Role of nuclear receptors in the regulation of gene expression by dietary fatty acids (review)

Impact of dietary n-6/n-3 fatty acid ratio of atherosclerosis risk: A review

Atherosclerosis is a causative factor associated with cardiovascular disease (CVD). Over the past few decades, extensive research has been carried out on the relationship between the n-6/n-3 fatty acid ratio of ingested lipids and the progression of atherosclerosis. However, there are still many uncertainties regarding the precise nature of this relationship, which has led to challenges in providing sound dietary advice to the general public. There is therefore a pressing need to review our current understanding of the relationship between the dietary n-6/n-3 fatty acid ratio and atherosclerosis, and to summarize the underlying factors contributing to the current uncertainties. Initially, this article reviews the association between the n-6/n-3 fatty acid ratio and CVDs in different countries. A summary of the current understanding of the molecular mechanisms of n-6/n-3 fatty acid ratio on atherosclerosis is then given, including inflammatory responses, lipid metabolism, low-density lipoprotein cholesterol oxidation, and vascular function. Possible reasons behind the current controversies on the relationship between the n-6/n-3 fatty acid ratio and atherosclerosis are then provided, including the precise molecular structures of the fatty acids, diet-gene interactions, the role of fat-soluble phytochemicals, and the impact of other nutritional factors. An important objective of this article is to highlight areas where further research is needed to clarify the role of n-6/n-3 fatty acid ratio on atherosclerosis.

The HABD: Home of All Biological Databases Empowering Biological Research With Cutting-Edge Database Systems

The emergence of computer technologies and computing power has led to the development of several database systems that provide standardized access to vast quantities of data, making it possible to collect, search, index, evaluate, and extract useful knowledge across various fields. The Home of All Biological Databases (HABD) has been established as a continually expanding platform that aims to store, organize, and distribute biological data in a searchable manner, removing all dead and non-accessible data. The platform meticulously categorizes data into various categories, such as COVID-19 Pandemic Database (CO-19PDB), Database relevant to Human Research (DBHR), Cancer Research Database (CRDB), Latest Database of Protein Research (LDBPR), Fungi Databases Collection (FDBC), and many other databases that are categorized based on biological phenomena. It currently provides a total of 22 databases, including 6 published, 5 submitted, and the remaining in various stages of development. These databases encompass a range of areas, including phytochemical-specific and plastic biodegradation databases. HABD is equipped with search engine optimization (SEO) analyzer and Neil Patel tools, which ensure excellent SEO and high-speed value. With timely updates, HABD aims to facilitate the processing and visualization of data for scientists, providing a one-stop-shop for all biological databases. Computer platforms, such as PhP, html, CSS, Java script and Biopython, are used to build all the databases. © 2024 Wiley Periodicals LLC.

The effect of conjugated linoleic acids on inflammation, oxidative stress, body composition and physical performance: a comprehensive review of putative molecular mechanisms

Conjugated linoleic acids (CLAs) are polyunsaturated fatty acids primarily found in dairy products and ruminant animal products such as beef, lamb, and butter. Supplementation of CLAs has recently become popular among athletes due to the variety of health-promoting effects, including improvements in physical performance. Preclinical and some clinical studies have shown that CLAs can reduce inflammation and oxidative stress and favorably modulate body composition and physical performance; however, the results of previously published clinical trials are mixed. Here, we performed a comprehensive review of previously published clinical trials that assessed the role of CLAs in modulating inflammation, oxidative stress, body composition, and select indices of physical performance, emphasizing the molecular mechanisms governing these changes. The findings of our review demonstrate that the effect of supplementation with CLAs on inflammation and oxidative stress is controversial, but this supplement can decrease body fat mass and increase physical performance. Future well-designed randomized clinical trials are warranted to determine the effectiveness of (1) specific doses of CLAs; (2) different dosing durations of CLAs; (3) various CLA isomers, and the exact molecular mechanisms by which CLAs positively influence oxidative stress, inflammation, body composition, and physical performance.

Fatty acid-binding protein genes in gilthead seabream: molecular cloning and nutritional regulation under low water temperatures

The molecular characteristics and tissue disruption of 10 fatty acid-binding protein (fabp) genes in gilthead seabream (Sparus aurata) were investigated, and their expression levels were found in the fish fed diets with different vegetable oil (VO) sources, which may explore the potential function of fabp genes in S. aurata. For this purpose, the open reading frames of fabp genes involved in the transport and ß-oxidation of fatty acids (FA) were molecularly cloned and characterized. S. aurata was then exposed to a two-staged feeding trial (the grow-out period following a wash-out period) at low water temperatures. In the grow-out period, the fish were fed diets containing 50% and 100% ratios of various VOs for 60 days, and in the wash-out period, the fish were fed a diet containing 100% fish oil (FO) for 30 days. It has been determined that (a) S. aurata and vertebrate fabp/FABP genes are orthologues; (b) spatio-temporal differences in tissue-specific patterns of fabp genes differ importantly; for instance, the difference between the highest and lowest values reaches 13 × 10⁵ -fold in the fabp10a; and (c) VO-based diets upregulated fabp transcript levels in the liver and muscle with some exceptions, such as liver fabp11a and muscle fabp7a. Gene expressions of only the hepatic fabp7b and fabp10a genes were diminished at the end of the wash-out period. In this study, the authors provide further evidence that dietary FAs affect fabp mRNA expressions in S. aurata. This might be useful in the nutritional control of fabp genes to maintain lipid homeostasis in marine fish fed VO-based diets at low water temperatures.

Immunomodulation for unexplained recurrent implantation failure: where are we now?

In brief

Immune dysfunction may contribute to or cause recurrent implantation failure. This article summarizes normal and pathologic immune responses at implantation and critically appraises currently used immunomodulatory therapies.

Abstract

Recurrent implantation failure (RIF) may be defined as the absence of pregnancy despite the transfer of ≥3 good-quality blastocysts and is unexplained in up to 50% of cases. There are currently no effective treatments for patients with unexplained RIF. Since the maternal immune system is intricately involved in mediating endometrial receptivity and embryo implantation, both insufficient and excessive endometrial inflammatory responses during the window of implantation are proposed to lead to implantation failure. Recent strategies to improve conception rates in RIF patients have focused on modulating maternal immune responses at implantation, through either promoting or suppressing inflammation. Unfortunately, there are no validated, readily available diagnostic tests to confirm immune-mediated RIF. As such, immune therapies are often started empirically without robust evidence as to their efficacy. Like other chronic diseases, patient selection for immunomodulatory therapy is crucial, and personalized medicine for RIF patients is emerging. As the literature on the subject is heterogenous and rapidly evolving, we aim to summarize the potential efficacy, mechanisms of actions and side effects of select therapies for the practicing clinician.

Role of Peroxisome Proliferator-Activated Receptors (PPARs) in Energy Homeostasis of Dairy Animals: Exploiting Their Modulation through Nutrigenomic Interventions

Peroxisome proliferator-activated receptors (PPARs) are the nuclear receptors that could mediate the nutrient-dependent transcriptional activation and regulate metabolic networks through energy homeostasis. However, these receptors cannot work properly under metabolic stress. PPARs and their subtypes can be modulated by nutrigenomic interventions, particularly under stress conditions to restore cellular homeostasis. Many nutrients such as polyunsaturated fatty acids, vitamins, dietary amino acids and phytochemicals have shown their ability for potential activation or inhibition of PPARs. Thus, through different mechanisms, all these nutrients can modulate PPARs and are ultimately helpful to prevent various metabolic disorders, particularly in transition dairy cows. This review aims to provide insights into the crucial role of PPARs in energy metabolism and their potential modulation through nutrigenomic interventions to improve energy homeostasis in dairy animals.

Peroxisomal footprint in the pathogenesis of nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is a form of fatty liver disease where benign hepatic steatosis leads to chronic inflammation in the steatotic liver of a patient without any history of alcohol abuse. Mechanisms underlying the progression of hepatic steatosis to NASH have long been investigated. This review outlines the potential role of peroxisomal dysfunctions in exacerbating the disease in NASH. Loss of peroxisomes as well as impaired peroxisomal functions have been demonstrated to occur in inflammatory conditions including NASH. Because peroxisomes and mitochondria co-operatively perform many metabolic functions including O₂ and lipid metabolisms, a compromised peroxisomal biogenesis and function can potentially contribute to defective lipid and reactive oxygen species metabolism which in turn can lead the progression of disease in NASH. Impaired peroxisomal biogenesis and function may be due to the decreased expression of peroxisomal proliferator-activated receptor-α (PPAR-α), the major transcription factor of peroxisomal biogenesis. Recent studies indicate that the reduced expression of PPAR-α in NASH is correlated with the activation of the toll-like receptor-4 pathway (TLR-4). Further investigations are required to establish the mechanistic connection between the TLR-4 pathway and PPAR-α-dependent impaired biogenesis/function of peroxisomes in NASH.

Discovery of new chalone adamantyl arotinoids having RXRα-modulating and anticancer activities

In the present study, a new series of chalcone adamantly arotinoids (chalcone AdArs) derived from RAR antagonist MX781, are synthesized, characterized, and evaluated for the biological activities in vitro. The studies of antiproliferative activity and RXRα-binding affinity of target compounds result in the discovery of a lead candidate (WA15), which is a good RXRα binder (K_d = 2.89 × 10^-6 M) with potent antiproliferative activity against human cancer cell lines (IC₅₀ ≈ 10 μM) and low toxic to normal LO2 and MRC-5 cells (IC₅₀ > 50 μM). Different from MX781, WA15 eliminates RARα antagonist activity but inhibits 9-cis-RA-induced RXRα transactivation activity in a dose-dependent manner. Compound WA15 is found to be a good apoptosis inducer in various cancer cells and promotes cell apoptosis in an RXRα-independent manner. Besides, WA15 shows the induction of proteasome-dependent RXRα degradation which might enhance the WA15-induced apoptosis. Finally, the immunoblotting indicates that WA15 can inhibit the TNFα-induced IKK activation and IκBα degradation, suggesting that the anticancer activity of WA15 might be related to the inhibition of IKK/NF-κB signal pathway.

Cytochrome P450 Metabolism of Polyunsaturated Fatty Acids and Neurodegeneration

Due to the aging population in the world, neurodegenerative diseases have become a serious public health issue that greatly impacts patients' quality of life and adds a huge economic burden. Even after decades of research, there is no effective curative treatment for neurodegenerative diseases. Polyunsaturated fatty acids (PUFAs) have become an emerging dietary medical intervention for health maintenance and treatment of diseases, including neurodegenerative diseases. Recent research demonstrated that the oxidized metabolites, particularly the cytochrome P450 (CYP) metabolites, of PUFAs are beneficial to several neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease; however, their mechanism(s) remains unclear. The endogenous levels of CYP metabolites are greatly affected by our diet, endogenous synthesis, and the downstream metabolism. While the activity of omega-3 (ω-3) CYP PUFA metabolites and omega-6 (ω-6) CYP PUFA metabolites largely overlap, the ω-3 CYP PUFA metabolites are more active in general. In this review, we will briefly summarize recent findings regarding the biosynthesis and metabolism of CYP PUFA metabolites. We will also discuss the potential mechanism(s) of CYP PUFA metabolites in neurodegeneration, which will ultimately improve our understanding of how PUFAs affect neurodegeneration and may identify potential drug targets for neurodegenerative diseases.

Relationship between the effect of polyunsaturated fatty acids (PUFAs) on brain plasticity and the improvement on cognition and behavior in individuals with autism spectrum disorder

Objective: This work aimed to compile information about the neuronal processes in which polyunsaturated fatty acids (PUFAs) could modulate brain plasticity, in order to analyze the role of nutritional intervention with the ω-3 and ω-6 fatty acids as a therapeutic strategy for the Autism Spectrum Disorder (ASD)-related signs and symptoms.Methods: We reviewed different articles reporting the effect of PUFAS on neurite elongation, membrane expansion, cytoskeleton rearrangement and neurotransmission, considering the ASD-related abnormalities in these processes.Results: In accordance to the reviewed studies, it is clear that ASD is one of the neurological conditions associated with an impairment in neuronal plasticity; therefore, PUFAs-rich diet improvements on cognition and behavioral deficits in individuals with autism, could be involved with the regulation of neuronal processes implicated in the atypical brain plasticity related with this neurodevelopmental disorder.Discussion: The behavioral and cognitive improvement observed in individuals with ASD after PUFAs treatment might underlie, at least in part, in the ability of ω-3 and ω-6 fatty acids to induce neurite outgrowth, probably, through the dynamic regulation of the neuronal cytoskeleton along with the expansion of neuronal membranes. Furthermore, it might also be associated with an enhancement of the efficacy of synaptic transmission and the modulation of neurotransmitters release.

Decreased Metabolic Flexibility in Skeletal Muscle of Rat Fed with a High-Fat Diet Is Recovered by Individual CLA Isomer Supplementation via Converging Protective Mechanisms

Energy balance, mitochondrial dysfunction, obesity, and insulin resistance are disrupted by metabolic inflexibility while therapeutic interventions are associated with improved glucose/lipid metabolism in skeletal muscle. Conjugated linoleic acid mixture (CLA) exhibited anti-obesity and anti-diabetic effects; however, the modulatory ability of its isomers (cis9, trans11, C9; trans10, cis12, C10) on the metabolic flexibility in skeletal muscle remains to be demonstrated. Metabolic inflexibility was induced in rat by four weeks of feeding with a high-fat diet (HFD). At the end of this period, the beneficial effects of C9 or C10 on body lipid content, energy expenditure, pro-inflammatory cytokines, glucose metabolism, and mitochondrial efficiency were examined. Moreover, oxidative stress markers, fatty acids, palmitoyletanolamide (PEA), and oleyletanolamide (OEA) contents along with peroxisome proliferator-activated receptors-alpha (PPARα), AKT, and adenosine monophosphate-activated protein kinase (AMPK) expression were evaluated in skeletal muscle to investigate the underlying biochemical mechanisms. The presented results indicate that C9 intake reduced mitochondrial efficiency and oxidative stress and increased PEA and OEA levels more efficiently than C10 while the anti-inflammatory activity of C10, and its regulatory efficacy on glucose homeostasis are associated with modulation of the PPARα/AMPK/pAKT signaling pathway. Our results support the idea that the dissimilar efficacy of C9 and C10 against the HFD-induced metabolic inflexibility may be consequential to their ability to activate different molecular pathways.

Nutrigenomic Effect of Saturated and Unsaturated Long Chain Fatty Acids on Lipid-Related Genes in Goat Mammary Epithelial Cells: What Is the Role of PPARγ?

A prior study in bovine mammary (MACT) cells indicated that long-chain fatty acids (LCFA) C16:0 and C18:0, but not unsaturated LCFA, control transcription of milk fat-related genes partly via the activation of peroxisome proliferator-activated receptor gamma (PPARγ). However, in that study, the activation of PPARγ by LCFA was not demonstrated but only inferred. Prior data support a lower response of PPARγ to agonists in goat mammary cells compared to bovine mammary cells. The present study aimed to examine the hypothesis that LCFA alter the mRNA abundance of lipogenic genes in goat mammary epithelial cells (GMEC) at least in part via PPARγ. Triplicate cultures of GMEC were treated with a PPARγ agonist (rosiglitazone), a PPARγ inhibitor (GW9662), several LCFA (C16:0, C18:0, t10,c12-CLA, DHA, and EPA), or a combination of GW9662 with each LCFA. Transcription of 28 genes involved in milk fat synthesis was measured using RT-qPCR. The data indicated that a few measured genes were targets of PPARγ in GMEC (SCD1, FASN, and NR1H3) while more genes required a basal activation of PPARγ to be transcribed (e.g., LPIN1, FABP3, LPL, and PPARG). Among the tested LCFA, C16:0 had the strongest effect on upregulating transcription of measured genes followed by C18:0; however, for the latter most of the effect was via the activation of PPARγ. Unsaturated LCFA downregulated transcription of measured genes, with a lesser effect by t10,c12-CLA and a stronger effect by DHA and EPA; however, a basal activation of PPARγ was essential for the effect of t10,c12-CLA while the activation of PPARγ blocked the effect of DHA. The transcriptomic effect of EPA was independent from the activation of PPARγ. Data from the present study suggest that saturated LCFA, especially C18:0, can modulate milk fat synthesis partly via PPARγ in goats. The nutrigenomic effect of C16:0 is not via PPARγ but likely via unknown transcription factor(s) while PPARγ plays an indirect role on the nutrigenomic effect of polyunsaturated LCFA (PUFA) on milk fat related genes, particularly for CLA (permitting effect) and DHA (blocking effect).

Cytotoxic Necrotizing Factor 1 Downregulates CD36 Transcription in Macrophages to Induce Inflammation During Acute Urinary Tract Infections

Urinary tract infections (UTIs) caused by uropathogenic Escherichia coli (UPEC) induce cystitis, pyelonephritis, and can cause kidney scarring and failure if inflammation is not under control. The detailed effects of cytotoxic necrotizing factor 1 (CNF1), the key UPEC toxin, on the pathogenicity of UPEC remain unclear. CD36 is an important scavenger receptor, responsible for pathogen and apoptotic cell clearance, and plays an essential role in host immune defense and homeostasis. Regulation of CD36 by bacterial toxins has not been reported. In this study, using a pyelonephritis mouse model, CNF1 was observed to contribute to increasing neutrophils and bacterial titers in infected bladder and kidney tissues, resulting in severe inflammation and tissue damage. CD36 expression in macrophages was found to be decreased by CNF1 in vitro and in vivo. We demonstrated that CNF1 attenuated CD36 transcription by decreasing expressions of its upstream transcription factors LXRβ and C/EBPα and their recruitment to the CD36 promotor. In addition, Cdc42 was found to be involved in CNF1-mediated downregulation of LXRβ. Our study investigated the pathogenesis of cnf1-carrying UPEC, which affected host innate immune defenses and homeostasis through regulation of CD36 in macrophages during acute UTIs.

The effects of trans-fatty acids on TAG regulation in mice depend on dietary unsaturated fatty acids

The aim of this study was to investigate the effects of trans-fatty acids (TFA) on liver and serum TAG regulation in mice fed diets containing different proportions of n-3, n-6 and n-9 unsaturated fatty acids (UFA) from olive (O), maize (C) or rapeseed (R) oils partially substituted or not with TFA (Ot, Ct and Rt, respectively). Male CF1 mice were fed (30 d) one of these diets. The effects of the partial substitution (1 %, w/w) of different UFA with TFA on the activity and expression of hepatic enzymes involved in lipogenesis and fatty acids oxidation were evaluated, as well as their transcription factor expressions. Some of the mechanisms involved in the serum TAG regulation, hepatic VLDL rich in TAG (VLDL-TAG) secretion rate and lipoprotein lipase (LPL) activity were assessed. In liver, TFA induced an increase in TAG content in the Ot and Rt groups, and this effect was associated with an imbalance between lipogenesis and β-oxidation. In the Ot group, exacerbated lipogenesis may be one of the mechanisms responsible for the liver steatosis induced by TFA, whereas in Rt it has been related to a decreased β-oxidation, compared with their respective controls. The enhanced hepatic VLDL-TAG secretion in the Ot and Rt groups was compensated with a differential removal of TAG by LPL enzyme in extrahepatic tissues, leading to unchanged serum TAG levels. In brief, the effects of low levels of TFA on liver and serum TAG regulation in mice depend on the dietary proportions of n-3, n-6 and n-9 UFA.

Peroxisome proliferator-activated receptor α ligands and modulators from dietary compounds: Types, screening methods and functions

Peroxisome proliferator-activated receptor α (PPARα) plays a key role in lipid metabolism and glucose homeostasis and a crucial role in the prevention and treatment of metabolic diseases. Natural dietary compounds, including nutrients and phytochemicals, are PPARα ligands or modulators. High-throughput screening assays have been developed to screen for PPARα ligands and modulators in our diet. In the present review, we discuss recent advances in our knowledge of PPARα, including its structure, function, and ligand and modulator screening assays, and summarize the different types of dietary PPARα ligands and modulators.

Polyunsaturated fatty acids and suicide risk in mood disorders: A systematic review

Deficiency of omega-3 polyunsaturated fatty acids (PUFAs) and an alteration between the ratio of omega-3 and omega-6 PUFAs may contribute to the pathogenesis of bipolar disorder and unipolar depression. Recent epidemiological studies have also demonstrated an association between the depletion of PUFAs and suicide. Our aim was to investigate the relationship between PUFAs and suicide; assess whether the depletion of PUFAs may be considered a risk factor for suicidal behavior; in addition to detailing the potential use of PUFAs in clinical practice. We performed a systematic review on PUFAs and suicide in mood disorders, searching MedLine, Excerpta Medica, PsycLit, PsycInfo, and Index Medicus for relevant epidemiological, post-mortem, and clinical studies from January 1997 to September 2016. A total of 20 articles from peer-reviewed journals were identified and selected for this review. The reviewed studies suggest that subjects with psychiatric conditions have a depletion of omega-3 PUFAs compared to control groups. This fatty acid depletion has also been found to contribute to suicidal thoughts and behavior in some cases. However, large epidemiological studies have generally not supported this finding, as the depletion of omega-3 PUFAs was not statistically different between controls and patients diagnosed with a mental illness and/or who engaged in suicidal behavior. Increasing PUFA intake may be relevant in the treatment of depression, however in respect to the prevention of suicide, the data is currently not supportive of this approach. Changes in levels of PUFAs may however be a risk factor to evaluate when assessing for suicide risk. Clinical studies should be conducted to prospectively assess whether prescriptive long-term use of PUFAs in PUFA-deficient people with depression, may have a preventative role in attenuating suicide.

Nutrigenomic Functions of PPARs in Obesogenic Environments

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors that mediate the effects of several nutrients or drugs through transcriptional regulation of their target genes in obesogenic environments. This review consists of three parts. First, we summarize current knowledge regarding the role of PPARs in governing the development of white and brown/beige adipocytes from uncommitted progenitor cells. Next, we discuss the interactions of dietary bioactive molecules, such as fatty acids and phytochemicals, with PPARs for the modulation of PPAR-dependent transcriptional activities and metabolic consequences. Lastly, the effects of PPAR polymorphism on obesity and metabolic outcomes are discussed. In this review, we aim to highlight the critical role of PPARs in the modulation of adiposity and subsequent metabolic adaptation in response to dietary challenges and genetic modifications. Understanding the changes in obesogenic environments as a consequence of PPARs/nutrient interactions may help expand the field of individualized nutrition to prevent obesity and obesity-associated metabolic comorbidities.

Relationship of serum polyunsaturated fatty acids with cytokines in colorectal cancer

AIM: To investigate the relationship of serum levels of polyunsaturated fatty acid (PUFA) with kinds of cytokines in colorectal cancer (CRC).

METHODS: Serum samples of 100 CRC patients were collected. The concentration of total n-3 PUFA which included C18:3 n-3, C20:5 n-3, C22:5 n-3, C22:6 n-3 and the total n-6 PUFA included C18:2 n-6, C18:3 n-6, C20:3 n-6, C20:4 n-6, and C22:5 n-6 were detected on GC-2010 Plus Gas Chromatograph with a OmegawaxTM 250 column. Cytokines were detected by MagPlexTM-C microspheres. P values for the trend were estimated by creating a continuous variable using the median value within quartiles.

RESULTS: Interleukin-6 (IL-6) showed significantly positive association with the C20:4 n-6 (P for trend = 0.004). Interferon gamma (IFN-γ) showed significant positive association with the C22:5 n-3 (P for trend = 0.035). IL-8 and matrix metalloproteinase-9 (MMP-9) showed significant inverse association with the C22:6 n-3 (P for trend = 0.049, and 0.021). MMP-2 showed significant inverse association with the C20:5 n-3 (P for trend = 0.008). MMP-7 showed significantly positive association with the ratio of n-6 PUFA and n-3 PUFA (P for trend = 0.008). MMP-7 also showed significantly inverse association with the ratio of C20:4 n-6 and (n-6 PUFA + n-3 PUFA) (P for trend = 0.024). IL-10 (P for trend = 0.023) and IL-6 (P for trend = 0.036) showed significantly positive association with the ratio of C20:4 n-6 and C20:5 n-3.

CONCLUSION: Our data suggested that serum levels of PUFA is related to the inflammation of CRC, and also play different role in regulation of immune response.

Role of 4-hydroxynonenal-protein adducts in human diseases

SIGNIFICANCE

Oxidative stress provokes the peroxidation of polyunsaturated fatty acids in cellular membranes, leading to the formation of aldheydes that, due to their high chemical reactivity, are considered to act as second messengers of oxidative stress. Among the aldehydes formed during lipid peroxidation (LPO), 4-hydroxy-2-nonenal (HNE) is produced at a high level and easily reacts with both low-molecular-weight compounds and macromolecules, such as proteins and DNA. In particular, HNE-protein adducts have been extensively investigated in diseases characterized by the pathogenic contribution of oxidative stress, such as cancer, neurodegenerative, chronic inflammatory, and autoimmune diseases.

RECENT ADVANCES

In this review, we describe and discuss recent insights regarding the role played by covalent adducts of HNE with proteins in the development and evolution of those among the earlier mentioned disease conditions in which the functional consequences of their formation have been characterized.

CRITICAL ISSUES

Results obtained in recent years have shown that the generation of HNE-protein adducts can play important pathogenic roles in several diseases. However, in some cases, the generation of HNE-protein adducts can represent a contrast to the progression of disease or can promote adaptive cell responses, demonstrating that HNE is not only a toxic product of LPO but also a regulatory molecule that is involved in several biochemical pathways.

FUTURE DIRECTIONS

In the next few years, the refinement of proteomical techniques, allowing the individuation of novel cellular targets of HNE, will lead to a better understanding the role of HNE in human diseases.

Oleic acid increases intestinal absorption of the BCRP/ABCG2 substrate, mitoxantrone, in mice

The efflux transporter breast cancer resistance protein (BCRP/ABCG2) decrease intestinal absorption of many food toxicants. Oleic acid increases absorption of the specific BCRP substrate mitoxantrone (MXR), and also BCRP gene expression in human intestinal Caco-2 cells, suggesting that oleic acid affect the BCRP function. Here, we investigated the effect of oleic acid on intestinal absorption of MXR in mice. Mice were orally dosed with 2.4g oleic acid/kg b.w. and 1mg MXR/kg b.w., and sacrificed 30, 60, 90 or 120min after exposure, or were exposed to 0.6, 2.4 or 4.8g oleic acid/kg b.w. and 1mg MXR/kg b.w., and sacrificed 90min after exposure. Mice were also treated with Ko143 together with MXR and sacrificed after 60min, as a positive control of BCRP-mediated effects on MXR absorption. Absorption of MXR increased after exposure to oleic acid at all doses, and also after exposure to Ko143. Intestinal BCRP gene expression tended to increase 120min after oleic acid exposure. Our results in mice demonstrate that oleic acid decreases BCRP-mediated efflux, causing increased intestinal MXR absorption in mice. These findings may have implications in humans, concomitantly exposed to oleic acid and food contaminants that, similarly as MXR, are substrates of BCRP.

Modulation of inflammation and immunity by dietary conjugated linoleic acid

Conjugated linoleic acid (CLA) is a mixture of positional and geometric isomers of linoleic acid. This family of polyunsaturated fatty acids has drawn significant attention in the last three decades for its variety of biologically beneficial properties and health effects. CLA has been shown to exert various potent protective functions such as anti-inflammatory, anticarcinogenic, antiadipogenic, antidiabetic and antihypertensive properties in animal models of disease. Therefore, CLA represents a nutritional avenue to prevent lifestyle diseases or metabolic syndrome. Initially, the overall effects of CLA were thought to be the result of interactions between its two major isomers: cis-9, trans-11 and trans-10, cis-12. However, later evidence suggests that such physiological effects of CLA might be different between the isomers: t-10, c-12-CLA is thought to be anticarcinogenic, antiobesity and antidiabetic, whereas c-9, t-11-CLA is mainly anti-inflammatory. Although preclinical data support a benefit of CLA supplementation, human clinical findings have yet to show definitive evidence of a positive effect. The purpose of this review is to comprehensively summarize the mechanisms of action and anti-inflammatory properties of dietary CLA supplementation and evaluate the potential uses of CLA in human health and disease.

Diet, nutrients and metabolism: cogs in the wheel driving Alzheimer's disease pathology?

Alzheimer's disease (AD), the most common form of dementia, is a chronic, progressive neurodegenerative disease that manifests clinically as a slow global decline in cognitive function, including deterioration of memory, reasoning, abstraction, language and emotional stability, culminating in a patient with end-stage disease, totally dependent on custodial care. With a global ageing population, it is predicted that there will be a marked increase in the number of people diagnosed with AD in the coming decades, making this a significant challenge to socio-economic policy and aged care. Global estimates put a direct cost for treating and caring for people with dementia at $US604 billion, an estimate that is expected to increase markedly. According to recent global statistics, there are 35.6 million dementia sufferers, the number of which is predicted to double every 20 years, unless strategies are implemented to reduce this burden. Currently, there is no cure for AD; while current therapies may temporarily ameliorate symptoms, death usually occurs approximately 8 years after diagnosis. A greater understanding of AD pathophysiology is paramount, and attention is now being directed to the discovery of biomarkers that may not only facilitate pre-symptomatic diagnosis, but also provide an insight into aberrant biochemical pathways that may reveal potential therapeutic targets, including nutritional ones. AD pathogenesis develops over many years before clinical symptoms appear, providing the opportunity to develop therapy that could slow or stop disease progression well before any clinical manifestation develops.

Fish oil improves motor function, limits blood-brain barrier disruption, and reduces Mmp9 gene expression in a rat model of juvenile traumatic brain injury

The effects of an oral fish oil treatment regimen on sensorimotor, blood-brain barrier, and biochemical outcomes of traumatic brain injury (TBI) were investigated in a juvenile rat model. Seventeen-day old Long-Evans rats were given a 15mL/kg fish oil (2.01g/kg EPA, 1.34g/kg DHA) or soybean oil dose via oral gavage 30min prior to being subjected to a controlled cortical impact injury or sham surgery, followed by daily doses for seven days. Fish oil treatment resulted in less severe hindlimb deficits after TBI as assessed with the beam walk test, decreased cerebral IgG infiltration, and decreased TBI-induced expression of the Mmp9 gene one day after injury. These results indicate that fish oil improved functional outcome after TBI resulting, at least in part from decreased disruption of the blood-brain barrier through a mechanism that includes attenuation of TBI-induced expression of Mmp9.

Elevated tissue omega-3 fatty acid status prevents age-related glucose intolerance in fat-1 transgenic mice

The objective of this study was to investigate the impact of elevated tissue omega-3 (n-3) polyunsaturated fatty acids (PUFA) status on age-related glucose intolerance utilizing the fat-1 transgenic mouse model, which can endogenously synthesize n-3 PUFA from omega-6 (n-6) PUFA. Fat-1 and wild-type mice, maintained on the same dietary regime of a 10% corn oil diet, were tested at two different ages (2 months old and 8 months old) for various glucose homeostasis parameters and related gene expression. The older wild-type mice exhibited significantly increased levels of blood insulin, fasting blood glucose, liver triglycerides, and glucose intolerance, compared to the younger mice, indicating an age-related impairment of glucose homeostasis. In contrast, these age-related changes in glucose metabolism were largely prevented in the older fat-1 mice. Compared to the older wild-type mice, the older fat-1 mice also displayed a lower capacity for gluconeogenesis, as measured by pyruvate tolerance testing (PTT) and hepatic gene expression of phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6 phosphatase (G6Pase). Furthermore, the older fat-1 mice showed a significant decrease in body weight, epididymal fat mass, inflammatory activity (NFκ-B and p-IκB expression), and hepatic lipogenesis (acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) expression), as well as increased peroxisomal activity (70-kDa peroxisomal membrane protein (PMP70) and acyl-CoA oxidase1 (ACOX1) expression). Altogether, the older fat-1 mice exhibit improved glucose homeostasis in comparison to the older wild-type mice. These findings support the beneficial effects of elevated tissue n-3 fatty acid status in the prevention and treatment of age-related chronic metabolic diseases.

Low brain DHA content worsens sensorimotor outcomes after TBI and decreases TBI-induced Timp1 expression in juvenile rats

The effects of dietary modulation of brain DHA content on outcomes after TBI were examined in a juvenile rat model. Long-Evans rats with normal or diet-induced decreases in brain DHA were subjected to a controlled cortical impact or sham surgery on postnatal day 17. Rats with the greatest decreases in brain DHA had the poorest sensorimotor outcomes after TBI. Ccl2, Gfap, and Mmp 9 mRNA levels, and MMP-2 and -9 enzymatic activities were increased after TBI regardless of brain DHA level. Lesion volume was not affected by brain DHA level. In contrast, TBI-induced Timp1 expression was lower in rats on the Deficient diet and correlated with brain DHA level. These data suggest that decreased brain DHA content contributes to poorer sensorimotor outcomes after TBI through a mechanism involving modulation of Timp1 expression.

Streptozotocin-induced diabetes partially attenuates the effects of a high-fat diet on liver and brain fatty acid composition in mice

The current study addresses the effects of a high-fat diet on liver and brain fatty acid compositions and the interaction of that diet with diabetes in a type 1 mouse model. Adult, male, normal and streptozotocin-induced diabetic C57BL/6 mice were fed standard (14 % kcal from fat) or high-fat (54 % kcal from fat, hydrogenated vegetable shortening and corn oil) diets for 8 weeks. Liver and whole brain total phospholipid fatty acid compositions were then determined by TLC/GC. In the liver of non-diabetic mice, the high-fat diet increased the percentages of 18:1n-9, 20:4n-6, and 22:5n-6 and decreased 18:2n-6 and 22:6n-3. Diabetes increased 16:0 in liver, and decreased 18:1n-7 and 20:4n-6. The effects of the high-fat diet on liver phospholipids in diabetic mice were similar to those in non-diabetic mice, or were of smaller magnitude. In the brain, the high-fat diet increased 18:0 and 20:4n-6 of non-diabetic, but not diabetic mice. Brain 22:5n-6 acid was increased by the high-fat diet in both non-diabetic and diabetic mice, but this increase was smaller in diabetic mice. Diabetes alone did not alter the percentage of any individual fatty acid in brain. This indicates that the effects of a high-fat diet on liver and brain phospholipid fatty acid compositions are partially attenuated by concomitant hyperglycemia with hypoinsulinemia.

Short-term, high-fat diet increases the expression of key intestinal genes involved in lipoprotein metabolism in healthy men

BACKGROUND

The modulation of cholesterol and fatty acid homeostasis by dietary fatty acids is thought to be mediated by changes in the expression of key intestinal genes involved in lipoprotein metabolism. However, the short-term effect of dietary fat intake on the expression of these genes has not been fully investigated in humans.

OBJECTIVE

To test whether short-term changes in dietary fatty acid intake affect the expression of key intestinal genes involved in lipoprotein metabolism, we conducted a randomized, double-blind, crossover study in 12 nonobese, healthy men with normal plasma lipid profiles.

DESIGN

Participants were subjected to the following 2 intensive 3-d dietary interventions under isocaloric conditions: 1) a high-fat diet (37% of energy from fat and 50% of energy from carbohydrates) and 2) a low-fat diet (25% of energy from fat and 62% of energy from carbohydrates). Expressions of key genes involved in lipoprotein metabolism were compared by using real-time polymerase chain reaction quantification on duodenal biopsy specimens obtained in a fasting state after each diet.

RESULTS

After the 3-d high-fat diet, plasma cholesterol, LDL cholesterol, and HDL cholesterol concentrations were significantly higher than concentrations observed after the low-fat diet was consumed. The high-fat diet also resulted in significant increases in the intestinal messenger RNA expression of several key genes involved in lipoprotein metabolism. Plasma triglycerides and apolipoprotein B-48 concentrations were significantly lower after the high-fat diet than after the low-fat diet.

CONCLUSION

These findings suggest that short-term exposure to a high-fat diet upregulates the expression of key genes involved in lipid and lipoprotein metabolism at the enterocyte level. This trial was registered at clinicaltrials.gov as NCT01806441.

Fatty acids modulate cytokine and chemokine secretion of stimulated human whole blood cultures in diabetes

Fatty acids, uric acid and glucose are thought to contribute to subclinical inflammation associated with diabetes mellitus. We tested whether co-incubation of free fatty acids and uric acid or glucose influences the secretion of immune mediators from stimulated human whole blood in vitro. Fresh whole blood samples from 20 healthy subjects, 20 patients with type 1 diabetes and 23 patients with type 2 diabetes were incubated for 24 h with palmitic acid (PAL), linolenic acid (LIN) or eicosapentaenoic acid (EPA) alone or together with elevated concentrations of uric acid or glucose. Concentrations of proinflammatory cytokines interleukin (IL)-1β, IL-2, IL-12(p70), IL-18, IFN-γ, of regulatory cytokines IL-4, IL-10, IL-17 and chemokine CCL2 (MCP-1) were measured by multiplex-bead technology from supernatants. Co-incubation of fatty acids with uric acid resulted in a significant reduction of IL-10, IL-12(p70), IFN-γ and CCL2 (MCP-1) concentrations in supernatants compared to incubation with uric acid alone (P < 0·0001). In contrast, IL-18 was up-regulated upon co-stimulation with fatty acids and uric acid. Similarly, co-incubation of fatty acids with glucose diminished secretion of IL-10, IFN-γ and CCL2 (monocyte chemotactic protein-1), while IL-8 was up-regulated (P < 0·001). Samples from healthy and diabetic subjects did not differ after adjustment for age, sex, body mass index and diabetes type. All three fatty acids similarly influenced whole blood cytokine release in vitro and modulated uric acid or glucose-stimulated cytokine secretion. Although the ω-3-fatty acid EPA showed slightly stronger effects, further studies are required to elaborate the differential effects of PAL, LIN and EPA on disease risk observed previously in epidemiological studies.

Functional Role of PPARs in Ruminants: Potential Targets for Fine-Tuning Metabolism during Growth and Lactation

Characterization and biological roles of the peroxisome proliferator-activated receptor (PPAR) isotypes are well known in monogastrics, but not in ruminants. However, a wealth of information has accumulated in little more than a decade on ruminant PPARs including isotype tissue distribution, response to synthetic and natural agonists, gene targets, and factors affecting their expression. Functional characterization demonstrated that, as in monogastrics, the PPAR isotypes control expression of genes involved in lipid metabolism, anti-inflammatory response, development, and growth. Contrary to mouse, however, the PPARγ gene network appears to controls milk fat synthesis in lactating ruminants. As in monogastrics, PPAR isotypes in ruminants are activated by long-chain fatty acids, therefore, making them ideal candidates for fine-tuning metabolism in this species via nutrients. In this regard, using information accumulated in ruminants and monogastrics, we propose a model of PPAR isotype-driven biological functions encompassing key tissues during the peripartal period in dairy cattle.

Effects of trans-fatty acids on liver lipid metabolism in mice fed on diets showing different fatty acid composition

AIM

Our aim was to investigate the effects of trans-fatty acids (TFA) on liver lipid metabolism in mice fed on experimental diets rich in either oleic or linoleic acid.

METHODS

Twenty-two male CF1 mice (22.0 ± 0.1 g) were fed with diets rich in corn oil or olive oil, supplemented or not with TFA (0.75 g TFA/100 g diet), for 4 weeks. Changes in triacylglycerol content, the activity and expression of enzymes involved in lipogenesis and fatty acid oxidation were measured.

RESULTS

Supplementation of an olive oil-rich diet with TFA increased liver triacylglycerols, the activity and expression of lipogenic enzymes and sterol regulatory element-binding protein SREBP-1a expression. By contrast, when TFA were added to a corn oil-rich diet, they did not modify these parameters. No significant differences were observed among the experimental groups in the activity and expression of carnitine palmitoyltransferase-Ia, body and liver weights or serum triacylglycerol concentrations.

CONCLUSIONS

The effect of TFA on liver fat accumulation depends on the dietary fatty acid composition. Steatosis induced by TFA when included in an olive oil diet (but not in a corn oil diet) was associated with an increased lipogenesis but not with a decreased fatty acid oxidation in animals fed on the olive oil diet. This metabolic change is mediated by SREBP-1a but not by SREBP-1c, and seems to be independent of insulin.

Fatty acid binding protein 3 (fabp3) is associated with insulin, lipids and cardiovascular phenotypes of the metabolic syndrome through epigenetic modifications in a Northern European family population

Background

Fatty acid-binding proteins (FABPs) play regulatory roles at the nexus of lipid metabolism and signaling. Dyslipidemia in clinical manifestation frequently co-occurs with obesity, insulin resistance and hypertension in the Metabolic Syndrome (MetS). Animal studies have suggested FABPs play regulatory roles in expressing MetS phenotypes. In our family cohort of Northern European descent, transcript levels in peripheral white blood cells (PWBCs) of a key FABPs, FABP3, is correlated with the MetS leading components. However, evidence supporting the functions of FABPs in humans using genetic approaches has been scarce, suggesting FABPs may be under epigenetic regulation. The objective of this study was to test the hypothesis that CpG methylation status of a key regulator of lipid homeostasis, FABP3, is a quantitative trait associated with status of MetS phenotypes in humans.

Methods

We used a mass-spec based quantitative method, EpiTYPER®, to profile a CpG island that extends from the promoter to the first exon of the FABP3 gene in our family-based cohort of Northern European descent (n=517). We then conducted statistical analysis of the quantitative relationship of CpG methylation and MetS measures following the variance-component association model. Heritability of each methylation and the effect of age and sex on CpG methylation were also assessed in our families.

Results

We find that methylation levels of individual CpG units and the regional average are heritable and significantly influenced by age and sex. Regional methylation was strongly associated with plasma total cholesterol (p=0.00028) and suggestively associated with LDL-cholesterol (p=0.00495). Methylation at individual units was significantly associated with insulin sensitivity, lipid particle sizing and diastolic blood pressure (p<0.0028, corrected for multiple testing for each trait). Peripheral white blood cell (PWBC) expression of FABP3 in a separate group of subjects (n=128) negatively correlated with adverse profiles of metabolism (β_WHR = −0.72; β_LDL-c = −0.53) while positively correlated with plasma adiponectin (β=0.24). Further, we show that differential methylation of FABP3 affects binding activity with nuclear proteins from heart tissue. This region that we found under methylation regulation overlaps with a region actively modified by histone codes in the newly available ENCODE data.

Conclusions

Our findings suggest that DNA methylation of FABP3 strongly influences MetS, and this may have important implications for cardiovascular disease.

The role of long-chained marine N-3 polyunsaturated Fatty acids in cardiovascular disease

This paper reviews the current evidence regarding long-chained marine omega-3 polyunsaturated fatty acids (PUFAs) and cardiovascular disease (CVD), their possible mechanisms of action, and results of clinical trials. Also, primary and secondary prevention trials as studies on antiarrhythmic effects and meta-analyses are summarized. However, the individual bioavailability of n-3 PUFAs along with the highly different study designs and estimations of FAs intake or supplementation dosages in patient populations with different background intake of n-3 PUFAs might be some of the reasons for the inconsistent findings of the studies evaluating the impact of n-3 PUFAs on CVD. The question of an optimum dose of n-3 PUFAs or whether there exists a dose-response relation for n-3 PUFA supplementation is widely discussed. Moreover, the difficulties in interpreting meta-analyses are clearly demonstrated by two recently published meta-analyses (Rizos et al. and Delgado Lista et al.), evaluating the efficacy of n-3 PUFAs on CVD, including 12 common studies, but drawing opposite conclusions. We definitely need more large-scale, randomized clinical trials of long duration, also reporting harmful effects of n-3 PUFAs.

Potent PPARα activator derived from tomato juice, 13-oxo-9,11-octadecadienoic acid, decreases plasma and hepatic triglyceride in obese diabetic mice

Dyslipidemia is a major risk factor for development of several obesity-related diseases. The peroxisome proliferator-activated receptor α (PPARα) is a ligand-activated transcription factor that regulates energy metabolism. Previously, we reported that 9-oxo-10,12-octadecadienoic acid (9-oxo-ODA) is presented in fresh tomato fruits and acts as a PPARα agonist. In addition to 9-oxo-ODA, we developed that 13-oxo-9,11-octadecadienoic acid (13-oxo-ODA), which is an isomer of 9-oxo-ODA, is present only in tomato juice. In this study, we explored the possibility that 13-oxo-ODA acts as a PPARα agonist in vitro and whether its effect ameliorates dyslipidemia and hepatic steatosis in vivo. In vitro luciferase assay experiments revealed that 13-oxo-ODA significantly induced PPARα activation; moreover, the luciferase activity of 13-oxo-ODA was stronger than that of 9-oxo-ODA and conjugated linoleic acid (CLA), which is a precursor of 13-oxo-ODA and is well-known as a potent PPARα activator. In addition to in vitro experiment, treatment with 13-oxo-ODA decreased the levels of plasma and hepatic triglycerides in obese KK-Ay mice fed a high-fat diet. In conclusion, our findings indicate that 13-oxo-ODA act as a potent PPARα agonist, suggesting a possibility to improve obesity-induced dyslipidemia and hepatic steatosis.

Inflammation-related gene expression by lipid oxidation-derived products in the progression of atherosclerosis

Vascular areas of atherosclerotic development persist in a state of inflammation, and any further inflammatory stimulus in the subintimal area elicits a proatherogenic response; this alters the behavior of the artery wall cells and recruits further inflammatory cells. In association with the inflammatory response, oxidative events are also involved in the development of atherosclerotic plaques. It is now unanimously recognized that lipid oxidation-derived products are key players in the initiation and progression of atherosclerotic lesions. Oxidized lipids, derived from oxidatively modified low-density lipoproteins (LDLs), which accumulate in the intima, strongly modulate inflammation-related gene expression, through involvement of various signaling pathways. In addition, considerable evidence supports a proatherogenic role of a large group of potent bioactive lipids called eicosanoids, which derive from oxidation of arachidonic acid, a component of membrane phospholipids. Of note, LDL lipid oxidation products might regulate eicosanoid production, modulating the enzymatic degradation of arachidonic acid by cyclooxygenases and lipoxygenases; these enzymes might also directly contribute to LDL oxidation. This review provides a comprehensive overview of current knowledge on signal transduction pathways and inflammatory gene expression, modulated by lipid oxidation-derived products, in the progression of atherosclerosis.

cis-9,trans-11,cis-15 and cis-9,trans-13,cis-15 CLNA mixture activates PPARα in HEK293 and reduces triacylglycerols in 3T3-L1 cells

Scientific research is constantly working to find new molecules that are effective in preventing excessive accumulation of body fat. The aim of the present work was to assess the potential agonism on PPARα and PPARγ of a conjugated linolenic acid (CLNA) isomer mixture, consisting of two CLNA isomers (cis-9,trans-11,cis-15 and cis-9,trans-13,cis-15). Secondly, we aimed to analyze the effects of this mixture on triacylglycerol accumulation in 3T3-L1 mature adipocytes. Luciferase transactivation assay was used to analyze whether the CLNA mixture activated PPARs. The expression of several enzymes and transcriptional factors involved in the main metabolic pathways that control triacylglycerol accumulation in adipocytes was assessed by real time RT-PCR in 3T3-L1 adipocytes treated for 20 h with the CLNA mixture. The mixture activated PPRE in cells with PPARα receptor over-expression, but not those with PPARγ over-expression. Decreased triacylglycerol was found in treated adipocytes. The lowest dose (10 μM) increased HSL expression and the highest dose (100 μM) increased ATGL gene expression. The other genes analyzed remained unchanged. The hypothesis of an anti-obesity action of the analyzed CLNA mixture, based on increased lipid mobilization in adipose tissue, can be proposed.

The Role of Hepatic Liver X Receptor α-and Sterol Regulatory Element Binding Protein-1c-Mediated Lipid Disorder in the Pathogenesis of Non-Alcoholic Steatohepatitis in Rats

Liver X receptor α (LXRα) and sterol regulatory element binding protein-1c (SREBP-1c) were studied in rats with non-alcoholic steatohepatitis (NASH) induced by a high-fat diet. Forty 5-week-old rats were fed either a high-fat diet ( n = 30) or a normal diet ( n = 10) for 9, 13 or 17 weeks. The mRNA and protein levels for LXRα and SREBP-1c were measured at each time point, as was fatty acid synthase (FAS) activity and the serum levels of free fatty acid (FFA) and triglyceride (TG). The mRNA and protein levels for LXRα and SREBP-1c, FAS activity and serum levels of FFA and TG all significantly increased from week 9 in the high-fat diet rats versus controls. In conclusion, a high-fat diet upregulates LXRα which, in turn, upregulates SREBP-1c, increasing the activity of FAS and FFA and accumulation of TG in hepatocytes. Thus, LXRα and SREBP-1c contribute to the development of NASH.

Conjugated linoleic acid (CLA): is it time to supplement asthma therapy?

The limitations and side effects of existing asthma therapies prompt interest in complementary and alternative therapies. Conjugated linoleic acids (CLA) are a family of natural fatty acids found primarily in beef and dairy products. These molecules have a variety of biological properties which suggest potential benefit in asthma, including effects on energy regulation, lipid metabolism, inflammation and immune function. Here we review the evidence for these effects from pre-clinical and clinical studies, their significance in the context of human asthma, and discuss the potential role for CLA supplementation in asthma management.

Peroxisome proliferator-activated receptor alpha target genes

The peroxisome proliferator-activated receptor alpha (PPARα) is a ligand-activated transcription factor involved in the regulation of a variety of processes, ranging from inflammation and immunity to nutrient metabolism and energy homeostasis. PPARα serves as a molecular target for hypolipidemic fibrates drugs which bind the receptor with high affinity. Furthermore, PPARα binds and is activated by numerous fatty acids and fatty acid-derived compounds. PPARα governs biological processes by altering the expression of a large number of target genes. Accordingly, the specific role of PPARα is directly related to the biological function of its target genes. Here, we present an overview of the involvement of PPARα in lipid metabolism and other pathways through a detailed analysis of the different known or putative PPARα target genes. The emphasis is on gene regulation by PPARα in liver although many of the results likely apply to other organs and tissues as well.