PPARα Activation Research Articles

MiR-21-5p promotes NASH-related hepatocarcinogenesis.

The mechanisms governing the progression of non-alcoholic fatty liver disease (NAFLD) towards steatohepatitis (NASH) and hepatocellular carcinoma (HCC) remain elusive. Here, we evaluated the role of hsa-miRNA-21-5p in NASH-related hepatocarcinogenesis. Hepatic hsa-miR-21-5p expression was evaluated in two cohorts of patients with biopsy-proven NAFLD (n = 199) or HCC (n = 366 HCC and n = 11 NAFLD-HCC). Serum/liver metabolomic profiles were correlated with hsa-miR-21-5p in NAFLD obese patients. Wild-type (WT) and Mir21 KO mice were fed a choline-deficient, amino acid-defined (CDAA) diet for 32 and 66 weeks to induce NASH and NASH-HCC, respectively. In obese individuals, hsa-miR-21-5p expression increased with NAFLD severity and associated with a hepatic lipotoxic profile. CDAA-fed WT mice displayed increased hepatic mmu-miR-21-5p levels and progressively developed NASH and fibrosis, with livers presenting macroscopically discernible pre-neoplastic nodules, hyperplastic foci and deregulated cancer-related pathways. Mir21 KO mice exhibited peroxisome-proliferator-activated receptor α (PPARα) activation, augmented mitochondrial activity, reduced liver injury and NAS below the threshold for NASH diagnosis, with the pro-inflammatory/fibrogenic milieu reversing to baseline levels. In parallel, Mir21 KO mice displayed reduced number of pre-neoplastic nodules, hepatocyte proliferation and activation of oncogenic signalling, being protected from NASH-associated carcinogenesis. The hsa-miRNA-21-5p/PPARα pathway was similarly deregulated in patients with HCC- or NASH-related HCC, correlating with HCC markers and worse prognosis. Hsa-miR-21-5p is a key inducer of whole-spectrum NAFLD progression, from simple steatosis to NASH and NASH-associated carcinogenesis. The inhibition of hsa-miR-21-5p, leading to a pro-metabolic profile, might constitute an appealing therapeutic approach to ameliorate NASH and prevent progression towards HCC.

PPARα/ACOX1 as a novel target for hepatic lipid metabolism disorders induced by per- and polyfluoroalkyl substances: An integrated approach

BackgroundPer- and polyfluoroalkyl substances (PFAS) are persistent and ubiquitous environmental contaminants with well-documented hepatotoxicity. However, the mechanistic linkage between PFAS exposure and non-alcoholic fatty liver disease (NAFLD) remains largely elusive. ObjectivesThis study aimed to explore PFAS-to-NAFLD link and the relevant molecular mechanisms. MethodsThe cross-sectional analyses using National Health and Nutrition Examination Survey (NHANES) data were conducted to investigate the association between PFAS exposure and NAFLD. A combination of in silico toxicological analyses, bioinformatics approaches, animal experiments, and in vitro assays was used to explore the molecular initiating events (MIEs) and key events (KEs) in PFAS-induced hepatic lipid metabolism disorders. ResultsThe cross-sectional analyses with NHANES data revealed the significant association between PFAS exposure and hepatic steatosis/NAFLD. The in silico toxicological analyses showed that PPARα activation induced by perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), prototypical representatives of PFAS, is the critical MIE associated with NAFLD-predominant liver diseases. Transcriptome-based bioinformatic annotation and analyses identified that transcriptional upregulation of hepatic acyl-CoA oxidase 1 (ACOX1) in PPARα-regulated peroxisomal β-oxidation pathway was the KE involved with PFOA/PFOS-perturbed hepatic lipid metabolic pathways in humans, mice and rats. The in vivo and in vitro assays further verified that ACOX1-mediated oxidative stress contributed to mitochondrial compromise and lipid accumulation in PFOA/PFOS-exposed mouse hepatocytes, which could be mitigated by co-treatment with ACOX1 inhibitor and mitochondria ROS scavenger. Additionally, we observed that besides PFOA and PFOS, hepatic ACOX1 exhibited good-fit response to short-term exposures of long-chain (C7-C10) perfluoroalkyl carboxylic acids (PFHpA, PFNA, PFDA) and perfluoroalkyl sulfonic acids (PFHpS, PFDS) in human hepatocyte spheroids through benchmark dose (BMD) modeling. ConclusionOur study unveils a novel molecular target for PFAS-induced hepatic lipid metabolic disorders, shedding new light on prediction, assessment, and mitigation of PFAS hepatotoxicity.

PPARγ-dependent hepatic macrophage switching acts as a central hub for hUCMSC-mediated alleviation of decompensated liver cirrhosis in rats

BackgroundDecompensated liver cirrhosis (DLC), a terminal-stage complication of liver disease, is a major cause of morbidity and mortality in patients with hepatopathies. Human umbilical cord mesenchymal stem cell (hUCMSC) therapy has emerged as a novel treatment alternative for the treatment of DLC. However, optimized therapy protocols and the associated mechanisms are not entirely understood.MethodsWe constructed a DLC rat model consistent with the typical clinical characteristics combined use of PB and CCL4. Performing dynamic detection of liver morphology and function in rats for 11 weeks, various disease characteristics of DLC and the therapeutic effect of hUCMSCs on DLC in experimental rats were thoroughly investigated, according to ascites examination, histopathological, and related blood biochemical analyses. Flow cytometry analysis of rat liver, immunofluorescence, and RT-qPCR was performed to examine the changes in the liver immune microenvironment after hucMSCs treatment. We performed RNA-seq analysis of liver and primary macrophages and hUCMSCs co-culture system in vitro to explore possible signaling pathways. PPARγ antagonist, GW9662, and clodronate liposomes were used to inhibit PPAR activation and pre-exhaustion of macrophages in DLC rats’ livers, respectively.ResultsWe found that changing the two key issues, the frequency and initial phase of hUCMSCs infusion, can affect the efficacy of hUCMSCs, and the optimal hUCMSCs treatment schedule is once every week for three weeks at the early stage of DLC progression, providing the best therapeutic effect in reducing mortality and ascites, and improving liver function in DLC rats. hUCMSCs treatment skewed the macrophage phenotype from M1-type to M2-type by activating the PPARγ signaling pathway in the liver, which was approved by primary macrophages and hUCMSCs co-culture system in vitro. Both inhibition of PPARγ activation with GW9662 and pre-exhaustion of macrophages in DLC rats’ liver abolished the regulation of hUCMSCs on macrophage polarization, thus attenuating the beneficial effect of hUCMSCs treatment in DLC rats.ConclusionsThese data demonstrated that the optimal hUCMSCs treatment effectively inhibits the ascites formation, prolongs survival and significantly improves liver structure and function in DLC rats through the activation of the PPARγ signaling pathway within liver macrophages. Our study compared the efficacy of different hUCMSCs infusion regimens for DLC, providing new insights on cell-based therapies for regenerative medicine.

Established and Emerging Lipid-Lowering Drugs for Primary and Secondary Cardiovascular Prevention.

Despite treatment with statins, patients with elevated low-density lipoprotein cholesterol (LDL-C) and triglycerides remain at increased risk for adverse cardiovascular events. Consequently, novel pharmaceutical drugs have been developed to control and modify the composition of blood lipids to ultimately prevent fatal cardiovascular events in patients with dyslipidaemia. This article reviews established and emerging lipid-lowering drugs regarding their mechanism of action, development stage, ongoing clinical trials, side effects, effect on blood lipids and reduction in cardiovascular morbidity and mortality. We conducted a keyword search to identify studies on established and emerging lipid modifying drugs. Results were summarized in a narrative overview. Established pharmaceutical treatment options include the Niemann-Pick-C1 like-1 protein (NPC1L1) inhibitor ezetimibe, the protein convertase subtilisin-kexin type 9 (PCSK9) inhibitors alirocumab and evolocumab, fibrates as peroxisome proliferator receptor alpha (PPAR-α) activators, and the omega-3 fatty acid icosapent ethyl. Statins are recommended as the first-line therapy for primary and secondary cardiovascular prevention in patients with hypercholesterinaemia and hypertriglyceridemia. For secondary prevention in hypercholesterinaemia, second-line options such as statin add-on or statin-intolerant treatments are ezetimibe, alirocumab and evolocumab. For secondary prevention in hypertriglyceridemia, second-line options such as statin add-on or statin-intolerant treatments are icosapent ethyl and fenofibrate. Robust data for these add-on therapeutics in primary cardiovascular prevention remains scarce. Recent biotechnological advances have led to the development of innovative small molecules (bempedoic acid, lomitapide, pemafibrate, docosapentaenoic and eicosapentaenoic acid), antibodies (evinacumab), antisense oligonucleotides (mipomersen, volanesorsen, pelcarsen, olezarsen), small interfering RNA (inclisiran, olpasiran), and gene therapies for patients with dyslipidemia. These molecules specifically target new cellular pathways, such as the adenosine triphosphate-citrate lyase (bempedoic acid), PCSK9 (inclisiran), angiopoietin-like 3 (ANGPTL3: evinacumab), microsomal triglyceride transfer protein (MTP: lomitapide), apolipoprotein B-100 (ApoB-100: mipomersen), apolipoprotein C-III (ApoC-III: volanesorsen, olezarsen), and lipoprotein (a) (Lp(a): pelcarsen, olpasiran). The authors are hopeful that the development of new treatment modalities alongside new therapeutic targets will further reduce patients' risk of adverse cardiovascular events. Apart from statins, data on new drugs' use in primary cardiovascular prevention remain scarce. For their swift adoption into clinical routine, these treatments must demonstrate safety and efficacy as well as cost-effectiveness in randomized cardiovascular outcome trials.

PPARα and PPARγ are expressed in midbrain dopamine neurons and modulate dopamine- and cannabinoid-mediated behavior in mice.

Peroxisome proliferator-activated receptors (PPARs) are a family of nuclear receptors that regulate gene expression. Δ9-tetrahydrocannabinol (Δ9-THC) is a PPARγ agonist and some endocannabinoids are natural activators of PPARα and PPARγ. However, little is known regarding their cellular distributions in the brain and functional roles in cannabinoid action. Here, we first used RNAscope in situ hybridization and immunohistochemistry assays to examine the cellular distributions of PPARα and PPARγ expression in the mouse brain. We found that PPARα and PPARγ are expressed in ~70% of midbrain dopamine (DA) neurons. In the amygdala, PPARα is expressed in ~60% ofglutamatergic neurons, while PPARγ is expressed in ~60% ofGABA neurons. However, no PPARα/γ signal was detected in GABA neurons in the nucleus accumbens. We then used a series of behavioral assays to determine the functional roles of PPARα/γ in the CNS effects of Δ9-THC. We found that optogenetic stimulation of midbrain DA neurons was rewarding as assessed by optical intracranial self-stimulation (oICSS) in DAT-cre mice. Δ9-THC and a PPARγ (but not PPARα) agonist dose-dependently inhibited oICSS. Pretreatment with PPARα or PPARγ antagonists attenuated the Δ9-THC-induced reduction in oICSS and Δ9-THC-inducedanxiogenic effects. In addition, a PPARγ agonist increased, while PPARα or PPARγ antagonists decreased open-field locomotion. Pretreatment with PPARα or PPARγ antagonists potentiated Δ9-THC-induced hypoactivity and catalepsy but failed to alter Δ9-THC-induced analgesia, hypothermia and immobility. These findings provide the first anatomical and functional evidence supporting an important role of PPARα/γ in DA-dependent behavior and cannabinoid action.

Effects of pemafibrate on left ventricular diastolic function in patients with type 2 diabetes mellitus: a pilot study.

Diabetic cardiomyopathy (DCM) is characterized predominantly by diastolic dysfunction. The multiple mechanisms underlying DCM include altered energy substrate utilization. Recent studies indicate that PPARα plays an important role in the pathogenesis of lipotoxic cardiomyopathy. Pemafibrate is known to be a selective PPARα modulator (SPPARMα). We thus investigated the effects of pemafibrate on cardiac diastolic function in patients with type 2 diabetes. Seventeen patients with type 2 diabetes (T2D) and hypertriglyceridemia were screened and treated with pemafibrate at a dose of 0.2mg/day for 8-16weeks. Fourteen patients were eligible for analysis. Echocardiography was used for assessment of diastolic function. Early diastolic filling velocity (E), late atrial filling velocity (A) and the E/A ratio were included in this study. Peak early diastolic annular velocities (e') were also assessed using color tissue Doppler images. The primary endpoints were changes in the ratio of E to A (E/A), e', and the ratio of E to e' (E/e') from baseline. Pemafibrate significantly increased average e' (7.24 ± 0.58 vs 7.94 ± 0.67, p = 0.019) and a significant reduction in E/e' (9.01 ± 0.94 vs 8.20 ± 0.91, p = 0.041). The increase in e' was significantly related to increases in fasting blood glucose (r = 0.607, p = 0.021) and non-esterified fatty acid (r = 0.592, p = 0.026). Pemafibrate improved diastolic function in patients with T2D and hypertriglyceridemia, suggesting that PPARα activation by pemafibrate prevents the development of DCM at an early stage.

In vitro to in vivo extrapolation for predicting human equivalent dose of phenolic endocrine disrupting chemicals: PBTK model development, biological pathways, outcomes and performance

In vitro to in vivo (IVIVE) leverages in vitro high-throughput biological responses to predict the corresponding in vivo exposures and further estimate the human safe dose. However, for phenolic endocrine disrupting chemicals (EDCs) linked with complicated biological pathways and adverse outcomes (AO), such as bisphenol A (BPA) and 4-nonylphenol (4-NP), plausible estimation of human equivalent doses (HED) by IVIVE approaches considering various biological pathways and endpoints is still challenging. To explore the capabilities and limitations of IVIVE, this study conducted physiologically based toxicokinetic (PBTK)-IVIVE approaches to derive pathway-specific HEDs using BPA and 4-NP as examples. In vitro HEDs of BPA and 4-NP varied in different adverse outcomes, pathways, and testing endpoints and ranged from 0.0013 to 1.0986 mg/kg bw/day and 0.0551 to 1.7483 mg/kg bw/day, respectively. In vitro HEDs associated with reproductive AOs initiated by PPARα activation and ER agonism were the most sensitive. Model verification suggested the potential of using effective in vitro data to determine reasonable approximation of in vivo HEDs for the same AO (fold differences of most AOs ranged in 0.14–2.74 and better predictions for apical endpoints). Furthermore, system-specific parameters of cardiac output and its fraction, body weight, as well as chemical-specific parameters of partition coefficient and liver metabolic were most sensitive for the PBTK simulations. The results indicated that the application of fit for-purpose PBTK-IVIVE approach could provide credible pathway-specific HEDs and contribute to high throughput prioritization of chemicals in a more realistic scenario.

Activation of Liver X Receptors and Peroxisome Proliferator-Activated Receptors by Lipid Extracts of Brown Seaweeds: A Potential Application in Alzheimer's Disease?

The nuclear liver X receptors (LXRα/β) and peroxisome proliferator-activated receptors (PPARα/γ) are involved in the regulation of multiple biological processes, including lipid metabolism and inflammation. The activation of these receptors has been found to have neuroprotective effects, making them interesting therapeutic targets for neurodegenerative disorders such as Alzheimer's Disease (AD). The Asian brown seaweed Sargassum fusiforme contains both LXR-activating (oxy)phytosterols and PPAR-activating fatty acids. We have previously shown that dietary supplementation with lipid extracts of Sargassum fusiforme prevents disease progression in a mouse model of AD, without inducing adverse effects associated with synthetic pan-LXR agonists. We now determined the LXRα/β- and PPARα/γ-activating capacity of lipid extracts of six European brown seaweed species (Alaria esculenta, Ascophyllum nodosum, Fucus vesiculosus, Himanthalia elongata, Saccharina latissima, and Sargassum muticum) and the Asian seaweed Sargassum fusiforme using a dual luciferase reporter assay. We analyzed the sterol and fatty acid profiles of the extracts by GC-MS and UPLC MS/MS, respectively, and determined their effects on the expression of LXR and PPAR target genes in several cell lines using quantitative PCR. All extracts were found to activate LXRs, with the Himanthalia elongata extract showing the most pronounced efficacy, comparable to Sargassum fusiforme, for LXR activation and transcriptional regulation of LXR-target genes. Extracts of Alaria esculenta, Fucus vesiculosus, and Saccharina latissima showed the highest capacity to activate PPARα, while extracts of Alaria esculenta, Ascophyllum nodosum, Fucus vesiculosus, and Sargassum muticum showed the highest capacity to activate PPARγ, comparable to Sargassum fusiforme extract. In CCF-STTG1 astrocytoma cells, all extracts induced expression of cholesterol efflux genes (ABCG1, ABCA1, and APOE) and suppressed expression of cholesterol and fatty acid synthesis genes (DHCR7, DHCR24, HMGCR and SREBF2, and SREBF1, ACACA, SCD1 and FASN, respectively). Our data show that lipophilic fractions of European brown seaweeds activate LXRs and PPARs and thereby modulate lipid metabolism. These results support the potential of brown seaweeds in the prevention and/or treatment of neurodegenerative diseases and possibly cardiometabolic and inflammatory diseases via concurrent activation of LXRs and PPARs.

Digeda-4 decoction and its disassembled prescriptions improve dyslipidemia and apoptosis by regulating AMPK/SIRT1 pathway on tyloxapol-induced nonalcoholic fatty liver disease in mice

Ethnopharmacological relevanceNonalcoholic fatty liver disease (NAFLD) is a manifestation of metabolic syndrome in the liver and the leading cause of chronic liver disease worldwide. Digeda-4 decoction (DGD-4) is a commonly prescribed Mongolian herbal drug for treating acute and chronic liver injury and fatty liver. However, the mechanisms underlying the improvement of dislipidemia and liver injury via treatment with DGD-4 remain unclear. Disassembling a prescription is an effective approach to studying the effects and mechanisms underlying Mongolian medicine prescriptions. By disassembling a prescription, it is feasible to discover effective combinations of individual herbs to optimize a given prescription. Accordingly, we disassembled DGD-4 into two groups: the single Lomatogonium rotatum (L.) Fries ex Nym (LR) (DGD-1) and non-LR (DGD-3). Aim of this studyTo study whether DGD-4 and its disassembled prescriptions have protective effects against tyloxapol (TY)-induced NAFLD and to explore the underlying mechanisms of action and compatibility of prescriptions. Material and methodsNAFLD mice were developed by TY induction. Biochemical horizontal analyses, enzyme-linked immunosorbent assay, and liver histological staining were performed to explore the protective effects of DGD-4 and its disassembled prescriptions DGD-3 and DGD-1. Furthermore, we performed immunohistochemical analyses and Western blotting to further explore the expression of target proteins. ResultsDGD-4 and its disassembled prescriptions could inhibit TY-induced dislipidemia and liver injury. In addition, DGD-4 and its disassembled prescriptions increased the levels of p-AMPKα and p-ACC, but decreased the levels of SREBP1c, SCD-1, SREBP-2, and HMGCS1 proteins. The activation of lipid metabolic pathways SIRT1, PGC-1α, and PPARα improved lipid accumulation in the liver. Moreover, DGD-4 could inhibit hepatocyte apoptosis and treat TY-induced liver injury by upregulating the Bcl-2 expression, downregulating the expression of Bax, caspase-3, caspase-8, and the ratio of Bax/Bcl-2, and positively regulating the imbalance of oxidative stress (OxS) markers (such as superoxide dismutase [SOD], catalase [CAT], malondialdehyde [MDA], and myeloperoxidase [MPO]). DGD-1 was superior to DGD-3 in regulating lipid synthesis-related proteins such as SREBP1c, SCD-1, SREBP-2, and HMGCS1. DGD-3 significantly affected the expression of lipid metabolic proteins SIRT1, PGC-1α, PPARα, apoptotic proteins Bcl-2, Bax, caspase-3, caspase-8, and the regulation of Bax/Bcl-2 ratio. However, DGD-1 showed no regulatory effects on Bax and Bcl-2 proteins. ConclusionThis study demonstrates the protective effects of DGD-4 in the TY-induced NAFLD mice through a mechanism involving improvement of dyslipidemia and apoptosis by regulating the AMPK/SIRT1 pathway. Although the Monarch drug DGD-1 reduces lipid accumulation and DGD-3 inhibits apoptosis and protects the liver from injury, DGD-4 can be more effective overall as a therapy when compared to DGD-1 and DGD-3.

Loss of functional peroxisomes leads to increased mitochondrial biogenesis and reduced autophagy that preserve mitochondrial function

Peroxisomes are essential for mitochondrial health, as the absence of peroxisomes leads to altered mitochondria. However, it is unclear whether the changes in mitochondria are a function of preserving cellular function or a response to cellular damage caused by the absence of peroxisomes. To address this, we developed conditional hepatocyte-specific Pex16 deficient (Pex16 KO) mice that develop peroxisome loss and subjected them to a low-protein diet to induce metabolic stress. Loss of PEX16 in hepatocytes led to increased biogenesis of small mitochondria and reduced autophagy flux but with preserved capacity for respiration and ATP capacity. Metabolic stress induced by low protein feeding led to mitochondrial dysfunction in Pex16 KO mice and impaired biogenesis. Activation of PPARα partially corrected these mitochondrial disturbances, despite the absence of peroxisomes. The findings of this study demonstrate that the absence of peroxisomes in hepatocytes results in a concerted effort to preserve mitochondrial function, including increased mitochondrial biogenesis, altered morphology, and modified autophagy activity. Our study underscores the relationship between peroxisomes and mitochondria in regulating the hepatic metabolic responses to nutritional stressors.

Selective activation of PPARα maintains thermogenic capacity of beige adipocytes

Beige adipocytes are inducible thermogenic adipocytes used for anti-obesity treatment. Beige adipocytes rapidly lose their thermogenic capacity once external cues are removed. However, long-term administration of stimulants, such as PPARγ and β-adrenergic receptor agonists, is unsuitable due to various side effects. Here, we reported that PPARα pharmacological activation was the preferred target for maintaining induced beige adipocytes. Pemafibrate used in clinical practice for dyslipidemia was developed as a selective PPARα modulator (SPPARMα). Pemafibrate administration regulated the thermogenic capacity of induced beige adipocytes, repressed body weight gain, and ameliorated impaired glucose tolerance in diet-induced obese mouse models. The transcriptome analysis revealed that the E-twenty-six transcription factor ELK1 acted as a cofactor of PPARα. ELK1 was mobilized to the Ucp1 transcription regulatory region with PPARα and modulated its expression by pemafibrate. These results suggest that selective activation of PPARα by pemafibrate is advantageous to maintain the function of beige adipocytes.

Peroxisome proliferator-activated receptor-α activation facilitates contextual fear extinction and modulates intrinsic excitability of dentate gyrus neurons

The dentate gyrus (DG) of the hippocampus encodes contextual information associated with fear, and cell activity in the DG is required for acquisition and extinction of contextual fear. However, the underlying molecular mechanisms are not fully understood. Here we show that mice deficient for peroxisome proliferator-activated receptor-α (PPARα) exhibited a slower rate of contextual fear extinction. Furthermore, selective deletion of PPARα in the DG attenuated, while activation of PPARα in the DG by local infusion of aspirin facilitated extinction of contextual fear. The intrinsic excitability of DG granule neurons was reduced by PPARα deficiency but increased by activation of PPARα with aspirin. Using RNA-Seq transcriptome we found that the transcription level of neuropeptide S receptor 1 (Npsr1) was tightly correlated with PPARα activation. Our results provide evidence that PPARα plays an important role in regulating DG neuronal excitability and contextual fear extinction.

Effects of perfluorooctanoic acid (PFOA) on gene expression profiles via nuclear receptors in HepaRG cells: Comparative study with in vitro transactivation assays

Perfluorooctanoic acid (PFOA), a synthetic perfluorinated eight-carbon organic chemical, induces hepatotoxicity in rodents, indicated increased liver weight, hepatocellular hypertrophy, necrosis, and peroxisome proliferation. Epidemiological studies have demonstrated the association between serum PFOA levels and various adverse effects. In this study, we investigated the gene expression profiles of human HepaRG cells exposed to 10 and 100 μM PFOA for 24 h. Treatment with 10 and 100 μM PFOA significantly modulated the expression of 190 and 996 genes, respectively. Genes upregulated or downregulated by 100 µM PFOA included peroxisome proliferator-activated receptor (PPAR) signaling genes related to lipid metabolism, adipocyte differentiation, and gluconeogenesis. Moreover, we identified the “Nuclear receptors-meta pathways” following the activation of other nuclear receptors: constitutive androstane receptor (CAR), pregnane X receptor (PXR) and farnesoid X receptor (FXR), as well as the transcription factor nuclear factor E2-related factor 2 (Nrf2). The expression levels of some target genes (CYP4A11, CYP2B6, CYP3A4, CYP7A1, and GPX2) of these nuclear receptors and Nrf2 were confirmed using quantitative reverse transcription polymerase chain reaction. Next, we performed transactivation assays using COS-7 and HEK293 cells to investigate whether these signaling-pathways were activated by the direct effects of PFOA on human PPARα, CAR, PXR, FXR and Nrf2. PFOA concentration-dependently activated PPARα, but not CAR, PXR, FXR, or Nrf2. Taken together, these results suggest that PFOA affects the hepatic transcriptomic responses of HepaRG cells through the direct activation of PPARα and indirect activation of CAR, PXR, FXR, and Nrf2. Our finding indicates that PPARα activation in the “Nuclear receptors-meta pathways” functions as a molecular initiating event for PFOA, and indirect activation of alternative nuclear receptors and Nrf2 also induce important molecular mechanisms in PFOA-induced human hepatotoxicity.

A putative adverse outcome network for neonatal mortality and lower birth weight in rodents: Applicability to per- and polyfluoroalkyl substances and relevance to human health.

Some per- and poly-fluoroalkyl substances (PFAS) cause neonatal mortality and lower birth weight in rodents. We constructed an Adverse Outcome Pathway (AOP) network for neonatal mortality and lower birth weight in rodents, comprising three putative AOPs. We then assessed strengths of the evidence for the AOPs and applicability to PFAS. Finally, we considered the relevance of this AOP network to human health. Literature searches targeted PFAS, peroxisome proliferator-activated receptor (PPAR) agonists, other nuclear receptors, relevant tissues, and developmental targets. We used reviews of established biology and described results of studies with prenatal PFAS exposure that assessed birth weight and neonatal survival. Molecular initiating events (MIEs) and key events (KEs) were proposed and strengths of KE relationships (KERs), applicability to PFAS, and human relevance were assessed. Neonatal mortality has been observed in rodents following gestational exposure to most longer chain PFAS studied, often coincident with lower birth weight. In AOP 1, PPARα activation and PPARγ activation or downregulation are MIEs; placental insufficiency, fetal nutrient restriction, neonatal hepatic glycogen deficit, and hypoglycemia are KEs leading to neonatal mortality and lower birth weight. In AOP 2, constitutive androstane receptor (CAR) and pregnane X receptor (PXR) activation upregulates Phase II metabolism, lowering maternal circulating thyroid hormones. In AOP 3, disrupted pulmonary surfactant function and PPARγ downregulation cause neonatal airway collapse and mortality from respiratory failure. It is likely that different components of this AOP network will apply to different PFAS, largely determined by which nuclear receptors they activate. The MIEs and KEs in this AOP network can occur in humans, but differences in PPAR structure and function, and the timeline of liver and lung development, suggest that humans may be less susceptible to this AOP network. This putative AOP network elucidates knowledge gaps and research needed to better understand the developmental toxicity of PFAS.

Peroxisome proliferator-activated receptor α agonist induces mouse hepatomegaly through the spatial hepatocyte enlargement and proliferation.

Peroxisome proliferator-activated receptor alpha (PPARα) activation-induced hepatomegaly is accompanied by hepatocyte hypertrophy around the central vein (CV) area and hepatocyte proliferation around the portal vein (PV) area. However, the molecular mechanisms underlying this spatial change of hepatocytes remains unclear. In this study, we examined the characteristics and possible reasons for the zonation distinction of hypertrophy and proliferation during PPARα activation-induced mouse liver enlargement. Mice were injected with corn oil or a typical mouse PPARα agonist WY-14643 (100 mg·kg-1·d-1, i.p.) for 1, 2, 3, 5 or 10 days. At each time point, the mice were sacrificed after the final dose, and liver tissues and serum were harvested for analysis. We showed that PPARα activation induced zonal changes in hepatocyte hypertrophy and proliferation in the mice. In order to determine the zonal expression of proteins related to hepatocyte hypertrophy and proliferation in PPARα-induced liver enlargement, we performed digitonin liver perfusion to separately destroy the hepatocytes around the CV or PV areas, and found that PPARα activation-induced increase magnitude of its downstream targets such as cytochrome P450 (CYP) 4 A and acyl-coenzyme A oxidase 1 (ACOX1) levels around the CV area were higher compared with those around the PV area. Upregulation of proliferation-related proteins such as cell nuclear antigen (PCNA) and cyclin A1 (CCNA1) after WY-14643-induced PPARα activation mainly occurred around the PV area. This study reveals that the zonal expression of PPARα targets and proliferation-related proteins is responsible for the spatial change of hepatocyte hypertrophy and proliferation after PPARα activation. These findings provide a new insight into the understanding of PPARα activation-induced liver enlargement and regeneration.

Potential Role of the mTORC1-PGC1α-PPARα Axis under Type-II Diabetes and Hypertension in the Human Heart.

Type-2 diabetes (T2DM) and arterial hypertension (HTN) are major risk factors for heart failure. Importantly, these pathologies could induce synergetic alterations in the heart, and the discovery of key common molecular signaling may suggest new targets for therapy. Intraoperative cardiac biopsies were obtained from patients with coronary heart disease and preserved systolic function, with or without HTN and/or T2DM, who underwent coronary artery bypass grafting (CABG). Control (n = 5), HTN (n = 7), and HTN + T2DM (n = 7) samples were analysed by proteomics and bioinformatics. Additionally, cultured rat cardiomyocytes were used for the analysis (protein level and activation, mRNA expression, and bioenergetic performance) of key molecular mediators under stimulation of main components of HTN and T2DM (high glucose and/or fatty acids and angiotensin-II). As results, in cardiac biopsies, we found significant alterations of 677 proteins and after filtering for non-cardiac factors, 529 and 41 were changed in HTN-T2DM and in HTN subjects, respectively, against the control. Interestingly, 81% of proteins in HTN-T2DM were distinct from HTN, while 95% from HTN were common with HTN-T2DM. In addition, 78 factors were differentially expressed in HTN-T2DM against HTN, predominantly downregulated proteins of mitochondrial respiration and lipid oxidation. Bioinformatic analyses suggested the implication of mTOR signaling and reduction of AMPK and PPARα activation, and regulation of PGC1α, fatty acid oxidation, and oxidative phosphorylation. In cultured cardiomyocytes, an excess of the palmitate activated mTORC1 complex and subsequent attenuation of PGC1α-PPARα transcription of β-oxidation and mitochondrial electron chain factors affect mitochondrial/glycolytic ATP synthesis. Silencing of PGC1α further reduced total ATP and both mitochondrial and glycolytic ATP. Thus, the coexistence of HTN and T2DM induced higher alterations in cardiac proteins than HTN. HTN-T2DM subjects exhibited a marked downregulation of mitochondrial respiration and lipid metabolism and the mTORC1-PGC1α-PPARα axis might account as a target for therapeutical strategies.

EARLY PPARα ACTIVATION PROTECT AGAINST HEPATIC MICROSTEATOSIS INDUCED BY POST-NATAL OVERFEEDING

Post-natal overfeeding leads to development of obesity and metabolic dysfunction. PPARαactivation improves steatosis and metabolic dysfunction associated with obesity. Thus, wehave hypothesized that PPARα would prevent the metabolic disorders and obesity caused bylitter reduction. Wistar male offspring rats were divided into normal litter (NL - 9 pups) andsmall litter (SL - 3 pups) and were daily treated with an PPARα agonist, fenofibrate, frompost-natal day (PN) 1 until weaning (PN21), with either, fenofibrate (F - 12.5mg/kg) orvehicle (V). Forming the following groups: NL-V, NL-F, SL-V, SL-F. At PN120 animalswere euthanized and histological evaluation of samples from liver, visceral (VAT),subcutaneous (SAT) and brown (BAT) adipose tissue were performed. Fenofibrate was ableto prevent the development of microsteatosis in the liver caused by postnatal overfeeding. Inregard to VAT, there was no difference in the mean adipocyte area, however in distributionanalyzes it was observed higher frequency of larger adipocytes in SL groups, and nodifference was observed in SAT. SL-V animals had increased lipid area in BAT, which wasreduced in SL-F. Increased PPARα activation induced by an agonist during lactationimproved some histopathological abnormalities induced by postnatal overfeeding. This wasproven by the decrease in microsteatosis in the liver and improvement in VAT and BATmorphology, thus implying a better metabolic health.

Juniper Berries Regulate Diabetes and Obesity Markers Through Modulating PPARα, PPARγ, and LXR: In Vitro and In Vivo Effects.

The berries of Juniperus communis have been traditionally used for therapeutic purposes. They have been reported to possess various pharmacological effects such as anti-inflammatory, hypoglycemic and hypolipidemic activities. In this study, a methanolic extract of J. communis berries (JB) was evaluated for its effects on peroxisome proliferator-activated receptors alpha and gamma (PPARα and PPARγ), liver X receptor (LXR), glucose uptake and lipid accumulation using various cellular systems. At a concentration of 25 μg/mL, JB caused 3.77-fold activation of PPARα, 10.90-fold activation of PPARγ, and 4.43-fold activation of LXR in hepatic cells. JB inhibited (11%) the adipogenic effect induced by rosiglitazone in adipocytes and increased glucose uptake (90%) in muscle cells. In high-fat diet (HFD) fed mice, JB at a dose of 25 mg/kg body weight exhibited a 21% decrease in body weight. Fasting glucose levels in mice treated with 12.5 mg/kg of JB were significantly decreased (39%) indicating its efficacy in regulating hyperglycemia and obesity induced by HFD thus ameliorating the symptoms of type 2 diabetes. A series of energy metabolic genes, including Sirt1 (2.00-fold) and RAF1 (2.04-fold), were upregulated by JB, while rosiglitazone regulated the hepatic PPARγ only. Phytochemical analysis of JB indicated presence of a number of flavonoids and biflavonoids which seem to be responsible for the observed activity. It was concluded that JB acted as a multiple agonist of PPARα, PPARγ and LXR without the undesired effect of adipogenesis and exhibited the property of enhancing glucose uptake. The regulation of PPARα, PPARγ and LXR seems to be through Sirt1 and RAF1. In vivo results confirmed the antidiabetic and antiobesity potential of JB and indicated its utility in metabolic disorder and type 2 diabetes.

Investigating the lipid-immune signaling axis in modulating the inflammatory response to Salmonella entericaserovar Typhimurium infections

Abstract Salmonella entericaserovar Typhimurium (STM) is an intracellular pathogen that causes gastroenteritis and can disseminate systemically through survival in phagocytes. Eicosanoids-derived bioactive lipids play critical roles in both the induction and resolution of inflammation during bacterial infections or other insults. A subset of these lipids are endogenous ligands for nuclear receptors/transcription factors Peroxisome proliferator-activated receptors (PPAR), which play major roles in fatty acid metabolism and modulation of immune functions (including macrophage MΦ polarization). To elucidate the role of PPARα, we infected streptomycin-pretreated C57BL/6 (wildtype) and Ppara−/−mice with STM (colitis model). We determined that Ppara−/−mice have increased eicosanoid production, decreased inflammatory gene expression and histopathology scores in cecal tissue, and reduced systemic dissemination of bacteria, compared to C57BL/6 mice. These data suggest that the activation of PPARα results in a deleterious immune response favoring STM infection. When polarizing MΦ to various subsets, STM infection enhanced M2b and M2c polarizations (anti-inflammatory and immunoregulatory) in a PPARα-dependent manner. Using liquid chromatography-mass spectrometry (LC/MS), we also determined that STM infection alters the fatty acid profiles in polarized MΦ. Specifically, C57BL/6 M2b-polarized STM-infected MΦ have decreased ceramide levels compared to uninfected control, which would inhibit programmed cell death and enhance bacterial intracellular survival. These findings provide important insights into how the reprogramming of immune metabolism affects host-pathogen interactions during bacterial infections. This work was supported by National Institute of Allergy and Infectious Disease R01 AI168550 (VT)

The nuclear receptor PPARα (peroxisome proliferator-activated receptor α) as a novel therapeutic target for schizophrenia

Our previous study has suggested that peroxisome proliferator-activated receptor α (PPARα) plays a crucial role in the pathophysiology of schizophrenia. In the current study, we screened and identified rare variants in the PPARA gene (encoding PPARα) of schizophrenia subjects. In vitro study showed that those variants decreased activities of PPARα as a transcription factor. Ppara KO mice exhibited a deficit in the sensorimotor gating function and schizophrenia-related histological abnormalities. RNA-seq analysis revealed that PPARα regulates the expression of synaptogenesis signaling pathway-related genes in the brain. Remarkably, treatment of mice with the PPARα agonist fenofibrate alleviated an NMDA receptor antagonist, phencyclidine (PCP)-induced spine pathology and reduced sensitivity to MK-801, another NMDA receptor antagonist. In conclusion, the current study further supports the idea that perturbation in the PPARα-regulated transcriptional machinery leads to a predisposition to schizophrenia, probably by affecting synapse physiology. This study also demonstrates that PPARα can serve as a novel therapeutic target for schizophrenia.