Docosahexaenoic acid synthesis in human skin fibroblasts involves peroxisomal retroconversion of tetracosahexaenoic acid

Peroxisomes and PPARs: Emerging role as master regulators of cancer metabolism

Cancer is a disease characterized by the acquisition of a multitude of unique traits. It has long been understood that cancer cells divert significantly from normal cell metabolism. The most obvious of metabolic changes is that cancer cells strongly rely on glucose conversion by aerobic glycolysis. In addition, they also regularly develop mechanisms to use lipids and fatty acids for their energy needs. Peroxisomes lie central to these adaptive changes of lipid metabolism. Peroxisomes are metabolic organelles that take part in over 50 enzymatic reactions crucial for cellular functioning. Thus, they are essential for an effective and comprehensive use of lipids' energy supplied to cells. Cancer cells display a substantial increase in the biogenesis of peroxisomes and an increased expression of proteins necessary for the enzymatic functions provided by peroxisomes. Moreover, the enzymatic conversion of FAs in peroxisomes is a significant source of reactive oxygen and nitrogen species (ROS/RNS) that strongly impact cancer malignancy. Important regulators in peroxisomal FA oxidation and ROS/RNS generation are the transcription factors of the peroxisome proliferator-activated receptor (PPAR) family. This review describes the metabolic changes in tumorigenesis and cancer progression influenced by peroxisomes. We will highlight the ambivalent role that peroxisomes and PPARs play in the different stages of tumor development and summarize our current understanding of how to capitalize on the comprehension of peroxisomal biology for cancer treatment.

Carnitine O-octanoyltransferase (CROT) deficiency in mice leads to an increase of omega-3 fatty acids

Introduction: Carnitine O-octanoyltransferase (CROT) is a well-established peroxisomal enzyme involved in liver fatty acid oxidation, but less is known about its recently discovered role in promoting vascular calcification, and whether CROT-dependent liver metabolism contributes to the latter. To date, CROT function in the context of calcification potential has been conducted in the dyslipidemic low-density lipoprotein receptor-deficient (Ldlr-/-) mice. Objectives: To differentiate peroxisome and CROT-dependent lipid biology from that of lipoprotein-mediated lipid biology, we therefore conducted a metabolomic analysis of the liver and plasma of normolipidemic CROT-deficient (Crot-/-) mice. Methods: We performed LC-MS-based metabolomics on liver and plasma derived from Crot-/- and Crot +/- mice and sibling Crot+/+ mice, using a dual-phase metabolite extraction protocol, and multiple LC-MS acquisition strategies. Results: We identified between 79 to 453 annotated metabolites from annotated metabolites from liver samples, and 117 to 424 annotated metabolites from plasma samples. Through differential abundance analysis, we determined that omega-3 fatty acids such as EPA, DPA, and DHA were higher in the liver of Crot-/- and Crot +/- mice than Crot+/+ mice. EPA were higher in plasma of Crot-/- mice than Crot+/+ mice. We also determined that the anti-inflammatory dicarboxylic acids, tetradecanedioic acid and azelaic acid, were higher in the plasma of CROT-deficient mice. Conclusion: Our study associated genetic CROT deletion with increased levels of anti-inflammatory molecules in mouse liver and plasma. These results suggest a potential mechanism for anti-calcification effects of CROT suppression and the potential use of omega-3 fatty acids as biomarkers for future CROT inhibition therapies.

Understanding the Role of Polyunsaturated Fatty Acids in the Development and Prevention of Cancer

Polyunsaturated fatty acids (PUFAs), notably omega-3 (n-3) and omega-6 (n-6), have received much attention owing to their multifaceted effects not only in the management of diverse pathological conditions but also in the maintenance of overall health of an individual. A disproportionately high n-6 to n-3 ratio contributes to the development of various disorders including cancer, which ranks as a leading cause of death worldwide with profound social and economic burden. Epidemiological studies and clinical trials combined with the animal and cell culture models have demonstrated the beneficial effects of n-3 PUFAs in reducing the risk of various cancer types including breast, prostate and colon cancer. The anti-cancer actions of n-3 PUFAs are mainly attributed to their role in the modulation of a wide array of cellular processes including membrane dynamics, apoptosis, inflammation, angiogenesis, oxidative stress, gene expression and signal transduction pathways. On the contrary, n-6 PUFAs have been shown to exert pro-tumor actions; however, the inconsistent findings and controversial data emphasize upon the need to further investigation. Nevertheless, one of the biggest challenges in future is to optimize the n-6 to n-3 ratio despite the genetic predisposition, age, gender and disease severity. Moreover, a better understanding of the potential risks and benefits as well as the cellular and molecular mechanisms of the basic actions of these PUFAs is required to explore their role as adjuvants in cancer therapy. All these aspects will be reviewed in this chapter.

Omega-3 long-chain polyunsaturated fatty acids: Metabolism and health implications

Recently, omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFAs) have gained substantial interest due to their specific structure and biological functions. Humans cannot naturally produce these fatty acids (FAs), making it crucial to obtain them from our diet. This comprehensive review details n-3 LC-PUFAs and their role in promoting and maintaining optimal health. The article thoroughly analyses several sources of n-3 LC-PUFAs and their respective bioavailability, covering marine, microbial and plant-based sources. Furthermore, we provide an in-depth analysis of the biological impacts of n-3 LC-PUFAs on health conditions, with particular emphasis on cardiovascular disease (CVD), gastrointestinal (GI) cancer, diabetes, depression, arthritis, and cognition. In addition, we highlight the significance of fortification and supplementation of n-3 LC-PUFAs in both functional foods and dietary supplements. Additionally, we conducted a detailed analysis of the several kinds of n-3 LC-PUFAs supplements currently available in the market, including an assessment of their recommended intake, safety, and effectiveness. The dietary guidelines associated with n-3 LC-PUFAs are also highlighted, focusing on the significance of maintaining a well-balanced intake of n-3 PUFAs to enhance health benefits. Lastly, we highlight future directions for further research in this area and their potential implications for public health.

Dietary Implications of Polyunsaturated Fatty Acids during Pregnancy and in Neonates

Certain limitations exist for animals to modify fatty acid changes. Besides the role of arachidonic acid (AA), docosahexaenoic acid (DHA) and other 20-carbon long-chain polyunsaturated fatty acids (LCPUFAs) for the synthesis of inflammatory mediators as eicosanoids, different LCPUFAs have many other effects, including their abilities to regulate gene expression and downstream events. LCPUFAs are susceptible to autoxidation, which is prevented by the action of antioxidants in the form of enzymes like superoxide dismutases, catalases and peroxidases, as well as antioxidant compounds that protect against oxidation or repair the damage caused. Under normal conditions, the fetus needs both essential fatty acids (EFAs) and LCPUFAs, which are obtained from its mother by placental transfer. In early pregnancy, dietary derived fatty acids are accumulated in maternal adipose tissue. However, during late pregnancy, corresponding to the period of the highest fetal growth, maternal adipose tissue becomes catabolic and LCPUFAs are released into the circulation by adipose lipolytic activity. The released LCPUFAs are taken up by maternal liver to be esterified and released back to the circulation as triacylglycerides (TAGs) in very-low-density lipoprotein (VLDL) that become available to the placenta to be transferred to the fetus in the form of non-esterified fatty acids (NEFAs). An enhanced adipose tissue lipolysis is maintained around parturition and esterified LCPUFAs are diverted to mammary glands thanks to an increased activity of lipoprotein lipase for milk production. Throughout this process, LCPUFAs become available to the newborn during suckling. The important role of both DHA and AA for the development of the nervous system and for growth has motivated their dietary supplement during different postnatal stages. This has been especially important in preterm infants both because under normal conditions, the fetus acquires most of these fatty acids during late pregnancy, and because the immaturity of the enzyme systems for the synthesis of AA and DHA from their respective EFAs.

Exogenous tetracosahexaenoic acid modifies the fatty acid composition of human primary T lymphocytes and Jurkat T cell leukemia cells contingent on cell type

Tetracosahexaenoic acid (24:6ω-3) is an intermediate in the conversion of 18:3ω-3 to 22:6ω-3 in mammals. There is limited information about whether cells can assimilate and metabolize exogenous 24:6ω-3. This study compared the effect of incubation with 24:6ω-3 on the fatty acid composition of two related cell types, primary CD3+ T lymphocytes and Jurkat T cell leukemia, which differ in the integrity of the polyunsaturated fatty acid (PUFA) biosynthesis pathway. 24:6ω-3 was only detected in either cell type when cells were incubated with 24:6ω-3. Incubation with 24:6ω-3 induced similar increments in the amount of 22:6ω-3 in both cell types and modified the homeoviscous adaptations fatty acid composition induced by activation of T lymphocytes. The effect of incubation with 18:3ω-3 compared to 24:6ω-3 on the increment in 22:6ω-3 was tested in Jurkat cells because primary T cells cannot convert 18:3ω-3 to 22:6ω-3. The increment in the 22:6ω-3 content of Jurkat cells incubated with 24:6ω-3 was 19.5-fold greater than that of cells incubated with 18:3ω-3. Acyl-coA oxidase siRNA knockdown decreased the amount of 22:6ω-3 and increased the amount of 24:6ω-3 in Jurkat cells. These findings show exogenous 24:6ω-3 can be incorporated into primary human T lymphocytes and Jurkat cells and induces changes in fatty acid composition consistent with its conversion to 22:6ω-3 via a mechanism involving peroxisomal β-oxidation that is regulated independently from the integrity of the upstream PUFA synthesis pathway. One further implication is that consuming 24:6ω-3 may be an effective alternative means of achieving health benefits attributed to 20:5ω-3 and 22:6ω-3.

Increases in plasma n-3 tetracosapentaenoic acid and tetracosahexaenoic acid following 12 weeks of EPA, but not DHA, supplementation in women and men

Dietary feeding and stable isotope studies in rodents support that the 24-carbon omega-3 polyunsaturated fatty acids, tetracosapentaenoic acid (24:5n-3, TPAn-3) and tetracosahexaenoic acid (24:6n-3, THA), are immediate precursors to docosahexaenoic acid (DHA, 22:6n-3). In this study, we assessed for the first time, changes in TPAn-3 or THA levels following omega-3 PUFA supplementation in humans, providing insight into human omega-3 PUFA metabolism. In this secondary analysis of a double-blind randomized control trial, women and men (19 - 30 years, n = 10 - 14 per sex, per diet) were supplemented with 3 g/day EPA, DHA, or olive oil control for 12 weeks. Plasma TPAn-3 and THA concentrations were determined by gas chromatography-mass spectrometry to determine changes following supplementation in a sex-specific manner (sex x time). EPA supplementation significantly increased (p < 0.0001) plasma TPAn-3 by 215% (1.3 ± 0.1 - 4.1 ± 0.7, nmol/mL ± SEM) and THA by 112% (1.7 ± 0.2 - 3.6 ± 0.5, nmol/mL ± SEM). Furthermore, women had 111% and 99% higher plasma TPAn-3 and THA in the EPA supplemented group compared to men (p < 0.0001). There were no significant effects of time on plasma TPAn-3 or THA concentrations in the DHA supplemented or olive oil supplemented groups. In conclusion, EPA, but not DHA, supplementation in humans increased plasma TPAn-3 and THA levels, suggesting that THA accumulates prior to conversion to DHA in the n-3 PUFA synthesis pathway. Furthermore, women generally exhibit higher plasma TPAn-3 and THA concentrations compared with men, suggesting that women have a greater ability to accumulate 24-carbon n-3 PUFA in plasma via EPA and DPAn-3 elongation, which may explain the known higher DHA levels in women. Summary: In this secondary analysis of a double-blind randomized control trial, we assessed changes in omega-3 (n-3) tetracosapentaenoic acid (24:5n-3, TPAn-3) and tetracosahexaenoic acid (24:6n-3, THA) plasma levels in women and men (19 - 30 years, n = 10 - 14 per sex, per diet) following 12-weeks of n-3 PUFA supplementation (3 g/day EPA, DHA or olive oil). Women had higher plasma TPAn-3 in all supplementation groups and higher THA levels in the EPA and olive oil groups (p < 0.0001) compared to men. EPA supplementation increased (p < 0.0001) plasma TPAn-3 by 215% (1.3 ± 0.1 - 4.1 ± 0.7, nmol/mL ± SEM) and THA by 112% (1.7 ± 0.2 - 3.6 ± 0.5, nmol/mL ± SEM), but DHA supplementation had no effect. For the first time in humans, we show that plasma TPAn-3 and THA levels are higher in women and increased with EPA, but not DHA supplementation, suggesting an accumulation of THA prior to conversion to DHA in the n-3 PUFA synthesis pathway.

Dysfunctional peroxisomal lipid metabolisms and their ocular manifestations

Retina is rich in lipids and dyslipidemia causes retinal dysfunction and eye diseases. In retina, lipids are not only important membrane component in cells and organelles but also fuel substrates for energy production. However, our current knowledge of lipid processing in the retina are very limited. Peroxisomes play a critical role in lipid homeostasis and genetic disorders with peroxisomal dysfunction have different types of ocular complications. In this review, we focus on the role of peroxisomes in lipid metabolism, including degradation and detoxification of very-long-chain fatty acids, branched-chain fatty acids, dicarboxylic acids, reactive oxygen/nitrogen species, glyoxylate, and amino acids, as well as biosynthesis of docosahexaenoic acid, plasmalogen and bile acids. We also discuss the potential contributions of peroxisomal pathways to eye health and summarize the reported cases of ocular symptoms in patients with peroxisomal disorders, corresponding to each disrupted peroxisomal pathway. We also review the cross-talk between peroxisomes and other organelles such as lysosomes, endoplasmic reticulum and mitochondria.

Metabolic Dynamics and Prediction of Gestational Age and Time to Delivery in Pregnant Women

Metabolism during pregnancy is a dynamic and precisely programmed process, the failure of which can bring devastating consequences to the mother and fetus. To define a high-resolution temporal profile of metabolites during healthy pregnancy, we analyzed the untargeted metabolome of 784 weekly blood samples from 30 pregnant women. Broad changes and a highly choreographed profile were revealed: 4,995 metabolic features (of 9,651 total), 460 annotated compounds (of 687 total), and 34 human metabolic pathways (of 48 total) were significantly changed during pregnancy. Using linear models, we built a metabolic clock with five metabolites that time gestational age in high accordance with ultrasound (R = 0.92). Furthermore, two to three metabolites can identify when labor occurs (time to delivery within two, four, and eight weeks, AUROC ≥ 0.85). Our study represents a weekly characterization of the human pregnancy metabolome, providing a high-resolution landscape for understanding pregnancy with potential clinical utilities.

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Weekly metabolome of maternal blood changes dynamically through healthy pregnancy

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A metabolic clock of five blood metabolites accurately predicts gestational age

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Two to three metabolites identify labor onset within two, four, and eight weeks

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Women with metabolic clocks that outpaced ultrasound evaluation tend to deliver earlier

Eicosapentaenoic acid prevents the progression of intracranial aneurysms in rats

Background

As subarachnoid hemorrhage due to rupture of an intracranial aneurysm (IA) has quite a poor outcome despite of an intensive medical care, development of a novel treatment targeting unruptured IAs based on the correct understanding of pathogenesis is mandatory for social health.

Methods

Using previously obtained gene expression profile data from surgically resected unruptured human IA lesions, we selected G-protein coupled receptor 120 (GPR120) as a gene whose expression is significantly higher in lesions than that in control arterial walls. To corroborate a contribution of GPR120 signaling to the pathophysiology, we used an animal model of IAs and examine the effect of a GPR120 agonist on the progression of the disease. IA lesion was induced in rats through an increase of hemodynamic stress achieved by a one-sided carotid ligation and induced hypervolemia. Eicosapentaenoic acid (EPA) was used as an agonist for GPR120 in this study and its effect on the size of IAs, the thinning of media, and infiltration of macrophages in lesions were examined.

Result

EPA administered significantly suppressed the size of IAs and the degenerative changes in the media in rats. EPA treatment also inhibited infiltration of macrophages, a hallmark of inflammatory responses in lesions. In in vitro experiments using RAW264.7 cells, pre-treatment of EPA partially suppressed lipopolysaccharide-induced activation of nuclear factor-kappa B and also the transcriptional induction of monocyte chemoattractant protein 1 (MCP-1), a major chemoattractant for macrophages to accumulate in lesions. As a selective agonist of GPR120, TUG-891, could reproduce the effect of EPA in RAW264.7 cells, EPA presumably acted on this receptor to suppress inflammatory responses. Consistently, EPA remarkably suppressed MCP-1 expression in lesions, suggesting the in vivo relevance of in vitro studies.

Conclusions

These results combined together suggest the potential of the medical therapy targeting GPR120 or using EPA to prevent the progression of IAs.

The highly unnatural fatty acid profile of cells in culture

The fatty acid profile of cells in culture are unlike those of natural cells with twice the monounsaturated (MUFA) and half the polyunsaturated fatty acids (PUFA) level (Mol%). This is not due to cell lines primarily being derived from cancers but is due to limited access to lipid and an inability to make PUFA de novo as vertebrate cells. Classic culture methods use media with 10% serum (the only exogenous source of lipid). Fetal bovine serum (FBS), the serum of choice has a low level of lipid and cholesterol compared to other sera and at 10% of media provides 2-3% of the fatty acid and cholesterol, 1% of the PUFA and 0.3% of the essential fatty acid linoleic acid (18:2n-6) available to cells in the body. Since vertebrate cell lines cannot make PUFA they synthesise MUFA, offsetting their PUFA deficit and reducing their fatty acid diversity. Stem and primary cells in culture appear to be similarly affected, with a rapid loss of their natural fatty acid compositions. The unnatural lipid composition of cells in culture has substantial implications for examining natural stems cell in culture, and for investigations of cellular mechanisms using cell lines based on the pervasive influence of fats.

Updates to the n-3 polyunsaturated fatty acid biosynthesis pathway: DHA synthesis rates, tetracosahexaenoic acid and (minimal) retroconversion

N-3 polyunsaturated fatty acids (PUFA) and the numerous families of lipid mediators derived from them collectively regulate numerous biological processes. The mechanisms by which n-3 PUFA regulate biological processes begins with an understanding of the n-3 biosynthetic pathway that starts with alpha-linolenic acid (18:3n-3) and is commonly thought to end with the production of docosahexaenoic acid (DHA, 22:6n-3). However, our understanding of this pathway is not as complete as previously believed. In the current review we provide a background of the evidence supporting the pathway as currently understood and provide updates from recent studies challenging three central dogma of n-3 PUFA metabolism. By building on nearly three decades of research primarily in cell culture and oral dosing studies, recent evidence presented focuses on in vivo kinetic modelling and compound-specific isotope abundance studies in rodents and humans that have been instrumental in expanding our knowledge of the pathway. Specifically, we highlight three main updates to the n-3 PUFA biosynthesis pathway: (1) DHA synthesis rates cannot be as low as previously believed, (2) DHA is both a product and a precursor to tetracosahexaenoic acid (24:6n-3) and (3) increases in EPA in response to DHA supplementation are not the result of increased retroconversion.

Deficiency or activation of peroxisome proliferator-activated receptor α reduces the tissue concentrations of endogenously synthesized docosahexaenoic acid in C57BL/6J mice

BACKGROUND/OBJECTIVES

Docosahexaenoic acid (DHA), an n-3 long chain polyunsaturated fatty acid (LCPUFA), is acquired by dietary intake or the in vivo conversion of α-linolenic acid. Many enzymes participating in LCPUFA synthesis are regulated by peroxisome proliferator-activated receptor alpha (PPARα). Therefore, it was hypothesized that the tissue accretion of endogenously synthesized DHA could be modified by PPARα.

MATERIALS/METHODS

The tissue DHA concentrations and mRNA levels of genes participating in DHA biosynthesis were compared among PPARα homozygous (KO), heterozygous (HZ), and wild type (WT) mice (Exp I), and between WT mice treated with clofibrate (PPARα agonist) or those not treated (Exp II). In ExpII, the expression levels of the proteins associated with DHA function in the brain cortex and retina were also measured. An n3-PUFA depleted/replenished regimen was applied to mitigate the confounding effects of maternal DHA.

RESULTS

PPARα ablation reduced the hepatic Acox, Fads1, and Fads2 mRNA levels, as well as the DHA concentration in the liver, but not in the brain cortex. In contrast, PPARα activation increased hepatic Acox, Fads1, Fads2 and Elovl5 mRNA levels, but reduced the DHA concentrations in the liver, retina, and phospholipid of brain cortex, and decreased mRNA and protein levels of the brain-derived neurotrophic factor in brain cortex.

CONCLUSIONS

LCPUFA enzyme expression was altered by PPARα. Either PPARα deficiency or activation-decreased tissue DHA concentration is a stimulus for further studies to determine the functional significance.

Metabolic Reprogramming during Microglia Activation

Abstract

Microglia, the specialized macrophages of the brain, can adopt different shapes and functions, some of which may be detrimental for nervous tissue. Similar to other immune cells, the metabolic program may determine the phenotypic features of microglia, and could constitute a therapeutic target in neurological diseases. Because the knowledge on microglial metabolism was sparse we here employed mouse primary microglia cells polarized into a pro- or anti-inflammatory state to define their metabolic features. After stimulation with either IL1β/IFNγ or IL4, the activity of glycolysis, glucose oxidation, glutamine oxidation, mitochondrial and peroxisomal fatty acid β-oxidation, and fatty acid synthesis, was assessed by using radiolabeled substrates. We complemented these data with transcriptome analysis of key enzymes orchestrating these metabolic pathways. Pro-inflammatory microglia exhibit increased glucose and glutamine metabolism and suppress both fatty acid oxidation and to a lesser extent fatty acid synthesis. On the other hand, anti-inflammatory microglia display changes only in fatty acid metabolism upregulating both fatty acid oxidation and fatty acid synthesis. Importantly, also human microglia-like cells differentiated from pluripotent stem cells upregulate glycolysis in pro-inflammatory conditions. Finally, we show that glycolytic enzymes are induced in a pro-inflammatory brain environment in vivo in mice. Taken together, the distinct metabolism in pro- and anti-inflammatory microglia can constitute a target to direct the microglial phenotype.

Relation of Serum Plasmalogens and APOE Genotype to Cognition and Dementia in Older Persons in a Cross-Sectional Study

Using a community sample of 1205 elderly persons, we investigated the associations and potential interactions between Apolipoprotein E (APOE) genotype and serum phosphatidylethanolamine (PlsEtn) on cognition and dementia. For each person, APOE genotype, PlsEtn Biosynthesis value (PBV, the combination of three key PlsEtn species), cognition (the combination of five specific cognitive domains), and diagnosis of dementia was determined. APOE genotype and PBV were observed to be non-interacting (p > 0.05) and independently associated with cognition: APOE (relative to ε3ε3:ε2ε3 (Coef = 0.14, p = 4.2 × 10⁻²); ε3ε4/ε4ε4 (Coef = −0.22, p = 6.2 × 10⁻⁵); PBV (Coef = 0.12, p = 1.7 × 10⁻⁷) and dementia: APOE (relative to ε3ε3:ε2ε3 (Odds Ratio OR = 0.44, p = 3.0 × 10⁻²); ε3ε4/ε4ε4 (OR = 2.1, p = 2.2 × 10⁻⁴)); PBV (OR = 0.61, p = 3.3 × 10⁻⁶). Associations are expressed per standard deviation (SD) and adjusted for serum lipids and demographics. Due to the independent and non-interacting nature of the APOE and PBV associations, the prevalence of dementia in APOE ε3ε4/ε4ε4 persons with high PBV values (>1 SD from mean) was observed to be the same as APOE ε3ε3 persons (14.3% versus 14.0%). Similarly, the prevalence of dementia in APOE ε3ε3 persons with high PBV values was only 5.7% versus 6.7% for APOE ε2ε3 persons. The results of these analyses indicate that the net effect of APOE genotype on cognition and the prevalence of dementia is dependent upon the plasmalogen status of the person.

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.

Docosahexaenoic acid is both a product of and a precursor to tetracosahexaenoic acid in the rat

Tetracosahexaeoic acid (THA; 24:6n-3) is thought to be the immediate precursor of DHA in rodents; however, the relationship between THA and DHA metabolism has not been assessed in vivo. Here, we infused unesterified ²H₅-THA and ¹³C₂₂-DHA, at a steady state, into two groups of male Long-Evans rats and determined the synthesis-secretion kinetics, including daily synthesis-secretion rates of all 20-24 carbon n-3 PUFAs. We determined that the synthesis-secretion coefficient (a measure of the capacity to synthesize a given fatty acid) for the synthesis of DHA from plasma unesterified THA to be 134-fold higher than for THA from DHA. However, when considering the significantly higher endogenous plasma unesterified DHA pool, the daily synthesis-secretion rates were only 7-fold higher for DHA synthesis from THA (96.3 ± 31.3 nmol/d) compared with that for THA synthesis from DHA (11.4 ± 4.1 nmol/d). Furthermore, plasma unesterified THA was converted to DHA and secreted into the plasma at a 2.5-fold faster rate than remaining as THA itself (26.2 ± 6.3 nmol/d), supporting THA's primary role as a precursor to DHA. In conclusion, using a 3 h infusion model in rats, we demonstrate for the first time in vivo that DHA is both a product and a precursor to THA.

Peroxisomes and cancer: The role of a metabolic specialist in a disease of aberrant metabolism

Cancer is irrevocably linked to aberrant metabolic processes. While once considered a vestigial organelle, we now know that peroxisomes play a central role in the metabolism of reactive oxygen species, bile acids, ether phospholipids (e.g. plasmalogens), very-long chain, and branched-chain fatty acids. Immune system evasion is a hallmark of cancer, and peroxisomes have an emerging role in the regulation of cellular immune responses. Investigations of individual peroxisome proteins and metabolites support their pro-tumorigenic functions. However, a significant knowledge gap remains regarding how individual functions of proteins and metabolites of the peroxisome orchestrate its potential role as a pro-tumorigenic organelle. This review highlights new advances in our understanding of biogenesis, enzymatic functions, and autophagic degradation of peroxisomes (pexophagy), and provides evidence linking these activities to tumorigenesis. Finally, we propose avenues that may be exploited to target peroxisome-related processes as a mode of combatting cancer.

Quantitation of Human Whole-Body Synthesis-Secretion Rates of Docosahexaenoic Acid and Eicosapentaenoate Acid from Circulating Unesterified α-Linolenic Acid at Steady State

The rate at which dietary α-linolenic acid (ALA) is desaturated and elongated to its longer-chain n-3 polyunsaturated fatty acid (PUFA) in humans is not agreed upon. In this study, we applied a methodology developed using rodents to investigate the whole-body, presumably hepatic, synthesis-secretion rates of esterified n-3 PUFA from circulating unesterified ALA in 2 healthy overweight women after 10 weeks of low-linoleate diet exposure. During continuous iv infusion of d5-ALA, 17 arterial blood samples were collected from each subject at -10, 0, 10, 20, 40, 60, 80, 100, 120, 150, 180, and 210 min, and at 4, 5, 6, 7, and 8 h after beginning infusion. Plasma esterified d5-n-3 PUFA concentrations were plotted against the infusion time and fit to a sigmoidal curve using nonlinear regression. These curves were used to estimate kinetic parameters using a kinetic analysis developed using rodents. Calculated synthesis-secretion rates of esterified eicosapentaenoate, n-3 docosapentaenoate, docosahexaenoic acid, tetracosapentaenate, and tetracosahexaenoate from circulating unesterified ALA were 2.1 and 2.7; 1.7 and 5.3; 0.47 and 0.27; 0.30 and 0.30; and 0.32 and 0.27 mg/day for subjects S01 and S02, respectively. This study provides new estimates of whole-body synthesis-secretion rates of esterified longer-chain n-3 PUFA from circulating unesterified ALA in human subjects. This method now can be extended to study factors that regulate human whole-body PUFA synthesis-secretion in health and disease.

Peroxisomal Acyl-CoA Oxidase Type 1: Anti-Inflammatory and Anti-Aging Properties with a Special Emphasis on Studies with LPS and Argan Oil as a Model Transposable to Aging

To clarify appropriateness of current claims for health and wellness virtues of argan oil, studies were conducted in inflammatory states. LPS induces inflammation with reduction of PGC1-α signaling and energy metabolism. Argan oil protected the liver against LPS toxicity and interestingly enough preservation of peroxisomal acyl-CoA oxidase type 1 (ACOX1) activity against depression by LPS. This model of LPS-driven toxicity circumvented by argan oil along with a key anti-inflammatory role attributed to ACOX1 has been here transposed to model aging. This view is consistent with known physiological role of ACOX1 in yielding precursors of specialized proresolving mediators (SPM) and with characteristics of aging and related disorders including reduced PGC1-α function and improvement by strategies rising ACOX1 (via hormonal gut FGF19 and nordihydroguaiaretic acid in metabolic syndrome and diabetes conditions) and SPM (neurodegenerative disorders, atherosclerosis, and stroke). Delay of aging to resolve inflammation results from altered production of SPM, SPM improving most aging disorders. The strategic metabolic place of ACOX1, upstream of SPM biosynthesis, along with ability of ACOX1 preservation/induction and SPM to improve aging-related disorders and known association of aging with drop in ACOX1 and SPM, all converge to conclude that ACOX1 represents a previously unsuspected and currently emerging antiaging protein.

Lipid homeostasis and inflammatory activation are disturbed in classically activated macrophages with peroxisomal β-oxidation deficiency

Macrophage activation is characterized by pronounced metabolic adaptation. Classically activated macrophages show decreased rates of mitochondrial fatty acid oxidation and oxidative phosphorylation and acquire a glycolytic state together with their pro-inflammatory phenotype. In contrast, alternatively activated macrophages require oxidative phosphorylation and mitochondrial fatty acid oxidation for their anti-inflammatory function. Although it is evident that mitochondrial metabolism is regulated during macrophage polarization and essential for macrophage function, little is known on the regulation and role of peroxisomal β-oxidation during macrophage activation. In this study, we show that peroxisomal β-oxidation is strongly decreased in classically activated bone-marrow-derived macrophages (BMDM) and mildly induced in alternatively activated BMDM. To examine the role of peroxisomal β-oxidation in macrophages, we used Mfp2^-/- BMDM lacking the key enzyme of this pathway. Impairment of peroxisomal β-oxidation in Mfp2^-/- BMDM did not cause lipid accumulation but rather an altered distribution of lipid species with very-long-chain fatty acids accumulating in the triglyceride and phospholipid fraction. These lipid alterations in Mfp2^-/- macrophages led to decreased inflammatory activation of Mfp2^-/- BMDM and peritoneal macrophages evidenced by impaired production of several inflammatory cytokines and chemokines, but did not affect anti-inflammatory polarization. The disturbed inflammatory responses of Mfp2^-/- macrophages did not affect immune cell infiltration, as mice with selective elimination of MFP2 from myeloid cells showed normal monocyte and neutrophil influx upon challenge with zymosan. Together, these data demonstrate that peroxisomal β-oxidation is involved in fine-tuning the phenotype of macrophages, probably by influencing the dynamic lipid profile during macrophage polarization.

Detection of unusual very-long-chain fatty acid and ether lipid derivatives in the fibroblasts and plasma of patients with peroxisomal diseases using liquid chromatography-mass spectrometry

Metabolic changes occur in patients with peroxisomal diseases owing to impairments in the genes involved in peroxisome function. For diagnostic purposes, saturated very-long-chain fatty acids (VLCFAs) such as C24:0 and C26:0, phytanic acid, pristanic acid, and plasmalogens are often measured as metabolic hallmarks. As the direct pathology of peroxisomal disease is yet to be fully elucidated, we sought to explore the fatty acid species that accumulate in patients with peroxisomal diseases. We developed a method for detecting a range of fatty acids implicated in peroxisomal diseases such as Zellweger syndrome (ZS) and X-linked adrenoleukodystrophy (X-ALD). To this end, we employed an ultra-performance liquid chromatography-mass spectrometry (LC-MS) coupled with negatively charged electrospray ionization. Fatty acids from patients and control subjects were extracted from total lipids by acid-hydrolysis and compared. In accordance with previous results, the amounts of VLCFAs, phytanic acid, and pristanic acid differed between the two groups. We identified extremely long and highly polyunsaturated VLCFAs (ultra-VLC-PUFAs) such as C44:12 in ZS samples. Moreover, three unknown molecules were prominent in control samples but scarcely detectable in ZS samples. LC-MS/MS analysis identified these as 1-alkyl-sn-glycerol 3-phosphates derived from ether lipids containing fatty alcohols such as C16:0, C18:0, or C18:1. Our method provides an approach to observing a wide range of lipid-derived fatty acids and related molecules in order to understand the metabolic changes involved in peroxisomal diseases. This technique can therefore be used in identifying metabolic markers and potential clinical targets for future treatment.

Metabolic dysfunctions in multiple sclerosis: implications as to causation, early detection, and treatment, a case control study

Background

Biochemical changes associated with multiple sclerosis (MS), and its various clinical forms have not been characterized well. Therefore, we investigated the biochemistry of MS in relation to its natural history using targeted lipidomics platforms.

Methods

Cross-sectional serum samples from 24 secondary progressive (SPMS), 100 relapsing remitting (RRMS), 19 primary progressive MS (PPMS), and 55 age-matched control subjects were analyzed by flow injection tandem mass spectrometry for very long chain fatty acid (VLCFA) containing phosphatidyl ethanolamines (PtdEtn), plasmalogen ethanolamines (PlsEtn) and for novel anti-inflammatory gastrointestinal tract acids (GTAs). Changes in analyte levels relative to healthy controls were correlated with the disease stage and disease duration.

Results

RRMS subjects having <13 years disease duration had elevated levels (p < 0.05) of anti-inflammatory metabolites (GTAs) and normal levels (p > 0.05) of mitochondrial stress biomarkers (VLCFA-PtdEtn), compared to controls. SPMS subjects had statistically similar levels of anti-inflammatory metabolites (GTAs), elevated mitochondrial stress metabolites (VLCFA-PtdEtn) and elevated peroxisomal metabolites (PlsEtn) compared to controls (p < 0.05). RRMS subjects with > = 13 years disease duration exhibited metabolic profiles intermediate between short-duration RRMS and SPMS, based on statistical significance. Therefore, RRMS cohort appear to comprise of two metabolically distinct subpopulations. The key clinical discriminator of these two groups was disease duration. PPMS patients exhibited metabolic profiles distinct from RRMS and SPMS.

Conclusions

These data indicate that inflammation and mitochondrial stress are intricately involved in the etiology of MS and that progression in MS can potentially be monitored using serum metabolic biomarkers.

The fatty acid desaturase 2 (FADS2) gene product catalyzes Δ4 desaturation to yield n-3 docosahexaenoic acid and n-6 docosapentaenoic acid in human cells

Docosahexaenoic acid (DHA) is a Δ4-desaturated C22 fatty acid and the limiting highly unsaturated fatty acid (HUFA) in neural tissue. The biosynthesis of Δ4-desaturated docosanoid fatty acids 22:6n-3 and 22:5n-6 are believed to proceed via a circuitous biochemical pathway requiring repeated use of a fatty acid desaturase 2 (FADS2) protein to perform Δ6 desaturation on C24 fatty acids in the endoplasmic reticulum followed by 1 round of β-oxidation in the peroxisomes. We demonstrate here that the FADS2 gene product can directly Δ4-desaturate 22:5n-3→22:6n-3 (DHA) and 22:4n-6→22:5n-6. Human MCF-7 cells lacking functional FADS2-mediated Δ6-desaturase were stably transformed with FADS2, FADS1, or empty vector. When incubated with 22:5n-3 or 22:4n-6, FADS2 stable cells produce 22:6n-3 or 22:5n-6, respectively. Similarly, FADS2 stable cells when incubated with d5-18:3n-3 show synthesis of d5-22:6n-3 with no labeling of 24:5n-3 or 24:6n-3 at 24 h. Further, both C24 fatty acids are shown to be products of the respective C22 fatty acids via elongation. Our results demonstrate that the FADS2 classical transcript mediates direct Δ4 desaturation to yield 22:6n-3 and 22:5n-6 in human cells, as has been widely shown previously for desaturation by fish and many other organisms.

Antiageing Mechanisms of a Standardized Supercritical CO 2 Preparation of Black Jack (Bidens pilosa L.) in Human Fibroblasts and Skin Fragments

The use of topical retinoids to treat skin disorders and ageing can induce local reactions, while oral retinoids are potent teratogens and produce several unwanted effects. This way, efforts to explore complementary care resources should be supported. Based on this, we evaluate the antiageing effects of a supercritical CO₂ extract from Bidens pilosa L. (BPE-CO₂A) containing a standardized multicomponent mixture of phytol, linolenic, palmitic, linoleic, and oleic acids. BPE-CO₂A was assessed for its effects on human dermal fibroblasts (TGF-β1 and FGF levels using ELISA; collagen, elastin, and glycosaminoglycan by colorimetric assays, and mRNA expression of RXR, RAR, and EGFr by qRT-PCR) and human skin fragments (RAR, RXR, collagen, elastin, and glycosaminoglycan by immunohistochemical analysis). Levels of extracellular matrix elements, TGF-β1 and FGF, and EGFr gene expression were significantly increased by BPE-CO₂A. The modulation of RXR and RAR was positively demonstrated after the treatment with BPE-CO₂A or phytol, a component of BPE-CO₂A. The effects produced by BPE-CO₂A were similar to or better than those produced by retinol and retinoic acid. The ability to stimulate extracellular matrix elements, increase growth factors, and modulate retinoid and rexinoid receptors provides a basis for the development of preparation containing BPE-CO₂A as an antiageing/skin-repair agent.

Redox imbalance and morphological changes in skin fibroblasts in typical Rett syndrome

Evidence of oxidative stress has been reported in the blood of patients with Rett syndrome (RTT), a neurodevelopmental disorder mainly caused by mutations in the gene encoding the Methyl-CpG-binding protein 2. Little is known regarding the redox status in RTT cellular systems and its relationship with the morphological phenotype. In RTT patients (n = 16) we investigated four different oxidative stress markers, F2-Isoprostanes (F2-IsoPs), F4-Neuroprostanes (F4-NeuroPs), nonprotein bound iron (NPBI), and (4-HNE PAs), and glutathione in one of the most accessible cells, that is, skin fibroblasts, and searched for possible changes in cellular/intracellular structure and qualitative modifications of synthesized collagen. Significantly increased F4-NeuroPs (12-folds), F2-IsoPs (7.5-folds) NPBI (2.3-folds), 4-HNE PAs (1.48-folds), and GSSG (1.44-folds) were detected, with significantly decreased GSH (-43.6%) and GSH/GSSG ratio (-3.05 folds). A marked dilation of the rough endoplasmic reticulum cisternae, associated with several cytoplasmic multilamellar bodies, was detectable in RTT fibroblasts. Colocalization of collagen I and collagen III, as well as the percentage of type I collagen as derived by semiquantitative immunofluorescence staining analyses, appears to be significantly reduced in RTT cells. Our findings indicate the presence of a redox imbalance and previously unrecognized morphological skin fibroblast abnormalities in RTT patients.

Zellweger syndrome: prenatal and postnatal growth failure with epiphyseal stippling

We present a 2-month-old male affected by Zellweger syndrome, a rare peroxisomal disorder. The diagnosis was supported by clinical and radiological findings and established by biochemical tests. The characteristic radiological features included anomalous ossification (epiphyseal stippling). We also discuss main differential diagnoses of epiphyseal stippling and a brief literature review.

The multifaceted effects of omega-3 polyunsaturated Fatty acids on the hallmarks of cancer

Omega-3 polyunsaturated fatty acids, in particular eicosapentaenoic acid, and docosahexaenoic acid have been shown to have multiple beneficial antitumour actions that affect the essential alterations that dictate malignant growth. In this review we explore the putative mechanisms of action of omega-3 polyunsaturated fatty acid in cancer protection in relation to self-sufficiency in growth signals, insensitivity to growth-inhibitory signals, apoptosis, limitless replicative potential, sustained angiogenesis, and tissue invasion, and how these will hopefully translate from bench to bedside.

Plasma levels of n-3 fatty acids in bipolar patients: deficit restricted to DHA

Epidemiological studies suggest that n-3 polyunsaturated fatty acid (n-3 FA) deficiency is a risk factor for bipolar disorders (BDs). The aim of this study was to determine whether such a deficit does exist in patients with BD and to characterize the overall plasma fatty acid (FA) profile in these patients. Using gas chromatography/mass spectrometry, we measured fasting plasma levels of 15 FAs in 42 patients diagnosed with BD according to DSM-IV criteria and in 57 age- and gender-matched healthy controls. Plasma docosahexaenoic acid (DHA) levels were significantly decreased in bipolar patients (p < 0.001 versus healthy controls). Compared with controls, patients had higher plasma levels of all other FAs, including arachidonic acid (AA, p < 0.001), alpha-linolenic acid (ALA, p < 0.001), and eicosapentaenoic acid (EPA) (p < 0.001). Although in the present study we observed significant DHA deficits in the plasma of bipolar patients our findings do not support the therapeutic use of ALA and/or EPA supplementation. DHA may provide a basis for possible pharmacological intervention in psychiatric disorders at the level of second messengers linked to the phosphatidylinositol cycle. Finally, measurement of FA levels in plasma seems to be more reliable and reproducible than assays of erythrocyte FA content.

Omega 3 fatty acids and inborn errors of metabolism

A number of studies are investigating the role of n-3 polyunsaturated fatty acids in children with metabolic inborn errors, while the effects on visual and brain development in premature infants and neonates are well known. However, their function incertain chronic neurological, inflammatory and metabolic disorders is still under study. Standards should be established to help identify the need of docosahexaenoic acid supplementation in conditions requiring a restricted diet resulting in an altered metabolism system, and find scientific evidence on the effects of such supplementation. This study reviews relevant published literature to propose adequate n-3 intake or supplementation doses for different ages and pathologies. The aim of this review is to examine the effects of long chain polyunsaturated fatty acids supplementation in preventing cognitive impairment or in retarding its progress, and to identify nutritional deficiencies, in children with inborn errors of metabolism. Trials were identified from a search of the Cochrane and MEDLINE databases in 2011. These databases include all major completed and ongoing double-blind, placebo-controlled, randomized trials, as well as all studies in which omega-3 supplementation was administered to children with inborn errors, and studies assessing omega-3 fatty acids status in plasma in these pathologies. Although few randomized controlled trials met the inclusion criteria of this review, some evidenced that most of children with inborn errors are deficient in omega-3 fatty acids, and demonstrated that supplementation might improve their neural function, or prevent the progression of neurological impairment. Nontheless, further investigations are needed on this issue.

Towards a whole-body systems [multi-organ] lipidomics in Alzheimer's disease

Preclinical and clinical evidence suggests that docosahexaenoic acid (DHA), an omega-3 fatty acid derived from diet or synthesized in the liver, decreases the risk of developing Alzheimer's disease (AD). DHA levels are reduced in the brain of subjects with AD, but it is still unclear whether human dementias are associated with dysregulations of DHA metabolism. A systems biological view of omega-3 fatty acid metabolism offered unexpected insights on the regulation of DHA homeostasis in AD [1]. Results of multi-organ lipidomic analyses were integrated with clinical and gene-expression data sets to develop testable hypotheses on the functional significance of lipid abnormalities observed and on their possible mechanistic bases. One surprising outcome of this integrative approach was the discovery that the liver of AD patients has a limited capacity to convert shorter chain omega-3 fatty acids into DHA due to a deficit in the peroxisomal d-bifunctional protein. This deficit may contribute to the decrease in brain DHA levels and contribute to cognitive impairment.

Efficient synthesis of the very-long-chain n-3 fatty acids, tetracosahexaenoic acid (C24:6n-3) and tricosahexaenoic acid (C23:6n-3)

Tetracosahexaenoic acid (C(24):6n-3, THA, 3) is an essential biosynthetic precursor in mammals of docosahexaenoic acid (C(22):6n-3, DHA, 1), the end-product of the metabolism of n-3 fatty acids. THA 3 is present in commercially valuable fishes, such as flathead flounder. Tricosahexaenoic acid (C(23):6n-3, TrHA, 2), an odd-numbered-chain fatty acid, has been identified from marine organisms such as the dinoflagellate, Amphidinium carterae. To date, few studies have examined THA 3 and TrHA 2 due to difficulties in detecting and identifying these compounds, so their chemical and biological properties remain poorly characterized. Only one methodology for the chemical synthesis of THA 3 has been presented, and no method for the synthesis of TrHA 2 has been reported. We report here the efficient synthesis of THA 3 in four steps in 56% overall yield, and the synthesis of TrHA 2 in six steps in 48% overall yield. We also present the synthesis of Δ(2)-THA 4, an intermediate of β-oxidation of THA 3 to DHA 1, in three steps in 73% overall yield.

Axonal integrity in the absence of functional peroxisomes from projection neurons and astrocytes

Ablation of functional peroxisomes from all neural cells in Nestin-Pex5 knockout mice caused remarkable neurological abnormalities including motoric and cognitive malfunctioning accompanied by demyelination, axonal degeneration, and gliosis. An oligodendrocyte selective Cnp-Pex5 knockout mouse model shows a similar pathology, but with later onset and slower progression. Until now, the link between these neurological anomalies and the known metabolic alterations, namely the accumulation of very long-chain fatty acids (VLCFA) and reduction of plasmalogens, has not been established. We now focused on the role of peroxisomes in neurons and astrocytes. A neuron-specific peroxisome knockout model, NEX-Pex5, showed neither microscopic nor metabolic abnormalities indicating that the lack of functional peroxisomes within neurons does not cause axonal damage. Axonal integrity and normal behavior was also preserved when peroxisomes were deleted from astrocytes in GFAP-Pex5(-/-) mice. Nevertheless, peroxisomal metabolites were dysregulated in brain including a marked accumulation of VLCFA and a slight reduction in plasmalogens. Interestingly, despite minor targeting of oligodendrocytes in GFAP-Pex5(-/-) mice, these metabolic perturbations were also present in isolated myelin indicating that peroxisomal metabolites are shuttled between different brain cell types. We conclude that absence of peroxisomal metabolism in neurons and astrocytes does not provoke the neurodegenerative phenotype observed after deleting peroxisomes from oligodendrocytes. Lack of peroxisomal metabolism in astrocytes causes increased VLCFA levels in myelin, but this has no major impact on neurological functioning.

Deficient liver biosynthesis of docosahexaenoic acid correlates with cognitive impairment in Alzheimer's disease

Reduced brain levels of docosahexaenoic acid (C22:6n-3), a neurotrophic and neuroprotective fatty acid, may contribute to cognitive decline in Alzheimer's disease. Here, we investigated whether the liver enzyme system that provides docosahexaenoic acid to the brain is dysfunctional in this disease. Docosahexaenoic acid levels were reduced in temporal cortex, mid-frontal cortex and cerebellum of subjects with Alzheimer's disease, compared to control subjects (P = 0.007). Mini Mental State Examination (MMSE) scores positively correlated with docosahexaenoic/α-linolenic ratios in temporal cortex (P = 0.005) and mid-frontal cortex (P = 0.018), but not cerebellum. Similarly, liver docosahexaenoic acid content was lower in Alzheimer's disease patients than control subjects (P = 0.011). Liver docosahexaenoic/α-linolenic ratios correlated positively with MMSE scores (r = 0.78; P<0.0001), and negatively with global deterioration scale grades (P = 0.013). Docosahexaenoic acid precursors, including tetracosahexaenoic acid (C24:6n-3), were elevated in liver of Alzheimer's disease patients (P = 0.041), whereas expression of peroxisomal d-bifunctional protein, which catalyzes the conversion of tetracosahexaenoic acid into docosahexaenoic acid, was reduced (P = 0.048). Other genes involved in docosahexaenoic acid metabolism were not affected. The results indicate that a deficit in d-bifunctional protein activity impairs docosahexaenoic acid biosynthesis in liver of Alzheimer's disease patients, lessening the flux of this neuroprotective fatty acid to the brain.

Docosahexaenoic acid status in females of reproductive age with maple syrup urine disease

Individuals with maple syrup urine disease (MSUD) have impaired metabolism of branched-chain amino acids (BCAA) valine, isoleucine, and leucine. Life-long dietary therapy is recommended to restrict BCAA intake and thus prevent poor neurological outcomes and death. To maintain adequate nutritional status, the majority of protein and nutrients are derived from synthetic BCAA-free medical foods with variable fatty acid content. Given the restrictive diet and the importance of omega-3 fatty acids, particularly docosahexaenoic acid (DHA), in neurological development, this study evaluated the dietary and fatty acid status of females of reproductive age with MSUD attending a metabolic camp. Healthy controls of similar age and sex were selected from existing normal laboratory data. Total lipid fatty acid concentration in plasma and erythrocytes was analyzed using gas chromatography-mass spectroscopy. Participants with MSUD had normal to increased concentrations of plasma and erythrocyte alpha linolenic acid (ALA) but significantly lower concentrations of plasma and erythrocyte docosahexaenoic acid (DHA) as percent of total lipid fatty acids compared with controls (plasma DHA: MSUD 1.03 +/- 0.35, controls 2.87 +/- 1.08; P = 0.001; erythrocyte DHA: MSUD 2.58 +/- 0.58, controls 3.66 +/- 0.80; P = 0.011). Dietary records reflected negligible or no DHA intake over the 3-day period prior to the blood draw (range 0-2 mg). These results suggest females of reproductive age with MSUD have lower blood DHA concentrations than age-matched controls. In addition, the presence of ALA in medical foods and the background diet may not counter the lack of preformed DHA in the diet. The implications of these results warrant further investigation.

A key role for the peroxisomal ABCD2 transporter in fatty acid homeostasis

Peroxisomes are essential organelles exerting key functions in fatty acid metabolism such as the degradation of very long-chain fatty acids (VLCFAs). VLCFAs accumulate in X-adrenoleukodystrophy (X-ALD), a disease caused by deficiency of the Abcd1 peroxisomal transporter. Its closest homologue, Abcd2, exhibits a high degree of functional redundancy on the catabolism of VLCFA, being able to prevent X-ALD-related neurodegeneration in the mouse. In the search for specific roles of Abcd2, we screened fatty acid profiles in organs and primary neurons of mutant knockout mice lacking Abcd2 in basal conditions and under dietary challenges. Our results indicate that ABCD2 plays a role in the degradation of long-chain saturated and omega9-monounsaturated fatty acids and in the synthesis of docosahexanoic acid (DHA). Also, we demonstrated a defective VLCFA beta-oxidation ex vivo in brain slices of Abcd1 and Abcd2 knockouts, using radiolabeled hexacosanoic acid and the precursor of DHA as substrates. As DHA levels are inversely correlated with the incidence of Alzheimer's and several degenerative conditions, we suggest that ABCD2 may act as modulator/modifier gene and therapeutic target in rare and common human disorders.

Effect of dietary docosahexaenoic acid on biosynthesis of docosahexaenoic acid from alpha-linolenic acid in young rats

Docosahexaenoic acid (DHA), a crucial nervous system n-3 PUFA, may be obtained in the diet or synthesized in vivo from dietary alpha-linolenic acid (LNA). We addressed whether DHA synthesis is regulated by the availability of dietary DHA in artificially reared rat pups, during p8 to p28 development. Over 20 days, one group of rat pups was continuously fed deuterium-labeled LNA (d5-LNA) and no other n-3 PUFA (d5-LNA diet), and a second group of rat pups was fed a d5-LNA diet with unlabeled DHA (d5-LNA + DHA diet). The rat pups were then euthanized, and the total amount of deuterium-labeled docosahexaenoic acid (d5-DHA) (synthesized DHA) as well as other n-3 fatty acids present in various body tissues, was quantified. In the d5-LNA + DHA group, the presence of dietary DHA led to a marked decrease (3- to 5-fold) in the total amount of d5-DHA that accumulated in all tissues that we examined, except in adipose. Overall, DHA accretion from d5-DHA was generally diminished by availability of dietary preformed DHA, inasmuch as this was found to be the predominant source of tissue DHA. When preformed DHA was unavailable, d5-DHA and unlabeled DHA were preferentially accreted in some tissues along with a net loss of unlabeled DHA from other organs.

The influence of dietary docosahexaenoic acid and arachidonic acid on central nervous system polyunsaturated fatty acid composition

Numerous studies on perinatal long-chain polyunsaturated fatty acid nutrition have clarified the influence of dietary docosahexaenoic acid (DHA) and arachidonic acid (ARA) on central nervous system PUFA concentrations. In humans, omnivorous primates, and piglets, DHA and ARA plasma and red blood cells concentrations rise with dietary preformed DHA and ARA. Brain and retina DHA are responsive to diet while ARA is not. DHA is at highest concentration in cells and tissues associated with high energy consumption, consistent with high DHA levels in mitochondria and synaptosomes. DHA is a substrate for docosanoids, signaling compounds of intense current interest. The high concentration in tissues with high rates of oxidative metabolism may be explained by a critical role related to oxidative metabolism.

Fatty Acid Transport Protein 4 Is the Principal Very Long Chain Fatty Acyl-CoA Synthetase in Skin Fibroblasts

Fatty acid transport protein 4 (FATP4) is a fatty acyl-CoA synthetase that preferentially activates very long chain fatty acid substrates, such as C24:0, to their CoA derivatives. To gain better insight into the physiological functions of FATP4, we established dermal fibroblast cell lines from FATP4-deficient wrinkle-free mice and wild type (w.t.) mice. FATP4 -/- fibroblasts had no detectable FATP4 protein by Western blot. Compared with w.t. fibroblasts, cells lacking FATP4 had an 83% decrease in C24:0 activation. Peroxisomal degradation of C24:0 was reduced by 58%, and rates of C24:0 incorporation into major phospholipid species (54-64% decrease), triacylglycerol (64% decrease), and cholesterol esters (58% decrease) were significantly diminished. Because these lipid metabolic processes take place in different subcellular organelles, we used immunofluorescence and Western blotting of subcellular fractions to investigate the distribution of FATP4 protein and measured enzyme activity in fractions from w.t. and FATP4 -/- fibroblasts. FATP4 protein and acyl-CoA synthetase activity localized to multiple organelles, including mitochondria, peroxisomes, endoplasmic reticulum, and the mitochondria-associated membrane fraction. We conclude that in murine skin fibroblasts, FATP4 is the major enzyme producing very long chain fatty acid-CoA for lipid metabolic pathways. Although FATP4 deficiency primarily affected very long chain fatty acid metabolism, mutant fibroblasts also showed reduced uptake of a fluorescent long chain fatty acid and reduced levels of long chain polyunsaturated fatty acids. FATP4-deficient cells also contained abnormal neutral lipid droplets. These additional defects indicate that metabolic abnormalities in these cells are not limited to very long chain fatty acids.

Failure of conjugated linoleic acid supplementation to enhance biosynthesis of docosahexaenoic acid from alpha-linolenic acid in healthy human volunteers

A rate-limiting step in docosahexaenoic acid (DHA) formation from alpha-linolenic acid (ALA) involves peroxisomal oxidation of 24:6n-3 to DHA. The aim of the study was to determine whether conjugated linoleic acid (CLA) would enhance conversion of ALA to DHA in humans on an ALA-supplemented diet. The subjects (n=8 per group) received daily supplementation of ALA (11g) and either CLA (3.2g) or placebo for 8 weeks. At baseline, 4 and 8 weeks, blood was collected for plasma fatty acid analysis and a number of physiological measures were examined. The ALA-supplemented diet increased plasma levels of ALA and eicosapentaenoic acid (EPA). The addition of CLA to the ALA diet resulted in increased plasma levels of CLA, as well as ALA and EPA. Plasma level of DHA was not increased with either the ALA alone or ALA plus CLA supplementation. The results demonstrated that CLA was not effective in enhancing DHA levels in plasma in healthy volunteers.

The fatty acid profiles in a drop of blood from a fingertip correlate with physiological, dietary and lifestyle parameters in volunteers

Limited data are available on the fatty acid (FA) composition of circulating lipids and the associations with diet, physiological and pathological conditions, due to the complexity and costs of the analytical process. The aim of our study was to evaluate the FA composition in 108 healthy subjects and to correlate the data with gender, pregnancy, dietary habits, lifestyle, and short-term controlled intake of n-3 FA, using an innovative analytical approach for the collection and processing of blood samples. Ten subjects were also supplemented with n-3 polyunsaturated FA as smoked salmon or capsules for 3 weeks. The resulting blood FA composition was affected by gender, pregnancy, diet and smoking. The data indicate that this new analytical methodology is suitable for assessing associations between circulating FA and various parameters in large population groups, and is applicable to epidemiological studies and in the assessment of the effects of controlled FA supplementation in clinical studies.

Conserved expression of alternative splicing variants of peroxisomal acyl-CoA oxidase 1 in vertebrates and developmental and nutritional regulation in fish

The acyl-coenzyme A oxidase 1 (ACOX1) catalyzes the first, rate-limiting step in peroxisomal beta-oxidation of medium to very long straight-chain fatty acids. Zebrafish (Danio rerio) acox1 was characterized and compared with homologs from other sequenced genomes, revealing a remarkable conservation of structure in the vertebrate lineage. Strictly conserved regions of the deduced proteins included acyl-CoA oxidase and FAD binding domains, as well as a COOH-terminal peroxisomal targeting signal. Whole mount in situ hybridization showed that zebrafish acox1 transcripts were diffusely distributed in early-stage embryonic cells, then discreetly expressed in the brain and widely present in the liver and intestine at later stages. An evolutionarily conserved alternative splicing of the corresponding acox1 primary transcript was identified in teleosts and tetrapods including mammals, giving rise, after exon skipping, to two splice variants, ACOX1-3I and ACOX1-3II. Real-time quantitative RT-PCR on zebrafish adult tissues indicated high levels of both variants in the liver, anterior intestine, and to a lesser extent, in the brain. However, the ACOX1-3II transcript variant was expressed seven times more in zebrafish brain than the ACOX1-3I variant. These data suggest a tissue-specific modulation of ACOX1 activity by exchanging exon 3 duplicated isoforms containing amino acid sequences that are potentially implicated in fatty acyl chain specificity. In addition, a significant pretranslational up-regulation of zebrafish and rainbow trout (Oncorhynchus mykiss) acox1 expression was observed in the anterior intestine after feeding. Taken together, these data indicate that ACOX1 alternative splicing isoforms play a key conserved role in the vertebrate fatty acid metabolism.

Peroxisome biogenesis disorders

Defects in PEX genes impair peroxisome assembly and multiple metabolic pathways confined to this organelle, thus providing the biochemical and molecular bases of the peroxisome biogenesis disorders (PBD). PBD are divided into two types--Zellweger syndrome spectrum (ZSS) and rhizomelic chondrodysplasia punctata (RCDP). Biochemical studies performed in blood and urine are used to screen for the PBD. DNA testing is possible for all of the disorders, but is more challenging for the ZSS since 12 PEX genes are known to be associated with this spectrum of PBD. In contrast, PBD-RCDP is associated with defects in the PEX7 gene alone. Studies of the cellular and molecular defects in PBD patients have contributed significantly to our understanding of the role of each PEX gene in peroxisome assembly.

Peroxisomal multifunctional protein-2 deficiency causes motor deficits and glial lesions in the adult central nervous system

In humans, mutations inactivating multifunctional protein-2 (MFP-2), and thus peroxisomal beta-oxidation, cause neuronal heterotopia and demyelination, which is clinically reflected by hypotonia, seizures, and death within the first year of life. In contrast, our recently generated MFP-2-deficient mice did not show neurodevelopmental abnormalities but exhibited aberrations in bile acid metabolism and one of three of them died early postnatally. In the postweaning period, all survivors developed progressive motor deficits, including abnormal cramping reflexes of the limbs and loss of mobility, with death at 6 months. Motor impairment was not accompanied by lesions of peripheral nerves or muscles. However, in the central nervous system MFP-2-deficient mice overexpressed catalase in glial cells, accumulated lipids in ependymal cells and in the molecular layer of the cerebellum, exhibited severe astrogliosis and reactive microglia predominantly within the gray matter of the brain and the spinal cord, whereas synaptic and myelin markers were not affected. This culminated in degenerative changes of astroglia cells but not in overt neuronal lesions. Neither the motor deficits nor the brain lesions were aggravated by increasing the branched-chain fatty acid concentration through dietary supplementation. These data indicate that MFP-2 deficiency in mice causes a neurological phenotype in adulthood that is manifested primarily by astroglial damage.