Quantitative effects of dietary polyunsaturated fats on the composition of fatty acids in rat tissues

A method combining data on fatty acid composition into subsets is used to illustrate general relative competitive selectivities in the metabolic and transport events that maintain fatty acid compositions in tissue lipids and to minimize differences among tissues or species in the amount of individual fatty acids. Fatty acid compositions of triglycerides and phospholipids in several tissues of the rat were maintained with simple relationships between the exogenous n−3 and n−6 dietary polyunsaturated fatty acids and the endogenous n−7 and n−9 types of fatty acid. The general pattern of fatty acids in triglycerides was similar for liver, plasma and adipose tissue, averaging about 30% as saturated acids, 67% as 16- and 18-carbon unsaturated acids and only about 2% as 20- and 22-carbon highly unsaturated acids. The tissues maintained a linear relationship between the amount of 18-carbon polyunsaturated fatty acids in the diet and in the tissue triglycerides, with the proportionality constant for 18∶3n−3 being 60% of that for 18∶2n−6. The total phospholipids of liver, plasma and red blood cells maintained about 45% of the fatty acids in the form of saturated fatty acids and 20–30% as 20- and 22-carbon highly unsaturated fatty acids irrespective of very different proportions of n−3, n−6 and n−9 types of fatty acids. In all three tissues, the 20-carbon highly unsaturated fatty acids of the n−3, n−6 and n−9 type were maintained in a competitive hyperbolic relationship with apparent EC₅₀ values for dietary 18∶2n−6 and 18∶3n−3 near 0.1% of dietary calories. The consistent quantitative relationships described in this study illustrate an underlying principle of competition among fatty acids for a limited number of esterification sites. This approach may be useful in predicting the influence of diet upon tissue levels of the substrates and antagonists of eicosanoid biosynthesis.     

Fatty acid composition of rat hearts as influenced by age and dietary fatty acids

Fatty acid composition of neutral and polar lipid fractions from rat hearts was determined in rats of different ages as their diet source changed. Piebald rats were weaned at 21 days and were fed standard lab chow. Lipids from rat hearts, mothers milk and lab chow were purified on a Sephadex G-25 fine column and separated into neutral and polar lipid fractions by silicic acid column chromatography. These lipid fractions were then hydrolyzed and methylated with BF₃ in methanol, prior to gas liquid chromatographic separation on a 1/8 in. × 10 ft aluminum column of 15% EGS on 80–100 mesh acid-washed Chromosorb W. Three major fatty acids in the neutral lipid fraction comprised 72% of total neutral lipid fatty acids from young hearts. At sexual maturity (at least 74 days old) C_18∶1 was the major fatty acid, followed by C_16∶0 and C_18∶0. The same three fatty acids comprised 83% of total polar lipid fatty acids, but C_18∶0 was the major fatty acid, followed by C_16∶0 and C_18∶1. The fatty acid composition of dietary lipids influenced the total neutral lipid fatty acid composition of the rat heart, but had little influence on the fatty acid composition of the polar lipid fraction. Presented in part at the AOCS Meeting, New Orleans, April 1970.     

Dietary Linseed Oil Reduces Growth While Differentially Impacting LC-PUFA Synthesis and Accretion into Tissues in Eurasian Perch (Perca fluviatilis)

The aim of this study was to evaluate the impact of replacing dietary fish oil (FO) with linseed oil (LO) on growth, fatty acid composition and regulation of lipid metabolism in Eurasian perch (Perca fluviatilis) juveniles. Fish (17.5 g initial body weight) were fed isoproteic and isoenergetic diets containing 116 g/kg of lipid for 10 weeks. Fish fed the LO diet displayed lower growth rates and lower levels of DHA in the liver and muscle than fish fed the FO diet, while mortality was not affected by dietary treatment. However, DHA content recorded in the liver and muscle of fish fed the LO diet remained relatively high, despite a weight gain of 134 % and a reduced dietary level of long‐chain polyunsaturated fatty acids (LC‐PUFA), suggesting endogenous LC‐PUFA biosynthesis. This was supported by the higher amounts of pathway intermediates, including 18:4n‐3, 20:3n‐3, 20:4n‐3, 18:3n‐6 and 20:3n‐6, recorded in the liver of fish fed the LO diet in comparison with those fed the FO diet. However, fads2 and elovl5 gene expression and FADS2 enzyme activity were comparable between the two groups. Similarly, the expression of genes involved in eicosanoid synthesis was not modulated by dietary LO. Thus, the present study demonstrated that in fish fed LO for 10 weeks, growth was reduced but DHA levels in tissues were largely maintained compared to fish fed FO, suggesting a physiologically relevant rate of endogenous LC‐PUFA biosynthesis capacity.     

The composition and metabolism of developing brown and white fats

This investigation was concerned with analysis of the composition and metabolism of developing adipose tissues in the postnatal hamster. Particular attentions were given to the development of brown fat and the relationship of brown and white fats to each other. Correlations with previous histological studies are stressed. The parameters studied were water content, total lipid content, glycogen content, fatty acid compositions of total lipid extracts, malic dehydrogenase activity as assayed from oxaloacetate to malate, glucose-6-phosphate dehydrogenase activity and aldolase activity. One of nine papers to be published from the Symposium “Brown Adipose Tissue,” presented at the AOCS-AACC Joint Meeting, Washington, D.C., March 1968.     

Modulation of cutaneous fatty acid-binding protein mRNA expression in rat adipose tissues by hereditary obesity and dietary fats

Cutaneous fatty acid-binding protein (C-FABP) is a member of the intracellular lipid-binding protein multigene family expressed in various tissues. A high level of C-FABP mRNA in adipose tissue has been reported, but its physiological significance in regulating adipose tissue function is not clear. To obtain insights into the role of C-FABP in adipose tissue, we studied the obesity-related and dietary fat-related changes of C-FABP mRNA expression in adipose tissues. C-FABP mRNA levels in interscapular brown adipose tissue, and epididymal and perirenal white adipose tissues were higher in Zucker fatty rats than in lean controls despite that the difference in brown adipose tissue was not significant. Fish oil compared to palm and safflower oils significantly reduced the mRNA level of C-FABP in brown adipose tissue and epididymal and perirenal white adipose tissues in Sprague-Dawley rats except for one occasion. Our study demonstrated that C-FABP is a protein whose mRNA expression is easily modified by hereditary obesity and the type of dietary fat. Therefore, C-FABP may play a significant role in regulating adipocyte function in response to changes in nutritional conditions.     

Influence of dietary long-chain PUFA on premature baboon lung FA and dipalmitoyl PC composition

One of the major survival challenges of premature birth is production of lung surfactant. The lipid component of surfactant, dipalmitoyl PC (DPPC), increases in concentration in the period before normal term birth via a net shift in FA composition away from unsaturates. We investigated the influence of dietary DHA and arachidonic acid (AA) on lung FA composition and DPPC concentration in term and preterm baboons. Pregnant animals/neonates were randomized to one of four groups: breast-fed (B), term formula-fed (T⁻), preterm formulafed (P⁻), and preterm fed formula supplemented with DHA-AA (P⁺). Breast milk contained 0.68%wt DHA and the P⁺ group formula contained 0.61%wt DHA. In the preterm groups (P⁻ and P⁺), pregnant females received a course of antenatal corticosteroids. At the adjusted age of 4 wk, neonate lung tissue was harvested, and FA composition and DPPC were analyzed. Palmitate was ∼28%wt of lung total FA and no significant differences were found among the four treatment groups. In contrast, DPPC in the B group lung tissue was significantly greater than DPPC in the unsupplemented groups, but not compared with the P⁺ group. The B and P⁺ groups were not significantly different in DHA and AA, but were different compared with the unsupplemented (T, P⁻) groups. These results indicate that LCP supplementation increases lung DHA and AA, without compromising overall lung 16∶0 or DPPC. The shift in FA composition toward greater unsaturation in the groups consuming LCP supported improved surfactant lipid concentration in preterm neonate lungs.     

Determination of FA composition and total trans FA of Turkish margarines by capillary GLC

In this research, FA composition and total trans FA contents of 16 different brands of margarine (8 hard-type and 8 soft-type) sold in Turkey were determined by capillary GLC method. According to the results, the contents of saturated FA, monounsaturated FA, and PUFA were within the ranges of 23.9–32.3, 44.0–61.9, and 14.2–24.1%, respectively, in hard-type margarines, and 27.0–39.9, 21.0–40.9, and 32.0–53.7%, respectively, in soft-type margarines. Hard-type margarines contained total trans FA concentrations of 20.1–34.3%, whereas soft-type margarines contained less than 8.9% total trans FA. C_18∶1 trans acid content was within the range of 18.5–29.8% in hard-type margarines, and it was significantly higher than the range in soft margarines (0.7–8.1%). C_18∶1 trans acid was the major trans FA in all margarines, and C_18∶3 trans acid concentrations were less than 0.2%.     

Effects of dietary fats on prostanoid production and aortic and plasma fatty acid composition in rats

Male Sprague-Dawley rats were fed diets with 10%, 30%, or 50% of energy derived from fat for two weeks. The fats used were beef tallow, olive oil, peanut oil and butter. Aortic prostacyclin (PGI₂) production, platelet aggregation and thromboxane A₂ (TXA₂) production and plasma and aortic phospholipid (PL) content were measured. Butter- and beef tallow-feeding reduced aortic PGI₂ production and collagen-induced TXA₂ production in a dosedependent manner as the level of fat in the diet increased. Neither olive oil nor peanut oil had any effect on aortic PGI₂ production or collagen-induced TXA₂ production. Butter-feeding also resulted in a decrease in collageninduced platelet aggregation; however, none of the other fats had any effect on collagen-induced platelet aggregation. The observed decreases in aortic PGI₂ and collagen-induced TXA₂ production were paralleled by similar decreases in aortic and plasma PL arachidonic acid content and an increase in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Only the most saturated fats, butter and beef tallow, had significant inhibitory effects on prostanoid production and platelet aggregation.     

Glyceride composition of processed fats and oils as determined by glass capillary gas chromatography

Refined and bleached fats and oils can be analyzed directly by high-temperature glass capillary column gas chromatography after derivatization of the fatty acids, mono- and diglycerides with BSTFA [(N,O)-bis(trimethyl silyl) trifluoroacetamide]. The intact glycerides are separated on the basis of volatility to provide characteristic carbon number profiles (CNP). Quantitative information on mono-, di- and triglycerides, as well as free fatty acids, is obtained from a single, rapid separation. Profile values are reported for 13 different processed fats and oils. The analysis performed in the split-injection mode maintains column integrity after numerous separations, while producing acceptable relative standard deviations.     

Changes in the chemical composition of surfactant-like particles secreted by rat small intestine in response to different dietary fats

Consumption of dietary oil, viz., corn, fish, coconut, or olive, induced the secretion of surfactant-like particles (SLP) in rat intestine. These lipoprotein particles differ in (i) levels of alkaline phosphatase activity, (ii) lipid composition, and (iii) FA composition in response to feeding of different oils. The secreted particles had similar buoyancy (1.07–1.08 g/mL) and cholesterol/phospholipid molar ratios (0.61–0.72) except that feeding coconut oil to rats produced SLP with a low (0.18) cholesterol/phospholipid molar ratio compared to control animals. It is concluded from these observations that feeding different oils induces the secretion of lipoprotein particles in rat intestine with different chemical compositions.     

Effects of dietary fats on fatty acid composition and Δ5 desaturase in normal and diabetic rats

We have studied the effect of various diets on the phospholipid fatty acid composition andin vitro Δ5 desaturase activity of hepatic microsomes derived either from the normal or streptozotocin-induced diabetic rat. The diets studied were the standard rat chow diet and a basal fat-free diet supplemented either with 20 percent saturated fat, 20 percent unsaturated fat, or 20 percent menhaden oil. Phospholipid fatty acid composition analysis revealed that the normal rat fed the saturated fat or menhaden oil diet had significantly decreased arachidonate levels, consistent with decreased Δ5 desaturase activities and decreased 18∶2n−6 intake. On the contrary, the unsaturated fat diet decreased dihomo-γ-linolenate and increased arachidonate levels, without increased Δ5 desaturase activity. Streptozotocininduced diabetes resulted in decreased arachidonate and Δ5 desaturase activity. The unsaturated fat diet fed to the diabetic rat also failed to correct this decreased Δ5 desaturase activity. The unsaturated fatty acids in this diet also displaced a substantial amount of n−3 fatty acids in both normal and diabetic microsomes, due to the competition between these two fatty acid families for incorporation into the membrane phospholipids. Conversely, the menhaden oil diet fed to the normal and diabetic rats displaced n−6 fatty acids, reduced Δ5 desaturase activity, and enhanced 22∶6n−3 incorporation into diabetic microsomes.     

Turnover of bile acids in the hypercholesterolemic rat as influenced by saturation of dietary fat

Injections of [24-¹⁴C] chenodeoxycholate and³H-cholate were made by heart puncture into 300 g male rats that bore T-cannulas in their bile ducts. The animals had been raised on diet A, containing glucose, cholesterol and cholate, or diet B, containing sucrose and cholesterol; each of the diets contained 5% safflower oil or 5% beef tallow as variables. From analysis of bile samples collected from the T at intervals over a 5 day period, it was observed that the safflower oil group fed diet B had a 17% shorter cholate half-life, a 29% larger cholate pool size and 52% higher rate of cholate synthesis than those fed beef tallow in the same diet. The safflower group fed diet A also had a larger cholate pool size, but synthesis and half-life were obscured by cholate feeding. Chenodeoxycholate turnover data were not obtainable because the decay curves were bimodal for all treatments and hence did not conform to a simple pool model. It is concluded that dietary safflower oil causes more rapid formation of cholate than does dietary beef tallow in the cholesterol-fed rat. Journal Paper No. 4952 AES, Purdue University.     

Sterol composition ofPhaeodactylum tricornutum as influenced by growth temperature and light spectral quality

In a detailed sterol analysis of the marine diatomPhaeodactylum tricornutum, free sterols as well as esterified and glycosylated conjugates were found. When the alga was grown under standard conditions (i.e., at 13°C under white light), 64% of total sterols were steryl glycosides. In all sterol classes, except steryl esters, (24S)-24-methylcholesta-5,22E--dien-3β-ol (epibrassicasterol) was the major (80 to 99%) sterol component. Eight other sterols were identified. Growth under different light spectral quality (red, blue, yellow, and green) at 13 and 23°C was examined. At 23°C, a dramatic decrease in total sterol content was observed, especially under blue light. The distribution of sterols between free and conjugated forms as well as sterol profile inside each class was found to be strongly dependent on the light spectral quality at both temperatures.     

Modulation of cyclic nucleotide phosphodiesterase by dietary fats in rat heart

Feeding oils of different fatty acid composition modifies the fatty acid composition of cardiac membrane phospholipids, thereby inducing changes in cardiac contractility and altering response of adenylate cyclase to catecholamines. In the present study, the effect of such dietary manipulations on cyclic nucleotide phosphodiesterase, which is involved in the control of cyclic nucleotide intracellular levels and in the control of cardiac contractility, was investigated. Rats were fed either a saturated fatty acid-enriched diet (8 weight percent [%] coconut oil +2% sunflower oil), an n−6 fatty acid-enriched diet (10% sunflower oil) or an n−3 fatty acid-enriched diet (8% fish oil +2% sunflower oil). The fatty acid composition of cardiac phospholipids, as well as the nonesterified fatty acid content of heart were markedly altered by the diets. The 18∶2n−6 and 20∶4n−6 content of cardiac phospholipids was markedly (−49%) depressed by fish oil as compared with sunflower oil feeding, but the nonesterified fatty acid level of heart membrane was lowest in coconut oil-fed rats. In addition, fish oil feeding more drastically depressed the n−6/n−3 fatty acid ratio in the nonesterified fatty acid pool than in cardiac phospholipids. Cyclic AMP phosphodiesterase activity was the lowest in both the particulate and soluble fractions of heart from rats fed sunflower oil, whereas cyclic GMP phosphodiesterase activity was not altered by the diets. Cyclic AMP phosphodiesterase activity was decreased by 18 and 12% in heart membranes of the sunflower oil group as compared to that of the coconut oil and fish oil groups, respectively. In heart cytosol, the activity decreased by 30% when compared with the activity of the coconut oil group. Additionalin vitro experiments showed that polyunsaturated fatty acids were more potent inhibitors of cyclic AMP phosphodiesterase than saturated fatty acids. These results suggest that polyunsaturated fatty acid-enriched diets might decrease heart cyclic AMP phosphodiesterase activity by increasing non-esterified polyunsaturated fatty acids, especially those of the n−6 series, but more complex and indirect mechanisms are very likely to be involved.     

Fertility and testicular fatty acid composition in the chicken as influenced by vitamin E and ethoxyquin

The fatty acid composition of testicular lipids has been determined and related to fertility data from groups of dubbed White Leghorn cockerels after a 50-week feeding period on rations containing 10% safflower oil or coconut oil. Supplements of ethoxyquin ord-α-tocopherol acetate maintained fertility in birds raised on rations containing safflower oils. This response was associated with higher proportions of 22∶4 ω6 and lower proportions of 18∶2 ω6 in testicular lipids. Testes size was quite variable in the unsupplemented group with changes in fatty acid composition being more pronounced in the smaller testes. A multiple regression was calculated using data from those birds on the safflower oil ration. With a correlation ratio of 0.90 fertility was expressed as a function of testes size, semen concentration and the proportions of 18∶2 ω6, 20∶4 ω6 and 22∶4 ω6 in testicular lipids. Despite the low intake of linoleate significant levels of polyunsaturated fatty acids were maintained in testicular lipids of birds fed the coconut oil rations. The major changes in fatty acid composition of testicular lipids produced by this variable was a decrease in the proportion of 18∶2 ω6 and an increase in the proportion of 18∶1. Paper No. 3050, Oregon Agricultural Experiment Station.     

Fate of dietary sterols in hydrogenated oils and fats

Samples of table margarines, so-called polyunsaturated table margarines, hydrogenated vegetable oils, and so-called polyunsaturated hydrogenated vegetable oils were shown by infrared spectroscopy to contain hydrogenated components. Examination of the sterols from these oils by argentation thin layer chromatography and gas liquid chromatography did not reveal campestanol, stigmastanol, or Δ²²-stigmastenol, the expected hydrogenation products of the natural sterols. The sterol compositions of the above samples, animal fats, and blends of hydrogenated vegetable oils and animal fats were determined. The compound 24-methyl cholest-7-en-3β-ol was identified tentatively in sunflower and safflower oils.     

Fatty acid composition of corn endosperm and germ oils as influenced by different extraction procedures

Gas liquid chromatography was used to determine fatty acid composition of oil obtained from corn (Zea mays L.) inbred lines by different extraction procedures. Kernels were separated into endosperm and germ fractions for nine inbreds which had a considerable range in fatty acid composition of oil. Oil obtained from the endosperm by different extraction procedures was significantly different in composition for all fatty acids. Oil obtained from the germ by different extraction procedures was similar in fatty acid composition. The differences in response of endosperm and germ oils to extraction procedures were attributed to the type of lipid found in each fraction. It was concluded that choice of extraction procedures was of little importance in studies of oil from the corn germ, but that specific extraction procedures must be recognized as a factor when studying oil composition of the endosperm. Approved as Journal Series Paper No. 696, University of Georgia, College of Agriculture Experiment Stations.     

Prevention of cholesterol cholelithiasis by dietary unsaturated fats in hormone-treated female hamsters

We examined the effect of diet on gallstone incidence and the composition of biliary phosphatidylcholines in methyltestosterone-treated female hamsters. These hamsters were fed a nutritionally adequate purified lithogenic diet containing 2% corn oil, 4% butterfat, 0.3% cholesterol, and 0.05% methyltestosterone, resulting in a cholesterol gallstone incidence of 86%. This incidence was lowered when mono-and polyunsaturated fats or fatty acids were added to the diet: 2.5% oleic acid resulted in total prevention of cholesterol cholelithiasis, 2.5% linoleic acid, and 4% safflower oil (78% linoleic acid content) reduced gallstone incidence to 26 and 8%, respectively. An additional 4% butterfat (29% oleic acid content) produced gallstones in 50% of the animals. At the end of the 6-wk feeding period, the bile of all hamsters was supersaturated with cholesterol. The major biliary phosphatidylcholine species in all groups were (sn-1-sn-2): 16:0–18:2, 16:0–18:1, 18:0–18:2, 16:0–20:4, and 18:2–18:2. The safflower oil-and linoleic acidfed hamsters exhibited an enrichment of 16:0–18:2 (16–18%); added butterfat or oleic acid increased the proportion of 16:0–18:1 (9 and 25%, respectively). We conclude that the phosphatidylcholine molecular species in female hamster bile can be altered by dietary fats/fatty acids and that mono-and polyunsaturated fatty acids play a role in suppressing the induced cholelithiasis.     

Fatty acid composition as a basis for identification of commercial fats and oils

Gas liquid chromatographic analyses of 200 samples of commercial fats and oils were compared to the standard ranges specified by the Food and Agriculture Organization/World Health Organization Codex Alimentarius Committee on Fats and Oils at its seventh session, London, England, March 25, 1974. Only six samples fell notably outside the standard ranges. On the basis of this information, the U.S. delegation is offering for consideration by the Committee at its next meeting a method for using the fatty acid composition of a fat or oil to determine its authenticity.