4-phenylbutyric acid improves sepsis-induced cardiac dysfunction by modulating amino acid metabolism and lipid metabolism via Comt/Ptgs2/Ppara.

INTRODUCTION: Cardiac dysfunction after sepsis the most common and severe sepsis-related organ failure. The severity of cardiac damage in sepsis patients was positively associated to mortality. It is important to look for drugs targeting sepsis-induced cardiac damage. Our previous studies found that 4-phenylbutyric acid (PBA) was beneficial to septic shock by improving cardiovascular function and survival, while the specific mechanism is unclear. OBJECTIVES: We aimed to explore the specific mechanism and PBA for protecting cardiac function in sepsis. METHODS: The cecal ligation and puncture-induced septic shock models were used to observe the therapeutic effects of PBA on myocardial contractility and the serum levels of cardiac troponin-T. The mechanisms of PBA against sepsis were explored by metabolomics and network pharmacology. RESULTS: The results showed that PBA alleviated the sepsis-induced cardiac damage. The metabolomics results showed that there were 28 metabolites involving in the therapeutic effects of PBA against sepsis. According to network pharmacology, 11 hub genes were found that were involved in lipid metabolism and amino acid transport following PBA treatment. The further integrated analysis focused on 7 key targets, including Comt, Slc6a4, Maoa, Ppara, Pparg, Ptgs2 and Trpv1, as well as their core metabolites and pathways. In an in vitro assay, PBA effectively inhibited sepsis-induced reductions in Comt, Ptgs2 and Ppara after sepsis. CONCLUSIONS: PBA protects sepsis-induced cardiac injury by targeting Comt/Ptgs2/Ppara, which regulates amino acid metabolism and lipid metabolism. The study reveals the complicated mechanisms of PBA against sepsis.

Chrysin attenuates estradiol-induced endometrial hyperplasia in rats via enhancing PPARα activity.

Endometrial hyperplasia (EH) is a complex condition that commonly affects women after menopause. Since the current available treatments for EH are mainly invasive, there is a need for developing new treatment modalities. Chrysin (Ch) is a dihydroxyflavone with numerous promising therapeutic potentials. In this study, Ch's protective effects on estradiol (E2)-induced EH were studied in rats. Animals were allocated randomly to five groups and were treated for 4 weeks as follows: Group 1, control: received the vehicle; group 2, Ch: received Ch 25 mg/kg; group 3, estradiol (E2): received E2 (3 mg/kg) 3 × weekly subcutaneously and the vehicle. Group 4, E2 + Ch 10 mg/kg and group 5, E2 + Ch 25 mg/kg: Ch was given once daily at 10 mg/kg or 25 mg/kg, respectively. In addition, E2 was administered 3 × weekly (3 mg/kg) in groups 4 and 5. Ch inhibited the E2-induced increase in uterine weights and histopathological changes. Ch lowered the cyclin D1 expression. Ch raised the caspase-3 content and Bax mRNA expression. Furthermore, it corrected the raised Bcl2 mRNA expression due to E2. Ch inhibited MDA accumulation and GSH depletion. It also prevents E2-induced SOD and GPx exhaustion. It also ameliorated the rise in NFκB, TNF-α, and IL-6 expression. These effects were correlated with an enhanced PPARα activity ratio relative to the E2 group. This suggests that Ch attenuates EH in this model by exerting anti-proliferative, anti-oxidant, and anti-inflammatory effects partially through increasing PPARα activity.

The anti-aging effect of velvet antler polypeptide is dependent on modulation of the gut microbiota and regulation of the PPARα/APOE4 pathway.

We investigated the anti-aging effects of velvet antler polypeptide on D-galactose (D-gal)-induced aging mice. D-gal-induced aging mice were established and randomly divided into five groups, the control, model, vitamin E (VE), velvet antler polypeptide low-dose and velvet antler polypeptide high-dose groups. The Morris water maze test was used to evaluate the learning and memory abilities of aging mice. Hippocampal neurons were observed via hematoxylin-eosin staining and transmission electron microscopy. Biochemical methods were used to detect the activities of superoxide dismutase, malonaldehyde and other enzymes and evaluate the influence of velvet antler polypeptide on the antioxidant capacity of aging mice. Using 16S rRNA gene sequencing and meristem technology, we assessed the effect of velvet antler polypeptide on aging mice's intestinal flora and fatty acid metabolism. The experimental results showed that velvet antler polypeptide could significantly improve aging mice's learning and cognitive abilities, increase the activities of superoxide dismutase, glutathione peroxidase, and catalase in the serum decrease the malonaldehyde content. Intestinal microecological analysis showed that velvet antler polypeptide could significantly increase the beneficial bacterial genus Lactobacillus abundance. Western blot analysis further demonstrated that velvet antler polypeptide could promote fatty acid metabolism by activating peroxisome proliferator-activated receptor α (PPARα) and upregulating the expression of the downstream enzymes carnitine-palmitoyl transferase-1 A and acyl-CoA oxidase 1 while downregulating that of apolipoprotein E4 (APOE4), thereby reducing fatty acid accumulation and increasing adenosine-triphosphate (ATP) production. Therefore, velvet antler polypeptide improves the intestinal microecology and activates the PPARα/APOE4 pathway to regulate fatty acid metabolism.

Anti-influenza A Virus Effects and Mechanisms of Emodin and Its Analogs via Regulating PPARα/γ-AMPK-SIRT1 Pathway and Fatty Acid Metabolism.

The peroxisome proliferator-activated receptor (PPAR) α/γ-adenosine 5'-monophosphate- (AMP-) activated protein kinase- (AMPK-) sirtuin-1 (SIRT1) pathway and fatty acid metabolism are reported to be involved in influenza A virus (IAV) replication and IAV-pneumonia. Through a cell-based peroxisome proliferator responsive element- (PPRE-) driven luciferase bioassay, we have investigated 145 examples of traditional Chinese medicines (TCMs). Several TCMs, such as Polygonum cuspidatum, Rheum officinale Baillon, and Aloe vera var. Chinensis (Haw.) Berg., were found to possess high activity. We have further detected the anti-IAV activities of emodin (EMO) and its analogs, a group of common important compounds of these TCMs. The results showed that emodin and its several analogs possess excellent anti-IAV activities. The pharmacological tests showed that emodin significantly activated PPARα/γ and AMPK, decreased fatty acid biosynthesis, and increased intracellular ATP levels. Pharmaceutical inhibitors, siRNAs for PPARα/γ and AMPKα1, and exogenous palmitate impaired the inhibition of emodin. The in vivo test also showed that emodin significantly protected mice from IAV infection and pneumonia. Pharmacological inhibitors for PPARα/γ and AMPK signal and exogenous palmitate could partially counteract the effects of emodin in vivo. In conclusion, emodin and its analogs are a group of promising anti-IAV drug precursors, and the pharmacological mechanism of emodin is linked to its ability to regulate the PPARα/γ-AMPK pathway and fatty acid metabolism.

Effects of pemafibrate on glucose metabolism markers and liver function tests in patients with hypertriglyceridemia: a pooled analysis of six phase 2 and phase 3 randomized double-blind placebo-controlled clinical trials.

BACKGROUND: Increased risk of cardiovascular events is associated not only with dyslipidemias, but also with abnormalities in glucose metabolism and liver function. This study uses pooled analysis to explore the in-depth effects of pemafibrate, a selective peroxisome proliferator-activated receptor α modulator (SPPARMα) already known to decrease elevated triglycerides, on glucose metabolism and liver function in patients with hypertriglyceridemia. METHODS: We performed a post-hoc analysis of six phase 2 and phase 3 Japanese randomized double-blind placebo-controlled trials that examined the effects of daily pemafibrate 0.1 mg, 0.2 mg, and 0.4 mg on glucose metabolism markers and liver function tests (LFTs). Primary endpoints were changes in glucose metabolism markers and LFTs from baseline after 12 weeks of pemafibrate treatment. All adverse events and adverse drug reactions were recorded as safety endpoints. RESULTS: The study population was 1253 patients randomized to placebo (n = 298) or pemafibrate 0.1 mg/day (n = 127), 0.2 mg/day (n = 584), or 0.4 mg/day (n = 244). Participant mean age was 54.3 years, 65.4 % had BMI ≥ 25 kg/m2, 35.8 % had type 2 diabetes, and 42.6 % had fatty liver. Fasting glucose, fasting insulin, and HOMA-IR decreased significantly in all pemafibrate groups compared to placebo. The greatest decrease was for pemafibrate 0.4 mg/day: least square (LS) mean change from baseline in fasting glucose - 0.25 mmol/L; fasting insulin - 3.31 µU/mL; HOMA-IR - 1.28. ALT, γ-GT, ALP, and total bilirubin decreased significantly at all pemafibrate doses vs. placebo, with the greatest decrease in the pemafibrate 0.4 mg/day group: LS mean change from baseline in ALT - 7.6 U/L; γ-GT - 37.3 U/L; ALP - 84.7 U/L; and total bilirubin - 2.27 µmol/L. Changes in HbA1c and AST did not differ significantly from placebo in any pemafibrate groups in the overall study population. The decreases from baseline in LFTs and glucose metabolism markers except for HbA1c were notable among patients with higher baseline values. FGF21 increased significantly in all pemafibrate groups compared to placebo, with the greatest increase in the pemafibrate 0.4 mg/day group. Adverse event rates were similar in all groups including placebo. CONCLUSIONS: In patients with hypertriglyceridemia, pemafibrate can improve glucose metabolism and liver function, and increase FGF21, without increasing adverse event risk.

Nanoparticle conjugation of ginsenoside Rb3 inhibits myocardial fibrosis by regulating PPARα pathway.

BACKGROUND: Cardiac fibrosis occurs in ischemic and non-ischemic heart failure, hereditary cardiomyopathy, diabetes and aging. Energy metabolism, which serves a crucial function in the course and treatment of cardiovascular diseases, might have therapeutic benefits for myocardial fibrosis. Ginsenoside Rb3 (G-Rb3) is one of the main components of Ginseng and exhibits poor oral bioavailability but still exerts regulate energy metabolism effects in some diseases. Therefore, the study investigated the effect of chitosan (CS) @ sodium tripolyphosphate (TPP) nanoparticles conjugation with ginsenoside Rb3 (NpRb3) on myocardial fibrosis and studied its possible mechanisms. The results showed that NpRb3 directly participates in the remodeling of myocardial energy metabolism and the regulation of perixisome proliferation-activated receptor alpha (PPARα), thereby improving the degree of myocardial fibrosis. The study also verifies the protective effect of NpRb3 on energy metabolism and mitochondrial function by targeting the PPARα pathway. Therefore, the prepared nanodrug carrier may be a potential solution for the delivery of G-Rb3, which is a promising platform for oral treatment of myocardial fibrosis.

Tenofovir-disoproxil-fumarate modulates lipid metabolism via hepatic CD36/PPAR-alpha activation in hepatitis B virus infection.

BACKGROUND: Entecavir and tenofovir-disoproxil-fumarate are first-line nucleos(t)ide analogs (NA) for treatment of hepatitis B virus (HBV) infections; however, their long-term administration can impact extrahepatic organs. Herein, we sought to examine the effect of NA on lipid metabolism while also characterizing the associated mechanism. METHODS: A retrospective study was performed on HBV patients administered entecavir or tenofovir-disoproxil-fumarate. Patient clinical information, as well as their preserved serum samples obtained at baseline and 6-12 months after treatment initiation, were analyzed. A 1:1 propensity score matching was applied to the assignment of tenofovir-disoproxil-fumarate or entecavir treatment. Changes in serum cholesterol, including oxidized-LDL, were analyzed. Subsequently, in vitro analysis elucidated the mechanism associated with the effect of NAs on lipid metabolism. RESULTS: Administration of tenofovir-disoproxil-fumarate, not entecavir, to chronic HBV patients, decreased serum cholesterol levels, including non-HDL and oxidized-LDL, which are strongly associated with arteriosclerosis. In vitro analysis revealed that tenofovir-disoproxil-fumarate reduced supernatant cholesterol, and upregulated the scavenger receptor, CD36, in hepatocytes. Meanwhile, silencing of hepatic CD36 increased supernatant cholesterol and negated the cholesterol-reducing effect of tenofovir-disoproxil-fumarate in HepG2-cells. Reporter, microarray, and RT-PCR analyses further revealed that tenofovir-disoproxil-fumarate treatment activates PPAR-α-mediated signaling, and upregulates PPAR-α target genes, including CPT1 and CD36. Alternatively, silencing of PPAR-α reversed the effects of tenofovir-disoproxil-fumarate on CD36. CONCLUSIONS: Tenofovir-disoproxil-fumarate modulates lipid metabolism by upregulating hepatic CD36 via PPAR-α activation. Since dyslipidemia could be associated with arteriosclerosis and hepatocarcinogenesis, these discoveries provide novel insights into anti-HBV therapies, as well as the associated extrahepatic effects of NA.

Marked effects of novel selective peroxisome proliferator-activated receptor α modulator, pemafibrate in severe hypertriglyceridemia: preliminary report.

BACKGROUND: Currently available treatments have only been partly successful in patients with severe hypertriglyceridemia, including those with high serum triglycerides above 1,000 mg/dL (11.3 mmol/L), who often suffer from acute pancreatitis. Pemafibrate is a novel selective peroxisome proliferator-activated receptor α modulator (SPPARMα) which has been developed as an affordable oral tablet in Japan. We herein report the first three patients with severe hypertriglyceridemia who were successfully treated with pemafibrate. METHODS: Three patients with fasting serum triglyceride (TG) levels above 1,000 mg/dL (11.3 mmol/L) were treated with pemafibrate (0.2-0.4 mg/day, 0.1-0.2 mg BID). RESULTS: Serum TGs decreased from 2,000-3,000 mg/dL (22.6-33.9 mmol/L) to < 250 mg/dL (2.8 mmol/L) without adverse effects in all three patients. Serum TGs in Patient 1 and 2 decreased from 1,326 mg/dL (15.0 mmol/L) to 164 mg/dL (1.9 mmol/L) and from 2,040 mg/dL (23.1 mmol/L) to 234 mg/dL (2.6 mmol/L), respectively. Patient 3 with type 2 diabetes and 12.1% (109 mmol/mol) hemoglobin A1c had a TG level of 2,300 mg/dL (26.0 mmol/L). Even after glycemic control improved, TG remained high. After pemafibrate administration, TG decreased to 200 mg/dL (2.3 mmol/L). All patients showed no serious adverse events. CONCLUSIONS: Pemafibrate demonstrated potential efficacy and safety for severe hypertriglyceridemia which may contribute to the prevention of acute pancreatitis, in a manner that can be easily prescribed and used as an oral tablet.

MiR-21 promotes calcium oxalate-induced renal tubular cell injury by targeting PPARA.

Kidney stone disease is a crystal concretion formed in the kidneys that has been associated with an increased risk of chronic kidney disease. MicroRNAs are functionally involved in kidney injury. Data mining using a microRNA array database suggested that miR-21 may be associated with calcium oxalate monohydrate (COM)-induced renal tubular cell injury. Here, we confirmed that COM exposure significantly upregulated miR-21 expression, inhibited proliferation, promoted apoptosis, and caused lipid accumulation in an immortalized renal tubular cell line (HK-2). Moreover, inhibition of miR-21 enhanced proliferation and decreased apoptosis and lipid accumulation in HK-2 cells upon COM exposure. In a glyoxylate-induced mouse model of renal calcium oxalate deposition, increased miR-21 expression, lipid accumulation, and kidney injury were also observed. In silico analysis and subsequent experimental validation confirmed the peroxisome proliferator-activated receptor (PPAR)-α gene (PPARA) a key gene in fatty acid oxidation, as a direct miR-21 target. Suppression of miR-21 by miRNA antagomiR or activation of PPAR-α by its selective agonist fenofibrate significantly reduced renal lipid accumulation and protected against renal injury in vivo. In addition, miR-21 was significantly increased in urine samples from patients with calcium oxalate renal stones compared with healthy volunteers. In situ hybridization of biopsy samples from patients with nephrocalcinosis revealed that miR-21 was also significantly upregulated compared with normal kidney tissues from patients with renal cell carcinoma who underwent radical nephrectomy. These results suggested that miR-21 promoted calcium oxalate-induced renal tubular cell injury by targeting PPARA, indicating that miR-21 could be a potential therapeutic target and biomarker for nephrolithiasis.

Gut-liver axis modulation in fructose-fed mice: a role for PPAR-alpha and linagliptin.

Fructose dietary intake affects the composition of the intestinal microbiota and influences the development of hepatic steatosis. Endotoxins produced by gram-negative bacteria alter intestinal permeability and cause bacterial translocation. This study evaluated the effects of gut microbiota modulation by a purified PPAR-alpha agonist (WY14643), a DPP-4 inhibitor (linagliptin), or their association on intestinal barrier integrity, endotoxemia, and hepatic energy metabolism in high-fructose-fed C57BL/6 mice. Fifty mice were divided to receive the control diet (C group) or the high-fructose diet (HFRU) for 12 weeks. Subsequently, the HFRU group was divided to initiate the treatment with PPAR-alpha agonist (3.5 mg/kg/BM) and DPP-4 inhibitor (15 mg/kg/BM). The HFRU group had glucose intolerance, endotoxemia, and dysbiosis (with increased Proteobacteria) without changes in body mass in comparison with the C group. HFRU group showed damaged intestinal ultrastructure, which led to liver inflammation and marked hepatic steatosis in the HFRU group when compared to the C group. PPAR-alpha activation and DPP-4 inhibition countered glucose intolerance, endotoxemia, and dysbiosis, ameliorating the ultrastructure of the intestinal barrier and reducing Tlr4 expression in the liver of treated animals. These beneficial effects suppressed lipogenesis and mitigated hepatic steatosis. In conclusion, the results herein propose a role for PPAR-alpha activation, DPP-4 inhibition, and their association in attenuating hepatic steatosis by gut-liver axis modulation in high-fructose mice model. These observations suggest these treatments as potential targets to treat hepatic steatosis and avoid its progression.

The role of PPARα in autosomal dominant polycystic kidney disease.

PURPOSE OF REVIEW: Metabolic reprogramming is a prominent feature of cyst epithelial cells in autosomal dominant polycystic kidney disease (ADPKD). Peroxisome proliferator activated receptor alpha (PPARα) is a transcription factor that regulates many aspects of cellular metabolism. The purpose of this review is to understand the role of PPARα in ADPKD. RECENT FINDINGS: PPARα expression is reduced in ADPKD kidneys of mice and humans. This downregulation is in part secondary to microRNA mediated translational repression and leads to impairment of fatty acid metabolism. Genetic studies demonstrate that deletion of Pparα aggravates cyst growth in a slowly progressive mouse model of ADPKD. Recent studies also show that administration of Pparα agonists ameliorates cyst burden in mice. SUMMARY: Abnormal reduction of PPARα affects cellular metabolism in ADPKD. Pparα is a modulator of cyst progression in mouse models of ADPKD. These studies establish PPARα as an exciting new drug target for the treatment of individuals with ADPKD.

NIK links inflammation to hepatic steatosis by suppressing PPARα in alcoholic liver disease.

Background: Inflammation and steatosis are the main pathological features of alcoholic liver disease (ALD), in which, inflammation is one of the critical drivers for the initiation and development of alcoholic steatosis. NIK, an inflammatory pathway component activated by inflammatory cytokines, was suspected to link inflammation to hepatic steatosis during ALD. However, the underlying pathogenesis is not well-elucidated. Methods: Alcoholic steatosis was induced in mice by chronic-plus-binge ethanol feeding. Both the loss- and gain-of-function experiments by the hepatocyte-specific deletion, pharmacological inhibition and adenoviral transfection of NIK were utilized to elucidate the role of NIK in alcoholic steatosis. Rate of fatty acid oxidation was assessed in vivo and in vitro. PPARα agonists or antagonists of MEK1/2 and ERK1/2 were used to identify the NIK-induced regulation of PPARα, MEK1/2, and ERK1/2. The potential interactions between NIK, MEK1/2, ERK1/2 and PPARα and the phosphorylation of PPARα were clarified by immunoprecipitation, immunoblotting and far-western blotting analysis. Results: Hepatocyte-specific deletion of NIK protected mice from alcoholic steatosis by sustaining hepatic fatty acid oxidation. Moreover, overexpression of NIK contributed to hepatic lipid accumulation with disrupted fatty acid oxidation. The pathological effect of NIK in ALD may be attributed to the suppression of PPARα, the main controller of fatty acid oxidation in the liver, because PPARα agonists reversed NIK-mediated hepatic steatosis and malfunction of fatty acid oxidation. Mechanistically, NIK recruited MEK1/2 and ERK1/2 to form a complex that catalyzed the inhibitory phosphorylation of PPARα. Importantly, pharmacological intervention against NIK significantly attenuated alcoholic steatosis in ethanol-fed mice. Conclusions: NIK targeting PPARα via MEK1/2 and ERK1/2 disrupts hepatic fatty acid oxidation and exhibits high value in ALD therapy.

Assessment of the Mode of Action Underlying the Effects of GenX in Mouse Liver and Implications for Assessing Human Health Risks.

GenX is an alternative to environmentally persistent long-chain perfluoroalkyl and polyfluoroalkyl substances. Mice exposed to GenX exhibit liver hypertrophy, elevated peroxisomal enzyme activity, and other apical endpoints consistent with peroxisome proliferators. To investigate the potential role of peroxisome proliferator-activated receptor alpha (PPARα) activation in mice, and other molecular signals potentially related to observed liver changes, RNA sequencing was conducted on paraffin-embedded liver sections from a 90-day subchronic toxicity study of GenX conducted in mice. Differentially expressed genes were identified for each treatment group, and gene set enrichment analysis was conducted using gene sets that represent biological processes and known canonical pathways. Peroxisome signaling and fatty acid metabolism were among the most significantly enriched gene sets in both sexes at 0.5 and 5 mg/kg GenX; no pathways were enriched at 0.1 mg/kg. Gene sets specific to the PPARα subtype were significantly enriched. These findings were phenotypically anchored to histopathological changes in the same tissue blocks: hypertrophy, mitoses, and apoptosis. In vitro PPARα transactivation assays indicated that GenX activates mouse PPARα. These results indicate that the liver changes observed in GenX-treated mice occur via a mode of action (MOA) involving PPARα, an important finding for human health risk assessment as this MOA has limited relevance to humans.

Effect of pemafibrate, a novel selective peroxisome proliferator-activated receptor-alpha modulator (SPPARMα), on urinary protein excretion in IgA nephropathy with hypertriglyceridemia.

Lipid abnormalities, including hypertriglyceridemia, are one of the most common comorbidities in patients with chronic kidney disease (CKD) and are independently associated with disease progression. However, it remains uncertain whether treatment for hypertriglyceridemia has favorable effects on the clinical course of IgA nephropathy (IgAN). Pemafibrate is a novel selective peroxisome proliferator-activated receptor-alpha modulator and may be distinct from conventional fibrates in terms of its pharmacological activity and hepatic and renal safety. A recent clinical study demonstrated that pemafibrate was safe and effective for correcting pro-atherogenic lipid abnormalities in CKD patients with a wide range of renal insufficiency. However, the effect of pemafibrate on renal function in patients with IgAN and hypertriglyceridemia has not been verified. This paper is the first to show that 12 months of pemafibrate (0.1 mg daily) administration in three drug-naïve and mild IgAN patients with variable renal dysfunction and histopathology proven IgAN decreased serum triglyceride level and excretion of urinary protein and liver-type fatty acid-binding protein with no change in estimated glomerular filtration rate (eGFR). These findings suggest that pemafibrate is safe and effective for correcting hypertriglyceridemia and decreasing urinary protein excretion without changing eGFR and blood pressure levels in mild IgAN patients with hypertriglyceridemia.

NLRP3 Inflammasome Inhibition by MCC950 in Aged Mice Improves Health via Enhanced Autophagy and PPARα Activity.

The NLRP3 inflammasome has emerged as an important regulator of metabolic disorders and age-related diseases in NLRP3-deficient mice. In this article, we determine whether, in old mice C57BL6J, the NLRP3 inflammasome inhibitor MCC950 is able to attenuate age-related metabolic syndrome to providing health benefits. We report that MCC950 attenuates metabolic and hepatic dysfunction in aged mice. In addition, MCC950 inhibited the Pi3K/AKT/mTOR pathway, enhanced autophagy, and activated peroxisome proliferator-activated receptor-α in vivo and in vitro. The data suggest that MCC950 mediates the protective effects by the mammalian target of rapamycin inhibition, thus activating autophagy and peroxisome proliferator-activated receptor-α. In conclusion, pharmacological inhibition of NLRP3 in aged mice has a significant impact on health. Thus, NLRP3 may be a therapeutic target of human age-related metabolic syndrome.

Activation of human nuclear receptors by perfluoroalkylated substances (PFAS).

Perfluoralkylated substances (PFAS) such as perfluorooctanoic acid (PFOA) or perfluorooctanesulfonic acid (PFOS) are used to produce, e.g., surface coatings with water- and dirt-repellent properties. These substances have been shown to be hepatotoxic in rodents, and the mechanism of action is mostly attributed to the PFAS-mediated activation of the peroxisome proliferator-activated receptor alpha (PPARα). In the present study, we investigated by using luciferase-based reporter gene assays whether PFOA, PFOS and six alternative PFAS can activate, in addition to PPARα, eight other human nuclear receptors. All tested PFAS except for perfluorobutanesulfonic acid (PFBS) were able to activate human PPARα. Perfluoro-2-methyl-3-oxahexanoic acid (PMOH) and 3H-perfluoro-3-[(3-methoxypropoxy) propanoic acid] (PMPP) were weak agonists of human PPARγ. The other human nuclear receptors (PPARδ, CAR, PXR, FXR, LXRα, RXRα and RARα) were not affected by any PFAS tested in this study. Although PMOH was more effective than PFOA in stimulating PPARα in the transactivation assay, it was less effective in stimulating PPARα-dependent target gene expression in human HepG2 hepatocarcinoma cells. Notably, any effect observed in this in vitro study only occurred at concentrations higher than 10 µM of the respective PFAS which is in all cases several magnitudes above the average blood concentration in the Western population. Thus, the results suggest that nuclear receptor activation may only play a minor role in potential PFAS-mediated adverse effects in humans.

PPARα/ß Activation Alleviates Age-Associated Renal Fibrosis in Sprague Dawley Rats.

Age-associated renal fibrosis is commonly observed, with a decline in renal function during aging. Although peroxisome proliferator-activated receptors α/ß (PPARα/ß) activation has been shown to exert beneficial effects on age-associated renal changes, its effects on age-associated renal fibrosis have not been investigated yet. Here, we show that the PPARα/ß activator, MHY2013, can significantly alter lipid metabolism in renal tubule epithelial cells and attenuate renal fibrosis in aged Sprague Dawley (SD) rats. We found that MHY2013 significantly increased nuclear translocation and activity of PPARα/ß in NRK52E renal epithelial cells. Moreover, the enhanced PPARα/ß activity increased the expression of fatty acid oxidation-associated PPARα/ß target genes. In addition, transforming growth factor-ß (TGF-ß)- and oleic acid-induced lipid accumulation and fibrosis-associated gene expression were decreased in NRK52E cells by MHY2013 pretreatment. To evaluate the effects of MHY2013 on age-associated renal fibrosis, aged SD rates were orally administered MHY2013 (1 and 5 mg/kg) daily for 1 month. MHY2013 efficiently increased PPARα/ß activation and reduced renal lipid accumulation in aged SD rat kidneys. Furthermore, renal fibrosis was significantly decreased by MHY2013, indicating the importance of renal lipid metabolism in age-associated renal fibrosis. Taken together, our results suggest that activation of PPARα/ß signaling during aging prevents age-associated renal fibrosis.

Resveratrol protects against nonalcoholic fatty liver disease by improving lipid metabolism and redox homeostasis via the PPARα pathway.

Resveratrol (RSV), a well-known bioactive compound, has been reported to exert a broad range of health benefits. Accumulating evidence suggests that RSV is beneficial for many metabolic diseases, including nonalcoholic fatty liver disease (NAFLD). This study investigated the preventive and therapeutic effects of RSV on high-fat diet (HFD)-induced NAFLD in rats and palmitate acid (PA)-induced hepatocyte steatosis in HepG2 cells. Hepatocytes were incubated with inhibitors of peroxisome proliferator-activated receptor α (PPARα) or short interfering RNAs (siRNAs) targeting PPARα, AMP-activated protein kinase (AMPK), and protein kinase A (PKA) to determine the underlying mechanisms. We found that RSV noticeably ameliorated HFD-induced hepatic steatosis in rats and inhibited PA-induced lipid accumulation in HepG2 cells. Moreover, RSV improved lipid metabolism, enhanced antioxidant capacity, and restored mitochondrial respiratory chain activities. Incubation with inhibitors of PPARα or PPARα siRNA abolished the protective effects of RSV on lipid metabolism and redox homeostasis. Furthermore, RSV activated the PKA/AMPK/PPARα signaling pathway. Our results provided direct evidence for a novel, PPARα-mediated mechanism responsible for the beneficial effects of RSV on hepatic steatosis. These findings may have important theoretical and application prospects for the prevention and treatment of NAFLD. Novelty RSV improved lipid metabolism and redox homeostasis and oxidative stress in NAFLD via the PKA/AMPK/PPARα signaling pathway. RSV may have a greater beneficial effect in the early prevention of hepatic steatosis.

Hypolipidemic effect of pure total flavonoids from peel of Citrus (PTFC) on hamsters of hyperlipidemia and its potential mechanism.

Citrus is a group of popular fruit that includes oranges, lemons, limes and grapefruit but research of its peel on hyperlipidemia and its mechanism is rare reported. We examined the effect of pure total flavonoids from peel of Citrus (PTFC), an extract from the peel of Citrus Changshan-huyou which is a popular fruit in China, on hamsters with hyperlipoidemia induced by high-fat diet (HFD). We found that PTFC significantly reduced levels of serum cholesterol (TC), triglyceride (TG) and low-density lipoprotein cholesterol (LDL-c) and improved levels of alanine transaminase (ALT), aspartate transaminase (AST) and Alkaline phosphatase (ALP) which associated with liver function in golden hamsters. Liver pathological results confirmed that the liver pathological section of golden hamster treated with PTFC was significantly improved compared with that of HFD group. The content of main cholesterol metabolic enzymes Cholesterol 7a-hydroxylase (CYP7A1) in liver was obviously recovered with PTFC treatment. Further studies shown that PTFC attenuated oxidative stress and free radical damage through superoxide dismutase (SOD) and malonyldialdehyde (MDA) tests and inflammatory injury by levels of Tumor Necrosis Factor-alpha (TNF-α) and interleukin-6 (IL-6) both in serum and hepatocyte of golden hamsters. Moreover, PTFC increased levels of RNA and protein expression of Peroxisome proliferator-activated receptor-α (PPAR-α) and PPAR-γ in liver, fat and skeletal muscle of hyperlipidemia golden hamster, significantly. Our results suggested that PTFC could play a hypolipidemic role through improvement of liver function by antioxidant and anti-inflammatory effects in hyperlipoidemia hamsters, its mechanism of action may through activating of PPARα and PPARγ.

Hippocampal PPARα is involved in the antidepressant-like effects of venlafaxine in mice.

Although thought as a serotonin and norepinephrine reuptake inhibitor (SNRI), the antidepressant mechanisms of venlafaxine remain unknown. Previous reports have shown the role of peroxisome proliferator activated receptor α (PPARα) in depression. In this study, we investigated whether the antidepressant-like effects of venlafaxine require PPARα. We first examined whether repeated venlafaxine administration reversed the effects of chronic unpredictable mild stress (CUMS) and chronic restraint stress (CRS) on PPARα in the hippocampus and medial prefrontal cortex (mPFC). Then, the pharmacologcial inhibitors of PPARα, GW6471 and MK886, were used to assay if the protecting effects of venlafaxine against chronic stress were prevented by PPARα blockade. Furthermore, gene knockdown of PPARα by AAV-PPARα-shRNA was also used. It was found that venlafaxine treatment fully restored the decreasing effects of CUMS and CRS on the hippocampal PPARα expression. Pharmacological inhibition of PPARα significantly attenuated the antidepressant-like effects of venlafaxine in mice. Moreover, gene knockdown of hippocampal PPARα also fully abolished the antidepressant-like actions of venlafaxine in mice. Collectively, hippocampal PPARα is an antidepressant target of venlafaxine.