Curcumin Inhibits the PPARδ-p-Akt-GLUT1 Pathway and Ameliorates the Antiproliferative Effects of Doxorubicin in MDA-MB-231 Cells.

OBJECTIVE: The aim of the present study was to examine whether GLUT1 was involved in the antiproliferative activity of curcumin and doxorubicin by understanding mechanistically how curcumin regulated GLUT1. METHODS: Expression level of GLUT1 in MCF-7 and MDA-MB-231 cells were quantitated using quantitative real-time PCR and western blot. GLUT1 activity was inhibited in MDA-MB-231 cells with the pharmacological inhibitor WZB117 to assess the anti-proliferative effects of doxorubicin using MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide).  To examine cell proliferation, trypan blue assay was used in cells transfected with GLUT1 siRNA or plasmid overexpressing GLUT1 with doxorubicin and/or commercially available curcumin. The role of PPARδ and Akt on the regulation of GLUT1 by curcumin was examined by overexpressing these proteins and western blot was employed to examine their protein expression. RESULTS: The data revealed that there was a 1.5 fold increase in GLUT1 mRNA and protein levels in MDA-MB-231 compared to MCF-7.  By inhibiting GLUT1 in triple negative breast cancer cell line, MDA-MB-231 with either the pharmacological inhibitor WZB117 or with GLUT1 siRNA, we observed the enhanced antiproliferative effects of doxorubicin. Additional observations indicated these effects can be reversed by the overexpression of GLUT1. Treatment of MDA-MB-231 with curcumin also revealed downregulation of GLUT1, with further growth suppressive effects when combined with doxorubicin.  Overexpression of GLUT1 blocked the growth suppressive role of curcumin and doxorubicin (p< 0.05). Mechanistically, we also observed that the regulation of GLUT1 by curcumin was mediated by the Peroxisome proliferator-activated receptor (PPAR) δ/Akt pathway. CONCLUSION: Our study demonstrates that regulation of GLUT1 by curcumin via the PPARδ/Akt signaling improves the efficacy of doxorubicin by promoting its growth inhibitory effects in MDA-MB-231 cells.

Melatonin Enhanced Microglia M2 Polarization in Rat Model of Neuro-inflammation Via Regulating ER Stress/PPARδ/SIRT1 Signaling Axis.

Neuro-inflammation involves distinct alterations of microglial phenotypes, containing nocuous pro-inflammatory M1-phenotype and neuroprotective anti-inflammatory M-phenotype. Currently, there is no effective treatment for modulating such alterations. M1/M2 marker of primary microglia influenced by Melatonin were detected via qPCR. Functional activities were explored by western blotting, luciferase activity, EMSA, and ChIP assay. Structure interaction was assessed by molecular docking and LIGPLOT analysis. ER-stress detection was examined by ultrastructure TEM, calapin activity, and ERSE assay. The functional neurobehavioral evaluations were used for investigation of Melatonin on the neuroinflammation in vivo. Melatonin had targeted on Peroxisome Proliferator Activated Receptor Delta (PPARδ) activity, boosted LPS-stimulated alterations in polarization from the M1 to the M2 phenotype, and thereby inhibited NFκB-IKKß activation in primary microglia. The PPARδ agonist L-165,041 or over-expression of PPARδ plasmid (ov-PPARδ) showed similar results. Molecular docking screening, dynamic simulation approaches, and biological studies of Melatonin showed that the activated site was located at PPARδ (phospho-Thr256-PPARδ). Activated microglia had lowered PPARδ activity as well as the downstream SIRT1 formation via enhancing ER-stress. Melatonin, PPARδ agonist and ov-PPARδ all effectively reversed the above-mentioned effects. Melatonin blocked ER-stress by regulating calapin activity and expression in LPS-activated microglia. Additionally, Melatonin or L-165,041 ameliorated the neurobehavioral deficits in LPS-aggravated neuroinflammatory mice through blocking microglia activities, and also promoted phenotype changes to M2-predominant microglia. Melatonin suppressed neuro-inflammation in vitro and in vivo by tuning microglial activation through the ER-stress-dependent PPARδ/SIRT1 signaling cascade. This treatment strategy is an encouraging pharmacological approach for the remedy of neuro-inflammation associated disorders.

Seladelpar combined with complementary therapies improves fibrosis, inflammation, and liver injury in a mouse model of nonalcoholic steatohepatitis.

Seladelpar, a selective peroxisome proliferator-activated receptor δ (PPARδ) agonist, improves markers of hepatic injury in human liver diseases, but histological improvement of nonalcoholic steatohepatitis (NASH) and liver fibrosis has been challenging with any single agent. To discover how complementary agents could work with seladelpar to achieve optimal outcomes, this study evaluated a variety of therapeutics (alone and in combination) in a mouse model of NASH. Mice on a high-fat amylin liver NASH (AMLN) diet were treated for 12 wk with seladelpar, GLP-1-R (glucagon-like peptide-1 receptor) agonist liraglutide, apoptosis signal-regulating kinase 1 (ASK1) inhibitor selonsertib, farnesoid X receptor (FXR) agonist obeticholic acid, and with seladelpar in combination with liraglutide or selonsertib. Seladelpar treatment markedly improved plasma markers of liver function. Seladelpar alone or in combination resulted in stark reductions in liver fibrosis (hydroxyproline, new collagen synthesis rate, mRNA indices of fibrosis, and fibrosis staining) compared with vehicle and the other single agents. Robust reductions in liver steatosis were also observed. Seladelpar produced a reorganization of metabolic gene expression, particularly for those genes promoting peroxisomal and mitochondrial lipid oxidation. In summary, substantial improvements in NASH and NASH-induced fibrosis were observed with seladelpar alone and in combination with liraglutide in this model. Broad gene expression analysis suggests seladelpar should be effective in concert with diverse mechanisms of action.NEW & NOTEWORTHY NASH is a chronic, progressive, and increasingly problematic liver disease that has been resistant to treatment with individual therapeutics. In this study using a diet-induced mouse model of NASH, we found that the PPARδ agonist seladelpar reduced fibrosis and NASH pathology alone and in combinations with a GLP-1-R agonist (liraglutide) or an ASK1 inhibitor (selonsertib). Liver transcriptome analysis comparing each agent and coadministration suggests seladelpar should be effective in combination with a variety of therapeutics.

Perturbation of IP3R-dependent endoplasmic reticulum calcium homeostasis by PPARδ-activated metabolic stress leads to mouse spermatocyte apoptosis: A direct mechanism for perfluorooctane sulfonic acid-induced spermatogenic disorders.

Perfluorooctane sulfonic acid (PFOS) as an archetypal representative of per- and polyfluoroalkyl substances (PFAS) is ubiquitously distributed in the environment and extensively detected in human bodies. Although accumulating evidence is suggestive of the deleterious effects of PFOS on male reproduction, the direct toxicity of PFOS towards spermatogenic cells and the relevant mechanisms remain poorly understood. The aims of the present study were to explore the direct effects and underlying molecular mechanisms of PFOS on spermatogenesis. Through integrating animal study, transcriptome profiling, in silico toxicological approaches, and in vitro validation study, we identified the molecular initiating event and key events contributing to PFOS-induced spermatogenic impairments. The mouse experiments revealed that spermatocytes were involved in PFOS-induced spermatogenic disorders and the activation of peroxisome proliferator-activated receptor delta (PPARδ) was linked to spermatocyte loss in PFOS-administrated mice. GC-2spd(ts) cells were treated with an increased gradient of PFOS, which was relevant to environmental and occupational exposure levels of PFOS in populations. Following 72-h treatment, cells was harvested for RNA sequencing. The transcriptome profiling and benchmark dose (BMD) modeling identified endoplasmic reticulum (ER) stress as the key event for PFOS-mediated spermatocyte apoptosis and determined the point-of-departure (PoD) for perturbations of ER stress signaling. Based on the calculated PoD value, further bioinformatics analyses combined with in vitro and in vivo validations showed that PFOS caused metabolic stress by activating PPARδ in mouse spermatocytes, which was responsible for Beclin 1-involved inositol 1,4,5-trisphosphate receptor (IP3R) sensitization. The disruption of IP3R-mediated ER calcium homeostasis triggered ER calcium depletion, leading to ER stress and apoptosis in mouse spermatocytes exposed to PFOS. This study systematically investigated the direct impacts of PFOS on spermatogenesis and unveiled the relevant molecular mechanism of PFOS-induced spermatogenic disorders, providing novel insights and potential preventive/therapeutic targets for PFAS-associated male reproductive toxicity.

Berberine activates PPARδ and promotes gut microbiota-derived butyric acid to suppress hepatocellular carcinoma.

BACKGROUND: Peroxisome proliferator-activated receptors (PPARs) are a family of ligand-inducible transcription factors that govern various essential metabolic activities in the liver and other organs. Recently, berberine (BBR) has been characterized as a modulator of PPARs; however, the matter of whether PPARs are involved in the inhibitory effect of BBR on hepatocellular carcinoma (HCC) is not well understood. PURPOSE: This study aimed to investigate the role of PPARs in the suppressive effect of BBR on HCC and to elucidate the relative mechanism. METHODS: We studied the role of PPARs in the anti-HCC effects of BBR both in vitro and in vivo. The mechanism whereby BBR regulated PPARs was studied using real-time PCR, immunoblotting, immunostaining, luciferase, and a chromatin immunoprecipitation coupled PCR assay. Additionally, we used adeno-associated virus (AAV)-mediated gene knockdown to address the effect of BBR more effectively. RESULTS: We demonstrated that PPARδ played an active role in the anti-HCC effect of BBR, rather than PPARα or PPARγ. Following a PPARδ-dependent manner, BBR increased BAX, cleaved Caspase 3, and decreased BCL2 expression to trigger apoptotic death, thereby suppressing HCC development both in vitro and in vivo. It was noted that the interactions between PPARδ and the apoptotic pathway resulted from the BBR-induced upregulation of the PPARδ transcriptional function; that is, the BBR-induced activation of PPARδ could mediate the binding with the promoters of apoptotic genes such as Caspase 3, BAX, and BCL2. Moreover, gut microbiota also contributed to the suppressive effect of BBR on HCC. We found that BBR treatment restored the dysregulated gut microbiota induced by the liver tumor burden, and a functional gut microbial metabolite, butyric acid (BA), acted as a messenger in the gut microbiota-liver axis. Unlike BBR, the effects of BA suppressing HCC and activating PPARδ were not potent. However, BA was able to enhance the efficacy of BBR by reducing PPARδ degradation through a mechanism to inhibit the proteasome ubiquitin system. Additionally, we found that the anti-HCC effect of BBR or a combination of BBR and BA was much weaker in mice with AAV-mediated PPARδ knockdown than those in the control mice, suggesting the critical role of PPARδ. CONCLUSION: In summary, this study is the first to report that a liver-gut microbiota-PPARδ trilogy contributes to the anti-HCC effect of BBR. BBR not only directly activated PPARδ to trigger apoptotic death but also promoted gut microbiota-derived BA production, which could reduce PPARδ degradation to enhance the efficacy of BBR.

Regulation of adipogenesis through retinoid X receptor and/or peroxisome proliferator-activated receptor by designed lignans based on natural products in 3T3-L1 cells.

We previously synthesized two retinoid X receptor (RXR) agonists, 4'-hydroxy-3'-propyl-[1,1'-biphenyl]-3-propanoic acid ethyl ester (4'OHE) and 6-hydroxy-3'-propyl-[1,1'-biphenyl]-3-propanoic acid ethyl ester (6OHE), based on the structure of magnaldehyde B, a natural product obtained from Magnolia obovata. 4'OHE and 6OHE exhibited different selectivities for peroxisome proliferator-activated receptor (PPAR)/RXR heterodimers. To examine the regulatory effects of these compounds in adipogenesis, 3T3-L1 mouse preadipocytes were treated with a differentiation cocktail with or without test compounds to induce differentiation, and subsequently treated with test compounds in insulin-containing medium every alternate day. Lipid droplets were stained with Oil Red O to examine lipid accumulation. In addition, adipogenesis-related gene expression was measured using RT-qPCR and immunoblotting. The results showed that a PPARγ agonist, 4'OHE, which exerts agonistic effects on PPARγ and RXRα, enhanced adipogenesis similar to rosiglitazone. However, unlike GW501516, a PPARδ agonist, 6OHE and its hydrolysis product (6OHA), which exert agonistic effects on PPARδ and RXRα, suppressed adipogenesis. In a manner similar to 6OHE and 6OHA, bexarotene, an RXR agonist, suppressed adipocyte differentiation, and its anti-adipogenic effect was reversed by an RXR antagonist. Furthermore, 6OHA and bexarotene inhibited the increase in Pparγ2 and Cebpa mRNA levels 2 days after the induction of differentiation. We demonstrated the adipogenic effect of 4'OHE and anti-adipogenic effects of 6OHE and 6OHA in 3T3-L1 cells. Previously, RXR agonists have been reported to positively regulate the differentiation of mesenchymal stem cells into adipocytes, but our current data showed that they inhibited the differentiation of preadipocytes, at least 3T3-L1 cells, into adipocytes.

Capmatinib suppresses LPS-induced interaction between HUVECs and THP-1 monocytes through suppression of inflammatory responses.

BACKGROUND: Capmatinib (CAP) is a drug that has been used to treat non-small cell lung cancer (NSCLC) in adults. Presently, its novel effects on skeletal muscle insulin signaling, inflammation, and lipogenesis in adipocytes have been uncovered with a perspective of drug repositioning. However, the impact of CAP on LPS-mediated interaction between human umbilical vein endothelial cells (HUVECs) and THP-1 monocytes has yet to be investigated. METHODS: HUVECs and THP-1 monocytes were treated with LPS and CAP. The protein expression levels were determined using Western blotting. Target protein knockdown was conducted using small interfering (si) RNA transfection. Interactions between HUVECs and THP-1 cells were assayed using green fluorescent dye. RESULTS: This study found that CAP treatment ameliorated cell adhesion between THP-1 monocytes and HUVECs and the expression of adhesive molecules, such as intracellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin. Moreover, phosphorylation of inflammatory markers, such as NFκB and IκB as well as TNFα and monocyte chemoattractant protein-1 (MCP-1) released from HUVECs and THP-1 monocytes, was prevented by CAP treatment. Treatment with CAP augmented PPARδ and IL-10 expression. siRNA-associated suppression of PPARδ and IL-10 abolished the effects of CAP on cell interaction between HUVECs and THP-1 cells and inflammatory responses. Further, PPARδ siRNA mitigated CAP-mediated induction of IL-10 expression. CONCLUSION: These findings imply that CAP improves inflamed endothelial-monocyte adhesion via a PPARδ/IL-10-dependent pathway. The current study provides in vitro evidence for a therapeutic approach for treating atherosclerosis.

Effect of caffeine on mitochondrial biogenesis in the skeletal muscle - A narrative review.

Caffeine is one of the most widely used substances as recreational drug for performance-enhancement in sport, underpinned by a strong evidence base. Although the effects of caffeine are widely investigated within the scope of performance physiology, the molecular effects of caffeine within skeletal muscle remain unclear. Evidence from in vitro and in vivo models suggest that caffeine regulates the glucose metabolism in the skeletal muscle. Moreover, caffeine seems to stimulate CaMKII, PPARδ/ß, AMPK and PGC1α, classical markers of exercise-adaptations, including mitochondrial biogenesis and mitochondrial content. This review summarizes evidence to suggest caffeine-effects within skeletal muscle fibers, focusing on the putative role of caffeine on mitochondrial biogenesis to explore whether caffeine supplementation might be a strategy to enhance mitochondrial biogenesis.

Cross-talk between TRPC-1, mTOR, PGC-1α and PPARδ in the dystrophic muscle cells treated with tempol.

Background Ca2+ dysregulation and oxidative damage appear to have a central role in Duchenne muscular dystrophy (DMD) progression. The current study provides muscle cell-specific insights into the effect of Tempol on the TRPC 1 channel; on the positive and negative regulators of muscle cell differentiation; on the antioxidant enzymatic system; on the activators of mitochondrial biogenesis; and on the inflammatory process in the dystrophic primary muscle cells in culture. METHODS: Mdx myotubes were treated with Tempol (5 mM) for 24 h. Untreated mdx myotubes and C57BL/10 myotubes were used as controls. RESULTS: The Trypan Blue, MTT and Live/Dead Cell assays showed that Tempol (5 mM) presented no cytotoxic effect on the dystrophic muscle cells. The Tempol treated-mdx muscle cells showed significantly lower levels in the fluorescence intensity of intracellular calcium; TRPC-1 channel; MyoD; H2O2 and O2•- production; 4-HNE levels; SOD2, CAT and GPx levels; and TNF levels. On the other hand, SOD, CAT and GR mRNA relative expression were significantly higher in Tempol treated-mdx muscle cells. In addition, higher levels of Myogenin, MHC-Slow, mTOR, PGC-1α and PPARδ were also observed in Tempol treated-mdx muscle cells. CONCLUSION: Our findings demonstrated that Tempol decreased intracellular calcium and oxidative stress in primary dystrophic muscle cells, promoting a cross-talk between TRPC-1, mTOR, PGC-1α and PPARδ.

Fimasartan Ameliorates Deteriorations in Glucose Metabolism in a High Glucose State by Regulating Skeletal Muscle and Liver Cells.

PURPOSE: Since diabetes and hypertension frequently occur together, it is thought that these conditions may have a common pathogenesis. This study was designed to evaluate the anti-diabetic function of the anti-hypertensive drug fimasartan on C2C12 mouse skeletal muscle and HepG2 human liver cells in a high glucose state. MATERIALS AND METHODS: The anti-diabetic effects and mechanism of fimasartan were identified using Western blot, glucose uptake tests, oxygen consumption rate (OCR) analysis, adenosine 5'-triphosphate (ATP) enzyme-linked immunosorbent assay (ELISA), and immunofluorescence staining for diabetic biomarkers in C2C12 cells. Protein biomarkers for glycogenolysis and glycogenesis were evaluated by Western blotting and ELISA in HepG2 cells. RESULTS: The protein levels of phosphorylated 5' adenosine monophosphate-activated protein kinase (p-AMPK), p-AKT, insulin receptor substrate-1 (IRS-1), and glucose transporter type 4 (Glut4) were elevated in C2C12 cells treated with fimasartan. These increases were reversed by peroxisome proliferator-activated receptor delta (PPARδ) antagonist. ATP, OCR, and glucose uptake were increased in cells treated with 200 µM fimasartan. Protein levels of glycogen phosphorylase, glucose synthase, phosphorylated glycogen synthase, and glycogen synthase kinase-3 (GSK-3) were decreased in HepG2 cells treated with fimasartan. However, these effects were reversed following the addition of the PPARδ antagonist GSK0660. CONCLUSION: In conclusion, fimasartan ameliorates deteriorations in glucose metabolism as a result of a high glucose state by regulating PPARδ in skeletal muscle and liver cells.

Endothelial PPARδ facilitates the post-ischemic vascular repair through interaction with HIF1α.

Rationale: Restoration of vascular perfusion in peripheral arterial disease involves a combination of neovessel formation and the functional restoration of vascular endothelium. Previous studies indicated that ligand-dependent PPARδ activation enhances angiogenesis. However, how PPARδ is triggered by hypoxia and its downstream effects during post-ischemic vascular repair was not well understood. Methods: We induced experimental hindlimb ischemia in endothelial cell selective Ppard knockout induced by Cdh5-Cre mediated deletion of floxed Ppard allele in mice and their wild type control and observed blood perfusion, capillary density, vascular relaxation, and vascular leakage. Results: Deletion of endothelial Ppard delayed perfusion recovery and tissue repair, accompanied by delayed post-ischemic angiogenesis, impaired restoration of vascular integrity, more vascular leakage and enhanced inflammatory responses. At the molecular level, hypoxia upregulated and activated PPARδ in endothelial cells, whereas PPARδ reciprocally stabilized HIF1α protein to prevent its ubiquitin-mediated degradation. PPARδ directly bound to the oxygen-dependent degradation domain of HIF1α at the ligand-dependent domain of PPARδ. Importantly, this HIF1α-PPARδ interaction was independent of PPARδ ligand. Adeno-associated virus mediated endothelium-targeted overexpression of stable HIF1α in vivo improved perfusion recovery, suppressed vascular inflammation, and enhanced vascular repair, to counteract with the effect of Ppard knockout after hindlimb ischemia in mice. Conclusions: In summary, hypoxia-induced, ligand-independent activation of PPARδ in ECs stabilizes HIF1α and serves as a critical regulator for HIF1α activation to facilitate the post-ischemic restoration of vascular homeostasis.

Down-regulation of AMPK/PPARδ signalling promotes endoplasmic reticulum stress-induced endothelial dysfunction in adult rat offspring exposed to maternal diabetes.

AIMS: Exposure to maternal diabetes is associated with increased prevalence of hypertension in the offspring. The mechanisms underlying the prenatal programming of hypertension remain unclear. Because endoplasmic reticulum (ER) stress plays a key role in vascular endothelial dysfunction in hypertension, we investigated whether aberrant ER stress causes endothelial dysfunction and high blood pressure in the offspring of dams with diabetes. METHODS AND RESULTS: Pregnant Sprague-Dawley rats were intraperitoneally injected with streptozotocin (35 mg/kg) or citrate buffer at Day 0 of gestation. Compared with control mother offspring (CMO), the diabetic mother offspring (DMO) had higher blood pressure and impaired endothelium-dependent relaxation in mesenteric arteries, accompanied by decreased AMPK phosphorylation and PPARδ expression, increased ER stress markers, and reactive oxygen species (ROS) levels. The inhibition of ER stress reversed these aberrant changes in DMO. Ex vivo treatment of mesenteric arteries with an AMPK agonist (A769662) or a PPARδ agonist (GW1516) improved the impaired EDR in DMO and reversed the tunicamycin-induced ER stress, ROS production, and EDR impairment in mesenteric arteries from CMO. The effects of A769662 were abolished by co-treatment with GSK0660 (PPARδ antagonist), whereas the effects of GW1516 were unaffected by Compound C (AMPK inhibitor). CONCLUSION: These results suggest an abnormal foetal programming of vascular endothelial function in offspring of rats with maternal diabetes that is associated with increased ER stress, which can be ascribed to down-regulation of AMPK/PPARδ signalling cascade.

Gene Doping with Peroxisome-Proliferator-Activated Receptor Beta/Delta Agonists Alters Immunity but Exercise Training Mitigates the Detection of Effects in Blood Samples.

Synthetic ligands of peroxisome-proliferator-activated receptor beta/delta (PPARß/δ) are being used as performance-enhancing drugs by athletes. Since we previously showed that PPARß/δ activation affects T cell biology, we wanted to investigate whether a specific blood T cell signature could be employed as a method to detect the use of PPARß/δ agonists. We analyzed in primary human T cells the in vitro effect of PPARß/δ activation on fatty acid oxidation (FAO) and on their differentiation into regulatory T cells (Tregs). Furthermore, we conducted studies in mice assigned to groups according to an 8-week exercise training program and/or a 6-week treatment with 3 mg/kg/day of GW0742, a PPARß/δ agonist, in order to (1) determine the immune impact of the treatment on secondary lymphoid organs and to (2) validate a blood signature. Our results show that PPARß/δ activation increases FAO potential in human and mouse T cells and mouse secondary lymphoid organs. This was accompanied by increased Treg polarization of human primary T cells. Moreover, Treg prevalence in mouse lymph nodes was increased when PPARß/δ activation was combined with exercise training. Lastly, PPARß/δ activation increased FAO potential in mouse blood T cells. Unfortunately, this signature was masked by training in mice. In conclusion, beyond the fact that it is unlikely that this signature could be used as a doping-control strategy, our results suggest that the use of PPARß/δ agonists could have potential detrimental immune effects that may not be detectable in blood samples.

PPARδ attenuates hepatic steatosis through autophagy-mediated fatty acid oxidation.

Peroxisome proliferator-activated receptor δ (PPARδ) belongs to the nuclear receptor family and is involved in metabolic diseases. Although PPARδ is known to attenuate hepatic lipid deposition, its mechanism remains unclear. Here, we show that PPARδ is a potent stimulator of hepatic autophagic flux. The expression levels of PPARδ and autophagy-related proteins were decreased in liver tissues from obese and ageing mice. Pharmacological and adenovirus-mediated increases in PPARδ expression and activity were achieved in obese transgenic db/db and high fat diet-fed mice. Using genetic, pharmacological and metabolic approaches, we demonstrate that PPARδ reduces intrahepatic lipid content and stimulates ß-oxidation in liver and hepatic cells by an autophagy-lysosomal pathway involving AMPK/mTOR signalling. These results provide novel insight into the lipolytic actions of PPARδ through autophagy in the liver and highlight its potential beneficial effects in NAFLD.

PPARD is an Inhibitor of Cartilage Growth in External Ears.

Peroxisome proliferator-activated receptor beta/delta (PPARD) is an important determinant of multiple biological processes. Our previous studies identified a missense mutation in the PPARD gene that significantly reduces its transcription activity, and consequently causes enlarged external ears in pigs. However, the mechanisms underlying the causality has remained largely unknown. Here, we show that PPARD retards the development of auricular cartilage by accelerating the apoptosis of cartilage stem/progenitor cells (CSPCs), the terminal differentiation of cartilage cells and the degradation of cartilage extracellular matrix in the auricle. At the transcription level, PPARD upregulates a set of genes that are associated with CSPCs apoptosis and chondrogenic differentiation, chondroblast differentiation and extracellular matrix degradation. ChIP-seq identified direct target genes of PPARD, including a well-documented gene for cartilage development: PPARG. We further show that compared to wild-type PPARD, the G32E mutant up-regulates the expression of PPARG and subsequently leads to the downregulation of critical genes that inhibit cartilage growth. These findings allow us to conclude that PPARD is an inhibitor of auricular cartilage growth in pigs. The causative mutation (G32E) in the PPARD gene attenuates the PPARD-mediated retardation of cartilage growth in the auricle, contributing to enlarged ears in pigs. The findings advance our understanding of the mechanisms underlying auricular development in mammals, and shed insight into the studies of innate pinna disorders and cartilage regeneration medicine in humans.

PPAR-delta promotes survival of chronic lymphocytic leukemia cells in energetically unfavorable conditions.

Targeting the mechanisms that allow chronic lymphocytic leukemia (CLL) cells to survive in harsh cancer microenvironments should improve patient outcomes. The nuclear receptor peroxisome proliferator activated receptor delta (PPARδ) sustains other cancers, and in silico analysis showed higher PPARD expression in CLL cells than normal lymphocytes and other hematologic cancers. A direct association was found between PPARδ protein levels in CLL cells and clinical score. Transgenic expression of PPARδ increased the growth and survival of CD5+ Daudi cells and primary CLL cells in stressful conditions including exhausted tissue culture media, low extracellular glucose, hypoxia and exposure to cytotoxic drugs. Glucocorticoids and synthetic PPARδ agonists up-regulated PPARD expression and also protected Daudi and primary CLL cells from metabolic stressors. Survival in low glucose was related to increased antioxidant expression, substrate utilization and mitochondrial performance, and was reversed by genetic deletion and synthetic PPARδ antagonists. These findings suggest PPARδ conditions CLL cells to survive in harsh microenvironmental conditions by reducing oxidative stress and increasing metabolic efficiency. Targeting PPARδ may be beneficial in the treatment of CLL.

PPARδ reduces abdominal aortic aneurysm formation in angiotensin II-infused apolipoprotein E-deficient mice by regulating extracellular matrix homeostasis and inflammatory responses.

BACKGROUND: Abdominal aortic aneurysm (AAA) is an inflammatory disorder characterized by a localized degradation of connective tissue and apoptosis of vascular smooth muscle cells. This study examined whether the ligand-activated peroxisome proliferator-activated receptor (PPAR) δ can directly antagonize angiotensin II (Ang II)-induced AAA formation in apoE-deficient mice. METHODS AND RESULTS: Six-month-old male apoE-deficient mice were infused with Ang II and/or GW501516 (1.44 and 3.3mg/kg/day, respectively) via osmotic mini-pumps. At day 28, aortic size was measured and tissues were collected for analyses. Co-infusion of GW501516, an activator of PPARδ, attenuated both the incidence and the severity of Ang II-induced AAA in apoE-deficient mice. Ligand-activated PPARδ also reduced infiltration of macrophages, resulting in significant decreases in chemotactic proteins such as monocyte chemoattractant protein-1, macrophage inflammatory protein-1ß, and inducible nitric oxide synthase. The anti-inflammatory effect of GW501516 was associated with the suppression of apoptotic cell death, along with the inhibition of medial smooth muscle cell loss and focal elastin destruction, which leads to a medial dissection and aortic rupture. These ameliorative effects of GW501516 on Ang II-induced aneurysm were correlated with increased expression of extracellular matrix (ECM) proteins, such as types I and III collagen, fibronectin, and elastin, along with the up-regulation of transforming growth factor-ß1. In addition, ligand-activated PPARδ also increased the expression of tissue inhibitor of metalloproteinase (TIMP)-2 and TIMP-3, while it strongly suppressed that of matrix metalloproteinase-2. CONCLUSIONS: PPARδ attenuates Ang II-induced AAA formation by regulating ECM homeostasis and inflammatory responses, suggesting a novel strategy for the treatment of AAA.

PPARß/δ attenuates palmitate-induced endoplasmic reticulum stress and induces autophagic markers in human cardiac cells.

BACKGROUND: Chronic endoplasmic reticulum (ER) stress contributes to the apoptotic cell death in the myocardium, thereby playing a critical role in the development of cardiomyopathy. ER stress has been reported to be induced after high-fat diet feeding in mice and also after saturated fatty acid treatment in vitro. Therefore, since several studies have shown that peroxisome proliferator-activated receptor (PPAR)ß/δ inhibits ER stress, the main goal of this study consisted in investigating whether activation of this nuclear receptor was able to prevent lipid-induced ER stress in cardiac cells. METHODS AND RESULTS: Wild-type and transgenic mice with reduced PPARß/δ expression were fed a standard diet or a high-fat diet for two months. For in vitro studies, a cardiomyocyte cell line of human origin, AC16, was treated with palmitate and the PPARß/δ agonist GW501516. Our results demonstrate that palmitate induced ER stress in AC16 cells, a fact which was prevented after PPARß/δ activation with GW501516. Interestingly, the effect of GW501516 on ER stress occurred in an AMPK-independent manner. The most striking result of this study is that GW501516 treatment also upregulated the protein levels of beclin 1 and LC3II, two well-known markers of autophagy. In accordance with this, feeding on a high-fat diet or suppression of PPARß/δ in knockout mice induced ER stress in the heart. Moreover, PPARß/δ knockout mice also displayed a reduction in autophagic markers. CONCLUSION: Our data indicate that PPARß/δ activation might be useful to prevent the harmful effects of ER stress induced by saturated fatty acids in the heart by inducing autophagy.

Peroxisome proliferator-activated receptor delta and cardiovascular disease.

Recent reports have shown that peroxisome proliferator-activated receptor delta (PPARD) plays an important role in different vascular processes suggesting that PPARD is a significant modulator of cardiovascular disease. This review will focus on PPARD in relation to cardiovascular risk factors based on cell, animal and human data. Mouse studies suggest that Ppard is an important metabolic modulator that may have implications for cardiovascular disease (CVD). Specific human PPARD gene variants show no clear association with CVD but interactions between variants and lifestyle factors might influence disease risk. During recent years, development of specific and potent PPARD agonists has also made it possible to study the effects of PPARD activation in humans. PPARD agonists seem to exert beneficial effects on dyslipidemia and insulin-resistant syndromes but safety issues have been raised due to the role that PPARD plays in cell proliferation. Thus, large long term outcome as well as detailed safety and tolerability studies are needed to evaluate whether PPARD agonists could be used to treat CVD in humans.

[PPARs: physiological functions and pharmacological roles of agonists in human diseases. Note II]. / PPARs: functii fiziologice si roluri farmacologice ale agonistilor în bolile umane (Nota II).

Increasing attention paid to the main family of peroxisome proliferator activated receptors--PPARs is generated, on one hand by the multiple functions of its members in numerous metabolically active tissues, and on the other hand by the therapeutic benefits expresed by some specific ligands that are used in certain metabolic diseases treatment plan. PPARalpha stimulates the beta-oxidative degradation of fatty acids and controls plasma lipid transport through the mediated action upon the triglycerides and fatty acids metabolism and by modulation of biosynthesis and catabolism of bile acids in the liver. PPARgamma promotes adipocytes differentiation and fat storage. PPARbeta/delta is involved in control and management of adipogenesis. While PPARalpha mediates the hypolipemiant actions of fibrates, PPARgamma is the receptor for thiazolidinediones (glitazones) reccomended in type 2 diabetes treatment; by binding to PPARgamma, glitazones modulates transcription of genes involved in lipid and carbohydrate metabolism.