Publications
383 results found
Hall Z, Ament Z, Wilson CH, et al., 2016, Myc expression drives aberrant lipid metabolism in lung cancer, Cancer Research, Vol: 76, Pages: 4608-4618, ISSN: 1538-7445
MYC-mediated pathogenesis in lung cancer continues to attract interest for new therapeutic strategies. In this study, we describe a transgenic mouse model of KRAS-driven lung adenocarcinoma that affords reversible activation of MYC, used here as a tool for lipidomic profiling of MYC-dependent lung tumors formed in this model. Advanced mass spectrometric imaging and surface analysis techniques were used to characterize the spatial and temporal changes in lipid composition in lung tissue. We found that normal lung tissue was characterized predominantly by saturated phosphatidylcholines and phosphatidylglycerols, which are major lipid components of pulmonary surfactant. In contrast, tumor tissues displayed an increase in phosphatidylinositols and arachidonate-containing phospholipids that can serve as signaling precursors. Deactivating MYC resulted in a rapid and dramatic decrease in arachidonic acid and its eicosanoid metabolites. In tumors with high levels of MYC, we found an increase in cytosolic phospholipase A2 (cPLA2) activity with a preferential release of membrane-bound arachidonic acid, stimulating the lipoxygenase (LOX) and COX pathways also amplified by MYC at the level of gene expression. Deactivating MYC lowered cPLA2 activity along with COX2 and 5-LOX mRNA levels. Notably, inhibiting the COX/5-LOX pathways in vivo reduced tumor burden in a manner associated with reduced cell proliferation. Taken together, our results show how MYC drives the production of specific eicosanoids critical for lung cancer cell survival and proliferation, with possible implications for the use of COX and LOX pathway inhibitors for lung cancer therapy. Cancer Res; 76(16); 4608-18. ©2016 AACR.
Cox PJ, Kirk T, Ashmore T, et al., 2016, Nutritional ketosis alters fuel preference and thereby endurance Performance in athletes, Cell Metabolism, Vol: 24, Pages: 256-268, ISSN: 1550-4131
Ketosis, the metabolic response to energy crisis, is a mechanism to sustain life by altering oxidative fuel selection. Often overlooked for its metabolic potential, ketosis is poorly understood outside of starvation or diabetic crisis. Thus, we studied the biochemical advantages of ketosis in humans using a ketone ester-based form of nutrition without the unwanted milieu of endogenous ketone body production by caloric or carbohydrate restriction. In five separate studies of 39 high-performance athletes, we show how this unique metabolic state improves physical endurance by altering fuel competition for oxidative respiration. Ketosis decreased muscle glycolysis and plasma lactate concentrations, while providing an alternative substrate for oxidative phosphorylation. Ketosis increased intramuscular triacylglycerol oxidation during exercise, even in the presence of normal muscle glycogen, co-ingested carbohydrate and elevated insulin. These findings may hold clues to greater human potential and a better understanding of fuel metabolism in health and disease.
Forouhi NG, Imamura F, Sharp SJ, et al., 2016, Association of Plasma Phospholipid n-3 and n-6 Polyunsaturated Fatty Acids with Type 2 Diabetes: The EPIC-InterAct Case-Cohort Study, PLOS Medicine, Vol: 13, ISSN: 1549-1277
BACKGROUND: Whether and how n-3 and n-6 polyunsaturated fatty acids (PUFAs) are related to type 2 diabetes (T2D) is debated. Objectively measured plasma PUFAs can help to clarify these associations. METHODS AND FINDINGS: Plasma phospholipid PUFAs were measured by gas chromatography among 12,132 incident T2D cases and 15,919 subcohort participants in the European Prospective Investigation into Cancer and Nutrition (EPIC)-InterAct study across eight European countries. Country-specific hazard ratios (HRs) were estimated using Prentice-weighted Cox regression and pooled by random-effects meta-analysis. We also systematically reviewed published prospective studies on circulating PUFAs and T2D risk and pooled the quantitative evidence for comparison with results from EPIC-InterAct. In EPIC-InterAct, among long-chain n-3 PUFAs, α-linolenic acid (ALA) was inversely associated with T2D (HR per standard deviation [SD] 0.93; 95% CI 0.88-0.98), but eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were not significantly associated. Among n-6 PUFAs, linoleic acid (LA) (0.80; 95% CI 0.77-0.83) and eicosadienoic acid (EDA) (0.89; 95% CI 0.85-0.94) were inversely related, and arachidonic acid (AA) was not significantly associated, while significant positive associations were observed with γ-linolenic acid (GLA), dihomo-GLA, docosatetraenoic acid (DTA), and docosapentaenoic acid (n6-DPA), with HRs between 1.13 to 1.46 per SD. These findings from EPIC-InterAct were broadly similar to comparative findings from summary estimates from up to nine studies including between 71 to 2,499 T2D cases. Limitations included potential residual confounding and the inability to distinguish between dietary and metabolic influences on plasma phospholipid PUFAs. CONCLUSIONS: These large-scale findings suggest an important inverse association of circulating plant-origin n-3 PUFA (ALA) but no convincing association of marine-derived n3 PUFAs (EPA and DHA) with T2D. Moreover, they hi
Ament Z, West JA, Stanley E, et al., 2016, PPAR-pan activation induces hepatic oxidative stress and lipidomic remodelling., Free Radic Biol Med, Vol: 95, Pages: 357-368
The peroxisome proliferator-activated receptors (PPARs) are ligand activated nuclear receptors that regulate cellular homoeostasis and metabolism. PPARs control the expression of genes involved in fatty-acid and lipid metabolism. Despite evidence showing beneficial effects of their activation in the treatment of metabolic diseases, particularly dyslipidaemias and type 2 diabetes, PPAR agonists have also been associated with a variety of side effects and adverse pathological changes. Agonists have been developed that simultaneously activate the three PPAR receptors (PPARα, γ and δ) in the hope that the beneficial effects can be harnessed while avoiding some of the negative side effects. In this study, the hepatic effects of a discontinued PPAR-pan agonist (a triple agonist of PPAR-α, -γ, and -δ), was investigated after dietary treatment of male Sprague-Dawley (SD) rats. The agonist induced liver enlargement in conjunction with metabolomic and lipidomic remodelling. Increased concentrations of several metabolites related to processes of oxidation, such as oxo-methionine, methyl-cytosine and adenosyl-methionine indicated increased stress and immune status. These changes are reflected in lipidomic changes, and increased energy demands as determined by free fatty acid (decreased 18:3 n-3, 20:5 n-3 and increased ratios of n-6/n-3 fatty acids) triacylglycerol, phospholipid (decreased and increased bulk changes respectively) and eicosanoid content (increases in PGB2 and 15-deoxy PGJ2). We conclude that the investigated PPAR agonist, GW625019, induces liver enlargement, accompanied by lipidomic remodelling, oxidative stress and increases in several pro-inflammatory eicosanoids. This suggests that such pathways should be monitored in the drug development process and also outline how PPAR agonists induce liver proliferation.
Taegtmeyer H, Young ME, Lopaschuk GD, et al., 2016, Assessing Cardiac Metabolism: A Scientific Statement From the American Heart Association., Circ Res, Vol: 118, Pages: 1659-1701
In a complex system of interrelated reactions, the heart converts chemical energy to mechanical energy. Energy transfer is achieved through coordinated activation of enzymes, ion channels, and contractile elements, as well as structural and membrane proteins. The heart's needs for energy are difficult to overestimate. At a time when the cardiovascular research community is discovering a plethora of new molecular methods to assess cardiac metabolism, the methods remain scattered in the literature. The present statement on "Assessing Cardiac Metabolism" seeks to provide a collective and curated resource on methods and models used to investigate established and emerging aspects of cardiac metabolism. Some of those methods are refinements of classic biochemical tools, whereas most others are recent additions from the powerful tools of molecular biology. The aim of this statement is to be useful to many and to do justice to a dynamic field of great complexity.
Sanders FWB, Griffin JL, 2016, De novo lipogenesis in the liver in health and disease: more than just a shunting yard for glucose, Biological Reviews of the Cambridge Philosophical Society, Vol: 91, Pages: 452-468, ISSN: 1464-7931
Hepatic de novo lipogenesis (DNL) is the biochemical process of synthesising fatty acids from acetyl-CoA subunits that are produced from a number of different pathways within the cell, most commonly carbohydrate catabolism. In addition to glucose which most commonly supplies carbon units for DNL, fructose is also a profoundly lipogenic substrate that can drive DNL, important when considering the increasing use of fructose in corn syrup as a sweetener. In the context of disease, DNL is thought to contribute to the pathogenesis of non-alcoholic fatty liver disease, a common condition often associated with the metabolic syndrome and consequent insulin resistance. Whether DNL plays a significant role in the pathogenesis of insulin resistance is yet to be fully elucidated, but it may be that the prevalent products of this synthetic process induce some aspect of hepatic insulin resistance.
Sanders F, McNally B, Griffin JL, 2016, Blood triacylglycerols: a lipidomic window on diet and disease., 5TH EUROPEAN LIPIDOMIC MEETING, Pages: 638-644
Although the measurement of triacylglycerols (TAGs) by clinical chemistry has been used in the diagnosis of a range of metabolic diseases, such approaches ignore the different species of TAGs that contribute to the total concentration. With the advent of LC and direct infusion forms of MS it is now possible to profile the individual TAGs in blood plasma or tissue extracts. This mini review surveys the information that is obtainable from the lipidomic profiling of TAGs in following metabolic diseases such as type 2 diabetes (T2DM), cardiovascular disease (CVD) and non-alcoholic fatty liver disease, as well as the development of insulin resistance and obesity.
Tan CY, Virtue S, Murfitt S, et al., 2016, Erratum: Adipose tissue fatty acid chain length and mono-unsaturation increases with obesity and insulin resistance (Scientific Reports (2015) 5:18366 DOI:10.1038/srep18366), Scientific Reports, Vol: 6
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Kale NS, Haug K, Conesa P, et al., 2016, MetaboLights: An Open-Access Database Repository for Metabolomics Data., Curr Protoc Bioinformatics, Vol: 53, Pages: 14.13.1-14.13.18
MetaboLights is the first general purpose, open-access database repository for cross-platform and cross-species metabolomics research at the European Bioinformatics Institute (EMBL-EBI). Based upon the open-source ISA framework, MetaboLights provides Metabolomics Standard Initiative (MSI) compliant metadata and raw experimental data associated with metabolomics experiments. Users can upload their study datasets into the MetaboLights Repository. These studies are then automatically assigned a stable and unique identifier (e.g., MTBLS1) that can be used for publication reference. The MetaboLights Reference Layer associates metabolites with metabolomics studies in the archive and is extensively annotated with data fields such as structural and chemical information, NMR and MS spectra, target species, metabolic pathways, and reactions. The database is manually curated with no specific release schedules. MetaboLights is also recommended by journals for metabolomics data deposition. This unit provides a guide to using MetaboLights, downloading experimental data, and depositing metabolomics datasets using user-friendly submission tools.
West JA, Beqqali A, Ament Z, et al., 2016, A targeted metabolomics assay for cardiac metabolism and demonstration using a mouse model of dilated cardiomyopathy, Metabolomics, Vol: 12, ISSN: 1573-3882
Metabolomics can be performed either as an ‘open profiling’ tool where the aim is to measure, usually in a semi-quantitative manner, as many metabolites as possible or perform ‘closed’ or ‘targeted’ analyses where instead a pre-defined set of metabolites are measured. Targeted methods can be designed to be more sensitive and quantitative and so are particularly appropriate to systems biology for quantitative models of systems or when metabolomics is performed in a hypothesis driven manner to test whether a particular pathway is perturbed. We describe a targeted metabolomics assay that quantifies a broad range of over 130 metabolites relevant to cardiac metabolism including the pathways of the citric acid cycle, fatty acid oxidation, glycolysis, the pentose phosphate pathway, amino acid metabolism, the urea cycle, nucleotides and reactive oxygen species using tandem mass spectrometry to produce quantitative, sensitive and robust data. This assay is illustrated by profiling cardiac metabolism in a lamin A/C (Lmna) mouse model of dilated cardiomyopathy (DCM). The model of DCM was characterised by increases in concentrations of proline and methyl-histidine suggestive of increased myofibrillar and collagen degradation, as well as decreases in a number of citric acid cycle intermediates and carnitine derivatives indicating reduced energy metabolism in the dilated heart. These assays could be used for any other cardiac or cardiovascular disease in that they cover central core metabolism and key pathways involved in cardiac metabolism, and may provide a general start for many mammalian systems.
Roberts LD, Ashmore T, Murray AJ, et al., 2016, Response to Comment on Lee et al. Diabetes 2015;64:2836-2846. Comment on Roberts et al. Diabetes 2015;64:471-484., Diabetes, Vol: 65
Auffray C, Caulfield T, Griffin JL, et al., 2016, From genomic medicine to precision medicine: highlights of 2015., Genome Medicine: medicine in the post-genomic era, Vol: 8, Pages: 12-12, ISSN: 1756-994X
Swatton JE, Davenport PW, Maunders EA, et al., 2016, Impact of Azithromycin on the Quorum Sensing-Controlled Proteome of Pseudomonas aeruginosa, PLoS One, Vol: 11, ISSN: 1932-6203
The macrolide antibiotic, azithromycin (AZM), has been reported to improve the clinical outcome of cystic fibrosis patients, many of whom are chronically-infected with Pseudomonas aeruginosa. However, the highest clinically-achievable concentrations of this drug are well-below the minimum inhibitory concentration for P. aeruginosa, raising the question of why AZM exhibits therapeutic activity. One possibility that has been raised by earlier studies is that AZM inhibits quorum sensing (QS) by P. aeruginosa. To explicitly test this hypothesis the changes brought about by AZM treatment need to be compared with those associated with specific QS mutants grown alongside in the same growth medium, but this has not been done. In this work, we used quantitative 2D-difference gel electrophoresis and 1H-NMR spectroscopy footprint analysis to examine whether a range of clinically-relevant AZM concentrations elicited proteomic and metabolomic changes in wild-type cultures that were similar to those seen in cultures of defined QS mutants. Consistent with earlier reports, over half of the AZM-induced spot changes on the 2D gels were found to affect QS-regulated proteins. However, AZM modulated very few protein spots overall (compared with QS) and collectively, these modulated proteins comprised only a small fraction (12-13%) of the global QS regulon. We conclude that AZM perturbs a sub-regulon of the QS system but does not block QS per se. Reinforcing this notion, we further show that AZM is capable of attenuating virulence factor production in another Gram-negative species that secretes copious quantities of exoenzymes (Serratia marcescens), even in the absence of a functional QS system.
Griffin JL, Salek RM, 2016, NMR Spectroscopy of Tissues, <sup>1</sup>H MAS, Encyclopedia of Spectroscopy and Spectrometry, Pages: 254-259, ISBN: 9780128032244
High-resolution magic angle spinning NMR spectroscopy is being increasingly applied to biologic samples, particularly mammalian tissues. In this article, the theory behind the technique and the experimental approaches are briefly introduced and the main applications summarized.
McNally B, Griffin JL, Roberts LD, 2016, Dietary inorganic nitrate: From villain to hero in metabolic disease?, Molecular Nutrition and Food Research, Vol: 60, Pages: 67-78, ISSN: 1613-4125
Historically, inorganic nitrate was believed to be an inert by-product of nitric oxide (NO) metabolism that was readily excreted by the body. Studies utilising doses of nitrate far in excess of dietary and physiological sources reported potentially toxic and carcinogenic effects of the anion. However, nitrate is a significant component of our diets, with the majority of the anion coming from green leafy vegetables, which have been consistently shown to offer protection against obesity, type 2 diabetes and metabolic diseases. The discovery of a metabolic pathway in mammals, in which nitrate is reduced to NO, via nitrite, has warranted a re-examination of the physiological role of this small molecule. Obesity, type 2 diabetes and the metabolic syndrome are associated with a decrease in NO bioavailability. Recent research suggests that the nitrate-nitrite-NO pathway may be harnessed as a therapeutic to supplement circulating NO concentrations, with both anti-obesity and anti-diabetic effects, as well as improving vascular function. In this review, we examine the key studies that have led to the re-evaluation of the physiological function of inorganic nitrate, from toxic and carcinogenic metabolite, to a potentially important and beneficial agent in the treatment of metabolic disease.
Keller MA, Zylstra A, Castro C, et al., 2016, Conditional iron and pH-dependent activity of a non-enzymatic glycolysis and pentose phosphate pathway, Science Advances, Vol: 2, ISSN: 2375-2548
Little is known about the evolutionary origins of metabolism. However, key biochemical reactions of glycolysis and the pentose phosphate pathway (PPP), ancient metabolic pathways central to the metabolic network, have non-enzymatic pendants that occur in a prebiotically plausible reaction milieu reconstituted to contain Archean sediment metal components. These non-enzymatic reactions could have given rise to the origin of glycolysis and the PPP during early evolution. Using nuclear magnetic resonance spectroscopy and high-content metabolomics that allowed us to measure several thousand reaction mixtures, we experimentally address the chemical logic of a metabolism-like network constituted from these non-enzymatic reactions. Fe(II), the dominant transition metal component of Archean oceanic sediments, has binding affinity toward metabolic sugar phosphates and drives metabolism-like reactivity acting as both catalyst and cosubstrate. Iron and pH dependencies determine a metabolism-like network topology and comediate reaction rates over several orders of magnitude so that the network adopts conditional activity. Alkaline pH triggered the activity of the non-enzymatic PPP pendant, whereas gentle acidic or neutral conditions favored non-enzymatic glycolytic reactions. Fe(II)-sensitive glycolytic and PPP-like reactions thus form a chemical network mimicking structural features of extant carbon metabolism, including topology, pH dependency, and conditional reactivity. Chemical networks that obtain structure and catalysis on the basis of transition metals found in Archean sediments are hence plausible direct precursors of cellular metabolic networks.
Griffin JL, Rubtsov DV, 2016, Analytical methodology standards for metabolomics, Encyclopedia of Spectroscopy and Spectrometry, Pages: 26-30, ISBN: 9780128032244
The need for standard operating protocols (SOPs) has long been recognized in all branches of analytical chemistry and is especially useful in transferring a given assay from one laboratory to another and for the cross-comparison of results. However, the field of standardized protocols has received renewed interest following the completion of the human genome project and the birth of functional genomics. The use of analytical equipment such as NMR spectroscopy and mass spectrometry in metabolomics, proteomics, and related functional genomic approaches has led to an increased need to standardize the reporting of data acquisition so that results in one laboratory can be validated in another. Ultimately databases can be produced of experimental data that catalog a tier of cellular organization, and in this manner a systems biology description of the biological world is approached. Given that any true description of the proteome or metabolome must by very definition consider all the changes that occur to these dynamic systems, it becomes clear that a full description will only be achieved by community-led initiatives, and thus standardized protocols become a vital cornerstone of any such endeavor. This article surveys recent developments in the area of standard reporting of protocols in metabolomics. However, to do this, it is first necessary to set the context of standardization of protocols in biology in general and the field of functional genomics in particular.
Ashmore T, Roberts LD, Morash AJ, et al., 2015, Nitrate enhances skeletal muscle fatty acid oxidation via a nitric oxide-cGMP-PPAR-mediated mechanism, BMC Biology, Vol: 13, Pages: 1-17, ISSN: 1741-7007
BackgroundInsulin sensitivity in skeletal muscle is associated with metabolic flexibility, including a high capacity to increase fatty acid (FA) oxidation in response to increased lipid supply. Lipid overload, however, can result in incomplete FA oxidation and accumulation of potentially harmful intermediates where mitochondrial tricarboxylic acid cycle capacity cannot keep pace with rates of β-oxidation. Enhancement of muscle FA oxidation in combination with mitochondrial biogenesis is therefore emerging as a strategy to treat metabolic disease. Dietary inorganic nitrate was recently shown to reverse aspects of the metabolic syndrome in rodents by as yet incompletely defined mechanisms.ResultsHerein, we report that nitrate enhances skeletal muscle FA oxidation in rodents in a dose-dependent manner. We show that nitrate induces FA oxidation through a soluble guanylate cyclase (sGC)/cGMP-mediated PPARβ/δ- and PPARα-dependent mechanism. Enhanced PPARβ/δ and PPARα expression and DNA binding induces expression of FA oxidation enzymes, increasing muscle carnitine and lowering tissue malonyl-CoA concentrations, thereby supporting intra-mitochondrial pathways of FA oxidation and enhancing mitochondrial respiration. At higher doses, nitrate induces mitochondrial biogenesis, further increasing FA oxidation and lowering long-chain FA concentrations. Meanwhile, nitrate did not affect mitochondrial FA oxidation in PPARα−/− mice. In C2C12 myotubes, nitrate increased expression of the PPARα targets Cpt1b, Acadl, Hadh and Ucp3, and enhanced oxidative phosphorylation rates with palmitoyl-carnitine; however, these changes in gene expression and respiration were prevented by inhibition of either sGC or protein kinase G. Elevation of cGMP, via the inhibition of phosphodiesterase 5 by sildenafil, also increased expression of Cpt1b, Acadl and Ucp3, as well as CPT1B protein levels, and further enhanced the effect of nitrate s
Yew Tan C, Virtue S, Murfitt S, et al., 2015, Adipose tissue fatty acid chain length and mono-unsaturation increases with obesity and insulin resistance, Scientific Reports, Vol: 5, ISSN: 2045-2322
The non-essential fatty acids, C18:1n9, C16:0, C16:1n7, C18:0 and C18:1n7 account for over 75% of fatty acids in white adipose (WAT) triacylglycerol (TAG). The relative composition of these fatty acids (FA) is influenced by the desaturases, SCD1-4 and the elongase, ELOVL6. In knock-out models, loss of SCD1 or ELOVL6 results in reduced Δ9 desaturated and reduced 18-carbon non-essential FA respectively. Both Elovl6 KO and SCD1 KO mice exhibit improved insulin sensitivity. Here we describe the relationship between WAT TAG composition in obese mouse models and obese humans stratified for insulin resistance. In mouse models with increasing obesity and insulin resistance, there was an increase in scWAT Δ9 desaturated FAs (SCD ratio) and FAs with 18-carbons (Elovl6 ratio) in mice. Data from mouse models discordant for obesity and insulin resistance (AKT2 KO, Adiponectin aP2-transgenic), suggested that scWAT TAG Elovl6 ratio was associated with insulin sensitivity, whereas SCD1 ratio was associated with fat mass. In humans, a greater SCD1 and Elovl6 ratio was found in metabolically more harmful visceral adipose tissue when compared to subcutaneous adipose tissue.
Tan CY, Virtue S, Bidault G, et al., 2015, Brown Adipose Tissue Thermogenic Capacity Is Regulated by Elovl6., Cell Rep, Vol: 13, Pages: 2039-2047
Although many transcriptional pathways regulating BAT have been identified, the role of lipid biosynthetic enzymes in thermogenesis has been less investigated. Whereas cold exposure causes changes in the fatty acid composition of BAT, the functional consequences of this remains relatively unexplored. In this study, we demonstrate that the enzyme Elongation of Very Long Chain fatty acids 6 (Elovl6) is necessary for the thermogenic action of BAT. Elovl6 is responsible for converting C16 non-essential fatty acids into C18 species. Loss of Elovl6 does not modulate traditional BAT markers; instead, it causes reduced expression of mitochondrial electron transport chain components and lower BAT thermogenic capacity. The reduction in BAT activity appears to be counteracted by increased beiging of scWAT. When beige fat is disabled by thermoneutrality or aging, Elovl6 KO mice gain weight and have increased scWAT mass and impaired carbohydrate metabolism. Overall, our study suggests fatty acid chain length is important for BAT function.
Osei M, Griffin JL, Koulman A, 2015, Hyphenating size-exclusion chromatography with electrospray mass spectrometry; using on-line liquid-liquid extraction to study the lipid composition of lipoprotein particles, Rapid Communications in Mass Spectrometry, Vol: 29, Pages: 1969-1976, ISSN: 0951-4198
RATIONALE: Lipoproteins belong to the most commonly measured clinical biochemical parameters. Lipidomics is an orthogonal approach and aims to profile the individual lipid molecules that jointly form the lipoprotein particles. However, in the first step of the extraction of lipid molecules from serum, an organic solvent is used leading to dissociation of the lipoproteins. Thus far it has been impossible to combine lipidomics and lipoprotein analysis in one analytical system. METHODS: Human plasma was diluted in phosphate-buffered saline (PBS) and injected onto a Superose 6 PC 3.2 column with PBS as a mobile phase to separate lipoproteins. The eluent was led to a Syrris FLLEX module, which also received CHCl3 /MeOH (3:1). The two phases were mixed and subsequently separated using a Teflon membrane in an especially designed pressurized flow chamber. The organic phase was led to a standard electrospray source of an Orbitrap mass spectrometer. RESULTS: Size-exclusion chromatography (SEC) has been commonly applied to separate lipoproteins and is considered a practical alternative to ultracentrifugation. Through the on-line liquid-liquid extraction method it becomes possible to obtained detailed mass spectra of lipids across different lipoprotein fractions. The extracted ion chromatograms of specific lipid signals showed their distribution against the size of lipoprotein particles. CONCLUSIONS: The application of on-line liquid-liquid extraction allows for the continuous electrospray-based mass spectral analysis of SEC eluent, providing the detailed lipid composition of lipoprotein particles separated by size. This approach provides new possibilities for the study of the biochemistry of lipoproteins.
Kuhnle GGC, Tasevska N, Lentjes MAH, et al., 2015, Association between sucrose intake and risk of overweight and obesity in a prospective sub-cohort of the European Prospective Investigation into Cancer in Norfolk (EPIC-Norfolk)., Public Health Nutrition, Vol: 18, Pages: 2815-2824, ISSN: 1368-9800
OBJECTIVE: The objective of the present study was to investigate associations between sugar intake and overweight using dietary biomarkers in the Norfolk cohort of the European Prospective Investigation into Cancer and Nutrition (EPIC-Norfolk). DESIGN: Prospective cohort study. SETTING: EPIC-Norfolk in the UK, recruitment between 1993 and 1997. SUBJECTS: Men and women (n 1734) aged 39-77 years. Sucrose intake was assessed using 7 d diet diaries. Baseline spot urine samples were analysed for sucrose by GC-MS. Sucrose concentration adjusted by specific gravity was used as a biomarker for intake. Regression analyses were used to investigate associations between sucrose intake and risk of BMI>25·0 kg/m2 after three years of follow-up. RESULTS: After three years of follow-up, mean BMI was 26·8 kg/m2. Self-reported sucrose intake was significantly positively associated with the biomarker. Associations between the biomarker and BMI were positive (β=0·25; 95 % CI 0·08, 0·43), while they were inverse when using self-reported dietary data (β=-1·40; 95 % CI -1·81, -0·99). The age- and sex-adjusted OR for BMI>25·0 kg/m2 in participants in the fifth v. first quintile was 1·54 (95 % CI 1·12, 2·12; P trend=0·003) when using biomarker and 0·56 (95 % CI 0·40, 0·77; P trend<0·001) with self-reported dietary data. CONCLUSIONS: Our results suggest that sucrose measured by objective biomarker but not self-reported sucrose intake is positively associated with BMI. Future studies should consider the use of objective biomarkers of sucrose intake.
Senyilmaz D, Virtue S, Xu X, et al., 2015, Regulation of mitochondrial morphology and function by stearoylation of TFR1, Nature, Vol: 525, Pages: 124-128, ISSN: 0028-0836
Mitochondria are involved in a variety of cellular functions, including ATP production, amino acid and lipid biogenesis and breakdown, signalling and apoptosis. Mitochondrial dysfunction has been linked to neurodegenerative diseases, cancer and ageing. Although transcriptional mechanisms that regulate mitochondrial abundance are known, comparatively little is known about how mitochondrial function is regulated. Here we identify the metabolite stearic acid (C18:0) and human transferrin receptor 1 (TFR1; also known as TFRC) as mitochondrial regulators. We elucidate a signalling pathway whereby C18:0 stearoylates TFR1, thereby inhibiting its activation of JNK signalling. This leads to reduced ubiquitination of mitofusin via HUWE1, thereby promoting mitochondrial fusion and function. We find that animal cells are poised to respond to both increases and decreases in C18:0 levels, with increased C18:0 dietary intake boosting mitochondrial fusion in vivo. Intriguingly, dietary C18:0 supplementation can counteract the mitochondrial dysfunction caused by genetic defects such as loss of the Parkinson's disease genes Pink or Parkin in Drosophila. This work identifies the metabolite C18:0 as a signalling molecule regulating mitochondrial function in response to diet.
Dickens AM, Larkin JR, Davis BG, et al., 2015, NMR-Based Metabolomics Separates the Distinct Stages of Disease in a Chronic Relapsing Model of Multiple Sclerosis., J Neuroimmune Pharmacol, Vol: 10, Pages: 435-444
Relapsing experimental allergic encephalomyelitis (Cr-EAE) is commonly used to explore the pathogenesis and efficacy of new therapies for MS, but it is unclear whether the metabolome of Cr-EAE is comparable to human multiple sclerosis (MS). For MS, the diagnosis and staging can be achieved by metabolomics on blood using a combination of magnetic resonance spectroscopy and partial least squares discriminant analysis (PLS-DA). Here, we sought to discover whether this approach could be used to differentiate between sequential disease states in Cr-EAE and whether the same metabolites would be discriminatory. Urine and plasma samples were obtained at different time-points from a clinically relevant model of MS. Using PLS-DA modelling for the urine samples furnished some predictive models, but could not discriminate between all disease states. However, PLS-DA modelling of the plasma samples was able to distinguish between animals with clinically silent disease (day 10, 28) and animals with active disease (day 14, 38). We were also able to distinguish Cr-EAE mice from naive mice at all-time points and control mice, treated with complete Freund's adjuvant alone, at day 14 and 38. Key metabolites that underpin these models included fatty acids, glucose and taurine. Two of these metabolites, fatty acids and glucose, were also key metabolites in separating relapsing-remitting MS from secondary-progressive MS in the human study. These results demonstrate the sensitivity of this metabolomics approach for distinguishing between different disease states. Furthermore, some, but not all, of the changes in metabolites were conserved in humans and the mouse model, which could be useful for future drug development.
Vacca M, Allison M, Griffin JL, et al., 2015, Fatty Acid and Glucose Sensors in Hepatic Lipid Metabolism: Implications in NAFLD., Semin Liver Dis, Vol: 35, Pages: 250-261
The term nonalcoholic fatty liver disease (NAFLD) covers a pathologic spectrum from lipid accumulation alone (simple steatosis) to steatosis with associated inflammation and fibrosis (nonalcoholic steatohepatitis [NASH]). Nonalcoholic steatohepatitis can progress to cirrhosis and potentially to hepatocellular carcinoma. Although a genetic predisposition has been highlighted, NAFLD is strongly associated with an unhealthy lifestyle and hypercaloric diet in the context of obesity and metabolic disease. The dysregulation of specific pathways (insulin signaling, mitochondrial function, fatty acid, and lipoprotein metabolism) have been linked to steatosis, but elucidating the molecular events determining evolution of the disease still requires further research before it can be translated into specific personalized interventional strategies. In this review, the authors focus on the early events of the pathophysiology of NASH, dissecting the metabolic and nutritional pathways involving fatty acids and glucose sensors that can modulate lipid accumulation in the liver, but also condition the progression to cirrhosis and hepatocellular carcinoma.
Salek RM, Neumann S, Schober D, et al., 2015, Erratum to: COordination of Standards in MetabOlomicS (COSMOS): facilitating integrated metabolomics data access, Metabolomics, Vol: 11, Pages: 1587-1597, ISSN: 1573-3882
Metabolomics has become a crucial phenotyping technique in a range of research fields including medicine, the life sciences, biotechnology and the environmental sciences. This necessitates the transfer of experimental information between research groups, as well as potentially to publishers and funders. After the initial efforts of the metabolomics standards initiative, minimum reporting standards were proposed which included the concepts for metabolomics databases. Built by the community, standards and infrastructure for metabolomics are still needed to allow storage, exchange, comparison and re-utilization of metabolomics data. The Framework Programme 7 EU Initiative ‘coordination of standards in metabolomics’ (COSMOS) is developing a robust data infrastructure and exchange standards for metabolomics data and metadata. This is to support workflows for a broad range of metabolomics applications within the European metabolomics community and the wider metabolomics and biomedical communities’ participation. Here we announce our concepts and efforts asking for re-engagement of the metabolomics community, academics and industry, journal publishers, software and hardware vendors, as well as those interested in standardisation worldwide (addressing missing metabolomics ontologies, complex-metadata capturing and XML based open source data exchange format), to join and work towards updating and implementing metabolomics standards.
Wang X, West JA, Murray AJ, et al., 2015, Comprehensive Metabolic Profiling of Age-Related Mitochondrial Dysfunction in the High-Fat-Fed ob/ob Mouse Heart., J Proteome Res, Vol: 14, Pages: 2849-2862
The ectopic deposition of fat is thought to lead to lipotoxicity and has been associated with mitochondrial dysfunction and diabetic cardiomyopathy. We have measured mitochondrial respiratory capacities in the hearts of ob/ob and wild-type mice on either a regular chow (RCD) or high-fat (HFD) diet across four age groups to investigate the impact of diet and age on mitochondrial function alongside a comprehensive strategy for metabolic profiling of the tissue. Myocardial mitochondrial dysfunction was only evident in ob/ob mice on RCD at 14 months, but it was detectable at 3 months on the HFD. Liquid chromatography-mass spectrometry (LC-MS) was used to study the profiles of acylcarnitines and the accumulation of triglycerides, but neither class of lipid was associated with mitochondrial dysfunction. However, a targeted LC-MS/MS analysis of markers of oxidative stress demonstrated increases in GSSG/GSH and 8-oxoguanine, in addition to the accumulation of diacylglycerols, which are lipid species linked to lipotoxicity. Our results demonstrate that myocardial mitochondria in ob/ob mice on RCD maintained a similar respiratory capacity to that of wild type until a late stage in aging. However, on a HFD, unlike wild-type mice, ob/ob mice failed to increase mitochondrial respiration, which may be associated with a complex I defect following increased oxidative damage.
Virtue S, Masoodi M, de Weijer BAM, et al., 2015, Prostaglandin profiling reveals a role for haematopoietic prostaglandin D synthase in adipose tissue macrophage polarisation in mice and humans, International Journal of Obesity, Vol: 39, Pages: 1151-1160, ISSN: 0307-0565
BACKGROUND/OBJECTIVES: Obesity has been associated with both changes in adipose tissue lipid metabolism and inflammation. A key class of lipid-derived signalling molecules involved in inflammation are the prostaglandins. In this study, we aimed to determine how obesity affects the levels of prostaglandins within white adipose tissue (WAT) and determine which cells within adipose tissue produce them. To avoid the effects of cellular stress on prostaglandin levels, we developed a multivariate statistical approach in which metabolite concentrations and transcriptomic data were integrated, allowing the assignment of metabolites to cell types. SUBJECTS/METHODS: Eicosanoids were measured by liquid chromatography-tandem mass spectrometry and mRNA levels using real-time PCR. Eicosanoid levels and transcriptomic data were combined using principal component analysis and hierarchical clustering in order to associate metabolites with cell types. Samples were obtained from C57Bl/6 mice aged 16 weeks. We studied the ob/ob genetically obese mouse model and diet-induced obesity model. We extended our results in mice to a cohort of morbidly obese humans undergoing bariatric surgery. RESULTS: Using our modelling approach, we determined that prostglandin D₂ (PGD₂) in adipose tissue was predominantly produced in macrophages by the haematopoietic isoform of prostaglandin D synthase (H-Pgds). Analysis of sub-fractionated WAT confirmed that H-Pgds was expressed in adipose tissue macrophages (ATMs). Furthermore, H-Pgds expression in ATMs isolated from lean and obese mice was consistent with it affecting macrophage polarisation. Functionally, we demonstrated that H-PGDS-produced PGD₂ polarised macrophages toward an M2, anti-inflammatory state. In line with a potential anti-inflammatory role, we found that H-PGDS expression in ATMs was positively correlated with both peripheral insulin and adipose tissue insulin sensitivity in humans. CONCLUSIONS: In this study, we have developed a method to
Castro C, Briggs W, Paschos GK, et al., 2015, A metabolomic study of adipose tissue in mice with a disruption of the circadian system., Mol Biosyst, Vol: 11, Pages: 1897-1906
Adipose tissue functions in terms of energy homeostasis as a rheostat for blood triglyceride, regulating its concentration, in response to external stimuli. In addition it acts as a barometer to inform the central nervous system of energy levels which can vary dramatically between meals and according to energy demand. Here a metabolomic approach, combining both Mass Spectrometry and Nuclear Magnetic Resonance spectroscopy, was used to analyse both white and brown adipose tissue in mice with adipocyte-specific deletion of Arntl (also known as Bmal1), a gene encoding a core molecular clock component. The results are consistent with a peripheral circadian clock playing a central role in metabolic regulation of both brown and white adipose tissue in rodents and show that Arntl induced global changes in both tissues which were distinct for the two types. In particular, anterior subcutaneous white adipose tissue (ASWAT) tissue was effected by a reduction in the degree of unsaturation of fatty acids, while brown adipose tissue (BAT) changes were associated with a reduction in chain length. In addition the aqueous fraction of metabolites in BAT were profoundly affected by Arntl disruption, consistent with the dynamic role of this tissue in maintaining body temperature across the day-night cycle and an upregulation in fatty acid oxidation and citric acid cycle activity to generate heat during the day when rats are inactive (increases in 3-hydroxybutyrate and glutamate), and increased synthesis and storage of lipids during the night when rats feed more (increased concentrations of glycerol, choline and glycerophosphocholine).
Eiden M, Koulman A, Hatunic M, et al., 2015, Mechanistic insights revealed by lipid profiling in monogenic insulin resistance syndromes, Genome Medicine, Vol: 7, ISSN: 1756-994X
BackgroundEvidence from several recent metabolomic studies suggests that increased concentrations of triacylglycerols with shorter (14–16 carbon atoms), saturated fatty acids are associated with insulin resistance and the risk of type 2 diabetes. Although causality cannot be inferred from association studies, patients in whom the primary cause of insulin resistance can be genetically defined offer unique opportunities to address this challenge.MethodsWe compared metabolite profiles in patients with congenital lipodystrophy or loss-of-function insulin resistance (INSR gene) mutations with healthy controls.ResultsThe absence of significant differences in triacylglycerol species in the INSR group suggest that changes previously observed in epidemiological studies are not purely a consequence of insulin resistance. The presence of triacylglycerols with lower carbon numbers and high saturation in patients with lipodystrophy suggests that these metabolite changes may be associated with primary adipose tissue dysfunction. The observed pattern of triacylglycerol species is indicative of increased de novo lipogenesis in the liver. To test this we investigated the distribution of these triacylglycerols in lipoprotein fractions using size exclusion chromatography prior to mass spectrometry. This associated these triacylglycerols with very low-density lipoprotein particles, and hence release of triacylglycerols into the blood from the liver. To test further the hepatic origin of these triacylglycerols we induced de novo lipogenesis in the mouse, comparing ob/ob and wild-type mice on a chow or high fat diet, confirming that de novo lipogenesis induced an increase in relatively shorter, more saturated fatty acids.ConclusionsOverall, these studies highlight hepatic de novo lipogenesis in the pathogenesis of metabolic dyslipidaemia in states where energy intake exceeds the capacity of adipose tissue.
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