Associations of genetically predicted fatty acid levels across the phenome: A mendelian randomisation study.

BACKGROUND: Fatty acids are important dietary factors that have been extensively studied for their implication in health and disease. Evidence from epidemiological studies and randomised controlled trials on their role in cardiovascular, inflammatory, and other diseases remains inconsistent. The objective of this study was to assess whether genetically predicted fatty acid concentrations affect the risk of disease across a wide variety of clinical health outcomes. METHODS AND FINDINGS: The UK Biobank (UKB) is a large study involving over 500,000 participants aged 40 to 69 years at recruitment from 2006 to 2010. We used summary-level data for 117,143 UKB samples (base dataset), to extract genetic associations of fatty acids, and individual-level data for 322,232 UKB participants (target dataset) to conduct our discovery analysis. We studied potentially causal relationships of circulating fatty acids with 845 clinical diagnoses, using mendelian randomisation (MR) approach, within a phenome-wide association study (PheWAS) framework. Regression models in PheWAS were adjusted for sex, age, and the first 10 genetic principal components. External summary statistics were used for replication. When several fatty acids were associated with a health outcome, multivariable MR and MR-Bayesian method averaging (MR-BMA) was applied to disentangle their causal role. Genetic predisposition to higher docosahexaenoic acid (DHA) was associated with cholelithiasis and cholecystitis (odds ratio per mmol/L: 0.76, 95% confidence interval: 0.66 to 0.87). This was supported in replication analysis (FinnGen study) and by the genetically predicted omega-3 fatty acids analyses. Genetically predicted linoleic acid (LA), omega-6, polyunsaturated fatty acids (PUFAs), and total fatty acids (total FAs) showed positive associations with cardiovascular outcomes with support from replication analysis. Finally, higher genetically predicted levels of DHA (0.83, 0.73 to 0.95) and omega-3 (0.83, 0.75 to 0.92) were found to have a protective effect on obesity, which was supported using body mass index (BMI) in the GIANT consortium as replication analysis. Multivariable MR analysis suggested a direct detrimental effect of LA (1.64, 1.07 to 2.50) and omega-6 fatty acids (1.81, 1.06 to 3.09) on coronary heart disease (CHD). MR-BMA prioritised LA and omega-6 fatty acids as the top risk factors for CHD. Although we present a range of sensitivity analyses to the address MR assumptions, horizontal pleiotropy may still bias the reported associations and further evaluation in clinical trials is needed. CONCLUSIONS: Our study suggests potentially protective effects of circulating DHA and omega-3 concentrations on cholelithiasis and cholecystitis and on obesity, highlighting the need to further assess them as prevention treatments in clinical trials. Moreover, our findings do not support the supplementation of unsaturated fatty acids for cardiovascular disease prevention.

Proteomic and lipidomic profiling of demyelinating lesions identifies fatty acids as modulators in lesion recovery.

After demyelinating injury of the central nervous system, resolution of the mounting acute inflammation is crucial for the initiation of a regenerative response. Here, we aim to identify fatty acids and lipid mediators that govern the balance of inflammatory reactions within demyelinating lesions. Using lipidomics, we identify bioactive lipids in the resolution phase of inflammation with markedly elevated levels of n-3 polyunsaturated fatty acids. Using fat-1 transgenic mice, which convert n-6 fatty acids to n-3 fatty acids, we find that reduction of the n-6/n-3 ratio decreases the phagocytic infiltrate. In addition, we observe accelerated decline of microglia/macrophages and enhanced generation of oligodendrocytes in aged mice when n-3 fatty acids are shuttled to the brain. Thus, n-3 fatty acids enhance lesion recovery and may, therefore, provide the basis for pro-regenerative medicines of demyelinating diseases in the central nervous system.

Causal Effects of N-6 Polyunsaturated Fatty Acids on Age-related Macular Degeneration: A Mendelian Randomization Study.

CONTEXT: Although the role of n-6 polyunsaturated fatty acids (PUFAs) in age-related macular degeneration (AMD) has been studied in previous observational studies, the precise manner in which 1 or more n-6 PUFAs account for this relationship remains unclear. OBJECTIVE: Using genetic instruments for n-6 PUFAs traits implemented through mendelian randomization (MR), we aimed to study possible causal associations between n-6 PUFAs and AMD. METHODS: The 2-sample MR method was used to obtain unconfounded causal estimates. We selected genetic variants strongly associated (P < 5 × 10-8) with circulating linoleic acid (LA) and arachidonic acid (AA) from a study involving 8 631 individuals and applied to an AMD case-control study (33 526 participants and 16 144 cases). The weighted median and MR Egger methods were used for the sensitivity analysis. RESULTS: Our MR analysis suggested that circulating LA was a causal protective factor for AMD, with an odds ratio (OR) estimate of 0.967 (95% CI 0.945 to 0.990; P = .005) per percentage in total fatty acid increase in LA. In contrast, higher genetically predicted circulating AA causally increased the AMD risk (OR = 1.034; 95% CI 1.012 to 1.056; P = .002). Sensitivity analysis provided no indication of unknown pleiotropy. The findings from different single-nucleotide polymorphism selections and analytic methods were consistent, suggesting the robustness of the causal associations. CONCLUSION: Our study provided genetic evidence that circulating LA accounted for protective effects of n-6 PUFAs against the risk of AMD, whereas AA was responsible for deleterious effects on higher AMD risk.

Could Lipoxins Represent a New Standard in Ischemic Stroke Treatment?

INTRODUCTION: Cardiovascular diseases including stroke are one of the most common causes of death. Their main cause is atherosclerosis and chronic inflammation in the body. An ischemic stroke may occur as a result of the rupture of unstable atherosclerotic plaque. Cardiovascular diseases are associated with uncontrolled inflammation. The inflammatory reaction produces chemical mediators that stimulate the resolution of inflammation. One of these mediators is lipoxins-pro-resolving mediators that are derived from the omega-6 fatty acid family, promoting inflammation relief and supporting tissue regeneration. AIM: The aim of the study was to review the available literature on the therapeutic potential of lipoxins in the context of ischemic stroke. MATERIAL AND METHODS: Articles published up to 31 January 2021 were included in the review. The literature was searched on the basis of PubMed and Embase in terms of the entries: 'stroke and lipoxin' and 'stroke and atherosclerosis', resulting in over 110 articles in total. Studies that were not in full-text English, letters to the editor, and conference abstracts were excluded. RESULTS: In animal studies, the injection/administration of lipoxin A4 improved the integrity of the blood-brain barrier (BBB), decreased the volume of damage caused by ischemic stroke, and decreased brain edema. In addition, lipoxin A4 inhibited the infiltration of neutrophils and the production of cytokines and pro-inflammatory chemokines, such as interleukin (Il-1ß, Il-6, Il-8) and tumor necrosis factor-α (TNF-α). The beneficial effects were also observed after introducing the administration of lipoxin A4 analog-BML-111. BML-111 significantly reduces the size of a stroke and protects the cerebral cortex, possibly by reducing the permeability of the blood-brain barrier. Moreover, more potent than lipoxin A4, it has an anti-inflammatory effect by inhibiting the production of pro-inflammatory cytokines and increasing the amount of anti-inflammatory cytokines. CONCLUSIONS: Lipoxins and their analogues may find application in reducing damage caused by stroke and improving the prognosis of patients after ischemic stroke.

Effect of plant-based diets with varying ratios of ω6 to ω3 fatty acids on growth performance, tissue composition, fatty acid biosynthesis and lipid-related gene expression in Atlantic salmon (Salmo salar).

Little is known about how variation in omega-6 to omega-3 (ω6:ω3) fatty acid (FA) ratios affects lipid metabolism and eicosanoid synthesis in salmon, and the potential underlying molecular mechanisms. The current study examined the impact of five plant-based diets (12-week exposure) with varying ω6:ω3 (0.3-2.7) on the growth, tissue lipid composition (muscle and liver), and hepatic transcript expression of lipid metabolism and eicosanoid synthesis-related genes in Atlantic salmon. Growth performance and organ indices were not affected by dietary ω6:ω3. The liver and muscle FA composition was highly reflective of the diet (ω6:ω3 of 0.2-0.8 and 0.3-1.9, respectively) and suggested elongation and desaturation of the ω3 and ω6 precursors 18:3ω3 and 18:2ω6. Furthermore, proportions of ω6 and ω3 PUFA in both tissues showed significant positive correlations with dietary inclusion (% of diet) of soy and linseed oils, respectively. Compound-specific stable isotope analysis (CSIA) further demonstrated that liver long-chain polyunsaturated fatty acid (LC-PUFA) synthesis (specifically 20:5ω3 and 20:4ω6) was largely driven by dietary 18:3ω3 and 18:2ω6, even when 20:5ω3 and 22:6ω3 were supplied at levels above minimum requirements. In addition, significant positive and negative correlations were identified between the transcript expression of LC-PUFA synthesis-related genes and liver ω6 and ω3 LC-PUFA, respectively, further supporting FA biosynthesis. Liver ω3 LC-PUFA also correlated negatively with the eicosanoid synthesis-related transcripts pgds and cox1. This is the first study to use CSIA, hepatic transcriptome, and tissue lipid composition analyses concurrently to demonstrate the impact of plant-based diets with varying ω6:ω3 on farmed Atlantic salmon.

Serum Omega-6 Fatty Acids and Immunology-Related Gene Expression in Peripheral Blood Mononuclear Cells: A Cross-Sectional Analysis in Healthy Children.

SCOPE: Some studies suggest that a high dietary intake of omega-6 fatty acids is pro-inflammatory. However, whether omega-6 fatty acids actually cause pathogenic inflammation in humans is debated. Therefore, the associations between expression of immunology-related genes in peripheral blood mononuclear cells (PBMCs) and serum total omega-6 PUFA status are investigated. METHODS AND RESULTS: Serum fatty acid profile and expression of 460 immunology-related genes in PBMCs from 58 healthy children (6-13 years) is measured, and examined the expression differences between children with high or low total omega-6 PUFA status (upper vs lower tertile). Taken together, both univariate analyses and integrated omics analyses support that while high omega-6 PUFA level associated with higher expressing of genes related to innate immune responses, it also associated with lower expression of several genes related to adaptive immune responses. CONCLUSION: Omega-6 PUFA status associated both positively and negatively with expression of specific immunology-related genes in PBMCs in healthy children. The results may suggest a nuanced role for omega-6 fatty acids in the interphase of lipids and inflammation, and warrants further examination in gene-environment studies and randomized controlled trials.

Modulation of apoptosis-related microRNAs following myocardial infarction in fat-1 transgenic mice vs wild-type mice.

BACKGROUND: microRNAs (miRNAs) post-transcriptionally regulate cardiac repair following myocardial infarction (MI). Omega-3 polyunsaturated fatty acid (ω-3 PUFAs) may support cardiac healing after MI, but the mechanism is unclear. METHODS: The fat-1 transgenic mouse expresses a ω-3 fatty acid desaturase which converts ω-6 PUFAs to ω-3 PUFAs in vivo. MI was induced in fat-1 transgenic (n = 30) and wild-type (WT) mice (n = 30) using permanent ligation. Other transgenic and WT mice underwent sham procedure (n = 30 and n = 30, respectively). One week after occlusion, cardiac function was measured by echocardiography and the infarct size was assessed using histology and miRNA microarray profiling. Expression of selected miRNA was confirmed using quantitative real-time PCR. RESULTS: One week following MI, the fat-1 transgenic myocardium had better cardiac function, a smaller fibrotic area, and fewer apoptotic cardiomyocytes than WT myocardium. Post-MI profiling showed 33 miRNAs that were significantly up-regulated, and 35 were down-regulated, in fat-1 group compared to the WT group (n = 3 and n = 2 mice, respectively). Among selected apoptosis-associated miRNAs, 9 miRNAs were up-regulated (miR-101a-3p, miR-128-3p,miR-133a-5p,miR-149-5p,miR-192-5p,miR-1a-3p,miR-208a-3p,miR-29c-5p,miR-30c-2-3p), and 3 were down-regulated (miR-210-3p,miR-21a-3p,miR-214-3p) in fat-1 transgenic mice compared with WT mice. Kyoto encyclopaedia of genes and genomes (KEGG) pathway analysis indicated likely roles for these miRNAs in MI. Furthermore, Bcl-2 expression was increased, and caspase-3 decreased, in infarcted fat-1 transgenic mouse hearts compared to WT hearts. CONCLUSIONS: ω-3 PUFAs may have a protective effect on cardiomyocytes following MI through their modulation of apoptosis-related miRNAs and target genes.

An overview of the biologic effects of omega-6 oxylipins in humans.

Oxylipins are lipid mediators produced from polyunsaturated fatty acid (PUFA) metabolism, and are thought to be a molecular explanation for the diverse biological effects of PUFAs. Like PUFAs, oxylipins are distinguished by their omega-6 (n6) or omega-3 (n3) chemistry. We review the use of n6 oxylipins as biomarkers of disease and their use in diagnosis and risk assessment. We show cases where oxylipins derived from linoleate (LA) or arachidonate (AA) produced by the activities of lipoxygenase, cyclooxygenase, epoxygenase, ω/ω-1 hydroxylase, and autooxidation are useful as biomarkers or risk markers. HODEs, KODEs, EpOMEs, DiHOMEs, and other metabolites of LA as well as prostanoids, HETEs, KETEs, EpETrEs, and DiHETrEs, and other metabolites of AA were useful for understanding the different signaling environments in conditions from traumatic brain injury, to major coronary events, dyslipidemia, sepsis, and more. We next evaluate interventions that alter the concentrations of n6 oxylipins in plasma. We note the utility and response of each plasma fraction, and the generally increasing utility from the non-esterified, to the esterified, to the lipoprotein fractions. Finally, we review the effects which are specifically related to n6 oxylipins and most likely to be beneficial. Both n6 and n3 oxylipins work together in an exceedingly complex matrix to produce physiological effects. This overview should provide future investigators with important perspectives for the emerging utility of n6 oxylipins as products of n6 PUFAs in human health.

Omega 3 polyunsaturated fatty acids inhibit cell proliferation by regulating cell cycle in fad3b transgenic mouse embryonic stem cells.

BACKGROUND: The consumption of omega 3 polyunsaturated fatty acids (PUFAs) is important for human health and is closely associated with cell proliferation and differentiation. This study aimed to investigate the influence of omega 3 PUFAs on embryonic stem cell (ESC) proliferation and explore potential mechanisms that mediate these effects. METHODS: In this study, we isolated ESCs from fad3b-expressing transgenic mice. We detected the fatty-acid composition of ESCs using gas chromatography-mass spectroscopy, analyzed cell-cycle phases using flow cytometry, and detected gene expression using real-time polymerase chain reaction (PCR) and western blots. RESULTS: The amount of omega 3 PUFAs significantly increased in fad3b versus control ESCs. However, the growth of fad3b ESCs was slower than that of control cells, and most fad3b ESCs were in a prolonged G0/G1 phase after being passaged for 18 h. Therefore, we hypothesized that fad3b expression inhibited the cell cycle in ESCs by increasing the expression of P21, which then decreased the expression of cyclin-dependent kinase 4 (Cdk4). We found that pretreatment of fad3b ESCs with PD0325901, a P21 inhibitor, clearly attenuated the inhibitory effects of P21 on Cdk4, and resumed the cell cycle. CONCLUSIONS: Expression of the fad3b gene in ESCs increased the omega 3 PUFA content, which inhibited cell proliferation by prolonging the G1 phase but did not arrest the G0-to-G1 or G1-to-S transitions. The prolonged G1 phase in fad3b ESCs was probably induced by downregulation of Cdk4 expression via p21 upregulation. These results suggest that accumulation of omega 3 PUFAs in vivo may beneficially affect ESC differentiation and that fad3b ESCs may be a useful tool for investigating related mechanisms.

A novel FADS2 isoform identified in human milk fat globule suppresses FADS2 mediated Δ6-desaturation of omega-3 fatty acids.

INTRODUCTION: The only known non-pharmacological means to alter long chain polyunsaturated fatty acid (LCPUFA) abundance in mammalian tissue is by altering substrate fatty acid ratios. Alternative mRNA splicing is increasingly recognized as a modulator of protein structure and function. Here we report identification of a novel alternative transcript (AT) of fatty acid desaturase 2 (FADS2) that inhibits production of omega-3 but not omega-6 LCPUFA, discovered during study of ATs in human milk fat globules (MFG). METHODS: Human breastmilk collected from a single donor was used to isolate MFG. An mRNA-sequencing library was constructed from the total RNA isolated from the MFG. The constructed library was sequenced using an Illumina HiSeq instrument operating in high output mode. Expression levels of evolutionary conserved FADSAT were measured using cDNA from MFG by semi-quantitative RT-PCR assay. RESULTS: RNA sequencing revealed >15,000 transcripts, including moderate expression of the FADS2 classical transcript (CS). A novel FADS2 alternative transcript (FADS2AT2) with 386 amino acids was discovered. When FADS2AT2 was transiently transfected into MCF7 cells stably expressing FADS2, delta-6 desaturation (D6D) of alpha-linolenic acid 18:3n-3 → 18:4n-3 was suppressed as were downstream products 20:4n-3 and 20:5n-3. In contrast, no significant effect on D6D of linoleic acid 18:2n-6 → 18:3n-6 or downstream products was observed. FADS2, FADS2AT1 and 5 out of 8 known FADS3AT were expressed in MFG. FADS1, FADS3AT3, and FADS3AT5 are undetectable. CONCLUSION: The novel, noncatalytic FADS2AT2 regulates FADS2CS-mediated Δ6-desaturation of omega-3 but not omega-6 PUFA biosynthesis. This spliced isoform mediated interaction is the first molecular mechanism by which desaturation of one PUFA family but not the other is modulated.

Associations among FADS1 rs174547, eicosapentaenoic acid/arachidonic acid ratio, and arterial stiffness in overweight subjects.

We aimed to evaluate the longitudinal interaction effects between the minor allele of FADS1 rs174547 and overweight on n-3 and n-6 long-chain polyunsaturated fatty acid (PUFA) levels and pulse wave velocity (PWV). Plasma PUFA levels were measured via GC-MS, and arterial stiffness was determined as brachial-ankle PWV (ba-PWV) at baseline and after a mean follow-up of 3 years. The FADS1 rs174547 T > C genotype was analyzed. At 3-years of follow-up, after adjustment for age, sex, smoking and drinking, there were interaction effects between the FADS1 rs174547 T > C genotype and baseline BMI on the changes (from baseline) in plasma arachidonic acid (AA) levels, in the eicosapentaenoic acid (EPA)/AA ratio, and in ba-PWV (p for interaction = 0.036, 0.022, and 0.001, respectively). There were smaller increases in AA levels from baseline among normal-weight C allele carriers (n = 112) and overweight TT subjects (n = 47) than among normal-weight TT subjects (n = 91). Overweight C allele carriers (n = 37) showed greater reductions in the plasma EPA/AA ratio and greater increases in ba-PWV than the 3 other populations studied. The minor allele of the FADS1 rs174547 polymorphism is associated with age-related decreases in the EPA/AA ratio and increases in ba-PWV among overweight subjects.

Acyl chain asymmetry and polyunsaturation of brain phospholipids facilitate membrane vesiculation without leakage.

Phospholipid membranes form cellular barriers but need to be flexible enough to divide by fission. Phospholipids generally contain a saturated fatty acid (FA) at position sn1 whereas the sn2-FA is saturated, monounsaturated or polyunsaturated. Our understanding of the impact of phospholipid unsaturation on membrane flexibility and fission is fragmentary. Here, we provide a comprehensive view of the effects of the FA profile of phospholipids on membrane vesiculation by dynamin and endophilin. Coupled to simulations, this analysis indicates that: (i) phospholipids with two polyunsaturated FAs make membranes prone to vesiculation but highly permeable; (ii) asymmetric sn1-saturated-sn2-polyunsaturated phospholipids provide a tradeoff between efficient membrane vesiculation and low membrane permeability; (iii) When incorporated into phospholipids, docosahexaenoic acid (DHA; omega-3) makes membranes more deformable than arachidonic acid (omega-6). These results suggest an explanation for the abundance of sn1-saturated-sn2-DHA phospholipids in synaptic membranes and for the importance of the omega-6/omega-3 ratio on neuronal functions.

Lipid droplets induced by secreted phospholipase A2 and unsaturated fatty acids protect breast cancer cells from nutrient and lipotoxic stress.

Cancer cells driven by the Ras oncogene scavenge unsaturated fatty acids (FAs) from their environment to counter nutrient stress. The human group X secreted phospholipase A2 (hGX sPLA2) releases FAs from membrane phospholipids, stimulates lipid droplet (LD) biogenesis in Ras-driven triple-negative breast cancer (TNBC) cells and enables their survival during starvation. Here we examined the role of LDs, induced by hGX sPLA2 and unsaturated FAs, in protection of TNBC cells against nutrient stress. We found that hGX sPLA2 releases a mixture of unsaturated FAs, including ω-3 and ω-6 polyunsaturated FAs (PUFAs), from TNBC cells. Starvation-induced breakdown of LDs induced by low micromolar concentrations of unsaturated FAs, including PUFAs, was associated with protection from cell death. Interestingly, adipose triglyceride lipase (ATGL) contributed to LD breakdown during starvation, but it was not required for the pro-survival effects of hGX sPLA2 and unsaturated FAs. High micromolar concentrations of PUFAs, but not OA, induced oxidative stress-dependent cell death in TNBC cells. Inhibition of triacylglycerol (TAG) synthesis suppressed LD biogenesis and potentiated PUFA-induced cell damage. On the contrary, stimulation of LD biogenesis by hGX sPLA2 and suppression of LD breakdown by ATGL depletion reduced PUFA-induced oxidative stress and cell death. Finally, lipidomic analyses revealed that sequestration of PUFAs in LDs by sPLA2-induced TAG remodelling and retention of PUFAs in LDs by inhibition of ATGL-mediated TAG lipolysis protect from PUFA lipotoxicity. LDs are thus antioxidant and pro-survival organelles that guard TNBC cells against nutrient and lipotoxic stress and emerge as attractive targets for novel therapeutic interventions.

In vivo activation of leukocyte GPR120/FFAR4 by PUFAs has minimal impact on atherosclerosis in LDL receptor knockout mice.

G protein-coupled receptor (GPR)120/FFA receptor (FFAR)4 (GPR120/FFAR4) activation by n-3 PUFAs attenuates inflammation, but its impact on atherosclerosis is unknown. We determined whether in vivo activation of leukocyte GPR120/FFAR4 by n-3 versus n-6 PUFAs is atheroprotective. Leukocyte GPR120/FFAR4 WT or KO mice in the LDL receptor KO background were generated by bone marrow transplantation. Mice were fed one of the four atherogenic diets containing 0.2% cholesterol and 10% calories as palm oil (PO) + 10% calories as: 1) PO, 2) fish oil (FO; 20:5 n-3 and 22:6 n-3 enriched), 3) echium oil (EO; 18:4 n-3 enriched), or 4) borage oil (BO; 18:3 n-6 enriched) for 16 weeks. Compared with PO, mice fed BO, EO, and FO had significantly reduced plasma cholesterol, TG, VLDL cholesterol, hepatic neutral lipid, and atherosclerosis that were equivalent for WT and KO mice. In BO-, EO-, and FO-fed mice, but not PO-fed mice, lack of leukocyte GPR120/FFAR4 resulted in neutrophilia, pro-inflammatory Ly6Chi monocytosis, increased aortic root monocyte recruitment, and increased hepatic inflammatory gene expression. In conclusion, leukocyte GPR120 expression has minimal effects on dietary PUFA-induced plasma lipid/lipoprotein reduction and atheroprotection, and there is no distinction between n-3 versus n-6 PUFAs in activating anti-inflammatory effects of leukocyte GPR120/FFAR4 in vivo.

Perilipin-2 Deletion Impairs Hepatic Lipid Accumulation by Interfering with Sterol Regulatory Element-binding Protein (SREBP) Activation and Altering the Hepatic Lipidome.

Perilipin-2 (PLIN2) is a constitutively associated cytoplasmic lipid droplet coat protein that has been implicated in fatty liver formation in non-alcoholic fatty liver disease. Mice with or without whole-body deletion of perilipin-2 (Plin2-null) were fed either Western or control diets for 30 weeks. Perilipin-2 deletion prevents obesity and insulin resistance in Western diet-fed mice and dramatically reduces hepatic triglyceride and cholesterol levels in mice fed Western or control diets. Gene and protein expression studies reveal that PLIN2 deletion suppressed SREBP-1 and SREBP-2 target genes involved in de novo lipogenesis and cholesterol biosynthetic pathways in livers of mice on either diet. GC-MS lipidomics demonstrate that this reduction correlated with profound alterations in the hepatic lipidome with significant reductions in both desaturation and elongation of hepatic neutral lipid species. To examine the possibility that lipidomic actions of PLIN2 deletion contribute to suppression of SREBP activation, we isolated endoplasmic reticulum membrane fractions from long-term Western diet-fed wild type (WT) and Plin2-null mice. Lipidomic analyses reveal that endoplasmic reticulum membranes from Plin2-null mice are markedly enriched in ω-3 and ω-6 long-chain polyunsaturated fatty acids, which others have shown inhibit SREBP activation and de novo lipogenesis. Our results identify PLIN2 as a determinant of global changes in the hepatic lipidome and suggest the hypothesis that these actions contribute to SREBP-regulated de novo lipogenesis involved in non-alcoholic fatty liver disease.

Altered hepatic gene expression in nonalcoholic fatty liver disease is associated with lower hepatic n-3 and n-6 polyunsaturated fatty acids.

UNLABELLED: In nonalcoholic fatty liver disease, hepatic gene expression and fatty acid (FA) composition have been reported independently, but a comprehensive gene expression profiling in relation to FA composition is lacking. The aim was to assess this relationship. In a cross-sectional study, hepatic gene expression (Illumina Microarray) was first compared among 20 patients with simple steatosis (SS), 19 with nonalcoholic steatohepatitis (NASH), and 24 healthy controls. The FA composition in hepatic total lipids was compared between SS and NASH, and associations between gene expression and FAs were examined. Gene expression differed mainly between healthy controls and patients (SS and NASH), including genes related to unsaturated FA metabolism. Twenty-two genes were differentially expressed between NASH and SS; most of them correlated with disease severity and related more to cancer progression than to lipid metabolism. Biologically active long-chain polyunsaturated FAs (PUFAs; eicosapentaenoic acid + docosahexaenoic acid, arachidonic acid) in hepatic total lipids were lower in NASH than in SS. This may be related to overexpression of FADS1, FADS2, and PNPLA3. The degree and direction of correlations between PUFAs and gene expression were different among SS and NASH, which may suggest that low PUFA content in NASH modulates gene expression in a different way compared with SS or, alternatively, that gene expression influences PUFA content differently depending on disease severity (SS versus NASH). CONCLUSION: Well-defined subjects with either healthy liver, SS, or NASH showed distinct hepatic gene expression profiles including genes involved in unsaturated FA metabolism. In patients with NASH, hepatic PUFAs were lower and associations with gene expression were different compared to SS.

Abnormal n-6 fatty acid metabolism in cystic fibrosis is caused by activation of AMP-activated protein kinase.

Cystic fibrosis (CF) patients and model systems exhibit consistent abnormalities in PUFA metabolism, including increased metabolism of linoleate to arachidonate. Recent studies have connected these abnormalities to increased expression and activity of the Δ6- and Δ5-desaturase enzymes. However, the mechanism connecting these changes to the CF transmembrane conductance regulator (CFTR) mutations responsible for CF is unknown. This study tests the hypothesis that increased activity of AMP-activated protein kinase (AMPK), previously described in CF bronchial epithelial cells, causes these changes in fatty acid metabolism by driving desaturase expression. Using CF bronchial epithelial cell culture models, we confirm elevated activity of AMPK in CF cells and show that it is due to increased phosphorylation of AMPK by Ca(2+)/calmodulin-dependent protein kinase kinase ß (CaMKKß). We also show that inhibition of AMPK or CaMKKß reduces desaturase expression and reverses the metabolic alterations seen in CF cells. These results signify a novel AMPK-dependent mechanism linking the genetic defect in CF to alterations in PUFA metabolism.

Anti-senescence effect of FatI gene in goat somatic cells.

The fatty acid dehydrogenase I (FatI) is able to express in mammalian cells and convert n-6 polyunsaturated fatty acids (PUFAs) to n-3 PUFAs. n-3 PUFA is an important component of the cell membrane and plays an important role in the prevention and control of a variety of human diseases. However, n-3 PUFAs cannot be endogenously synthesized by mammals because they lack the dehydrogenase that converts n-6 to n-3 PUFA. For the time being, gradually matured transgenic technology makes it possible to produce transgenic animals that are able to synthesize n-3 PUFAs by themselves. However, the transgenic technology itself may bring negative impacts. In this study, the eukaryotic expression vector pcDNA3.1-FatI was introduced into the genome of Boer goat fetal fibroblasts cultured in vitro, and the influence of biological characteristics of the fetal fibroblast was studied via overexpression of FatI. The results showed that the proliferation and apoptosis of cultured fetal fibroblast were not affected significantly by the overexpression of FatI using BrdU and TUNEL staining methods, respectively. Moreover, the overexpression of FatI significantly inhibited the senescence of somatic cells compared with enhanced green fluorescent protein (EGFP) transgenic cells (P < 0.01). Quantitative PCR revealed that the mRNA expression of P16 and P53 in the FatI transgenic cell group was significantly lower than that in the EGFP transgenic cell group (P < 0.01). In conclusion, the senescence of goat somatic cells was inhibited by the overexpression of the FatI gene.

Biosynthesis of polyunsaturated fatty acids in the oleaginous marine diatom Fistulifera sp. strain JPCC DA0580.

Studies of polyunsaturated fatty acid (PUFA) biosynthesis in microalgae are of great importance for many reasons, including the production of biofuel and variable omega 3-long chain PUFAs. The elucidation of the PUFA biosynthesis pathway is necessary for bioengineering to increase or decrease PUFA content in certain microalgae. In this study, we identified the PUFA synthesis pathway in the oleaginous marine diatom, Fistulifera sp. strain JPCC DA0580, a promising candidate for biodiesel production. The data revealed not only the presence of the desaturases and elongases involved in eicosapentaenoic acid (EPA) synthesis, but also the unexpected localization of ω3-desaturase expression in the chloroplast. This suggests that this microalga might perform the final step of EPA synthesis in the chloroplast and not in the endoplasmic reticulum (ER) like other diatoms. The detailed fatty acid profile suggests that the EPA was synthesized only through the ω6-pathway in this strain, which was also different from other diatoms. Finally, the transcriptome analysis demonstrated an overall down-regulation of desaturases and elongases over incubation time. These genetic features might explain the decrease of PUFA percentage over incubation time in this strain. The important insights into metabolite synthesis acquired here will be useful for future metabolic engineering to control PUFA content in this diatom.

Meat quality attributes of the Longissimus lumborum muscle of the Kh'ara genotype of llama (Lama glama) reared extensively in northern Chile.

Twenty male llama of the Kh'ara genotype, reared extensively in the north of Chile, were slaughtered at ages between 2 and 4 permanent teeth (2 to 3.5years) and analyses were carried out on the Longissimus lumborum muscle, including composition (moisture, fat, protein, ash, cholesterol, amino acids, fatty acid profile and collagen content) and meat quality parameters (pH, color, water holding capacity and Warner-Bratzler shear-force). Llama meat was characterized by a low cholesterol (39.04mg/100g) and intramuscular fat (1.56%) content, a total collagen content of 6.28mg/g, of which 20.28% was soluble collagen. Amino acid composition and fatty acid profile were similar to those found for beef finished on forage. Llama meat showed a low n-6/n-3 (4.69) and hypocholesterolemic/hypercholesterolemic (1.55) ratio and acceptable values of DFA (65.78%). Quality parameters in llama Longissimus muscle were within the ranges reported for more traditional meats such as beef and lamb.