Peroxisome Proliferator-activated Receptor Gene Research Articles

Therapeutic Targeting of PPAR Signaling in Cancer Treatment-Related Lymphedema

Lymphedema secondary to cancer treatment affects up to 1 in 5 cancer survivors. It is an irreversible late normal tissue toxicity characterized by swelling and scar formation (fibrosis) of the affected limb with physical and psychosocial health consequences for patients. Recent evidence reveals changes in peroxisome proliferator-activated receptor (PPAR) signaling as an underlying pathology of this disease. PPAR agonists have demonstrated therapeutic benefit in other fibrotic conditions; their role in lymphedema, however, remains unclear.In this study, RNA-sequencing of human and murine tissues with and without lymphedema was performed. Samples included: human lymphedema (n = 4), human normal tissue control (n = 5, matched for demographics and cancer history), murine lymphedema (n = 12), and murine control (n = 9). Pathway enrichment analysis was performed. An in vitro model of lymphedema fibrosis using cultured transforming growth factor beta (TGFβ)-stimulated fibroblasts and an in vivo model of lymphedema using a murine surgical model of tail lymphedema were utilized to evaluate the effects of PPAR agonists on gene expression and fibrotic protein expression (pro-collagen Iα1, collagen) in lymphedema compared to controls.RNA-sequencing of tissue from human and murine lymphedema and control subjects identified that suppression of PPAR signaling was a hallmark of lymphedema fibrosis on pathway enrichment analysis (FDR < 0.01). In the murine model, PPAR signaling gene expression changes co-occurred with fibrotic deposition beginning as early as two weeks after lymphedema development, and continued for at least 35 weeks. Treatment of TGFβ-stimulated fibroblasts with a PPAR agonist resulted in an increase in expression of PPAR genes and suppression of COL1α1 gene expression (n≥9 per group, q < 0.05) as well as reduction in the secretion of fibrotic proteins: pro-collagen Iα1 on ELISA (n≥8 per group, P < 0.0001) and collagen I on Western blotting. PPAR agonist treatment of the murine model of lymphedema resulted in a significant reduction in lymphedema fibrosis as measured by trichrome collagen staining (n≥4 per group, P < 0.05).These data, for the first time, demonstrated the value of upregulating PPAR signaling to treat lymphedema. For this condition, which to date, has no cure, repurposing PPAR agonists for lymphedema treatment is a highly promising therapeutic opportunity, which warrants further investigation.

Analysis of sepsis-related genes through weighted gene co-expression network

To identify the Key genes in the development of sepsis through Weighted Gene Co-Expression Network Analysis (WGCNA). The gene expression dataset GSE154918 was downloaded from the public database Gene Expression Omnibus (GEO) database, which containes data from 105 microarrays of 40 control cases, 12 cases of asymptomatic infection, 39 cases of sepsis, and 14 cases of follow-up sepsis. The R software was used to screen out differentially expressed genes (DEG) in sepsis, and the Distributed Access View Integrated Database (DAVID), SEARCH TOOL FOR RETRIEVAL OF INTERACTING NEIGHBOURING GENES (STRING) and visualization software Cytoscape were used to perform gene function and pathway enrichment analysis, Protein-protein interaction (PPI) network analysis and key gene analysis to screen out the key genes in the development of sepsis. Forty-six candidate genes were obtained by WGCNA and combined with DEG expression analysis, and these 46 genes were analyzed by gene ontology (GO) and Kyoto City Encyclopedia of Genes and Genomes (KEGG) pathway enrichment to obtain gene functions and involved signaling pathways. The PPI network was further constructed using the STRING database, and 5 key genes were selected by the PPI network visualization software Cytoscape, including the mast cell expressed membrane protein 1 gene (MCEMP1), the S100 calcium-binding protein A12 gene (S100A12), the adipokine resistance factor gene (RETN), the c-type lectin structural domain family 4 member gene (CLEC4D), and peroxisome proliferator-activated receptor gene (PPARG), and differential expression analysis of each of these 5 genes showed that the expression levels of the above 5 genes were significantly upregulated in sepsis patients compared with healthy controls. In this study, 5 key genes related to sepsis were screened by constructing WGCNA method, which may be potential candidate targets related to sepsis diagnosis and treatment.

Paternal trans-fatty acid and vitamin E diet affects rat offspring's semen quality and PPARs expression.

Trans-fatty acids (TFAs) consumption has created concerns regarding male/female reproductive system. However, the effects of TFA in paternal diet on offspring's reproduction have not been addressed. The purpose of this study is to investigate the effects of rat paternal TFAs and vitamin E consumption on offspring's sperm quality and expression pattern of peroxisome proliferator-activated receptors (PPARs) in testis tissues. Forty adult male rats were randomly divided into four groups: Control diet (C); Control diet plus TFA (CTH); diet supplemented with vitamin E (E) and a diet containing vitamin E and TFA (ETH). Mother rats had normal diet during gestation period. Three offspring from each group were chosen randomly and their testicular samples were collected, and sperm parameters were measured by CASA. Our results indicate that feeding fathers with TFA can negatively affect offspring's sperm concentration and motility, while consumption of vitamin E can improve these parameters (p<.05). The paternal diet containing TFA down-regulated the expression of PPARβ and PPARγ genes, whereas vitamin E-containing diet up-regulated the transcription of PPAR genes. In conclusion, TFA intake in paternal diet may have negative effects on reproductive system of the offspring while vitamin E may not diminish these effects.

Developmental exposures to perfluorooctanesulfonic acid (PFOS) impact embryonic nutrition, pancreatic morphology, and adiposity in the zebrafish, Danio rerio.

Perfluorooctanesulfonic acid (PFOS) is a persistent environmental contaminant previously found in consumer surfactants and industrial fire-fighting foams. PFOS has been widely implicated in metabolic dysfunction across the lifespan, including diabetes and obesity. However, the contributions of the embryonic environment to metabolic disease remain uncharacterized. This study seeks to identify perturbations in embryonic metabolism, pancreas development, and adiposity due to developmental and subchronic PFOS exposures and their persistence into later larval and juvenile periods. Zebrafish embryos were exposed to 16 or 32μM PFOS developmentally (1-5 days post fertilization; dpf) or subchronically (1-15 dpf). Embryonic fatty acid and macronutrient concentrations and expression of peroxisome proliferator-activated receptor (PPAR) isoforms were quantified in embryos. Pancreatic islet morphometry was assessed at 15 and 30 dpf, and adiposity and fish behavior were assessed at 15 dpf. Concentrations of lauric (C12:0) and myristic (C14:0) saturated fatty acids were increased by PFOS at 4 dpf, and PPAR gene expression was reduced. Incidence of aberrant islet morphologies, principal islet areas, and adiposity were increased in 15 dpf larvae and 30 dpf juvenile fish. Together, these data suggest that the embryonic period is a susceptible window of metabolic programming in response to PFOS exposures, and that these early exposures alone can have persisting effects later in the lifecourse.

Evidence from Neonatal Piglets Shows How Infant Formula and Other Mammalian Milk Shape Lipid Metabolism

We tested the hypothesis that the consumption of different milk lipids is one of the factors affecting metabolic response to lipid in the early life of infants. Neonatal piglets, as animal models, were stratified by the feeding mode (formula-fed, bovine-, caprine-, and human milk-fed). Lipidomic profiles of plasma and liver samples were detected using liquid chromatography-mass spectrometry (LC-MS). The results indicate that 31, 54, and 28 differential lipid species could be used as potential biomarkers for bovine milk, caprine milk, and infant formula-fed samples, respectively, and the main lipid classes screened in plasma were SM, PC, and PE, including PC(14:1/P-20:0) as the isoform of PC(34:1), which regulates the lipid metabolism gene peroxisome proliferator-activated receptor α, PPAR-α. SM(d15:1/22:0) was the common potential biomarker screened from all of the groups. The amounts of biomarkers screened from the caprine milk-fed liver samples were the highest, which had a significant effect on the distribution of SM, PI, and PA. Infant formula, bovine-, and caprine milk-fed samples had an obvious effect on the metabolism of glycerophospholipid and glycerol ester, especially TG (16:0/18:0/18:2).

Metabolically Flexible CAR T Cells (mfCAR-T), with Constitutive Expression of PGC-1α Resistant to Post Translational Modifications, Exhibit Superior Survival and Function in Vitro

Background: Remarkable durable responses are seen with chimeric antigen receptor (CAR) T cell therapy in B cell lymphoma, however the majority of patients relapse (Locke et al. Lancet Oncol. 2019). Improvements enabling CAR T cells (CAR-T) to circumvent mechanisms of resistance may increase efficacy. Hypoxia, nutrient deprivation and acidosis, all common in the tumor microenvironment (TME), impair metabolic function necessary for CAR-T to kill tumor (Chang et al. Cell 2015). The metabolic response gene peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) co-activates genes that upregulate mitochondrial and glycolytic machinery for ATP synthesis from myriad carbon sources. Post translational modifications (PTM) fine tune PGC-1α activity to meet energy demands (Luo et al. IJC 2019). We hypothesized that CAR-T co-expressing full-length PGC-1α or the truncated (ie. short) NT-PGC-1α isoform, with mutations that prevent suppressive PTMs, would confer metabolic flexibility to improve function under TME conditions. Methods: We constructed four PGC-1α encoded retroviral vectors with an IRES and DsRed fluorescent protein: full-length wild type (WT); full-length mutant (GA); wild type short isoform (NT); and mutant short isoform (mNT). GA contained T295A and S571A mutations to abrogate GSK3β and Akt mediated PTMs. mNT sequence contained K to A mutations at K78/K145/K184/K254 to prevent acetylation by GCN5, and L to A mutations of the nuclear export sequence corresponding to L29/L33/L36/L38. Human CD8 T cells were activated with αCD3/αCD28 beads + 100 IU IL-2/mL, and transduced at 48 hr. to express FMC63-CD28/CD3z CAR and non-functional truncated CD34. Cells were co-transduced with WT, or in the case of metabolically flexible CAR T cells (mfCAR-T) with a mutant and/or short isoform PGC-1α vector. After 7 days of expansion CD34+DsRed+ cells were isolated by FACS. In vitro experiments were performed within 2 weeks to characterize mitochondrial dynamics/oxidative stress (flow cytometry), cytokine secretion (ELISA), and real-time cytotoxicity (xCelligence). The effect of glucose restriction was evaluated in normal (10 mM) and low glucose (0.01 mM) medium. A Mitochondrial stress test (Seahorse) was performed 30 days after FACS. CAR-T (WT and control w/o co-transduction) and mfCAR-T were stimulated with CD19+ K562 or 3T3 cells. Results: Representative PGC-1α metabolic fitness target genes (ERRα, TFAM, and NRF2) were increased in mfCAR T cells (p≤0.001). mfCAR-T exhibited decreased mitochondrial biomass (p≤0.01) and mitochondrial membrane potential (MMP) (p≤0.01) in both glucose conditions. However, MMP:mitochondrial biomass and autophagy were greater (p≤0.01, p≤0.001), suggesting accelerated mitochondrial quality control (MQC). Oxidative stress was generally decreased (p≤0.01) in mfCAR-T, accompanied by reduced apoptosis. All mfCAR and control CAR T cells cytolysed 100% of targets at a 1:1 ratio but differed in cytolytic rate. Relative to CAR only, WT CAR-T and GA mfCAR-T killed 1.6 and 1.9 times faster, while shorter isoforms required 1.9 times longer to lyse all targets. IFNγ and IL-2 secretion by GA-mfCAR-T was increased above control CAR-T and other mfCAR T cells (p≤0.01), while others were similar. At 30 days both WT-CAR-T and all 3 mfCAR-T had increased spare respiratory capacity (SRC) compared to control CAR-T (p≤0.05); however ATP production and OCR/ECAR was increased (p≤0.001, p≤0.0.05) in mfCAR-T above control CAR-T and WT-CAR-T. Conclusion: Enforced expression of mutant or truncated PGC-1α in CAR-T enhanced mitochondrial quality control with commensurate function. mfCAR-T cells exhibited equivalent cytotoxicity in vitro, improved survival, and a metabolism less reliant on glucose. Stark differences in SRC, OCR/ECAR, and mitochondrial ATP production between WT and mfCAR-T suggest signaling pathways in CAR T cells may target PTM mediated suppression of PGC-1α and lead to metabolic exhaustion in the TME. mfCAR-T are a promising new strategy to improve the function of CAR-T cells in the TME. Further in vitro and in vivo experiments are needed to validate the approach. Disclosures Locke: Kite, a Gilead Company: Consultancy, Research Funding; Celgene/Bristol-Myers Squibb: Consultancy; Cellular Biomedicine Group: Other: Consultancy with grant options; Wugen: Consultancy; GammaDelta Therapeutics: Consultancy; Calibr: Consultancy; Allogene: Consultancy; Novartis: Consultancy.

Characterization and comparative DNA methylation profiling of four adipogenic genes in adipose-derived stem cells and dedifferentiated fat cells from aging subjects

Adipose-derived stem cells (ASCs) and dedifferentiated fat (DFAT) cells are alternative cell sources in tissue engineering and regeneration because they are easily obtained and exhibit multilineage differentiation. However, aging may attenuate their regenerative potential and metabolic functions. Reports characterizing DFAT cells derived from aging donors are rare, and comparisons of DNA methylation profiles between aging ASCs and DFAT cells are poorly understood. Therefore, this study aimed to characterize DFAT cells relative to ASCs derived from aging subjects and compare the DNA methylation profiles of four adipogenic genes in these cells. ASCs and DFAT cells from aging donors exhibited characteristics similar to those of stem cells, including colony formation, proliferation, and multilineage differentiation abilities. However, compared with ASCs, DFAT cells exhibited increased proliferation, smooth muscle actin alpha (SMA-α) expression and decreased cellular senescence. DNA methylation profiling of ASCs and DFAT cells by combined bisulfite restriction analysis (COBRA) demonstrated hypermethylation patterns in three potent adipogenic genes—peroxisome proliferator-activated receptor gamma 2 (PPARγ2), fatty acid-binding protein 4 (FABP4), and lipoprotein lipase (LPL)—but hypomethylation of CCAAT/enhancer binding protein alpha (C/EBPα) in the aging group. Statistically significant differences were observed between the aging group and the young group. Epigenetic regulation maintains the stability of ASCs and DFAT cells in an age-dependent manner. Our findings suggested that although the DNA methylation patterns of three adipogenic genes correlated with hypermethylation and aging, ASCs and DFAT cells exhibited cellular stability and several stem cell characteristics, offering further opportunities for personalized regeneration and energy maintenance by adipogenesis during aging.

Association of Peroxisome Proliferator-Activated Receptors (PPARs) with Diabetic Retinopathy in Human and Animal Models: Analysis of the Literature and Genome Browsers.

Diabetic retinopathy (DR) is a condition that develops after long-lasting and poorly handled diabetes and is presently the main reason for blindness among elderly and youth. Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors that are involved in carbohydrate and fatty-acid metabolism and have also been associated with DR. Three PPAR isoforms are known: PPARG, PPARA, and PPARD. In the present study, we retrieved articles reporting associations between PPARs and DR from PubMed database and compiled the data in two catalogues, for human and animal models. Extracted data was then complemented with additional relevant genomic information. Seven retrieved articles reported testing an association between PPARs with DR in human. Four of them concluded association of PPARG and PPARA with DR in European and Asian populations, having a protective role on DR development. One study reported pathogenic role of PPARG, while two articles reported no association between PPARG and DR among Indian and Chinese populations. Six retrieved articles reported testing of involvement of PPARG and PPARA in DR in animal models, including mouse and rat. The review includes case-control studies, meta-analysis, expression studies, animal models, and cell line studies. Despite a large number of documented sequence variants of the PPAR genes available in genome browsers, researchers usually focus on a small set of previously reported variants. Data extraction from Ensembl genome browser revealed several sequence variants with predicted deleterious effect on protein function which present candidates for further experimental validation. Results of the present analysis will enable more holistic approach for understanding of PPARs in DR development. Additionally, developed catalogues present a baseline for standardized reporting of PPAR-phenotype association in upcoming studies.

An Integrated Analysis of mRNA and lncRNA Expression Profiles Indicates Their Potential Contribution to Brown Fat Dysfunction With Aging.

Brown adipose tissue (BAT) can convert fatty acids and glucose into heat, exhibiting the potential to combat obesity and diabetes. The mass and activity of BAT gradually diminishes with aging. As a newly found regulator of gene expression, long non-coding RNAs (lncRNAs) exhibit a wide range of functions in life processes. However, whether long non-coding RNA (lncRNA) involves in BAT dysfunction with aging is still unclear. Here, using RNA-sequencing technology, we identified 3237 messenger RNAs (mRNAs) and 1312 lncRNAs as differentially expressed in BAT of 10-months-old mice compared with 6- to 8-week-old. The protein-protein interaction network and k-score analysis revealed that the core mRNAs were associated with two important aging-related pathways, including cell cycle and p53 signaling pathway. Gene set enrichment analysis indicated that these mRNAs might participate in lipid metabolism and brown fat dysfunction. Functional enrichment analyses demonstrated that dysregulated lncRNAs were associated with mitochondria, regulation of cellular senescence, cell cycle, metabolic and p53 signaling pathways. Moreover, we revealed that two lncRNAs (NONMMUT024512 and n281160) may involve in the regulation of their adjacent gene peroxisome proliferator-activated receptor alpha (Pparα), a thermogenesis regulator. Collectively, these results lay a foundation for extensive studies on the role of lncRNAs in age-related thermogenic degradation.

Omega3-polyunsaturated fatty acid ameliorates metabolic disorders in adulthood rats caused by postnatal early overfeeding

Objective To explore the effect and mechanism of omega 3-polyunsaturated fatty acid(ω3-PUFA) dietary intervention on mitochondrial function of white adipose tissue in adult rats with postnatal early overfeeding. Methods An overfed animal model by adjusting litter size was developed for the study of neonatal overfeeding. The litter size was adjusted to 3 male rats per litter(small litter, SL group) and 10 pups per litter(normal litter, NL group). After weaning(week 3), the pups were fed standard chow or ω3-PUFA diet(SL-FO) until postnatal weeks 13. Food intake, body weight, and rectal temperature of rats were measured regularly, and energy metabolism of animals was monitored in week 13. During week 3 and 13, subcutaneous adipose tissue was collected. Inguinal preadipocytes of mice were isolated and induced to differentiate, and 50 μmol/L eicosapentaenoicacid(EPA) was administered for 48 h at the late stage of differentiation. The mRNA and protein expression levels of mitochondrial related genes, mitochondrial copy number, and oxygen consumption rate of adipocytes were detected in adipose tissue and adipocytes. Results By the 3rd week, the body weight, food intake, and fat cell area in SL group were higher than those in NL group while the body temperature was lower until to 13 weeks. By the 13th week, the O2 consumption, CO2 output, and heat production of rats in SL group were lower than those in NL group. Meanwhile, the expressions of mitochondrial function related genes such as uncoupling protein 1(UCP1), carnitine palmitoyltransferase 1(CPT1), SIRT1, and mitochondrial biosynthesis regulatory gene peroxisome proliferator-activated receptor coativator-1 (PGC1α) in adipose tissue by the 3rd and 13th week were significantly reduced(P<0.05). After weaning, ω3-PUFA diet significantly reduced weight gain in SL rats, increased UCP1 protein expression, restored energy metabolism level and mitochondrial function related gene expression. In vitro intervention of EPA increased the mitochondrial copy number, the mRNA and protein expression levels of mitochondrial biosynthesis and functional genes, as well as the mitochondrial basic oxygen consumption rate(P<0.05). Conclusion ω3-PUFA improves postnatal overfeeding-induced impairment of the mitochondrial function and biosynthesis of subcutaneous white adipose tissue in rats, which may be an important mechanism for fish oil diet to inhibit the early over-nutrition program and restore the thermogenic metabolism. Key words: Omega 3-PUFA; Postnatal overfeeding; White fat; Mitochondria

Sphingolipid Synthesis Inhibition by Myriocin Administration Enhances Lipid Consumption and Ameliorates Lipid Response to Myocardial Ischemia Reperfusion Injury.

Myocardial infarct requires prompt thrombolytic therapy or primary percutaneous coronary intervention to limit the extent of necrosis, but reperfusion creates additional damage. Along with reperfusion, a maladaptive remodeling phase might occur and it is often associated with inflammation, oxidative stress, as well as a reduced ability to recover metabolism homeostasis. Infarcted individuals can exhibit reduced lipid turnover and their accumulation in cardiomyocytes, which is linked to a deregulation of peroxisome proliferator activated receptors (PPARs), controlling fatty acids metabolism, energy production, and the anti-inflammatory response. We previously demonstrated that Myriocin can be effectively used as post-conditioning therapeutic to limit ischemia/reperfusion-induced inflammation, oxidative stress, and infarct size, in a murine model. In this follow-up study, we demonstrate that Myriocin has a critical regulatory role in cardiac remodeling and energy production, by up-regulating the transcriptional factor EB, PPARs nuclear receptors and genes involved in fatty acids metabolism, such as VLDL receptor, Fatp1, CD36, Fabp3, Cpts, and mitochondrial FA dehydrogenases. The overall effects are represented by an increased β–oxidation, together with an improved electron transport chain and energy production. The potent immunomodulatory and metabolism regulatory effects of Myriocin elicit the molecule as a promising pharmacological tool for post-conditioning therapy of myocardial ischemia/reperfusion injury.

The pan-cancer mutational landscape of the PPAR pathway reveals universal patterns of dysregulated metabolism and interactions with tumor immunity and hypoxia.

Peroxisome proliferator-activated receptors (PPARs) are a family of nuclear receptors that regulate lipid metabolism and bioenergetic demands within living systems. Consequently, aberrant expression of PPAR genes could predispose individuals to diseases, including cancer. PPAR signaling exerts pleiotropic functions in cancer, yet little is known about the interactions between genetic and transcriptional events of pathway genes in a pan-cancer context. Employing multidimensional datasets of over 18,000 patients involving 21 cancers, we performed systematic characterization on copy number alteration and differential transcript expression of 74 PPAR pathway genes. We identified 18 genes demonstrating mutually exclusive patterns of loss- and gain-of-function phenotypes. These genes successfully predicted patient survival rates in bladder, renal, glioma, liver, and stomach/esophageal cancers. Dysregulated PPAR signaling in these cancers converged on common downstream pathways associated with multiple metabolic processes. Moreover, clinically relevant relationships between PPARs and hypoxia were observed, where hypoxia further aggravates disease phenotypes in tumor subtypes with aberrant PPAR signaling. In glioma samples, including astrocytoma and oligoastrocytoma, PPAR hyperactivation is associated with immunosuppression through increased regulatory T cell expression. Our analysis reveals underappreciated levels of diversity and conservation in PPAR genes that could lay the groundwork for therapeutic strategies targeting tumor metabolism, immunity, and hypoxia.

Do arachidonic acid metabolites affect apoptosis in bovine endometrial cells with silenced PPAR genes?

Peroxisome proliferator-activated receptors (PPARs) are expressed in bovine uterus, and their agonists are arachidonic acid (AA) metabolites. We hypothesised that silencing of PPAR genes in bovine endometrial stromal cells (ESC) would change the intracellular signalling through PPAR and affect apoptosis after cell treatment with different AA metabolites. The study’s aims are detection of apoptosis and examining the influence of prostaglandins and leukotrienes on apoptosis occurring in physiological ESC and cells with silenced PPAR (α, δ, and γ) genes. Silencing the PPARα and PPARδ genes in cells resulted in increased DNA fragmentation and mRNA and protein expression of caspase (CASP) -3 and -8 (P < 0.05). Neither DNA fragmentation nor the mRNA and protein expression of CASP3 and -8 in cells with silenced PPARγ gene were changed compared to physiological cells (P > 0.05). Among PPARs, PPARα and PPARδ appear to inhibit apoptosis, and AA metabolites, as PPAR agonists, modify this process in bovine ESC.

Genetic polymorphisms of PPAR genes and human cancers: evidence for gene–environment interactions

Peroxisome proliferator-activated receptors (PPARs) are nuclear transcription factors that play a role in lipid metabolism, cell proliferation, terminal differentiation, apoptosis, and inflammation. Although several cancer models have been suggested to explain PPARs’ involvement in tumorigenesis, however, their role is still unclear. In this review, we examined associations of the different PPARs, polymorphisms and various types of cancer with a focus on gene–environment interactions. Reviewed evidence suggests that functional genetic variants of the different PPARs may modulate the relationship between environmental exposure and cancer risk. In addition, this report unveils the scarcity of reliable quantitative environmental exposure data when examining these interactions, and the current gaps in studying gene–environment interactions in many types of cancer, particularly colorectal, prostate, and bladder cancers.

Selenate Prevents Adipogenesis through Induction of Selenoprotein S and Attenuation of Endoplasmic Reticulum Stress.

The conversion of preadipocytes to adipocytes (adipogenesis) is a potential target to treat or prevent obesity. Selenate, an inorganic form of selenium, elicits diverse health benefits, mainly through its incorporation into selenoproteins. The individual roles of selenium and certain selenoproteins have been reported. However, the effects of selenate treatment on selenoproteins in adipocytes are unclear. In this study, the effects of selenate pretreatment on selenoprotein and endoplasmic reticulum (ER) stress during adipogenesis were examined in vitro. The selenate pretreatment dose-dependently suppressed the adipogenesis of 3T3-L1 preadipocytes. The selenate pretreatment at 50 μM for 24 h almost completely suppressed adipogenesis without cytotoxic effects. The expression of the adipogenic genes peroxisome proliferator-activated receptor gamma, CCAAT-enhancer binding protein alpha, and leptin was suppressed by selenate. This pretreatment also upregulated selenoprotein S (SEPS1), an ER resident selenoprotein that reduces ER stress, and prevented dexamethasone-induced SEPS1 degradation during the early stage of adipogenesis. The selenate-inhibited adipogenesis was associated with an attenuation of ER stress. The expression of the ER stress marker genes was upregulated during the early stage of differentiation, whereas the selenate pretreatment suppressed the mRNA expression of the XBP1 and C/EBP homologous protein. The collective data suggest a preventive role of selenate and SEPS1 in adipogenesis, and support a novel dietary approach to prevent obesity.

HS218 as an FXR antagonist suppresses gluconeogenesis by inhibiting FXR binding to PGC-1α promoter

IntroductionFarnesoid X receptor (FXR) as a member of nuclear receptor is tightly associated with glucose metabolism. Accumulated evidence has addressed the potential of FXR antagonist in the treatment of type 2 diabetes mellitus (T2DM), although the related mechanisms remain unclear. Here, we determined a specific FXR antagonist HS218 (N-benzyl-N-(3-(tert-butyl)-4-hydroxyphenyl)-2,4-dichlorobenzamide), which exhibited high activities in suppressing gluconeogenesis and ameliorating glucose homeostasis in db/db and HFD/STZ-induced T2DM mice. We would like to investigate the mechanisms underlying FXR antagonism in the regulation of gluconeogenesis by using HS218 as a probe. MethodsHS218 was evaluated by glucose output assay. Binding affinity of HS218 to the ligand binding domain of FXR (FXR-LBD) was detected by Surface Plasmon Resonance (SPR) technology-based Biacore and fluorescence quenching assays. Mammalian one-hybrid and transactivation assays were carried out to detect the antagonistic effect of HS218 on FXR. Real-time PCR assay was performed to measure the expressions of FXR-target and gluconeogenic genes. Anti-diabetic efficiencies of HS218 were determined in db/db and HFD/STZ-induced T2DM mice. Assays by promoter 5′-deletion analysis and Chromatin immunoprecipitation (ChIP) were performed to detect the binding of FXR to peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) promoter. Western blot assay was used to determine the protein level in either cells or the liver tissues of mice. ResultsWe determined that HS218 as a new FXR specific antagonist could FXR-dependently suppress gluconeogenesis in mouse primary hepatocytes, and effectively improve glucose homeostasis in db/db and HFD/STZ-induced T2DM mice. HS218 decreased gluconeogenesis by inhibiting the FXR-induced increase in the promoter activity of the key gluconeogenic gene PGC-1α, leading to the repression of PGC-1α and its target gene peroxisome proliferator-activated receptor α (PPARα). ConclusionsTo our knowledge, our work might be the first report on the mechanism underlying FXR antagonist in the regulation of gluconeogenesis, and all results have also highlighted the potential of HS218 in the treatment of T2DM.

The influence of arachidonic acid metabolites on PPAR and RXR expression in bovine uterine cells

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the superfamily of nuclear receptors. Three isoforms have been described: alpha (PPARα), delta (PPARδ), and gamma (PPARγ). PPARs heterodimerize with retinoid X receptors (RXRs: RXRα, RXRβ and RXRγ). PPAR activity can be modulated by several ligands, including arachidonic acid (AA) metabolites. The aims of the study were to determine the effect of AA metabolites (prostaglandin [PG]E2, PGF2α, leukotriene [LT]B4, and LTC4) on mRNA (real-time PCR) and protein expression (Western blotting) of PPARα, PPARδ, and PPARγ, and on mRNA expression of RXRα, RXRβ, and RXRγ, in bovine epithelial, stromal, and myometrial primary uterine cells and in bovine stromal cells with silenced PPAR genes (N = 10). All PPAR and RXR isoforms were expressed. Prostaglandins affected expression of PPARs only in stromal cells, whereas LTs modulated PPARγ mRNA expression in epithelial and myometrial primary cells. Blockade of signal transduction through PPARs prevented interactions between AA metabolites and PPARs and changed RXR expression comparing with primary stromal cells. In primary stromal uterine cells, mRNA expression of RXRs was higher than that of PPARs. In uterine stromal cells in which intracellular signaling through PPARs was blocked, RXRs seem to take over the role of PPARs and are pivotal for cell functions. This study revealed the reaction of PPARs and RXRs to agonists which naturally occur in the bovine uterus.

Intestinal epithelial Toll-like receptor 4 prevents metabolic syndrome by regulating interactions between microbes and intestinal epithelial cells in mice.

Little is known about the pathogenesis of metabolic syndrome, although Toll-like receptor 4 (TLR4) has been implicated. We investigated whether TLR4 in the intestinal epithelium regulates metabolic syndrome by coordinating interactions between the luminal microbiota and host genes that regulate metabolism. Mice lacking TLR4 in the intestinal epithelium (TLR4ΔIEC), but not mice lacking TLR4 in myeloid cells nor mice lacking TLR4 globally, developed metabolic syndrome; these features were not observed in TLR4ΔIEC mice given antibiotics. Metagenomic analysis of the fecal microbiota revealed differences between TLR4ΔIEC and wild type mice, while meta-transcriptome analysis of the microbiota showed that intestinal TLR4 affected the expression of microbial genes involved in the metabolism of lipids, amino acids, and nucleotides. Genes regulated by peroxisome proliferator-activated receptors (PPARs) and the antimicrobial peptide lysozyme were significantly down-regulated in TLR4ΔIEC mice, suggesting a mechanism by which intestinal TLR4 could exert its effects on the microbiota and metabolic syndrome. Supportingly, antibiotics prevented both downregulation of PPAR genes and the development of metabolic syndrome, while PPAR agonists prevented development of metabolic syndrome in TLR4ΔIEC mice. Thus, intestinal epithelial TLR4 regulates metabolic syndrome through altered host-bacterial signaling, suggesting that microbial or PPAR based strategies might have therapeutic potential for this disease.

Long-chain polyunsaturated fatty acids and extensively hydrolyzed casein-induced browning in a Ucp-1 reporter mouse model of obesity.

Browning in adipose tissues, which can be affected by diet, may mitigate the detrimental effects of adiposity and improve longer-term metabolic health. Here, browning-inducing effects of long-chain polyunsaturated fatty acids, e.g., arachidonic acid (ARA)/docosahexaenoic acid (DHA) and extensively hydrolyzed casein (eHC) were investigated in uncoupling protein 1 (Ucp-1) reporter mice. To address the overall functionality, their potential role in supporting a healthy metabolic profile under obesogenic dietary challenges later in life was evaluated. At weaning Ucp1+/LUC reporter mice were fed a control low fat diet (LFD) with or without ARA + DHA, eHC or eHC + ARA + DHA for 8 weeks until week 12 after which interventions continued for another 12 weeks under a high-fat diet (HFD) challenge. Serology (metabolic responses and inflammation) and in vivo and ex vivo luciferase activity were determined; in the meantime browning-related proteins UCP-1 and the genes peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), PR domain containing 16 (PRDM16) and Ucp-1 were examined. ARA + DHA, eHC or their combination reduced body weight gain and adipose tissue weight compared to the HFD mice. The interventions induced Ucp-1 expression in adipose tissues prior to and during the HFD exposure. Ucp-1 induction was accompanied by higher PGC1a and PRDM16 expression. Glucose tolerance and insulin sensitivity were improved coinciding with lower serum cholesterol, triglycerides, free fatty acids, insulin, leptin, resistin, fibroblast growth factor 21, alanine aminotransferase, aspartate aminotransferase and higher adiponectin than the HFD group. HFD-associated increased systemic (IL-1β and TNF-α) and adipose tissue inflammation (F4/80, IL-1β, TNF-α, IL-6) was reduced. Studies in a Ucp-1 reporter mouse model revealed that early intervention with ARA/DHA and eHC improves metabolic flexibility and attenuates obesity during HFD challenge later in life. Increased browning is suggested as, at least, part of the underlying mechanism.

Xuezhikang contributes to greater triglyceride reduction than simvastatin in hypertriglyceridemia rats by up-regulating apolipoprotein A5 via the PPARα signaling pathway.

Xuezhikang (XZK), an extract of Chinese red yeast rice, is recommended as an optimal choice for patients with coronary heart disease (CHD) with markedly elevated triglyceride (TG) levels. This study was designed to compare the hypotriglyceridemic effects between XZK and simvastatin. The role of apolipoprotein A5 (apoA5), a key regulator of TG metabolism and a target gene of peroxisome proliferator-activated receptor α (PPARα), was to be identified in XZK-related hypotriglyceridemic actions. For these goals, hypertriglyceridemia of rats was induced by a high-fructose diet. In order to investigate the hypotriglyceridemic effects of XZK and simvastatin on these animals based on an equivalent low-density lipoprotein cholesterol (LDL-C) lowering power, we titrated their doses (XZK 80 mg/kg/d versus simvastatin 1 mg/kg/d) according to plasma LDL-C reduction of rats. Similarly, we titrated the target doses of the two agents (XZK 500 μg/ml versus simvastatin 10 μM) according to hepatocyte LDL receptor expressions, and then compared the effects of the two agents on TG and apoA5 of hepatocytes in vitro. Our results showed that XZK (80 mg/kg/d) had higher hypotriglyceridemic performance than simvastatin (1 mg/kg/d) on these animals albeit their equivalent LDL-C lowering power. Higher plasma apoA5 levels and hepatic apoA5 expressions were observed in rats treated with XZK (80 mg/kg/d) than simvastatin (1 mg/kg/d). Further, XZK (80 mg/kg/d) contributed to higher hepatic PPARα expressions of rats than simvastatin (1 mg/kg/d). Although the two agents led to an equivalent up-regulation of LDL receptors of hepatocytes, more TG reduction and apoA5 elevation were detected in hepatocytes treated with XZK (500 μg/ml) than simvastatin (10 μM). However, PPARα knockdown eliminated the above effects of XZK on hepatocytes. Therefore, our study indicates that XZK has greater hypotriglyceridemic performance than simvastatin in the setting of an equivalent LDL-C lowering power, which is attributed to more apoA5 up-regulation by this agent via the PPARα signaling pathway.