The essential dietary fatty acid requirement of the tufted apple budmoth, Platynota idaeusalis

The tufted apple budmoth, Platynota idaeusalis (Walker), was reared non-axenically for two successive generations on a casein-based semisynthetic diet. The qualitative essential fatty acid requirement for growth, development and normal pupal-adult ecdysis was studied using the non-axenic casein-based semisynthetic diets with and without various 99% pure fatty acids. Linoleic or linolenic acids caused accelerated larval development; linoleic, linolenic and arachidonic acids showed similar activity in body weight gain and survival to pupal-adult ecdysis. Linoleic or linolenic acids were active in alleviating wing deformities; arachidonic acid was partially active in alleviating wing deformities at the one dietary concentration evaluated. Activity of arachidonic acid as an essential fatty acid for P. idaeusalis is unique among insects, except for mosquitoes. The essential fatty acid deficiency syndrome of the adult, resulting from the larvae feeding on fat-deficient diets, was greatly reduced when larvae were fed on a diet adequate in essential fatty acid during either their early or late development.     

Arachidonic and other tissue fatty acids of Culex pipiens reared with various concentrations of dietary arachidonic acid

Chloroform/methanol extracts were prepared from groups of Culex pipiens reared in synthetic dietary media provided with various concentrations of arachidonic acid. Extracts were analyzed by gas-liquid chromatography to determine the fatty acid composition of whole extracts and also of phospholipid and triacylglycerol fractions separated by thin-layer chromatography from the whole extracts. The same extracts were also tested for their ability to support flight of adult C. pipiens reared in basal synthetic diet containing various concentrations of the extracts: this provided a bioassay for the presence of arachidonic acid or related polyunsaturates in the extracted lipid, since adults can fly only if provided, as larvae, with dietary arachidonic or related fatty acids. For comparison, chromatographic and bioassay data obtained from normal stock mosquitoes, reared in crude septic medium, are also presented. All extracts were shown by gas-liquid chromatography to contain some arachidonic acid and other polyunsaturated fatty acids. The proportions of arachidonic acid in extracts from mosquitoes reared in synthetic media were greater the greater the concentration of dietary arachidonic acid provided; and in the bioassay, extracts induced more flight activity in test mosquitoes the higher the dietary arachidonic acid provided for extracted mosquitoes. Extracts from stock-reared mosquitoes were more active in the bioassay than synthetic dietreared extracts, even though gas-liquid chromatography indicated lower proportions of arachidonic acid in stock-reared extract. However, stock-reared extract contained a substantial proportion of gammalinolenic acid, which is flight active for C. pipiens, as well as more linolenic acid and a large amount of linoleic acid, both of which are semi-active for flight; thus, stock-reared extract contained a higher overall proportion of flight-inducing fatty acids. Proportions of polyunsaturates in the phospholipid fractions of extracts from synthetic diet-reared mosquitoes were much greater than in the unfractionated extracts, whereas polyunsaturates were virtually absent from the triacylglycerol fractions, indicating a sequestering of polyunsaturates into phospholipids.     

The predominance of polyunsaturated fatty acids in the butterfly Morpho peleides before and after metamorphosis

We hypothesized that the polyunsaturated fatty acids of the butterfly were probably derived from the diet and that there might be a great loss of body fat during metamorphosis. To substantiate these hypotheses, we analyzed the fatty acid composition and content of the diet, the larva, and the butterfly Morpho peleides. Both the diet and the tissues of the larva and butterfly had a high concentration of polyunsaturated fatty acids. In the diet, linolenic acid accounted for 19% and linoleic acid for 8% of total fatty acids. In the larva, almost 60% of the total fatty acids were polyunsaturated: linolenic acid predominated at 42% of total fatty acids, and linoleic acid was at 17%. In the butterfly, linolenic acid represented 36% and linoleic acid represented 11% of total fatty acids. The larva had a much higher total fatty acid content than the butterfly (20.2 vs. 6.9 mg). Our data indicate that the transformation from larva to butterfly during metamorphosis drastically decreased the total fatty acid content. There was bioenhancement of polyunsaturated fatty acids from the diet to the larva and butterfly. This polyunsaturation of membranes may have functional importance in providing membrane fluidity useful in flight.     

Effect of a high-fat diet with partially hydrogenated fish oil on long-chain fatty acid metabolizing enzymes in subcellular fractions of rat liver

Hepatic metabolism of long-chain fatty acids were studied in young male rats fed a semisynthetic diet containing 20% (w/w) partially hydrogenated fish oil (PHFO)2, with or without 2% (w/w) linoleic acid. The enzymic activities involved in the formation and breakdown of long-chain acyl-CoA were both increased in the animals fed the semisynthetic diet, compared to pellet-fed control animals. Thus, the specific palmitoyl-CoA synthetase activity increased slightly in both the mitochondrial (1.4-fold) and the microsomal (1.6-fold) fractions. In the peroxisome-enriched fraction the activity was increased (about 2.6-fold) only on addition of linoleic acid to the diet. The data are consistent with an increased catabolism of long-chain fatty acids by a peroxisomal and a mitochondrial pathway. Thus, the total carnitine palmitoyltransferase activity increased 2-fold in the mitochondrial fraction, and was partly prevented by added linoleic acid. Peroxisomal beta-oxidation activity was also increased (about 7-fold) in livers of PHFO-fed rats, but did not change when linoleic acid was added. The PHFO-fed rats also revealed elevated capacity for hydrolysis of palmitoyl-CoA in both the mitochondrial (2.4-fold) and the cytosolic (2.0-fold) fractions and the latter was almost completely and selectively prevented by added linoleic acid. The s values of mitochondria and peroxisomes varied with the dietary regime, and some of the observed changes in the specific activities of the fatty acid metabolizing enzymes with multiple subcellular localization can be explained as an effect of changes in the s values of the organelles. Thus, the s value of mitochondria increased 1.8-fold as a result of PHFO feeding, but was fully prevented by linoleic acid in the diet. On the other hand, the s values of peroxisomes decreased by about 50% on feeding a PHFO diet, and by about 25% with added linoleic acid.     

The effect of diet on the fatty acid compositions of serum, brain, brain mitochondria and myelin in the rat

1. Three groups of female rats (8-12 weeks old) were maintained respectively on a linoleic acid-rich diet, a linoleic acid-poor predominantly saturated-fatty acid diet and a normal diet. Changes in the fatty acid compositions of serum, brain, brain mitochondria-rich fraction and myelin were observed. 2. Of the serum fatty acids, linoleic acid showed the greatest change in the percentage of the total acids in response to diet; the change in the proportion of oleic acid was considerable. The percentages of arachidonic acid in serum fatty acids in the groups on the linoleic acid-rich and linoleic acid-poor diets were similar, but higher than those in the normal group. 3. Changes in the proportions of linoleic acid, arachidonic acid and docosahexaenoic acid occurred in brain fatty acids that to some extent paralleled those occurring in the serum. Changes in the proportions of most other acids in the serum fatty acids were not accompanied by corresponding changes in the brain fatty acids. 4. The percentage fatty acid compositions of a mitochondria-rich fraction and myelin are given, and changes in the relative proportions of linoleic acid, arachidonic acid and possibly some docosapolyenoic acids were demonstrated to occur as a result of diet. 5. The results are discussed in relation to the possible aetiology of multiple sclerosis.     

Essential fatty acid consideration at birth in the premature neonate and the specific requirement for preformed prostaglandin precursors in the infant

The essentiality of certain PUFA is probably related to their capability to be incorporated into lipids and to act as precursor in the formation of ecosanoids. Esterified to phospholipids, the EFA influence the physico-chemical characteristics of biomembranes. Normal growth of infants is dependent upon an adequate supply of EFA. The human fetus, like the adult, is unable to synthesize the EFA, which must therefore be derived from the maternal circulation and pass through the placenta. Increased concentration of the polyenoic fatty acids with advanced gestational age may result from increased synthetic activity of these fatty acids by the fetus or the placenta or by preferential transfer of these fatty acids across the placenta. Several clinical manifestations have been ascribed in the human infant to prolonged EFA deficiency; however, none of these findings were noted in a group of sick newborn infants with very rapid onset of deficiency. Platelet dysfunction, decreased prostaglandin biosynthesis and turnover and altered pulmonary surfactant are among the effects of EFA deficiency on infants. Supplementation of the diet with EFA, parenterally or by the inunction of oil rich in linoleic acid, were reported to alleviate the symptoms of EPA deficiency. The minimal estimated requirement of linoleic acid is 1% of calories and 4% is an optimal intake. Most diets, including human breast milk, infant formulas and parenteral fat emulsions, far exceed the optimal intake of linoleic acid. Relatively little is known about the possible effects of high levels of linoleate in the diet.     

Effects of dietary amino acids on the production of sexual morph by the green peach aphid,Myzus persicae

In order to complete a holocycle of the green peach aphid, Myzus persicae, on a synthetic diet, the effects of dietary amino acid contents on development of sexuals were investigated. For this purpose, the aphids were reared on holidic diets for two to three generations at 20°C under a scotophase of 15 h per diem. Under these conditions, the production of males by the aphids on a synthetic diet was very much poorer than those reared on radish seedling. On reducing the amino acid concentration of the diet, the proportion of males produced was comparable to that produced by aphids fed on radish seedlings. The obtained males were smaller and survived longer than those reared on radish seedling. Under the long night photoperiod and on the synthetic diet with reduced amino acids, gynoparae and then oviparae were also obtained. The oviparae were mated with the males grown on the synthetic diet, and laid eggs. The eggs, however, did not turn dark in color, and perished. © 1995 Wiley-Liss, Inc.     

Influence of dietary partially hydrogenated fat high in trans fatty acids on lipid composition and function of intestinal brush border membrane in rats

The effect of dietary hydrogenated fat (Indian vanaspati) high in trans fatty acids (6 en%) on lipid composition, fluidity and function of rat intestinal brush border membrane was studied at 2 and 8 en% of linoleic acid. Three groups of weanling rats were fed rice-pulse based diet containing 10% fat over a ten week period: Group I (groundnut oil), Group II (vanaspati), Group III (vanaspati + safflower oil). The functionality of the brush border membrane was assessed by the activity of membrane bound enzymes and transport of D-glucose and L-leucine. The levels of total cholesterol and phospholipids were similar in all groups. The data on fatty acid composition of membrane phospholipids showed that, at 2 en% of linoleic acid in the diet, trans fatty acids lowered arachidonic acid and increased linoleic acid contents indicating altered polyunsaturated fatty acid metabolism. Alkaline phosphatase activity was increased while the activities of sucrase, gamma-glutamyl transpeptidase and transport of D-glucose and L-leucine were not altered by dietary trans fatty acids. However at higher intake of linoleic acid in the diet, trans fatty acids have no effect on polyunsaturated fatty acid composition and alkaline phosphatase activity of intestinal brush border membrane. These data suggest that feeding dietary fat high in trans fatty acids is associated with alteration in intestinal brush border membrane polyunsaturated fatty acid composition and alkaline phosphatase activity only when the dietary linoleic acid is low.     

The influence of linoleic acid and linolenic acid on adult moth emergence of Homona coffearia from meridic diets in vitro

The fatty acids linoleic and linolenic acids have been found to be critical dietary supplements for the successful adult emergence of Homona coffearia reared in meridic diets in vitro. When the levels of these fatty acids were sub-optimal, the moths were able to emerge only partially and a few that emerged fully were deformed with naked wings. In the presence of optimal amounts of these fatty acids, the Δ⁷ sterol, ergosterol, available in the brewer's yeast provided in the diets was found to be adequate for growth and adult emergence. The availability of linoleic acid, which appeared to be the more critical requirement, was sufficient for successful adult emergence, provided that the diet was supplemented with additional amounts of ergosterol. The above two fatty acids seemed to be the only critical dietary supplements offered by whole tea leaves incorporated in a previously described oligidic diet. The provision of a dietary source of a Δ⁷ sterol was found essential as this insect was unable to utilize cholesterol.     

A Western-like fat diet is sufficient to induce a gradual enhancement in fat mass over generations

The prevalence of obesity has steadily increased over the last few decades. During this time, populations of industrialized countries have been exposed to diets rich in fat with a high content of linoleic acid and a low content of α-linolenic acid compared with recommended intake. To assess the contribution of dietary fatty acids, male and female mice fed a high-fat diet (35% energy as fat, linoleic acid:α-linolenic acid ratio of 28) were mated randomly and maintained after breeding on the same diet for successive generations. Offspring showed, over four generations, a gradual enhancement in fat mass due to combined hyperplasia and hypertrophy with no change in food intake. Transgenerational alterations in adipokine levels were accompanied by hyperinsulinemia. Gene expression analyses of the stromal vascular fraction of adipose tissue, over generations, revealed discrete and steady changes in certain important players, such as CSF3 and Nocturnin. Thus, under conditions of genome stability and with no change in the regimen over four generations, we show that a Western-like fat diet induces a gradual fat mass enhancement, in accordance with the increasing prevalence of obesity observed in humans.     

The role of lipid components of the diet in the regulation of the fatty acid composition of the rat liver endoplasmic reticulum and lipid peroxidation

The fatty acid compositions of the lipids and the lipid peroxide concentrations and rates of lipid peroxidation were determined in suspensions of liver endoplasmic reticulum isolated from rats fed on synthetic diets in which the fatty acid composition had been varied but the remaining constituents (protein, carbohydrate, vitamins and minerals) kept constant. Stock diet and synthetic diets containing no fat, 10% corn oil, herring oil, coconut oil or lard were used. The fatty acid composition of the liver endoplasmic reticulum lipid was markedly dependent on the fatty acid composition of the dietary lipid. Feeding a herring-oil diet caused incorporation of 8.7% eicosapentaenoic acid (C_20:5) and 17% docosahexaenoic acid (C_22:6), but only 5.1% linoleic acid (C_18:2) and 6.4% arachidonic acid (C_20:4), feeding a corn-oil diet caused incorporation of 25.1% C_18:2, 17.8% C_20:4 and 2.5% C_22:6 fatty acids, and feeding a lard diet caused incorporation of 10.3% C_18:2, 13.5% C_20:4 and 4.3% C_22:6 fatty acids into the liver endoplasmic-reticulum lipids. Phenobarbitone injection (100mg/kg) decreased the incorporation of C_20:4 and C_22:6 fatty acids into the liver endoplasmic reticulum of rats fed on a lard, corn-oil or herring-oil diet. Microsomal lipid peroxide concentrations and rates of peroxidation in the presence of ascorbate depended on the nature and quantity of the polyunsaturated fatty acids in the diet. The lipid peroxide content was 1.82±0.30nmol of malonaldehyde/mg of protein and the rate of peroxidation was 0.60±0.08nmol of malonaldehyde/min per mg of protein after feeding a fat-free diet, and the values were increased to 20.80nmol of malonaldehyde/mg of protein and 3.73nmol of malonaldehyde/min per mg of protein after feeding a 10% herring-oil diet in which polyunsaturated fatty acids formed 24% of the total fatty acids. Addition of α-tocopherol to the diets (120mg/kg of diet) caused a very large decrease in the lipid peroxide concentration and rate of lipid peroxidation in the endoplasmic reticulum, but addition of the synthetic anti-oxidant 2,6-di-t-butyl-4-methylphenol to the diet (100mg/kg of diet) was ineffective. Treatment of the animals with phenobarbitone (1mg/ml of drinking water) caused a sharp fall in the rate of lipid peroxidation. It is concluded that the polyunsaturated fatty acid composition of the diet regulates the fatty acid composition of the liver endoplasmic reticulum, and this in turn is an important factor controlling the rate and extent of lipid peroxidation in vitro and possibly in vivo.     

Mass spectral characterization of fatty acid amides from alfalfa trichomes and their deterrence against the potato leafhopper

A homologous series of N-(3-methylbutyl)amides of normal saturated C14, C15, C16, C17 and C18 fatty acids were identified as major components of glandular trichome extracts from Medicago sativa G98A, an alfalfa genotype resistant to the potato leafhopper, Empoasca fabae. A second homologous series of N-(2-methylpropyl)amides of C14 through C18 normal fatty acids were minor components. Saturated free fatty acids C12, C13, C14, C15, C16, C17 and C18 were present in trace amounts, as was the N-(3-methylbutyl)amide of linoleic acid (C18:2). N-(3-methylbutyl)amides and N-(2-methylpropyl)amides of C14 through C18 fatty acids, along with the N-(3-methylbutyl)amide of linoleic acid, were synthesized and bioassayed for leafhopper deterrence by applying the compounds to the surface of a sachet containing an artificial diet. Leafhoppers were then offered a two-way choice between diet surfaces treated with the synthetic amides or an untreated control. N-(3-methylbutyl)amides and N-(2-methylpropyl)amides of C14 through C18 fatty acids did not deter leafhopper settling in a dose-dependent fashion. In contrast, when tested singly, N-(3-methylbutyl)amide of linoleic acid exhibited dose-dependent deterrence against leafhopper settling. Fatty acid amides localized in alfalfa glandular trichomes likely contribute to leafhopper resistance.     

Responses to oleic,linoleic and α-linolenic acids in high-carbohydrate,high-fat diet-induced metabolic syndrome in rats

We investigated the changes in adiposity, cardiovascular and liver structure and function, and tissue fatty acid compositions in response to oleic acid-rich macadamia oil, linoleic acid-rich safflower oil and α-linolenic acid-rich flaxseed oil (C18 unsaturated fatty acids) in rats fed either a diet high in simple sugars and mainly saturated fats or a diet high in polysaccharides (cornstarch) and low in fat. The fatty acids induced lipid redistribution away from the abdomen, more pronounced with increasing unsaturation; only oleic acid increased whole-body adiposity. Oleic acid decreased plasma total cholesterol without changing triglycerides and nonesterified fatty acids, whereas linoleic and α-linolenic acids decreased plasma triglycerides and nonesterified fatty acids but not cholesterol. α-Linolenic acid improved left ventricular structure and function, diastolic stiffness and systolic blood pressure. Neither oleic nor linoleic acid changed the left ventricular remodeling induced by high-carbohydrate, high-fat diet, but both induced dilation of the left ventricle and functional deterioration in low fat-diet-fed rats. α-Linolenic acid improved glucose tolerance, while oleic and linoleic acids increased basal plasma glucose concentrations. Oleic and α-linolenic acids, but not linoleic acid, normalized systolic blood pressure. Only oleic acid reduced plasma markers of liver damage. The C18 unsaturated fatty acids reduced trans fatty acids in the heart, liver and skeletal muscle with lowered stearoyl-CoA desaturase-1 activity index; linoleic and α-linolenic acids increased accumulation of their C22 elongated products. These results demonstrate different physiological and biochemical responses to primary C18 unsaturated fatty acids in a rat model of human metabolic syndrome.     

Dietary n-9, n-6, and n-3 fatty acids modify linoleic acid more than arachidonic acid levels in plasma and platelet lipids and minimally affect platelet thromboxane formation in the rabbit

We have studied the effects of semisynthetic diets containing 5% by weight (12% of the energy) of either olive oil (70% oleic acid, OA) or corn oil (58% linoleic acid), or fish oil (Max EPA, containing about 30% eicosapentaenoic, EPA C 20:5 n-3, plus docosahexaenoic, DHA C 22:6 n-3, acids, and less than 2% linoleic acid), fed to male rabbits for a period of five weeks, on plasma and platelet fatty acids and platelet thromboxane formation. Aim of the study was to quantitate the absolute changes of n-6 and n-3 fatty acid levels in plasma and platelet lipid pools after dietary manipulations and to correlate the effects on eicosanoid-precursor fatty acids with those on platelet thromboxane formation. The major differences were found when comparing the group fed fish oil and depleted linoleic acid vs the other groups. The accumulation of n-3 fatty acids in various lipid classes was associated with modifications in the distribution of linoleic acid and arachidonic acid in different lipid pools. In platelets maximal incorporation of n-3 fatty acids occurred in phosphatidyl ethanolamine, which also participated in most of the total arachidonic acid reduction occurring in platelets, and linoleic acid, more than archidonic acid, was replaced by n-3 fatty acids in various phospholipids. The archidonic acid content of phosphatidyl choline was unaffected and that of phosphatidyl inositol only marginally reduced. Thromboxane formation by thrombin stimulated platelets did not differ among the three groups, and this may be related to the minimal changes of arachidonic acid in phosphatidyl choline and phosphatidyl inositol.     

Dose-dependent effects of dietary gamma-linolenic acid on rat spleen lymphocyte functions.

Feeding rodents a diet rich in evening primrose oil (EPO), which contains 5-10 g gamma-linolenic acid (GLA)/100 g total fatty acids, has been shown to decrease lymphocyte proliferation and natural killer cell activity. However, EPO contains a very high level of linoleic acid which itself can affect lymphocyte functions and it is not clear to what extent the effects of EPO can be attributed to GLA. The current study investigated the effect of two levels of GLA in the rat diet upon immune cell functions; the level of linoleic acid was maintained below 30 g/100 g total fatty acids. Weanling rats were fed on high fat (178 g/kg) diets which contained 4.4 g or 10 g GLA/100 g total fatty acids in place of a proportion of linoleic acid. The total polyunsaturated fatty acid content and the n-6 to n-3 polyunsaturated fatty acid ratio of the diet were maintained at 35 g/100 g total fatty acids and 7, respectively. The fatty acid compositions of the serum and of spleen leukocytes were markedly influenced by that of the diet, with an increase in the proportions of GLA and dihomo-gamma-linolenic acid when the diets containing GLA were fed; these diets also increased the proportion of arachidonic acid in spleen leukocytes. Spleen lymphocyte proliferation in response to concanavalin A was significantly reduced (by 60%) by feeding the diet containing the higher level of GLA, but not by the diet containing the lower level of GLA. Spleen natural killer cell activity and prostaglandin E (PGE) production by spleen leukocytes were not significantly affected by inclusion of GLA in the diet, although there was a tendency towards decreased natural killer cell activity by cells from rats fed the high GLA diet. Thus, this study shows that dietary GLA is capable of altering the fatty acid composition of cells of the immune system and of exerting some immunomodulatory effects, but that the level of GLA in the diet must exceed 4.4 g/100 g total fatty acids for these effects to become apparent.     

Interactions of saturated, n-6 and n-3 polyunsaturated fatty acids to modulate arachidonic acid metabolism

Anti-thrombotic effects of omega-3 (n-3) fatty acids are believed to be due to their ability to reduce arachidonic acid levels. Therefore, weanling rats were fed n-3 acids in the form of linseed oil (18:3n-3) or fish oil (containing 20:5n-3 and 22:6n-3) in diets containing high levels of either saturated fatty acids (hydrogenated beef tallow) or high levels of linoleic acid (safflower oil) for 4 weeks. The effect of diet on the rate-limiting enzyme of arachidonic acid biosynthesis (delta 6-desaturase) and on the lipid composition of hepatic microsomal membrane was determined. Both linseed oil- or fish oil-containing diets inhibited conversion of linoleic acid to gamma-linolenic acid. Inhibition was greater with fish oil than with linseed oil, only when fed with saturated fat. delta 6-Desaturase activity was not affected when n-3 fatty acids were fed with high levels of n-6 fatty acids. Arachidonic acid content of serum lipids and hepatic microsomal phospholipids was lower when n-3 fatty acids were fed in combination with beef tallow but not when fed with safflower oil. Similarly, n-3 fatty acids (18:3n-3, 20:5n-3, 22:5n-3, and 22:6n-3) accumulated to a greater extent when n-3 fatty acids were fed with beef tallow than with safflower oil. These observations indicate that the efficacy of n-3 fatty acids in reducing arachidonic acid level is dependent on the linoleic acid to saturated fatty acid ratio of the diet consumed.     

Effect of dietary cis and trans fatty acids on serum lipoprotein[a] levels in humans.

Serum lipoprotein[a] (Lp[a]) is a strong risk factor for coronary heart disease. We therefore examined the effect of dietary fatty acid composition on serum Lp[a] levels in three strictly controlled experiments with healthy normocholesterolemic men and women. In Expt. I, 58 subjects consumed a control diet high in saturated fatty acids for 17 days. For the next 36 days, 6.5% of total energy intake from saturated fatty acids was replaced by monounsaturates plus polyunsaturates (monounsaturated fatty acid diet; n = 29) or by polyunsaturates alone (polyunsaturated fatty acid diet; n = 29). Both diets caused a slight, nonsignificant, increase in median Lp[a] levels, with no difference between diets. In Expt. II, 10% of energy from the cholesterol-raising saturated fatty acids (lauric, myristic, and palmitic acid) was replaced by oleic acid or by trans-monounsaturated fatty acids. Each of the 59 participants received each diet for 3 weeks in random order. The median level of Lp[a] was 26 mg/l on the saturated fatty acid diet; it increased to 32 mg/l (P less than 0.020) on the oleic acid diet and to 45 mg/l (P less than 0.001) on the trans-fatty acid diet. The difference in Lp[a] between the trans-fatty acid and the oleic acid diets was also highly significant (P less than 0.001). Expt. III involved 56 subjects; all received 8% of energy from stearic acid, from linoleic acid, or from trans-monounsaturates, for 3 weeks each. All other nutrients were equal.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of fatty acids on aflatoxin production byAspergillus parasiticus

The effect of saturated and unsaturated fatty acids on aflatoxin production was studied in a synthetic medium. The aflatoxin production decreased (10-75%) in the presence of lauric acid and palmitic acid but the addition of behenic and sebacic acid stimulated aflatoxin production by 125-541%. Linolenic and linoleic acids effected aflatoxin production and mycelium growth. An 34-fold increase in aflatoxin production was observed with 50 mM linoleic acid. An inverse relationship was observed between aflatoxin production and mycelium mass, irrespective of the nature of the fatty acid.     

CHANGES IN PHOSPHOGLYCERIDE FATTY ACIDS OF RAT BRAIN INDUCED BY LINOLEIC AND LINOLENIC ACIDS AFTER PRE- AND POST-NATAL FAT DEPRIVATION

Abstract— Pregnant rats were maintained on a fat-free diet, starting at 10–12 days after impregnation and the offspring continued on the diet during a developmental period of 120 days. Brain fatty acids showed decreases in the level of (n-3) and (n-6) fatty acids of brain phophoglycerides, except for 22:5 (n-6) which increased. These changes preceded an increase in the (n-9) fatty acids (20:3 and 22:3). Supplementation with either linoleic or linolenic acid for 10 or 30 days after induction of the deficiency state caused an increase in the (n-6) and (n-3) fatty acids respectively, to control levels. The level of 22:5 (n-6) was increased additionally by linoleic supplementation while linolenic refeeding to deficient animals decreased 22:5 (n-6) to near control levels. The anomalous results obtained on 22:5 (n-6) with 18:3 (n-3) supplementation is attributed to competitive inhibition of linoleate desaturation by linolenate. Linoleic and linolenic acid were equally effective in reducing the elevated levels of the (n-9) fatty acids toward control levels, although control levels with either fatty acid was not reached after 30 days supplementation. The increase of the (n-6) and (n-3) fatty acids to normal values precedes the decrease of (n-9) fatty acids following supplementation of linoleic or linolenic acid to fat-deficient rats. No change in fatty acid composition in control animals between 30 and 120 days was observed. In fat deficient as well as supplemented animals the total saturated, monounsaturated and polyunsatur-ated fatty acid composition was constant as was the unsaturation index.     

Effect of dietary fats on linoleic acid metabolism. A radiolabel study in rats

Effects on the linoleic acid metabolism in vivo of three dietary fats, rich in either oleic acid, trans fatty acids or alpha-linolenic acid, and all with the same linoleic acid content, were investigated in male Wistar rats. After 6 weeks of feeding, the rats were intubated with [1-14C]linoleic acid and [3H]oleic acid. The incorporation of these radiolabels into liver, heart and serum was investigated 2, 4, 8, 24 and 48 h after intubation. The amount of 14C-labelled arachidonic acid incorporated into the liver phospholipid of the group fed the oleic acid-rich diet was significantly higher than that of the other groups. However, compared to the trans fatty acids-containing diet, the oleic acid-rich diet induced only a slightly higher arachidonic acid level in the phospholipid fraction of the tissues as determined by GLC. Dietary alpha-linolenic acid more than halved the arachidonic acid levels. Our results do not support the hypothesis that the delta 6-desaturase system actually determines the polyunsaturated fatty acid levels in tissue lipids by regulating the amount of polyunsaturated fatty acids (e.g., arachidonic acid) synthesized. The biosynthesis of polyunsaturated fatty acids only is not sufficient to explain the complicated changes in fatty acid compositions as observed after feeding different dietary fats.