Biomedical subjects
R G Ackman
Publications and source records attributed to R G Ackman.
Nervonic acid versus tricosanoic acid as internal standards in quantitative gas chromatographic analyses of fish oil longer-chain n-3 polyunsaturated fatty acid methyl esters.
Tricosanoic acid (23:0) and cis-15-tetracosenoic acid (nervonic acid, 24:1 n-9) were compared as choices suitable for use as internal standards in the quantitation of eicosapentaenoic (EPA) and docosahexaenoic (DHA) fatty acids. Experiments conducted included: (a) comparison of the flame ionisation detector responses of the two fatty acid methyl esters; (b) estimation of accurately weighed quantities of EPA and DHA using both 23:0 and 24:1 separately as internal standard; (c) determination of EPA and DHA contents of commercially available fish oil ethyl ester capsules using the two as internal standard. The results suggest that both 23:0 and 24:1 methyl esters behaved similarly in the flame ionization detector of the gas chromatograph and are comparable internal standards for use in quantitation of EPA and DHA. This includes the analysis of ethyl ester mixtures as long as interesterification of sample with solvent methanol is complete. The relatively poor solubility of the saturated 23:0 is countered by its greater stability. A possible drawback of 24:1 could be the presence of more than one positional isomer in either a 24:1n-9 standard or in the actual sample. In principle any fatty acid could serve as an internal standard as long as the limitations involved in the use of each are taken into account.
Novel branched-chain fatty acids in certain fish oils.
Methyl-branched fatty acids, which are usually minor components (equal or less than 0.1%) in fish oils, were concentrated in the non-urea-complexing fraction along with polyunsaturated fatty acids during the enrichment of omega-3 fatty acids from certain fish oils via the urea complexation process. The methyl-branched fatty acids in the omega-3 polyunsaturated fatty acid concentrates, which were prepared from three fish body oils, were characterized by gas chromatography and gas chromatography/mass spectrometry. Among the major branched-chain fatty acids expected and identified were the known isoprenoid acids--mainly 4,8,12-trimethyltridecanoic, pristanic, and phytanic--and the well-known iso and anteiso structures. Two novel phytol-derived multimethyl-branched fatty acids, 2,2,6,10,14-pentamethylpentadecanoic and 2,3,7,11,15-pentamethylhexadecanoic, were identified in redfish (Sebastes sp.) oil. These two fatty acids were absent in oils from menhaden (Brevoortia tyrannus) and Pacific salmon (mixed, but mostly from sockeye, Oncorhynchus nerka). The major branched-chain fatty acid in the salmon oil, 7-methyl-7-hexadecenoic acid, was also present to a moderate extent in menhaden oil. A novel vicinal dimethyl-branched fatty acid, 7,8-dimethyl-7-hexadecenoic was detected in all of the fish oils examined, but was most important in the salmon oil. Three monomethyl-branched fatty acids, 11-methyltetradecanoic acid, and 11- and 13-methylhexadecanoic, hitherto undescribed in fish lipids, were also detected in salmon, redfish and menhaden oils.
Birthweights in the Faroe Islands: possible role of isovaleric acid.
A high intake of n-3 polyunsaturated fatty acids has been suggested as a factor in prolonged gestation in the population of the Faroe Islands. It is now suggested that isovaleric acid from pilot whales, a species frequently consumed in the Faroe Islands, may be the unusual dietary factor. Fatty acid data for eicosapentaenoic acid (EPA) and docosahexanoic acid (DHA) in blood lipids of Faroese and Norwegians is reviewed in terms of the type of fish eaten, apparently mostly lean white fish with DHA much greater than EPA. The popular lean fish, thus, probably provides too little EPA to produce a marked effect on human biochemistry.
Omega-3 fatty acid levels and general performance of commercial broilers fed practical levels of redfish meal.
A total of 1,200 day-old Arbor Acre broiler chickens was randomly assigned to 12 pens (50 males and 50 females/pen) and divided into three blocks of four pens each. Each of four different diets was fed ad libitum to one pen of birds within each block to determine the effect of feeding practical levels of redfish meal (RFM) on performance and omega-3 fatty acid content of edible meat and skin lipids of broiler chickens. The four diets included (control) 0%, 4.0%, 8.0%, and 12.0% RFM. Feeding diets containing RFM had no effect on overall mortality or feed efficiency but resulted in decreased incidence of sudden death syndrome and lower body weight (P less than .01) and feed consumption (P less than .05). Additions of RFM to the diets resulted in a substantial dietary enrichment of omega-3 fatty acids (especially eicosapentaenoic acid, EPA or 20:5n-3, and docosahexaenoic acid, DHA or 22:6n-3). Analyses (wt/wt%) revealed that breast meat (less skin) was lower (P less than .001) in lipid and triglyceride but higher in free cholesterol (P less than .001) and phospholipid (P less than .001) than thigh meat (less skin). Dietary treatment had no effect on carcass lipid content or composition. Breast meat lipid contained more (P less than .001) omega-3 fatty acids (especially EPA and DHA), more docosapentaenoic acid, (DPA or 22:5n-3) and more total omega-3 polyunsaturated acids (n-3 PUFA) than thigh meat lipids. Feeding additional RFM resulted in an increased (P less than .001) accumulation of EPA, DPA, DHA, and total n-3 PUFA primarily at the expense of two omega-6 fatty acids, linoleic (18:2n-6) and arachidonic acid (20:4n-6). It can be calculated from the data presented that the consumption of 100 g of chicken that has been fed 12.0% RFM would contribute approximately 197 mg of omega-3 fatty acids (EPA + DPA + DHA) in contrast with the 138 mg of omega-3 fatty acids which would be realized from the consumption of 100 g of white fish such as cod.
Nutritional composition of fats in seafoods.
Public interest in the health benefits of seafood lipids, or of fish oils, is a most unusual phenomenon because for once the recommendations of health authorities to "eat more fish" are in accord with newer and popular attitudes. Media exploitation of the more sensational health aspects is also generally in favor of more consumption of seafood. The public is however still confused by the multitude of species of fish and shellfish available, and in a quandary over whether fatty fish are risky in terms of calories or cholesterol, or of more benefit than lean fish in terms of omega-3 fatty acids. Most direct questions on how much omega-3 fatty acids are useful in the diet of an average individual may never be answerable until long term studies with humans are carried out. It does appear that marine fish can be broken down into four convenient categories: lean (including shellfish), low fat, medium fat and high fat; and in this review it is suggested that these could contribute, per 100 grams, respectively about 250, 750, 1000 and 2000 mg of total C20 + C22 omega-3 fatty acids. This intake can compare favorably with the alternative of commonly available fish oil capsules. Moreover this survey shows that at present the composite of total omega-3 fatty acids in fish and shellfish may contain roughly equal proportions of the functionally effective eicosapentaenoic acid, and of docosahexaenoic acid with its as yet unknown long-term biochemical effects, or be biased in favor of more of the latter. To assist the public, nutritionists, dietitians, and researchers this review discusses the distribution of fat in edible fish muscle, the classes of lipids encountered, and the major fatty acids of health interest. Included are limited numbers of analyses from parts of the world other than North America.
Absorption and transport of fat in mammals with emphasis on n-3 polyunsaturated fatty acids.
The current state of knowledge concerning the absorption and transport of dietary fat with emphasis on long-chain polyunsaturated n-3 fatty acids in mammals is reviewed. It is apparent that long-chain polyunsaturated n-3 fatty acids, either as free acids or as part of triglycerides, are readily absorbed in the gut and transported by the circulatory system. Indeed, it would appear that long-chain polyunsaturated n-3 fatty acids are digested, absorbed and transported similarly to other long-chain fatty acids with only minor variations, although there is much that is still not understood about these processes. The main unresolved issues in the area of the absorption and transport of long-chain polyunsaturated n-3 fatty acids appear to be: 1) If they, when located in the 2-position of triglycerides, have unique metabolic pathways; and 2) whether the unnatural forms, i.e., methyl or ethyl ester derivatives, are suitable vehicles for administration as dietary supplements. The effect in man of dietary, long-chain polyunsaturated n-3 fatty acids on blood serum lipid and lipoprotein levels, particularly the low density lipoproteins, remains controversial, except for the well-documented reduction in serum triglyceride levels. Also, there is uncertainty regarding their distribution and metabolism in tissues. Finally, if the consumption of long-chain polyunsaturated n-3 fatty acids has beneficial health consequences, what is the appropriate therapeutic dose? In view of these important, unresolved issues and uncertainties, it would seem prudent to direct additional research toward a better understanding of the overall process by which fat is digested, absorbed and transported.
Some possible effects on lipid biochemistry of differences in the distribution on glycerol of long-chain n-3 fatty acids in the fats of marine fish and marine mammals.
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Fatty acid components of larval Ostrea edulis (L.): importance of triacylglycerols as a fatty acid reserve.
1. The fatty acid profiles of all of the acyl-lipid classes of 1- and 10-day-old European oyster Ostrea edulis (L.) larvae were studied in detail by capillary gas-liquid chromatography. 2. No significant changes in the fatty acids were detected between the different larval stages. 3. Total lipid fatty acids showed a higher degree of unsaturation than previously reported. This may be a consequence of the extraction of lipids from the living tissues without sample storage. 4. One-third of the triacylglycerol fatty acids were polyunsaturated. In agreement with the importance of triacylglycerols in lipids of bivalve larvae, it is suggested that this lipid fraction may act as a temporary reservoir of physiologically-important polyunsaturated fatty acids. 5. Free fatty acids and fatty acids from the minor lipid classes are discussed in terms of their possible origin and physiological significances.
Ingestion of fish oil or a derived n-3 fatty acid concentrate containing eicosapentaenoic acid (EPA) affects fatty acid compositions of individual phospholipids of rat brain, sciatic nerve and retina.
The effect of feeding redfish (Sebastes marinus or mantella) oil or a derived n-3 fatty acid concentrate containing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on the fatty acid compositions of individual phospholipids in selected neural tissues was studied in growing male rats. Control animals were given sunflower oil in the diet for the 5-wk feeding trial. Lipid analyses revealed that EPA (20:5n-3) became significantly enriched in all phospholipid fractions (phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol) in the tissues studied (brain, retina and sciatic nerve) in the two n-3 fatty acid dietary groups relative to controls. Corresponding changes were also found in the 22:5n-3 contents of these tissues, whereas little or no significant elevation in DHA (22:6n-3) was found. In contrast, the percentages by weight of the n-6 fatty acids including 18:2n-6, 20:4n-6 (arachidonic acid, AA), 22:4n-6 and 22:5n-6 were generally lower in the various phospholipids/tissues of the animals given fish oil or the n-3 fatty acid concentrate; the levels of 22:5n-6 and 22:4n-6 were markedly affected in this regard. These results indicate that dietary n-3 fatty acids (as EPA plus DHA) can greatly affect the fatty acid compositions of the various membrane phospholipids in nervous tissues within a relatively short time. These biochemical alterations may be important for functional changes including altered membrane fluidity, cellular responses, ion transport and the biosyntheses of AA- and EPA-derived prostaglandins and leukotrienes.
Simplification of analyses of fatty acids in fish lipids and related lipid samples.
The longer chain, highly unsaturated fatty acids up to 22:6 and typical of fish lipids must be included in many current analyses of fatty acids of diets, blood, and eventually of organ lipids. The use of the GLC liquid phase Carbowax-20M in a bonded, or cross-linked form, wall-coated in glass or flexible fused silica capillary columns, eliminates the confusing overlap of component fatty acids of different chain lengths found with polar packed GLC columns. Either isothermal or programmed conditions yield comparable results illustrated with a fish oil analysis.
Comparison of fatty acids and lipids of smolting hatchery-fed and wild Atlantic salmon Salmo salar.
In Atlantic Canada the Atlantic salmon Salmo salar change from the parr stage to the smolt stage while still in fresh water, preparatory to migration to salt water. In some stocks this takes place during the second overwintering. In several hatcheries where the water temperature drops to 0-0.5 C and the ponds ice over, there is a high incidence of erosion of the dorsal and pectoral fins and sometimes of the caudal fin. No disease organism has been identified, and the lesions heal over in most cases. Dietary fatty acids were thought to be a factor. A detailed study of lipid recoveries and classes has shown that in the skins of abnormal fish the total lipid is 7.8% compared to 4.7% in control fish. Unexpectedly, an analysis of one lot of healthy smoltstage wild fish showed that whole bodies have only a quarter of the lipid of comparable hatchery fish. Comparison of fatty acids showed that wild fish lipids include a higher proportion of arachidonic acid than those of the hatchery fish. In the latter, linoleic acid is provided readily by diet but the elongation to arachidonic acid evidently does not proceed. These results suggest that the smolt lipid is involved intimately with either the cause of the dermal lesion or is a defense mechanism, possibly mediated through oxygenase activity.
Serum lipid abnormalities in a chemical/viral mouse model for Reye's syndrome.
Neonatal mice given nontoxic dermal applications of an industrial surfactant, Toximul MP8 (Tox), and subsequently infected with sublethal doses of mouse-adapted human Influenza B (Lee) virus (FluB) develop many of the biochemical features of Reye's Syndrome (RS). To determine whether these also include abnormal circulating lipid, we examined serum lipid profiles in the mouse model throughout the treatment course using Iatroscan-TH10. Following 10 days of exposure to surfactant, serum phospholipid and cholesterol levels were significantly reduced relative to control animals. These reductions were transient; however, four days following virus administration, significant differences in serum lipid were again evident. These abnormalities coincided and correlated with increased animal mortality. Animals that received combined Tox + virus treatment had significant decreases in serum total lipids relative to control animals, a reflection of a reduction in all lipid classes, including phospholipid, cholesterol, neutral glycerides (triglycerides plus diglycerides) and free fatty acids. Phospholipid (specifically phosphatidylcholine and lysophosphatidylcholine) and free fatty acid levels in the Tox + virus group were also significantly lower than those in animals that received virus alone. This study has demonstrated that suckling mice given chemical/viral treatment have the serum hypopanlipidemia but not the freefattyacidemia that are characteristic of RS.
Mass spectra of fatty acid derivatives, of isopropylidenes of novel glyceryl ethers of cod muscle and of phenolic acetates obtained with the Finnigan MAT Ion Trap Detector.
The applicability of the Finnigan MAT Ion Trap Detector (ITD) mass spectrometer for structure determination in some selected fatty acids and their derivatives has been investigated. Isopropylidene derivatives of novel glyceryl ethers isolated from cod flesh and of phenolic acetates are included to indicate the potential for diverse structures and to clarify the protonation of ions. The ITD is a simple and unsophisticated gas liquid chromatograph-mass spectrometer, but the spectra obtained are in most respects comparable to those from more conventional electron impact mass spectrometers. However, due to the comparatively high background pressure (approximately 10(-3) torr) in the ionization chamber of the ITD, there is a tendency for both neutral and ionized molecules to acquire protons from other molecules or fragments through collision. In many cases, the molecular ion was observed as the protonated molecular ion (M + 1), as in chemical ionization mass spectrometry. These interactions can be minimized if the sample load is decreased. Phenolic acetates exhibit not only protonation of the molecular ion, but also protonation of stable fragmented neutral molecules or ions.
Occurrence of cis-9,10-methylenehexadecanoic and cis-9, 10-methyleneoctadecanoic acids in the lipids of immature and mature Fundulus heteroclitus (L.), and in roe.
Analysis of saturated fatty acids in the mummichog Fundulus heteroclitus (L.) by argentation chromatography and open-tubular gas-liquid chromatography detected cyclopropanoid fatty acids as well as all of the anticipated saturated fatty acids, including a variety of branched-chain saturated fatty acids previously found in fish. Cyclopropanoid fatty acids were identified in juveniles, male and female bodies, and roe. When the levels of these acids in eviscerated male and female bodies were compared with roe, roe had the highest concentration, followed by female and then male fish. Whole immature mummichog had almost twice the proportion of cyclopropanoid fatty acids found in whole mature male fish. The cyclic acids probably originate indirectly in the diet of the mummichog. This consists mainly of invertebrates probably consuming bacteria associated with plant detritus. The Atlantic silversides Menidia menidia collected from the same habitat had lower proportions of odd-chain methyl-branched fatty acids, and lower proportions of cyclopropanoid fatty acids, indicating differences in sources of dietary fatty acids.
Two methods for determining erucic acid in edible fats and oils: results from a collaborative study on a rapid, open-tubular (capillary) GLC method and comparison with an isolation TLC procedure.
The results of an international collaborative study for the determination of 5% erucic acid in four samples of edible fats and oils with differing levels of 22:1 isomers other than erucic acid, based on the use of wall-coated (SILAR-5CP) open-tubular gas-liquid chromatography, are examined. The same samples had been analyzed in a separate collaborative study by an alternative and more complex method based on argentation thin-layer chromatography. Both methods rejected about the same proportion of participating laboratories and a few individual results from otherwise acceptable laboratories. The means and repeatabilities of the two methods were similar, but the gas-liquid chromatographic method showed better reproducibility.
Aortic changes in cynomolgus monkeys fed high-fat diets (long-term study).
Two diets containing either a lard-corn oil mixture (LCO) or partially hydrogenated herring oil (PHHO) were fed to cynomolgus monkeys (Macaca fascicularis) for up to 30 months. Serum cholesterol values rose to 180 mg/dl in the LCO-group and to 260 mg/dl in the PHHO-group. Serum lipoprotein concentrations were normal in the LCO-group, but PHHO-fed monkeys had lower HDL- and higher LDL- and VLDL-proportions. Only one animal on the LCO-diet for 24 months developed a pre-atherosclerotic lesion in the aorta. The general absence of true atherosclerotic lesions in the presence of high serum cholesterol levels and abnormal serum lipoprotein proportions may be interpreted as being indicative of the low atherogenicity of the fats used. This finding points toward a specific fat-animal species interaction.
Flame ionization detection applied to thin-layer chromatography on coated quartz rods.
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