. Consistent with these in vitro findings, we found that the CtBP2-PPARα interaction is accelerated in obese livers while genetic deletion of CtBP2 in the liver causes derepression of PPARα target genes. These findings support our model where CtBP2 exists primarily as a monomer in the metabolic milieu of obesity to repress PPARα, representing a liability in metabolic diseases that can be exploited to develop therapeutic approaches.

Peroxisome proliferator-activated receptor alpha (PPAR-α) belongs to the nuclear receptor superfamily of proteins. It is one of the principle regulators of metabolism and lipid homeostasis whose malfunction leads to complications including obesity and type 2 diabetes. In the adipose tissue, glyceroneogenesis is a unique pathway through which pyruvate is converted into glycerol-3- phosphate (G3P) in a multistep process. Previous findings demonstrated that glyceroneogenesis regulates triacylglycerol synthesis and adipogenesis. This led us to hypothesize that one of the pathway intermediate is physiologically relevant PPAR-α ligand. In the present study using in silico docking, we proved that glycerate, dihydroxy acetone phosphate, glyceraldehyde-3-phosphate, and G3P are key glyceroneogenesis pathway intermediates which bind to PPAR-α. They bind PPAR-α with comparable binding energy and docking score to that of (2s)-2-ethoxy-3-[4-(2-{4-[(methylsulfonyl)oxy]phenyl}ethoxy)phenyl]propanoic acid(AZ-2), a synthetic high affinity ligand of PPAR-α. These intermediates could be studied further as potential physiologically relevant activators of PPAR-α in vitro and in vivo.

Thiazolidinediones (TZDs), agonists for PPARs, have been shown to block the inhibitory effects of TNF-alpha on insulin action using cultured cells. In order to clarify the in vivo effects of TZDs on the inhibition of insulin sensitivity by TNF-alpha, insulin action in muscles and adipose tissues was assessed in the TNF-alpha-overexpression mice model using transplantation of cells secreting the TNF-alpha protein. After the pioglitazone treatment for 4 weeks, glucose uptake, insulin-induced IRS-1 phosphorylation, and lipoprotein lipase mRNA levels were analyzed. Pioglitazone did not ameliorate TNF-alpha-induced hyperinsulinemia in this model, as assessed by the OGTT. Glucose uptake and lipoprotein lipase mRNA levels were decreased by TNF-alpha in adipose tissues from the TNF-alpha-overexpressing mice, and pioglitazone blocked these inhibitions by TNF-alpha. On the other hand, in muscles, pioglitazone did not reverse the effects of TNF-alpha on insulin-induced phosphorylation of IRS-1, glucose uptake, and lipoprotein lipase mRNA levels. Present study revealed the different sensitivities of pioglitazone for the recovery of decreased insulin action in a TNF-alpha-overexpressing model using cell transplantation. These results suggest that the effect of TZDs is dependent on the fat distribution and accumulation in humans.

Despite the great efficacy reported for cisplatin as a widely used chemotherapeutic agent, its clinical use is limited by the challenge of facing its serious side effect; nephrotoxicity. In this study, the effect of the benzbromarone on peroxisome proliferator-activated receptor-alpha (PPAR-α) was investigated against cisplatin nephrotoxicity.

Peroxisome Proliferator Activated Receptor (PPAR)-α is a key regulator of lipid metabolism and recent studies reveal it also regulates inflammation in several different disease models. Gemfibrozil, an agonist of PPAR-α, is a FDA approved drug for hyperlipidemia and has been shown to inhibit clinical signs in a rodent model of multiple sclerosis. Since many studies have shown improved outcome from spinal cord injury (SCI) by anti-inflammatory and neuroprotective agents, we tested the efficacy of oral gemfibrozil given before or after SCI for promoting tissue preservation and behavioral recovery after spinal contusion injury in mice. Unfortunately, the results were contrary to our hypothesis; in our first attempt, gemfibrozil treatment exacerbated locomotor deficits and increased tissue pathology after SCI. In subsequent experiments, the behavioral effects were not replicated but histological outcomes again were worse. We also tested the efficacy of a different PPAR-α agonist, fenofibrate, which also modulates immune responses and is beneficial in several neurodegenerative disease models. Fenofibrate treatment did not improve recovery, although there was a slight trend for a modest increase in histological tissue sparing. Based on our results, we conclude that PPAR-α agonists yield either no effect or worsen recovery from spinal cord injury, at least at the doses and the time points of drug delivery tested here. Further, patients sustaining spinal cord injury while taking gemfibrozil might be prone to exacerbated tissue damage.

Activation of peroxisome proliferator-activated receptor (PPAR)gamma is associated with bone loss and increased fracture risk, while PPARalpha activation seems to have positive skeletal effects. To further explore these effects we have examined the effect of the PPARalpha agonists fenofibrate and Wyeth 14643, and the PPARgamma agonist pioglitazone, on bone mineral density (BMD), bone architecture and biomechanical strength in ovariectomized rats.

To investigate the efficacy of the peroxisome proliferator-activated receptor-alpha (PPARalpha) agonist, AVE8134, in cellular and experimental models of cardiac dysfunction and heart failure.

At present, there are more and more patients with acute hypertriglyceridemia pancreatitis in clinical practice. Common treatment measures include fasting and water withdrawal, fluid resuscitation, and somatostatin. In recent years, studies have pointed out that the PPARa agonist fenofibrate may help improve the condition of such patients. Therefore, through clinical research and analysis, we reported for the first time that fenofibrate combined with octreotide acetate has a more excellent effect in the treatment of patients with acute hypertriglyceridemia pancreatitis, and from the perspective of signal pathways, we revealed that the combination of the two drugs has an effect on NF-κB P65. The synergistic inhibitory effect proves that the combined treatment is beneficial to control inflammation, protect liver function, and improve the prognosis of patients. It is worthy of clinical promotion.

MMP-12, a macrophage-specific matrix metalloproteinase with large substrate specificity, has been reported to be highly expressed in mice, rabbits and human atherosclerotic lesions. Increased MMP-12 from inflammatory macrophages is associated with several degenerative diseases such as atherosclerosis. In this manuscript, we show that IL-1beta, a proinflammatory cytokine found in atherosclerotic plaques, increases both mRNA and protein levels of MMP-12 in human monocyte-derived macrophages (HMDM). Since peroxisome proliferator-activated receptors (PPARs), such as PPARalpha and PPARgamma, are expressed in macrophages and because PPAR activation exerts an anti-inflammatory effect on vascular cells, we have investigated the effect of PPARalpha and gamma isoforms on MMP-12 regulation in HMDM. Our results show that MMP-12 expression (mRNA and protein) is down regulated in IL-1beta-treated macrophages only in the presence of a specific PPARalpha agonist, GW647, in a dose-dependent manner. In contrast, this inhibitory effect was abolished in IL-1beta-stimulated peritoneal macrophages isolated from PPARalpha(-/-) mice and treated with the PPARalpha agonist, GW647. Moreover, reporter gene transfection experiments using different MMP-12 promoter constructs showed a reduction of the promoter activities by approximately 50% in IL-1beta-stimulated PPARalpha-pre-treated cells. However, MMP-12 promoter analysis did not reveal the presence of a PPRE response element. The IL-1beta effect is known to be mediated through the AP-1 binding site. Mutation of the AP-1 site, located at -81 in the MMP-12 promoter region relative to the transcription start site, followed by transfection analysis, gel shift and ChIP experiments revealed that the inhibitory effect was the consequence of the protein-protein interaction between GW 647-activated PPARalpha and c-Fos or c-Jun transcription factors, leading to inhibition of their binding to the AP-1 motif. These studies suggest that PPARalpha agonists may be used therapeutically, not only for lipid disorders, but also to prevent inflammation and atheromatous plaque rupture, where their ability to inhibit MMP-12 expression in HMDM may be beneficial.

We show here that the alpha, beta, and gamma isotypes of peroxisome proliferator-activated receptor (PPAR) are expressed in the mouse epidermis during fetal development and that they disappear progressively from the interfollicular epithelium after birth. Interestingly, PPARalpha and beta expression is reactivated in the adult epidermis after various stimuli, resulting in keratinocyte proliferation and differentiation such as tetradecanoylphorbol acetate topical application, hair plucking, or skin wound healing. Using PPARalpha, beta, and gamma mutant mice, we demonstrate that PPARalpha and beta are important for the rapid epithelialization of a skin wound and that each of them plays a specific role in this process. PPARalpha is mainly involved in the early inflammation phase of the healing, whereas PPARbeta is implicated in the control of keratinocyte proliferation. In addition and very interestingly, PPARbeta mutant primary keratinocytes show impaired adhesion and migration properties. Thus, the findings presented here reveal unpredicted roles for PPARalpha and beta in adult mouse epidermal repair.

Abdominal obesity is a principal risk factor in the development of metabolic syndrome. Previously, we showed that a palatinose-based liquid formula, Inslow/MHN-01, suppressed postprandial plasma glucose level and reduced visceral fat accumulation better than the standard formula (SF). To elucidate the mechanism of Inslow-mediated anti-obesity effect, expression levels of genes involved in the glucose and lipid metabolism were compared in Inslow- and SF-fed rats. Both fasting plasma insulin level and average islet sizes were reduced in the Inslow group. We also found less abdominal fat accumulation and reduced hepatic triacylglycerol content in the Inslow group. Expression of the beta-oxidation enzymes and uncoupling potein-2 (UCP-2) mRNAs in the liver of the Inslow group were higher than the SF group, which was due to a concomitant higher expression of the peroxisome proliferator-activated receptor (PPAR)-alpha mRNA in the former. Furthermore, expression of the UCP-2 and adiponectin mRNAs in the epididymal fat were higher in the Inslow group than the SF group, and were stimulated by a concomitant increase of the PPAR-gamma gene expression in the former. These results strongly suggested that the anti-obesity effect of Inslow was due to an increase in the hepatic PPAR-alpha and adipocyte PPAR-gamma gene expressions.

One of the most important factors in the initiation and progression of atherosclerosis is the default in macrophage cholesterol homeostasis. Many genes and transcription factors such as peroxisome proliferators activated receptors (PPARs) and acyl coenzyme A: cholesterol acyltransferase1 (ACAT1) are involved in cholesterol homeostasis. Fatty acids are important ligands of PPARalpha and the concentration of them can effect expression of ACAT1. So this study designed to clarified on the role of these genes and fatty acids on the lipid metabolism in foam cells.

Proton Nuclear Magnetic Resonance spectroscopy and Gas Chromatography Mass Spectrometry based metabolomics has been used in conjunction with multivariate statistics to examine the metabolic changes in Caenorhabditis elegans following the deletion of nuclear hormone receptor-49 (nhr-49). Deletion of the receptor produced profound changes in fatty acid metabolism, in particular an increase in the ratio of unsaturated to saturated fatty acids, a decrease in the concentration of glucose and increases in lactate and alanine. Given the proposed functional similarity between nhr-49 and the mammalian peroxisome proliferator-activated receptors (PPARs) these changes were compared with the metabolome of the PPAR-alpha null mouse. The metabolomic approach demonstrated a number of similarities including the regulation of lipid synthesis, beta-oxidation of fatty acids and changes in glycolysis/gluconeogenesis.