Activation of Peroxisome Proliferator-Activated Receptor-ß/δ (PPARß/δ) in Keratinocytes by Endogenous Fatty Acids.

Nuclear hormone receptors exist in dynamic equilibrium between transcriptionally active and inactive complexes dependent on interactions with ligands, proteins, and chromatin. The present studies examined the hypothesis that endogenous ligands activate peroxisome proliferator-activated receptor-ß/δ (PPARß/δ) in keratinocytes. The phorbol ester treatment or HRAS infection of primary keratinocytes increased fatty acids that were associated with enhanced PPARß/δ activity. Fatty acids caused PPARß/δ-dependent increases in chromatin occupancy and the expression of angiopoietin-like protein 4 (Angptl4) mRNA. Analyses demonstrated that stearoyl Co-A desaturase 1 (Scd1) mediates an increase in intracellular monounsaturated fatty acids in keratinocytes that act as PPARß/δ ligands. The activation of PPARß/δ with palmitoleic or oleic acid causes arrest at the G2/M phase of the cell cycle of HRAS-expressing keratinocytes that is not found in similarly treated HRAS-expressing Pparb/d-null keratinocytes. HRAS-expressing Scd1-null mouse keratinocytes exhibit enhanced cell proliferation, an effect that is mitigated by treatment with palmitoleic or oleic acid. Consistent with these findings, the ligand activation of PPARß/δ with GW0742 or oleic acid prevented UVB-induced non-melanoma skin carcinogenesis, an effect that required PPARß/δ. The results from these studies demonstrate that PPARß/δ has endogenous roles in keratinocytes and can be activated by lipids found in diet and cellular components.

Aster glehni Extract, Including Caffeoylquinic Acids as the Main Constituents, Induces PPAR ß/δ-Dependent Muscle-Type Change and Myogenesis in Apolipoprotein E Knockout Mice.

To probe the functions of Aster glehni (AG) extract containing various caffeoylquinic acids on dyslipidemia, obesity, and skeletal muscle-related diseases focused on the roles of skeletal muscle, we measured the levels of biomarkers involved in oxidative phosphorylation and type change of skeletal muscle in C2C12 cells and skeletal muscle tissues from apolipoprotein E knockout (ApoE KO) mice. After AG extract treatment in cell and animal experiments, western blotting, immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA) were used to estimate the levels of proteins that participated in skeletal muscle type change and oxidative phosphorylation. AG extract elevated protein expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), phosphorylated 5'-AMP-activated protein kinase (p-AMPK), peroxisome proliferator-activated receptor beta/delta (PPARß/δ), myoblast determination protein 1 (MyoD), and myoglobin in skeletal muscle tissues. Furthermore, it elevated the ATP concentration. However, protein expression of myostatin was decreased by AG treatment. In C2C12 cells, increments of MyoD, myoglobin, myosin, ATP-producing pathway, and differentiation degree by AG were dependent on PPARß/δ and caffeoylquinic acids. AG extract can contribute to the amelioration of skeletal muscle inactivity and sarcopenia through myogenesis in skeletal muscle tissues from ApoE KO mice, and function of AG extract may be dependent on PPARß/δ, and the main functional constituents of AG are trans-5-O-caffeoylquinic acid and 3,5-O-dicaffeoylquinic acid. In addition, in skeletal muscle, AG has potent efficacies against dyslipidemia and obesity through the increase of the type 1 muscle fiber content to produce more ATP by oxidative phosphorylation in skeletal muscle tissues from ApoE KO mice.

Pectolinarigenin ameliorates osteoporosis via enhancing Wnt signaling cascade in PPARß-dependent manner.

BACKGROUND: Osteoporosis is a prevalent metabolic bone disease in older adults. Peroxisome proliferator-activated receptor ß (PPARß), the most abundant PPAR isotype expressed in bone tissues, plays a critical role in regulating the energy metabolism of osteoblasts. However, the botanical compounds targeting PPARß for the treatment of osteoporosis remain largely unexplored. PURPOSE: To discover a potent PPARß agonist from botanical compounds, as well as to investigate the anti-osteoporosis effects and to elucidate the underlying mechanisms of the newly identified PPARß agonist. METHODS: The PPARß agonist effects of botanical compounds were screened by an in vitro luciferase reporter gene assay. The PPARß agonist effects of pectolinarigenin (PEC) in bone marrow mesenchymal stromal cells (BMSCs) were validated by Western blotting. RNA-seq transcriptome analyses were conducted to reveal the underlying osteoporosis mechanisms of PEC in BMSCs. The PPARß antagonist (GSK0660) and Wnt signaling inhibitor (XAV969) were used to explore the role of the PPARß and Wnt signaling cascade in the anti-osteoporosis effects of PEC. PEC or the PEG-PLGA nanoparticles of PEC (PEC-NP) were intraperitoneally administrated in both wild-type mice and ovariectomy-induced osteoporosis mice to examine its anti-osteoporotic effects in vivo. RESULTS: PEC, a newly identified naturally occurring PPARß agonist, significantly promotes osteogenic differentiation and up-regulates the osteogenic differentiation-related genes (Runx2, Osterix, and Bmp2) in BMSCs. RNA sequencing and functional gene enrichment analysis suggested that PEC could activate osteogenic-related signaling pathways, including Wnt and PPAR signaling pathways. Further investigations suggested that PEC could enhance Wnt/ß-catenin signaling in a PPARß-dependent manner in BMSCs. Animal tests showed that PEC-NP promoted bone mass and density, increased the bone cell matrix protein, and accelerated bone formation in wild-type mice, while PEC-NP also played a preventive role in ovariectomy-induced osteoporosis mice via maintaining the expression level of bone cell matrix protein, balancing the rate of bone formation, and slowing down bone loss. Additionally, PEC-NP did not cause any organ injury and body weight loss after long-term use (11 weeks). CONCLUSION: PEC significantly promotes bone formation and reduces bone loss in both BMSCs and ovariectomy-induced osteoporosis mice via enhancing the Wnt signaling cascade in a PPARß-dependent manner, providing a new alternative therapy for preventing estrogen deficiency-induced osteoporotic diseases.

PPARß/δ as a promising molecular drug target for liver diseases: A focused review.

Various liver diseases pose great threats to humans. Although the etiologies of these liver diseases are quite diverse, they share similar pathologic phenotypes and molecular mechanisms such as oxidative stress, lipid and glucose metabolism disturbance, hepatic Kupffer cell (KC) proinflammatory polarization and inflammation, insulin resistance, and hepatic stellate cell (HSC) activation and proliferation. Peroxisome proliferator-activated receptor ß/δ (PPARß/δ) is expressed in various types of liver cells with relatively higher expression in KCs and HSCs. Accumulating evidence has revealed the versatile functions of PPARß/δ such as controlling lipid homeostasis, inhibiting inflammation, regulating glucose metabolism, and restoring insulin sensitivity, suggesting that PPARß/δ may serve as a potential molecular drug target for various liver diseases. This article aims to provide a concise review of the structure, expression pattern and biological functions of PPARß/δ in the liver and its roles in various liver diseases, and to discuss potential future research perspectives.

Clinical Relevance of Differential RARα and PPARß/δ Expression in Myelodysplastic Syndromes.

BACKGROUND/AIM: Myelodysplastic syndromes (MDS) are clinically heterogeneous hematological malignancies with an increased risk of transformation to acute myeloid leukemia, emphasizing the importance of identifying new diagnostic and prognostic markers. This study sought to investigate the predictive ability of all-trans retinoic acid (ATRA)-dependent nuclear transcription factors RARα and PPARß/δ gene expression in MDS patients. MATERIALS AND METHODS: Peripheral blood specimens were collected from 49 MDS patients and 15 healthy volunteers. The specimens were further separated in Ficoll density gradient to obtain the mononuclear cells fractions. Gene expression analysis was carried out using quantitative real-time polymerase chain reaction (qRT-PCR) technique. RESULTS: In the mononuclear cell fractions of MDS patients, RARα expression was increased (p<0.05) and PPARß/δ expression was decreased (p<0.01) compared to healthy volunteers. When RARα and PPARß/δ expression was compared in groups of MDS patients with different risks of disease progression, no statistically significant difference was found for RARα expression, while PPARß/δ expression was significantly lower in the high-risk group of patients compared to the low-risk group (p<0.05). The expression of RARα was significantly associated with overall survival (p<0.05). ROC analysis showed that the expression of PPARß/δ, rather than RARα expression, could have potential diagnostic value for MDS patients (AUC=0.75, p=0.003 and AUC=0.65, p=0.081, respectively). CONCLUSION: RARα and PPARß/δ genes are putative biomarkers that may be associated with the diagnosis and prognosis of MDS.

GW0742 reduces mast cells degranulation and attenuates neurological impairments via PPARß/δ/CD300a/SHP1 pathway after GMH in neonatal rats.

BACKGROUND: Activation of mast cells plays an important role in brain inflammation. CD300a, an inhibitory receptor located on mast cell surfaces, has been reported to reduce the production of pro-inflammatory cytokines and exert protective effects in inflammation-related diseases. Peroxisome proliferator-activated receptor ß/δ (PPARß/δ), a ligand-activated nuclear receptor, activation upregulates the transcription of CD300a. In this study, we aim to investigate the role of PPARß/δ in the attenuation of germinal matrix hemorrhage (GMH)-induced mast cell activation via CD300a/SHP1 pathway. METHODS: GMH model was induced by intraparenchymal injection of bacterial collagenase into the right hemispheric ganglionic eminence in P7 Sprague Dawley rats. GW0742, a PPARß/δ agonist, was administered intranasally at 1 h post-ictus. CD300a small interfering RNA (siRNA) and PPARß/δ siRNA were injected intracerebroventricularly 5 days and 2 days before GMH induction. Behavioral tests, Western blot, immunofluorescence, Toluidine Blue staining, and Nissl staining were applied to assess post-GMH evaluation. RESULTS: Results demonstrated that endogenous protein levels of PPARß/δ and CD300a were decreased, whereas chymase, tryptase, IL-17A and transforming growth factor ß1 (TGF-ß1) were elevated after GMH. GMH induced significant short- and long-term neurobehavioral deficits in rat pups. GW0742 decreased mast cell degranulation, improved neurological outcomes, and attenuated ventriculomegaly after GMH. Additionally, GW0742 increased expression of PPARß/δ, CD300a and phosphorylation of SHP1, decreased phosphorylation of Syk, chymase, tryptase, IL-17A and TGF-ß1 levels. PPARß/δ siRNA and CD300a siRNA abolished the beneficial effects of GW0742. CONCLUSIONS: GW0742 inhibited mast cell-induced inflammation and improved neurobehavior after GMH, which is mediated by PPARß/δ/CD300a/SHP1 pathway. GW0742 may serve as a potential treatment to reduce brain injury for GMH patients.

PPARß/δ-ANGPTL4 axis mediates the promotion of mono-2-ethylhexyl phthalic acid on MYCN-amplified neuroblastoma development.

Di-2-ethylhexyl phthalic acid (DEHP) is one of the most widely used plasticizers in the industry, which can improve the flexibility and durability of plastics. It is prone to migrate from various daily plastic products through wear and leaching into the surrounding environment and decompose into the more toxic metabolite mono-2-ethylhexyl phthalic acid (MEHP) after entering the human body. However, the impacts and mechanisms of MEHP on neuroblastoma are unclear. We exposed MYCN-amplified neuroblastoma SK-N-BE(2)C cells to an environmentally related concentration of MEHP and found that MEHP increased the proliferation and migration ability of tumor cells. The peroxisome proliferator-activated receptor (PPAR) ß/δ pathway was identified as a pivotal signaling pathway in neuroblastoma, mediating the effects of MEHP through transcriptional sequencing analysis. Because MEHP can bind to the PPARß/δ protein and initiate the expression of the downstream gene angiopoietin-like 4 (ANGPTL4), the PPARß/δ-specific agonist GW501516 and antagonist GSK3787, the recombinant human ANGPTL4 protein, and the knockdown of gene expression confirmed the regulation of the PPARß/δ-ANGPTL4 axis on the malignant phenotype of neuroblastoma. Based on the critical role of PPARß/δ and ANGPTL4 in the metabolic process, a non-targeted metabolomics analysis revealed that MEHP altered multiple metabolic pathways, particularly lipid metabolites involving fatty acyls, glycerophospholipids, and sterol lipids, which may also be potential factors promoting tumor progression. We have demonstrated for the first time that MEHP can target binding to PPARß/δ and affect the progression of neuroblastoma by activating the PPARß/δ-ANGPTL4 axis. This mechanism confirms the health risks of plasticizers as tumor promoters and provides new data support for targeted prevention and treatment of neuroblastoma.

Elafibranor upregulates the EMT-inducer S100A4 via PPARß/δ.

Elafibranor is a dual peroxisome proliferator-activated receptor (PPAR)α and ß/δ agonist that has reached a phase III clinical trial for the treatment of metabolic dysfunction-associated steatotic liver disease (MASLD). Here, we examined the effects of elafibranor in mice fed a choline-deficient high-fat diet (CD-HFD), a model of metabolic dysfunction-associated steatohepatitis (MASH) that presents obesity and insulin resistance. Our findings revealed that elafibranor treatment ameliorated steatosis, inflammation, and fibrogenesis in the livers of CD-HFD-fed mice. Unexpectedly, elafibranor also increased the levels of the epithelial-mesenchymal transition (EMT)-promoting protein S100A4 via PPARß/δ activation. The increase in S100A4 protein levels caused by elafibranor was accompanied by changes in the levels of markers associated with the EMT program. The S100A4 induction caused by elafibranor was confirmed in the BRL-3A rat liver cells and a mouse primary hepatocyte culture. Furthermore, elafibranor reduced the levels of ASB2, a protein that promotes S100A4 degradation, while ASB2 overexpression prevented the stimulating effect of elafibranor on S100A4. Collectively, these findings reveal an unexpected hepatic effect of elafibranor on increasing S100A4 and promoting the EMT program.

PPARß/δ activation protects against hepatic ischaemia-reperfusion injury.

BACKGROUND AND AIMS: Hepatic ischaemia/reperfusion injury (HIRI) is a pathophysiological process that occurs during the liver resection and transplantation. Reportedly, peroxisome proliferator-activated receptor ß/δ (PPARß/δ) can ameliorate kidney and myocardial ischaemia/reperfusion injury. However, the effect of PPARß/δ in HIRI remains unclear. METHODS: Mouse hepatic ischaemia/reperfusion (I/R) models were constructed for in vivo study. Primary hepatocytes and Kupffer cells (KCs) isolated from mice and cell anoxia/reoxygenation (A/R) injury model were constructed for in vitro study. Liver injury and inflammation were investigated. Small molecular compounds (GW0742 and GSK0660) and adenoviruses were used to interfere with PPARß/δ. RESULTS: We found that PPARß/δ expression was increased in the I/R and A/R models. Overexpression of PPARß/δ in hepatocytes alleviated A/R-induced cell apoptosis, while knockdown of PPARß/δ in hepatocytes aggravated A/R injury. Activation of PPARß/δ by GW0742 protected against I/R-induced liver damage, inflammation and cell death, whereas inhibition of PPARß/δ by GSK0660 had the opposite effects. Consistent results were obtained in mouse I/R models through the tail vein injection of adenovirus-mediated PPARß/δ overexpression or knockdown vectors. Furthermore, knockdown and overexpression of PPARß/δ in KCs aggravated and ameliorated A/R-induced hepatocyte injury, respectively. Gene ontology and gene set enrichment analysis showed that PPARß/δ deletion was significantly enriched in the NF-κB pathway. PPARß/δ inhibited the expression of p-IKBα and p-P65 and decreased NF-κB activity. CONCLUSIONS: PPARß/δ exerts anti-inflammatory and anti-apoptotic effects on HIRI by inhibiting the NF-κB pathway, and hepatocytes and KCs may play a synergistic role in this phenomenon. Thus, PPARß/δ is a potential therapeutic target for HIRI.

Medium-chain fatty acids modify macrophage expression of metabolic and inflammatory genes in a PPAR ß/δ-dependent manner.

There is great interest on medium chain fatty acids (MCFA) for cardiovascular health. We explored the effects of MCFA on the expression of lipid metabolism and inflammatory genes in macrophages, and the extent to which they were mediated by the nuclear receptor peroxisome proliferator-activated receptor beta/delta (PPAR ß/δ). J774A.1 murine macrophages were exposed to octanoate or decanoate as MCFA, a long-chain fatty acid control (palmitate), or the PPAR ß/δ agonist GW501516, with or without lipopolysaccharide (LPS) stimulation, and with or without an siRNA-induced knockdown of PPAR ß/δ. MCFA increased the expression of Plin2, encoding a lipid-droplet associated protein with anti-inflammatory effects in macrophages, in a partially PPAR ß/δ-dependent manner. Both MCFA stimulated expression of the cholesterol efflux pump ABCA1, more pronouncedly under LPS stimulation and in the absence of PPAR ß/δ. Octanoate stimulated the expression of Pltp, encoding a phospholipid transfer protein that aids ABCA1 in cellular lipid efflux. Only palmitate increased expression of the proinflammatory genes Il6, Tnf, Nos2 and Mmp9. Non-stimulated macrophages exposed to MCFA showed less internalization of fluorescently labeled lipoproteins. MCFA influenced the transcriptional responses of macrophages favoring cholesterol efflux and a less inflammatory response compared to palmitate. These effects were partially mediated by PPAR ß/δ.

Sinomenine alleviates lipopolysaccharide-induced acute lung injury via a PPARß/δ-dependent mechanism.

Evidence is mounting that sinomenine and peroxisome proliferator-activated receptor ß/δ (PPARß/δ) are effective against lipopolysaccharide (LPS)-induced acute lung injury (ALI) via anti-inflammatory properties. However, it is unknown whether PPARß/δ plays a role in the protective effect of sinomenine on ALI. Here, we initially observed that preemptive administration of sinomenine markedly alleviated lung pathological changes, pulmonary edema and neutrophil infiltration, accompanied by inhibition of the expression of the pro-inflammatory cytokines Tumor necrosis factor-α (TNF-α) and Interleukin-6 (IL-6), which were largely reversed following the addition of a PPARß/δ antagonist. Subsequently, we also noticed that sinomenine upregulated adenosine A2A receptor expression in a PPARß/δ-dependent manner in LPS-stimulated bone marrow-derived macrophages (BMDMs). Further investigation indicated that PPARß/δ directly bound to the functional peroxisome proliferator responsive element (PPRE) in the adenosine A2A receptor gene promoter region to enhance the expression of the adenosine A2A receptor. Sinomenine was identified as a PPARß/δ agonist. It could bind with PPARß/δ, and promote the nuclear translocation and transcriptional activity of PPARß/δ. In addition, combined treatment with sinomenine and an adenosine A2A receptor agonist exhibited synergistic effects and better protective roles than their single use against ALI. Taken together, our results reveal that sinomenine exerts advantageous effects on ALI by activating of PPARß/δ, with the subsequent upregulation of adenosine A2A receptor expression, and provide a novel and potential therapeutic application for ALI.

Unraveling the Role of Peroxisome Proliferator-Activated Receptor ß/Δ (PPAR ß/Δ) in Angiogenesis Associated with Multiple Myeloma.

Growing evidence suggests a role for peroxisome proliferator-activated receptor ß/δ (PPAR ß/δ) in the angiogenesis, growth, and metastasis of solid tumors, but little is known about its role in multiple myeloma (MM). Angiogenesis in the bone marrow (BM) is characteristic of disease transition from monoclonal gammopathy of undetermined significance (MGUS) to MM. We examined the expression and function of PPAR ß/δ in endothelial cells (EC) from the BM of MGUS (MGEC) and MM (MMEC) patients and showed that PPAR ß/δ was expressed at higher levels in MMEC than in MGEC and that the overexpression depended on myeloma plasma cells. The interaction between myeloma plasma cells and MMEC promoted the release of the PPAR ß/δ ligand prostaglandin I2 (PGI2) by MMEC, leading to the activation of PPAR ß/δ. We also demonstrated that PPAR ß/δ was a strong stimulator of angiogenesis in vitro and that PPAR ß/δ inhibition by a specific antagonist greatly impaired the angiogenic functions of MMEC. These findings define PGI2-PPAR ß/δ signaling in EC as a potential target of anti-angiogenic therapy. They also sustain the use of PPAR ß/δ inhibitors in association with conventional drugs as a new therapeutic approach in MM.

Gastrodin protects endothelial cells against high glucose-induced injury through up-regulation of PPARß and alleviation of nitrative stress.

In diabetes mellitus (DM), high glucose can result in endothelial cell injury, and then lead to diabetic vascular complications. Gastrodin, as the mainly components of Chinese traditional herb Tianma (Gastrodia elata Bl.), has been widely used for cardiovascular diseases. However, the known of the effect of gastrodin on endothelial cell injury is still limited. In this study, we aimed to investigate the effect and possible mechanism of gastrodin on high glucose-injured human umbilical vein endothelial cells (HUVEC). High glucose (30 mmol/L) treatment caused HUVEC injury. After gastrodin (0.1, 1, 10 µmol/L) treatment, compared with the high glucose group, the cell proliferation ability increased in a dose-dependent manner. Meanwhile, gastrodin (10 µmol/L) up-regulated the mRNA and protein expressions of PPARß and eNOS, decreased the expressions of iNOS, also reduced the protein expression of 3-nitrotyrosine, and lowed the level of ONOO-, increased NO content. Both the PPARß antagonist GSK0660 (1 µmol/L) and the eNOS inhibitor L-NAME (10 µmol/L) were able to block the above effects of gastrodin. In conclusion, gastrodin protectes vascular endothelial cells from high glucose injury, which may be, at least partly, mediated by up-regulating the expression of PPARß and negatively regulating nitrative stress.

PPARß/δ Ligands Regulate Oxidative Status and Inflammatory Response in Inflamed Corpus Luteum-An In Vitro Study.

Inflammation in the female reproductive system causes serious health problems including infertility. The aim of this study was to determine the in vitro effects of peroxisome proliferator-activated receptor-beta/delta (PPARß/δ) ligands on the transcriptomic profile of the lipopolysaccharide (LPS)-stimulated pig corpus luteum (CL) in the mid-luteal phase of the estrous cycle using RNA-seq technology. The CL slices were incubated in the presence of LPS or in combination with LPS and the PPARß/δ agonist-GW0724 (1 µmol/L or 10 µmol/L) or the antagonist-GSK3787 (25 µmol/L). We identified 117 differentially expressed genes after treatment with LPS; 102 and 97 differentially expressed genes after treatment, respectively, with the PPARß/δ agonist at a concentration of 1 µmol/L or 10 µmol/L, as well as 88 after the treatment with the PPARß/δ antagonist. In addition, biochemical analyses of oxidative status were performed (total antioxidant capacity and activity of peroxidase, catalase, superoxide dismutase, and glutathione S-transferase). This study revealed that PPARß/δ agonists regulate genes involved in the inflammatory response in a dose-dependent manner. The results indicate that the lower dose of GW0724 showed an anti-inflammatory character, while the higher dose seems to be pro-inflammatory. We propose that GW0724 should be considered for further research to alleviate chronic inflammation (at the lower dose) or to support the natural immune response against pathogens (at the higher dose) in the inflamed corpus luteum.

Anti-inflammatory effects and improved metabolic derangements in ob/ob mice by a newly synthesized prenylated benzopyran with pan-PPAR activity.

BACKGROUND AND PURPOSE: Selective peroxisome proliferator-activated receptors (PPARs) are widely used to treat metabolic complications; however, the limited effect of PPARα agonists on glucose metabolism and the adverse effects associated with selective PPARγ activators have stimulated the development of novel pan-PPAR agonists to treat metabolic disorders. Here, we synthesized a new prenylated benzopyran (BP-2) and evaluated its PPAR-activating properties, anti-inflammatory effects and impact on metabolic derangements. EXPERIMENTAL APPROACH: BP-2 was used in transactivation assays to evaluate its agonism to PPARα, PPARß/δ and PPARγ. A parallel-plate flow chamber was employed to investigate its effect on TNFα-induced leukocyte-endothelium interactions. Flow cytometry and immunofluorescence were used to determine its effects on the expression of endothelial cell adhesion molecules (CAMs) and chemokines and p38-MAPK/NF-κB activation. PPARs/RXRα interactions were determined using a gene silencing approach. Analysis of its impact on metabolic abnormalities and inflammation was performed in ob/ob mice. KEY RESULTS: BP-2 displayed strong PPARα activity, with moderate and weak activity against PPARß/δ and PPARγ, respectively. In vitro, BP-2 reduced TNFα-induced endothelial ICAM-1, VCAM-1 and fractalkine/CX3CL1 expression, suppressed mononuclear cell arrest via PPARß/δ-RXRα interactions and decreased p38-MAPK/NF-κB activation. In vivo, BP-2 improved the circulating levels of glucose and triglycerides in ob/ob mice, suppressed T-lymphocyte/macrophage infiltration and proinflammatory markers in the liver and white adipose tissue, but increased the expression of the M2-like macrophage marker CD206. CONCLUSION AND IMPLICATIONS: BP-2 emerges as a novel pan-PPAR lead candidate to normalize glycemia/triglyceridemia and minimize inflammation in metabolic disorders, likely preventing the development of further cardiovascular complications.

VLDL-VLDLR axis facilitates brown fat thermogenesis through replenishment of lipid fuels and PPARß/δ activation.

In mammals, brown adipose tissue (BAT) is specialized to conduct non-shivering thermogenesis for survival under cold acclimation. Although emerging evidence suggests that lipid metabolites are essential for heat generation in cold-activated BAT, the underlying mechanisms of lipid uptake in BAT have not been thoroughly understood. Here, we show that very-low-density lipoprotein (VLDL) uptaken by VLDL receptor (VLDLR) plays important roles in thermogenic execution in BAT. Compared with wild-type mice, VLDLR knockout mice exhibit impaired thermogenic features. Mechanistically, VLDLR-mediated VLDL uptake provides energy sources for mitochondrial oxidation via lysosomal processing, subsequently enhancing thermogenic activity in brown adipocytes. Moreover, the VLDL-VLDLR axis potentiates peroxisome proliferator activated receptor (PPAR)ß/δ activity with thermogenic gene expression in BAT. Accordingly, VLDL-induced thermogenic capacity is attenuated in brown-adipocyte-specific PPARß/δ knockout mice. Collectively, these data suggest that the VLDL-VLDLR axis in brown adipocytes is a key factor for thermogenic execution during cold exposure.

[Mechanism of nerve growth factor promotes angiogenesis and skeletal muscle fiber remodeling in a mouse hindlimb ischemic model].

Objective: To explore the mechanism of nerve growth factor (NGF) in the skeletal muscle fiber remodeling in ischemic limbs during therapeutic angiogenesis. Methods: Eighteen female mice with SPF grade, 6 weeks old and 25-30 g weighed were randomly allocated to sham-operated group (n=6), blank control group (n=6) and NGF gene transfection group (n=6). The left hindlimb ischemia models were established by ligating the femoral artery in blank control group and NGF gene transfection group. Seven days after the operation, mice in the three groups were separately injected with normal saline, empty plasmids, and NGF plasmids. Gastrocnemius of left hindlimbs was harvested after the blood perfusion assessment of the ischemic limb on the 21st postoperative day. The gastrocnemius muscle specimens were stained with HE, CD31 and proliferating cell nuclear antigen (PCNA) immunohistochemistry staining, the mRNA expressions of myosin heavy chain-Ⅰ(MHC-Ⅰ), MHC-Ⅱa and MHC-Ⅱb were measured by real-time PCR, and the protein level of NGF and peroxisome proliferator-activated receptors-ß/δ (PPAR ß/δ) were detected by Western blot. The expression of cytochrome C oxidase (COX), isocitrate dehydrogenase (IDH) and adenosine triphosphate (ATP) were examined by enzyme-linked immunosorbent assay (ELISA). Results: On the 21st day after operation, the blood perfusion of the ischemic limb in NGF gene transfection group was (195.70±9.99)PU, which was lower than that in sham-operated group (312.15±17.32)PU (P=0.001), while it was higher than that in blank control group (82.11±8.55)PU (P=0.001). The degree of muscle atrophy in the NGF gene transfection group was lower than that in the blank control group. The capillary density of NGF gene transfection group (0.34±0.05) was higher than that of sham-operated group (0.11±0.03) and blank control group (0.27±0.04) (P<0.05). The endothelial cell proliferation index in NGF gene transfection group (0.39±0.19) was significantly higher than that in sham-operated group (0.18±0.01) and blank control group (0.25±0.14) (P<0.05). The expression of NGF, PPAR ß/δ, COX, IDH, ATP, and MHC-Ⅰ mRNA in NGF gene transfection group were significantly higher than those in sham-operated group and blank control group (P<0.05). Conclusions: NGF gene transfection can promote angiogenesis in the ischemic limbs of mice, increase the blood perfusion, and thus induce the remodeling of skeletal muscle fibers to type Ⅰ. This process may be related to NGF-induced PPAR ß/δ expression and promote the cellular aerobic metabolism in skeletal muscle.

Cannabidiolic acid activates the expression of the PPARß/δ target genes in MDA-MB-231 cells.

Cannabidiolic acid (CBDA) can activate peroxisome proliferator-activated receptor-α (PPARα) and PPARγ. Whether CBDA can activate PPARß/δ has not been examined sufficiently to date. Since previous studies showed that triple-negative breast cancer cells respond to activation of PPARß/δ, the present study examined the effect of CBDA in MDA-MB-231 cells and compared the activities of CBDA with known PPARß/δ agonists/antagonists. Expression of the PPARß/δ target genes angiopoietin-like 4 (ANGPTL4) and adipocyte differentiation-related protein (ADRP) was increased by CBDA. Interestingly, ligand activation of PPARß/δ with GW501516 caused an increase in expression of both ANGPTL4 and ADRP, but the magnitude of this effect was markedly increased when co-treated with CBDA. Specificity of these effects were confirmed by showing that CBDA-induced expression of ANGPTL4 and ADRP is mitigated in the presence of either a PPARß/δ antagonist or an inverse agonist. Results from these studies suggest that CBDA can synergize with PPARß/δ and might interact with endogenous agonists that modulate PPARß/δ function.

Grape seed extract supplementation modulates hepatic lipid metabolism in rats. Implication of PPARß/δ.

In mammals, the liver is involved in nutrient metabolism and in the regulation of lipid and glucose homeostasis. Multiple studies have described improvements in liver disorders after regular consumption of grape seed extract (GSE). GSE prevents or ameliorates hepatic metabolic dysfunction through AMPK activation, which reduces hepatic lipogenesis while enhancing hepatic lipid oxidation. However, the involvement of ChREBPß and PPARß/δ in these effects has not been fully elucidated. We aim to demonstrate that chronic consumption of GSE at low doses (25 mg kg-1 body weight per day) produces beneficial effects on hepatic glucose and lipid metabolism in young lean Wistar rats and that part of these effects involve ChREBPß inactivation and PPARß/δ activation. In our study, increased concentrations of structurally related (-)-(epi)catechin metabolites and 5-carbon ring fission metabolites were found in the serum of GSE-supplemented rats parallel with the reduction in triglycerides and leptin levels, hepatic cholesterol content and visceral adiposity. GSE supplementation inactivates ChREBP and GSK-3ß, which has been linked to improvements in hepatic lipid and glucose metabolism. Furthermore, the consumption of GSE promotes the expression of Pparß/δ, as well as Pgc-1α and Acox-1, which control hepatic lipid oxidation. Interestingly, pharmacological inhibition of PPARß/δ slowed the induction of Pgc-1α and Acox-1, as well as the activation of AMPK triggered by GSE consumption. Our data suggest that PPARß/δ activation is involved in the metabolic reprogramming effects of chronic GSE consumption in young rats, by modulating, at least, part of the transcriptional programs that maintain hepatic and systemic fuel homeostasis.

Genetic Mechanism of Tissue-Specific Expression of PPAR Genes in Turbot (Scophthalmus maximus) at Different Temperatures.

In this study, we used PCR to measure the levels of the peroxisome proliferator activated receptor genes PPARα1, PPARα2, PPARß, and PPARγ in the intestine, liver, gill, heart, kidney, brain, muscle, spleen, skin, and stomach of turbot (Scophthalmus maximus) cultured under different temperature conditions (14, 20, 23, 25, and 28 °C). We used split-split-plot (SSP) analysis of variance, additive main effects and multiplicative interaction (AMMI) analysis, and genotype main effects and genotype × environment interaction (GGE) biplot analysis to evaluate the genotype × tissue interaction effects on gene expression. The results of the SSP analysis of variance showed that temperature and tissue × gene have highly significant (p < 0.01) effect on the expression of S. maximus PPAR genes. The AMMI analysis results revealed that the expression of PPAR genes at the appropriate temperature (14 °C) mainly depended on genotype × tissue interaction and tissue effects. Under stress temperatures, genotype effects, tissue effects, and genotype × tissue interaction, all had significant effects on the expression of PPAR genes. The contribution of the genotype effect slowly increased with increasing temperature; it increased faster at 20 °C and then slowly declined at 25 °C. The contribution of the tissue effect slowly increased from 14 to 20 °C, where it sharply decreased, and then it stabilized after a slight fluctuation. The contribution of the genotype × tissue interaction effect showed a fluctuating upward trend throughout the experiment, and it had a significant impact on PPAR gene expression. The key temperature at which the three effects changed was 20 °C, indicating that it is the limit temperature for active lipid metabolism under high-temperature stress. The GGE biplot analysis results showed that under suitable water temperature, the expression difference of PPAR genes in the liver was the largest; at 20 and 23 °C, the expression difference in the gill was the largest; and at 25 and 28 °C, the expression difference in the brain was the largest. Overall, our results suggest that the mechanism responsible for PPAR gene expression under the three high temperatures (23, 25, and 28 °C) was relatively consistent, but it differed from that at 20 °C.