Fatty acid bioconversion in harpacticoid copepods in a changing environment : a transcriptomic approach

By 2100, global warming is predicted to significantly reduce the capacity of marine primary producers for long-chain polyunsaturated fatty acid (LC-PUFA) synthesis. Primary consumers such as harpacticoid copepods (Crustacea) might mitigate the resulting adverse effects on the food web by increased LC-PUFA bioconversion. Here, we present a high-quality de novo transcriptome assembly of the copepodPlatychelipus littoralis, exposed to changes in both temperature (+3 degrees C) and dietary LC-PUFA availability. Using this transcriptome, we detected multiple transcripts putatively coding for LC-PUFA-bioconverting front-end fatty acid (FA) desaturases and elongases, and performed phylogenetic analyses to identify their relationship with sequences of other (crustacean) taxa. While temperature affected the absolute FA concentrations in copepods, LC-PUFA levels remained unaltered even when copepods were fed an LC-PUFA-deficient diet. While this suggests plasticity of LC-PUFA bioconversion withinP. littoralis, none of the putative front-end desaturase or elongase transcripts was differentially expressed under the applied treatments. Nevertheless, the transcriptome presented here provides a sound basis for future ecophysiological research on harpacticoid copepods. This article is part of the theme issue 'The next horizons for lipids as 'trophic biomarkers': evidence and significance of consumer modification of dietary fatty acids'

A C35 Carotenoid Biosynthetic Pathway

Upon coexpression with Erwinia geranylgeranyldiphosphate (GGDP) synthase in Escherichia coli, C30 carotenoid synthase CrtM from Staphylococcus aureus produces novel carotenoids with the asymmetrical C35 backbone. The products of condensation of farnesyldiphosphate and GDP, C35 structures comprise 40 to 60% of total carotenoid accumulated. Carotene desaturases and carotene cyclases from C40 or C30 pathways accepted and converted the C35 substrate, thus creating a C35 carotenoid biosynthetic pathway in E. coli. Directed evolution to modulate desaturase step number, together with combinatorial expression of the desaturase variants with lycopene cyclases, allowed us to produce at least 10 compounds not previously described. This result highlights the plastic and expansible nature of carotenoid pathways and illustrates how combinatorial biosynthesis coupled with directed evolution can rapidly access diverse chemical structures

Intake and metabolism of omega-3 and omega-6 polyunsaturated fatty acids: nutritional implications for cardiometabolic diseases

Prospective observational studies support the use of long-chain omega-3 polyunsaturated fatty acids (PUFAs) in the primary prevention of atherosclerotic cardiovascular disease; however, randomised controlled trials, have often reported neutral findings. There is a long history of debate about the potential harmful effects of a high intake of omega-6 PUFAs, although this idea is not supported by prospective observational studies or randomised controlled trials. Health effects of PUFAs might be influenced by Δ-5 and Δ-6 desaturases, the key enzymes in the metabolism of PUFAs. The activity of these enzymes and modulation by variants in encoding genes (FADS1-2-3 gene cluster) are linked to several cardiometabolic traits. This Review will further consider non-genetic determinants of desaturase activity, which have the potential to modify the availability of PUFAs to tissues. Finally, we discuss the consequences of altered desaturase activity in the context of PUFA intake, that is, gene–diet interactions and their clinical and public health implications

FADS Gene Cluster Polymorphisms: Important Modulators of Fatty Acid Levels and Their Impact on Atopic Diseases

Long-chain polyunsaturated fatty acids (LC-PUFAs) play an important role in several physiological processes and their concentration in phospholipids has been associated with several complex diseases, such as atopic disease. The level and composition of LC-PUFAs in the human body is highly dependent on their intake in the diet or on the intake of fatty acid precursors, which are endogenously elongated and desaturated to physiologically active LC-PUFAs. The most important enzymes in this reaction cascade are the Delta(5) and Delta(6) desaturase. Several studies in the last few years have revealed that single nucleotide polymorphisms (SNPs) in the 2 desaturase encoding genes (FADS1 and FADS2) are highly associated with the concentration of omega-6 and omega-3 fatty acids, showing that beside nutrition, genetic factors also play an important role in the regulation of LC-PUFAs. This review focuses on current knowledge of the impact of genetic polymorphisms on LC-PUFA metabolism and on their potential role in the development of atopic diseases. Copyright (c) 2009 S. Karger AG, Base

Regulation of podocyte survival and endoplasmic reticulum stress by fatty acids and its modification by Stearoyl-CoA desaturases and cyclic AMP

Podocyte apoptosis is a hallmark in the development and progression of diabetic nephropathy (DN). Several factors of the diabetic milieu are known to induce podocyte apoptosis. Currently, the role of free fatty acids (FFAs) for podocytopathy and podocyte cell death is unknown, although FFAs are considered to be crucially involved in the development of diabetes mellitus type II. It is well known that FFAs are toxic to several cell types including pancreatic § cells and they may contribute to the development of insulin resistance. The aims of this study were to elucidate the role of the saturated palmitic acid and the monounsaturated palmitoleic and oleic acid on podocyte cell death and endoplasmic reticulum (ER)-stress, to investigate more specifically the impact of ER-stress on podocyte survival as well as to elaborate strategies to protect podocytes from lipotoxicity. The present study uncovered that palmitic acid induces podocyte apoptosis and necrosis and leads to ER-stress as reflected by induction of the unfolded protein response (UPR), i.e. upregulation of the ER chaperone immunoglobulin heavy chain binding protein (BiP), X-box protein 1 (XBP-1) mRNA splicing, and a strong upregulation of the proapoptotic transcription factor C/EBP homologous protein (CHOP). Gene silencing experiments of CHOP support a crucial involvment of CHOP and ER-stress in mediating the proapoptotic effect of palmitic acid in podocytes. Contrariwise, monounsaturated FFAs (MUFAs) such as palmitoleic and oleic acid prevent palmitic acid-induced podocyte death and attenuate ER-stress. This study further revealed that the liver X receptor (LXR) agonist TO901317 (TO) ameliorates survival of palmitic acid-treated podocytes. Mechanistically, this beneficial effect can be explained mainly by the induction of stearoyl-CoA desaturase (SCD-) 1 and 2 as shown by gene silencing experiments and further supported from overexpression studies of SCD-1. Moreover, palmitic acid tracing experiments revealed a higher incorporation of palmitic acid into the triglyceride (TG) fraction in podocytes treated with TO or oleic acid, which is at least compatible with a benefit of increased fatty acid storage, by TO, i.e. SCDs, and MUFAs, respectively. In addition, this study provides some preliminary data that adenylate cyclases (AC) may be an interesting target to protect podocytes from ER-stress in general and in particular from palmitic acid-induced podocytopathy and cell death. Experiments with forskolin, a specific AC agonist, and cyclic AMP (cAMP) analogons protect from palmitic acid-induced podocyte lipotoxicity. The effect cannot be explained by an involvment of PKA-CREB signaling as overexpression of a dominant negative CREB mutant could not abrogate the protective effect of forskolin. Furthermore, the beneficial impact of forskolin is not influencing the intrinisic (mitochondrial) apoptotic pathway. However, in addition to the protection from palmitic acid-induced cell death, forskolin is suppressing podocyte death caused by other independent ER-stressors such as tunicamycin and thapsigargin. These findings suggest a direct role of forskolin and increased cAMP levels for a protection from ER-stress in podocytes. In summary, this study unveiled antagonistic effects of palmitic acid versus monounsaturated FFAs for podocyte survival, ER-stress and the UPR. They support an important role of CHOP in the regulation of podocyte death by FFAs. Similarly to exogenous MUFAs, induction of SCDs partially protects podocytes from palmitic acid-induced ER-stress and podocyte death. The protective effect of MUFAs may be related to increased incorporation of palmitic acid into TGs. Additional, preliminary data indicate that AC agonists such as forskolin may be interesting compounds to protect podocytes from ER-stress and from the toxic effects of FFAs. The results of this study offer a rationale for interventional studies aimed at testing whether dietary shifting of the FFA balance toward MUFAs, or tissue- (podocyte-) specific stimulation or overexpression of SCDs can delay the progression of DN. Similarly, the results of this study should encourage more studies to evaluate the therapeutic potential of AC agonists or phosphodiesterase inhibitors for the prevention and treatment of DN

The hypoxic transcription factor KlMga2 mediates the response to oxidative stress and influences longevity in the yeast Kluyveromyces lactis

Hypoxia is defined as the decline of oxygen availability, depending on environmental supply and cellular consumption rate. The decrease in O2 results in reduction of available energy in facultative aerobes. The response and/or adaptation to hypoxia and other changing environmental conditions can influence the properties and functions of membranes by modifying lipid composition. In the yeast Kluyveromyces lactis, the KlMga2 gene is a hypoxic regulatory factor for lipid biosynthesis-fatty acids and sterols-and is also involved in glucose signaling, glucose catabolism and is generally important for cellular fitness. In this work we show that, in addition to the above defects, the absence of the KlMGA2 gene caused increased resistance to oxidative stress and extended lifespan of the yeast, associated with increased expression levels of catalase and SOD genes. We propose that KlMga2 might also act as a mediator of the oxidative stress response/adaptation, thus revealing connections among hypoxia, glucose signaling, fatty acid biosynthesis and ROS metabolism in K. lactis

Comparative Analysis of Fatty Acid Desaturases in Cyanobacterial Genomes

Fatty acid desaturases are enzymes that introduce double bonds into the hydrocarbon chains of fatty acids. The fatty acid desaturases from 37 cyanobacterial genomes were identified and classified based upon their conserved histidine-rich motifs and phylogenetic analysis, which help to determine the amounts and distributions of desaturases in cyanobacterial species. The filamentous or N2-fixing cyanobacteria usually possess more types of fatty acid desaturases than that of unicellular species. The pathway of acyl-lipid desaturation for unicellular marine cyanobacteria Synechococcus and Prochlorococcus differs from that of other cyanobacteria, indicating different phylogenetic histories of the two genera from other cyanobacteria isolated from freshwater, soil, or symbiont. Strain Gloeobacter violaceus PCC 7421 was isolated from calcareous rock and lacks thylakoid membranes. The types and amounts of desaturases of this strain are distinct to those of other cyanobacteria, reflecting the earliest divergence of it from the cyanobacterial line. Three thermophilic unicellular strains, Thermosynechococcus elongatus BP-1 and two Synechococcus Yellowstone species, lack highly unsaturated fatty acids in lipids and contain only one Δ9 desaturase in contrast with mesophilic strains, which is probably due to their thermic habitats. Thus, the amounts and types of fatty acid desaturases are various among different cyanobacterial species, which may result from the adaption to environments in evolution

Statin-induced myopathic changes in primary human muscle cells and reversal by a prostaglandin F2 alpha analogue

Statin-related muscle side effects are a constant healthcare problem since patient compliance is dependent on side effects. Statins reduce plasma cholesterol levels and can prevent secondary cardiovascular diseases. Although statin-induced muscle damage has been studied, preventive or curative therapies are yet to be reported. We exposed primary human muscle cell populations (n = 22) to a lipophilic (simvastatin) and a hydrophilic (rosuvastatin) statin and analyzed their expressome. Data and pathway analyses included GOrilla, Reactome and DAVID. We measured mevalonate intracellularly and analyzed eicosanoid profiles secreted by human muscle cells. Functional assays included proliferation and differentiation quantification. More than 1800 transcripts and 900 proteins were differentially expressed after exposure to statins. Simvastatin had a stronger effect on the expressome than rosuvastatin, but both statins influenced cholesterol biosynthesis, fatty acid metabolism, eicosanoid synthesis, proliferation, and differentiation of human muscle cells. Cultured human muscle cells secreted ω-3 and ω-6 derived eicosanoids and prostaglandins. The ω-6 derived metabolites were found at higher levels secreted from simvastatin-treated primary human muscle cells. Eicosanoids rescued muscle cell differentiation. Our data suggest a new aspect on the role of skeletal muscle in cholesterol metabolism. For clinical practice, the addition of omega-n fatty acids might be suitable to prevent or treat statin-myopathy