A synopsis of the process of lipid peroxidation since the discovery of the essential fatty acids

Eighty years ago, Burr and Burr, introduced for the first time the concept of essential fatty acids. Now is very well known that requirements for polyunsaturated fatty acids PUFAs can not be met by de novo metabolic processes within mammalian tissues. Animals are absolutely dependent on plants for providing the two major precursors of the n-6 and n-3 fatty acids, C18:2n-6; linoleic and C18:3n-3; α-linolenic acids. In animal tissues these precursors are transformed to fatty acids containing three to six double bonds. During the last four decades the interest in polyunsaturated fatty acids has augmented manifolds, and the number of published studies is rising each year. The current impetus for this interest has been mainly the observation that PUFAs and their metabolites have several physiological roles including: energy provision, membrane structure, cell signaling and regulation of gene expression. In addition the observation that PUFAs are targets of lipid peroxidation opens a new important area of investigation. Melatonin, the main secretory product of the pineal gland, efficiently scavenges both the hydroxyl and peroxyl radicals counteracting lipid peroxidation in biological membranes. In addition the two key pineal biochemical functions, lipoxygenation and melatonin synthesis may be synergistically regulated by the status of n-3 essential fatty acids. At the retina level, free radicals may preferentially react with the membrane polyunsaturated fatty acids leading to the release of lipoperoxide radicals. These lipoperoxides can induce oxidative stress linked to membrane lysis, damage to neuronal membranes may be related to alteration of visual function.     

Transient Formation of Superoxide Radicals in Polyunsaturated Fatty Acid-Induced Brain Swelling

The involvement of superoxide free radicals and lipid peroxidation in brain swelling induced by free fatty acids has been studied in brain slices and homogenates. The polyunsaturated fatty acids linoleic acid (18:2), linolenic acid (18:3), arachidonic acid (20:4), and docosahexaenoic acid (22:6) caused brain swelling concomitant with increases in superoxide and membrane lipid peroxidation. Palmitic acid (16:0) and oleic acid (18:1) had no such effect. Furthermore, superoxide formation was stimulated by NADPH and scavenged by the addition of exogenous superoxide dismutase in cortical slice homogenates. These in vitro data support the hypothesis that both superoxide radicals and lipid peroxidation are involved in the mechanism of polyunsaturated fatty acid-induced brain edema.     

Oxygen uptake during the gamma-irradiation of fatty acids

The radiation-induced oxidation of saturated and unsaturated fatty acids in aqueous solutions has been estimated by measurement of the continuous uptake of oxygen using an oxygen electrode. Chain reactions, initiated by HO radicals, are easily identified to be occurring in the case of unsaturated fatty acids. Other mild oxidation agents, namely (SCN)-.2, Br-.2 and N.3, are also found to be capable of oxidizing the polyunsaturated fatty acids. Evidence is presented that O-.2 may also initiate peroxidation. The oxidation of the polyunsaturated fatty acids is dependent on dose rate, fatty acid concentration, temperature and the presence of antioxidant and other protective agents. Kinetic studies of the reaction of (SCN)-.2 and Br-.2 with linoleic and linolenic acids have been carried out using pulse radiolysis. The bimolecular rate constants for both radical species with the lipids are approx 10(7) mol-1 dm3 s-1, below their critical micelle concentrations, and decrease at higher concentrations due to micelle formation.     

Characterization of a Ca2+-stimulated lipid peroxidizing system in the sea urchin egg

Addition of calcium chloride to an egg homogenate of Strongylocentrotus purpuratus stimulates O2 consumption which is not inhibited by millimolar cyanide. Results strongly suggest that Ca2+-stimulated O2 consumption is at least partially the result of polyunsaturated fatty acid oxidation. First, addition of arachidonic acid (AA), or other polyunsaturated fatty acids, to the homogenate enhance Ca2+-stimulated O2 consumption; this enhancement, by AA, being coupled to its oxidation to a hydroxy fatty acid. Second, calcium stimulates a lipase activity in the homogenate that is capable of releasing free fatty acids. Third, Ca2+-stimulated O2 consumption and AA oxidation have virtually identical calcium requirements and pH optima. The sequence of events then is that upon calcium addition to the homogenate, lipase activity is increased which liberates free fatty acids. At the same time calcium also activates a polyunsaturated fatty acid oxygenase, possibly lipoxygenase, that converts the free fatty acids to hydroxy fatty acids. The possible physiological importance of this reaction is underscored by the high affinity for Ca2+ [approximately 10(-7)M], an ion known to increase above the required levels at fertilization. The pH activity profile also suggests possible physiological modulation because a pH change of 6.8 increasing to 7.2, as suggested to occur after fertilization, yields almost a twofold increase in O2 consumption. Egg homogenates from many other invertebrate species have the ability to oxidize AA in a Ca2+-dependent fashion. For the investigated species, the presence of Ca2+-stimulated O2 consumption and AA oxidation correlates with the presence of cyanide insensitive respiration in the intact egg.     

Lipoxygenases

Lipoxygenases (EC 1.13.11.12), commonly found in plant tissues, catalyze peroxidation of polyunsaturated fatty acids to various primary and secondary oxidation products. Some of these products affect the aroma of foods and some may be of significance in plant growth and development and/or pest resistance.     

Engineering oilseeds to produce nutritional fatty acids

There is a growing body of evidence suggesting that regular consumption of foods rich in omega-3 long chain polyunsaturated fatty acids has multiple positive health benefits. The fats and oils from marine fish contain high contents of these beneficial fatty acids but increased consumer demand has also increased strain on the ability of the world's fisheries to meet demand from wild capture. Many consumers are choosing fish oil supplements or are eating foods that have been complemented with fish oils instead of consuming fish directly. However, removing undesirable odors, flavors and contaminants is expensive. In contrast, oils derived from land plants such as soybean are inexpensive and contaminant free. Recent strides in plant molecular biology now allow the engineering of oilseeds for the production of novel fats and oils, including those synthesized by complex, multigene biosynthetic pathways such as the omega-3 long chain polyunsaturated fatty acids. Given the potential benefits to the environment with regards to overfishing and the health prospects of increased consumption of these healthy fatty acids, producing these fatty acids in oilseeds is a desirable and worthy goal. In this review, we will describe the recent advances in this field along with some of the technical hurdles encountered thus far.     

Lipid Peroxides in the Free Radical Pathophysiology of Brain Diseases

1. Polyunsaturated fatty acids are essential for normal neural cell membrane functioning because many membrane properties, such as fluidity and permeability, are closely related to the presence of unsaturated and polyunsaturated side chains. Lipid peroxidation results in loss of membrane polyunsaturated fatty acids and oxidized phospholipids as polar species contributing to increased membrane rigidity.2. Polyunsaturated fatty acids are released from membrane phospholipids by a number of enzymic mechanisms involving the receptor-mediated stimulation of phospholipase A₂ and phospholipase C/diacylglycerol lipase pathways.3. The overstimulation of excitatory amino acid (EAA) receptors stimulates the activities of lipases and phospholipases, and this stimulation produces changes in membrane phospholipid composition, permeability, and fluidity, thus decreasing the integrity of plasma membranes.4. Alterations in properties of plasma membranes may be responsible for the degeneration of neurons seen in neurodegenerative diseases. Two major processes may be involved in neuronal injury caused by the overstimulation of EAA receptors. One is a large Ca²⁺ influx and the other is an accumulation of free radicals and lipid peroxides as a result of neural membrane phospholipid degradation. It is suggested that calcium and free radicals act in concert to induce neuronal injury in acute trauma (ischemia and spinal cord injury) and in neurodegenerative diseases.     

Comparative study of fatty-acid composition of table eggs from the Jeddah food market and effect of value addition in omega-3 bio-fortified eggs

Health consciousness has increased the desire of people around the world to consume functional foods. Omega-3 essential fatty acids are one among these beneficial and important health supplements without which a general predisposition to degenerative and stress related disorders can occur. Saudi Arabia has shown an alarming increase in obesity (Al-Nozha et al., 2005), diabetes (Alqurashi et al., 2011), and cardiovascular disease (Al-Nozha et al., 2004) in the last few decades mainly due to nutritional transitions and lifestyle alterations (Amuna and Zotor, 2008). Lack of nutrient dense foods and the prevailing food related disorder of obesity (Popkin, 2001; Prentice, 2014) especially render egg as a choice food to be value-added for attaining nutritional security in Saudi Arabia and in effect reverse the increasing incidences of lifestyle diseases. Nutritional intervention through a commonly consumed food product would be an important step in improving the health of the people, and reducing health care costs. As eggs are a frequently consumed food item in Saudi Arabia, enriching them with omega-3 fatty acids would be an excellent way to alleviate the existing problems. A significant deposition of omega-3 fatty acids in the eggs was observed when the diet of hens was supplemented with omega-3 fatty acids from either flaxseed or fish oil source. Inadequacy of omega-3 fatty acids could thus be rectified by producing omega-3 enriched eggs from hens supplemented with flaxseed or fish oil source, and thus contribute toward better health choice of the consumer.     

7-Hydroxycholestrol as a possible biomarker of cellular lipid peroxidation: Difference between cellular and plasma lipid peroxidation

Polyunsaturated fatty acids and their esters are known to be susceptible to free radical-mediated oxidation, whereas cholesterol is thought to be more resistant to oxidation. In fact, it has been observed that in the case of plasma lipid peroxidation, the amount of oxidation products of polyunsaturated fatty acids such as linoleic acid was higher than that of cholesterol. In contrast, during oxidative stress-induced cellular lipid peroxidation, oxidation products of cholesterol such as 7-hydroxycholesterol (7-OHCh) were detected in greater amounts than those of linoleates such as hydroxyoctadecadienoic acid (HODE). There are several forms of oxidation products of cholesterol and linoleates in vivo, namely, hydroperoxides, as well as the hydroxides of both the free and ester forms of cholesterol and linoleates. To evaluate these oxidation products, a method used to determine the lipid oxidation products after reduction and saponification was developed. With this method, several forms of oxidation products of cholesterol and linoleates are measured as total 7-OHCh (t7-OHCh) and total HODE (tHODE), respectively. During free radical-mediated lipid peroxidation in plasma, the amount of tHODE was 6.3-fold higher than that of t7-OHCh. In contrast, when Jurkat cells were exposed to free radicals, the increased amount of cellular t7-OHCh was 5.7-fold higher than that of tHODE. Higher levels of t7-OHCh than those of tHODE have also been observed in selenium-deficient Jurkat cells and glutamate-treated neuronal cells. These results suggest that, in contrast to plasma oxidation, cellular cholesterol is more susceptible to oxidation than cellular linoleates. Collectively, cholesterol oxidation products at the 7-position may be a biomarker of cellular lipid peroxidation.     

Effects of dietary factors on oxidation of low-density lipoprotein particles

Oxidized low-density lipoproteins (ox-LDLs) appear to play a significant role in atherogenesis. In fact, circulating ox-LDL concentrations have been recognized as a risk factor for cardiovascular disease (CVD). A higher intake of some nutrients and specific food compounds such as monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs) and flavonoids have also been associated with a lower risk of CVD. These dietary factors could be associated to a lower risk of CVD through a reduction of the atherogenicity of LDL particles through limited oxidation. Therefore, the purpose of this article is to review human clinical studies that evaluated effects of dietary antioxidant vitamins, fatty acids (MUFA, PUFA) and specific flavonoid-rich foods on LDL particle oxidation and describe potential mechanisms by which dietary factors may prevent oxidation of LDL particles. Antioxidant vitamin supplements such as alpha-tocopherol and ascorbic acid as well as beta-carotene and fish-oil supplements have not been clearly demonstrated to prevent oxidation of LDL particles. Moreover, inconsistent documented effects of flavonoid-rich food such as olive oil, tea, red wine and soy on LDL particle oxidizability may be explained by difference in variety and quantity of flavonoid compounds used among studies. However, a healthy food pattern such as the Mediterranean diet, which includes a combination of antioxidant compounds and flavonoid-rich foods, appears effective to decrease LDL particle oxidizability, which may give some insight of the cardiovascular benefits associated with the Mediterranean diet.     

Dietary monounsaturated versus polyunsaturated fatty acids: which is really better for protection from coronary heart disease?

PURPOSE OF REVIEW: The purpose is to evaluate recent findings concerning dietary fats and the risk of coronary heart disease. Monounsaturated fatty acids are often regarded as healthy, and many have recommended their consumption instead of saturated fatty acids and polyunsaturated fatty acids. Support for the benefits of monounsaturated fatty acids comes largely from epidemiological data, but they have not been an isolated, single variable in such studies. Beneficial effects on the plasma lipid profile and LDL oxidation rates have also been identified. More recent findings have questioned the impact of suspected beneficial effects on coronary heart disease, indicating that studies with more conclusive endpoints are needed. RECENT FINDINGS: Human dietary studies often produce conflicting results regarding the effects of monounsaturated and polyunsaturated fatty acids on the plasma lipid profile. Monounsaturated and polyunsaturated fatty acids both appear to reduce total and LDL-cholesterol compared with saturated fatty acids; however, the effect on HDL is less clear. Lowered HDL levels in response to low-fat or polyunsaturated fatty acid diets and the decreased protection from oxidation of polyunsaturated fatty acid-enriched LDL may not indicate increased coronary heart disease risk. Several lines of evidence also suggest that polyunsaturated fatty acids may protect against atherosclerosis. SUMMARY: Recommendations to substitute monounsaturated fatty acids for polyunsaturated fatty acids or a low-fat carbohydrate diet seem premature without more research into the effects on the development of atherosclerosis. Current opinions favoring monounsaturated fatty acids are based on epidemiological data and risk factor analysis, but are questioned by the demonstrated detrimental effects on atherosclerosis in animal models.     

The Important Role of Lipid Peroxidation Processes in Aging and Age Dependent Diseases

Any change in the cell membrane structure activates lipoxygenases (LOX). LOX transform polyunsaturated fatty acids (PUFAs) to lipidhydroperoxide molecules (LOOHs). When cells are severely wounded, this physiological process switches to a non-enzymatic lipid peroxidation (LPO) process producing LOO^· radicals. These oxidize nearly all-biological molecules such as lipids, sugars, and proteins. The LOO^· induced degradations proceed by transfer of the radicals from cell to cell like an infection. The chemical reactions induced by LO^· and LOO^· radicals seem to be responsible for aging and induction of age dependent diseases. Alternatively, LO^· and LOO^· radicals are generated by frying of fats and involve cholesterol-PUFA esters and thus induce atherogenesis. Plants and algae are exposed to LOO^· radicals generating radiation. In order to remove LOO^· radicals, plants and algae transform PUFAs to furan fatty acids, which are incorporated after consumption of vegetables into mammalian tissues where they act as excellent scavengers of LOO^· and LO^· radicals. Figure 6 of this article is reprinted from the paper of G. Spiteller: “Peroxyl radicals: Inductors of neurodegenerative and other inflammatory diseases. Their origin and how they transform cholesterol, phospholipids, plasmalogens, polyunsaturated fatty acids, sugars and proteins into deleterious products” published in Free Radic. Biol. Med. 41, 362–387 (2006) Elsevier, 2006 by permission from Elsevier.     

Use of recovered frying oils in chicken and rabbit feeds: effect on the fatty acid and tocol composition and on the oxidation levels of meat,liver and plasma

The addition of some fat co- and by-products to feeds is usual nowadays; however, the regulations of their use are not always clear and vary between countries. For instance, the use of recycled cooking oils is not allowed in the European Union, but they are used in other countries. However, oils recovered from industrial frying processes could show satisfactory quality for this purpose. Here we studied the effects of including oils recovered from the frying industry in rabbit and chicken feeds (at 30 and 60 g/kg, respectively) on the fatty acid (FA) and tocol (tocopherol + tocotrienol) compositon of meat, liver and plasma, and on their oxidative stability. Three dietary treatments (replicated eight times) were compared: fresh non-used oil (LOX); oil discarded from the frying industry, having a high content of secondary oxidation compounds (HOX); and an intermediate level (MOX) obtained by mixing 50 : 50 of LOX and HOX. The FA composition of oil diets and tissues was assessed by GC, their tocol content by HPLC, the thiobarbituric acid value was used to assess tissue oxidation status, and the ferrous oxidation-xylenol orange method was used to assess the susceptibility of tissues to oxidation. Our results indicate that FA composition of rabbit and chicken meat, liver and plasma was scarcely altered by the addition of recovered frying oils to feed. Differences were encountered in the FA composition between species, which might be attributed mainly to differences in the FA digestion, absorption and metabolism between species, and to some physiological dietary factors (i.e. coprophagy in rabbits that involves fermentation with FA structure modification). The α-tocopherol (αT) content of tissues was reduced in response to the lower αT content in the recovered frying oil. Differences in the content of other tocols were encountered between chickens and rabbits, which might be attributable to the different tocol composition of their feeds, as well as to species differences in the digestion and metabolism of tocols. Tissue oxidation and susceptibility to oxidation were in general low and were not greatly affected by the degree of oxidation of the oil added to the feeds. The relative content of polyunsaturated fatty acids/αT in these types of samples would explain the differences observed between species in the susceptibility of each tissue to oxidation. According to our results, oils recovered from the frying industry could be useful for feed uses.     

Oxygen free radical induced damage during intestinal ischemia/reperfusion in normal and xanthine oxidase deficient rats

This study looks at the role of xanthine oxidase (XO) in ischemia/reperfusion (I/R) induced intestinal mucosal damage using normal and xanthine oxidase deficient rats. Tungstate feeding for 3 days depleted the intestinal mucosal XO by 80%. A ligated loop of the rat small intestine (both normal and XO-deficient) was subjected to 1 h of total ischemia followed by 5 min revascularisation. The ensuing mucosal damage was assessed by biochemical and histological studies. Ischemia or I/R increased the XO levels in normal rats without any change in XO-deficient rats. Myeloperoxidase (a neutrophil marker) level was increased in both group of rats but it was comparatively higher in the XO-deficient rats. Accumulation of peroxidation products such as malondialdehyde, conjugated diene and increased production of hydroxyl radicals by microsomes were seen after ischemia and I/R and were similar in normal and XO-deficient rats. Studies on other parameters of peroxidation showed a decrease in polyunsaturated fatty acids and alpha-tocopherol, an increase in cysteine and cystine levels after I/R and were similar in both normal and XO-deficient rats. Histological results indicated gross morphological changes in the intestinal mucosa due to ischemia and I/R, and the damage was more severe in XO-deficient rats. These observations suggest that oxygen-derived free radicals are involved in the intestinal mucosal damage during I/R and infiltrated neutrophils rather than XO may be the primary source of free radicals under these conditions.     

Cultivation of Microorganisms in the Cultural Medium Made from Squid Internal Organs and Accumulation of Polyunsaturated Fatty Acids in the Cells

The disposal and more efficient utilization of marine wastes is becoming increasingly serious. A culture media for microorganisms has been prepared from squid internal organs that are rich in polyunsaturated fatty acids (PUFAs). Both freshwater and marine bacteria grew well in this medium and some bacteria accumulated PUFAs in their lipids, suggesting uptake of exogenous PUFAs. Higher PUFA accumulations were observed in Escherichia coli mutant cells defective either in unsaturated fatty acid biosynthesis or fatty acid degradation, or both, compared to those without these mutations. Therefore, PUFA accumulation in cells can be improved by genetic modification of fatty acid metabolism in the bacteria. Squid internal organs would be a good source of medium, not only for marine bacteria but also for freshwater bacteria, and that this process may be advantageous to make efficient use of the fishery wastes and to produce PUFA-containing microbial cells and lipids.     

Oregano essential oil as an inhibitor of higher fatty acid oxidation

Inhibition of the oxidation of fatty acids methyl esters by oregano essential oil was studied using capillary gas chromatography. A mixture of fatty acids which contained saturated, mono-, di-, and polyunsaturated acids with 16–24 carbon atoms was extracted from mice brain. Changes in the composition of esters in hexane solutions both in the presence of oregano essential oil and without it were examined during their autooxidation in light for 1 year. It was found that the oxidation rate of unsaturated fatty acids increases with increasing degree of their unsaturation. Oregano essential oil inhibited the oxidation process. Antioxidant activity of the oil increased with increase of its concentration. It was shown that carvacrol and thymol are the main antioxidant components of oregano oil.     

Studies on the metal-ion and lipoxygenase-catalysed breakdown of hydroperoxides using electron-spin-resonance spectroscopy.

The breakdown of cumene hydroperoxide and peroxidized fatty acids by iron is shown, by use of the spin trap 5,5-dimethyl-l-pyrroline-N-oxide, to be sensitive to (a) the oxidation state of the metal and (b) the nature of the chelating ligands. The initial step in the Fe2+-catalysed breakdown is the production of an alkoxyl radical by one-electron reduction, and this type of radical has been successfully trapped from each substrate. Subsequent reactions of this alkoxyl species produce both carbon-centred and peroxyl radicals, depending on the concentrations of the reagents present. The use of the same spin trap in microsomal systems undergoing either NADPH-supported or Fe2+-induced peroxidation led to the detection of low concentrations of radical adducts, among which are signals that are believed to be due to lipid alkoxyl radicals. Reaction of polyunsaturated fatty acid hydroperoxides with both Fe2+ and lipoxygenase under anaerobic conditions gives rise to signals not only from the alkoxy-radical adduct, but also from a further species which is tentatively identified as being due to an acyl [RC(O).]-radical adduct; chemical studies lend support to this assignment.     

Lipid peroxyl radical intermediates in the peroxidation of polyunsaturated fatty acids by lipoxygenase. Direct electron spin resonance investigations

Lipid peroxyl radicals resulting from the peroxidation of polyunsaturated fatty acids by soybean lipoxygenase were directly detected by the method of rapid mixing, continuous-flow electron spin resonance spectroscopy. When air-saturated borate buffer (pH 9.0) containing linoleic acid or arachidonate acid was mixed with lipoxygenase, fatty acid-derived peroxyl free radicals were readily detected; these radicals have a characteristic g-value of 2.014. An organic free radical (g = 2.004) was also detected; this may be the carbon-centered fatty acid free radical that is the precursor of the peroxyl free radical. The ESR spectrum of this species was not resolved, so the identification of this free radical was not possible. Fatty acids without at least two double bonds (e.g. stearic acid and oleic acid) did not give the corresponding peroxyl free radicals, suggesting that the formation of bisallylic carbon-centered radicals precedes peroxyl radical formation. The 3.8-G doublet feature of the fatty acid peroxyl spectrum was proven (by selective deuteration) to be a hyperfine coupling due to a gamma-hydrogen that originated as a vinylic hydrogen of arachidonate. Arachidonate peroxyl radical formation was shown to be dependent on the substrate, active lipoxygenase, and molecular oxygen. Antioxidants are known to protect polyunsaturated fatty acids from peroxidation by scavenging peroxyl radicals and thus breaking the free radical chain reaction. Therefore, the peroxyl signal intensity from micellar arachidonate solutions was monitored as a function of the antioxidant concentration. The reaction of the peroxyl free radical with Trolox C was shown to be 10 times slower than that with vitamin E. The vitamin E and Trolox C phenoxyl radicals that resulted from scavenging the peroxyl radical were also detected.     

The effect of ionizing radiation on the fatty acid composition of natural fats and on lipid peroxide formation.

The effects of irradiation doses of 200-1000 krad on the fatty acid compositions of saturated and unsaturated natural food fats have been studied. Lard, coconut oil, corn oil, methyl linoleate and herring oil have been analysed before and after irradiation for lipid peroxide content and fatty acid composition. The effects of storage under varied conditions after irradiation have also been investigated. Irradiation doses of 200-1000 krad had little effect on the fatty acid compositions of saturated fats (lard and coconut oil) or of fats with a high antioxidant content (corn oil) but caused destruction of 98 per cent of the highly unsaturated acids (18: 4,20 :5,22 : 6) and 46 per cent of the diene acids (18:2) in herring oil. The destruction of the polyunsaturated fatty acids increased with increasing storage temperature and storage time. The destruction of polyunsaturated fatty acids is accompanied by an increase in lipid peroxide formation. It is considered that changes in fatty acid composition in natural foods after irradiation are important in consideration of the use of irradiation for food preservation.     

食物中多不饱和脂肪酸在家蝇幼虫体内的富集与代谢及对其生长的影响

【目的】阐明家蝇 Musca domestica 幼虫对食物中各种多不饱和脂肪酸的富集能力以及代谢转化情况,并探究各种多不饱和脂肪酸对家蝇幼虫生长的影响。【方法】在基础饲料中添加不同浓度(3%, 6%和12%)的多不饱和脂肪酸(亚油酸、α-亚麻酸、花生四烯酸和二十二碳六烯酸)饲养经过脱脂传代培养的家蝇幼虫;提取家蝇幼虫的总脂肪酸,利用气相色谱仪进行检测和分析;测定统计幼虫体重,以分析多不饱和脂肪酸对家蝇幼虫生长的影响。【结果】亚油酸、α-亚麻酸和花生四烯酸在家蝇幼虫体内均能被富集,且它们的富集程度随着食物中多不饱和脂肪酸的添加浓度的升高而增加,其中亚油酸、α-亚麻酸和花生四烯酸在幼虫体内富集的最高含量(占体内总脂肪酸的比例)分别为21.93%, 16.13%和9.68%,而二十二碳六烯酸不能在家蝇幼虫体内富集,提示家蝇幼虫食物中添加的各种多不饱和脂肪酸经过代谢后并没有在其体内产生新的脂肪酸,而食物中添加的二十二碳六烯酸在家蝇幼虫体内被分解代谢后消除。饲喂α-亚麻酸及花生四烯酸后家蝇幼虫体重增长较为明显,其中6%α-亚麻酸添加组的幼虫体重显著高于对照组(取食脱脂饲料)和3%和12%α-亚麻酸添加组,3%和6%花生四烯酸添加组的幼虫体重显著高于对照组和12%花生四烯酸添加组。【结论】家蝇幼虫体内能够从食物中富集部分多不饱和脂肪酸,多不饱和脂肪酸碳链越长其富集程度越低直至不能富集,富集的多不饱和脂肪酸对家蝇幼虫生长有不同程度的影响。