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 Technical Editor, Bill Christie. Inevitably, the selection is highly personal and subjective.
May 22nd, 2013
If I had been asked to cite the first paper to show that lipids had functions other than as a source of energy, I would probably have listed the classic work of Burr and Burr from the 1920s on essential fatty acids (see Smith, W. and Mukhopadhyay, R. Essential Fatty Acids: The Work of George and Mildred Burr. J. Biol. Chem., 287, 35439-35441 (2012); DOI: 10.1074/jbc.O112.000005. However, an editorial in the Journal of Lipid Research (Blaner, W.S. The fat-soluble vitamins 100 years later: where are we now?), just available in manuscript form, suggests that the first to provide evidence of the fat-soluble vitamins 100 years ago may be due this honour (McCollum, E.V. and Davis. M. The necessity of certain lipins in the diet during growth. J. Biol. Chem., 15, 167-175 (1913)). The journal has a series of thematic reviews on the fat-soluble vitamins in the pipeline – something for which to look forward when I return from my annual vacation.
May 15th, 2013
As far as I can ascertain, the first mention of sphingosine-1-phosphate in the scientific literature was in 1970 by Wilhelm Stoffel and colleagues. At the time, this appears to have attracted little notice and another 25 years or so were to pass before the scientific community began to give due attention to this key molecule, which is now understood to have vital roles in health and disease in that it affects cardiac function, vascular development, immune cell function, inflammation, cancer and Alzheimer’s disease. Google scholar suggests that there were 3,600 publications touching on this lipid last year. It is transported in the blood stream in complexation with apolipoprotein M in the HDL, and this complex activates a specific receptor S1P1. Their combined interactions are now seen to be of relevance to atherosclerosis and perhaps other diseases. A new review discusses this aspect of the topic (Arkensteijn, B.W.C. et al. The apolipoprotein M-sphingosine-1-phosphate axis: biological relevance in lipoprotein metabolism, lipid disorders and atherosclerosis. Int. J. Mol. Sci., 14, 4419-4431 (2013); DOI: 10.3390/ijms14034419).
The world is such a beautiful place that I have difficulty in understanding how anyone would wish to change their perception of it with drugs. Indeed, I sometimes get the impression from the popular news media that I am one of the few people left in the world who has not tried cannabis. This exerts its physiological functions by activating specific receptors in cells, the true function of which are important in many aspects of human physiology and are relevant to many disease states. The real endogenous ligands are lipids, and they have been termed ‘endogenous cannabinoids’ or ‘endocannabinoids’, e.g. anandamide and 2-arachidonoylglycerol. As we know more and more about the biochemistry and functions of specific lipids, reviews dealing with them tend to become more specialized and restricted to specific aspects. I find it helpful, therefore, when a more general overview is published that attempts to put developments into a proper perspective. It is not an easy read for non-biochemists, but I can recommend one such (Fonseca, B.M. et al. Endogenous cannabinoids revisited: A biochemistry perspective. Prostaglandins Other Lipid Mediators, 102/103, 13-30 (2013); DOI: 10.1016/j.prostaglandins.2013.02.002).
May 8th, 2013
I have belatedly become aware of a special issue of a new journal Metabolites, the January issue (2012) of which is devoted to the topic of "Lipidomics". There are a number of interesting articles including one on the analysis of glycolipids, and another on the technology of modern mass spectrometric methods. All of these have the additional virtue of being open access.
Another useful set of reviews has been published in the journal Molecular and Cellular Endocrinology (Volume 368, Issues 1–2, Pages 1-128 (10 April 2013)) and deals with the topic of “Nuclear Receptors, Bile Acids and Cholesterol Homeostasis” (edited by Kristina Schoonjans).
May 1st, 2013
I
have a particular interest nowadays in the biological functions of lipids,
but equally interesting is how natural lipids are being used in industrial/commercial applications of various kinds,
especially in health products via the pharmaceutical industry. Two recent reviews in the journal
Biotechnology Advances have caught my eye.
The most recent deals with the potential of bacterial
lipopeptides in the control of infection
and it seems that at least four have reached commercial status.
Others appear to have great promise against the antibiotic resistant strains of bacteria,
which are so troublesome in our hospitals.
Other lipopeptides have applications as surfactants and emulsifiers, and even in cosmetics as anti-wrinkle agents (Mandal, S.M.
et al. Lipopeptides in microbial infection control: Scope and reality for industry.
Biotechnol. Adv., 31, 338-345 (2013);
DOI: 10.1016/j.biotechadv.2013.01.004).
The second review in this journal, published towards the end of last year, deals with the industrial uses of products of lipoxygenases. It seems that “animal lipoxin LXA4, plant jasmonic acids, plant green leaf volatiles, and bacterial lactones have been used as anti-inflammatory agents, anti-pest agents, flavors, and food additives, respectively” (Joo, Y.-C. and Oh, D.-K. Lipoxygenases: Potential starting biocatalysts for the synthesis of signaling compounds. Biotechnol. Adv., 30, 1524-1532 (2012); DOI: 10.1016/j.biotechadv.2012.04.004).
April 25th, 2013
As a school boy, I never appreciated my French teacher – Monsieur Smith (his name corrupted by his pupils to ‘Messerschmitt’ and then simply ‘Mesh’ out of his hearing), but I was grateful to him in later years on my occasional visits to France or when I read a scientific paper in French (reading is infinitely easier than speaking the language for me now). As a Francophone, I have mixed feelings about rarely using these waning skills as so many important French journals now publish in English only, not least Biochimie (Société française de biochimie et biologie moléculaire). The March issue of this journal has an important series of review articles on ‘Oxysterols and Related Sterols in Chemistry, Biology and Medicine’ (edited by Luigi Iuliano and Gérard Lizard – Biochimie, 95, Issue 3, 445-640 (March 2013)). I suppose that we have to be grateful that we have a 'Lingua Franca' for science and that it is English (or American).
The May issue of Biochim. Biophys. Acta - Molecular and Cell Biology of Lipids (Vol. 1831, Issue 5, Pages 895-1008 (May 2013)) is devoted solely to the topic of ‘Brown and White Fat: From Signaling to Disease’ (edited by S. Herzig and C. Wolfrum).
A substantial biography of the late A.T. (Tony) James, who amongst many other achievements in lipid biochemistry was the inventor of gas chromatography, has been published by Mike Gurr (Biogr. Mems. Fell. R. Soc., 58, 129-150 (2012); DOI: 10.1098/rsbm.2011.0018). You can find James' own account of his early work on this site here.
April 17th, 2013
The O-acylated proteolipids have been on my radar for some time, but two recent reviews have raised their profile. The best known is probably ghrelin, which is of particular importance as a hunger-stimulating hormone produced in the human stomach and pancreas, increasing food intake and adiposity. It can be octanoylated at a serine residue and this is essential for binding to its specific receptor. The enzyme that catalyses octanoylation is now a target for pharmaceutical intervention for treatment of the metabolic syndrome. (Romero, A. et al. GOAT: the master switch for the ghrelin system? Eur. J. Endocrinol., 163, 1-8 (2010); DOI: 10.1530/EJE-10-0099).
Secondly, the family of Wnt proteins are central mediators of animal development, influencing cell proliferation, differentiation and migration. They are S-palmitoylated on a conserved cysteine residue, but they have a second unusual O-acyl modification with palmitoleic acid at a conserved serine residue. O-Acylation requires an acyltransferase termed 'Porcupine', which has become a high-priority target for an anticancer drug (Ke, J. et al. Lipid modification in Wnt structure and function. Current Opinion in Lipidology, 24, 129-133 (2013); DOI: 10.1097/MOL.0b013e32835df2bf). I am intrigued as to whether this highly specific function of palmitoleic acid might be related to its role as a lipokine.
The journal CNS & Neurological Disorders - Drug Targets has a new issue devoted largely to the subject of “Palmitoylethanolamide: Biochemistry, Pharmacology and Therapeutic Use of a Pleiotropic Anti-Inflammatory Lipid Mediator”. This issue is open access.
I was fascinated by the title of a new paper in the Journal of Lipid Research (Chaitidis, P. et al. Lipoxygenase pathways in Homo neanderthalensis: functional comparison with Homo sapiens isoforms. J. Lipid Res., 54, 1397-1409 (2013); DOI: 10.1194/jlr.M035626). It is astonishing that we can now study lipid biochemistry in a species that has been extinct for 40,000 years.
April 12th, 2013
The contribution of Margaret Hilda Roberts to lipid chemistry is not widely recognized, probably because she is a co-author of only one scientific paper (Jellinek, H.H.G. and Roberts, M.H. The saponification of α-monostearin in a monolayer. J. Sci. Food Agric., 2, 391–394 (1951); DOI: 10.1002/jsfa.2740020904). Her chemistry career was short and she left it to take a second degree in law before entering politics. She is better known under her married name of Margaret Thatcher. As such she became an iconic figure in the United Kingdom as our first woman Prime Minister and the longest serving one in the 20th century. She was probably our most controversial politician also, and there are many who wish she had stuck to lipid chemistry. Whatever our political convictions, I suspect the world is poorer without her.
April 10th, 2013
A new publication available as yet only in manuscript form suggests a short-hand nomenclature for lipids (Liebisch, G. et al. Shorthand notation for lipid structures derived from mass spectrometry. J. Lipid Res., in press. DOI: 10.1194/jlr.M033506). I believe that abbreviations and acronyms are grossly over-used in the scientific literature; they are a convenience for authors but simply a nuisance for readers. Nevertheless, there are occasions when they are useful, so if they must be used they should at least be standardized. One virtue of those proposed here is that they are simple, PC for phosphatidylcholine, for example, unlike those recommended in an early LIPID MAPS publication. One quibble I do have with the list is that it ignores the common plant lipids.
Shorthand nomenclature for fatty acids is confusing and inconsistent. A correspondent has recently reminded me that the shorthand nomenclature for linoleic acid is ‘18:2’ not ‘C18:2’, and I could add that the IUPAC-IUB recommendation is for ‘18:2(n-6)’ not ‘18:2n-6’, as are frequently found in journals. You will also find in the literature 9c,12c-18:2, Δ9,12-18:2 and 18:2(9Z,12Z) (and probably more). The shorthand nomenclatures in common use for branched-chain fatty acids can even lead to errors in interpretation. It is time that international bodies looked again at these questions and I trust that they will consult more widely that the private consortia appear to have done. I am not hopeful as the last time I looked, the IUPAC web page dealing with lipid nomenclature had misinterpreted its own conclusions.
I am a firm believer in the open access movement for scientific publication, and I am grateful to those journals that may not be fully open but permit access a year or two after formal publication. It is distressing to read that fraudsters are getting into the act with bogus journals and scientific meetings, designed simply to fleece authors. The New York Times has a recent piece on the topic.
April 3rd, 2013
I
have been reading a fascinating review on phosphatidylethanolamine
(Vance, J.E. and Tasseva, G. Formation and function of phosphatidylserine
and phosphatidylethanolamine in mammalian cells. Biochim. Biophys. Acta, 1831, 543-554 (2013);
DOI: 10.1016/j.bbalip.2012.08.016).
The modern science apart, I was entertained by a comment in the introductory section regarding the discovery
of this lipid in 1884 by Ludwig Thudichum.
It appears that during his lifetime his work was considered “relatively insignificant,”
according to Thudichum's obituaries in Nature [volume 64, page 527 (1901)] and “The Times”
of London (Sept. 10, 1901). The latter article stated that “the knowledge yielded by
these researches was hardly commensurate with the time and cost at which it was obtained.”"
The authors comment that “Unfortunately, similar sentiments are even today often applied to basic research”.
This was certainly true in regard to lipids in general during the last century,
when lipid science was often poorly taught in Universities.
Thankfully, the true relevance of lipids to human health and well-being is now being recognized.
As an example, the most recent evidence for the importance of omega-3 fatty acids in human nutrition is the effects of epoxy-docosapentaenoic acid (a metabolite of DHA) on cancer reported in Science Daily News.
March 27th, 2013
How the science of lipidomics impinges on disease states is becoming a recurrent theme in these notes, and a new review offers an interesting perspective on the subject (Tucker, S.C. and Honn, K.V. Emerging targets in lipid-based therapy. Biochem. Pharmacol., 85, 673-688 (2013); DOI: 10.1016/j.bcp.2012.11.028). It seems that a number of enzymes, accessory proteins and receptor molecules involved in lipid metabolism are now targets for therapeutic intervention. In addition, a number of lipid species are considered biomarkers for various disease states.
Similarly, the lipids of lung surfactant are important for health and disease, and the detailed molecular structures of the lipids and their biosynthesis and metabolism are under intensive scrutiny. This is also the topic of a new review (Goss, V. et al. Regulation of lung surfactant phospholipid synthesis and metabolism. Biochim. Biophys. Acta, 1831, 448-458 (2013); DOI: 10.1016/j.bbalip.2012.11.009).
Occasionally, I find reports of some unusual uses for lipids and a recent publication discusses the use of lysophosphatidylethanolamine in a number of horticultural applications. Apparently, when applied exogenously, the claimed “benefits include delayed leaf senescence, stimulation of ripening in table grape, acceleration of color development and extension of shelf-life in cranberry and tomato, and increased vase life of cut flowers”. The mechanism for these effect seems to be obscure as does the role of this lipid in vivo in plants (Amaro, A.L. and Almeida, D.P.F. Lysophosphatidylethanolamine effects on horticultural commodities: A review. Postharvest Biol. Technol., 78, 92-102 (2013): DOI: 10.1016/j.postharvbio.2012.12.011).
March 20th, 2013
The journal Current Opinion in Clinical Nutrition and Metabolic Care (Vol. 16:2) contains eight review articles on the theme of “Lipid metabolism and therapy” (edited by Philip C. Calder and Richard J. Deckelbaum). The main thrust of the articles concerns the effects of omega-3 fatty acids in various disease states.
Defects in lipid metabolism are implicated in Alzheimer’s disease and this is the subject of a new review (open access); it appears that much of the evidence comes from recent lipidomic studies (Wood, P.L. Lipidomics of Alzheimer's disease: current status. Alzheimers Res. Therapy, 4, 5 (2012); DOI: 10.1186/alzrt103). An isoform of apolipoprotein E is a major risk factor, but substantial deficits in brain structural glycerophospholipids and sphingolipids have also been detected together with effects on signalling molecules derived from these.
There is an intriguing report that N-acylethanolamines, including the endocannabinoids, exist in plasma and erythrocytes in esterified form, i.e. the free hydroxyl group as well as the amine moiety is esterified (Balvers, M.G.J. et al. Liquid chromatography-tandem mass spectrometry analysis of free and esterified fatty acid N-acyl ethanolamines in plasma and blood cells. Anal. Biochem., 434, 275-283 (2013); DOI: 10.1016/j.ab.2012.11.008). So far the evidence is indirect, but it will be interesting to learn whether these compounds are inert storage or transport forms, or whether they have biological properties in their own right.
March 13th, 2013
The latest news on fish oils continues to be good for consumers. It seems the docosahexaenoic acid (DHA) interacts very specifically with ion channels with beneficial effects on blood pressure and the cardiovascular system. There is a popular account here..
In 2011, 20 substantial review articles were published under the title ‘The Biology of Lipids’ (edited by Kai Simons) as part of the Cold Spring Harbor Perspectives in Biology series. These have now been made freely available online to all readers.
The Biochemical Society Transactions (Vol. 41 Part 1 of 2013) contains a number of articles dealing with proteolipids or more specifically the theme of “Regulation of protein trafficking and function by palmitoylation” (edited by Luke Chamberlain and Tony Magee).
The term ‘lipid rafts’ is used to describe ordered structures in biological membranes arising from lateral segregation of sphingolipids and cholesterol. These attract specific proteins and other signalling molecules with profound effects on cell biology. I can recommend a new open access review, which summarises current knowledge (Sonnino, S. and Prinetti, A. Membrane domains and the "lipid raft" concept. Curr. Med. Chem., 20, 4-21 (2013); Link here. This issue also contains several other reviews on lipids in membranes.
March 6th, 2013
I always enjoy learning of the experiences of the pioneers of lipid science to understand how their research careers developed and why they went down specific paths. I have just been reading a fascinating autobiographical account of the career of Konrad Sandhoff, one of the pioneers in the study of the complex glycosphingolipids, such as gangliosides. He has been instrumental especially in revealing the roles of these lipids in lysosomal storage diseases as well as many other aspects of sphingolipid biochemistry. It is available in an open access journal (Sandhoff, K. My journey into the world of sphingolipids and sphingolipidoses. Proc. Japan Acad., B. Phys. Biol. Sci., 88, 554-582 (2012); DOI: 10.2183/pjab.88.554). Incidentally, you can find links to many articles of this kind on this website here (please inform me if you know of others).
A correspondent has brought to my attention a paper describing a novel method for the preparative separation of trans- and cis-monoenoic fatty acids using membrane technology rather than chromatography methodology (Gupta, A. and Bowden, N.B. Separation of cis-fatty acids from saturated and trans-fatty acids by nanoporous polydicyclopentadiene membranes. ACS Appl. Mater. Interfaces, 5, 924–933 (2013); DOI: 10.1021/am3025867). The width of the pores in the membrane are such that fatty acids with relatively linear chains can pass through, but the kinked cis-monoenes cannot.
Two weeks ago, I discussed a review paper that suggested that there were no definitive experiments to confirm the supposed benefits of dietary cis-monoenoic fatty acids. Now there is news of a major study (PREDIMED) with 7,500 subjects which finds that a Mediterranean diet supplemented with virgin olive oil and nuts (walnuts, almonds, hazelnuts) reduces the risk of suffering cardiovascular death, myocardial infarction or stroke by 30 percent. The diet has a relatively high fat content, but a significant difference from other studies may be that it does not use a refined oil and has other natural constituents. The report in the website Science Daily News describes the results to non-nutritionists such as myself.
The current controversy about horse meat in the food chain is concerned more with fraud than with nutrition or safety issues. I cannot put my hands on a reference immediately, but I seem to recall that the triacylglycerols of horse fat contain much more linoleic and α-linolenic acids than beef. This is certainly the case in horse milk (Parodi, P.W. Positional distribution of fatty acids in triglycerides from milk of several species of mammals. Lipids, 17, 437-442 (1982) DOI: 10.1007/BF02535223).
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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