Hypolipidemic drugs, polyunsaturated fatty acids, and eicosanoids are ligands for peroxisome proliferator-activated receptors alpha and delta

PPARβ/δ recruits NCOR and regulates transcription reinitiation of ANGPTL4

In the absence of ligands, the nuclear receptor PPARβ/δ recruits the NCOR and SMRT corepressors, which form complexes with HDAC3, to canonical target genes. Agonistic ligands cause dissociation of corepressors and enable enhanced transcription. Vice versa, synthetic inverse agonists augment corepressor recruitment and repression. Both basal repression of the target gene ANGPTL4 and reinforced repression elicited by inverse agonists are partially insensitive to HDAC inhibition. This raises the question how PPARβ/δ represses transcription mechanistically. We show that the PPARβ/δ inverse agonist PT-S264 impairs transcription initiation by decreasing recruitment of activating Mediator subunits, RNA polymerase II, and TFIIB, but not of TFIIA, to the ANGPTL4 promoter. Mass spectrometry identifies NCOR as the main PT-S264-dependent interactor of PPARβ/δ. Reconstitution of knockout cells with PPARβ/δ mutants deficient in basal repression results in diminished recruitment of NCOR, SMRT, and HDAC3 to PPAR target genes, while occupancy by RNA polymerase II is increased. PT-S264 restores binding of NCOR, SMRT, and HDAC3 to the mutants, resulting in reduced polymerase II occupancy. Our findings corroborate deacetylase-dependent and -independent repressive functions of HDAC3-containing complexes, which act in parallel to downregulate transcription.

Contribution of Palmitic Acid to Epidermal Morphogenesis and Lipid Barrier Formation in Human Skin Equivalents

The outermost barrier layer of the skin is the stratum corneum (SC), which consists of corneocytes embedded in a lipid matrix. Biosynthesis of barrier lipids occurs de novo in the epidermis or is performed with externally derived lipids. Hence, in vitro developed human skin equivalents (HSEs) are developed with culture medium that is supplemented with free fatty acids (FFAs). Nevertheless, the lipid barrier formation in HSEs remains altered compared to native human skin (NHS). The aim of this study is to decipher the role of medium supplemented saturated FFA palmitic acid (PA) on morphogenesis and lipid barrier formation in HSEs. Therefore, HSEs were developed with 100% (25 μM), 10%, or 1% PA. In HSEs supplemented with reduced PA level, the early differentiation was delayed and epidermal activation was increased. Nevertheless, a similar SC lipid composition in all HSEs was detected. Additionally, the lipid organization was comparable for lamellar and lateral organization, irrespective of PA concentration. As compared to NHS, the level of monounsaturated lipids was increased and the FFA to ceramide ratio was drastically reduced in HSEs. This study describes the crucial role of PA in epidermal morphogenesis and elucidates the role of PA in lipid barrier formation of HSEs.

The PPARδ Agonist GW501516 Improves Lipolytic/Lipogenic Balance through CPT1 and PEPCK during the Development of Pre-Implantation Bovine Embryos

The PPARs (peroxisome proliferator-activated receptors) play critical roles in the regulation of lipid and glucose metabolism. PPARδ, a member of the PPARs family, is associated with decreased susceptibility to ectopic lipid deposition and is implicated in the regulation of mitochondrial processes. The current study aimed to determine the role of PPARδ in fatty acid β-oxidation and its influence on PEPCK for the lipogenic/lipolytic balance during in vitro bovine oocyte maturation and embryo development. Activation of PPARδ by GW501516, but not 2-BP, was indicated by intact embryonic PEPCK (cytosolic) and CPT1 expression and the balance between free fatty acids and mitochondrial β-oxidation that reduced ROS and inhibited p-NF-κB nuclear localization. Genes involved in lipolysis, fatty acid oxidation, and apoptosis showed significant differences after the GW501516 treatment relative to the control- and 2-BP-treated embryos. GSK3787 reversed the PPARδ-induced effects by reducing PEPCK and CPT1 expression and the mitochondrial membrane potential, revealing the importance of PPARδ/PEPCK and PPARδ/CPT1 for controlling lipolysis during embryo development. In conclusion, GW501516-activated PPARδ maintained the correlation between lipolysis and lipogenesis by enhancing PEPCK and CPT1 to improve bovine embryo quality.

Herb-Drug Interactions and Hepatotoxicity

BACKGROUND

In recent times, herbals or phytomedicines have become very popular due to their global acceptance as a complementary and alternative remedy. While modern drugs are commercially available only after laboratory validations, clinical trials, as well as approval from drug regulatory authorities, majority of the marketed herbal products lack such scientific evidence of efficacy and safety. This results in herb or herb-drug interaction induced unfavorable clinical outcomes without crucial documentation on their temporal relations and concomitant use.

METHODS

An online literature search for peer-reviewed articles was conducted on the PubMed, Europe PMC, Medline and Google Scholar portals, using the phrases: complementary & alternative medicine, traditional Chinese medicine, herb-drug interaction, mechanisms of herb-drug interaction, herb-induced toxicity, herbal hepatotoxicity and causality, traditional medicine, viral hepatitis, etc.

Results

The retrieved data showed that globally, patients are attracted to herbal remedies with the misconception that these are completely safe and therefore, use them simultaneously with prescription drugs. Notably, there exists a potential risk of herb-drug interactions leading to some adverse side effects, including hepatotoxicity. The toxicological effect of a drug or herb is due to the inhibition of drug metabolizing enzymes (e.g., cytochrome P450), including interactions with certain prescription drugs through various mechanisms. Several cases of hepatotoxicity due to use of herbals in viral hepatitis-related liver diseases have been recently reported. However, limited experimental data and clinical evidence on herbal pharmacokinetics hamper the evaluation and reporting of adverse reactions and the underlying mechanisms.

CONCLUSION

Herb-drug interaction related morbidity is thus an emerging serious public health issue with broad implications for clinicians, pharmaceutical industries and health authorities. Nonetheless, despite increasing recognition of herb-drug interaction, a standard system for interaction prediction and evaluation is still nonexistent. This review article discusses the herb-drug interactions related hepatotoxicity and underlying mechanisms, including drug metabolizing enzymes and their regulation.

Euphausia pacifica as a source of 8(R)-hydroxy-eicosapentaenoic acid (8R-HEPE), 8(R)-hydroxy-eicosatetraenoic acid (8R-HETE) and 10(R)-hydroxy-docosahexaenoic acid (10R-HDHA)

Although not fully investigated, 8-HEPE, 8-HETE, and 10-HDHA have potentially beneficial effects for human health. Euphausia pacifica (North Pacific krill) is unique in containing several ppm level of 8R-HEPE, and sub-ppm levels of 8R-HETE and 10R-HDHA. Obtaining sufficient quantities of these compounds is a major bottleneck for conducting in vivo experiments to evaluate their biological activities. In this study, we examined an efficient way of obtaining 8R-HEPE, 8R-HETE, and 10R-HDHA by enzymatic production in E. pacifica. We devised a novel method to purify 199.4 mg of 8R-HEPE, 2.1 mg of 8R-HETE and 5.6 mg of 10R-HDHA from 1 kg of E. pacifica. We identified the stereochemistry of the hydroxy group at C-8 of HEPE and HETE and C-10 of HDHA as the R configuration by chiral column chromatography analysis using LC/QTOFMS.Abbreviations: 8-HEPE: 8-hydroxy-eicosapentaenoic acid; 8-HETE: 8-hydroxy-eicosatetraenoic acid; 10-HDHA: 10-hydroxy-docosahexaenoic acid; EPA: eicosapentaenoic acid; TLC-FID, thin layer chromatograph-Flame Ionization Detector; LC/QTOFMS: liquid chromatography/hybrid quadrupole time of flight mass spectrometry.

Effects of Docosahexaenoic Acid and Its Peroxidation Product on Amyloid-β Peptide-Stimulated Microglia

Growing evidence suggests that docosahexaenoic acid (DHA) exerts neuroprotective effects, although the mechanism(s) underlying these beneficial effects are not fully understood. Here we demonstrate that DHA, but not arachidonic acid (ARA), suppressed oligomeric amyloid-β peptide (oAβ)-induced reactive oxygen species (ROS) production in primary mouse microglia and immortalized mouse microglia (BV2). Similarly, DHA but not ARA suppressed oAβ-induced increases in phosphorylated cytosolic phospholipase A₂ (p-cPLA₂), inducible nitric oxide synthase (iNOS), and tumor necrosis factor-α (TNF-α) in BV2 cells. LC-MS/MS assay indicated the ability for DHA to cause an increase in 4-hydroxyhexenal (4-HHE) and suppress oAβ-induced increase in 4-hydroxynonenal (4-HNE). Although oAβ did not alter the nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, exogenous DHA, ARA as well as low concentrations of 4-HHE and 4-HNE upregulated this pathway and increased production of heme oxygenase-1 (HO-1) in microglial cells. These results suggest that DHA modulates ARA metabolism in oAβ-stimulated microglia through suppressing oxidative and inflammatory pathways and upregulating the antioxidative stress pathway involving Nrf2/HO-1. Understanding the mechanism(s) underlying the beneficial effects of DHA on microglia should shed light into nutraceutical therapy for the prevention and treatment of Alzheimer's disease (AD).

Genetically-encoded sensors to detect fatty acid production and trafficking

OBJECTIVE

Fatty acids are important for biological function; however, in excess, they can cause metabolic dysregulation. Methods to image and detect fatty acids in real time are lacking. Therefore, the current study examined the dynamics of fatty acid trafficking and signaling utilizing novel fluorescent and luminescent approaches.

METHODS

We generated fluorescent and luminescent-based genetically-encoded sensors based upon the ligand-dependent interaction between PPARα and SRC-1 to image and detect cellular dynamics of fatty acid trafficking.

RESULTS

The use of a fluorescent sensor demonstrates that fatty acids traffic rapidly from lipid droplets to the nucleus. Both major lipases ATGL and HSL contribute to fatty acid signaling from lipid droplet to nucleus, however, their dynamics differ. Furthermore, direct activation of lipolysis, independent of receptor-mediated signaling is sufficient to promote lipid droplet to nuclear trafficking of fatty acids. A luminescent-based sensor that reports intracellular fatty acid levels is amenable to high-throughput analysis.

CONCLUSIONS

Fatty acids traffic from lipid droplets to the nucleus within minutes of stimulated lipolysis. Genetically-encoded fluorescent and luminescent based sensors can be used to probe the dynamics of fatty acid trafficking and signaling.

Sepsis Immunometabolism: From Defining Sepsis to Understanding How Energy Production Affects Immune Response

OBJECTIVES

This review will examine current definitions and trends in sepsis management as well pathophysiologic mechanisms in animal and ex vivo studies that correlate decreased energy production with deranged inflammatory response during the septic process.

DATA SOURCES

The latest articles in the literature that focus on the role of immunometabolism and associated mechanisms in sepsis were selected.

STUDY SELECTION

The most relevant, original articles were included in the review.

DATA EXTRACTION

All pertinent data for sepsis definitions as well as changes in immunometabolic pathways during the septic process was reviewed and assessed for inclusion in this article.

DATA SYNTHESIS

Sepsis is a major cause of multiple organ dysfunction. It is the principal cause of death resulting from infection and one of the most expensive conditions treated in the United States. Despite current efforts to accurately define sepsis, novel treatments and highly trained providers, mortality rates for sepsis remain high, prompting a need for further investigation of underlying immunometabolic mechanisms to identify potential treatment targets. The definition of sepsis has shifted and changed in the past few decades due to poorly defined criteria, as well as unclear guidelines for providers with regards to management of severe sepsis and septic shock. The early identification of patients with a systemic inflammatory response that will progress to septic shock is critical since recent traditional therapeutic approaches, such as early goal-directed therapy, IV immunoglobulin, and anti-tumor necrosis factor-α antibodies have failed.

CONCLUSIONS

There are no effective anti-sepsis drug therapies due to complex inflammatory and metabolic interactions. Further studies regarding the interface between innate immunity and metabolism should be investigated to effectively address septic patient mortality rates.

N-3 fatty acids as preventive and therapeutic agents in attenuating PCOS complications

To our knowledge, in spite of several trials exploring the beneficial effect of n-3 polyunsaturated fatty acids (PUFA) on polycystic ovary syndrome (PCOS), no comprehensive evidence has investigated the effects of n-3 PUFA consumption on PCOS complications. Therefore, our aim was to conduct a review to investigate the possible effect and related mechanisms. A comprehensive systematic search was conducted in Embase, MEDLINE/PubMed, Google Scholar, and SCOPUS, to identify studies investigating n-3 fatty acids as a preventative or therapeutic agent for the attenuation of PCOS complications. Subsequently, the impact of omega-3 on PCOS, omega-3 and inflammation, omega-3 and insulin resistance, omega-3 and adipokines, omega-3 and lipid metabolism, omega-3 and endothelial function and omega-3 and hormonal factors were discussed. There are multiple mechanisms by which n-3 PUFAs may exert their beneficial effects on PCOS, including anti-obesity, glycemic and hormonal hemostasis, anti-inflammatory, regulation of adipokine production and enhancement of endothelial function.N-3 PUFAs are a promising agent in relieving complications associated with PCOS. Although most of the studies in patients with PCOS reported an improvement in most complications after administration of omega-3 supplements, there is a distinct dearth of studies investigating the dietary intake of these types of fatty acids. Moreover, favorable effects regarding the improvement of dyslipidemia, regulation of adipokines, regulation of hormonal factors and enhancement of endothelial function are limited. Therefore, more trials are warranted to investigate palatable mechanisms for clarifying the metabolic and hormonal effects of these agents in PCOS.

Comparative Evaluation of Gemcabene and Peroxisome Proliferator-Activated Receptor Ligands in Transcriptional Assays of Peroxisome Proliferator-Activated Receptors: Implication for the Treatment of Hyperlipidemia and Cardiovascular Disease

Gemcabene, a late-stage clinical candidate, has shown efficacy for LDL-C, non-HDL cholesterol, apoB, triglycerides, and hsCRP reduction, all risk factors for cardiovascular disease. In rodents, gemcabene showed changes in targets, including apoC-III, apoA-I, peroxisomal enzymes, considered regulated through peroxisome proliferator-activated receptor (PPAR) gene activation, suggesting a PPAR-mediated mechanism of action for the observed hypolipidemic effects observed in rodents and humans. In the current study, the gemcabene agonist activity against PPAR subtypes of human, rat, and mouse were compared with known lipid lowering PPAR activators. Surprisingly, gemcabene showed no or little PPAR-α transactivation compared with reference agonists, which showed concentration-dependent transactivation against human PPAR-α of 2.4- to 30-fold (fenofibric acid), 17-fold (GW590735), and 2.3- to 25-fold (WY-14643). These agents also showed robust transactivation of mouse and rat PPAR-α in a concentration-dependent manner. The known PPAR-δ agonists, GW1516, L165041, and GW0742, showed potent agonist activity against human, mouse, and rat receptors (ranging from 165- to 396-fold). By contrast, gemcabene at the highest concentration tested (300 μM) showed no response in mouse and rat and a marginal response against human PPAR-δ receptors (3.2-fold). For PPAR-γ, gemcabene showed no agonist activity against all 3 species at 100 μM and marginal activity (3.6- to 5-fold) at 300 μM. By contrast, the known agonists, rosiglitazone, indomethacin, and muraglitazar showed strong activation against the mouse, rat, and human PPAR-γ receptors. No clear antagonist activity was observed with gemcabene against any PPAR subtypes for all 3 species over a wide range of concentrations. In summary, the transactivation studies rule out gemcabene as a direct agonist or antagonist of PPAR-α, PPAR-γ, and PPAR-δ receptors of these 3 species. These data suggest that the peroxisomal effects observed in rodents and the lipid regulating effects observed in rodents and humans are not related to a direct activation of PPAR receptors by gemcabene.

Isolation of Sphingoid Bases from Starfish Asterias amurensis Glucosylceramides and Their Effects on Sphingolipid Production in Cultured Keratinocytes

Starfish Asterias amurensis produces sphingoid bases d18:3, 9-methyl-d18:3 (9Me-d18:3), and d22:2, which possess unique structural features. In this study, sphingoid bases prepared from A. amurensis glucosylceramides displayed unexpected elution behaviors from a general octadecyl silyl high-performance liquid chromatography (HPLC) column. For separation and isolation, sphingoid bases were fractionated by octadecyl silyl HPLC after N-acetylation, yielding d18:3, 9Me-d18:3, and two d22:2 isomers. To compare the biological activities of individual sphingoid bases, their effects on sphingolipid production in normal human keratinocytes were evaluated. Treatment with sphingoid bases increased the content of ceramides, glucosylceramides, and sphingomyelins in keratinocytes. Moreover, ceramides, which contain saturated ultra-long-chain fatty acids (C30-34), were significantly increased by treatment with d18:3, but not with other A. amurensis sphingoid bases. The mRNA level of the early differentiation marker keratin 10 was markedly decreased and sphingolipid synthesis-related genes were slightly increased in keratinocytes exposed to A. amurensis-derived d18:3, 9Me-d18:3, and d22:2 isomers. These results suggest that A. amurensis-derived sphingoid bases induce differentiation to varying degrees, sphingolipid production depends on their chemical structures, and d18:3 is the most promising functional sphingoid base.

MiR-15b can target insulin receptor to regulate hepatic insulin signaling in mice

Now diabetes is growing to be a health problems globally. However, its specific pathogenesis still needs further exploration. Here we showed that miR-15b was upregulated in the palmitate-induced HepG2 cells and livers of hyperglycemic mice. At the same time, we confirmed that the insulin receptor was a direct target of miR-15b. Then we found that the manipulation of miR-15b expression level could affect the insulin signaling pathway of HepG2 cells and the inhibition of miR-15b in liver of ob/ob mice can improve insulin sensitivity of mice. Furthermore, our study demonstrated that palmitate could upregulate the expression of miR-15b by activating PPARα. Our findings established PPARα-responsive miR-15b as a critical regulator of hepatic insulin signaling, thus serving as a new potential therapeutic target for diabetes.

The class 3 PI3K coordinates autophagy and mitochondrial lipid catabolism by controlling nuclear receptor PPARα

The class 3 phosphoinositide 3-kinase (PI3K) is required for lysosomal degradation by autophagy and vesicular trafficking, assuring nutrient availability. Mitochondrial lipid catabolism is another energy source. Autophagy and mitochondrial metabolism are transcriptionally controlled by nutrient sensing nuclear receptors. However, the class 3 PI3K contribution to this regulation is unknown. We show that liver-specific inactivation of Vps15, the essential regulatory subunit of the class 3 PI3K, elicits mitochondrial depletion and failure to oxidize fatty acids. Mechanistically, transcriptional activity of Peroxisome Proliferator Activated Receptor alpha (PPARα), a nuclear receptor orchestrating lipid catabolism, is blunted in Vps15-deficient livers. We find PPARα repressors Histone Deacetylase 3 (Hdac3) and Nuclear receptor co-repressor 1 (NCoR1) accumulated in Vps15-deficient livers due to defective autophagy. Activation of PPARα or inhibition of Hdac3 restored mitochondrial biogenesis and lipid oxidation in Vps15-deficient hepatocytes. These findings reveal roles for the class 3 PI3K and autophagy in transcriptional coordination of mitochondrial metabolism.

The influence of dietary fatty acids on liver fat content and metabolism

Non-alcoholic fatty liver disease encompasses a spectrum of conditions from hepatic steatosis through to cirrhosis; obesity is a known risk factor. The liver plays a major role in regulating fatty acid metabolism and perturbations in intrahepatic processes have potential to impact on metabolic health. It remains unclear why intra-hepatocellular fat starts to accumulate, but it likely involves an imbalance between fatty acid delivery to the liver, fatty acid synthesis and oxidation within the liver and TAG export from the liver. As man spends the majority of the day in a postprandial rather than postabsorptive state, dietary fatty acid intake should be taken into consideration when investigating why intra-hepatic fat starts to accumulate. This review will discuss the impact of the quantity and quality of dietary fatty acids on liver fat accumulation and metabolism, along with some of the potential mechanisms involved. Studies investigating the role of dietary fat in liver fat accumulation, although surprisingly limited, have clearly demonstrated that it is total energy intake, rather than fat intake per se, that is a key mediator of liver fat content; hyperenergetic diets increase liver fat whilst hypoenergetic diets decrease liver fat content irrespective of total fat content. Moreover, there is now, albeit limited evidence emerging to suggest the composition of dietary fat may also play a role in liver fat accumulation, with diets enriched in saturated fat appearing to increase liver fat content to a greater extent when compared with diets enriched in unsaturated fats.

Increase in muscle endurance in mice by dietary Yamabushitake mushroom (Hericium erinaceus) possibly via activation of PPARδ

Skeletal muscle fiber is largely classified into two types: type 1 (slow‐twitch) and type 2 (fast‐twitch) fibers. Meat quality and composition of fiber types are thought to be closely related. Previous research showed that overexpression of constitutively active peroxisome proliferator‐activated receptor (PPAR)δ, a nuclear receptor present in skeletal muscle, increased type 1 fibers in mice. In this study, we found that hexane extracts of Yamabushitake mushroom (Hericium erinaceus) showed PPARδ agonistic activity in vitro. Eight‐week‐old C57BL/6J mice were fed a diet supplemented with 5% (w/w) freeze‐dried Yamabushitake mushroom for 24 hr. After the treatment period, the extensor digitorum longus (EDL) muscles were excised. The Yamabushitake‐supplemented diet up‐regulated the PPARδ target genes Pdk4 and Ucp3 in mouse skeletal muscles in vivo. Furthermore, feeding the Yamabushitake‐supplemented diet to mice for 8 weeks resulted in a significant increase in muscle endurance. These results indicate that Yamabushitake mushroom contains PPARδ agonistic ligands and that dietary intake of Yamabushitake mushroom could activate PPARδ in skeletal muscle of mice. Unexpectedly, we observed no significant alterations in composition of muscle fiber types between the mice fed control and Yamabushitake‐supplemented diets.

Targeting lipid mediators in cancer biology

Bioactive lipids are essential components of human cells and tissues. As discussed in this review, the cancer lipidome is diverse and malleable, with the ability to promote or inhibit cancer pathogenesis. Targeting lipids within the tumor and surrounding microenvironment may be a novel therapeutic approach for treating cancer patients. Additionally, the emergence of a novel super-family of lipid mediators termed specialized pro-resolving mediators (SPMs) has revealed a new role for bioactive lipid mediators in the resolution of inflammation in cancer biology. The role of SPMs in cancer holds great promise in our understanding of cancer pathogenesis and can ultimately be used in future cancer diagnostics and therapy.

Self-regulation of the inflammatory response by peroxisome proliferator-activated receptors

The peroxisome proliferator-activated receptor (PPAR) family includes three transcription factors: PPARα, PPARβ/δ, and PPARγ. PPAR are nuclear receptors activated by oxidised and nitrated fatty acid derivatives as well as by cyclopentenone prostaglandins (PGA₂ and 15d-PGJ₂) during the inflammatory response. This results in the modulation of the pro-inflammatory response, preventing it from being excessively activated. Other activators of these receptors are nonsteroidal anti-inflammatory drug (NSAID) and fatty acids, especially polyunsaturated fatty acid (PUFA) (arachidonic acid, ALA, EPA, and DHA). The main function of PPAR during the inflammatory reaction is to promote the inactivation of NF-κB. Possible mechanisms of inactivation include direct binding and thus inactivation of p65 NF-κB or ubiquitination leading to proteolytic degradation of p65 NF-κB. PPAR also exert indirect effects on NF-κB. They promote the expression of antioxidant enzymes, such as catalase, superoxide dismutase, or heme oxygenase-1, resulting in a reduction in the concentration of reactive oxygen species (ROS), i.e., secondary transmitters in inflammatory reactions. PPAR also cause an increase in the expression of IκBα, SIRT1, and PTEN, which interferes with the activation and function of NF-κB in inflammatory reactions.

Impact of fatty acid binding protein 5-deficiency on COPD exacerbations and cigarette smoke-induced inflammatory response to bacterial infection

BACKGROUND

Although cigarette smoking (CS) is by far the most important risk factor of chronic obstructive pulmonary disease (COPD), repeated and sustained infections are clearly linked to disease pathogenesis and are responsible for acute inflammatory flares (i.e. COPD exacerbations). We have previously identified Fatty Acid Binding Protein 5 (FABP5) as an important anti-inflammatory protein in primary airway epithelial cells.

RESULTS

In this study we found decreased FABP5 mRNA and protein levels in peripheral blood mononuclear cells (PBMCs) of COPD patients, especially among those who reported episodes of COPD exacerbations. Using wildtype (WT) and FABP5-/- mice, we examined the effects of FABP5 on CS and infection-induced inflammatory responses. Similarly to what we saw in airway epithelial cells, infection increased FABP5 expression while CS decreased FABP5 expression in mouse lung tissues. CS-exposed and P. aeruginosa-infected FABP5-/- mice had significantly increased inflammation as shown by increased lung histopathological score, cell infiltration and inflammatory cytokine levels. Restoration of FABP5 in alveolar macrophages using a lentiviral approach attenuated the CS- and bacteria-induced pulmonary inflammation. And finally, while P. aeruginosa infection increased PPARγ activity, CS or FABP5 knockdown greatly reduced PPARγ activity.

CONCLUSIONS

These findings support a model in which CS-induced FABP5 inhibition contributes to increased inflammation in COPD exacerbations. It is interesting to speculate that the increased inflammation is a result of decreased PPARγ activity.

Sequence Variations in pxr (nr1i2) From Zebrafish (Danio rerio) Strains Affect Nuclear Receptor Function

Regulators of biotransformation are of particular interest in pharmacology and toxicology, determining in part the metabolism, disposition, and toxicity of chemicals. The nuclear receptor NR1I2 (pregnane X receptor, PXR) is a prominent xenosensor that regulates the expression of biotransformation enzymes governing elimination of many exogenous as well as endogenous compounds. Zebrafish (Danio rerio) has only one gene locus for pxr, but different genetic variants have been identified in zebrafish. However, the prevalence and significance of these variants are unknown. We hypothesize that sequence variation occurring in the Pxr gene of zebrafish may affect the action and fate of many chemicals in this species, a key model organism in various fields of research, including environmental toxicology. Here, we examine variation in Pxr sequences from four different strains of zebrafish and assess the responses of each Pxr to clotrimazole and butyl-4-aminobenzoate. The Pxr variants differed in both their ability to bind these structurally different ligands and to regulate reporter gene expression in vitro. We infer that the observed sequence variations in zebrafish Pxrs likely affect the response to putative Pxr agonists in vivo and potentially cause strain-specific biotransformation of xenobiotics in zebrafish. Thus, the choice of zebrafish strain could affect the outcome of downstream toxicological studies.

Is essential fatty acid interconversion an important source of PUFA in humans?

Humans can obtain pre-formed long-chain PUFA from the diet and are also able to convert essential fatty acids (EFA) to longer-chain PUFA. The metabolic pathway responsible for EFA interconversion involves alternating desaturation and carbon chain elongation reactions, and carbon chain shortening by peroxisomal β-oxidation. Studies using stable isotope tracers or diets supplemented with EFA show that capacity for PUFA synthesis is limited in humans, such that DHA (22 : 6n-3) synthesis in men is negligible. PUFA synthesis is higher in women of reproductive age compared with men. However, the magnitude of the contribution of hepatic PUFA synthesis to whole-body PUFA status remains unclear. A number of extra-hepatic tissues have been shown to synthesise PUFA or to express genes for enzymes involved in this pathway. The precise function of extra-hepatic PUFA synthesis is largely unknown, although in T lymphocytes PUFA synthesis is involved in the regulation of cell activation and proliferation. Local PUFA synthesis may also be important for spermatogenesis and fertility. One possible role of extra-hepatic PUFA synthesis is that it may provide PUFA in a timely manner to facilitate specific cell functions. If so, this may suggest novel insights into the effect of dietary PUFA and/or polymorphisms in genes involved in PUFA synthesis on health and tissue function.

The Antagonist Effect of Arachidonic Acid on GLUT4 Gene Expression by Nuclear Receptor Type II Regulation

OBJECTIVES

Obesity is a complex disease that has a strong association with diet and lifestyle. Dietary factors can influence the expression of key genes connected to insulin resistance, lipid metabolism, and adipose tissue composition. In this study, our objective was to determine gene expression and fatty acid (FA) profiles in visceral adipose tissue (VAT) from lean and morbidly obese individuals. We also aimed to study the agonist effect of dietary factors on glucose metabolism.

DESIGN AND METHODS

Lean and low and high insulin resistance morbidly obese subjects (LIR-MO and HIR-MO) were included in this study. The gene expression of liver X receptor type alpha (LXR-α) and glucose transporter type 4 (GLUT4) and the FA profiles in VAT were determined. Additionally, the in vivo and in vitro agonist effects of oleic acid (OA), linoleic acid (LA), and arachidonic acid (AA) by peroxisome proliferator-activated receptor type gamma 2 (PPAR-γ2) on the activity of GLUT4 were studied.

RESULTS

Our results showed a dysregulation of GLUT4 and LXR-α in VAT of morbidly obese subjects. In addition, a specific FA profile for morbidly obese individuals was found. Finally, AA was an PPAR-γ2 agonist that activates the expression of GLUT4.

CONCLUSIONS

Our study suggests a dysregulation of LXR-α and GLUT4 expression in VAT of morbidly obese individuals. FA profiles in VAT could elucidate their possible role in lipolysis and adipogenesis. Finally, AA binds to PPAR-γ2 to activate the expression of GLUT4 in the HepG2 cell line, showing an alternative insulin-independent activation of GLUT4.

Curcumin and/or omega-3 polyunsaturated fatty acids supplementation reduces insulin resistance and blood lipids in individuals with high risk of type 2 diabetes: a randomised controlled trial

Background

Lowering insulin resistance and dyslipidaemia may not only enhance glycaemic control but also preserve the β-cell function, reducing the overall risk of developing type 2 diabetes (T2D). The current study was aimed to evaluate the effects of curcumin and/or long-chain omega-3 polyunsaturated fatty acids (LCn-3PUFA) supplementation on glycaemic control and blood lipid levels in individuals at high risk of developing T2D.

Methods

This was a 2 × 2 factorial, randomised, double-blinded, placebo-controlled study. Participants were allocated to either double placebo (PL) or curcumin plus placebo matching for LCn-3PUFA (CC), or LCn-3PUFA plus placebo matching for curcumin (FO), or curcumin plus LCn-3PUFA (CC-FO) for twelve weeks. Primary outcome of the trial was glycaemic indices (HbA1C, fasting glucose and insulin). Insulin resistance and sensitivity is measured using homeostatic model assessment model.

Results

A total of sixty-four participants (PL, n = 16; CC, n = 15; FO, n = 17, CC-FO, n = 16) were included in the final analysis. Post-intervention, HbA1c and fasting glucose remained unchanged across all the groups. Insulin sensitivity was significantly improved in the CC supplemented group (32.7 ± 10.3%) compared to PL (P = 0.009). FO and CC-FO tended to improve insulin sensitivity by 14.6 ± 8.5% and 8.8 ± 7.7% respectively, but the difference did not reach significance. Triglyceride levels were further increased in the PL (26.9 ± 7.4%), however, CC and CC-FO supplementation reduced the triglycerides, FO resulted in the greatest reduction in triglycerides (− 16.4 ± 4.5%, P < 0.001).

Conclusion

Reduction in insulin resistance and triglycerides by curcumin and LCn-3PUFA appears to be attractive strategies for lowering the risk of developing T2D. However, this study failed to demonstrate complimentary benefits of curcumin and LCn-3PUFA on glycaemic control.

Trail registration

ACTRN12615000559516.

Electronic supplementary material

The online version of this article (10.1186/s12944-019-0967-x) contains supplementary material, which is available to authorized users.

N-3 polyunsaturated fatty acids: An innovative strategy against obesity and related metabolic disorders, intestinal alteration and gut microbiota dysbiosis

Obesity is now widely recognized to be associated with low-grade systemic inflammation. It has been shown that high-fat feeding modulates gut microbiota which strongly increased intestinal permeability leading to lipopolysaccharide absorption causing metabolic endotoxemia that triggers inflammation and metabolic disorders. N-3 polyunsaturated fatty acids (PUFAs) have been shown associated with anti-obesity properties, but results still remain heterogeneous and very few studies underlined the metabolic pathways involved. Thus, the use of Fat-1 transgenic mice allows to better understanding whether endogenous n-3 PUFAs enrichment contributes to obesity and associated metabolic disorders prevention. It specially evidence that such effects occur through modulations of gut microbiota and intestinal permeability. Then, by remodeling gut microbiota, endogenous n-3 PUFAs improve HF/HS-diet induced features of the metabolic syndrome which in turn affects host metabolism. Thus, increasing anti-obesogenic microbial species in the gut microbiota population (i.e Akkermansia) by appropriate n-3 PUFAs may represent a promising strategy to control or prevent metabolic diseases.

Identification and Molecular Characterization of Peroxisome Proliferator-Activated Receptor δ as a Novel Target for Covalent Modification by 15-Deoxy-Δ12,14-prostaglandin J2

PPARδ belongs to the peroxisome proliferator-activated receptor (PPAR) family of nuclear receptors. Upon activation by an agonist, PPARδ controls a variety of physiological processes via regulation of its target genes. 15-Deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) is a cyclopentenone prostaglandin that features an electrophilic, α,β-unsaturated ketone (an enone) in the cyclopentenone ring. Many of 15d-PGJ2's biological effects result from covalent interaction between C9 and the thiol group of a catalytic cysteine (Cys) in target proteins. In this study, we investigated whether 15d-PGJ2 activates PPARδ by forming a covalent adduct. Our data show that 15d-PGJ2 activates PPARδ's transcriptional activity through formation of a covalent adduct between its endocyclic enone at C9 and Cys249 in the receptor's ligand-binding domain. As expected, no adduct formation was seen following a Cys-to-Ser mutation at residue 249 (C249S) of PPARδ or with a PGD2/PGJ2 analogue that lacks the electrophilic C9. Furthermore, the PPARδ C249S mutation weakened induction of the receptor's DNA binding activity by 15d-PGJ2, which highlights the biological significance of our findings. Calculated chemical properties as well as data from molecular orbital calculations, reactive molecular dynamics simulations, and intrinsic reaction coordinate modeling also supported the selectivity of 15d-PGJ2's C9 toward PPARδ's Cys thiol. In summary, our results provide the molecular, chemical, and structural basis of 15d-PGJ2-mediated PPARδ activation, designating 15d-PGJ2 as the first covalent PPARδ ligand to be identified.

Cooperative cobinding of synthetic and natural ligands to the nuclear receptor PPARγ

Crystal structures of peroxisome proliferator-activated receptor gamma (PPARγ) have revealed overlapping binding modes for synthetic and natural/endogenous ligands, indicating competition for the orthosteric pocket. Here we show that cobinding of a synthetic ligand to the orthosteric pocket can push natural and endogenous PPARγ ligands (fatty acids) out of the orthosteric pocket towards an alternate ligand-binding site near the functionally important omega (Ω)-loop. X-ray crystallography, NMR spectroscopy, all-atom molecular dynamics simulations, and mutagenesis coupled to quantitative biochemical functional and cellular assays reveal that synthetic ligand and fatty acid cobinding can form a 'ligand link' to the Ω-loop and synergistically affect the structure and function of PPARγ. These findings contribute to a growing body of evidence indicating ligand binding to nuclear receptors can be more complex than the classical one-for-one orthosteric exchange of a natural or endogenous ligand with a synthetic ligand.

Obesity-related cellular stressors regulate gonadotropin releasing hormone gene expression via c-Fos/AP-1

Obesity is a risk factor for infertility, but mechanisms underlying this risk are unclear. Fertility is regulated by hypothalamic gonadotropin-releasing hormone, encoded by the Gnrh1 gene. Because obesity promotes endoplasmic reticulum (ER) stress, we sought to determine how tunicamycin-induced ER stress affected Gnrh1 gene expression in the mouse hypothalamic cell line GT1-7. Tunicamycin repressed expression of Gnrh1 in a PKC- and JNK-dependent manner, while upregulating expression of a known Gnrh1 repressor, Fos. Obesity is associated with increased circulating free fatty acids, and exposure to palmitate promoted ER stress and inflammation. Fos expression increased with palmitate dose, but Gnrh1 expression was upregulated with low-dose palmitate and repressed with high-dose palmitate. Using a small molecule inhibitor, we determined that AP-1 was required for Gnrh1 repression by high-dose palmitate or tunicamycin-induced ER stress. These findings suggest that hypogonadism driven by decreased hypothalamic GnRH may be a component of obesity-related infertility.

Improving Soluble Expression of Tyrosine Decarboxylase from Lactobacillus brevis for Tyramine Synthesis with High Total Turnover Number

The soluble expression of tyrosine decarboxylase (TDC) in heterologous host is often challenging. Here, acidic condition was found to be favorable for improving the soluble expression of TDC from Lactobacillus brevis in Escherichia coli, while addition of carbohydrates (such as glucose, arabinose, and fructose) was vital for decreasing the insoluble fraction. By simple pH control and addition of glucose, the specific activity of TDC in crude extract was enhanced to 46.3 U mg^-1, 3.67-fold of that produced from LB medium. Optimization of the reaction conditions revealed that Tween-80 was effective in improving the tyramine production catalyzed by TDC, especially at high tyrosine loadings. As much as 400 mM tyrosine could be completely converted into tyramine with a substrate to catalyst ratio of 29.0 g g^-1 and total turnover number of 23,300. This study provides efficient strategies for the highly soluble expression of TDC and biocatalytic production of tyramine.

Basic mechanisms of the regulation of L-carnitine status in monogastrics and efficacy of L-carnitine as a feed additive in pigs and poultry

A great number of studies have investigated the potential of L-carnitine as feed additive to improve performance of different monogastric and ruminant livestock species, with, however, discrepant outcomes. In order to understand the reasons for these discrepant outcomes, it is important to consider the determinants of L-carnitine status and how L-carnitine status is regulated in the animal's body. While it is a long-known fact that L-carnitine is endogenously biosynthesized in certain tissues, it was only recently recognized that critical determinants of L-carnitine status, such as intestinal L-carnitine absorption, tissue L-carnitine uptake, endogenous L-carnitine synthesis and renal L-carnitine reabsorption, are regulated by specific nutrient sensing nuclear receptors. This review aims to give a more in-depth understanding of the basic mechanisms of the regulation of L-carnitine status in monogastrics taking into account the most recent evidence on nutrient sensing nuclear receptors and evaluates the efficacy of L-carnitine as feed additive in monogastric livestock by providing an up-to-date overview about studies with L-carnitine supplementation in pigs and poultry.

C/VDdb: A multi-omics expression profiling database for a knowledge-driven approach in cardiovascular disease (CVD)

The cardiovascular disease (C/VD) database is an integrated and clustered information resource that covers multi-omic studies (microRNA, genomics, proteomics and metabolomics) of cardiovascular-related traits with special emphasis on coronary artery disease (CAD). This resource was built by mining existing literature and public databases and thereafter manual biocuration was performed. To enable integration of omic data from distinct platforms and species, a specific ontology was applied to tie together and harmonise multi-level omic studies based on gene and protein clusters (CluSO) and mapping of orthologous genes (OMAP) across species. CAD continues to be a leading cause of death in the population worldwide, and it is generally thought to be an age-related disease. However, CAD incidence rates are now known to be highly influenced by environmental factors and interactions, in addition to genetic determinants. With the complexity of CAD aetiology, there is a difficulty in research studies to elucidate general elements compared to other cardiovascular diseases. Data from 92 studies, covering 13945 molecular entries (4353 unique molecules) is described, including data descriptors for experimental setup, study design, discovery-validation sample size and associated fold-changes of the differentially expressed molecular features (p-value<0.05). A dedicated interactive web interface, equipped with a multi-parametric search engine, data export and indexing menus are provided for a user-accessible browsing experience. The main aim of this work was the development of a data repository linking clinical information and molecular differential expression in several CVD-related traits from multi-omics studies (genomics, transcriptomics, proteomics and metabolomics). As an example case of how to query and identify data sets within the database framework and concomitantly demonstrate the database utility, we queried CAD-associated studies and performed a systems-level integrative analysis. URL: www.padb.org/cvd

Elucidating the Beneficial Role of PPAR Agonists in Cardiac Diseases

Peroxisome proliferator-activated receptors (PPARs) are nuclear hormone receptors that bind to DNA and regulate transcription of genes involved in lipid and glucose metabolism. A growing number of studies provide strong evidence that PPARs are the promising pharmacological targets for therapeutic intervention in various diseases including cardiovascular disorders caused by compromised energy metabolism. PPAR agonists have been widely used for decades as lipid-lowering and anti-inflammatory drugs. Existing studies are mainly focused on the anti-atherosclerotic effects of PPAR agonists; however, their role in the maintenance of cellular bioenergetics remains unclear. Recent studies on animal models and patients suggest that PPAR agonists can normalize lipid metabolism by stimulating fatty acid oxidation. These studies indicate the importance of elucidation of PPAR agonists as potential pharmacological agents for protection of the heart from energy deprivation. Here, we summarize and provide a comprehensive analysis of previous studies on the role of PPARs in the heart under normal and pathological conditions. In addition, the review discusses the PPARs as a therapeutic target and the beneficial effects of PPAR agonists, particularly bezafibrate, to attenuate cardiomyopathy and heart failure in patients and animal models.

A prospective study of dietary polyunsaturated fatty acids intake and lung cancer risk

Animal studies have shown that polyunsaturated fatty acids (PUFAs) have antineoplastic and anti-inflammatory properties. Results from epidemiologic studies on specific types of PUFAs for lung cancer risk, however, are inconclusive. We prospectively evaluated the association of specific types of dietary PUFA intakes and lung cancer risk in two population-based cohort studies, the Shanghai Women's Health Study (SWHS) and Shanghai Men's Health Study (SMHS) with a total of 121,970 study participants (i.e., 65,076 women and 56,894 men). Dietary fatty acid intakes were derived from data collected at the baseline using validated food frequency questionnaires (FFQs). Cox proportional hazards model was performed to assess the association between PUFAs and lung cancer risk. Total, saturated and monounsaturated fatty acid intakes were not significantly associated with lung cancer risk. Total PUFAs intake was inversely associated with lung cancer risk [HRs and respective 95% CIs for quintiles 2-5 vs quintile 1: 0.84 (0.71-0.98), 0.97 (0.83-1.13), 0.86 (0.74-1.01) and 0.85 (0.73-1.00), ptrend  = 0.11]. However, DHA intake was positively associated with lung cancer risk [HRs and 95% CIs: 1.01 (0.86-1.19), 1.20 (1.03-1.41), 1.21 (1.03-1.42) and 1.24 (1.05-1.47), ptrend  = 0.001]. The ratio of n-6 PUFAs to n-3 PUFAs (i.e., 7:1) was inversely associated with lung cancer risk, particularly among never-smokers and adenocarcinoma patients. Total PUFAs and the ratio between n-6 PUFAs and n-3 PUFAs were inversely associated with lung cancer risk. This study highlights an important public health impact of PUFA intakes toward intervention/prevention programs of lung cancer.

δ-Tocotrienol, Isolated from Rice Bran, Exerts an Anti-Inflammatory Effect via MAPKs and PPARs Signaling Pathways in Lipopolysaccharide-Stimulated Macrophages

δ-Tocotrienol, an important component of vitamin E, has been reported to possess some physiological functions, such as anticancer and anti-inflammation, however their molecular mechanisms are not clear. In this study, δ-tocotrienol was isolated and purified from rice bran. The anti-inflammatory effect and mechanism of δ-tocotrienol against lipopolysaccharides (LPS) activated pro-inflammatory mediator expressions in RAW264.7 cells were investigated. Results showed that δ-tocotrienol significantly inhibited LPS-stimulated nitric oxide (NO) and proinflammatory cytokine (TNF-α, IFN-γ, IL-1β and IL-6) production and blocked the phosphorylation of c-Jun N-terminal kinase (JNK) and extracellular regulated protein kinases 1/2 (ERK1/2). δ-Tocotrienol repressed the transcriptional activations and translocations of nuclear factor-kappa B (NF-κB) and activator protein-1 (AP-1), which were closely related with downregulated cytokine expressions. Meanwhile, δ-tocotrienol also affected the PPAR signal pathway and exerted an anti-inflammatory effect. Taken together, our data showed that δ-tocotrienol inhibited inflammation via mitogen-activated protein kinase (MAPK) and peroxisome proliferator-activated receptor (PPAR) signalings in LPS-stimulated macrophages.

The Pioglitazone Trek via Human PPAR Gamma: From Discovery to a Medicine at the FDA and Beyond

For almost two decades, pioglitazone has been prescribed primarily to prevent and treat insulin resistance in some type 2 diabetic patients. In this review, we trace the path to discovery of pioglitazone as a thiazolidinedione compound, the glitazone tracks through the regulatory agencies, the trek to molecular agonism in the nucleus and the binding of pioglitazone to the nuclear receptor PPAR gamma. Given the rise in consumption of pioglitazone in T2D patients worldwide and the increased number of clinical trials currently testing alternate medical uses for this drug, there is also merit to some reflection on the reported adverse effects. Going forward, it is imperative to continue investigations into the mechanisms of actions of pioglitazone, the potential of glitazone drugs to contribute to unmet needs in complex diseases associated with the dynamics of adaptive homeostasis, and also the routes to minimizing adverse effects in every-day patients throughout the world.

Ex situ machine perfusion as a tool to recondition steatotic donor livers: Troublesome features of fatty livers and the role of defatting therapies. A systematic review

Long-standing research has shown that increased lipid content in donor livers is associated with inferior graft outcomes posttransplant. The global epidemic that is obesity has increased the prevalence of steatosis in organ donors, to the extent that it has become one of the main reasons for declining livers for transplantation. Consequently, it is one of the major culprits behind the discrepancy between the number of donor livers offered for transplantation and those that go on to be transplanted. Steatotic livers are characterized by poor microcirculation, depleted energy stores because of an impaired capacity for mitochondrial recovery, and a propensity for an exaggerated inflammatory response following reperfusion injury culminating in poorer graft function postoperatively. Ex situ machine perfusion, currently a novel method in graft preservation, is showing great promise in providing a tool for the recovery and reconditioning of marginal livers. Hence, reconditioning these steatotic livers using machine perfusion has the potential to increase the number of liver transplants performed. In this review, we consider the problematic issues associated with fatty livers in the realm of transplantation and discuss pharmacological and nonpharmacological options that are being developed to enhance recovery of these organs using machine perfusion and defatting strategies.

Molecular Actions of PPARα in Lipid Metabolism and Inflammation

Peroxisome proliferator-activated receptor α (PPARα) is a nuclear receptor of clinical interest as a drug target in various metabolic disorders. PPARα also exhibits marked anti-inflammatory capacities. The first-generation PPARα agonists, the fibrates, have however been hampered by drug-drug interaction issues, statin drop-in, and ill-designed cardiovascular intervention trials. Notwithstanding, understanding the molecular mechanisms by which PPARα works will enable control of its activities as a drug target for metabolic diseases with an underlying inflammatory component. Given its role in reshaping the immune system, the full potential of this nuclear receptor subtype as a versatile drug target with high plasticity becomes increasingly clear, and a novel generation of agonists may pave the way for novel fields of applications.

Peroxisome Proliferator-Activated Receptor-δ Supports the Metabolic Requirements of Cell Growth in TCRβ-Selected Thymocytes and Peripheral CD4+ T Cells

During T cell development, progenitor thymocytes undergo a large proliferative burst immediately following successful TCRβ rearrangement, and defects in genes that regulate this proliferation have a profound effect on thymus cellularity and output. Although the signaling pathways that initiate cell cycling and nutrient uptake after TCRβ selection are understood, less is known about the transcriptional programs that regulate the metabolic machinery to promote biomass accumulation during this process. In this article, we report that mice with whole body deficiency in the nuclear receptor peroxisome proliferator-activated receptor-δ (PPARδ^mut) exhibit a reduction in spleen and thymus cellularity, with a decrease in thymocyte cell number starting at the double-negative 4 stage of thymocyte development. Although in vivo DNA synthesis was normal in PPARδ^mut thymocytes, studies in the OP9-delta-like 4 in vitro system of differentiation revealed that PPARδ^mut double-negative 3 cells underwent fewer cell divisions. Naive CD4⁺ T cells from PPARδ^mut mice also exhibited reduced proliferation upon TCR and CD28 stimulation in vitro. Growth defects in PPAR-δ-deficient thymocytes and peripheral CD4⁺ T cells correlated with decreases in extracellular acidification rate, mitochondrial reserve, and expression of a host of genes involved in glycolysis, oxidative phosphorylation, and lipogenesis. By contrast, mice with T cell-restricted deficiency of Ppard starting at the double-positive stage of thymocyte development, although exhibiting defective CD4⁺ T cell growth, possessed a normal T cell compartment, pointing to developmental defects as a cause of peripheral T cell lymphopenia in PPARδ^mut mice. These findings implicate PPAR-δ as a regulator of the metabolic program during thymocyte and T cell growth.

Epigenetic-Transcriptional Regulation of Fatty Acid Metabolism and Its Alterations in Leukaemia

In recent years fatty acid metabolism has gained greater attention in haematologic cancers such as acute myeloid leukaemia. The oxidation of fatty acids provides fuel in the form of ATP and NADH, while fatty acid synthesis provides building blocks for cellular structures. Here, we will discuss how leukaemic cells differ from healthy cells in their increased reliance on fatty acid metabolism. In order to understand how these changes are achieved, we describe the main pathways regulating fatty acid metabolism at the transcriptional level and highlight the limited knowledge about related epigenetic mechanisms. We explore these mechanisms in the context of leukaemia and consider the relevance of the bone marrow microenvironment in disease management. Finally, we discuss efforts to interfere with fatty acid metabolism as a therapeutic strategy along with the use of metabolic parameters as biomarkers.

Etomoxir Inhibits Macrophage Polarization by Disrupting CoA Homeostasis

Long-chain fatty acid (LCFA) oxidation has been shown to play an important role in interleukin-4 (IL-4)-mediated macrophage polarization (M(IL-4)). However, many of these conclusions are based on the inhibition of carnitine palmitoyltransferase-1 with high concentrations of etomoxir that far exceed what is required to inhibit enzyme activity (EC₉₀ < 3 μM). We employ genetic and pharmacologic models to demonstrate that LCFA oxidation is largely dispensable for IL-4-driven polarization. Unexpectedly, high concentrations of etomoxir retained the ability to disrupt M(IL-4) polarization in the absence of Cpt1a or Cpt2 expression. Although excess etomoxir inhibits the adenine nucleotide translocase, oxidative phosphorylation is surprisingly dispensable for M(IL-4). Instead, the block in polarization was traced to depletion of intracellular free coenzyme A (CoA), likely resulting from conversion of the pro-drug etomoxir into active etomoxiryl CoA. These studies help explain the effect(s) of excess etomoxir on immune cells and reveal an unappreciated role for CoA metabolism in macrophage polarization.

Grifola frondosa (Maitake) extract activates PPARδ and improves glucose intolerance in high-fat diet-induced obese mice

Grifola frondosa is a mushroom that has anti-obesity effects, but the detailed mechanism is poorly understood. In this study, we found that lipid soluble extracts derived from G. frondosa (GFE) had peroxisome proliferator-activated receptor δ (PPARδ) agonist activity, inducing the expression of PPARδ-target genes in vitro. Furthermore, administration of GFE to high-fat diet-induced obese mice lowered the total blood cholesterol levels, upregulated the expression of PPARδ-target genes in skeletal muscles and improved glucose intolerance. Additionally, analyses of C2C12 myotubes revealed that GFE restored glucose uptake, which was inhibited by sodium palmitate, to normal levels. Unexpectedly, such acceleration was not abolished by a PPARδ antagonist. These results suggest that G. frondosa is a novel functional food that may prevent life-style related diseases like obesity and diabetes, and that these beneficial effects are likely to be mediated through the activation of PPARδ and a PPARδ-independent insulin signaling pathway.

Oleoylethanolamide treatment reduces neurobehavioral deficits and brain pathology in a mouse model of Gulf War Illness

There are nearly 250,000 Gulf War (GW) veterans who suffer from Gulf War Illness (GWI), a multi-symptom condition that remains untreatable. The main objective was to determine if targeting peroxisomal function could be of therapeutic value in GWI. We performed a pilot study that showed accumulation of very long chain fatty acids (VLCFA), which are metabolized in peroxisomes, in plasma from veterans with GWI. We then examined if targeting peroxisomal β-oxidation with oleoylethanolamide (OEA) restores these lipids to the normal levels and mitigates neuroinflammation and neurobehavioral deficits in a well-established mouse model of GWI. In GWI mice, treatment with OEA corresponded with cognitive benefits and reduced fatigue and disinhibition-like behavior in GWI mice. Biochemical and molecular analysis of the brain tissue showed reduced astroglia and microglia staining, decreased levels of chemokines and cytokines, and decreased NFκB phosphorylation. Treatment with OEA reduced accumulation of peroxisome specific VLCFA in the brains of GWI mice. These studies further support the translational value of targeting peroxisomes. We expect that OEA may be a potential therapy for treating neurobehavioral symptoms and the underlying lipid dysfunction and neuroinflammation associated with GWI. Oleoylethanolamide is available as a dietary supplement, making it appealing for human translational studies.

Skeletal muscle mitochondrial remodeling in exercise and diseases

Skeletal muscle fitness and plasticity is an important determinant of human health and disease. Mitochondria are essential for maintaining skeletal muscle energy homeostasis by adaptive re-programming to meet the demands imposed by a myriad of physiologic or pathophysiological stresses. Skeletal muscle mitochondrial dysfunction has been implicated in the pathogenesis of many diseases, including muscular dystrophy, atrophy, type 2 diabetes, and aging-related sarcopenia. Notably, exercise counteracts the effects of many chronic diseases on skeletal muscle mitochondrial function. Recent studies have revealed a finely tuned regulatory network that orchestrates skeletal muscle mitochondrial biogenesis and function in response to exercise and in disease states. In addition, increasing evidence suggests that mitochondria also serve to "communicate" with the nucleus and mediate adaptive genomic re-programming. Here we review the current state of knowledge relevant to the dynamic remodeling of skeletal muscle mitochondria in response to exercise and in disease states.

Role of peroxisome proliferator-activated receptors in non-alcoholic fatty liver disease inflammation

Overweight and obesity have been identified as the most important risk factors for many diseases, including cardiovascular disease, type 2 diabetes and lipid disorders, such as non-alcoholic fatty liver disease (NAFLD). The metabolic changes associated with obesity are grouped to define metabolic syndrome, which is one of the main causes of morbidity and mortality in industrialized countries. NAFLD is considered to be the hepatic manifestation of metabolic syndrome and is one of the most prevalent liver diseases worldwide. Inflammation plays an important role in the development of numerous liver diseases, contributing to the progression to more severe stages, such as non-alcoholic steatohepatitis and hepatocellular carcinoma. Peroxisome proliferator-activated receptors (PPARs) are binder-activated nuclear receptors that are involved in the transcriptional regulation of lipid metabolism, energy balance, inflammation and atherosclerosis. Three isotypes are known: PPAR-α, PPARδ/β and PPAR-γ. These isotypes play different roles in diverse tissues and cells, including the inflammatory process. In this review, we discuss current knowledge on the role PPARs in the hepatic inflammatory process involved in NAFLD as well as new pharmacological strategies that target PPARs.

An effective protocol for pharmacological defatting of primary human hepatocytes which is non-toxic to cholangiocytes or intrahepatic endothelial cells

Introduction

Pharmacological defatting of rat hepatocytes and hepatoma cell lines suggests that the same method could be used to ameliorate macrovesicular steatosis in moderate to severely fatty livers. However there is no data assessing the effects of those drugs on primary human liver cells. We aimed to determine the effectiveness of a pharmacological cocktail in reducing the in vitro lipid content of primary human hepatocytes (PHH). In addition we sought to determine the cytotoxicity of the cocktail towards non-parenchymal liver cells.

Methods

Steatosis was induced in PHH by supplementation with a combination of saturated and unsaturated free fatty acids. This was followed by addition of a defatting drug cocktail for up to 48 hours. The same experimental method was used with human intra-hepatic endothelial cells (HIEC) and human cholangiocytes. MTT assay was used to assess cell viability, triglyceride quantification and oil red O staining were used to determine intracellular lipids content whilst ketone bodies were measured in the supernatants following experimentation.

Results

Incubation of fat loaded PHH with the drugs over 48 hours reduced the intracellular lipid area by 54%, from 12.85% to 5.99% (p = 0.002) (percentage of total oil red O area), and intracellular triglyceride by 35%, from 28.24 to 18.30 nmol/million of cells (p<0.001). Total supernatant ketone bodies increased 1.4-fold over 48 hours in the defatted PHH compared with vehicle controls (p = 0.002). Moreover incubation with the drugs for 48 hours increased the viability of PHH by 11%, cholangiocytes by 25% whilst having no cytotoxic effects on HIEC.

Conclusion

These data demonstrate that pharmacological intervention can significantly decrease intracellular lipid content of PHH, increase fatty acids β-oxidation whilst being non-toxic to PHH, HIEC or cholangiocytes.

Linoleate-enriched diet increases both linoleic acid esterified to omega hydroxy very long chain fatty acids and free ceramides of canine stratum corneum without effect on protein-bound ceramides and skin barrier function

Few studies have investigated the influence of increased amounts of dietary linoleic acid on the epidermal lipid biochemistry and TEWL in healthy subject. The influence of dietary linoleic acid on canine stratum corneum (SC) lipids was studied by feeding two groups of five dogs differential amounts of linoleic acid (LA) for three months. SC was harvested by tape stripping and lipids were analyzed by thin-layer chromatography and mass spectrometry. The dogs that were fed the higher concentration of LA showed high increases in the contents of both linoleic acid and free ceramides in the SC, whereas the protein-bound ceramide content was unchanged. Acylacids that represent the esterified form of linoleic acid in omega hydroxy very long chain fatty acids (ω-OH VLCFA) accounted for most of the elevation of LA, whereas the concentration of the free form was not significantly changed. Corroborating the absence of change in the protein-bound ceramides content of healthy dogs SC, TEWL was nearly unaffected by the linoleic acid-enriched diet.