4-phenylbutyric acid improves sepsis-induced cardiac dysfunction by modulating amino acid metabolism and lipid metabolism via Comt/Ptgs2/Ppara

INTRODUCTION

Cardiac dysfunction after sepsis the most common and severe sepsis-related organ failure. The severity of cardiac damage in sepsis patients was positively associated to mortality. It is important to look for drugs targeting sepsis-induced cardiac damage. Our previous studies found that 4-phenylbutyric acid (PBA) was beneficial to septic shock by improving cardiovascular function and survival, while the specific mechanism is unclear.

OBJECTIVES

We aimed to explore the specific mechanism and PBA for protecting cardiac function in sepsis.

METHODS

The cecal ligation and puncture-induced septic shock models were used to observe the therapeutic effects of PBA on myocardial contractility and the serum levels of cardiac troponin-T. The mechanisms of PBA against sepsis were explored by metabolomics and network pharmacology.

RESULTS

The results showed that PBA alleviated the sepsis-induced cardiac damage. The metabolomics results showed that there were 28 metabolites involving in the therapeutic effects of PBA against sepsis. According to network pharmacology, 11 hub genes were found that were involved in lipid metabolism and amino acid transport following PBA treatment. The further integrated analysis focused on 7 key targets, including Comt, Slc6a4, Maoa, Ppara, Pparg, Ptgs2 and Trpv1, as well as their core metabolites and pathways. In an in vitro assay, PBA effectively inhibited sepsis-induced reductions in Comt, Ptgs2 and Ppara after sepsis.

CONCLUSIONS

PBA protects sepsis-induced cardiac injury by targeting Comt/Ptgs2/Ppara, which regulates amino acid metabolism and lipid metabolism. The study reveals the complicated mechanisms of PBA against sepsis.

Chrysin attenuates estradiol-induced endometrial hyperplasia in rats via enhancing PPARα activity

Endometrial hyperplasia (EH) is a complex condition that commonly affects women after menopause. Since the current available treatments for EH are mainly invasive, there is a need for developing new treatment modalities. Chrysin (Ch) is a dihydroxyflavone with numerous promising therapeutic potentials. In this study, Ch's protective effects on estradiol (E2)-induced EH were studied in rats. Animals were allocated randomly to five groups and were treated for 4 weeks as follows: Group 1, control: received the vehicle; group 2, Ch: received Ch 25 mg/kg; group 3, estradiol (E2): received E2 (3 mg/kg) 3 × weekly subcutaneously and the vehicle. Group 4, E2 + Ch 10 mg/kg and group 5, E2 + Ch 25 mg/kg: Ch was given once daily at 10 mg/kg or 25 mg/kg, respectively. In addition, E2 was administered 3 × weekly (3 mg/kg) in groups 4 and 5. Ch inhibited the E2-induced increase in uterine weights and histopathological changes. Ch lowered the cyclin D1 expression. Ch raised the caspase-3 content and Bax mRNA expression. Furthermore, it corrected the raised Bcl2 mRNA expression due to E2. Ch inhibited MDA accumulation and GSH depletion. It also prevents E2-induced SOD and GPx exhaustion. It also ameliorated the rise in NFκB, TNF-α, and IL-6 expression. These effects were correlated with an enhanced PPARα activity ratio relative to the E2 group. This suggests that Ch attenuates EH in this model by exerting anti-proliferative, anti-oxidant, and anti-inflammatory effects partially through increasing PPARα activity.

NLRP3 Inflammasome Inhibition by MCC950 in Aged Mice Improves Health via Enhanced Autophagy and PPARα Activity

The NLRP3 inflammasome has emerged as an important regulator of metabolic disorders and age-related diseases in NLRP3-deficient mice. In this article, we determine whether, in old mice C57BL6J, the NLRP3 inflammasome inhibitor MCC950 is able to attenuate age-related metabolic syndrome to providing health benefits. We report that MCC950 attenuates metabolic and hepatic dysfunction in aged mice. In addition, MCC950 inhibited the Pi3K/AKT/mTOR pathway, enhanced autophagy, and activated peroxisome proliferator-activated receptor-α in vivo and in vitro. The data suggest that MCC950 mediates the protective effects by the mammalian target of rapamycin inhibition, thus activating autophagy and peroxisome proliferator-activated receptor-α. In conclusion, pharmacological inhibition of NLRP3 in aged mice has a significant impact on health. Thus, NLRP3 may be a therapeutic target of human age-related metabolic syndrome.

Anti-influenza A Virus Effects and Mechanisms of Emodin and Its Analogs via Regulating PPARα/γ-AMPK-SIRT1 Pathway and Fatty Acid Metabolism

The peroxisome proliferator-activated receptor (PPAR) α/γ-adenosine 5'-monophosphate- (AMP-) activated protein kinase- (AMPK-) sirtuin-1 (SIRT1) pathway and fatty acid metabolism are reported to be involved in influenza A virus (IAV) replication and IAV-pneumonia. Through a cell-based peroxisome proliferator responsive element- (PPRE-) driven luciferase bioassay, we have investigated 145 examples of traditional Chinese medicines (TCMs). Several TCMs, such as Polygonum cuspidatum, Rheum officinale Baillon, and Aloe vera var. Chinensis (Haw.) Berg., were found to possess high activity. We have further detected the anti-IAV activities of emodin (EMO) and its analogs, a group of common important compounds of these TCMs. The results showed that emodin and its several analogs possess excellent anti-IAV activities. The pharmacological tests showed that emodin significantly activated PPARα/γ and AMPK, decreased fatty acid biosynthesis, and increased intracellular ATP levels. Pharmaceutical inhibitors, siRNAs for PPARα/γ and AMPKα1, and exogenous palmitate impaired the inhibition of emodin. The in vivo test also showed that emodin significantly protected mice from IAV infection and pneumonia. Pharmacological inhibitors for PPARα/γ and AMPK signal and exogenous palmitate could partially counteract the effects of emodin in vivo. In conclusion, emodin and its analogs are a group of promising anti-IAV drug precursors, and the pharmacological mechanism of emodin is linked to its ability to regulate the PPARα/γ-AMPK pathway and fatty acid metabolism.

Gut-liver axis modulation in fructose-fed mice: a role for PPAR-alpha and linagliptin

Fructose dietary intake affects the composition of the intestinal microbiota and influences the development of hepatic steatosis. Endotoxins produced by gram-negative bacteria alter intestinal permeability and cause bacterial translocation. This study evaluated the effects of gut microbiota modulation by a purified PPAR-alpha agonist (WY14643), a DPP-4 inhibitor (linagliptin), or their association on intestinal barrier integrity, endotoxemia, and hepatic energy metabolism in high-fructose-fed C57BL/6 mice. Fifty mice were divided to receive the control diet (C group) or the high-fructose diet (HFRU) for 12 weeks. Subsequently, the HFRU group was divided to initiate the treatment with PPAR-alpha agonist (3.5 mg/kg/BM) and DPP-4 inhibitor (15 mg/kg/BM). The HFRU group had glucose intolerance, endotoxemia, and dysbiosis (with increased Proteobacteria) without changes in body mass in comparison with the C group. HFRU group showed damaged intestinal ultrastructure, which led to liver inflammation and marked hepatic steatosis in the HFRU group when compared to the C group. PPAR-alpha activation and DPP-4 inhibition countered glucose intolerance, endotoxemia, and dysbiosis, ameliorating the ultrastructure of the intestinal barrier and reducing Tlr4 expression in the liver of treated animals. These beneficial effects suppressed lipogenesis and mitigated hepatic steatosis. In conclusion, the results herein propose a role for PPAR-alpha activation, DPP-4 inhibition, and their association in attenuating hepatic steatosis by gut-liver axis modulation in high-fructose mice model. These observations suggest these treatments as potential targets to treat hepatic steatosis and avoid its progression.

Assessment of the Mode of Action Underlying the Effects of GenX in Mouse Liver and Implications for Assessing Human Health Risks

GenX is an alternative to environmentally persistent long-chain perfluoroalkyl and polyfluoroalkyl substances. Mice exposed to GenX exhibit liver hypertrophy, elevated peroxisomal enzyme activity, and other apical endpoints consistent with peroxisome proliferators. To investigate the potential role of peroxisome proliferator-activated receptor alpha (PPARα) activation in mice, and other molecular signals potentially related to observed liver changes, RNA sequencing was conducted on paraffin-embedded liver sections from a 90-day subchronic toxicity study of GenX conducted in mice. Differentially expressed genes were identified for each treatment group, and gene set enrichment analysis was conducted using gene sets that represent biological processes and known canonical pathways. Peroxisome signaling and fatty acid metabolism were among the most significantly enriched gene sets in both sexes at 0.5 and 5 mg/kg GenX; no pathways were enriched at 0.1 mg/kg. Gene sets specific to the PPARα subtype were significantly enriched. These findings were phenotypically anchored to histopathological changes in the same tissue blocks: hypertrophy, mitoses, and apoptosis. In vitro PPARα transactivation assays indicated that GenX activates mouse PPARα. These results indicate that the liver changes observed in GenX-treated mice occur via a mode of action (MOA) involving PPARα, an important finding for human health risk assessment as this MOA has limited relevance to humans.

NIK links inflammation to hepatic steatosis by suppressing PPARα in alcoholic liver disease

Background: Inflammation and steatosis are the main pathological features of alcoholic liver disease (ALD), in which, inflammation is one of the critical drivers for the initiation and development of alcoholic steatosis. NIK, an inflammatory pathway component activated by inflammatory cytokines, was suspected to link inflammation to hepatic steatosis during ALD. However, the underlying pathogenesis is not well-elucidated. Methods: Alcoholic steatosis was induced in mice by chronic-plus-binge ethanol feeding. Both the loss- and gain-of-function experiments by the hepatocyte-specific deletion, pharmacological inhibition and adenoviral transfection of NIK were utilized to elucidate the role of NIK in alcoholic steatosis. Rate of fatty acid oxidation was assessed in vivo and in vitro. PPARα agonists or antagonists of MEK1/2 and ERK1/2 were used to identify the NIK-induced regulation of PPARα, MEK1/2, and ERK1/2. The potential interactions between NIK, MEK1/2, ERK1/2 and PPARα and the phosphorylation of PPARα were clarified by immunoprecipitation, immunoblotting and far-western blotting analysis. Results: Hepatocyte-specific deletion of NIK protected mice from alcoholic steatosis by sustaining hepatic fatty acid oxidation. Moreover, overexpression of NIK contributed to hepatic lipid accumulation with disrupted fatty acid oxidation. The pathological effect of NIK in ALD may be attributed to the suppression of PPARα, the main controller of fatty acid oxidation in the liver, because PPARα agonists reversed NIK-mediated hepatic steatosis and malfunction of fatty acid oxidation. Mechanistically, NIK recruited MEK1/2 and ERK1/2 to form a complex that catalyzed the inhibitory phosphorylation of PPARα. Importantly, pharmacological intervention against NIK significantly attenuated alcoholic steatosis in ethanol-fed mice. Conclusions: NIK targeting PPARα via MEK1/2 and ERK1/2 disrupts hepatic fatty acid oxidation and exhibits high value in ALD therapy.

Novel Anti-Obesity Properties of Palmaria mollis in Zebrafish and Mouse Models

(1) Background: The red seaweed Palmaria mollis (PM), which has a bacon-like taste, is increasingly being included in Western diets. In this study, we evaluate anti-obesity effects of PM using diet-induced obese (DIO) zebrafish and mice models. (2) Methods: We fed PM-containing feed to DIO-zebrafish and mice, and evaluated the anti-obesity effects We also analyzed gene expression changes in their liver and visceral adipose tissues (VAT). (3) Results: PM ameliorated several anti-obesity traits in both animals, including dyslipidaemia, hepatic steatosis, and visceral adiposity. In liver tissues of DIO-zebrafish and mice, PM upregulated gene expressions involved in peroxisome proliferator-activated receptor alpha (PPARA) pathways, and downregulated peroxisome proliferator-activated receptor gamma (PPARG) pathways, suggesting that the lipid-lowering effect of PM might be caused by activation of beta-oxidation and inhibition of lipogenesis. In VAT, PM downregulated genes involved in early and late adipocyte differentiation in zebrafish, but not in mice. (4) Conclusions: We have demonstrated that PM can prevent hepatic steatosis and visceral adiposity for the first time. Dietary supplementation of PM as a functional food may be suitable for obesity prevention and reduction in the prevalence of obesity-related diseases.

The OEA effect on food intake is independent from the presence of PPARα in the intestine and the nodose ganglion, while the impact of OEA on energy expenditure requires the presence of PPARα in mice

BACKGROUND

Oleoylethanolamide (OEA) is an endocannabinoid that controls food intake, energy expenditure and locomotor activity. Its anorexigenic effect appears to be mediated by PPARα, but the tissue where the presence of this receptor is required for OEA to inhibit feeding is unknown as yet. Previous studies point to a possible role of proximal enterocytes and neurons of the nodose ganglion.

MATERIALS AND METHODS

Acute intraperitoneal OEA effects on food intake, energy expenditure, respiratory exchange ratio (RER) and locomotor activity were studied in control mice (PPARα-loxP) and intestinal (Villin-Cre;PPARα-loxP) or nodose ganglion (Phox2B-Cre;PPARα-loxP) specific PPARα knockout mice placed in calorimetric cages.

RESULTS

OEA administration to both intestinal and nodose ganglion PPARα knockout mice decreased food intake, RER (leading to increased lipid oxidation) and locomotor activity as in control mice. However, while OEA injection acutely decreased energy expenditure in controls, this effect was not observed in mice devoid of PPARα in the intestine.

CONCLUSION

These results indicate that the OEA effect on food intake is independent from the presence of PPARα in the intestine and the nodose ganglion, while the impact of OEA on energy expenditure requires the presence of PPARα in the intestine.

Capsaicin in Metabolic Syndrome

Capsaicin, the major active constituent of chilli, is an agonist on transient receptor potential vanilloid channel 1 (TRPV1). TRPV1 is present on many metabolically active tissues, making it a potentially relevant target for metabolic interventions. Insulin resistance and obesity, being the major components of metabolic syndrome, increase the risk for the development of cardiovascular disease, type 2 diabetes, and non-alcoholic fatty liver disease. In vitro and pre-clinical studies have established the effectiveness of low-dose dietary capsaicin in attenuating metabolic disorders. These responses of capsaicin are mediated through activation of TRPV1, which can then modulate processes such as browning of adipocytes, and activation of metabolic modulators including AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor α (PPARα), uncoupling protein 1 (UCP1), and glucagon-like peptide 1 (GLP-1). Modulation of these pathways by capsaicin can increase fat oxidation, improve insulin sensitivity, decrease body fat, and improve heart and liver function. Identifying suitable ways of administering capsaicin at an effective dose would warrant its clinical use through the activation of TRPV1. This review highlights the mechanistic options to improve metabolic syndrome with capsaicin.

[Role of PPARα in the oxidative damage of rat liver cells BRL-3A induced by perfluorooctanoic acid]

OBJECTIVE

To investigate the role of PPARα in oxidative damage of BRL-3A cells induced by perfluorooctanoic acid( PFOA) by inhibiting and activating gene expression.

METHODS

In vitro culture of rat liver BRL-3A cells were divided into blank control group, PFOA experimental control group, PPARα inhibition group( GW6471), PPARα agonist group( WY14643), PPARα inhibitor pretreatment PFOA group( GW6471 + PFOA), PPARα agonist pretreatment PFOA group( WY14643 + PFOA). Fluorescence immunocytochemistry was used to detect the expression of PPARα. The expression of PPARα and its downstream target gene was detected by q PCR. The expression of related protein was detected by Western blot.

RESULTS

The expression of PPARα in rat liver BRL-3A cells was successfully inhibited and stimulated by inhibitors and agonists( P < 0. 05). Compared with the blank control group and the PFOA experimental control group, there was a significant decrease in the content of ROS in the WY14643 + PFOA group compared with the blank control group and the PFOA experimental control group( P < 0. 05). The expression of PPARα and its downstream gene Cyp4a1 in GW6471 + PFOA group was higher than that in PPARα inhibitor group( P < 0. 05), but it was significantly lower than that in PFOA experimental control group( P < 0. 05). The expression of related genes in WY14643 + PFOA group was significantly lower than that in PPARα agonist group( P < 0. 05). The protein expression of PPARα in GW6471 + PFOA group was up-regulated compared with the inhibitor group, there was no difference compared with the blank control group. The protein expression of PPARα in WY14643 + PFOA group was not significantly different from that in agonist group, but it was significantly higher than that in PFOA experimental control group( P < 0. 05).

CONCLUSION

PFOA exposure can activate the expression of PPARα, remove ROS, PPARα played a protective role in PFOA-induced rat liver cell oxidative damage.

[Effects of perfluorooctanoic acid on oxidative stress and PPARα and its related CYP4A1 gene expression in rat liver]

OBJECTIVE

To study the effects on oxidative stress and the expression of PPARα-related genes and protein in the liver of rats induced by pentadecafluorooctanoic acid( PFOA).

METHODS

A total of 28 male SD rats were randomly divided into four groups: control group: double distilled water, low dose group: PFOA 1 mg/( kg·d), middle dose group: PFOA 5 mg/( kg·d), high dose group: PFOA 25 mg/( kg·d), and were administrated by gavage once a day for 14 days take the organization after anesthesia, according to the follow-up experiments need treatment. The activity of oxidative stressrelated enzymes and the content of malondialdehyde( MDA) in liver tissue were detected. The mRNA levels of peroxisome proliferators-activited receptors α( PPARα) and cytochrome P4504A1( CYP4A1) were detected by real-time PCR. The protein expression of PPARα was detected by Western blot.

RESULTS

There was significant difference between high dose group and control group of the body weight( P < 0. 05). The liver weight and relative liver weight of the middle and high dose groups were significantly higher than those of the control group( P < 0. 05). The activity of superoxide dismutase( SOD) and glutathione peroxidase( GSH-Px) in the liver of the low dose group were significantly higher than that of the control group( P < 0. 05). The content of MDA in liver of middle and high dose groups were increased by 2. 5 times and 3. 5 times compared with that of control group( P < 0. 05). The expression of PPARα and its regulated CYP4A1 mRNA were significantly increased in low, middle and high dose groups. The expression of PPARα protein in the low, middle and high dose groups were up-regulated.

CONCLUSION

PFOA exposure can lead to oxidative stress in rat liver, resulting in antioxidant enzymes SOD and GSH-Px and MDA changes. At the same time, PFOA exposure induced up regulation of PPARα and CYP4A1 in the liver of rats to enhance theβ-oxidation of fatty acids, leading to lipid peroxidation, which has obvious toxic effects on rat liver.

Gemfibrozil not fenofibrate decreases systemic glucose level via PPARα

BACKGROUND

Concurrence of high glucose or diabetes in patients with dyslipidemia is presenting major challenges for clinicians. Although sporadically reported, a rational basis for the use of fibrates for the treatment of dyslipidemia with concurrent metabolic syndrome has not been established.

METHODS

In this study, wild-type (WT) and Ppara-null (KO) mice were fed a serial gemfibrozil- and fenofibrate-containing diet under the same experimental conditions for 14 days. Glucose level in the blood, glycogen storage in the liver tissues, and the potential toxic responses were assayed. Genes involved in glucose metabolism were determined by quantitative polymerase chain reaction analysis.

RESULTS

Both the blood glucose level and the glycogen content in the liver were down-regulated by gemfibrozil but not by fenofibrate in WT mice, in a dose-dependent manner. This decrement did not occur in KO mice for either fibrate agent. Secondary regulation on the transcription of pyruvate kinase, and gluconolactonase were observed following gemfibrozil treatment, which was differential between WT mice and KO mice.

CONCLUSIONS

Gemfibrozil, not fenofibrate, down-regulates systemic glucose level and glycogen storage in the liver dependent on PPARα, suggesting its potential value for treatment of dyslipidemia with concurrent diabetes or high glucose levels.

Identification of modulators of the nuclear receptor peroxisome proliferator-activated receptor α (PPARα) in a mouse liver gene expression compendium

The nuclear receptor family member peroxisome proliferator-activated receptor α (PPARα) is activated by therapeutic hypolipidemic drugs and environmentally-relevant chemicals to regulate genes involved in lipid transport and catabolism. Chronic activation of PPARα in rodents increases liver cancer incidence, whereas suppression of PPARα activity leads to hepatocellular steatosis. Analytical approaches were developed to identify biosets (i.e., gene expression differences between two conditions) in a genomic database in which PPARα activity was altered. A gene expression signature of 131 PPARα-dependent genes was built using microarray profiles from the livers of wild-type and PPARα-null mice after exposure to three structurally diverse PPARα activators (WY-14,643, fenofibrate and perfluorohexane sulfonate). A fold-change rank-based test (Running Fisher’s test (p-value ≤ 10^-4)) was used to evaluate the similarity between the PPARα signature and a test set of 48 and 31 biosets positive or negative, respectively for PPARα activation; the test resulted in a balanced accuracy of 98%. The signature was then used to identify factors that activate or suppress PPARα in an annotated mouse liver/primary hepatocyte gene expression compendium of ~1850 biosets. In addition to the expected activation of PPARα by fibrate drugs, di(2-ethylhexyl) phthalate, and perfluorinated compounds, PPARα was activated by benzofuran, galactosamine, and TCDD and suppressed by hepatotoxins acetaminophen, lipopolysaccharide, silicon dioxide nanoparticles, and trovafloxacin. Additional factors that activate (fasting, caloric restriction) or suppress (infections) PPARα were also identified. This study 1) developed methods useful for future screening of environmental chemicals, 2) identified chemicals that activate or suppress PPARα, and 3) identified factors including diets and infections that modulate PPARα activity and would be hypothesized to affect chemical-induced PPARα activity.

Δ(9)-THC modulation of fatty acid 2-hydroxylase (FA2H) gene expression: possible involvement of induced levels of PPARα in MDA-MB-231 breast cancer cells

We recently reported that Δ(9)-tetrahydrocannabinol (Δ(9)-THC), a major cannabinoid component in Cannabis Sativa (marijuana), significantly stimulated the expression of fatty acid 2-hydroxylase (FA2H) in human breast cancer MDA-MB-231 cells. Peroxisome proliferator-activated receptor α (PPARα) was previously implicated in this induction. However, the mechanisms mediating this induction have not been elucidated in detail. We performed a DNA microarray analysis of Δ(9)-THC-treated samples and showed the selective up-regulation of the PPARα isoform coupled with the induction of FA2H over the other isoforms (β and γ). Δ(9)-THC itself had no binding/activation potential to/on PPARα, and palmitic acid (PA), a PPARα ligand, exhibited no stimulatory effects on FA2H in MDA-MB-231 cells; thus, we hypothesized that the levels of PPARα induced were involved in the Δ(9)-THC-mediated increase in FA2H. In support of this hypothesis, we herein demonstrated that; (i) Δ(9)-THC activated the basal transcriptional activity of PPARα in a concentration-dependent manner, (ii) the concomitant up-regulation of PPARα/FA2H was caused by Δ(9)-THC, (iii) PA could activate PPARα after the PPARα expression plasmid was introduced, and (iv) the Δ(9)-THC-induced up-regulation of FA2H was further stimulated by the co-treatment with L-663,536 (a known PPARα inducer). Taken together, these results support the concept that the induced levels of PPARα may be involved in the Δ(9)-THC up-regulation of FA2H in MDA-MB-231 cells.

Association between triglyceride and high-density lipoprotein cholesterol change following fibrate therapy

BACKGROUND

Debate surrounding the role of fibrates has followed mixed outcomes from several randomised controlled trials. Subgroup analysis of even the negative trials reveals significant reduction in cardiovascular risk amongst patients with low HDL-C and high TG. We previously described factors associated with HDL-C change following fibrates. As fibrates influence both HDL-C and TG levels via their action on PPAR-α, we now wished to study TG change following fibrate therapy and any associations with baseline and change in HDL-C and TC levels.

METHODS

Data was collected from case notes of patients started on fibrates (n=248) between 2002 and 2008 in the lipid clinics at Heart of England NHS Foundation Trust. Regression analyses were carried out to determine factors associated with changes in TG.

RESULTS

Multiple regression analysis revealed that TG change was associated with pre-treatment TG (p<0.001) and TC levels (p=0.029). The association between TG change and pre-treatment TG remained significant when all factors including gender, concurrent statin treatment, diabetes and baseline HDL-C were entered into the regression model. Our previous study demonstrated significant post-fibrate HDL-C change in the group with baseline HDL-C values <1.0mmol/l. In our present study significant TG reduction was observed regardless of the baseline patient characteristics including HDL-C levels.

CONCLUSIONS

The actions of fibrates are considered to be mediated via PPAR-α, but our data suggest that the effects on TG and HDL-C are different. Thus, the mechanisms mediating the changes of these lipids following fibrate treatment may vary.

[Peroxisome proliferator-activated receptors-alpha (PPAR-alpha) and chronic heart failure: is there a reason to discuss the metabolic strategy of treatment?]

Despite improved prognosis in patients with heart failure (HF) treated with neurohumoral activation-suppressing drugs (such as angiotensin-converting enzyme inhibitors, angiotensin II receptor antagonists, beta-adrenergic receptor antagonists, aldosterone receptor antagonists), mortality from heart failure remains high, myocardial contractile dysfunction progresses, and the left ventricle becomes enlarged. This leads to the need to elaborate novel approaches to treating HF. The latter is obviously due to impaired myocardial energy substrate metabolism. The mechanisms underlying this phenomenon are numerous and complex. These include reduced myocardial expression and activity of key free fatty acid oxidative enzymes. The expression of these enzymes is controlled by peroxisome proliferator-activated receptors-alpha (PPAR-alpha). Thus, PPAR-alpha activation is a direct method to regulate myocardial fatty acid metabolism. Evidence for the efficiency of therapeutic strategies based on the fact that fatty acid metabolism may be modulated is controversial, which indicates that there may be more complex molecular/biochemical changes than supposed before. The data available in the literature suggest the promises of the above strategy and its serious therapeutic potential.

Screening of medicinal plants for PPARα and PPARγ activation and evaluation of their effects on glucose uptake and 3T3-L1 adipogenesis

Medicinal plants are a rich source of ligands for nuclear receptors. The present study was aimed to screen a collection of plant extracts for PPARα/γ-activating properties and identify the active extract that can stimulate cellular glucose uptake without enhancing the adipogenesis. A reporter gene assay was performed to screen ethanolic extracts of 263 plant species, belonging to 94 families, for activation of PPARα and PPARγ. Eight extracts showed activation of PPARγ, while 22 extracts showed activation of PPARα. The extracts of five plants (Daphne gnidium, Illicium anisatum, Juniperus virginiana, Terminalia chebula, and Thymelaea hirsuta) showed activation of both PPARα and PPARγ and out of them, D. gnidium and T. hirsuta markedly increased PPARα/γ protein expression. All five extracts showed an increase in cellular glucose uptake. Of the five dual agonists, T. chebula and T. hirsuta did not show any increase in differentiation of 3T3-L1 preadipocytes, but I. anisatum caused an increase in adipogenesis, while D. gnidium and J. virginiana were toxic to adipocytes. The adipogenic effect of rosiglitazone was antagonized by T. chebula and T. hirsuta. It was concluded that T. hirsuta and T. chebula retain the property of elevating glucose uptake as PPARα/γ dual agonists without the undesired side effect of adipogenesis. This is the first report to reveal the PPARα/γ dual agonistic action and glucose uptake enhancing property of T. hirsuta and T. chebula.

Estrogen therapy attenuates adiposity markers in spontaneously hypertensive rats

Ovarian hormones modulate the metabolism of adipose cells and present a protective effect against hypertension. The aim of this study was to compare the effect of estradiol on adiposity markers in spontaneously hypertensive rats. Ovariectomized spontaneously hypertensive rats treated with estradiol (5 μg/100 g/day), three weeks after ovariectomy, presented decreased blood pressure and insulin levels and increased hepatic glycogen content. Periuterine or mesenteric adipocytes from treated animals were smaller as compared to vehicle treated group, whereas no differences were observed in relation to the number of cells. Basal rates of glycerol release were higher only in periuterine adipocytes of treated rats. The increment of glycerol release over basal values in response to isoproterenol was 400% and 440%, 283% and 330% for vehicle and estradiol treated periuterine and mesenteric adipocytes, respectively. The estradiol treated group was more sensitive to insulin inhibition of isoproterenol-stimulated lipolysis than the control animals. The lipoprotein lipase activity decreased after treatment, only in periuterine adipose tissue. Estradiol administration increased basal and insulin-stimulated rates of glucose transport in adipocytes of both sites, although the values obtained by periuterine were higher than those observed for mesenteric adipocytes. Both adipose tissues from treated animals exhibited a decreased expression of the peroxisome proliferator-activated receptor-γ, but an increased expression of peroxisome proliferator-activated receptor-α in liver. These findings suggest that estrogen administration attenuates adiposity markers of spontaneously hypertensive rats as a result of the decreased expression levels of peroxisome proliferator-activated receptor-γ in adipose tissue and increased expression of peroxisome proliferator-activated receptor-α in liver.

[Effects of ursolic acid in ameliorating insulin resistance in liver of KKAy mice via peroxisome proliferator-activated receptors α and γ]

OBJECTIVE

To explore the effects and mechanism of ursolic acid in improving hepatic insulin resistance in KKAy mice with spontaneous type 2 diabetes.

METHODS

Thirty-five KKAy mice were divided into five groups according to the randomized block design, namely, control, rosiglitazone, fenofibrate, and high- and low-dose ursolic acid groups with seven mice in each group. C57BL/6J mice were used as the normal control group. At the end of the 4th week, free fatty acid (FFA), tumor necrosis factor-α (TNF-α) and adiponectin contents in serum were detected by enzyme-linked immunosorbent assay; the protein expressions of phosphoenolpyruvate carboxykinase (PEPCK), insulin receptor substrate-2 (IRS-2) and glucose transport factor-2 (GLUT-2) were detected by Western blot method; the mRNA expressions of PEPCK, IRS-2 and GLUT-2 were detected by real-time polymerase chain reaction; the expressions of peroxisome proliferator-activated receptor α (PPARα) and peroxisome proliferator-activated receptor γ (PPARγ) in liver tissue were detected by immunohistochemical method.

RESULTS

After four weeks of intervention, the contents of FFA, TNF-α and adiponectin in serum of the high-dose ursolic acid group had changed, showing statistically significant difference compared to those of the control group (P<0.01); high dose of ursolic acid had depressant effect on the expressions of PEPCK protein and PEPCK mRNA (P<0.01); low dose of ursolic acid depressed the expression of PEPCK mRNA and induced phosphorylation of IRS-2 in the liver (P<0.05); both high and low dose of ursolic acid improved the expression of PPARα in the liver (P<0.01).

CONCLUSION

The effects of ursolic acid in improving hepatic insulin resistance in KKAy mice with spontaneous type 2 diabetes may be closely related to affecting the contents of FFA, TNF-α and adiponectin, improving the expression of PPARα protein, regulating transcription of PEPCK protein and inducing phosphorylation of IRS-2.

Inhibitory effect of α-lipoic acid on platelet aggregation is mediated by PPARs

Peroxisome proliferator-activated receptors (PPARs) isoforms (α, β/δ, and γ are present in human platelets, and activation of PPARs inhibits platelet aggregation. α-Lipoic acid (ALA), occurring naturally in human food, has been reported to exhibit an antiplatelet activity. However, the mechanisms underlying ALA-mediated inhibition of platelet aggregation remain unknown. The aim of this study was to investigate whether the antiplatelet activity of ALA is mediated by PPARs. ALA itself significantly induced PPARα/γ activation in platelets and increased intracellular amounts of PPARα/γ by blocking PPARα/γ secretion from arachidonic acid (AA)-activated platelets. Moreover, ALA significantly inhibited AA-induced platelet aggregation, Ca(2+) mobilization, and cyclooxygenase-1 (COX-1) activity, but increased cyclic AMP production in rabbit washed platelets. Importantly, ALA also enhanced interaction of PPARα/γ with protein kinase Cα (PKCα) and COX-1 accompanied by an inhibition of PKCα activity in resting and AA-activated platelets. However, the above effects of ALA on platelets were markedly reversed by simultaneous addition of selective PPARα antagonist (GW6471) or PPARγ antagonist (GW9662). Taken together, the present study provides a novel mechanism by which ALA inhibition of platelet aggregation is mediated by PPARα/γ-dependent processes, which involve interaction with PKCα and COX-1, increase of cyclic AMP formation, and inhibition of intracellular Ca(2+) mobilization.

PPARα activation by culinary herbs and spices

Hyper- and dyslipidemia are risk factors for cardiovascular disease, the primary cause of death in industrialized countries. Peroxisome proliferators-activated receptor (PPAR)α activation is involved in various mechanisms that improve the lipid profile. We tested various plant extracts and their compounds to determine whether they stimulated PPARα activity in vitro. Out of 34 tested plant extracts, nine exhibited low to moderate PPARα transactivation, including caraway, chili pepper, nutmeg, licorice, black and white pepper, paprika, coriander, saffron, and stevia tea. The active components of black pepper and chili pepper, piperine, and capsaicin exerted the highest transactivational activities with EC₅₀ values of 84 µM and 49 µM, respectively. The chalcones, including 2-hydroxychalcone, 2'-hydroxychalcone, 4-hydroxychalcone, and 4-methoxychalcone, moderately transactivated PPARα. Resveratrol and apigenin only slightly transactivated PPARα. These results suggest that a diet rich in fruit, herbs, and spices provides a number of PPARα agonists that might contribute to an improved lipid profile.

Effects of fatty acid amide hydrolase inhibition on neuronal responses to nicotine, cocaine and morphine in the nucleus accumbens shell and ventral tegmental area: involvement of PPAR-alpha nuclear receptors

The endocannabinoid system regulates neurotransmission in brain regions relevant to neurobiological and behavioral actions of addicting drugs. We recently demonstrated that inhibition by URB597 of fatty acid amide hydrolase (FAAH), the main enzyme that degrades the endogenous cannabinoid N-acylethanolamine (NAE) anandamide and the endogenous non-cannabinoid NAEs oleoylethanolamide and palmitoylethanolamide, blocks nicotine-induced excitation of ventral tegmental area (VTA) dopamine (DA) neurons and DA release in the shell of the nucleus accumbens (ShNAc), as well as nicotine-induced drug self-administration, conditioned place preference and relapse in rats. Here, we studied whether effects of FAAH inhibition on nicotine-induced changes in activity of VTA DA neurons were specific for nicotine or extended to two drugs of abuse acting through different mechanisms, cocaine and morphine. We also evaluated whether FAAH inhibition affects nicotine-, cocaine- or morphine-induced actions in the ShNAc. Experiments involved single-unit electrophysiological recordings from DA neurons in the VTA and medium spiny neurons in the ShNAc in anesthetized rats. We found that URB597 blocked effects of nicotine and cocaine in the ShNAc through activation of both surface cannabinoid CB1-receptors and alpha-type peroxisome proliferator-activated nuclear receptor. URB597 did not alter the effects of either cocaine or morphine on VTA DA neurons. These results show that the blockade of nicotine-induced excitation of VTA DA neurons, which we previously described, is selective for nicotine and indicate novel mechanisms recruited to regulate the effects of addicting drugs within the ShNAc of the brain reward system.

Protective effect of Chinese prescription Kangen-karyu and its crude drug Tanjin against age-related lipidosis in rats

We have investigated the effect of the Chinese prescription Kangen-karyu and its crude drug Tanjin against age-related lipidosis in-vivo in a rat model. The serum and hepatic triglyceride levels were remarkably elevated in 12-month-old compared with two-month-old rats. However, the administration of Kangen-karyu and Tanjin extracts significantly decreased these levels. This suggested a protective role against related pathological conditions as well as hyperlipidaemia. On the other hand, the reduction of the levels of adiponectin in serum with ageing did not show significant changes in rats given diets supplemented with Kangen-karyu and Tanjin extracts. Furthermore, the expression of transcription factors in nuclear hepatic tissue related to lipid metabolism was investigated. The decline in the expression of nuclear peroxisome proliferator-activated receptor α protein in hepatic tissue with age was ameliorated by the administration of Kangen-karyu and Tanjin supplements. On the other hand, the overexpression of sterol regulatory element-binding proteins (SREBP)-1 and SREBP-2 in old rats compared with young rats showed a tendency to decrease with Kangen-karyu and Tanjin administration. The decline of hepatic function with ageing was attenuated by Kangen-karyu and Tanjin, suggesting the beneficial role of Kangen-karyu and Tanjin on lipid metabolism through the improvement of hepatic function. This study has demonstrated that Kangen-karyu and Tanjin inhibited the accumulation of triglyceride with regulation of related protein expressions and they improved hepatic function. Evidence has been provided for the anti-ageing activity of Kangen-karyu and its crude drug Tanjin against age-related lipidosis.

Iridoids from Fraxinus excelsior with adipocyte differentiation-inhibitory and PPARalpha activation activity

Two new secoiridoid glucosides, excelsides A (1) and B (2), were isolated from the seeds of Fraxinus excelsior. Their structures were elucidated as (2S,4S,3E)-methyl 3-ethylidene-4-(2-methoxy-2-oxoethyl)-2-[(6-O-beta-D-glucopyranosyl-beta-d-glucopyranosyl)oxy]-3,4-dihydro-2H-pyran-5-carboxylate and (2S,4S,3E)-methyl 3-ethylidene-4-{2-[2-(4-hydroxyphenyl)ethyl]oxy-2-oxoethyl}-2-[(6-O-beta-d-glucopyranosyl-beta-d-glucopyranosyl)oxy]-3,4-dihydro-2H-pyran-5-carboxylate, respectively, on the basis of NMR and MS data. Eight known compounds were identified as nuzhenide (3), GI3 (4), GI5 (5), ligstroside (6), oleoside 11-methyl ester (7), oleoside dimethyl ester (8), 1'''-O-beta-D-glucosylformoside (9), and salidroside (10). Compounds 1-9 inhibited adipocyte differentiation in 3T3-L1 cells. Dilutions of the aqueous extract of F. excelsior (1:10,000) as well as compounds 2, 3, 4, 5, and 8 activated the peroxisome proliferator-mediated receptor-alpha (PPARalpha) reporter cell system in the range of 10(-4) M, compared to 10(-7)-10(-8) M for the synthetic PPARalpha activator, WY14,643. Both biological activity profiles support the hypothesis that inhibition of adipocyte differentiation and PPARalpha-mediated mechanisms might be relevant pathways for the antidiabetic activity of F. excelsior extract.

Glucose represses PPARα gene expression via AMP-activated protein kinase but not via p38 mitogen-activated protein kinase in the pancreatic β-cell

BACKGROUND

Peroxisome proliferator-activated receptor α (PPARα) regulates the expression of fatty acid metabolism genes and is thought to play a role in the regulation of insulin secretion and lipid detoxification. We have examined the mechanism whereby glucose decreases PPARα gene expression in the pancreatic β-cell.

METHODS

INS832/13 β-cell and isolated rat islets were incubated at 3 and 20 mM glucose for 18 h in the absence or presence of adenosine monophosphate (AMP)-activated protein kinase (AMPK) activators and inhibitors, as well as p38 mitogen-activated protein kinase (p38 MAPK) inhibitors. In another set of experiments, INS832/13 were infected with an adenovirus expressing a dominant-negative form of AMPK. PPARα expression levels were measured by reverse transcription polymerase chain reaction and Western blot.

RESULTS

Elevated glucose reduced the abundance of the PPARα transcript and protein, and its target genes acyl-coenzyme A (CoA) oxidase (ACO) and uncoupling protein 2 (UCP-2) in INS832/13 β-cell and isolated rat islets. Glucose reduced AMPK activity, while the AMPK activators 5-amino-4-imidazolecarboxamide riboside and metformin increased PPARα expression and suppressed the action of glucose. By contrast, the AMPK inhibitor compound C mimicked the glucose effect. A dominant negative form of AMPKα reduced the PPARα, ACO and UCP-2 transcripts to the same extent as elevated glucose. Pharmacological evidence indicated that glucose-regulated PPARα expression does not involve p38 MAPK, a target of AMPK in several cell types.

CONCLUSIONS

The results indicate that glucose represses PPARα gene expression via AMPK, but not via p38 MAPK in the β-cell.

Pomegranate flower ameliorates fatty liver in an animal model of type 2 diabetes and obesity

AIMS OF THE STUDY

Fatty liver is the most common cause of abnormal liver function tests. We investigated the effect and its underlying mechanism of pomegranate flower (PGF), a traditional antidiabetic medicine, on fatty liver.

MATERIALS AND METHODS

At the endpoint of treatment of male Zucker diabetic fatty (ZDF) rats with PGF extract (500 mg/kg, p.o. x 6 weeks), liver weight index, hepatic lipid contents (enzymatic colorimetric methods) and droplet accumulation (Oil Red O staining) were determined. Gene profiles (RT-PCR) were analyzed in the liver of ZDF rats and in human liver-derived HepG2 cell line.

RESULTS

PGF-treated ZDF rats showed reduced ratio of liver weight to tibia length, hepatic triglyceride contents and lipid droplets. These effects were accompanied by enhanced hepatic gene expression of peroxisome proliferator-activated receptor (PPAR)-alpha, carnitine palmitoyltransferase-1 and acyl-CoA oxidase (ACO), and reduced stearoyl-CoA desaturase-1. In contrast, PGF showed minimal effects on expression of genes responsible for synthesis, hydrolysis or uptake of fatty acid and triglycerides. PGF treatment also increased PPAR-alpha and ACO mRNA levels in HepG2 cells.

CONCLUSION

Our findings suggest that this Unani medicine ameliorates diabetes and obesity-associated fatty liver, at least in part, by activating hepatic expression of genes responsible for fatty acid oxidation.

Activation of mouse and human peroxisome proliferator-activated receptor alpha by perfluoroalkyl acids of different functional groups and chain lengths

Perfluoroalkyl acids (PFAAs) are surfactants used in consumer products and persist in the environment. Some PFAAs elicit adverse effects on rodent development and survival. PFAAs can activate peroxisome proliferator-activated receptor alpha (PPARalpha) and may act via PPARalpha to produce some of their effects. This study evaluated the ability of numerous PFAAs to induce mouse and human PPARalpha activity in a transiently transfected COS-1 cell assay. COS-1 cells were transfected with either a mouse or human PPARalpha receptor-luciferase reporter plasmid. After 24 h, cells were exposed to either negative controls (water or dimethyl sulfoxide, 0.1%); positive control (WY-14643, PPARalpha agonist); perfluorooctanoic acid or perfluorononanoic acid at 0.5-100 microM; perfluorobutanoic acid, perfluorohexanoic acid, perfluorohexane sulfonate, or perfluorodecanoic acid (PFDA) at 5-100 microM; or perfluorobutane sulfonate or perfluorooctane sulfonate at 1-250 microM. After 24 h of exposure, luciferase activity from the plasmid was measured. Each PFAA activated both mouse and human PPARalpha in a concentration-dependent fashion, except PFDA with human PPARalpha. Activation of PPARalpha by PFAA carboxylates was positively correlated with carbon chain length, up to C9. PPARalpha activity was higher in response to carboxylates compared to sulfonates. Activation of mouse PPARalpha was generally higher compared to that of human PPARalpha. We conclude that, in general, (1) PFAAs of increasing carbon backbone chain lengths induce increasing activity of the mouse and human PPARalpha with a few exceptions, (2) PFAA carboxylates are stronger activators of mouse and human PPARalpha than PFAA sulfonates, and (3) in most cases, the mouse PPARalpha appears to be more sensitive to PFAAs than the human PPARalpha in this model.

The Korean traditional medicine Gyeongshingangjeehwan inhibits obesity through the regulation of leptin and PPARalpha action in OLETF rats

Gyeongshingangjeehwan (GGEx), which comprises Liriope platyphylla F.T. Wang & T. Tang (Liliaceae), Platycodongrandiflorum A. DC. (Campanulaceae), Schisandrachinensis K. Koch (Magnoliaceae), and Ephedra sinica Stapf (Ephedraceae), has traditionally been used as an anti-obesity drug in Korean local clinics, although there is no evidence concerning the scientific analyses of its effects and mechanism(s) of action. Thus, we investigated the effects of GGEx on obesity, as well as the mechanism by which GGEx functions, in Otsuka Long-Evans Tokushima Fatty (OLETF) male rats. Compared with obese OLETF control rats, administration of GGEx for 8 weeks significantly decreased food intake and plasma leptin levels as well as body weight gain and abdominal fat in OLETF rats. GGEx treatment not only decreased circulating triglycerides, but also inhibited lipid accumulation in the liver. GGEx increased the hepatic mRNA levels of PPARalpha target genes responsible for fatty acid beta-oxidation. Consistent with the in vivo data, GGEx elevated PPARalpha reporter gene expression in NMu2Li liver cells. These results suggest that GGEx may effectively prevent obesity and hypertriglyceridemia in part through the inhibition of feeding and the activation of hepatic PPARalpha.

PPAR-alpha: therapeutic role in diabetes-related cardiovascular disease

Among individuals with diabetes mellitus, cardiovascular disease remains the leading cause of death, despite the many treatment modalities that have been developed over time. The PPAR family, including PPAR-alpha, play important roles in glucose and lipid metabolism and atherosclerosis and thus are potential therapeutic targets. Fibrates act upon PPAR-alpha and appear to target the typical dyslipidaemia of diabetes. Several large prospective clinical trials have shown both primary prevention and secondary prevention benefit with fibrates, although they only had small subgroups of patients with diabetes. The first large outcome study to exclusively study those with diabetes was the FIELD study, which showed no reduction in the primary cardiovascular end-point and only some benefit in the secondary end-point. There are many potential explanations for these results; however, it would appear that at present, there is no role for fibrates as monotherapy for the reduction of cardiovascular risk among those with diabetes. However, their potential role in combination with statin therapy remains to be further elucidated with ongoing studies.

Nuclear receptors as drug targets in obesity, dyslipidemia and atherosclerosis

Nuclear hormone receptors, including peroxisome proliferator-activated receptors (PPARs), liver X receptors (LXRs), and the farnesoid X receptor (FXR), are transcription factors involved in the regulation of essential metabolic functions, including glucose and lipid metabolism, reverse cholesterol transport, and the regulation of bile acids. This review summarizes new developments in the use of PPAR, LXR and FXR agonists for the treatment of obesity and cardiovascular diseases, including dyslipidemia and atherosclerosis. Currently available drugs and future areas of research for new therapies are also discussed.

Regulation of obesity and lipid disorders by herbal extracts from Morus alba, Melissa officinalis, and Artemisia capillaris in high-fat diet-induced obese mice

Melissa officinalis L. (Labiatae), Morus alba L. (Moraceae), and Artemisia capillaris Thunb. (Compositae) are suggested to be involved in the regulation of hyperlipidemia. We hypothesized that Ob-X, a mixture of three herbs, Morus alba, Melissa officinalis and Artemisia capillaris [corrected] improves lipid metabolism, body weight gain and adiposity and that peroxisome proliferator-activated receptor alpha (PPARalpha) is associated with these events. Mice fed a high-fat diet for 12 weeks exhibited increases in body weight gain and adipose tissue mass compared with mice fed a low fat diet. However, feeding a high-fat diet supplemented with Ob-X significantly reduced these effects. Ob-X treatment also decreased the circulating levels of triglycerides and total cholesterol, and inhibited hepatic lipid accumulation. Ob-X supplementation was found to increase the hepatic mRNA levels of PPARalpha target enzymes responsible for fatty acid beta-oxidation. Moreover, Ob-X elevated the endogenous expression of a luciferase reporter gene containing three copies of a PPAR response element (PPRE) in NMu2Li liver cells. These data demonstrate that Ob-X regulates body weight gain, adipose tissue mass, and lipid metabolism in part through changes in the expression of hepatic PPARalpha target genes.

Pomegranate flower: a unique traditional antidiabetic medicine with dual PPAR-alpha/-gamma activator properties

PPARs are transcription factors belonging to the superfamily of nuclear receptors. PPAR-alpha is involved in the regulation of fatty acid (FA) uptake and oxidation, inflammation and vascular function, while PPAR-gamma participates in FA uptake and storage, glucose homeostasis and inflammation. The PPARs are thus major regulators of lipid and glucose metabolism. Synthetic PPAR-alpha or PPAR-gamma agonists have been widely used in the treatment of dyslipidaemia, hyperglycaemia and their complications. However, they are associated with an incidence of adverse events. Given the favourable metabolic effects of both PPAR-alpha and PPAR-gamma activators, as well as their potential to modulate vascular disease, combined PPAR-alpha/-gamma activation has recently emerged as a promising concept, leading to the development of mixed PPAR-alpha/-gamma activators. However, some major side effects associated with the synthetic dual activators have been reported. It is unclear whether this is a specific effect of the particular synthetic compounds or a class effect. To date, a medication that may combine the beneficial metabolic effects of PPAR-alpha and PPAR-gamma activation with fewer undesirable side effects has not been successfully developed. Pomegranate plant parts are used traditionally for the treatment of various disorders. However, only pomegranate flower has been prescribed in Unani and Ayurvedic medicines for the treatment of diabetes. This review provides a new understanding of the dual PPAR-alpha/-gamma activator properties of pomegranate flower in the potential treatment of diabetes and its associated complications.

Nonalcoholic steatohepatitis (NASH) in ob/ob mice treated with yo jyo hen shi ko (YHK): effects on peroxisome proliferator-activated receptors (PPARs) and microsomal triglyceride transfer protein (MTP)

YHK has antioxidant properties, has a hypoglycemic effect, and may reduce plasma lipid levels. In this study, we examined the hepatic expression of PPAR-alpha and -gamma and MTP in ob/ob mice receiving or not receiving YHK. Ob/ob mice were assigned to receive oral YHK (20 mg/kg/day) fed solution (methionine/choline-deficient [MCD] diet+YHK group) or vehicle (MCD group) by gavage for 4 weeks. Liver fragments were collected for histologic examination and mRNA isolation. PPAR-alpha and -gamma and MTP gene expression was examined by RT-qPCR. YHK treatment was associated with NASH prevention, weight loss, and reduction of visceral fat and of serum concentrations of aminotransferases in comparison to the MCD group. YHK promoted an increment in PPAR-alpha and MTP and a decrement in PPAR-gamma mRNA contents. These findings suggest that modulation of PPAR-alpha and -gamma and MTP RNA expression may be implicated in the protective effect of YHK in experimental NASH, limiting hepatocyte lipid accumulation.

PPAR activation: a new target for the treatment of hypertension

Hypertensive patients are at increased risk for cardiovascular complications. Inhibition of different pathophysiological mechanisms involved in hypertension and hypertension-related target organ damage may revert or prevent the progression of the pathological changes observed and reduce the occurrence of cardiovascular events. One of the new targets that may prevent or regress hypertensive vascular, renal, and perhaps brain changes in hypertension is the activation of nuclear receptors that have metabolic effects but also exert antiinflammatory action, the peroxisome proliferator activator receptor (PPAR) activators alpha and gamma. This review will discuss some of the evidence, both experimental and clinical, that suggests that activation of PPAR alpha and/or gamma in hypertension may exert beneficial cardiovascular protective effects.

The novel mechanism of recombinant human ciliary neurotrophic factor on the anti-diabetes activity

In a previous study, the ciliary neurotrophic factor (CNTF) were demonstrated to lead to weight-loss partly by up-regulating the energy metabolism and the expression of uncoupling protein-1, mitochondrial transcription factor A and nuclear respiratory factor-1 in adipose tissues or muscle. To investigate the up-stream regulators of the expression, recombinant human CNTF (rhCNTF) (0.1, 0.3 and 0.9 mg/kg/day subcutaneously) were administered to KK-Ay mice for 30 days, resulting in reduction of perirenal fat mass, serum free fatty acids and islet triacylglycerol; furthermore, the values of oral glucose tolerance test were found improved. In brown adipose tissues, the gene expressions of peroxisome proliferator-activated receptor alpha (PPARalpha) and peroxisome proliferator-activated receptor coactivator-1 alpha (PGC-1alpha) were found to be up-regulated by rhCNTF. To the best of our knowledge, the changes of gene expression of PPARalpha and PGC-1alpha represent new insights into the mechanisms of anti-diabetes by rhCNTF. In addition, the activity of mitochondrial complexII was found to be increased by rhCNTF. Stimulation of PPARalpha, PGC-1alpha, uncoupling protein-1 and enhanced activity of mitochondrial complex II may be associated with the effects of anti-diabetes. The present study indicates new mechanisms of the activity and mechanisms on anti-diabetes of rhCNTF, which may be a novel anti-diabetes reagent partly acting by enhancing energy metabolism.

Activation of peroxisome proliferator-activated receptor-alpha by fenofibrate prevents myocardial dysfunction during endotoxemia in rats

OBJECTIVE

To investigate the effects of fenofibrate, an activator of peroxisome proliferator-activated receptor-alpha, on cardiac function in a rat endotoxemia model.

DESIGN

Prospective, randomized, controlled study.

SETTING

University research laboratory.

SUBJECTS

Three-month-old male Wistar rats.

INTERVENTIONS

Animals were fed with standard diet containing no drug or fenofibrate (0.2%) for 14 days. They were then injected intravenously with either 5 mg/kg lipopolysaccharide (LPS and fenofibrate + LPS groups) or saline (control and fenofibrate groups).

MEASUREMENTS AND MAIN RESULTS

In the LPS group, body weight loss, metabolic acidosis, and thrombocytopenia confirmed presence of systemic endotoxemia. LPS administration resulted in an early peak in plasma tumor necrosis factor-alpha, decreased cardiac contractility (isolated and perfused heart), reduced myofilament Ca2+ sensitivity (Triton-skinned cardiac fibers), and increased left ventricular nitric oxide (NO) end-oxidation products (NO(x) and NO2), without evidence of myocardial oxidative stress (thiobarbituric acid-reactive substances and antioxidant enzyme activities). Fenofibrate pretreatment (fenofibrate + LPS group) did not alter signs of endotoxemia but prevented reductions in both cardiac contractility and myofilament Ca2+ sensitivity. The peak of plasma tumor necrosis factor-alpha was attenuated, whereas myocardial NO(x) and NO2 remained similar to the LPS group. Oxidative stress was suggested from moderate increase in cardiac thiobarbituric acid-reactive substances and reduced glutathione peroxidase activity.

CONCLUSION

Fenofibrate, an activator of peroxisome proliferator-activated receptor-alpha, may prevent endotoxemia-induced cardiac dysfunction and reduction in myofilament Ca2+ sensitivity. Our data also suggest a mediating role for early peak plasma tumor necrosis factor-alpha, but not for myocardial NO production or oxidative stress.

Statins activate peroxisome proliferator-activated receptor gamma through extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase-dependent cyclooxygenase-2 expression in macrophages

Both statins and peroxisome proliferator-activated receptor (PPAR)gamma ligands have been reported to protect against the progression of atherosclerosis. In the present study, we investigated the effects of statins on PPARgamma activation in macrophages. Statins increased PPARgamma activity, which was inhibited by mevalonate, farnesylpyrophosphate, or geranylgeranylpyrophosphate. Furthermore, a farnesyl transferase inhibitor and a geranylgeranyl transferase inhibitor mimicked the effects of statins. Statins inhibited the membrane translocations of Ras, RhoA, Rac, and Cdc42, and overexpression of dominant-negative mutants of RhoA (DN-RhoA) and Cdc42 (DN-Cdc42), but not of Ras or Rac, increased PPARgamma activity. Statins induced extracellular signal-regulated kinase (ERK)1/2 and p38 mitogen-activated protein kinase (MAPK) activation. However, DN-RhoA and DN-Cdc42 activated p38 MAPK, but not ERK1/2. ERK1/2- or p38 MAPK-specific inhibitors abrogated statin-induced PPARgamma activation. Statins induced cyclooxygenase (COX)-2 expression and increased intracellular 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) levels through ERK1/2- and p38 MAPK-dependent pathways, and inhibitors or small interfering RNA of COX-2 inhibited statin-induced PPARgamma activation. Statins also activate PPARalpha via COX-2-dependent increases in 15d-PGJ(2) levels. We further demonstrated that statins inhibited lipopolysaccharide-induced tumor necrosis factor alpha or monocyte chemoattractant protein-1 mRNA expression, and these effects by statins were abrogated by the PPARgamma antagonist T0070907 or by small interfering RNA of PPARgamma or PPARalpha. Statins also induced ATP-binding cassette protein A1 or CD36 mRNA expression, and these effects were suppressed by small interfering RNAs of PPARgamma or PPARalpha. In conclusion, statins induce COX-2-dependent increase in 15d-PGJ(2) level through a RhoA- and Cdc42-dependent p38 MAPK pathway and a RhoA- and Cdc42-independent ERK1/2 pathway, thereby activating PPARgamma. Statins also activate PPARalpha via COX-2-dependent pathway. These effects of statins may explain their antiatherogenic actions.

n-3 Fatty acids preserve insulin sensitivity in vivo in a peroxisome proliferator-activated receptor-alpha-dependent manner

Recent studies have suggested that n-3 fatty acids, abundant in fish oil, protect against high-fat diet-induced insulin resistance through peroxisome proliferator-activated receptor (PPAR)-alpha activation and a subsequent decrease in intracellular lipid abundance. To directly test this hypothesis, we fed PPAR-alpha null and wild-type mice for 2 weeks with isocaloric high-fat diets containing 27% fat from either safflower oil or safflower oil with an 8% fish oil replacement (fish oil diet). In both genotypes the safflower oil diet blunted insulin-mediated suppression of hepatic glucose production (P < 0.02 vs. genotype control) and PEPCK gene expression. Feeding wild-type mice a fish oil diet restored hepatic insulin sensitivity (hepatic glucose production [HGP], P < 0.002 vs. wild-type mice fed safflower oil), whereas in contrast, in PPAR-alpha null mice failed to counteract hepatic insulin resistance (HGP, P = NS vs. PPAR-alpha null safflower oil-fed mice). In PPAR-alpha null mice fed the fish oil diet, safflower oil plus fish oil, hepatic insulin resistance was dissociated from increases in hepatic triacylglycerol and acyl-CoA but accompanied by a more than threefold increase in hepatic diacylglycerol concentration (P < 0.0001 vs. genotype control). These data support the hypothesis that n-3 fatty acids protect from high-fat diet-induced hepatic insulin resistance in a PPAR-alpha-and diacylglycerol-dependent manner.

Gypenoside XLIX, a naturally occurring PPAR-alpha activator, inhibits cytokine-induced vascular cell adhesion molecule-1 expression and activity in human endothelial cells

Vascular cell adhesion molecule-1 (VCAM-1) is involved in several diseases, including chronic inflammation and atherosclerosis. Inhibition of the expression of this adhesion molecule is one of the key targets of anti-inflammatory, anti-cancer and anti-atherosclerotic drugs. Gynostemma pentaphyllum is a traditional medicine widely used in the treatment of respiratory inflammation, hyperlipidemia and atherosclerosis. However, its molecular mechanisms of action are still largely unknown. Gypenoside XLIX, a dammarane-type glycoside, is a prominent component of G. pentaphyllum. We have recently demonstrated Gypenoside XLIX to be a selective peroxisome proliferator-activated receptor (PPAR)-alpha activator. Here we demonstrate that Gypenoside XLIX concentration-dependently (0-300 microM) inhibited VCAM-1 promoter activity after induction by cytokine tumor necrosis factor (TNF)-alpha in human umbilical vein endothelial cells (HUVECs) transfected with promoter-reporter construct pVCAM-1-LUC. Furthermore, Gypenoside XLIX inhibited TNF-alpha-induced VCAM-1 mRNA and protein overexpression in HUVECs. The result of the enzyme immunoassay demonstrated that Gypenoside XLIX inhibited TNF-alpha-induced increase in cell surface VCAM-1 protein levels in HUVECs. In the present study we show that activities of Gypenoside XLIX are similar to those of Wy-14643, a potent synthetic PPAR-alpha activator. Furthermore, Gypenoside XLIX-induced inhibition on TNF-alpha-stimulated VCAM-1 promoter hyperactivity was completely abolished by a selective blocker of PPAR-alpha, MK-886. Thus, our findings suggest that Gypenoside XLIX inhibits cytokine-induced VCAM-1 overexpression and hyperactivity in human endothelial cells via a PPAR-alpha-dependent pathway. These data provide new insight into the rational basis of the use of the traditional Chinese herbal medicine G. pentaphyllum in the treatment of inflammatory and cardiovascular diseases, including atherosclerosis.

Synergistic vascular protective effects of combined low doses of PPARalpha and PPARgamma activators in angiotensin II-induced hypertension in rats

BACKGROUND AND PURPOSE

Protective cardiovascular effects of peroxisome proliferator activated receptor (PPAR)alpha and PPARgamma activators have been demonstrated. If used as vasoprotective agents in high risk vascular patients rather than for their metabolic benefits, these agents could be associated with unwanted side effects. As a proof of concept to support the use of combined low doses of PPARalpha and PPARgamma as vascular protective agents in high risk vascular patients, we tested the hypothesis that combined low doses of PPARalpha (fenofibrate) and PPARgamma (rosiglitazone) activators would provide vascular protective benefits similar to full individual doses of these PPAR agonists.

EXPERIMENTAL APPROACH

Male Sprague-Dawley rats infused with Ang II (120 ng kg(-1) min(-1)) were treated with rosiglitazone (1 or 2 mg kg(-1) day(-1)) alone or concomitantly with fenofibrate (30 mg kg(-1) day(-1)) for 7 days. Thereafter, vessels was assessed on a pressurized myograph, while NAD(P)H oxidase activity was determined by lucigenin chemiluminescence. Inflammation was evaluated using ELISA for NFkappaB and Western blotting for adhesion molecules.

KEY RESULTS

Ang II-induced blood pressure increase, impaired acetylcholine-induced vasorelaxation, altered vascular structure, and enhanced vascular NAD(P)H oxidase activity and inflammation were significantly reduced by low dose rosiglitazone+fenofibrate.

CONCLUSIONS AND IMPLICATIONS

Combined low doses of PPARalpha and PPARgamma activators attenuated development of hypertension, corrected vascular structural abnormalities, improved endothelial function, oxidative stress, and vascular inflammation. These agents used in low-dose combination have synergistic vascular protective effects. The clinical effects of combined low-dose PPARalpha and PPARgamma activators as vascular protective therapy, potentially with reduced side-effects and drug interactions, should be assessed.

Effect of PPARalpha activation of macrophages on the secretion of inflammatory cytokines in cultured adipocytes

The relationship between adipocytes and infiltrated macrophages in fat tissue is important for the pathogenesis of insulin resistance through the activation of cytokines. Peroxisome proliferator-activated receptors (PPARs) play a role in the regulation of cytokine secretion in these cells. We studied the effect of the PPARalpha activation of macrophages on the modulation of the tumor necrosis factor alpha (TNFalpha) expression in adipocytes using a cell culture system. A conditioned medium of lipopolysaccharide (LPS)-stimulated RAW264.7 cells, a macrophage cell line, induced the level of TNFalpha mRNA in 3T3-L1 adipocytes. This effect was inhibited by the addition of neutralizing antibody against interleukin 6 (IL-6) in the conditioned medium or the preincubation of RAW264.7 cells with a specific PPARalpha agonist, K-111 (2,2-dichloro-12-(4-chlorophenyl)dodecanoic acid). K-111 reduced both the IL-6 production and mRNA expression in RAW264.7 cells, and its effect was stronger than that of rosiglitazone, a PPARgamma agonist. The activation of the stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK) pathway and nuclear factor kappa B (NF-kappaB) subunits of p65 was significantly inhibited by K-111. The blocking of IL-6 production through the SAPK/JNK pathway or by transfection with siRNA specific for IL-6 abolished the inhibitory effect of K-111 on the TNFalpha expression in the 3T3-L1 adipocytes. As a result, the IL-6 produced by RAW264.7 cells is an inducer of TNFalpha expression in 3T3-L1 adipocytes, and the IL-6 secretion is inhibited by the activation of PPARalpha. The PPARalpha activators may suppress the pathogenetical secretion of TNFalpha in the adipocytes through the functional modulation of the infiltrated macrophages.

Down-regulation of vinculin upon MK886-induced apoptosis in LN18 glioblastoma cells

Glioblastomas are a type of malignant brain tumor and are among the most difficult cancers to treat. One strategy to treat aggressive cancers is the use of drugs that target multiple signaling pathways. MK886 is a drug known to inhibit both 5- lipoxygenase-activating-protein (FLAP) and peroxisome proliferator activated receptor-alpha (PPAR-alpha). The objectives of this study were to investigate the ability of MK886 to induce apoptotic cell death in LN18 glioblastoma cells and to characterize the cell death mechanisms. MK886 induced massive apoptotic LN18 cell death that was manifested by the release of nucleosomes, annexinV binding to phosphatidylserine in the absence of nuclear staining, and changes in the fluorescent intensity of Mito Tracker Deep Red 633 indicating changes in mitochondrial oxidative function and mass. The alteration of the mitochondrial function implied that MK886 induced apoptosis in LN18 cells via a mitochondrial pathway. The broad caspases inhibitor ZVAD-FMK inhibited MK886-induced nucleosome release, but not annexinV binding or MK886-altered mitochondrial function. Real time RT-PCR demonstrated that LN18 cells expressed significant levels of FLAP and PPAR- alpha mRNAs. A low level of arachidonate 5-lipoxygenase (ALOX-5) mRNA was detected, but little, if any, arachidonate 12- lipoxygenase (ALOX-12) mRNA was present. In addition, MK886-induced apoptosis in LN18 cells was accompanied by a decrease in the protein and mRNA levels of vinculin, but not other focal adhesion proteins. In summary, the data presented here indicate that disruption of the actin-vinculin-cell-cytoskeleton matrix of the LN18 glioblastoma is a component of the MK886 induced apoptosis. In addition, MK886 treated LN18 cells could provide one model in which to investigate drugs that target lipoxygenase and PPAR-alpha pathways in the chemotherapeutic treatment of glioblastomas.

Peroxisome proliferator-activated receptor-alpha and glucocorticoids interactively regulate insulin secretion during pregnancy

We evaluated the impact of peroxisome proliferator-activated receptor (PPAR)alpha activation and dexamethasone treatment on islet adaptations to the distinct metabolic challenges of fasting and pregnancy, situations where lipid handling is modified to conserve glucose. PPARalpha activation (24 h) in vivo did not affect glucose-stimulated insulin secretion (GSIS) in nonpregnant female rats in the fasted state, although fasting suppressed GSIS. Dexamethasone treatment (5 days) of nonpregnant rats lowered the glucose threshold and augmented GSIS at high glucose; the former effect was selectively opposed by PPARalpha activation. Pregnancy-induced changes in GSIS were opposed by PPARalpha activation at day 19 of pregnancy. Dexamethasone treatment from day 14 to 19 of pregnancy did not modify the GSIS profile of perifused islets from 19-day pregnant rats but rendered the islet GSIS profile refractory to PPARalpha activation. During sustained hyperglycemia in vivo, dexamethasone treatment augmented GSIS in nonpregnant rats but limited further modification of GSIS by pregnancy. We propose that the effect of PPARalpha activation to oppose lowering of the glucose threshold for GSIS by glucocorticoids is important as part of the fasting adaptation, and modulation of the islet GSIS profile by glucocorticoids toward term facilitates the transition of maternal islet function from the metabolic demands of pregnancy to those imposed after parturition.

Peroxisome proliferator-activated receptor alpha activation during pregnancy severely impairs mammary lobuloalveolar development in mice

To identify the potential functions of peroxisome proliferator-activated receptor alpha (PPARalpha) in skin development, transgenic mice were generated to target constitutively activated PPARalpha (VP16PPARalpha) to the stratified epithelia by use of the keratin K5 promoter. In addition to marked alterations in epidermal development, the transgenic mice had a severe defect in lactation during pregnancy resulting in 100% pup mortality. In this study, the alteration of mammary gland development in these transgenic mice was investigated. The results showed that expression of the VP16PPARalpha transgene during pregnancy resulted in impaired development of lobuloalveoli, which is associated with reduced proliferation and increased apoptosis of mammary epithelia. Mammary epithelia from transgenic mice also showed a significant reduction in the expression of beta-catenin and a down-regulation of one of its target genes, cyclin D1, which is thought to be required for lobuloalveolar development. Furthermore, upon PPARalpha ligand treatment, similar effects on lobuloalveolar development were observed in wild-type mice, but not in PPARalpha-null mice. These findings suggest that PPARalpha activation has a marked influence in mammary lobuloalveolar development.

Peroxisome proliferator-activated receptor alpha activation decreases metastatic potential of melanoma cells in vitro via down-regulation of Akt

PURPOSE

Peroxisome proliferator-activated receptors (PPAR) regulate lipid and glucose metabolism but their anticancer properties have been recently studied as well. We previously reported the antimetastatic activity of the PPARalpha ligand, fenofibrate, against melanoma tumors in vivo. Here we investigated possible molecular mechanisms of fenofibrate anti metastatic action.

EXPERIMENTAL DESIGN

Monolayer cultures of mouse (B16F10) and human (SkMell88) melanoma cell lines, soft agar assay, and cell migration assay were used in this study. In addition, we analyzed PPARalpha expression and its transcriptional activity in response to fenotibrate by using Western blots and liciferase-based reporter system.

RESULTS

Fenofibrate inhibited migration of B16F10 and SkMel188 cells in Transwell chambers and colony formation in soft agar. These effects were reversed by PPAR inhibitor, GW9662. Western blot analysis revealed time-dependent down-regulation of Akt and extracellular signal-regulated kinase l/2 phosphorylation in fenofibrate-treated cells. A B16F10 cell line stably expressing constitutively active Akt mutant was resistant to fenofibrate. In contrast, Akt gene silencing with siRNA mimicked the fenofibrate action and reduced the migratory ability of B16F1O cells. In addition, fenofibrate strongly sensitized BI6FIO cells to the proapoptotic drug staurosporine, further supporting the possibility that fenofibrate-induced down-regulation of Akt function contributes to fenofibrate-mediated inhibition of metastatic potential in this experimental model.

CONCLUSIONS

Our results show that the PPAR-dependent antimetastatic activity of fenofibrate involves down-regulation of Akt phosphorylation and suggest that supplementation with this drug may improve the effectiveness of melanoma chemotherapy.