PPARα Activation Research Articles

Magnolol preserves the integrity of the intestinal epithelial barrier and mitigates intestinal injury through activation of PPAR γ in COPD rat

Ethnopharmacological relevanceMagnolia officinalis Rehder & E.H. Wilson is traditionally used in the treatment of gastrointestinal disorders, diarrhea, and cough. Its main active ingredient, magnolol, exhibits protective effects on the lungs and gastrointestinal tract, including the inhibition of inflammation in these organs. Aim of the studyThis work aims to explore the molecular mechanism by which magnolol suppressed Chronic obstructive pulmonary disease (COPD) intestinal damage by improving the intestinal epithelial barrier. Materials and methodsThe study focused on investigating the mitigation effect of magnolol on intestinal injury and epithelial barrier in a COPD rat. Caco-2 cells were induced with TNF-α or IL-1β to establish the barrier injury model in order to explore the direct protective effect of magnolol on the intestinal barrier and elucidate the molecular mechanism by which it activates peroxisome proliferators-activated receptors-γ (PPARγ). ResultsMagnolol significantly improves pulmonary function and tissue damage in COPD rats by inhibiting inflammation, protease imbalance, and oxidative stress. It also suppresses colon tissue damage and inflammation, and protects colon epithelial barrier function by suppressing the decline of tight junction proteins, reducing colon epithelial permeability. In Caco-2 cells, magnolol directly reduces monolayer permeability, increases TEER, and upregulates tight junction protein expression induced by TNF-α or IL-1β. Drug Affinity Responsive Target Stability (DARTS) and thermal shift assays show that magnolol effectively binds to SRC, activating PPARγ signaling in Caco-2 cells and colon tissues of COPD rats. Furthermore, magnolol enhances the binding of PPARγ and RXRα, promoting their activation and entry into the nucleus. The PPARγ inhibitor GW9662 can reverse the effects of magnolol on PPARγ activation and tight junction protein upregulation in IL-1β or TNF-α induced Caco-2 cells. ConclusionsThis work demonstrates that magnolol enhances lung and intestinal functions in COPD rats, and elucidates its mechanism of action in protecting the intestinal epithelial barrier by activating PPARγ.

Lipotoxicity of palmitic acid is associated with DGAT1 downregulation and abolished by PPARα activation in liver cells

Lipotoxicity refers to the harmful effects of excess fatty acids on metabolic health, and it can vary depending on the type of fatty acids involved. Saturated and unsaturated fatty acids exhibit distinct effects, though the precise mechanisms behind these differences remain unclear. Here, we investigated the lipotoxicity of palmitic acid (PA), a saturated fatty acid, compared with oleic acid (OA), a monounsaturated fatty acid, in the hepatic cell line HuH7.Our results demonstrated that PA, unlike OA, induces lipotoxicity, endoplasmic reticulum (ER) stress, and autophagy inhibition. Compared with OA, PA treatment leads to less lipid droplet (LD) accumulation and a significant reduction in the mRNA and protein level of diacylglycerol acyltransferase 1 (DGAT1), a key enzyme of triacylglycerol synthesis. Using modulators of ER stress and autophagy, we established that DGAT1 downregulation by PA is closely linked to these cellular pathways. Notably, the ER stress inhibitor 4-phenylbutyrate can suppress PA-induced DGAT1 downregulation. Furthermore, knockdown of DGAT1 by siRNA or with A922500, a specific DGAT1 inhibitor, resulted in cell death, even with OA. Both PA and OA increased the oxygen consumption rate; however, the increase associated with PA was only partially coupled to ATP synthesis. Importantly, treatment with GW7647 a specific PPARα agonist mitigated the lipotoxic effects of PA, restoring PA-induced ER stress, autophagy block, and DGAT1 suppression. In conclusion, our study highlights the crucial role of DGAT1 in PA-induced lipotoxicity, broadening the knowledge of the mechanisms underlying hepatic lipotoxicity and providing the basis for potential therapeutic interventions.

E2F3a Activates Gadd45b Gene Expression Through PPARα-Mediated Transcriptional Regulation in Hepatic Cells

Growth arrest and DNA damage-inducible beta (GADD45b) plays a critical role in intracellular events such as cell growth and apoptosis. Although the functional study of GADD45b has been conducted, the mechanism for the transcriptional regulation of GADD45b is largely unknown. Due to the drastic induction of hepatic GADD45b mRNA by peroxisome proliferator-activated receptor alpha (PPARα) activation in wild-type mice, we investigated a key factor that affects the upregulation of GADD45b mRNA. Interestingly, we found that GADD45b-promoter luciferase activity was dramatically increased as the 5’-flanking regions were closer to the transcription start site (TSS) in Hepa1c1c7 cells. Additionally, we found two E2F (E2F-myc activator/cell cycle regulator) binding motifs in the region (-150/-1) of the GADD45b promoter. Notably, E2F3 mRNA was significantly increased only in wild-type mice treated with WY-14643, a PPARα agonist, followed by the induction of GADD45b mRNA. Furthermore, gene functional studies and Chromatin Immunoprecipitation (ChIP) assays revealed that E2F3 could regulate the GADD45b gene via the E2F binding motif. Thus, we suggest that E2F3 may play a key role in regulating the GADD45b gene as a positive transcription factor.

Potential Mechanism of Perillaldehyde in the Treatment of Nonalcoholic Fatty Liver Disease Based on Network Pharmacology and Molecular Docking

Non-alcoholic fatty liver disease (NAFLD) is one of the most common chronic metabolic liver diseases worldwide. Perillaldehyde (4-propyl-1-en-2-ylcyclohexene-1-aldehyde, PA) is a terpenoid compound extracted from Perilla, which has effective pharmacological activities such as anti-inflammatory, antidepressant, and anticancer. This study aimed to explore the pharmacological effects of PA in intervening with NAFLD and reveal its potential mechanisms. Firstly, we identified the core targets of PA intervention therapy for NAFLD through network pharmacology and molecular docking techniques. After that, in vitro animal experiments such as H&E and Masson staining, immunofluorescence, immunohistochemistry, and western blot were conducted to validate the results network effectively pharmacology predicted. Network pharmacology analysis suggested that PPAR-α may be the core target of PA intervention in NAFLD. H&E and Masson staining showed that after low-dose (50mg/kg) PA administration, there was a noticeable improvement in fat deposition in the livers of NAFLD mice, and liver tissue fibrosis was alleviated. Immunohistochemical and immunofluorescence analysis showed that low dose (50mg/kg) PA could reduce hepatocyte apoptosis, decrease the content of pro-apoptosis protein Bax, and increase the expression of anti-apoptosis protein Bcl-2 in NAFLD mice. Western blot results confirmed that low-dose (50mg/kg) PA could increase the expression of PPAR-α and inhibit the expression of NF-κB in NAFLD mice. Our study indicated that PA could enhance the activity of PPAR-α and reduce the level of NF-κB in NAFLD mice, which may positively affect the prevention of NAFLD.

Selective activation of PPARα by pemafibrate mitigates peritoneal inflammation and fibrosis through suppression of NLRP3 inflammasome and modulation of inflammation

Peritoneal inflammation and fibrosis remain major challenges to the long-term maintenance of peritoneal dialysis. Pemafibrate, a selective peroxisome proliferator-activated receptor α (PPARα) modulator, has been implicated in the management of fibrosis-related disorders. We investigated whether pemafibrate ameliorates peritoneal inflammation and fibrosis and explored the underlying mechanisms in mice with methylglyoxal (MGO)-induced peritoneal fibrosis (MGO mice). MGO mice exhibited peritoneal fibrosis with increased expression of mesenchymal markers, transforming growth factor-β1 (TGF-β1), and substantial deposition of extracellular matrix (ECM) proteins. Additionally, MGO mice exhibited peritoneal inflammation as indicated by elevated tumor necrosis factor-α expression and macrophage infiltration in peritoneal tissue. These effects were mitigated by pemafibrate treatment, which also restored peritoneal membrane function. Furthermore, pemafibrate promoted anti-inflammatory macrophage polarization in both mice and THP-1 cells. In human peritoneal mesothelial cells (HPMCs), pemafibrate effectively inhibited interferon-γ-induced production of TGF-β1 and ECM while suppressing the proinflammatory cytokines nuclear factor-κB (NF-κB) and activator protein 1. The NF-κB inhibitory effect of pemafibrate involved stabilization of the NF-κB inhibitory protein IkBα. Notably, pemafibrate hindered activation of the NLR family pyrin domain containing 3/caspase-1 axis in interferon-γ-stimulated THP-1 cells. These findings suggest that pemafibrate ameliorates peritoneal inflammation and fibrosis, making it a promising candidate for peritoneal fibrosis therapy.

6827 Pharmacological PPARα Activation In Combination With Ketogenic Nutrition Aggravated Muscle Weakness By Metabolic Failure In Septic Mice

Abstract Disclosure: C. Lauwers: None. M.P. Casaer: None. W. Vankrunkelsven: None. S. Derde: None. I. Derese: None. S. Vander Perre: None. P. Vermeersch: None. G.H. Van Den Berghe: None. L. Langouche: None. Introduction: In septic mice, infusion of ketone bodies (beta-hydroxybutyrate (BHB)) attenuated muscle weakness, a debilitating complication of critical illness. Interestingly, in critically ill children, fasting-induced ketosis also improved outcomes, but in adults ketosis upon fasting was impaired, likely due to suppression of PPARα, a key transcriptional regulator of ketogenesis. In septic mice, pharmacological induction of PPARα by pemafibrate (PF) alone, however, was ineffective in promoting ketosis. Therefore, we here hypothesized that PPARα activation by PF combined with ketogenic nutrition can more effectively induce ketosis and hereby reduce muscle weakness in sepsis. Methods: In a fluid-resuscitated and antibiotic-treated mouse model of prolonged (5 days) sepsis (male C57BL/6J), the impact of PF (1mg/kg/d) combined with 4 types of parenteral nutrition (PN) was studied. Mice were either allocated to PF + total PN (composed of glucose, long-chain triglycerides (LCTs) and amino acids) (TPN, n = 18), PF + TPN with an extra LCT emulsion (TPN + LCTs, n = 18), PF + a pure low dose LCT emulsion (Low LCT, n = 16) or PF + a pure high dose LCT emulsion (High LCT n = 18). Healthy control mice on standard chow served as a reference (HC, n=19). After 5 days of sepsis, ex vivo muscle force (aurora scientific®), plasma BHB and lipids (TG, FFA, LDL- and HDL-cholesterol; commercial assays), and liver gene expression levels were measured. Metabolomics of muscle tissue was assessed by LC-MS and plasma acylcarnitines by LC-MS-MS. Results: Liver PPARα gene expression was higher in all PF-treated mice than in HCs. Compared to HCs, specific muscle force was reduced in all septic mice, but mostly so in both PF + LCT groups (PF + Low LCT: 10.7%, PF + High LCT: 25.0%, PF+TPN + LCTs: 44.6%, PF+TPN: 58.4% of HC: 124.7 mN/mm²; p = 0.0001). PF + TPN + LCTs did not induce ketosis, whereas BHB plasma levels increased 95-fold in the PF + High LCT and 10-fold in the PF + Low LCT group (p < 0.0001 vs. other groups). Glycemia was lower in both PF + LCT groups relative to the other septic mice (PF + Low LCT: 52 mg/dl; PF + High LCT: 80 mg/dl; PF + TPN + LCTs: 108 mg/dl; PF + TPN: 102 mg/dl; p < 0.0001). Compared to the PF + TPN group, plasma lipids and long-chain acylcarnitines were increased in all other septic mice with the highest levels in the PF + High LCT group. Muscular glycolytic intermediates and ATP levels were depleted in both PF + LCT groups in comparison with all other septic mice and HCs. Conclusion: In septic mice, PF-induced PPARα activation combined with TPN, irrespective of the amount of LCTs, was unable to induce ketosis and did not attenuate muscle weakness. By contrast, PF-induced PPARα activation in combination with pure LCTs resulted in ketosis, but aggravated rather than improved muscle weakness, irrespective of the dose. In these groups, metabolic analyses suggested a bioenergetic failure of muscle fibers with an accumulation of plasma lipids. Presentation: 6/1/2024

Intestinal epithelial cell NCoR deficiency ameliorates obesity and metabolic syndrome

Nuclear receptor corepressor (NCoR1) interacts with various nuclear receptors and regulates the anabolism and catabolism of lipids. An imbalance in lipid/energy homeostasis is also an important factor in obesity and metabolic syndrome development. In this study, we found that the deletion of NCoR1 in intestinal epithelial cells (IECs) mainly activated the nuclear receptor PPARα and attenuated metabolic syndrome by stimulating thermogenesis. The increase in brown adipose tissue thermogenesis was mediated by gut-derived tricarboxylic acid cycle intermediate succinate, whose production was significantly enhanced by PPARα activation in the fed state. Additionally, NCoR1 deletion derepressed intestinal LXR, increased cholesterol excretion, and impaired duodenal lipid absorption by decreasing bile acid hydrophobicity, thereby reversing the possible negative effects of intestinal PPARα activation. Therefore, the simultaneous regulatory effect of intestinal NCoR1 on both lipid intake and energy expenditure strongly suggests that it is a promising target for developing metabolic syndrome treatment.

Dual PPAR-a/g enhances beta cell identity, preserving islet structure in HF-fed mice.

The pancreas suffers from lipotoxicity, which threatens the survival of pancreatic islets. Dual PPAR-alpha(a)/gamma(g) agonism is a promising method for treating type 2 diabetes. This study evaluated the effects of single PPAR-a and PPAR-g or their combined activation on pancreatic islet remodeling, beta-cell proliferation, identity, and maintenance in an experimental obesity model. Fifty three-month-old mice, randomly divided to receive the control (C) or high-fat (HF) diet for ten weeks, were then redivided for a four-week treatment: C, HF, HF-a (received the PPAR-a agonist), HF-g (PPAR-g agonist pioglitazone), and HF-d (PPAR-a/g agonists). The HF group was overweight, had oral glucose intolerance, showed a proinflammatory adipokine profile, exhibited increased alpha and beta cell masses, and islet gene expression compatible with compromised beta cell proliferation and favored dedifferentiation. All treatments reduced body weight, mitigated oral glucose intolerance, and produced an anti-inflammatory adipokine profile, which rescued islet cytoarchitecture, and beta cell function. Principal component analysis (PCA) revealed a shift in the antiapoptotic gene Bcl2 and beta cell proliferation genes (Pax4 and Neurog3) in HF-a. Conversely, HF-g and HF-d benefited from the upregulation of genes related to beta cell function (Fgf21, Glut2, and Glp1r), identity, and maintenance (Pdx1, Neurod1, Mafa, and Nkx6.1). The HF mice were glucose intolerant, showing islet hypertrophy and low beta cell identity-related genes. In contrast, PPAR activation rescued islet structure, and PCA showed that the PPAR-a/g combination was the most effective treatment because it favored beta cell function, identity, and maintenance-related genes, halting the T2DM spectrum in diet-induced obese mice.

Clinopodium gracile Alleviates Metabolic Dysfunction-Associated Steatotic Liver Disease by Upregulating Peroxisome Proliferator-Activated Receptor α and Inhibiting Mitochondrial Oxidative Damage.

The most prevalent chronic liver disease, known as metabolic dysfunction-associated steatotic liver disease (MASLD), is characterized by an excessive accumulation of lipids and oxidative damage. Clinopodium gracile, a natural herbal medicine widely used by Chinese folk, has antioxidative, anti-inflammatory, and lipid metabolism-regulating effects. Here, we explored the effect of C. gracile extract (CGE) on MASLD using palmitic acid (PA)-induced hepatocytes and high-fat diet (HFD)-fed mice. In vitro, CGE could promote fatty acid oxidation and inhibit fatty acid synthesis and uptake to reduce lipid accumulation by regulating PPARα activation. Moreover, CGE could inhibit reactive oxygen species production and maintain mitochondrial homeostasis in PA-induced HepG2 cells. In vivo, animal study results indicated that CGE could effectively reduce lipid metabolism disorder, inhibit oxidative stress, and upregulate PPARα protein in the liver of HFD-fed mice. Molecular docking results also showed that active compounds isolated from CGE had low binding energy and highly stable binding with PPARα. In summary, these findings reveal that CGE may be a potential therapeutic candidate for MASLD and act by upregulating PPARα to reduce lipid accumulation and suppress mitochondrial oxidative damage.

Weighted gene co-expression network analysis identified GBP2 connected to PPARα activity and liver cancer

Liver cancer is the fourth leading cause of cancer-related deaths with a steadily increasing rate worldwide, as a well-known hallmark of liver cancer, metabolic alterations are related to liposomal changes, a common characteristic of primary liver cancers based on recent lipidomics studies. Peroxisome proliferator-activated receptor α (PPARα) is a ligand-activated transcription factor with important lipid homeostasis function, therefore we aimed to understand the molecular mechanisms and pathways that activate PPARα after using PPAR-α agonist WY-14643 and identify candidate biomarkers related to PPARα activity and evaluate their effects in liver cancer. The data from differently expressed genes (DEGs) between liver cancer tissue from obese subjects alone and liver tissue after treatment were evaluated by DESeq2 and module genes were analyzed using weighted gene co-expression network analysis (WGCNA). Final candidate genes were identified by intersecting genes among highly ranked DEGs and the brown module, which demonstrated a significant negative correlation with drug treatments. We conducted a protein–protein interaction network, and KEGG enrichment analysis, and core hub genes (CD40, CXCL9, CXCL10, TNFSF14, GBP2, GBP3, APOL3, CLDN1) were identified using the cyto-hubba plugin, among them we focused on GBP2 that plays key roles in oncogenesis and evaluate its expressional with clinical outcomes. In conclusion, the WGCNA-based co-expression network identified GBP2 as one of the hub genes with a negative relation with PPARα agonist treatments. higher expression of GBP2 was closely associated with HCC progression. Therefore, GBP2 might be a potential candidate for the study of PPARα activity in HCC.

Saroglitazar, a PPAR α/γ agonist alleviates 3-Nitropropionic acid induced neurotoxicity in rats: Unveiling the underlying mechanisms

Saroglitazar (SGZ), a peroxisomal proliferated activated receptor α/γ agonist showed neuroprotective effects in various neurodegenerative disorders like Alzheimer’s and Parkinson’s. However, no studies were performed on Huntington’s, so the goal of the current study is to examine the effect of SGZ on Huntington’s disease like symptoms induced by 3-Nitropropionic acid. In this protocol, twenty-four rats were divided into four groups, each group consisting of 6 animals. Group 1: The control group received 1 % CMC 10 mg/kg, p.o. for 14 days. Groups 2, 3, and 4 received 3-NP 15 mg/kg, i.p. from Day 1 to Day 7. Groups 3 and 4 received SGZ 5 mg/kg, p.o. and 10 mg/kg, p.o. respectively once daily from day 1 to day 14. Various behavioral tests like OFT, rotarod, hanging wire, narrow beam walk, MWM, and Y-maze were performed. On day-15, the animals were euthanised by cervical dislocation and brain sample were isolated for biochemical and histopathological analysis. Administration of 3-NP showed a significant decrease in motor coordination and cognitive function. Furthermore, 3-NP altered the activity of acetylcholinesterase, anti-oxidant enzymes, Nrf-2, NF-κB, BDNF, CREB levels, and histological features. However, treatment with SGZ showed ameliorative effects in the 3-NP induced neurotoxicity via PPAR α/γ pathway by reducing motor dysfunction, memory impairment, cholinesterase levels, oxidative stress, neuroinflammation. It also enhanced the levels of Nrf-2, BDNF, and CREB expression and improved histological features. In conclusion, treatment with Saroglitazar attenuated Huntington’s disease-like symptoms in rats which are induced by 3-NP via activation of PPAR α/γ pathway.

Exploring maternal and developmental toxicity of perfluoroalkyl ether acids PFO4DA and PFO5DoA using hepatic transcriptomics and serum metabolomics

Production of per- and polyfluoroalkyl substances (PFAS) has shifted from long-chain perfluoroalkyl acids to short-chain compounds and those with ether bonds in the carbon chain. Next-generation perfluoroalkylether PFAS include HFPO-DA (“GenX chemicals”), Nafion Byproducts, and the PFOx homologous series that includes perfluoro-3,5,7,9-butaoxadecanoic acid (PFO4DA) and perfluoro-3,5,7,9,11-pentaoxadodecanoic acid (PFO5DoA). PFO4DA and PFO5DoA have been detected in serum and/or tissues from humans and wildlife proximal to contamination point sources. However, toxicity data are extremely limited, with no in vivo developmental toxicology data. To address these data gaps, pregnant Sprague-Dawley rats were exposed via oral gavage to vehicle, PFO4DA, or PFO5DoA across a series of doses (0.1 to 62.5 mg/kg/day) from gestation day (GD) 18–22. Hepatic transcriptomics were assayed in dams and fetuses, and serum metabolomics in dams. These data were overlaid with serum PFO4DA and PFO5DoA concentrations to perform dose-response modeling. Both dams and fetuses exhibited dose-responsive disruption of hepatic gene expression in response to PFO4DA or PFO5DoA, with fetal expression disrupted at lower doses than dams. Several differentially expressed genes were upregulated by every dose of PFO5DoA in both maternal and fetal samples, including genes encoding enzymes that hydrolyze acyl-coA to free fatty acids. Maternal serum metabolomics revealed PFO4DA exposure did not induce significant changes at any tested dose, whereas PFO5DoA exposure resulted in dose-dependent differential metabolite abundance for 149 unique metabolites. Multi-omics pathway analyses of integrated maternal liver transcriptomics and serum metabolomics revealed significant convergent changes as low as 3 mg/kg/d PFO4DA and 0.3 mg/kg/d PFO5DoA exposure. Overall, transcriptomic and metabolomic effects of PFO4DA and PFO5DoA appear consistent with other carboxylic acid PFAS, with primary changes related to lipid metabolism, bile acids, cholesterol, and cellular stress. Importantly, PFO5DoA exposure more potently induced changes in maternal and fetal hepatic gene expression and maternal circulating metabolites, despite high structural similarity. Further, we report in vitro PPARα and PPARγ receptor activation for both compounds as putative molecular mechanisms. This work demonstrates the potential developmental toxicity of alternative moiety perfluoroethers and highlights the developing liver as particularly vulnerable to transcriptomic disruption.Synopsis: Developmental exposure to fluoroether carboxylic acids PFO4DA and PFO5DoA result in differential impacts on hepatic transcriptome in dams and offspring and circulating metabolome in dams, with PFO5DoA exhibiting higher potency than PFO4DA.

OS01-10 Development of a QSAR model for predicting PPARα activation by PFAS based on human in vitro data

OS01-10 Development of a QSAR model for predicting PPARα activation by PFAS based on human in vitro data

PPAR-α Insufficiency Enhances Doxorubicin-Induced Nephropathy in PPAR-α Knockout Mice and a Murine Podocyte Cell Line.

Peroxisome proliferator-activated receptor-alpha (PPAR-α) and its exogenous activators (fibrates) promote autophagy. However, whether the deleterious effects of PPAR-α deficiency on doxorubicin (DOX)-induced podocytopathy are associated with reduced autophagy remains to be clarified. We investigated the mechanisms of PPAR-α in DOX-induced podocytopathy and tubular injury in PPAR-α knockout (PAKO) mice and in a murine podocyte cell line. DOX-treated PAKO mice showed higher serum levels of triglycerides and non-esterified fatty acids and more severe podocytopathy than DOX-treated wild-type mice, as evidenced by higher urinary levels of proteins and podocalyxin at 3 days to 2 weeks and higher blood urea nitrogen and serum creatinine levels at 4 weeks. Additionally, there was an increased accumulation of p62, a negative autophagy marker, in the glomerular and tubular regions in DOX-treated PAKO mice at Day 9. Moreover, DOX-treated PAKO mice showed more severe glomerulosclerosis and tubular damage and lower podocalyxin expression in the kidneys than DOX-treated control mice at 4 weeks. Furthermore, DOX treatment increased p-p53, an apoptosis marker, and cleaved the caspase-3 levels and induced apoptosis, which was ameliorated by fenofibrate, a PPAR-α activator. Fenofibrate further enhanced AMPK activation and autophagy under fed and fasting conditions. Conclusively, PPAR-α deficiency enhances DOX-induced podocytopathy, glomerulosclerosis, and tubular injury, possibly by reducing autophagic activity in mouse kidneys.

Endoplasmic reticulum stress induces hepatic steatosis through interaction between PPARα and FoxO6 in vivo and in vitro

Endoplasmic reticulum (ER) stress is a major cause of hepatic steatosis through increasing de novo lipogenesis. Forkhead box O6 (FoxO6) is a transcription factor mediating insulin signaling to glucose and lipid metabolism. Therefore, dysregulated FoxO6 is involved in hepatic lipogenesis. This study elucidated the role of FoxO6 in ER stress–induced hepatic steatosis in vivo and in vitro. Hepatic ER stress responses and β-oxidation were monitored in mice overexpressed with constitutively active FoxO6 allele and FoxO6-null mice. For the in vitro study, liver cells overexpressing constitutively active FoxO6 and FoxO6-siRNA were treated with high glucose, and lipid metabolism alterations were measured. ER stress–induced FoxO6 activation suppressed hepatic β-oxidation in vivo. The expression and transcriptional activity of peroxisome proliferator-activated receptor α (PPARα) were significantly decreased in the constitutively active FoxO6 allele. Otherwise, inhibiting β-oxidation genes were reduced in the FoxO6-siRNA and FoxO6-KO mice. Our data showed that the FoxO6-induced hepatic lipid accumulation was negatively regulated by insulin signaling. High glucose treatment as a hyperglycemia condition caused the expression of ER stress–inducible genes, which was deteriorated by FoxO6 activation in liver cells. However, high glucose-mediated ER stress suppressed β-oxidation gene expression through interactions between PPARα and FoxO6 corresponding to findings in the in vivo study—lipid catabolism is also regulated by FoxO6. Furthermore, insulin resistance suppressed b-oxidation through the interaction between FoxO6 and PPARα promotes hepatic steatosis, which, due to hyperglycemia-induced ER stress, impairs insulin signaling.Key messagesOur original aims were to delineate the interrelation between the regulation of PPARα and the transcription factor FoxO6 pathway in relation to lipid metabolism at molecular levels.Evidence on high glucose promoted FoxO6 activation induced lipid accumulation in liver cells.The effect of PPARα activation of the insulin signaling.FoxO6 plays a pivotal role in hepatic lipid accumulation through inactivation of PPARα in FoxO6-overexpression mice.

Patient-derived colon epithelial organoids reveal lipid-related metabolic dysfunction in pediatric ulcerative colitis.

Ulcerative colitis (UC) is associated with epithelial metabolic derangements which exacerbate gut inflammation. Patient-derived organoids recapitulate complexities of the parent tissue in health and disease; however, whether colon organoids (colonoids) model the metabolic impairments in the pediatric UC epithelium is unclear. Here, we developed colonoid lines from pediatric patients with endoscopically active UC, inactive UC, and those without endoscopic or histologic evidence of colon inflammation (non-IBD controls) to interrogate functional metabolic differences in the colon epithelia. We demonstrate that colonoids from active UC patients exhibit hypermetabolic features and cellular stress, specifically during differentiation. Hypermetabolism in differentiating active UC colonoids was driven, in part, by increased proton leak, and supported by enhanced glycolytic capacity and dysregulated neutral lipid accumulation. Transcriptomic and pathway analyses indicated a role for PPAR-α in lipid-induced hypermetabolism in aUC colonoids, which was validated by PPAR-α activation in non-IBD colonoids. Accordingly, limiting neutral lipid accumulation in active UC colonoids through pharmacological inhibition of PPAR-α induced a metabolic shift towards glucose utilization, suppressed hypermetabolism and chemokine secretion, and improved markers of cellular stress and epithelial differentiation. Taken together, we reveal a role for lipid-related metabolic dysfunction in the pediatric UC epithelium and support the advancement of colonoids as a preclinical human model for testing epithelial-directed therapies against such metabolic dysfunction.

IGFBP1 promotes the proliferation and migration of lung adenocarcinoma cells through the PPARα pathway

BackgroundThe immune status is closely linked to cancer progression, metastasis, and prognosis. Lipid metabolism, crucial for reshaping immune status, plays a key role in regulating the advancement of lung adenocarcinoma (LUAD) and deserves further investigation. MethodsThis study classifies LUAD patients into different immune subtypes based on lipid metabolism-related genes and compares the clinical characteristics among these subtypes. Single-multi COX analysis screens out key genes related to prognosis, and a risk feature and prognostic model are constructed. Cell cloning, scratch, transwell, western blotting and flow cytometry cell cycle analysis to detect the function of key genes. A subcutaneous tumor animal model is used to investigate the in vivo function and molecular mechanisms of key genes. ResultsLUAD patients are classified into three immune subtypes, among which C3 subtype has lower immune status and higher frequency of gene mutations, and show lower immunoreactivity in immunotherapy. COX analysis identified a prognostic model for four lipid metabolism factors (IGFBP1, NR0B2, PPARA, and POMC). IGFBP1, a core gene in this model, is highly expressed in the C3 subtype. Functionally, knocking down IGFBP1 significantly inhibits tumor cell cloning, scratch, and migration abilities, and downregulates the expression of cell cycle and EMT-related proteins. Knocking down IGFBP1 significantly inhibits tumor burden (P < 0.05). Mechanistically, knocking down IGFBP1 inhibits the activation of PPARα to regulate tumor cell growth. ConclusionsThis study found that lipid metabolism genes are closely related to LUAD, and IGFBP1 may be a key gene in regulating tumor growth and development.

Perfluorohexanesulfonic Acid (PFHxS) Impairs Lipid Homeostasis in Zebrafish Larvae through Activation of PPARα.

Perfluorohexanesulfonic acid (PFHxS), an emerging short-chain per- and polyfluoroalkyl substance, has been frequently detected in aquatic environments. Adverse outcome pathway studies have shown that perfluorinated compounds impair lipid homeostasis through peroxisome proliferator activated receptors (PPARs). However, many of these studies were performed at high concentrations and may thus be a result of overt toxicity. To better characterize the molecular and key events of PFHxS to biota, early life-stage zebrafish (Danio rerio) were exposed to concentrations detected in the environment (0.01, 0.1, 1, and 10 μg/L). Lipidomic and transcriptomic evaluations were integrated to predict potential molecular targets. PFHxS significantly impaired lipid homeostasis by the dysregulation of glycerophospholipids, fatty acyls, glycerolipids, sphingolipids, prenol lipids, and sterol lipids. Informatic analyses of the lipidome and transcriptome indicated alterations of the PPAR signaling pathway, with downstream changes to retinol, linoleic acid, and glycerophospholipid metabolism. To assess the role of PPARs, potential binding of PFHxS to PPARs was predicted and animals were coexposed to a PPAR antagonist (GW6471). Molecular simulation indicated PFHxS had a 27.1% better binding affinity than oleic acid, an endogenous agonist of PPARα. Antagonist coexposures rescued impaired glycerophosphocholine concentrations altered by PFHxS. These data indicate PPARα activation may be an important molecular initiating event for PFHxS.

The Loss of PPARγ Expression and Signaling Is a Key Feature of Cutaneous Actinic Disease and Squamous Cell Carcinoma: Association with Tumor Stromal Inflammation.

Given the importance of peroxisome proliferator-activated receptor (PPAR)-gamma in epidermal inflammation and carcinogenesis, we analyzed the transcriptomic changes observed in epidermal PPARγ-deficient mice (Pparg-/-epi). A gene set enrichment analysis revealed a close association with epithelial malignancy, inflammatory cell chemotaxis, and cell survival. Single-cell sequencing of Pparg-/-epi mice verified changes to the stromal compartment, including increased inflammatory cell infiltrates, particularly neutrophils, and an increase in fibroblasts expressing myofibroblast marker genes. A comparison of transcriptomic data from Pparg-/-epi and publicly available human and/or mouse actinic keratoses (AKs) and cutaneous squamous cell carcinomas (SCCs) revealed a strong correlation between the datasets. Importantly, PPAR signaling was the top common inhibited canonical pathway in AKs and SCCs. Both AKs and SCCs also had significantly reduced PPARG expression and PPARγ activity z-scores. Smaller reductions in PPARA expression and PPARα activity and increased PPARD expression but reduced PPARδ activation were also observed. Reduced PPAR activity was also associated with reduced PPARα/RXRα activity, while LPS/IL1-mediated inhibition of RXR activity was significantly activated in the tumor datasets. Notably, these changes were not observed in normal sun-exposed skin relative to non-exposed skin. Finally, Ppara and Pparg were heavily expressed in sebocytes, while Ppard was highly expressed in myofibroblasts, suggesting that PPARδ has a role in myofibroblast differentiation. In conclusion, these data provide strong evidence that PPARγ and possibly PPARα represent key tumor suppressors by acting as master inhibitors of the inflammatory changes found in AKs and SCCs.

Azologs of the Fatty Acid Mimetic Drug Cinalukast Enable Light-Induced PPARα Activation.

Photo-switchable nuclear receptor modulators ("photohormones") enable spatial and temporal control over transcription factor activity and are valuable precision tools for biological studies. We have developed a new photohormone chemotype by incorporating a light-switchable motif in the scaffold of a cinalukast-derived PPARα ligand and tuned light-controlled activity by systematic structural variation. An optimized photohormone exhibited PPARα agonism in its light-induced (Z)-configuration and strong selectivity over related lipid-activated transcription factors representing a valuable addition to the collection of light-controlled tools to study nuclear receptor activity.