A LIPID BLOG
An occasional series of notes on publications or other items dealing with lipid science that seem to be of particular interest to the Editor-in-Chief, Bill Christie. Inevitably, the selection is highly personal and subjective.
May 16th, 2012
The journal Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids has just published a substantial special issue (Volume 1821, Issue 5, pp. 719-876) dealing with the topic of ‘Triglyceride Metabolism and Disease’ and edited by Ira J. Goldberg.
An earlier review from the same journal discusses the signalling properties of lysophosphatidylinositol, which has functions in relation to cell proliferation, migration, survival and tumorigenesis (Pineiro, R. and Falasca, M. Lysophosphatidylinositol signalling: new wine from an old bottle. Biochim. Biophys. Acta, 1821, 694-705 (2012); DOI: 10.1016/j.bbalip.2012.01.009). It is only two weeks ago that I highlighted a similar article on the properties of lysophosphatidylserine.
I have also found a new review on the endocannabinoids such as anandamide that has the virtues of both brevity and being open access (Battista, N. et al. The endocannabinoid system: an overview. Frontiers Behavioral Neurosci., 6, 9 (2012); DOI: 10.3389/fnbeh.2012.00009). I take issue with one statement, i.e. “they mimic the action of Δ9-tetrahydrocannabinol (THC) in different biological processes”. Should we not by now be reversing this statement – “the cannabinol derivatives mimic the effects of anandamide and related compounds, etc”? A further review on anandamide discusses how the molecule is shuttled between the various intracellular compartments (Fowler, C.J. Anandamide uptake explained? Trends Pharmacol. Sci., 33, 181-185 (2012); DOI: 10.1016/j.tips.2012.01.001).
The popular science site Science Daily News has a fascinating story with appropriate links with an amazing colour picture which demonstrates how the cell membrane in yeast is divided into different domains according to the proteins they contain and the specific lipids associated with them - www.sciencedaily.com/releases/2012/05/120504135808.htm
May 10th, 2012
I am pleased to announce that Professors John L. Harwood and Randall Weselake are the new joint Editors-in Chief of the AOCS Lipid Library. Both are eminent scientists and they will bring fresh energy and imagination to the site. We can all look forward to its further development.
May 9th, 2012
In this blog, I suppose that I tend to emphasize ‘high-tech’ methodology as this is where the most obvious new developments are seen. However, I was impressed by the separations illustrated in a new paper on gas chromatography of fatty acid methyl esters. The liquid phase was a new ionic liquid, SLB-IL111, and the column was 200 m long, perhaps not for everyday use. However, the separations of positional isomers especially are impressive (Delmonte, P. et al. Evaluation of highly polar ionic liquid gas chromatographic column for the determination of the fatty acids in milk fat. J. Chromatogr. A, 1233, 137-146 (2012); DOI: 10.1016/j.chroma.2012.02.012). If I could make one plea to those active in this field – please do not stick to methyl esters alone – why not try isopropyl esters, for example, which can be very useful for separation of polyunsaturated fatty acids and have better mass spectrometric properties.
A review paper of particular interest summarises the methodology used for regiospecific analysis of triacylglycerols, including using silver-ion HPLC, reversed-phase-HPLC, and high-resolution gas-liquid chromatography, with and without mass spectrometry (Kalo, P.J. and Kemppinen, A. Regiospecific analysis of TAGs using chromatography, MS, and chromatography-MS. Eur. J. Lipid Sci. Technol., 114, 399-411 (2012); DOI: 10.1002/ejlt.201100367). The only item I would fault is my old complaint of excessive use of abbreviations in the title.
The third methodology paper to catch my eye this week is best suited to those with deep pockets and reviews mass spectrometry with atmospheric pressure photoionization (Gaudin, M. et al. Atmospheric pressure photoionization as a powerful tool for large-scale lipidomic studies. J. Am. Soc. Mass Spectrom., 23, 869-879 (2012); DOI: 10.1007/s13361-012-0341-y). It appears to be especially useful for polar lipids.
May 2nd, 2012
I
have found two interesting papers on lipids as news items in the popular scientific press.
A new paper from the laboratory of Professor Charles Serhan provides evidence that the anti-inflammatory mediators resolvins
and protectins reduce the requirement for antibiotics to fight infections (Chiang
et al. Infection regulates pro-resolving mediators that lower antibiotic requirements.
Nature, 484, 524–528 (2012);
DOI: 10.1038/nature11042).
The second of these papers deals with how ceramides in skin are arranged to provide such a good barrier to water.
It appears that rather than the two tails of the molecule pointing in the same direction as in a typical bilayer,
they are splayed outwards so that they point in opposite directions (Iwai, I.
et al. The human skin barrier is organized as stacked bilayers of fully extended ceramides
with cholesterol molecules associated with the ceramide sphingoid moiety. J. Invest. Dermatol.
DOI: 10.1038/jid.2012.43 (open access)).
I have commented before that the French journal Oléagineux, Corps Gras, Lipides (http://www.revue-ocl.fr/) does not seem to be cited as often as it should be, possibly because it is not covered by abstracting services. The first issue of 2012 deals with ‘green chemistry of oils and fats’ and the second with their ‘nutritional and functional properties’. All the articles are open access and some are in English.
I sometimes disagree about the definition of what constitutes a lipid with the LipidMaps website, particularly with some of the polyketide metabolites, but I always find their article - ‘Lipid of the Month’ to be of great interest. This month is no exception with vitamin K as the subject.
April 25th, 2012
For 30 years, lipid biochemists have been aware that lysophosphatidylserine, like other lysophospholipids, has distinctive biological properties, but we only now beginning to understand the full range of these. A new review discusses the role of this lipid in relation to the resolution of inflammation (Frasch, S.C. and Bratton, D.L. Emerging roles for lysophosphatidylserine in resolution of inflammation. Prog. Lipid Res., 51, 199–207 (2012); DOI: 10.1016/j.plipres.2012.03.001).
The British Journal of Pharmacology has a special themed section in its April issue dealing with “Cannabinoids in Biology and Medicine, Part II” (with guest Editors: Itai Bab and Steve Alexander). The range of new activities reported for endocannabinoid lipids, such as anandamide and 2-arachidonoylglycerol, continues to surprise me.
AOCS will shortly be making an announcement on the new editors for the Lipid Library. I have been retired from active research for a long time now and I don't get to scientific conferences any longer, so I am happy that others are willing to take forward the future development of the site. It will surely go from strength to strength. My ambition for the site has grown with the years, and I hope it will become the first port of call for all who wish to learn something of lipid science. It may never be encyclopaedic in its coverage, but it will hopefully always give plentiful background information together with pointers for those who require more specialist knowledge. I would like to reassure the many friends I have made as a consequence of my work on the Lipid Library, not least through this blog, that I will remain active as Technical Editor and that I will continue to update my own web pages for the foreseeable future.
April 18th, 2012
A news item on a popular science website reports that studies of the relevant genes suggests that about 300,000 years ago humans developed modified enzymes for more efficient elongation and desaturation to produce long-chain polyunsaturated fatty acids from the C18 precursors. This did not occur with our primate relatives. The more efficient enzymes may have enabled more rapid brain development in early man, and it is possible to speculate endlessly on the evolutionary implications. Aren’t lipids wonderful?
The journal Biochimica et Biophysica Acta (BBA) – Biomembranes has a special issue (Volume 1818, Issue 4, Pages 925-1122) on the topic of ‘Protein Folding in Membranes’. Most of the articles are of more interest to protein biochemists than those of us with an interest in lipids, but I did find two of special interest to me at least – one dealing with ‘the role of lipids in protein lipid folding’ and the other with ‘recognition of polyunsaturated acyl chains in membranes’.
April 11th, 2012
I have the impression that much of what is written regarding the function of ether lipids, i.e. phospholipids with an ether linked alkyl moiety in position sn-1, is largely speculative. It has been suggested for example that they may have an antioxidant function (plasmalogens especially) or that they may provide a particular pool of polyunsaturated fatty acids for eicosanoid production. A recent paper shows that the hydrolysis products of ether lipids alkylglycerophosphates, produced in peroxisomes, are required to stimulate the immune system in the thymus (Facciotti, F. et al. Peroxisome-derived lipids are self antigens that stimulate invariant natural killer T cells in the thymus. Nature Immunology, in press: DOI: 10.1038/ni.2245).
Cardiolipin is a fascinating molecule, which has been termed the 'signature lipid' of the mitochondrion in that its presence in the membranes of an organelle identifies that organelle as a mitochondrion. Much recent research has focused on the enzymes that remodel the fatty acid components of the newly formed lipid to give the functional molecule with its relatively simple symmetrical structure. Tafazzin has been of particular interest, because of its involvement in Barth’s syndrome, but at least two other enzyme systems are involved. It has long been known that cardiolipin is an essential component of the complex of enzymes involved in energy production in mitochondria, but the range of known functions is expanding all the time. I can recommend two recent review for those who require more detailed information (Claypool, S.M. and Koehler, C.M. The complexity of cardiolipin in health and disease. Trends Biochem. Sci., 37, 32-41 (2012) (DOI: 10.1016/j.tibs.2011.09.003); Osman, C. et al. Making heads or tails of phospholipids in mitochondria. J. Cell Biol., 192, 7-16 (2011) (DOI: 10.1083/jcb.201006159).
April 4th, 2012
The
endocannabinoid lipids
anandamide and
2-arachidonoylglycerol are of great interest from any number of standpoints.
The journal Neuroscience
(Vol. 204, Issue 1) is devoted to the topic of ‘Stress, Emotional Behavior
and the Endocannabinoid System’ (edited by Matthew Hill).
We are close to the centenary of the identification of vitamin A. I have just found an interesting and substantial review paper in an open access journal that I had not come across previously (D'Ambrosio, D.N. et al. Vitamin A metabolism: an update. Nutrients, 3, 63-103 (2011); DOI: 10.3390/nu3010063). Of course, it is not concerned simply with one molecule but encompasses the whole retinoid family - retinyl esters, retinol, retinal, retinoic acid and oxidized and conjugated metabolites of both retinol and retinoic acid. The authors point out that more than 500 genes are now known to be regulated by retinoic acid, for example.
Why does the fungus Aspergillus fumigatus produce eicosanoids (Kupfahl, C. et al. Production of prostaglandins, isoprostanes and thromboxane by Aspergillus fumigatus: Identification by gas chromatography-tandem mass spectrometry and quantification by enzyme immunoassay. Mol. Immunol., 49, 621-627 (2012); DOI: 10.1016/j.molimm.2011.10.010)? Whatever the explanation it must have implications for the progress of infections in humans by this organism.
March 28th, 2012
A few years ago, my little grand-daughter asked me why I had a ‘space’ in my hair at the back of my head. I found an explanation that amused if it did not convince her. Now I find that it is all due to lipids. It appears that excessive amounts of prostaglandin D2 its derivative, 15-dPGJ2, in the scalp inhibit hair growth via interaction with a specific receptor distinct from the prostaglandin D2 receptor 1 (Garza, L.A. et al. Hair loss prostaglandin D2 inhibits hair growth and is elevated in bald scalp of men with androgenetic alopecia. Science Translational Medicine, 4, 126-134 (2012); DOI: 10.1126/scitranslmed.3003122). It is hoped that this will lead to new treatments. The popular scientific press also carried stories this week that trans fatty acids promote aggression, while conjugated linoleic acid ameliorates the symptoms of Crohn’s disease. Is there anything lipids can’t do?
In the early days of prostaglandin research (around 1968), I attended a lipid conference in which an eminent speaker described prostaglandins as ‘drugs in search of a disease’. Those days have long gone, and I can recommend a readable open-access account of the progress by an Nobel prize winner (Samuelsson, B. Role of basic science in the development of new medicines: examples from the eicosanoid field. J. Biol. Chem., 287, 10070-10080 (2012); DOI: 10.1074/jbc.X112.351437).
The journal Biochimie (Vol. 94, Issue 1) has a special section entitled ‘Lipids in all their states’ (Groupe d'Etudes et de Recherches en Lipidomique (Anglet-Biarritz, France) and edited by Erick J. Dufourc).
March 21st, 2012
Arsenic-containing lipids (‘arsenolipids’) have been an enigma for many years. Their presence in fish oils and lipids from other marine organisms was inferred from the presence of arsenical components in lipid hydrolysis products, but the methods available were insufficiently sensitive to permit definitive identification of the intact lipids. Nonetheless, it was possible to say with reasonable confidence that arsenical analogues of phosphatidylcholine and sphingomyelin were present, together with a fairly well characterized arseno-glycophospholipid. Nor was it known where these compounds arose in the marine food chain. It was as recently as 2008, before hydrocarbons with terminal arsinoyl moieties were identified unequivocally in fish oils followed shortly thereafter by structurally related fatty acids. A new review gives a comprehensive account of what is known on the topic (Sele, V. et al. Arsenolipids in marine oils and fats: A review of occurrence, chemistry and future research needs. Food Chem., 133, 618–630 (2012); DOI: 10.1016/j.foodchem.2012.02.004).
Almost simultaneously a paper has been published in which the intact arseno-glycophospholipid has been fully characterized by mass spectrometry as a component of brown algae (Garcia-Salgado, S. et al. Arsenosugar phospholipids and arsenic hydrocarbons in two species of brown macroalgae. Environm. Chem., 9, 63-66 (2012); (DOI: 10.1071/EN11164). This work seems also to establish that these organisms may be the primary source of the arsenolipids found in fish. Happily, it has been determined that such lipids do not pose problems of toxicity towards humans, as they are rapidly converted to water-soluble organic metabolites and excreted (Francesconi, K.A. Arsenic species in seafood: Origin and human health implications. Pure Appl. Chem., 82, 373-381 (2010); DOI: 10.1351/PAC-CON-09-07-01). These new findings have prompted me to produce a short document on arsenolipids in the 'About Lipids' pages of this website.
March 14th, 2012
Two special issues of journals caught my eye this week. The first is Current Opinion in Clinical Nutrition & Metabolic Care (Vol. 15, Issue 2), which has the theme - Lipid Metabolism and Therapy (edited by Philip C. Calder and Richard J. Deckelbaum). One article especially caught my eye and reinforced my desire to steer clear of nutritional topics (Fernandez, M.L. Rethinking dietary cholesterol. Curr. Opin. Clin. Nutr. Metabol. Care, 15, 117-121 (2012); DOI: 10.1097/MCO.0b013e32834d2259). Contrary to the popular view and some formal recommendations, the author suggests that there is little need for concern about our dietary intake of cholesterol. In the small proportion of the population who are more sensitive to dietary cholesterol, both LDL and HDL cholesterol rise, but the LDL/HDL cholesterol ratio, a key marker of CHD risk, remains constant.
The other special issue is of BBA Biomembranes (Vol. 1818, Issue 2) with the theme ‘Membrane protein structure and function’ (edited by T.W. Allen and F. Separovic). Again, the particular paper to catch my eye deals with sterols (Olsen, B.N. et al. Side-chain oxysterols: From cells to membranes to molecules. Biochim. Biophys. Acta, 1818, 330-336 (2012); DOI: 10.1016/j.bbamem.2011.06.014). The authors discuss how oxysterols regulate cholesterol homeostasis via membrane-mediated mechanisms. They propose that there are two pools of cholesterol in membranes, one that is tightly bound and another that is relatively mobile. Oxysterols may promote the movement of cholesterol from membranes by shifting it from the low to the high activity pools.
March 7th, 2012
For
some time, I have been puzzling what to do about an important error in nomenclature in the lipid literature
in general and this website in particular. A correspondent recently reminded me of the problem.
The fatty acid derivatives we call ‘picolinyl esters’ should in fact be
termed ‘nicotinyl esters’.
Picolinyl alcohol is in fact 2-(hydroxy-methyl)pyridine while nicotinyl alcohol is 3-(hydroxy-methyl)pyridine or 3-pyridylcarbinol,
and it is the latter which is used for derivative preparation.
The error stems from the very first paper on the subject in which ’2- and 3-picolinyl alcohols’ were compared
and the second found best for mass spectrometry purposes; ‘3-picolinyl alcohol’ became simply ‘picolinyl alcohol’
and the error has been perpetuated since.
My dilemma has been that there are at least 160 refereed publications that have used the incorrect term over the last 30 years
(see our literature survey page on the topic), and changing now could cause appreciable confusion.
On the other hand, it has to be done sooner or later by someone and I feel that I should not procrastinate further.
It cannot be done rapidly but over the next few weeks,
I propose to introduce the correct nomenclature to the mass spectrometry web pages here,
although I cannot ditch the erroneous nomenclature immediately.
To lessen confusion, it might be best to use a more systematic nomenclature, e.g.
3-pyridylcarbinol esters.
A new open access journal dealing with lipidomics has been brought to my attention - Journal of Glycomics and Lipidomics.
February 29th, 2012
The Journal of Psychopharmacology has a special issue devoted to endocannabinoids (Volume 16, Issue 1 (2012). There are a number of interesting reviews on biodiesel in Renewable and Sustainable Energy Reviews, including Hoekman, S.K et al. Review of biodiesel composition, properties, and specifications. RSEV, 16, 143-169 (2012); DOI: 10.1016/j.rser.2011.07.143).
There are three fascinating papers on mass spectrometry of lipids in the first issue of the year of the Journal of Mass Spectrometry. For example, the great sensitivity of the newer methodology is illustrated by a lipidomic analysis of single oocytes from mice (Ferreira, C.R. et al. Single oocyte and single embryo lipid analysis by desorption electrospray ionization mass spectrometry. J. Mass Spectrom., 47, 29-33 (2012); DOI: 10.1002/jms.2022).
The possibilities in terms of structural analysis can be seen from a paper in which glycosyldiacylglycerols (GalGlcDAG and GlcDAG) are characterised including the nature and order of the carbohydrate moieties and the structures, including double bond positions, of the fatty acids and their positional distributions on the glycerol moiety (Tatituri, R.V.V. et al. Structural elucidation of diglycosyl diacylglycerol and monoglycosyl diacylglycerol from Streptococcus pneumoniae by multiple-stage linear ion-trap mass spectrometry with electrospray ionization. J. Mass Spectrom., 47, 115-123 (2012); DOI: 10.1002/jms.2033). This organism is of course a major cause of pneumonia in humans and it is known that the glycolipids and the nature and positional distributions of their fatty acid constituents are important for recognition by killer T-cells.
Past items are archived for about a year here..
James Hutton Institute (and Mylnefield Lipid Analysis), Invergowrie, Dundee (DD2 5DA), Scotland. |
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