The effect of dietary fats on the plasma lipid composition of sheep

This study reports on the plasma lipid compositions of sheep fed either a control diet (C), a control diet supplemented with tallow (A) or polyunsaturated fatty acid (B) that had been protected against hydrolysis and hydrogenation in the rumen, or a control diet supplemented with maize oil (D). Diet B considerably increased the 18∶2 content of all the major plasma lipid fractions. Although the feeding of diet D also resulted in an increase in the 18∶2 contents within the cholesteryl ester, unesterified fatty acid, and phospholipid fractions the increases were considerably less than those observed with diet B; the levels of 18∶2 within the triglyceride fraction remained similar to that for the sheep which received the control diet. The effect of feeding diet A was confined solely to the triglyceride fraction where the concentrations of 16∶0 and 18∶1 were increased. The lipoproteins of the plasma were separated into very low density lipoproteins (d<1.006), low density lipoproteins (1.006<d<1.063), and high density lipoproteins (1.063<d<1.21), and the distribution of the major lipids between these lipoprotein fractions was investigated. Diet B increased considerably the proportion of triglyceride found in association with the very low density fraction and the concentrations of 18∶2 within all the lipoprotein fractions; these increases in the concentrations of 18∶2 were not confined to any particular lipid fraction of the lipoproteins. In contrast, the increases in the concentrations of 18∶2 produced as a result of feeding diet D were confined to the low and high density lipoproteins. The effect of feeding diet A was confined to fatty acid changes within the triglycerides of the low and very low density lipoproteins.     

Effects of cyclopropene fatty acids on the lipid composition of the Morris hepatoma 7288C

Fatty acids ofSterculia foetida were added to the medium used to maintain the Morris hepatoma 7288C in culture. The effect of this supplement on the lipid composition was examined. Overall, monoene levels were decreased with 18∶1 levels reduced by 40%. Saturated fatty acid levels were increased, with stearate (18∶0) levels 220% of control values. No effect occurred on the level of polyunsaturates (18∶2, 20∶4, 22∶5, 22∶6). These changes in fatty acid makeup were observed in both neutral and phospholipid fractions, and all lipid classes were affected. Triglycerides were most affected with a 66% decrease in 18∶1. There appeared to be little specificity of effect in the phospholipids with 18∶1 levels decreased 40–60% in all classes. All classes were therefore dependent on an endogenous supply of 18∶1. Examination of the distribution of geometrical isomers of 18∶1 reveals that in all lipid classes, except diphosphatidylglycerol (DPG), the ratio of Δ11 to Δ9 isomer decreased toward the isomeric distribution displayed by total medium lipids. In DPG, although 18∶1 levels were lowered, the isomeric distribution increased. DPG, synthesized and found in the mitochondria, may use a separate pool of 18∶1 during synthesis. Cyclopropene fatty acids (sterculic and malvalic) were incorporated into both neutral and phospholipid fractions with preferential incorporation into triglycerides. Cyclopropene fatty acids were not selectively incorporated into any phospholipid species. Sphingomyelin did not incorporate cyclopropene fatty acids, indicating that a different class of acyltransferase is used in the formation of this phospholipid class.     

Distribution of deuterium-labeledcis-andtrans-12-octadecenoic acids in human plasma and lipoprotein lipids

Triglycerides containingcis- andtrans-12-octadecenoic acid (12c-18∶1 and 12t-18∶1) andcis-9-octadecenoic acid (9c-18∶1) labeled with deuterium were fed to 2 young adult male subjects. These fatty isomers each contained a different number of deuterium labels, which allowed mass spectrometric analysis to distinguish among them after they were fed as a mixture. This approach results in a direct comparison of the absorption and distribution of these 3 monoenoic acids into blood plasma and lipoprotein lipids. Plasma lipid data indicated that all phospholipid fractions selectively incorporate 12c-18∶1 and 12t-18∶1 in preference to 9c-18∶1. Discrimination against 12c-18∶1 and 12t-18∶1 compared to 9c-18∶1 was found in the plasma neutral lipids, with a strong discrimination against 12t-18∶1 incorporation into the cholesteryl ester fraction. Considerable reduction in the percentage of linoleic and arachidonic acid was observed when 12–18∶1 isomers were incorporated in plasma triglyceride, phosphatidylcholine and sphingomyelin samples. Chylomicron lipid analyses indicated that all isomers were well absorbed. Variation was observed in the relative distribution of 12c-18∶1, 12t-18∶1 and 9c-18∶1 between the very low density, low density and high density lipoprotein lipid classes. No desaturation of 12c-18∶1 to linoleic acid was detected.     

The effect of dietary fat level and quality on plasma lipoprotein lipids and plasma fatty acids in normocholesterolemic subjects

This study examined the effect on the plasma lipids and plasma phospholipid and cholesteryl ester fatty acids of changing from a typical western diet to a very low fat (VLF) vegetarian diet containing one egg/day. The effect of the addition of saturated, monounsaturated or polyunsaturated fat (PUFA) to the VLF diet was also examined. Three groups of 10 subjects (6 women, 4 men) were fed the VLF diet (10% energy as fat) for two weeks, and then in the next two weeks the dietary fat in each group was increased by 10% energy/week using butter, olive oil or safflower oil. The fat replaced dietary carbohydrate. The VLF diet reduced both the low density lipoprotein (LDL)-and high density lipoprotein (HDL)-cholesterol levels; addition of the monounsaturated fats and PUFA increased the HDL-cholesterol levels, whereas butter increased the cholesterol levels in both the LDL- and HDL-fractions. The VLF diet led to significant reductions in the proportion of linoleic acid (18∶2ω6) and eicosapentaenoic acid (20∶5ω3) and to increases in palmitoleic (16∶1), eicosatrienoic (20∶3ω6) and arachidonic acids (20∶4ω6) in both phospholipids and cholesteryl esters. Addition of butter reversed the changes seen on the VLF diet, with the exception of 16∶1, which remained elevated. Addition of olive oil resulted in a significant rise in the proportion of 18∶1 and significant decreases in all ω3 PUFA except 22∶6 compared with the usual diet. The addition of safflower oil resulted in significant increases in 18∶2 and 20∶4ω6 and significant decreases in 18∶1, 20∶5ω3 and 22∶5ω3. These results indicate that the reduction of saturated fat content of the diet (<6% dietary energy), either by reducing the total fat content of the diet or by exchanging saturated fat with unsaturated fat, reduced the total plasma cholesterol levels by approximately 12% in normocholesterolemic subjects. Although the VLF vegetarian diet reduced both LDL- and HDL-cholesterol levels, the long-term effects of VLF diets are unlikely to be deteterious since populations which habitually consume these diets have low rates of coronary heart disease. The addition of safflower oil or olive oil to a VLF diet produced favorable changes in the lipoprotein lipid profile compared with the addition of butter. The VLF diets and diets rich in butter, olive oil or safflower oil had different effects on the 20 carbon eicosanoid precursor fatty acids in the plasma. This suggests that advice on plasma lipid lowering should also take into account the effect of the diet on the fatty acid profile of the plasma lipids.     

Effects of a (n−3) polyunsaturated fatty acid-deficient diet on profiles of serum vitellogenin and lipoprotein in vitellogenic trout (Salmo gairdneri)

During the 6 months of vitellogenesis, 3-year-old female trout (Salmo gairdneri) were fed either an enriched (E) or an (n−3) polyunsaturated fatty acid (PUFA)-deficient (D) diet; serum vitellogenin (VG) and lipoproteins (d<1.21 g/ml) were analyzed at the third month of vitellogenesis (September) and at ovulation (December). The serum content of high density lipoproteins (HDL), the major protein class, maintained a mean value of 1500 mg/dl at both stages and with both diets. On the contrary, very low density lipoproteins (VLDL) were 90% higher during vitellogenesis than at spawning time, whereas excess vitellogenin circulated at this period (6580 mg/dl serum with diet E). The diet deficient in (n−3) lowered serum vitellogenin content by 16% in September and by 26% in December. The degree of (n−3) PUFA incorporation moderately decreased in low density lipoproteins (LDL) and in HDL with the (n−3)-deficient diet. The effect was more pronounced for 20∶5. On the other hand, essential 22∶6 was incorporated into vitellogenin at the same rate in September as in December with diet E (23% and 25%, respectively), whereas after a 3-month deficiency, the percentage fell to 12%; this percentage rose again to 19% at spawning time. These findings show that, although stored (n−3) PUFA were not exhausted after a 6-month dietary deficiency, the incorporation of essential fatty acids (EFA) into vitellogenin during the early stages of oogenesis was low, suggesting changes in egg composition that may influence hatching.     

Lipoprotein composition and serum cholesterol ester fatty acids in nonwesternized melanesians

In this study, the relationships between dietary fat [as measured by serum cholesterol ester fatty acids (CE-FA)], age, smoking, body mass index, and serum lipids were analyzed in 151 subsistence horticulturalists, aged 20–86 yr, from Kitava, Trobriand Islands, Papua New Guinea. Their diet consists of tubers, fruit, coconut, fish, and vegetables with a negligible influence of western food and alcohol. Total fat intake is low [21% of energy (en%)], while saturated fat intake from coconuts is high (17 en%, mainly lauric and myristic acid). In multivariate analysis, 11–43% of the variation of the serum lipoprotein composition was explained by CE-FA, age, and smoking habits. The proportion of CE20∶5n-3 explained much of the variation of triglycerides (TG, negative relation) and high density lipoprotein-cholesterol (HDL-C, positive) in both sexes and serum apolipoprotein A1 (ApoA1, positive) in the males. CE16∶0 was positively related to TG and negatively related to HDL-C and ApoA1 in both sexes, and in males it related negatively to total cholesterol (TC) and low density lipoprotein-cholesterol (LDI-C). In males, negative relationships were present between CE18∶2n-6 and TC and between CE14∶0 and serum lipoprotein(a). Smoking was independently associated with lower ApoA1 in both sexes and with lower HDL-C and higher TG, TC, LDL-C, and apolipoprotein B in males. In conclusion, marine n-3 fatty acids and linoleic acid showed the same potentially beneficial relationships with lipoproteins and apolipoproteins as in western populations. The relations of palmitic acid to serum lipids may be explained in terms of endogenous fat synthesis at a low-fat intake, rather than reflecting its relative intake.     

Phospholipid synthesis by chick retinal microsomes: Fatty acid preference and effect of fatty acid binding protein

The acylation of 1-palmitoyl-sn-glycerophosphocholine (1-16∶0-GPC) or 1-palmitoyl-sn-glycerophosphoethanolamine (1-16∶0-GPE) was measured using the microsomal fraction prepared from retinas of 14–15-day-old chick embryos. Rates of incorporation of exogenously supplied fatty acids into diacyl-GPC were generally 5–7 times greater than into diacyl-GPE. Substrate preferences for incorporation into diacyl-GPC and diacyl-GPE were, respectively, 18∶2>18∶3=20∶5>20∶4>18∶1>22∶6=18∶0 and 18∶2>22∶6≽18∶3=18∶0≽20∶4=18∶1>20∶5. The apparent selectivities were not consistent with the reported fatty acid compositions of these lipid classes. The addition of partially purified fatty acid binding protein (FABP) to the reaction had no effect either on overall rates of incorporation or on the substrate preference. When fatty acyl-CoA substrates were used, rates of incorporation of the 18∶0 derivative were much higher than with the fatty acid, while rates with other fatty acyl-CoA were similar to those with the respective fatty acid. Substrate preferences for CoA derivatives incorporated into diacyl-GPC were: 18∶0>20∶4>18∶2≽22∶6, and into diacyl-GPE: 20∶4=22∶6>18∶0>18∶2. Polyunsaturated fatty acyl CoA (PUFA-CoA) were thus favored for incorporation into diacyl-GPE, and to a lesser extent into diacyl-GPC, a result that is consistent with composition data. When purified FABP was added to the reactions, there was an increase in the incorporation of 18∶0-CoA and a decrease or no change in the incorporation of PUFA-CoA. The deacylation/reacylation cycle thus appears to play a role in the modification of phospholipid composition. The data are not consistent, however, with a role for FABP in directing PUFA toward membrane lipid synthesis.     

Myocardial changes in newborn piglets fed sow milk or milk replacer diets containing different levels of erucic acid

This study was undertaken to determine whether the neonate was more susceptible to the effects of dietary erucic acid (22∶1n−9) than the adult. Newborn piglets were used to assess the safety of different levels of 22∶1n−9 on lipid and histological changes in the heart. Newborn piglets showed no myocardial lipidosis as assessed by oil red 0 staining, but lipidosis appeared with consumption of sow milk and disappeared by seven days of age. Milk replacer diets containing soybean oil, or rapeseed oil mixtures with up to 5% 22∶1n−9 in the oil, or 1.25% in the diet, gave trace myocardial lipidosis. Rapeseed oil mixtures with 7 to 42.9% 22∶1n−9 showed definite myocardial lipidosis in newborn piglets, which correlated to dietary 22∶1n−9, showing a maximum after one week on diet. The severity of the lipidosis was greater than observed previously with weaned pigs. There were no significant differences among diets in cardiac lipid classes except for triacylglycerol (TAG), which increased in piglets fed a repeseed oil with 42.9% 22∶1n−9. TAG showed the highest incorporation of 22∶1n−9, the concentration of 22∶1n−9 in TAG was similar to that present in the dietary oil. Among the cardiac phospholipids, sphingomyelin and phosphatidylserine had the highest, and diphosphatidylglycerol (DPG) the lowest level of 22∶1n−9. The low content of 22∶1n−9 in DPG of newborn piglets is not observed in weaned pigs and rats fed high erucic acid rapeseed oil. The relative concentration of saturated fatty acids was lowered in all cardiac phospholipids of piglets fed rapeseed oils, possibly due to the low content of saturated fatty acids in rapeseed oils. The results suggest that piglets fed up to 750 mg 22∶1n−9/kg body weight/day showed no adverse nutritional or cardiac effects.     

Plasma lipids are affected similarly by dietary lauric or palmitic acid in gerbils and monkeys

To compare the relative impact of dietary lauric acid (12∶0) and palmitic acid (16∶0) on plasma lipids, two fat-sensitive species, Mongolian gerbils and cebus monkeys, were fed cholesterol-free, purified diets enriched with either 12∶0-rich or 16∶0-rich fats, while all other fatty acids were held constant by selective blending of up to five natural fats or oils. The two gerbil diets (40 en% from fat) allowed for an 8 en% exchange between 12∶0 and 16∶0, and the monkey diets (31 en% from fat) allowed for 6 en% exchange beteen these two fatty acids. Eight gerbils received the diets for eight weeks, and 12 cebus monkeys were fed each diet in a cross-over design for up to 22 wk. Both diets resulted in similar plasma cholesterol, triglyceride, and high density lipoprotein cholesterol concentrations within each species. Additionally, separation of cebus lipoproteins by discontinuous density-gradient ultracentrifugation failed to show any dietary differences in concentration or composition of the three major lipoprotein classes (d<1.019, 1.019–1.055, and 1.055–1.168 g/mL). Thus, in two species sensitive to manipulations in dietary fat while consuming cholesterol-free diets, 16∶0 was not hypercholesterolemic relative to 12∶0. Based on a paper presented at the PORIM International Palm Oil Congress (PIPOC) held in Kuala Lumpur, Malaysia, September 1993.     

Lipid components and enzymatic hydrolysis of lipids in muscle of Chinese freshwater fish

The lipid and fatty acid composition of muscle of 10 species of freshwater fish obtained from a market of Shanghai City was examined. Total lipids (TL) ranged over 0.9–4.7% of muscle for all samples. The content of triacylglycerol (TG) in muscle ranged over 0.2–3.4% and that of polar lipids (PL) was 0.5–1.3%. Differences of TL content were dependent on TG contents. The predominant important fatty acids (>10% of the total fatty acids in TL) were 16∶0 and 18∶1n−9 with some 16∶1n−7, 18∶2n−6, and 22∶6n−3. The polyunsaturated fatty acids (PUFA) content was 10.2–43.4%, and especially Chinese sea bass contained above 20% of 22∶6n−3 in the total fatty acids. There were higher levels of PUFA such as 20∶5n−3 and 22∶6n−3 in PL than in neutral lipids. Muscle of the silver carp was stored at 20°C, and changes of lipid classes during storage were examined. Free fatty acids increased, and PL decreased during storage. This phenomenon was inhibited by heating the muscle, suggesting that lipid hydrolysis by phospholipase occurred in silver carp muscle.     

Lipid composition of the pineal organ from rainbow trout (Oncorhynchus mykiss)

The lipid composition of the pineal organ from the rainbow trout (Oncorhynchus mykiss) was determined to establish whether the involvement of this organ in the control of circadian rhythms is reflected by specific adaptations of lipid composition. Lipid comprised 4.9% of the tissue wet weight and triacylglycerols were the major lipid class present (47% of total lipid). Phosphatidylcholine (PC) was the principal polar lipid, and smaller proportions of other phospholipids and cholesterol were also present. Plasmalogens contributed 11% of the ethanolamine glycerophospholipids (EGP). No cerebrosides were detected. The fatty acid composition of triacylglycerols was generally similar to that of total lipids in which saturated, monounsaturated and polyunsaturated fatty acids (PUFA) were present in almost equal proportions. Each of the polar lipid classes had a specific fatty acid composition. With the exception of phosphatidylinositol (PI), in which 20∶4n−6 comprised 27.4% of the total fatty acids, 22∶6n−3 was the principal PUFA in all lipid classes. The proportion of 20∶5n−3 never exceeded 6.0% of the fatty acids in any lipid class. The predominant molecular species of PC were 16∶0/22∶6n−3 and 16∶0/18∶1, which accounted for 33.2 and 28.5%, respectively, of the total molecular species of this phospholipid. Phosphatidylethanolamine (PE) contained the highest level of di-22∶6n−3 (13.0%) of any phospholipid. There was also 4.9% of this molecular species in phosphatidylserine (PS) and 4.1% in PC. In PE, the species 16∶0/22∶6, 18∶1/22∶6 and 18∶0/22∶6 totalled 45.1%, while in PS 18∶0/22∶6 accounted for 43.9% of the total molecular species. The most abundant molecular species of PI was 18∶0/20∶4n−6 (37.8%). The lipid composition of the pineal organ of trout, and particularly the molecular species composition of PI, is more similar to the composition of the retina than that of the brain. Molecular species are abbreviated as follows: e.g., 16∶0/22∶6 PC is 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine.     

Lipid metabolism and tissue composition in Atlantic salmon (Salmo salar L.)—Effects of capelin oil, palm oil, and oleic acid-enriched sunflower oil as dietary lipid sources

Triplicate groups of Atlantic salmon (Salmo salar L.) were fed four diets containing different oils as the sole lipid source, i.e., capelin oil, oleic acid-enriched sunflower oil, a 1∶1 (w/w) mixture of capelin oil and oleic acid-enriched sunflower oil, and palm oil (PO). The β-oxidation capacity, protein utilization, digestibility of dietary fatty acids and fatty acid composition of lipoproteins, plasma, liver, belly flap, red and white muscle were measured. Further, the lipid class and protein levels in the lipoproteins were analyzed. The different dietary fatty acid compositions did not significantly affect protein utilization or β-oxidation capacity in red muscle. The levels of total cholesterol, triacylglycerols, and protein in very low density lipoprotein (VLDL), low density lipoprotein (LDL), high density lipoprotein (HDL), and plasma were not significantly affected by the dietary fatty acids. VLDL, LDL, and HDL fatty acid compositions were decreasingly affected by dietary fatty acid composition. Dietary fatty acid composition significantly affected both the relative fatty acid composition and the amount of fatty acids (mg fatty acid per g tissue, wet weight) in belly flap, liver, red and white muscle. Apparent digestibility of the fatty acids measured by adding yttrium oxide as inert marker, was significantly lower in fish fed the PO diet compared to the other three diets.     

Black currant seed oil feeding and fatty acids in liver lipid classes of guinea pigs

Guinea pigs were fed one of three diets containing 10% black currant seed oil (a source of gamma-linolenic (18∶3 n−6) and stearidonic (18∶4 n−3) acids), walnut oil or lard for 40 days. The fatty acid composition of liver triglycerides, free fatty acids, cholesteryl esters, phosphatidylinositol, phosphatidylserine, cardiolipin, phosphatidylcholine and phosphatidylethanolamine were determined. Dietary n−3 fatty acids found esterified in liver lipids had been desaturated and elongated to longer chain analogues, notably docosapentaenoic acid (22∶5 n−3) and docosahexaenoic acid (22∶6 n−3). When the diet contained low amounts of n−6 fatty acids, proportionately more of the n−3 fatty acids were transformed. Significantly more eicosapentaenoic acid (EPA) (20∶5 n−3) was incorporated into triglycerides, cholesteryl esters, phosphatidylcholine and phosphatidylethanolamine of the black currant seed oil group compared with the walnut oil group. Feeding black currant seed oil resulted in significant increases of dihomogamma-linolenic acid (20∶3 n−6) in all liver lipid classes examined, whereas the levels of arachidonic acid (20∶4 n−6) remained relatively stable. The ratio dihomo-gamma-linolenic acid/arachidonic acid was significantly (2.5-fold in PI to 17-fold in cholesteryl esters) higher in all lipid classes from the black currant seed oil fed group.     

Essential fatty acids in trout serum lipoproteins,vitellogenin and egg lipids

This paper describes evidence of (n−3) and particularly of 22∶6 (n−3) fatty acid enrichment in trout lipoproteins as well as in vitellogenin, egg lipovitellin and oil globule. Among the lipoproteins, HDL and LDL were the main forms of blood lipid transport, whereas phospholipids and cholesteryl esters are the preferential chemical carriers for (n−3) fatty acid transport. However, cholesteryl esters were less important as esterified fatty acid carriers than in man. Taken together with the data obtained in mammals, our results suggest that there may be a relationship between EFA activity and the distribution of the EFA among the lipoprotein lipid fractions in vertebrates, irrespective of the EFA series. Administration of an (n−3) fatty acid deficient diet for three months prior to trout spawning produced a significant increase in egg lipid content, primarily as a result of the increase of the oil globule composed almost exclusively of triacylglycerols. This diet decreased the 22∶6 (n−3), as well as the (n−3) fatty acid contents of lipoproteins, lipovitellin, vitellogenin and the oil globule. In contrast, the (n−3) fatty acid level was always higher in lipoproteins and lipovitellin than in the vitellogenin and the oil globule. Moreover, the relative levels of 22∶6 (n−3) and total (n−3) fatty acids were quite similar in lipoproteins and lipovitellin on the one hand, and in vitellogenin and the oil globule on the other. These findings suggest a direct relationship between the two forms of plasma lipid transport and the two egg compartments. During ovogenesis, dietary lipids seemed to be diverted from the adipose tissue and essentially deposited in the egg.     

Metabolism of glyceryl 1-14C-trilinoleate in rat testis

Animals of the Sprague-Dawley strain were injected intratesticularly with radioactive glyceryl 1-¹⁴C-trilinoleate in a sequential experiment and killed at 1/4, 1/2, 1, 3, 6, 12, 24, 36 and 48 hr. Distribution and concentration (specific activity) of radioactivity among the lipid classes and fatty acids were determined. The results showed that radioactive 1-¹⁴C-linoleic acid was released from the glyceryl trilinoleate and incorporated throghout the lipid classes. The pattern of the distribution of the radioactivity and specific activities showed that the transformation of linoleic acid between the triglyceride, diglyceride and fatty acid pools was an equilibrium process. Linoleic acid released from glyceryl 1-¹⁴C-trilinoleate was converted to higher polyunsaturated fatty acids which were incorporated throughout the lipid classes, and was catabolized as evidenced by the finding of radioactivity in palmitic acid. The main metabolic pools in the interconversion of linoleic acid were arachidonic and 22∶5 acids. Small amounts of 20∶3 and 22∶4 were also detected and had high specific activities indicative of their roles as precursors.     

Varietal difference in lipid content and fatty acid composition of highbush blueberries

Lipids from five cultivars of highbush blueberries (Vaccinium corymbosum L.) were extracted and fractionated into neutral lipids (60–66%), glycolipids (20–22%) and phospholipids (14–18%). The major fatty acids in all fractions were palmitic (16∶0), oleic (18∶1), linoleic (18∶2), and linolenic (18∶3) acids. All lipid classes had a large concentration of C₁₈ polyunsaturated acids (84–92%), indicating that blueberries are a rich source of linoleic and linolenic acids. Changes in the fatty acid composition of neutral lipids and phospholipids were not significantly different among the five cultivars, but significant differences were noted in the ratios of linoleic and linolenic acids in the glycolipids fraction.     

A diet containing myristoleic plus palmitoleic acids elevates plasma cholesterol in young growing swine

The objective of this study was to test the effect of a novel fatty acid mixture, enriched with myristoleic and palmitoleic acids, on plasma lipoprotein cholesterol concentrations. Weanling pigs were assigned to one of six groups and each group received a diet differing in fatty acid composition. Diets were fed for 35 days and contained 10 g added cornstarch/100 g (to provide baseline data) or 10 g added fatty acids/100 g. For those diets containing added fatty acids, extracted lipids contained 36% myristoleic plus palmitoleic acid combined (14∶1/16∶1 diet), 52% palmitic acid (16∶0 diet), 51% stearic acid (18∶0 diet), 47% oleic acid (18∶1 diet), or 38% linoleic acid (18∶2 diet). Witht the exception of the cornstarch diet, all diets contained approximately 30% myristic acid. There were no significant differences in weight gain across treatment groups (P=0.22). All diets caused a significant increase in triglycerides and in total, low density lipoprotein, high density lipoprotein, and very low density lipoprotein cholesterol. The increase in total plasma cholesterol from pretreatment values was greatest in pigs fed the 14∶1/16∶1 and 18∶1 diets. However, the increase in low density lipoprotein cholesterol from the pretreatment concentration was greatest in the 14∶1/16∶1-fed pigs. Increases in very low density lipoprotein cholesterol above pretreatment concentrations were lowest in 16∶0-fed pigs and greatest in 18∶1-fed pigs. Dietary fatty acids elicited changes in plasma fatty acids which generally were reflective of the diets, although the 18∶0 diet did not alter plasma fatty acid concentrations and the 16∶0 diet increased plasma 16∶0 only at the end of the study. These results demonstrated that the combination of myristoleic plus palmitoleic acids increased plasma cholesterol in young pigs, suggesting that fatty acid chain length, rather than degree of unsaturation, is primarily responsible for the effects of fatty acids on circulating lipoprotein cholesterol concentrations.     

Chronic administration of eicosapentaenoic acid and docosahexaenoic acid as ethyl esters reduced plasma cholesterol and changed the fatty acid composition in rat blood and organs

Fish oils rich in n-3 fatty acids have been shown to decrease plasma lipid levels, but the underlying mechanism has not yet been elucidated. This investigation was performed in order to further clarify the effects of purified ethyl esters of eicosapentaenoic acid (EPA-EE) and docosahexaenoic acid (DHA-EE) on lipid metabolism in rats. The animals were fed EPA-EE, DHA-EE, palmitic acid, or corn oil (1 g/kg/d) by orogastric intubation along with a chow background diet for three months. At the end the animals were sacrificed. Plasma and liver lipids were measured, as well as lipid-related enzyme activities and mRNA levels. The fatty acid composition of plasma and different tissues was also determined. This study shows that, compared to the corn oil control, EPA-EE and DHA-EE lowered plasma cholesterol level, whereas only EPA-EE lowered the amount of plasma triacylglycerol. In liver peroxisomes, both EE preparations increased fatty acyl-CoA oxidase FAO activities, and neither altered 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase activities. In liver microsomes, EPA-EE raised HMG-CoA reductase and acyl-CoAicholesterol acyltransferase activities, whereas DHA-EE lowered the former and did not affect the latter. Neither product altered mRNA levels for HMG-CoA reductase, low density lipoprotein-receptor, or low density lipoprotein-receptor related protein. EPA-EE lowered plasma triacylglycerol, reflecting lowered very low density lipoprotein secretion, thus the cholesterol lowering effect in EPA-EE-treated rats may be secondary to the hypotriacylglycerolemic effect. An inhibition of HMG-CoA reductase activity in DHA-EE treated rats may contribute to the hypocholesterolemic effect. The present study reports that 20∶5n-3, and not 22∶6n-3, is the fatty acid primarily responsible for the triacylglycerol lowering effect of fish oil. Finally, 20∶5n-3 was not converted to 22∶6n-3, whereas retroconversion of 22∶6n-3 to 20∶5n-3 was observed.     

Lipid,sterol and fatty acid composition of antarctic krill (Euphausia superba Dana)

The lipid classes, fatty acids of total and individual lipids and sterols of Antarctic krill (Euphausia superba Dana) from two areas of the Antarctic Ocean were analyzed by thin layer chromatography (TLC), gas liquid chromatography (GLC) and gas liquid chromatography/mass spectrometry (GLC/MS). Basic differences in the lipid composition of krill from the Scotia Sea (caught in Dec. 1977) and krill from the Gerlache Strait (caught in Mar. 1981) were not observed. The main lipid classes found were: phosphatidylcholine (PC) (33–36%), phosphatidylethanolamine (PE) (5–6%), triacylglycerol (TG) (33–40%), free fatty acids (FFA) (8–16%) and sterols (1.4–1.7%). Wax esters and sterol esters were present only in traces. More than 50 fatty acids could be identified using GLC/MS, the major ones being 14∶0, 16∶0, 16∶1(n−7), 18∶1(n−9), 18∶1(n−7), 20∶5(n−3) and 22∶6(n−3). Phytanic acid was found in a concentration of 3% of total fatty acids. Short, medium-chain and hydroxy fatty acids (C≤10) were not detectable. The sterol fraction consisted of cholesterol, desmosterol and 22-dehydrocholesterol.     

Incorporation oftrans-8- andcis-8-octadecenoic acid isomers in human plasma and lipoprotein lipids

Mixtures of deuterium-labeledtrans-8-,cis-8- andcis-9-octadecenoic acids (8t–18∶1, 8c–18∶1, 9c–18∶1) were fed as triglycerides (TG) to two adult male subjects. Blood samples were collected sequentially over a 48-hour period. Plasma and lipoprotein lipids were separated by thin layer chromatography and analyzed by gas chromatography-mass spectroscopy. Results indicate (i) absorption of the 8t- and 8c–18∶1 isomers were similar to 9c–18∶1; (ii) the 8t–18∶1 isomer was cleared approximately 30% faster than 9c–18∶1 from plasma TG; (iii) cholesterol ester samples contained 8.4 times less 8t–18∶1 than 9c–18∶1; (iv) incorporation at the 1-acyl phosphatidylcholine (PC) position was higher for 8t–18∶1 and 8c–18∶1 (2.2 and 1.7 times) than for 9c–18∶1; and (v) discrimination at the 2-acyl PC position was 4.6-fold against 8t–18∶1 and 1.3-fold against 8c–18∶1 compared with 9c–18∶1. Discrimination against uptake of the Δ-8 isomers in both neutral and phospholipid classes suggests that both 8t- and 8c–18∶1 may be preferentially oxidized relative to 9c–18∶1. Except for triglycerides, data for each of the lipid classes from total plasma and individual lipoprotein samples were similar. These data indicate that differences for incorporation and turnover of the 8t- and 8c–18∶1 isomers relative to 9c–18∶1 are not substantially influenced by the lipoprotein classes. The maximum isotopic enrichment detected in the chylomicron triglycerides fractions was 60%, which indicates that a substantial amount of endogenous triglycerides was mobilized during absorption of the deuterated fats.