Peroxisome proliferator-activated receptors: nuclear control of metabolism

The adiponectin promoter activator NP-1 induces high levels of circulating TNFα and weight loss in obese (fa/fa) Zucker rats

Chronic NP-1 administration reduces body weight and hepatic steatosis despite induction of tolerance in adiponectin gene transcription with respect to the acute actions of this drug. This study explored the hypothesis that NP-1 could exert these effects through mechanisms independent of adiponectin. To this aim, we took advantage of the Zucker (fa/fa) rat model, which exhibits obesity, fatty liver and elevated leptin and adiponectin levels. Body weight and food intake were reduced after chronic NP-1 treatment. Plasma TNFα concentrations were elevated but no increase in adiponectin was found. Even so, NP-1 ameliorated fatty liver and corrected dyslipidemia by mechanisms probably associated with reduced feeding, transcription of Cpt1 and down-regulation of Hmgcr-CoA expression. In brown fat tissue NP-1 increased Dnmt1 (inhibitor of Adipoq) while it reduced Ucp1 expression and heat production, which excludes thermogenesis as a mechanism of the NP-1 slimming effect. The anti-obesity action of chronic NP-1 administration might be mediated by TNFα, which is known to have anorectic actions in the hypothalamus and to regulate both Dmnt1 and Ucp1 expression in adipose tissues. This finding opens up the possibility of using NP-1-mediated TNFα-induced weight loss as an innovative treatment of complicated obesity under strict pharmacologic control.

The Involvement of PPARs in the Peculiar Energetic Metabolism of Tumor Cells

Energy homeostasis is crucial for cell fate, since all cellular activities are strongly dependent on the balance between catabolic and anabolic pathways. In particular, the modulation of metabolic and energetic pathways in cancer cells has been discussed in some reports, but subsequently has been neglected for a long time. Meanwhile, over the past 20 years, a recovery of the study regarding cancer metabolism has led to an increasing consideration of metabolic alterations in tumors. Cancer cells must adapt their metabolism to meet their energetic and biosynthetic demands, which are associated with the rapid growth of the primary tumor and colonization of distinct metastatic sites. Cancer cells are largely dependent on aerobic glycolysis for their energy production, but are also associated with increased fatty acid synthesis and increased rates of glutamine consumption. In fact, emerging evidence has shown that therapeutic resistance to cancer treatment may arise from the deregulation of glucose metabolism, fatty acid synthesis, and glutamine consumption. Cancer cells exhibit a series of metabolic alterations induced by mutations that lead to a gain-of-function of oncogenes, and a loss-of-function of tumor suppressor genes, including increased glucose consumption, reduced mitochondrial respiration, an increase of reactive oxygen species, and cell death resistance; all of these are responsible for cancer progression. Cholesterol metabolism is also altered in cancer cells and supports uncontrolled cell growth. In this context, we discuss the roles of peroxisome proliferator-activated receptors (PPARs), which are master regulators of cellular energetic metabolism in the deregulation of the energetic homeostasis, which is observed in cancer. We highlight the different roles of PPAR isotypes and the differential control of their transcription in various cancer cells.

A Snake Venom-Secreted Phospholipase A2 Induces Foam Cell Formation Depending on the Activation of Factors Involved in Lipid Homeostasis

MT-III, a snake venom GIIA sPLA₂, which shares structural and functional features with mammalian GIIA sPLA₂s, activates macrophage defense functions including lipid droplet (LDs) formation, organelle involved in both lipid metabolism and inflammatory processes. Macrophages (MΦs) loaded with LDs, termed foam cells, characterize early blood vessel fatty-streak lesions during atherosclerosis. However, the factors involved in foam cell formation induced by a GIIA sPLA₂ are still unknown. Here, we investigated the participation of lipid homeostasis-related factors in LD formation induced by MT-III in macrophages. We found that MT-III activated PPAR-γ and PPAR-β/δ and increased the protein levels of both transcription factors and CD36 in macrophages. Pharmacological interventions evidenced that PPAR-γ, PPAR-β/δ, and CD36 as well as the endoplasmic reticulum enzymes ACAT and DGAT are essential for LD formation. Moreover, PPAR-β/δ, but not PPAR-γ, is involved in MT-III-induced PLIN2 protein expression, and both PPAR-β/δ and PPAR-γ upregulated CD36 protein expression, which contributes to MT-III-induced COX-2 expression. Furthermore, production of 15-d-PGJ₂, an activator of PPARs, induced by MT-III, was dependent on COX-1 being LDs an important platform for generation of this mediator.

PPARs and pain

Chronic pain is a common cause of disability worldwide and remains a global health and socio-economic challenge. Current analgesics are either ineffective in a significant proportion of patients with chronic pain or associated with significant adverse side effects. The PPARs, a family of nuclear hormone transcription factors, have emerged as important modulators of pain in preclinical studies and therefore a potential therapeutic target for the treatment of pain. Modulation of nociceptive processing by PPARs is likely to involve both transcription-dependent and transcription-independent mechanisms. This review presents a comprehensive overview of preclinical studies investigating the contribution of PPAR signalling to nociceptive processing in animal models of inflammatory and neuropathic pain. We examine current evidence from anatomical, molecular and pharmacological studies demonstrating a role for PPARs in pain control. We also discuss the limited evidence available from relevant clinical studies and identify areas that warrant further research. LINKED ARTICLES: This article is part of a themed section on 8^th European Workshop on Cannabinoid Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.10/issuetoc.

Exposure to 2,4-dichlorophenoxyacetic acid induced PPARβ-dependent disruption of glucose metabolism in HepG2 cells

2,4-Dichlorophenoxyacetic acid is one of the most widely used herbicides. Its impact on health is increasingly attracting great attentions. This study aimed to investigate the effect of 2,4-dichlorophenoxyacetic acid on glucose metabolism in HepG2 cells and the underlying mechanism. After 24 h exposure to 2,4-dichlorophenoxyacetic acid, glycogen was measured by PAS staining and glucose by ELISA in HepG2 cells. The expression of genes involved in glucose metabolism was measured by real-time PCR, Western blotting, and immunofluorescence. HepG2 cells presented more extracellular glucose consumption and glycogen content after exposed to 2,4-dichlorophenoxyacetic acid. Expression of gluconeogenesis-related genes, FoxO1, and CREB is significantly elevated. Moreover, PPARβ was up-regulated dose-dependently. SiRNA knockdown of PPARβ completely rescued the increase of glycogen accumulation and glucose uptake, and the up-regulation of FOXO1 and CREB expression. Our findings propose novel mechanisms that 2,4-dichlorophenoxyacetic acid causes glucose metabolism dysfunction through PPARβ in HepG2 cells.

The Circadian Clock in White and Brown Adipose Tissue: Mechanistic, Endocrine, and Clinical Aspects

Obesity is a major risk factor for the development of illnesses, such as insulin resistance and hypertension, and has become a serious public health problem. Mammals have developed a circadian clock located in the hypothalamic suprachiasmatic nuclei (SCN) that responds to the environmental light-dark cycle. Clocks similar to the one located in the SCN are found in peripheral tissues, such as the kidney, liver, and adipose tissue. The circadian clock regulates metabolism and energy homeostasis in peripheral tissues by mediating activity and/or expression of key metabolic enzymes and transport systems. Knockouts or mutations in clock genes that lead to disruption of cellular rhythmicity have provided evidence to the tight link between the circadian clock and metabolism. In addition, key proteins play a dual role in regulating the core clock mechanism, as well as adipose tissue metabolism, and link circadian rhythms with lipogenesis and lipolysis. Adipose tissues are distinguished as white, brown, and beige (or brite), each with unique metabolic characteristics. Recently, the role of the circadian clock in regulating the differentiation into the different adipose tissues has been investigated. In this review, the role of clock proteins and the downstream signaling pathways in white, brown, and brite adipose tissue function and differentiation will be reviewed. In addition, chronodisruption and metabolic disorders and clinical aspects of circadian adiposity will be addressed.

Bioactivity-Guided Isolation of Potential Antidiabetic and Antihyperlipidemic Compounds from Trigonella stellata

The in vitro antidiabetic and antihyperlipidemic activities of an alcoholic extract of Trigonella stellata were evaluated in terms of the activation of PPAR_α and PPAR_γ in human hepatoma (HepG2) cells. The extract was investigated phytochemically, aiming at the isolation of the most active compounds to be used as a platform for drug discovery. Three new isoflavans, (3 S,4 R)-4,2',4'-trihydroxy)-7-methoxyisoflavan (1), (3 R,4 S)-4,2',4'-trihydroxy-7-methoxy-4'- O-β-d-glucopyranosylisoflavan (2), and (2 S,3 R,4 R)-4,2',4'-trihydroxy-2,7-dimethoxyisoflavan (3), were isolated and characterized along with the five known compounds p-hydroxybenzoic acid (4), 7,4'-dihydroxyflavone (5), dihydromelilotoside (6), quercetin-3,7- O-α-l-dirhamnoside (7), and soyasaponin I (8). The structures of 1-3 were elucidated using various spectroscopic techniques including HRESIMS and 1D and 2D NMR. The absolute stereochemistry of the new isoflavans (1-3) was determined using both experimental and calculated electronic circular dichroism as well as DP4 calculations. The isolated compounds were tested for their PPAR_α and PPAR_γ activation effects in HepG2 cells.

Delayed activation of PPAR-β/δ improves long-term survival in mouse sepsis: effects on organ inflammation and coagulation

Activation of peroxisome proliferator-activated receptor (PPAR)-β/δ reduces tissue injury in murine endotoxemia. We hypothesized that the PPAR-β/δ-agonist GW0742 improves long-term outcome after sepsis caused by cecal ligation and puncture (CLP). Fifty-one CD-1 female mice underwent CLP and received either vehicle (control), GW0742 (0.03 mg/kg/injection; five post-CLP i.v. injections), GSK0660 (PPAR-β/δ-antagonist) or both and were monitored for 28 d. Another 20 CLP mice treated with GW0742 and vehicle were sacrificed 24 h post-CLP to assess coagulopathy. Compared to vehicle, survival of CLP-mice treated with GW0742 was higher by 35% at d 7 and by 50% at d 28. CLP mice treated with GW0742 had 60% higher IFN-γ but circulating monocyte chemoattractant protein-1 and chemokine ligand were lower at 48 h post-CLP. Compared to vehicle, CLP mice treated with GW0742 exhibited a 50% reduction in the circulating plasminogen activator inhibitor-1 associated with an increase in platelet number at 24 h post-CLP (but no changes occurred in anti-thrombin-III, plasminogen, fibrinogen and clotting-times). CLP mice treated with GW0742 exhibited a similar increase in most of the biochemical markers of organ injury/dysfunction (lactate dehydrogenase, alanine aminotransferase, creatine kinase, creatinine, blood urea nitrogen, and triglycerides) measured. Treatment with GW0742 consistently improved long-term survival in septic CD-1 mice by partially modulating the post-CLP systemic cytokine response and coagulation systems.

Effects of a novel selective peroxisome proliferator-activated receptor-α modulator, pemafibrate, on hepatic and peripheral glucose uptake in patients with hypertriglyceridemia and insulin resistance

AIMS/INTRODUCTION

Pemafibrate is a novel selective peroxisome proliferator-activated receptor-α modulator with potent triglyceride-lowering and high-density lipoprotein cholesterol-raising effects. We showed that pemafibrate decreased the homeostatic model assessment for insulin resistance in patients with dyslipidemia. To investigate how pemafibrate improves insulin sensitivity, we used a hyperinsulinemic-euglycemic clamp technique to determine the splanchnic and peripheral glucose uptake in patients with hypertriglyceridemia and insulin resistance.

MATERIALS AND METHODS

A total of 27 patients with hypertriglyceridemia and insulin resistance were randomly assigned to receive pemafibrate (0.4 mg/day, b.i.d.) or placebo treatment for 12 weeks. The hyperinsulinemic-euglycemic clamp test combined with oral glucose loading was carried out at weeks 0 and 12 to evaluate the splanchnic and peripheral glucose uptake.

RESULTS

Pemafibrate, but not the placebo, significantly increased the splanchnic glucose uptake rate from baseline (19.6 ± 5.9% with P = 0.005 and 2.1 ± 7.4% with P = 0.78, respectively), although no significant difference between the groups was observed (P = 0.084). Conversely, peripheral glucose uptake rate was not significantly altered. Pemafibrate, compared with the placebo, significantly decreased plasma triglycerides (-61.4 ± 16.4% vs -2.5 ± 41.4%, P = 0.001), free fatty acids (-24.8 ± 23.2% vs 2.0 ± 26.8%, P = 0.016) and gamma-glutamyl transpeptidase (-30 ± 46 vs 10 ± 19 U/L, P = 0.009) levels, and significantly increased fibroblast growth factor 21 (457.7 ± 402.1 vs -41.7 ± 37.4 pg/mL, P = 0.007) levels.

CONCLUSIONS

Pemafibrate increased splanchnic glucose uptake from baseline in patients with hypertriglyceridemia.

Assessment of the Pro12Ala Polymorphism in the PPAR-γ2 Gene among Type 2 Diabetes Patients in a Nigerian Population

The association between the Pro12Ala polymorphism of the PPARγ2 gene, type 2 diabetes (T2D), and obesity in certain ethnic populations has been reported. However, this relationship has not yet been described among diabetes patients in Nigeria. This study investigated the relationship between the Pro12Ala polymorphism in the PPARγ2 gene, obesity, and lipid abnormalities characterizing T2D among patients in Nigeria. This case-control study recruited 73 T2D and 75 non-diabetic (ND) patients. Demographic and clinical data were collected and blood glucose levels together with serum lipid profile for patients were measured. Pro12Ala polymorphism in the PPARγ2 gene was genotyped by restriction fragment length-Polymerase Chain Reaction (RFLP-PCR). The PPAR-γ2 gene (amplicon size = 270 base pair) was successfully amplified for all samples. Following restriction enzyme digestion and analysis by agarose gel electrophoresis, amplicons from samples showed a band of size 270 bp and were of the wild homozygous Pro/Pro genotype. Ala12 variant was totally absent from the study population. Obesity, estimated using Body Mass Index (BMI) and waist circumference (WC), was significantly higher (p < 0.05) in T2D patients compared to the non-diabetic patients. More so, the prevalence of lipid abnormalities; hypercholesterolaemia (TC > 200 mg/dL), hypertriglyceridaemia (TG > 150 mg/dL), high HDL (>100 mg/dL), and low HDL (<50 mg/dL) was significantly greater (p < 0.001) in T2D patients compared to non-diabetic patients. Results obtained further indicated lack of significant association between PPAR-γ2 gene polymorphism, T2D, and obesity. However, obesity and dyslipidaemia were strongly associated in T2D patients.

Pharmacogenomics of Chemically Distinct Classes of Keap1-Nrf2 Activators Identify Common and Unique Gene, Protein, and Pathway Responses In Vivo

The Kelch-like erythroid-associated protein 1 (Keap1)-NF-E2-related factor 2 (Nrf2) signaling pathway is the subject of several clinical trials evaluating the effects of Nrf2 activation on the prevention of cancer and diabetes and the treatment of chronic kidney disease and multiple sclerosis. 3H-1,2-dithiole-3-thione (D3T) and 1-[2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oyl]imidazole (CDDO-Im) are representative members of two distinct series of Nrf2 chemical activators. Previous reports have described activator-specific effects on Nrf2-dependent gene regulation and physiologic outcomes. Here we used a robust chemical genomics approach to characterize expression profiles between D3T and CDDO-Im in livers from wild-type and Nrf2-null mice. At equally efficacious doses in wild-type mice, 406 genes show common RNA responses to both treatments. These genes enriched the Nrf2-regulated pathways of antioxidant defense and xenobiotic metabolism. In addition, 197 and 745 genes were regulated uniquely in response to either D3T or CDDO-Im, respectively. Functional analysis of the D3T-regulated set showed a significant enrichment of Nrf2-regulated enzymes involved in cholesterol biosynthesis. This result was supported by Nrf2-dependent increases in lanosterol synthase and CYP51 protein expression. CDDO-Im had no effect on cholesterol biosynthesis regardless of the dose tested. However, unlike D3T, CDDO-Im resulted in Nrf2-dependent elevation of peroxisome proliferator α and Kruppel-like factor 13, as well as the coactivator peroxisome proliferator γ coactivator 1β, together indicating regulation of β-oxidation and lipid metabolic pathways. These findings provide novel insights into the pharmacodynamic action of these two activators of Keap1-Nrf2 signaling. Although both compounds modify Keap1 to affect canonical cytoprotective gene expression, additional unique sets of Nrf2-dependent genes were regulated by each agent with enrichment of selective metabolic pathways.

Polymorphisms in the Egl nine homolog 3 (EGLN3) and Peroxisome proliferator activated receptor-alpha (PPARα) genes and their correlation with hypoxia adaptation in Tibetan chickens

Peroxisome proliferator activated receptor-alpha (PPARα) and Egl nine homolog 3 (EGLN3) play critical roles in facilitating the adaptation to a hypoxic environment. However, the relationship between EGLN3 and PPARα variants and hypoxic adaptation remains poorly understood in Tibetan chickens. To better understand the effects of genetic variation, we sequenced exons of PPARα and EGLN3 in 138 Lowland chickens (LC) from 7 breeds that were located in Emei, Miyi, Shimian, Wanyuan, Pengxian, and Muchuan in the Sichuan province, and Wenchang in the Hainan province (altitudes for these locations are below 1800 meters). Total 166 Tibetan chickens (TC) from 7 subpopulations that were located in Shigatse, Lhoka, Lhasa, Garze, Aba, Diqing and Yushu in the Tibetan area were also sequenced (altitudes greater than 2700 meters). One single-nucleotide polymorphism (rs316017491, C > T) was identified in EGLN3 and was shared by TC and LC with no significant difference for allele frequencies between them (P > 0.05). Six single-nucleotide polymorphisms (SNP1, A29410G; SNP2, rs13886097; SNP3, T29467C; SNP4, rs735915170; SNP5, rs736599044; and SNP6, rs740077421) including one non-synonymous mutation (SNP2, T > C) were identified in PPARα. This is the first report of SNP1 and SNP3. There was a difference between TC and LC for allele frequencies (P <0.01), except for SNP1, SNP4, and SNP5) The fix index statistic test indicated that there was population differentiation between TC and LC for SNP2, SNP3, and SNP6 in PPARα (P < 0.05). Phylogenetic analysis showed that the genetic distance among chickens, finch and great tit were close for both EGLN3 and PPARα. Bioinformatics analysis of PPARα showed that SNP2 leads to an amino acid substitution of Ile for Met, which results in the protein being more likely to be hydrolyzed. Thus, genetic variation in PPARα may play a role in the ability of TC to adapt to a high altitude environment; however we were unable to identify a relationship between polymorphisms in EGLN3 and environmental adaptability.

Ligand-activated PPARγ downregulates CXCR4 gene expression through a novel identified PPAR response element and inhibits breast cancer progression

Stromal Derived Factor-1α (SDF-1α) and its cognate receptor CXCR4 play a key role in mediating breast cancer cell invasion and metastasis. Therefore, drugs able to inhibit CXCR4 activation may add critical tools to reduce tumor progression, especially in the most aggressive form of the breast cancer disease. Peroxisome Proliferator-Activated Receptor (PPAR) γ, a member of the nuclear receptor superfamily, has been found to downregulate CXCR4 gene expression in different cancer cells, however the molecular mechanism underlying this effect is not fully understood. Here, we identified a novel PPARγ-mediated mechanism that negatively regulates CXCR4 expression in both epithelial and stromal breast cancer cells. We found that ligand-activated PPARγ downregulated CXCR4 transcriptional activity through the recruitment of the silencing mediator of retinoid and thyroid hormone receptor (SMRT) corepressor onto a newly identified PPAR response element (PPRE) within the CXCR4 promoter in breast cancer cell lines. As a consequence, the PPARγ agonist rosiglitazone (BRL) significantly inhibited cell migration and invasion and this effect was PPARγ-mediated, since it was reversed in the presence of the PPARγ antagonist GW9662. According to the ability of cancer-associated fibroblasts (CAFs), the most abundant component of breast cancer stroma, to secrete high levels of SDF-1α, BRL reduced migratory promoting activities induced by conditioned media (CM) derived from CAFs and affected CXCR4 downstream signaling pathways activated by CAF-CM. In addition, CAFs exposed to BRL showed a decreased expression of CXCR4, a reduced motility and invasion along with a phenotype characterized by an altered morphology. Collectively, our findings provide novel insights into the role of PPARγ in inhibiting breast cancer progression and further highlight the utility of PPARγ ligands for future therapies aimed at targeting both cancer and surrounding stromal cells in breast cancer patients.

Wide-range screening of anti-inflammatory compounds in tomato using LC-MS and elucidating the mechanism of their functions

Obesity-induced chronic inflammation is a key factor in type 2 diabetes. A vicious cycle involving pro-inflammatory mediators between adipocytes and macrophages is a common cause of chronic inflammation in the adipose tissue. Tomato is one of the most popular vegetables and is associated with a reduced risk of diabetes. However, the molecular mechanism underlying the effect of tomato on diabetes is unclear. In this study, we focused on anti-inflammatory compounds in tomato. We found that the extract of tomato reduced plasma glucose and inflammatory markers in mice. We screened anti-inflammatory fractions in tomato using lipopolysaccharide-stimulated RAW264.7 macrophages, and active compounds were estimated by liquid chromatography-mass spectrometry over a wide range. Surprisingly, a large number of compounds including oxylipin and coumarin derivatives were estimated as anti-inflammatory compounds. Especially, 9-oxo-octadecadienoic acid and daphnetin suppressed pro-inflammatory cytokines in RAW264.7 macrophages inhibiting mitogen-activated protein kinase phosphorylation and inhibitor of kappa B α protein degradation. These findings suggest that tomato containing diverse anti-inflammatory compounds ameliorates chronic inflammation in obese adipose tissue.

4',6-Dimethoxyisoflavone-7-O-β-D-glucopyranoside (wistin) is a peroxisome proliferator-activated receptor α (PPARα) agonist in mouse hepatocytes

Peroxisome proliferator-activated receptors (PPARs) are ligand-dependent transcription factors that regulate lipid and glucose metabolism. PPARα mainly affects fatty acid metabolism, and its activation lowers lipid levels. PPARγ is involved in the regulation of adipogenesis, insulin sensitivity, energy balance, and lipid biosynthesis. We have previously reported that 4',6-dimethoxyisoflavone-7-O-β-D-glucopyranoside (wistin) can activate PPARγ. The purpose of the present study is to investigate the PPARα agonist activity of wistin. Using a luciferase reporter assay system of PPARα in monkey COS7 kidney cells, we showed that wistin could activate PPARα (P < 0.01 at 10 μg/mL) in a dose-dependent manner. Moreover, the addition of wistin upregulated the expression of PPARα (P < 0.01 at 10 μg/mL) and PPARα target genes including carnitine palmitoyltransferase 1a (P < 0.05 at 10 μg/mL), acyl-CoA oxidase (P < 0.01 at 10 μg/mL), acyl-CoA synthase (P < 0.05 at 10 μg/mL), PPARγ coactivator 1α (P < 0.05 at 10 μg/mL), uncoupling protein 2 (P < 0.05 at 1 μg/mL), and uncoupling protein 3 (P < 0.05 at 10 μg/mL), which are genes involved in lipid efflux and energy expenditure, in mouse primary hepatocytes. Furthermore, wistin inhibited cellular triglyceride accumulation in hepatocytes (P < 0.05 at 10 μg/mL) in a dose-dependent manner. These results indicate that wistin could suppress lipid accumulation through PPARα activation. The action of wistin on PPARα could be of interest for the amelioration of lipid metabolic disorders. To the best of our knowledge, wistin is the first reported isoflavonoid O-glycoside with PPARα agonist activity.

DHA induces apoptosis of human malignant breast cancer tissues by the TLR-4/PPAR-α pathways

Docosahexaenoic acid (DHA) oil is an important polyunsaturated fatty acid for the human body. Evidence has demonstrated that DHA is beneficial for inhibiting mammary carcinogenesis. However, the mechanisms of DHA mediating apoptosis induction have not been fully elucidated. Thus, in the present study, the activity levels of total-superoxide dismutase (t-SOD), catalase (CAT), glutathione-peroxidase (GSH-PX) and the concentration of malondialdehyde (MDA) were determined in DHA oil-treated human malignant breast tissues. The results revealed that compared with control, DHA significantly increased the main antioxidant enzymes levels, including t-SOD, CAT, and GSH-PX, but decreased the MDA concentration in the DHA oil treated breast cancer tissues. Furthermore, DHA significantly increased the ratio of cyclic (c)AMP/cGMP levels and promoted the expression of Toll-like receptor 4 (TLR-4) and peroxisome proliferator activated receptor (PPAR)-α, thus DHA induced breast cancer cell apoptosis. We hypothesized that the levels of TLR-4 and PPAR-α are involved in the antitumorigenesis properties of DHA in breast cancer. The results of the present study hold significance for the further clinical development of DHA oil in breast cancer treatment.

Oleate activates SREBP-1 signaling activity in SCD1-deficient hepatocytes

Stearoyl-CoA desaturase-1 (SCD1) is a key player in lipid metabolism. SCD1 catalyzes the synthesis of monounsaturated fatty acids (MUFA). MUFA are then incorporated into triacylglycerols and phospholipids. Previous studies have shown that Scd1 deficiency in mice induces metabolic changes in the liver characterized by a decrease in de novo lipogenesis and an increase in β-oxidation. Interestingly, Scd1-deficient mice show a decrease in the expression and maturation of the principal lipogenic transcription factor sterol receptor element binding protein-1 (SREBP-1). The mechanisms mediating this effect on de novo lipogenesis and β-oxidation have not been fully elucidated. We evaluated the role of SCD1 on de novo lipogenesis and β-oxidation in HepG2 cells. We also used Scd1-deficient mice and two strains of transgenic mice that produce either oleate (GLS5) or palmitoleate (GLS3) in a liver-specific manner. We demonstrate that the expression of β-oxidation markers increases in SCD1-deficient hepatocytes and suggest that this is due to an increase in cellular polyunsaturated fatty acid content. We also show that the changes in the level of SREBP-1 expression, for both the precursor and the mature forms, are mainly due to the lack of oleate in SCD1-deficient hepatocytes. Indeed, oleate treatment of cultured HepG2 cells or hepatic oleate production in chow-fed GLS5 mice can restore SREBP-1 expression and increase hepatic de novo lipogenesis. Finally, we show that oleate specifically increases SREBP-1 nuclear accumulation, suggesting a central role for oleate in SREBP-1 signaling activity.

A transcriptomic study of myogenic differentiation under the overexpression of PPARγ by RNA-Seq

To study the cellular and molecular function of peroxisome proliferator-activated receptor γ (PPARγ) in skeletal muscle differentiation, we have generated inducible gain-of-function to overexpress PPARγ in C2C12 myoblasts. In order to identify PPARγ targets, RNA sequencing (RNA-seq) was used to evaluate and quantify the transcriptomes and expression patterns during myogenic differentiation under the overexpression of PPARγ. The formation of myotubes and the expression of muscle-specific myogenic genes such as MyoD and MyoG may be inhibited by PPARγ overexpression. Multiple genes and pathways were significantly involved in this process, including 11 genes such as Fndc9 and Slc14a1 with fundamental change of regulation modes, 9 genes of which were validated by the data of qRT-PCR. Our studies demonstrate that PPARγ would play critical roles on myoblasts differentiation, mediating crosstalk among several pathways and transcription factors. Our data is available in the Gene Expression Omnibus (GEO) database with the accession number as GSE99399.

5-Ene-4-thiazolidinones - An efficient tool in medicinal chemistry

The presented review is an attempt to summarize a huge volume of data on 5-ene-4-thiazolidinones being a widely studied class of small molecules used in modern organic and medicinal chemistry. The manuscript covers approaches to the synthesis of 5-ene-4-thiazolidinone derivatives: modification of the C5 position of the basic core; synthesis of the target compounds in the one-pot or multistage reactions or transformation of other related heterocycles. The most prominent pharmacological profiles of 5-ene derivatives of different 4-thiazolidinone subtypes belonging to hit-, lead-compounds, drug-candidates and drugs as well as the most studied targets have been discussed. Currently target compounds (especially 5-en-rhodanines) are assigned as frequent hitters or pan-assay interference compounds (PAINS) within high-throughput screening campaigns. Nevertheless, the crucial impact of the presence/nature of C5 substituent (namely 5-ene) on the pharmacological effects of 5-ene-4-thiazolidinones was confirmed by the numerous listed findings from the original articles. The main directions for active 5-ene-4-thiazolidinones optimization have been shown: i) complication of the fragment in the C5 position; ii) introduction of the substituents in the N3 position (especially fragments with carboxylic group or its derivatives); iii) annealing in complex heterocyclic systems; iv) combination with other pharmacologically attractive fragments within hybrid pharmacophore approach. Moreover, the utilization of 5-ene-4-thiazolidinones in the synthesis of complex compounds with potent pharmacological application is described. The chemical transformations cover mainly the reactions which involve the exocyclic double bond in C5 position of the main core and correspond to the abovementioned direction of the 5-ene-4-thiazolidinone modification.

Solanum nigrum Polyphenol Extracts Inhibit Hepatic Inflammation, Oxidative Stress, and Lipogenesis in High-Fat-Diet-Treated Mice

Patients with diabetes, obesity, and hyperlipidemia are all high-risk groups for fatty liver; however, the mechanism of fatty liver formation is not completely understood. Studies have indicated that abnormal fat metabolism, oxidative stress, and insulin resistance are positively correlated with peroxidation and abnormal cytokine production. Recent studies have revealed that Solanum nigrum extracts (SNE) possess anti-inflammatory, antioxidation, antihyperlipidemia, and liver protection abilities. Therefore, the present study investigated the in vivo and in vitro effects of an SNE on nonalcoholic fatty liver (NAFL)-induced hepatitis. In vivo data demonstrated that the SNE reduced blood triglyceride, sugar, and cholesterol levels, as well as fat accumulation, oxidative stress, and lipid peroxidation in high-fat-diet-treated mice. The results indicated that the SNE downregulated the expression of fatty acid synthase, 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase), and sterol regulatory element-binding proteins (SREBPs) through the AMP-activated protein kinase (AMPK) pathway and upregulated the expression of carnitine palmitoyltransferase 1 (CPT1) and peroxisome proliferator-activated receptor alpha. Furthermore, we prepared a Solanum nigrum polyphenol extract (SNPE) from the SNE; the SNPE reduced hepatic lipid (oleic acid) accumulation. Therefore, SNE have the potential to alleviate NAFL-induced hepatitis, and polyphenolic compounds are the main components of SNE. Moreover, SNE can be used to develop health-food products for preventing NAFL disease.

Peroxisome proliferator activating receptor-γ and the podocyte

Over the past two decades it has become clear that the glomerular podocyte is a key cell in preventing albuminuria, kidney failure and cardiovascular morbidity. Understanding the key pathways that protect the podocyte in times of glomerular stress, which can also be therapeutically manipulated, are highly attractive. In the following review we assess the evidence that the peroxisome proliferator activating receptor (PPAR) agonists are beneficial for podocyte and kidney function with a focus on PPAR-γ. We explain our current understanding of the mechanisms of action of these agonists and the evidence they are beneficial in diabetic and non-diabetic kidney disease. We also outline why these drugs have not been widely used for kidney disease in the past but they may be in the future.

Anti-hypertensive and cardioprotective effects of a novel apitherapy formulation via upregulation of peroxisome proliferator-activated receptor-α and -γ in spontaneous hypertensive rats

Ventricular remodeling is associated with many heart diseases, and ventricular remodeling induced by hypertension can be fatal independent of hypertension. In this study, we prepared a novel apitherapy formulation, designated Bao-Yuan-Ling (BYL), which contained propolis, royal jelly, and bee venom, to treat spontaneous hypertensive rats (SHRs). We then evaluated the pharmacology of BYL and the potential mechanisms through which BYL affects hypertension and ventricular remodeling. We found that BYL treatment could reduce blood pressure in SHRs. Thereafter, we found that BYL treatment reduced serum levels of angiotensin II, endothelin 1, and transforming growth factor-β and improved the myocardial structure. Moreover, the results of quantitative real-time polymerase chain reaction indicated that BYL treatment could upregulate the mRNA expression of peroxisome proliferator-activated receptor (PPAR)-α and PPAR-γ. Thus, we could conclude that BYL had hypotensive and cardioprotective effects in SHRs, potentially through improvement of myocardial energy metabolism.

ADAMTS1-mediated targeting of TSP-1 by PPARδ suppresses migration and invasion of breast cancer cells

Migration and invasion of cancer cells into surrounding tissue is a key stage of cancer metastasis. Here, we show that peroxisome proliferator-activated receptor (PPAR) δ regulates migration and invasion of human breast cancer cells via thrombospondin-1 (TSP-1) and its degrading protease, a disintegrin and metalloprotease domains with thrombospondin motifs 1 (ADAMTS1). Activation of PPARδ by GW501516, a specific ligand for PPARδ, led to marked inhibition in the cell migration and TSP-1 expression of breast cancer. These effects were suppressed by small interfering RNA-mediated knock-down of ADAMTS1, indicating that ADAMTS1 is involved in PPARδ-mediated inhibition of migration and TSP-1 expression in breast cancer cells. In addition, ligand-activated PPARδ upregulated expression of ADAMTS1 at the transcriptional level via binding of PPARδ to a direct repeat-1 site within the ADAMTS1 gene promoter. Furthermore, ligand-activated PPARδ suppressed invasion of breast cancer cells in an ADAMTS1-dependent manner. Taken together, these results demonstrate that PPARδ suppresses migration and invasion of breast cancer cells by downregulating TSP-1 in a process mediated by upregulation of ADAMTS1.

PPAR-α Modulates the Anti-Inflammatory Effect of Melatonin in the Secondary Events of Spinal Cord Injury

Melatonin is the principal secretory product of the pineal gland, and its role as an immunomodulator is well established. Recent evidence shows that melatonin is a scavenger of oxyradicals and peroxynitrite and reduces the development of inflammation and tissue injury events associated with spinal cord trauma. Previous results suggest that peroxisome proliferator-activated receptor α (PPAR-α), a nuclear receptor protein that functions as a transcription factor activated by fatty acids, plays a role in control of secondary inflammatory process associated with spinal cord injury (SCI).With the aim to characterize the role of PPAR-α in melatonin-mediated anti-inflammatory activity, we tested the efficacy of melatonin (30 mg/kg) in an experimental model of spinal cord trauma, induced in mice, by the application of vascular clips (force of 24 g) to the dura via a four-level T5-T8 laminectomy, and comparing mice lacking PPAR-α (PPAR-α KO) with wild-type (WT) mice.The results obtained indicate that melatonin-mediated anti-inflammatory activity is weakened in PPAR-α KO mice, as compared to WT controls. In particular, melatonin was less effective in PPAR-α KO, compared to WT mice, as evaluated by inhibition of the degree of spinal cord inflammation and tissue injury, neutrophil infiltration, pro-inflammatory cytokine expression, nuclear factor κB (NF-κB) activation, and inducible nitric oxide synthase (iNOS) expression. This study indicates that PPAR-α can contribute to the anti-inflammatory activity of melatonin in SCI.

The Roles of SUMO in Metabolic Regulation

Protein modification with the small ubiquitin-related modifier (SUMO) can affect protein function, enzyme activity, protein-protein interactions, protein stability, protein targeting and cellular localization. SUMO influences the function and regulation of metabolic enzymes within pathways, and in some cases targets entire metabolic pathways by affecting the activity of transcription factors or by facilitating the translocation of entire metabolic pathways to subcellular compartments. SUMO modification is also a key component of nutrient- and metabolic-sensing mechanisms that regulate cellular metabolism. In addition to its established roles in maintaining metabolic homeostasis, there is increasing evidence that SUMO is a key factor in facilitating cellular stress responses through the regulation and/or adaptation of the most fundamental metabolic processes, including energy and nucleotide metabolism. This review focuses on the role of SUMO in cellular metabolism and metabolic disease.

Nuclear Receptor PPARα Agonist Wy-14,643 Ameliorates Hepatic Cell Death in Hepatic IKKβ-Deficient Mice

Inhibitor of nuclear factor kappa-B kinase beta (IKKβ) plays a critical role in cell proliferation and inflammation in various cells by activating NF-κB signaling. However, the interrelationship between peroxisome proliferator-activated receptor α (PPARα) and IKKβ in cell proliferation is not clear. In this study, we investigated the possible role of PPARα in the hepatic cell death in the absence of IKKβ gene using liver-specific Ikkb-null (Ikkb^F/F-AlbCre) mice. To examine the function of PPARα activation in hepatic cell death, wild-type (Ikkb^F/F) and Ikkb^F/F-AlbCre mice were treated with PPARα agonist Wy-14,643 (0.1% w/w chow diet) for two weeks. As a result of Wy-14,643 treatment, apoptotic markers including caspase-3 cleavage, poly (ADP-ribose) polymerase (PARP) cleavage and TUNEL-positive staining were significantly decreased in the Ikkb^F/F-AlbCre mice. Surprisingly, Wy-14,643 increased the phosphorylation of p65 and STAT3 in both Ikkb and Ikkb^F/F-AlbCre mice. Furthermore, BrdU-positive cells were significantly increased in both groups after treatment with Wy-14,643. Our results suggested that IKKβ-derived hepatic apoptosis could be altered by PPARα activation in conjunction with activation of NF-κB and STAT3 signaling.

Collaborative Power of Nrf2 and PPARγ Activators against Metabolic and Drug-Induced Oxidative Injury

Mammalian cells have evolved a unique strategy to protect themselves against oxidative damage induced by reactive oxygen species (ROS). Especially, two transcription factors, nuclear factor erythroid 2p45-related factor 2 (Nrf2) and peroxisome proliferator-activated receptor γ (PPARγ), have been shown to play key roles in establishing this cellular antioxidative defense system. Recently, several researchers reported ameliorating effects of pharmacological activators for these Nrf2 and PPARγ pathways on the progression of various metabolic disorders and drug-induced organ injuries by oxidative stress. In this review, general features of Nrf2 and PPARγ pathways in the context of oxidative protection will be summarized first. Then, a number of successful applications of natural and synthetic Nrf2 and PPARγ activators to the alleviation of pathological and drug-related oxidative damage will be discussed later.

Pioglitazone Enhances Cytosolic Lipolysis, β-oxidation and Autophagy to Ameliorate Hepatic Steatosis

Non-alcoholic fatty liver disease closely contributes to the development of obesity and insulin resistance. Even though pioglitazone has been reported to effectively lessen hepatic steatosis in human studies, its molecular mechanism remains unclear. This study is designed to investigate the regulation of cytosolic lipolysis, β-oxidation and autophagy by pioglitazone in a mice model of high fat diet (HFD) and cell model incubated with palmitic acid. Our results revealed hepatic steatosis was apparently induced by HFD and it was significantly reversed by pioglitazone. The serum insulin and hepatic triglyceride content was significantly decreased by co-administered pioglitazone with HFD. Hepatic expression of cytosolic-lipolysis related proteins (ATGL, HSL), β-oxidation (CPT-1A) and autophagy-related proteins (ATG7, LC3, LAL) was significantly enhanced by pioglitazone. Knockdown PPARα/PPARγ in AML12 cells significantly and proportionally reduced the expressions of ATGL, CPT-1A and LC3II, which was induced by pioglitazone. Furthermore, facilitation of the autophagic flux by pioglitazone was obviously blocked by lysosomal inhibitor, leupeptin, to demonstrate accumulation of the LC3II and intracellular lipid in AML12 cells. Our results demonstrated that pioglitazone attenuating the hepatic steatosis may be mediated by enhancing cytosolic lipolysis, β-oxidation and autophagy in a PPARα and PPARγ dependent manner.

Fatty Acid Profile Is Modulated by Dietary Resveratrol in Rainbow Trout (Oncorhynchus mykiss)

To produce fish of a high quality that are rich in omega-3 fatty acids (n-3 FA) and simultaneously generate more sustainable aquaculture, the combined use of phytochemicals and vegetable oils in fish feed seems to be a promising approach. Resveratrol (RV) potentially induces endogenous fatty acid synthesis, resulting in elevated n-3 FA levels in fish. RV putatively influences ∆6-desaturase, the key enzyme in FA metabolism, and serves as a ligand for PPARα, a transcription factor regulating β-oxidation. Rainbow trout (36.35 ± 0.03 g) were randomly allocated into six groups and fed diets with reduced fish oil levels (F4 = 4%, F2 = 2% and F0 = 0% of dry matter) supplemented with 0.3% (w/w) RV (F4 + RV, F2 + RV and F0 + RV). RV significantly affected FA composition in liver tissue and whole fish homogenates. 20:5n-3 (EPA) and 22:6n-3 (DHA) were significantly increased whereas precursor FA were diminished in fish fed the F2 + RV and F0 + RV diets when compared to F4 + RV and F0. RV significantly elevated ∆6-desaturase protein levels in the livers of F0 + RV fed animals. Hepatic mRNA expression of ∆6-desaturase, PPARα, and its target genes were affected by the dietary fish oil level and not by dietary RV. The results of this study indicated a potential benefit of supplementing RV in fish oil deprived diets elevating n-3 FA levels in rainbow trout.

Anti-inflammatory Mechanisms Triggered by Apoptotic Cells during Their Clearance

In the human body, billions of cells die by apoptosis every day. The subsequent clearance of apoptotic cells by phagocytosis is normally efficient enough to prevent secondary necrosis and the consequent release of cell contents that would induce inflammation and trigger autoimmunity. In addition, apoptotic cells generally induce an anti-inflammatory response, thus removal of apoptotic cells is usually immunologically silent. Since the first discovery that uptake of apoptotic cells leads to transforming growth factor (TGF)-β and interleukin (IL)-10 release by engulfing macrophages, numerous anti-inflammatory mechanisms triggered by apoptotic cells have been discovered, including release of anti-inflammatory molecules from the apoptotic cells, triggering immediate anti-inflammatory signaling pathways by apoptotic cell surface molecules via phagocyte receptors, activating phagocyte nuclear receptors following uptake and inducing the production of anti-inflammatory soluble mediators by phagocytes that may act via paracrine or autocrine mechanisms to amplify and preserve the anti-inflammatory state. Here, we summarize our present knowledge about how these anti-inflammatory mechanisms operate during the clearance of apoptotic cells.

Changes to cholesterol trafficking in macrophages by Leishmania parasites infection

Leishmania spp. are protozoan parasites that are transmitted by sandfly vectors during blood sucking to vertebrate hosts and cause a spectrum of diseases called leishmaniases. It has been demonstrated that host cholesterol plays an important role during Leishmania infection. Nevertheless, little is known about the intracellular distribution of this lipid early after internalization of the parasite. Here, pulse-chase experiments with radiolabeled cholesteryl esterified to fatty acids bound to low-density lipoproteins indicated that retention of this source of cholesterol is increased in parasite-containing subcellular fractions, while uptake is unaffected. This is correlated with a reduction or absence of detectable NPC1 (Niemann-Pick disease, type C1), a protein responsible for cholesterol efflux from endocytic compartments, in the Leishmania mexicana habitat and infected cells. Filipin staining revealed a halo around parasites within parasitophorous vacuoles (PV) likely representing free cholesterol accumulation. Labeling of host cell membranous cholesterol by fluorescent cholesterol species before infection revealed that this pool is also trafficked to the PV but becomes incorporated into the parasites' membranes and seems not to contribute to the halo detected by filipin. This cholesterol sequestration happened early after infection and was functionally significant as it correlated with the upregulation of mRNA-encoding proteins required for cholesterol biosynthesis. Thus, sequestration of cholesterol by Leishmania amastigotes early after infection provides a basis to understand perturbation of cholesterol-dependent processes in macrophages that were shown previously by others to be necessary for their proper function in innate and adaptive immune responses.

Protection against alcohol-induced neuronal and cognitive damage by the PPARγ receptor agonist pioglitazone

Binge alcohol drinking has emerged as a typical phenomenon in young people. This pattern of drinking, repeatedly leading to extremely high blood and brain alcohol levels and intoxication is associated with severe risks of neurodegeneration and cognitive damage. Mechanisms involved in excitotoxicity and neuroinflammation are pivotal elements in alcohol-induced neurotoxicity. Evidence has demonstrated that PPARγ receptor activation shows anti-inflammatory and neuroprotective properties. Here we examine whether treatment with the PPARγ agonist pioglitazone is beneficial in counteracting neurodegeneration, neuroinflammation and cognitive damage produced by binge alcohol intoxication. Adult Wistar rats were subjected to a 4-day binge intoxication procedure, which is commonly used to model excessive alcohol consumption in humans. Across the 4-day period, pioglitazone (0, 30, 60mg/kg) was administered orally twice daily at 12-h intervals. Degenerative cells were detected by fluoro-jade B (FJ-B) immunostaining in brain regions where expression of pro-inflammatory cytokines was also determined. The effects of pioglitazone on cognitive function were assessed in an operant reversal learning task and the Morris water maze task. Binge alcohol exposure produced selective neuronal degeneration in the hippocampal dentate gyrus and the adjacent entorhinal cortex. Pioglitazone reduced FJ-B positive cells in both regions and prevented alcohol-induced expression of pro-inflammatory cytokines. Pioglitazone also rescued alcohol-impaired reversal learning in the operant task and spatial learning deficits in the Morris water maze. These findings demonstrate that activation of PPARγ protects against neuronal and cognitive degeneration elicited by binge alcohol exposure. The protective effect of PPARγ agonist appears to be linked to inhibition of pro-inflammatory cytokines.

Fish oil supplementation to rats fed high-fat diet during pregnancy prevents development of impaired insulin sensitivity in male adult offspring

We examined whether maternal fish oil supplementation during pregnancy could prevent development of insulin resistance in adult male offspring of rat dams fed a high-fat diet. Time-mated Sprague-Dawley rat dams were randomised into four treatment groups: Con-Con, dams fed a control diet (fat: 15% kcal) and administered water by gavage; Con-FO, control diet with unoxidised fish oil by gavage; HF-Con, high-fat diet (fat: 45% kcal) and water by gavage; and HF-FO, high-fat diet and unoxidised fish oil by gavage. Dams were fed the allocated diet ad libitum during pregnancy and lactation, but daily gavage occurred only during pregnancy. After weaning, male offspring consumed a chow diet ad libitum until adulthood. Maternal high-fat diet led to increased food consumption, adiposity, systolic blood pressure, and triglycerides and plasma leptin in adult HF-Con offspring. HF-Con offspring also exhibited lower insulin sensitivity than Con-Con rats. Male offspring from HF-FO group were similar to HF-Con regarding food consumption and most metabolic parameters. However, insulin sensitivity in the HF-FO group was improved relative to the HF-Con offspring. Supplementation with unoxidised n-3 PUFA rich oils in the setting of a maternal obesogenic diet improved insulin sensitivity, but had no impact on body composition of adult male offspring.

A Review of the Molecular Mechanisms Underlying the Development and Progression of Cardiac Remodeling

Pathological molecular mechanisms involved in myocardial remodeling contribute to alter the existing structure of the heart, leading to cardiac dysfunction. Among the complex signaling network that characterizes myocardial remodeling, the distinct processes are myocyte loss, cardiac hypertrophy, alteration of extracellular matrix homeostasis, fibrosis, defective autophagy, metabolic abnormalities, and mitochondrial dysfunction. Several pathophysiological stimuli, such as pressure and volume overload, trigger the remodeling cascade, a process that initially confers protection to the heart as a compensatory mechanism. Yet chronic inflammation after myocardial infarction also leads to cardiac remodeling that, when prolonged, leads to heart failure progression. Here, we review the molecular pathways involved in cardiac remodeling, with particular emphasis on those associated with myocardial infarction. A better understanding of cell signaling involved in cardiac remodeling may support the development of new therapeutic strategies towards the treatment of heart failure and reduction of cardiac complications. We will also discuss data derived from gene therapy approaches for modulating key mediators of cardiac remodeling.

Peroxisome Proliferator-Activated Receptor α Facilitates Osteogenic Differentiation in MC3T3-E1 Cells via the Sirtuin 1-Dependent Signaling Pathway

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease characterized by lack of insulin and high glucose levels. T2DM can cause bone loss and fracture, thus leading to diabetic osteoporosis. Promoting osteogenic differentiation of osteoblasts may effectively treat diabetic osteoporosis. We previously reported that Sirtuin 1 (Sirt1), a NAD+-dependent deacetylase, promotes osteogenic differentiation through downregulation of peroxisome proliferator-activated receptor (PPAR) γ. We also found that miR-132 regulates osteogenic differentiation by downregulating Sirt1 in a PPARβ/δ-dependent manner. The ligand-activated transcription factor, PPARα, is another isotype of the peroxisome proliferator-activated receptor family that helps maintain bone homeostasis and promot bone formation. Whether the regulatory role of PPARα in osteogenic differentiation is mediated via Sirt1 remains unclear. In the present study, we aimed to determine this role and the underlying mechanism by using high glucose (HG) and free fatty acids (FFA) to mimic T2DM in MC3T3-E1 cells. The results showed that HG-FFA significantly inhibited expression of PPARα, Sirt1 and osteogenic differentiation, but these effects were markedly reversed by PPARα overexpression. Moreover, siSirt1 attenuated the positive effects of PPARα on osteogenic differentiation, suggesting that PPARα promotes osteogenic differentiation in a Sirt1-dependent manner. Luciferase activity assay confirmed interactions between PPARα and Sirt1. These findings indicate that PPARα promotes osteogenic differentiation via the Sirt1-dependent signaling pathway.

Effects of Karela (Bitter Melon; Momordica charantia) on genes of lipids and carbohydrates metabolism in experimental hypercholesterolemia: biochemical, molecular and histopathological study

Background

Hypercholesterolemia is a serious diseases associated with type-2 diabetes, atherosclerosis, cardiovascular disorders and liver diseases. Humans seek for safe herbal medication such as karela (Momordica charantia/bitter melon) to treat such disorders to avoid side effect of pharmacotherapies widely used.

Methods

Forty male Wistar rats were divided into four equal groups; control group with free access to food and water, cholesterol administered group (40 mg/kg BW orally); karela administered group (5 g /kg BW orally) and mixture of cholesterol and karela. The treatments continued for 10 weeks. Karela was given for hypercholesterolemic rats after 6 weeks of cholesterol administration. Serum, liver and epididymal adipose tissues were taken for biochemical, histopathological and genetic assessments.

Results

Hypercholesterolemia induced a decrease in serum superoxide dismutase (SOD), catalase, reduced glutathione (GSH) and an increase in malondialdehyde (MDA) levels that were ameliorated by karela administration. Hypercholesterolemia up regulated antioxidants mRNA expression and altered the expression of carbohydrate metabolism genes. In parallel, hypercholesterolemic groups showed significant changes in the expression of PPAR-alpha and gamma, lipolysis, lipogenesis and cholesterol metabolism such as carnitine palmitoyltransferase-1 (CPT-1). Acyl CoA oxidase (ACO), fatty acids synthase (FAS), sterol responsible element binding protein-1c (SREBP1c), 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoAR) and cholesterol 7α-hydroxylase (CYP7A1) at hepatic and adipose tissue levels. Interestingly, Karela ameliorated all altered genes confirming its hypocholesterolemic effect. Histopathological and immunohistochemical findings revealed that hypercholesterolemia induced hepatic tissue changes compared with control. These changes include cholesterol clefts, necrosis, karyolysis and sever congestion of portal blood vessel. Caspase-3 immunoreactivity showed positive expression in hepatic cells of hypercholesterolemic rats compared to control. All were counteracted and normalized after Karela administration to hypercholesterolemic group.

Conclusion

Current findings confirmed that karela is a potential supplement useful in treatment of hypercholesterolemia and its associated disorders and is good for human health.

Peroxisome proliferator-activated receptor alpha mediates C/EBP homologous protein to protect mice from acute liver failure

OBJECTIVE

Peroxisome proliferator-activated receptor α (PPARα) activation has been reported to ameliorate liver injury in cases of acute liver failure (ALF). However, its intrinsic protective molecular mechanisms remain largely undetermined. C/EBP homologous protein (CHOP) is an important mediator of lipopolysaccharide (LPS)-induced inflammation. The aim of the present study was to test the hypothesis that PPARα activation alleviates liver inflammation to protect mice from acute liver failure (ALF) mediated by CHOP.

METHODS

In a murine model induced by D-galactosamine (D-GalN, 700 mg/kg) and LPS (10 μg/kg), Wy-14643 (6 mg/kg) was administered to activate PPARα. The mice of different groups were killed 6 h after D-GalN/LPS injection, and the liver and blood were collected for analysis. To find out whether PPARα activation protects the liver from injury due to inflammation by regulating CHOP, we used expression plasmid to increase CHOP expression and demonstrated how PPARα mediated CHOP to regulate inflammation in vivo and in vitro.

RESULTS

The expression of PPARα was downregulated and the expression of CHOP was upregulated with the development of D-GalN/LPS-induced liver injury. The protective molecular mechanisms of PPARα activation were dependent on the expression of CHOP. Indeed, (1) PPARα activation decreased the expression of CHOP; on the other hand, PPARα knockdown increased the expression of CHOP in vivo; (2) the depressed liver inflammation by PPARα activation was due to the downregulation of CHOP expression, because overexpression of CHOP by transfect plasmid reversed liver protection and increased liver inflammation again; (3) in vitro, PPARα inhibition by siRNA treatment increased the expression of proinflammatory cytokines, and CHOP siRNA co-transfection reversed the expression of proinflammatory cytokines.

CONCLUSIONS

Here, we demonstrated that PPARα activation contributes to liver protection and decreases liver inflammation in ALF, particularly through regulating CHOP. Our findings may provide a rationale for targeting PPARα as a potential therapeutic strategy to ameliorate ALF.

Thermodynamics in Gliomas: Interactions between the Canonical WNT/Beta-Catenin Pathway and PPAR Gamma

Gliomas cells are the site of numerous metabolic and thermodynamics abnormalities with an increasing entropy rate which is characteristic of irreversible processes driven by changes in Gibbs energy, heat production, intracellular acidity, membrane potential gradient, and ionic conductance. We focus our review on the opposing interactions observed in glioma between the canonical WNT/beta-catenin pathway and PPAR gamma and their metabolic and thermodynamic implications. In gliomas, WNT/beta-catenin pathway is upregulated while PPAR gamma is downregulated. Upregulation of WNT/beta-catenin signaling induces changes in key metabolic enzyme that modify their thermodynamics behavior. This leads to activation pyruvate dehydrogenase kinase 1(PDK-1) and monocarboxylate lactate transporter 1 (MCT-1). Consequently, phosphorylation of PDK-1 inhibits pyruvate dehydrogenase complex (PDH). Thus, a large part of pyruvate cannot be converted into acetyl-CoA in mitochondria and in TCA (tricarboxylic acid) cycle. This leads to aerobic glycolysis despite the availability of oxygen, named Warburg effect. Cytoplasmic pyruvate is, in major part, converted into lactate. The WNT/beta-catenin pathway induces also the transcription of genes involved in cell proliferation, cell invasiveness, nucleotide synthesis, tumor growth, and angiogenesis, such as c-Myc, cyclin D1, PDK. In addition, in gliomas cells, PPAR gamma is downregulated, leading to a decrease in insulin sensitivity and an increase in neuroinflammation. Moreover, PPAR gamma contributes to regulate some key circadian genes. Abnormalities in the regulation of circadian rhythms and dysregulation in circadian clock genes are observed in gliomas. Circadian rhythms are dissipative structures, which play a key role in far-from-equilibrium thermodynamics through their interactions with WNT/beta-catenin pathway and PPAR gamma. In gliomas, metabolism, thermodynamics, and circadian rhythms are tightly interrelated.

Abnormal expression of long non-coding RNAs in myocardial infarction

Myocardial infarction (MI) is the leading cause of fatality worldwide. Our study aimed to investigate the dysregulated long non-coding RNA (lncRNA) in MI and elucidate the mechanism of it in MI. The lncRNA and mRNA expression profiling of the whole left ventricular tissue of MI mice model (8 mice) and Sham group (8 mice) was obtained based on microarray analysis. Differentially expressed lnRNAs/mRNA (DELs/DEMs) were identified in MI. DELs/DEMs co-expression network construction, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis were conducted to predict the biological functions of DEMs. Quantitative real-time polymerase chain reaction (qRT-PCR) was subjected to validate the abnormally expressed DELs in left ventricular tissues of MI mice model. Total of 168 DELs (37 up- and 131 down-regulated) and 126 DEMs (87 up- and 39 down-regulated) were identified in MI compared with Sham group. The co-expression network of candidate DELs and DEMs was constructed, which covered 219 nodes and 1775 edges. The qRT-PCR validation results indicated that ENSMUST00000124047 was significantly down-regulated in MI group and AK166279 was significantly up-regulated in MI group. ENSMUST00000121611 and NR_015515 had the up-regulated tendency in MI group compared with Sham group. The DEMs in MI were significantly enriched in 41 signaling pathways including complement and coagulation cascades, cytokine-cytokine receptor interaction and chemokine signaling pathway. The expression profiling of dysregulated DELs in MI was identified. Our results might provide useful information for exploring the pathogenesis mechanism of MI.

Radix Stellariae extract prevents high-fat-diet-induced obesity in C57BL/6 mice by accelerating energy metabolism

Stellaria dichotoma L. is widely distributed in Ningxia and surrounding areas in northwestern China. Its root, Radix Stellariae (RS), has been used in herbal formulae for treating asthenic-fever, infection, malaria, dyspepsia in children and several other symptoms. This study investigated whether the RS extract (RSE) alleviates metabolic disorders. The results indicated that RSE significantly inhibited body weight gain in high-fat (HF)-diet-fed C57BL/6 mice, reduced fasting glucose levels, and improved insulin tolerance. Moreover, RSE increased the body temperature of the mice and the expression of uncoupling proteins and peroxisome proliferator-activated receptors in the white adipose tissue. Thus, RSE alleviated metabolic disorders in HF-diet-fed C57BL/6 mice by potentially activating UCP and PPAR signaling.

PPARs and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) encompasses a range of liver pathology ranging from simple steatosis to varying degrees of inflammation, hepatocyte injury and fibrosis. Without intervention it can progress to end-stage liver disease and hepatocellular carcinoma. Given its close association with obesity, the prevalence of NAFLD has increased dramatically worldwide. Currently, there are no FDA-approved medications for the treatment of NAFLD and although lifestyle modifications with appropriate diet and exercise have been shown to be beneficial, this has been difficult to achieve and sustain for the majority of patients. As such, the search for effective therapeutic agents is an active area of research. Peroxisome proliferator-activated receptors (PPARs) belong to a class of nuclear receptors. Because of their key role in the transcriptional regulation of mediators of glucose and lipid metabolism, PPAR ligands have been investigated as possible therapeutic agents. Here we review the current evidence from preclinical and clinical studies investigating the therapeutic potential of PPAR ligands for the treatment of NAFLD.

Synthesis and anti-obesity effects in vivo of Crotadihydrofuran C as a novel PPARγ antagonist from Crotalaria albida

Crotadihydrofuran C (CC) from the herbs of Crotalaria albida is able to inhibit adipocyte differentiation and lipid accumulation. However, the effects of CC on obesity and metabolic disorders have not yet been elucidated. In our study, the first enantioselective synthesis of the 2-isopropenyl dihydrofuran isoflavone skeleton (CC) is described. The convenient and efficient synthetic protocols developed skilfully solve the problems of the ortho-para directing group and Suzuki coupling reaction using a boronic acid pinacol ester that was more stable and easy to obtain. Furthermore, CC treatment of high-fat diet (HFD)-fed obese mice remarkably reduced their body weight, fat mass, and lipid level as well as improved insulin resistance and non-alcoholic fatty liver disease (NAFLD). A TR-FRET assay showed that CC was specifically bound to PPARγ LBD, which was further confirmed by the molecular docking study. These results suggest that CC could be a useful and potential natural product for treating metabolic diseases, including obesity, hyperlipidemia insulin resistance and NAFLD, without toxic side-effects.

HVC1 ameliorates hyperlipidemia and inflammation in LDLR-/- mice

Background

HVC1 consists of Coptidis Rhizoma (dried rhizome of Coptischinensis), Scutellariae Radix (root of Scutellariabaicalensis), Rhei Rhizoma (rhizome of Rheum officinale), and Pruni Cortex (cortex of Prunusyedoensis Matsum). Although the components are known to be effective in various conditions such as inflammation, hypertension, and hypercholesterolemia, there are no reports of the molecular mechanism of its hypolipidemic effects.

Methods

We investigated the hypolipidemic effect of HVC1 in low-density lipoprotein receptor-deficient (LDLR^−/−) mice fed a high-cholesterol diet for 13 weeks. Mice were randomized in to 6 groups: ND (normal diet) group, HCD (high-cholesterol diet) group, and treatment groups fed HCD and treated with simvastatin (10 mg/kg, p.o.) or HVC1 (10, 50, or 250 mg/kg, p.o.).

Results

HVC1 regulated the levels of total cholesterol, triglyceride (TG), low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol in mouse serum. In addition, it regulated the transcription level of the peroxisome proliferator-activated receptors (PPARs), sterol regulatory element-binding proteins (SREBP)-2, 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase, lipoprotein lipase (LPL), apolipoprotein B (apo B), liver X receptor (LXR), and inflammatory cytokines (IL-1β, IL-6, and TNF-α). Furthermore, HVC1 activated 5′ adenosine monophosphate-activated protein kinase (AMPK).

Conclusion

Our results suggest that HVC1 might be effective in preventing high-cholesterol diet-induced hyperlipidemia by regulating the genes involved in cholesterol and lipid metabolism, and inflammatory responses.

Aggressive Crosstalk Between Fatty Acids and Inflammation in Macrophages and Their Influence on Metabolic Homeostasis

From the immunological point of view, macrophages are required to maintain metabolic homeostasis. Recently, there has been an increased focus on the influence of macrophage phenotypes in adipose tissue on the maintenance of metabolic homeostasis in healthy conditions because dysregulated metabolic homeostasis causes metabolic syndrome. This review notes several types of inflammatory and anti-inflammatory mediators in metabolic homeostasis. M1 macrophage polarization mediates inflammation, whereas M2 macrophage polarization mediates anti-inflammation. Fatty acids and their related factors mediate both inflammatory and anti-inflammatory responses. Saturated fatty acids and polyunsaturated fatty acids mediate inflammation, whereas marine-derived n-3 fatty acids, such as eicosapentaenoic acid and docosahexaenoic acid, mediate anti-inflammation. In this review, we discuss the current understanding of the crosstalk between fatty acids and inflammation in macrophages and their influence on metabolic homeostasis.

Thermodynamics in cancers: opposing interactions between PPAR gamma and the canonical WNT/beta-catenin pathway

Cancer cells are the site of numerous metabolic and thermodynamic abnormalities. We focus this review on the interactions between the canonical WNT/beta-catenin pathway and peroxisome proliferator-activated receptor gamma (PPAR gamma) in cancers and their implications from an energetic and metabolic point of view. In numerous tissues, PPAR gamma activation induces inhibition of beta-catenin pathway, while the activation of the canonical WNT/beta-catenin pathway inactivates PPAR gamma. In most cancers but not all, PPAR gamma is downregulated while the WNT/beta-catenin pathway is upregulated. In cancer cells, upregulation of the WNT/beta-catenin signaling induces dramatic changes in key metabolic enzymes that modify their thermodynamic behavior. This leads to activation of pyruvate dehydrogenase kinase1 (PDK-1) and monocarboxylate lactate transporter. Consequently, phosphorylation of PDK-1 inhibits the pyruvate dehydrogenase complex (PDH). Thus, a large part of pyruvate cannot be converted into acetyl-coenzyme A (acetyl-CoA) in mitochondria and only a part of acetyl-CoA can enter the tricarboxylic acid cycle. This leads to aerobic glycolysis in spite of the availability of oxygen. This phenomenon is referred to as the Warburg effect. Cytoplasmic pyruvate is converted into lactate. The WNT/beta-catenin pathway induces the transcription of genes involved in cell proliferation, i.e., MYC and CYCLIN D1. This ultimately promotes the nucleotide, protein and lipid synthesis necessary for cell growth and multiplication. In cancer, activation of the PI3K-AKT pathway induces an increase of the aerobic glycolysis. Moreover, prostaglandin E2 by activating the canonical WNT pathway plays also a role in cancer. In addition in many cancer cells, PPAR gamma is downregulated. Moreover, PPAR gamma contributes to regulate some key circadian genes. In cancers, abnormalities in the regulation of circadian rhythms (CRs) are observed. CRs are dissipative structures which play a key-role in far-from-equilibrium thermodynamics. In cancers, metabolism, thermodynamics and CRs are intimately interrelated.

Interactions between PPAR Gamma and the Canonical Wnt/Beta-Catenin Pathway in Type 2 Diabetes and Colon Cancer

In both colon cancer and type 2 diabetes, metabolic changes induced by upregulation of the Wnt/beta-catenin signaling and downregulation of peroxisome proliferator-activated receptor gamma (PPAR gamma) may help account for the frequent association of these two diseases. In both diseases, PPAR gamma is downregulated while the canonical Wnt/beta-catenin pathway is upregulated. In colon cancer, upregulation of the canonical Wnt system induces activation of pyruvate dehydrogenase kinase and deactivation of the pyruvate dehydrogenase complex. As a result, a large part of cytosolic pyruvate is converted into lactate through activation of lactate dehydrogenase. Lactate is extruded out of the cell by means of activation of monocarboxylate lactate transporter-1. This phenomenon is called Warburg effect. PPAR gamma agonists induce beta-catenin inhibition, while inhibition of the canonical Wnt/beta-catenin pathway activates PPAR gamma.

Limited Excessive Voluntary Alcohol Drinking Leads to Liver Dysfunction in Mice

BACKGROUND

Liver damage is a serious and sometimes fatal consequence of long-term alcohol intake, which progresses from early-stage fatty liver (steatosis) to later-stage steatohepatitis with inflammation and fibrosis/necrosis. However, very little is known about earlier stages of liver disruption that may occur in problem drinkers, those who drink excessively but are not dependent on alcohol.

METHODS

We examined how repeated binge-like alcohol drinking in C57BL/6 mice altered liver function, as compared with a single binge-intake session and with repeated moderate alcohol consumption. We measured a number of markers associated with early- and later-stage liver disruption, including liver steatosis, measures of liver cytochrome P4502E1 (CYP2E1) and alcohol dehydrogenase (ADH), alcohol metabolism, expression of cytokine mRNA, accumulation of 4-hydroxynonenal (4-HNE) as an indicator of oxidative stress, and alanine transaminase/aspartate transaminase as a measure of hepatocyte injury.

RESULTS

Importantly, repeated binge-like alcohol drinking increased triglyceride levels in the liver and plasma, and increased lipid droplets in the liver, indicators of steatosis. In contrast, a single binge-intake session or repeated moderate alcohol consumption did not alter triglyceride levels. In addition, alcohol exposure can increase rates of alcohol metabolism through CYP2E1 and ADH, which can potentially increase oxidative stress and liver dysfunction. Intermittent, excessive alcohol intake increased liver CYP2E1 mRNA, protein, and activity, as well as ADH mRNA and activity. Furthermore, repeated, binge-like drinking, but not a single binge or moderate drinking, increased alcohol metabolism. Finally, repeated, excessive intake transiently elevated mRNA for the proinflammatory cytokine IL-1B and 4-HNE levels, but did not alter markers of later-stage liver hepatocyte injury.

CONCLUSIONS

Together, we provide data suggesting that even relatively limited binge-like alcohol drinking can lead to disruptions in liver function, which might facilitate the transition to more severe forms of liver damage.

ALOX15 as a suppressor of inflammation and cancer: Lost in the link

Mounting evidence supports a mechanistic link between inflammation and cancer, especially colon cancer. ALOX15 (15-lipoxygenase-1) plays an important role in the formation of key lipid mediators (e.g., lipoxins and resolvins) to terminate inflammation. ALOX15 expression is downregulated in colorectal cancer (CRC). Intestinally-targeted transgenic expression of ALOX15 in mice inhibited dextran sodium sulfate-induced colitis from promoting azoxymethane- induced colorectal tumorigenesis, demonstrating that ALOX15 can suppress inflammation-driven promotion of carcinogen-induced colorectal tumorigenesis and therefore ALOX15 downregulation during tumorigenesis is likely to enhance the link between colitis and colorectal tumorigenesis. ALOX15 suppressed the TNF-α, IL-1β/NF-κB, and IL-6/STAT3 signaling pathways, which play major roles in promotion of colorectal cancer by chronic inflammation. Defining ALOX15's regulatory role in colitis-associated colorectal cancer could identify important molecular regulatory events that could be targeted to suppress promotion of tumorigenesis by chronic inflammation.

Peroxisome proliferator-activated receptor α (PPARα) contributes to control of melanogenesis in B16 F10 melanoma cells

Recent studies revealed the cooperation between peroxisome proliferator-activated receptor gamma (PPARγ) and α-MSH signaling, which results in enhanced melanogenesis in melanocytes and melanoma cells. However, the agonists of PPARα, such as fenofibrate, exert depigmenting effect. Therefore, we aimed to check how the PPARα expression level affects the antimelanogenic activity of fenofibrate and whether PPARα modulates melanogenesis independently of its agonist. To answer these questions, we used three B16 F10-derived cell lines, which varied in the PPARα expression level and were developed by stable transfection with plasmids driving shRNA-based PPARα silencing or overexpression of PPARα-emerald GFP fusion protein. Melanin contents were assessed with electron paramagnetic resonance spectroscopy along with color component image analysis-a novel approach to pigment content characteristics in melanoma cells. B16 F10 wt and Ctrl shRNA lines showed intermediate pigmentation, whereas the pigmentation of the B16 F10-derived cell lines was inversely correlated with the PPARα expression level. We observed that cells overexpressing PPARα were almost amelanotic and cells with reduced PPARα protein level were heavily melanized. Furthermore, fenofibrate down-regulated the melanogenic apparatus (MITF, tyrosinase, and tyrosinase-related proteins) in the cells with the regular PPARα expression level resulting in their visibly lower total melanin content in all the cell lines. From these observations, we conclude that fenofibrate works as a strong depigmenting agent, which acts independently of PPARα, but in an additive fashion. Our results also indicate that alterations in PGC-1a acetylation and expression level might contribute to the regulation of melanogenesis by PPARα and fenofibrate.

Regulation of FADS2 transcription by SREBP-1 and PPAR-α influences LC-PUFA biosynthesis in fish

The present study was conducted to explore the mechanisms leading to differences among fishes in the ability to biosynthesize long-chain polyunsaturated fatty acids (LC-PUFAs). Replacement of fish oil with vegetable oil caused varied degrees of increase in 18-carbon fatty acid content and decrease in n-3 LC-PUFA content in the muscle and liver of rainbow trout (Oncorhynchus mykiss), Japanese seabass (Lateolabrax japonicus) and large yellow croaker (Larimichthys crocea), suggesting that these fishes have differing abilities to biosynthesize LC-PUFAs. Fish oil replacement also led to significantly up-regulated expression of FADS2 and SREBP-1 but different responses of the two PPAR-α homologues in the livers of these three fishes. An in vitro experiment indicated that the basic transcription activity of the FADS2 promoter was significantly higher in rainbow trout than in Japanese seabass or large yellow croaker, which was consistent with their LC-PUFA biosynthetic abilities. In addition, SREBP-1 and PPAR-α up-regulated FADS2 promoter activity. These regulatory effects varied considerably between SREBP-1 and PPAR-α, as well as among the three fishes. Taken together, the differences in regulatory activities of the two transcription factors targeting FADS2 may be responsible for the different LC-PUFA biosynthetic abilities in these three fishes that have adapted to different ambient salinity.