Quantitative analysis of brain and spinach leaf lipids employing silicic acid column chromatography and acetone for elution of glycolipids

Quantitative elution of acidic and neutral glycolipids of brain and spinach leaves from silicic acid columns with acetone was demonstrated. Cerebrosides and sulfatides of brain and sulfolipid and glycosyl diglycerides of spinach leaves were eluted quantitatively with acetone while prospholipids remained on the column. The observations provide the basis for an analytical procedure employing column and quantitative thin-layer chromatography (TLC). Sephadex column chromatography is utilized for separation of lipids from nonlipids; silicic acid column chromatography for separation into neutral lipid, glycolipid and phospholipid fractions; and quantitative TLC for analysis of lipid classes of each column fraction.

Studies on the lipids of sheep red blood cells. I. Lipid composition in low and high potassium red cells

The lipid composition of whole red blood cells was investigated in five sheep with red cells containing a low concentration of potassium (LK) and in five sheep with red cells containing a high concentration of potassium (HK). No apparent differences within the limit of error of the experiment were detected in the lipid class composition between the HK and LK red cells. Cholesterol, the only nonpolar lipid detected in the tissue, was present in oneto-one molar ratio to the total phospholipids. Phosphatidyl ethanolamine and sphingomyelin accounted for 85% of the total phospholipids; phosphatidyl serine, phosphatidyl inositol, phosphatidic acid, and lysolecithin were present in lesser amounts. No lecithin was detected in any of the animals in this investigation. Plasmalogen compounds were found only in the ethanolamine lipids. The molar ratio of choline to noncholine phospholipids was also approximately one to one. It was concluded that the major lipid class distribution in the two types of red cells cannot be directly responsible for the differences observed in the cation concentrations in these cells in the two species of sheep.

The phospholipid composition of plasma in various mammalian species

Plasma phospholipids in several common mammalian species, including cat, cow, dog, goat, guinea pig, horse, pig, rabbit, rat, and sheep, were analyzed by using chromatographic and spectrophotometric methods. Lipids were extracted from plasma with chloroform-methanol 2ratio1 (v/v) and freed of nonlipid material by passage through a Sephadex column. The phospholipids were separated by two-dimensional thin-layer chromatography (TLC). Spots were identified by spray reagents, also by infrared spectrophotometry. The relative distribution of the phospholipids was determined by phosphorus analysis on the spot scraped off the TLC plate.Lecithin, lysolecithin, and sphingomyelin were found in the plasma of all species and accounted for more than 95% of the phospholipids except in the rodents. Lecithin was without exception the major phospholipid in plasma (56 to 83%). Lysolecithin and sphingomyelin content varied between 8 and 23% and 6 and 15% respectively. Phosphatidyl ethanolamine and phosphatidyl inositol were the only noncholine-containing phospholipids detected (detection limits 0.2%) in the plasma of these species. Together these compounds usually made up less than 5% of the total phospholipid. Rodents were an exception, especially the guinea pig, which had 21.7% phosphatidyl ethanolamine.

Studies on the lipids of sheep red blood cells. II. The incorporation of phosphorus into phospholipids of HK and LK cells

The incorporation of inorganic phosphate (as NaH(2)PO(4)) into the phospholipids of sheep red blood cells was studied in vitro in blood samples from five highpotassium (HK) and five low-potassium (LK) sheep. The erythrocytes from HK sheep incorporated more activity in 4 hr than those from the LK sheep. However no activity was incorporated into the major phospholipids of the cells (phosphatidyl ethanolamine, phosphatidyl serine, and sphingomyelin) of either group. The phosphatidic acid fraction was labeled in both groups and to a significantly greater extent in the HK samples. However the highest activity in the phospholipid of sheep red-cells was located in three unknown compounds not previously detected. Their specific activities were the same in the HK and the LK samples although they were present in slightly larger amounts in the HK samples. In general, incorporation was at a rather low level, and from stoichiometric considerations it was concluded that the metabolism in the red-cell phospholipids could not be directly involved in the active transport of ions across the cell membrane. This work also confirmed a previous report that no quantitative differences exist among the major phospholipid classes in the two types of cells.

Dietary supplementation with conjugated linoleic acid increased its concentration in human peripheral blood mononuclear cells, but did not alter their function

The purpose of this study was to examine if conjugated linoleic acid (CLA) supplementation of diets would alter fatty acid (FA) composition and function of peripheral blood mononuclear cells (PBMC). Seventeen women, 20-41 yr, participated in a 93-d study conducted at the Metabolic Research Unit. The same diet (19, 30, and 51% energy from protein, fat, and carbohydrate, respectively) was fed to all subjects throughout the study. Seven subjects (control group) supplemented their diet with six daily capsules (1 g each) of placebo oil (sunflower) for 93 d. For the other 10 subjects (CLA group), the supplement was changed to an equivalent amount of Tonalin capsules for the last 63 d of the study. Tonalin provided 3.9 g/d of a mixture of CLA isomers (trans-10,cis-12, 22.6%; cis-11,trans-13, 23.6%; cis-9,trans-11, 17.6%; trans-8,cis-10, 16.6%; other isomers 19.6%), and 2.1 g/d of other FA. PBMC isolated on study days 30 and 90 were used to assess intracellular cytokines by flow cytometry, secreted cytokines, and eicosanoid by enzyme-linked immonosorbent assay, and FA composition by gas-liquid chromatography. After supplementation, total CLA concentration increased from 0.012 to 0.97% (P < 0.0001) in PBMC lipids, but it did not significantly alter the concentration of other FA. CLA supplementation did not alter the in vitro secretion of prostaglandin E2, leukotriene B4, interleukin-1beta (IL-1beta), or tumor necrosis factor alpha (TNFalpha) by PBMC simulated with lipopolysaccharide, and the secretion of IL-2 by PBMC stimulated with phytohemagglutinin. Nor did it alter the percentage T cells producing IL-2, interferon gamma, and percentage of monocytes producing TNFalpha. The intracellular concentration of these cytokines was also not altered. None of the variables tested changed in the control group. Our results show that CLA supplementation increased its concentration in PBMC lipids, but did not alter their functions.

The effect of conjugated linoleic acid on platelet function, platelet fatty acid composition, and blood coagulation in humans

Despite extensive research on conjugated linoleic acid (CLA) showing multiple beneficial effects in animal models, little is known about the role of dietary CLA in human health. To investigate if the beneficial effects of CLA seen in animal models are relevant to humans, we conducted a study with 17 healthy female volunteers who lived in the Metabolic Research Unit of the Western Human Nutrition Research Center for 93 d. This paper reports only the results from this study that are related to the effects of CLA supplementation on blood coagulation, platelet function, and platelet fatty acid composition. Throughout the study, the subjects were fed a low-fat diet (30 en% fat, 19 en% protein, and 51 en% carbohydrate) consisting of natural foods with the recommended dietary allowances for all known nutrients. After a 30-d stabilization period, subjects were randomly assigned to either an intervention group (n = 10) whose diet was supplemented with 3.9 g/d of CLA or a control group (n = 7) who received an equivalent amount of sunflower oil consisting of 72.6% linoleic acid with no detectable CLA. Platelet aggregation was measured in platelet-rich plasma using adenosine diphosphate, collagen, and arachidonic acid agonists. No statistical difference was detected between the amount of agonist required to produce 50% aggregation of platelet-rich plasma before and after the subjects consumed the CLA, with the exception of a decrease in response to collagen. This decrease was found in both control and intervention groups with no significant difference between the groups, suggesting that both linoleic acid (sunflower oil) and CLA might have similar effects on platelet function. The prothrombin time, activated partial thromboplastin time, and the antithrombin III levels in the subjects were determined. Again, there was no statistically significant difference in these three parameters when pre- and post-CLA consumption values were compared. The in vivo bleeding times were also unaffected by CLA supplementation (10.4 + 2.8 min pre- and 10.2 + 1.6 min postconsumption). Platelet fatty acid composition was not markedly influenced by the consumption of dietary CLA, although there was a small increase in the amount of the 9 cis,11 trans-18:2 isomer normally present in platelets after feeding CLA for 63 days. In addition, small amounts of the 8 trans,10 cis-18:2 and the 10 trans,12 cis-18:2 isomers were detected in the platelets along with traces of some of the other isomers. Thus, when compared to sunflower oil, the blood-clotting parameters and in vitro platelet aggregation showed that adding 3.9 g/d of dietary CLA to a typical Western diet for 63 d produces no observable physiological change in blood coagulation and platelet function in healthy adult females. Short-term consumption of CLA does not seem to exhibit antithrombotic properties in humans.

The effect of conjugated linoleic acid on plasma lipoproteins and tissue fatty acid composition in humans

Conjugated linoleic acid (CLA) has been suggested by some animal studies to possess antiatherogenic properties. To determine, in humans, the effect of dietary CLA on blood lipids, lipoproteins, and tissue fatty acid composition, we conducted a 93-d study with 17 healthy female volunteers at the Metabolic Research Unit of the Western Human Nutrition Research Center. Throughout the study, subjects were fed a low-fat diet [30 energy percent (en%) fat, 19 en% protein, and 51 en% carbohydrate] that consisted of natural foods with the recommended dietary allowances for all known nutrients. After a 30-d stabilization period, subjects were randomly assigned to either an intervention group (n = 10) supplemented daily with capsules containing 3.9 g of CLA or a control group (n = 7) that received an equivalent amount of sunflower oil. The CLA capsules (CLA 65%) contained four major cis/trans geometric isomers (11.4% 9 cis-,11 trans-18:2; 10.8% 8 trans-,10 cis-18:2; 15.3% 11 cis-,13 trans-18:2; and 14.7% 10 trans-,12 cis-18:2) and their corresponding cis/cis (6.74% total) and trans/trans (5.99% total) varieties in smaller amounts. Fasting blood was drawn on study days 30 (end of the stabilization period), 60 (midpoint of the intervention period), and 93 (end of the intervention period). Adipose tissue samples were taken on days 30 and 93. CLA supplementation for 63 d did not change the levels of plasma cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol, and triglycerides. The weight percentage of CLA in plasma increased from 0.28 +/- 0.06 to 1.09 +/- 0.31 (n = 10, P < 0.05) after the supplementation. The 9 cis-,11 trans-isomer was the most prominent variety followed by the 11 cis-,13 trans- and 10 trans-,12 cis-isomers in lesser amounts. CLA in adipose tissue was not influenced by the supplementation (0.79 +/- 0.18 to 0.83 +/- 0.19 wt%) (n = 10) and the 9 cis-,11 trans-variety was the only isomer present. Thus, contrary to findings from some animal studies, CLA does not seem to offer health benefits, in the short term, regarding the prevention of atherosclerosis in humans. CLA supplementation for 2 mon did not alter the blood cholesterol or lipoprotein levels of healthy, normolipidemic subjects. The supplementation did increase CLA in the plasma but only 4.23% of the ingested CLA was present in the plasma at any given time. No adverse effect of CLA supplementation was detected in this study.

Dietary conjugated linoleic acid did not alter immune status in young healthy women

The purpose of this study was to examine whether conjugated linoleic acid (CLA) supplementation in human diets would enhance indices of immune status as reported by others for animal models. Seventeen women, 20-41 yr, participated in a 93-d study conducted in two cohorts of 9 and 8 women at the Metabolic Research Unit of Western Human Nutrition Research Center. Seven subjects were fed the basal diet (19, 30, and 51% energy from protein, fat, and carbohydrate, respectively) throughout the study. The remaining 10 subjects were fed the basal diet for the first 30 d, followed by 3.9 g CLA (Tonalin)/d for the next 63 d. CLA made up 65% of the fatty acids in the Tonalin capsules, with the following isomeric composition: t10, c12, 22.6%; c11, t13, 23.6%; c9, t11, 17.6%; t8, c10, 16.6%; and other isomers 19.6%. Most indices of immune response were tested at weekly intervals, three times at the end of each period (stabilization/intervention); delayed-type hypersensitivity (DTH) to a panel of six recall antigens was tested on study day 30 and 90; all subjects were immunized on study day 65 with an influenza vaccine, and antibody titers were examined in the sera collected on day 65 and 92. None of the indices of immune status tested (number of circulating white blood cells, granulocytes, monocytes, lymphocytes, and their subsets, lymphocytes proliferation in response to phytohemagglutinin, and influenza vaccine, serum influenza antibody titers, and DTH response) were altered during the study in either dietary group. Thus, in contrast to the reports with animal models, CLA feeding to young healthy women did not alter any of the indices of immune status tested. These data suggest that short-term CLA supplementation in healthy volunteers is safe, but it does not have any added benefit to their immune status.

Conjugated linoleic acid supplementation in humans: effects on body composition and energy expenditure

Recent animal studies have demonstrated that dietary conjugated linoleic acid (CLA) reduces body fat and that this decrease may be due to a change in energy expenditure. The present study examined the effect of CLA supplementation on body composition and energy expenditure in healthy, adult women. Seventeen women were fed either a CLA capsule (3 g/d) or a sunflower oil placebo for 64 d following a baseline period of 30 d. The subjects were confined to a metabolic suite for the entire 94 d study where diet and activity were controlled and held constant. Change in fat-free mass, fat mass, and percentage body fat were unaffected by CLA supplementation (0.18+/-0.43 vs. 0.09+/-0.35 kg; 0.01+/-0.64 vs. -0.19+/-0.53 kg; 0.05+/-0.62 vs. -0.67+/-0.51%, placebo vs. CLA, respectively). Likewise, body weight was not significantly different in the placebo vs. the CLA group (0.48+/-0.55 vs. -0.24+/-0.46 kg change). Energy expenditure (kcal/min), fat oxidation, and respiratory exchange ratio were measured once during the baseline period and during weeks 4 and 8 of the intervention period. At all three times, measurements were taken while resting and walking. CLA had no significant effect on energy expenditure, fat oxidation, or respiratory exchange ratio at rest or during exercise. When dietary intake was controlled, 64 d of CLA supplementation at 3 g/d had no significant effect on body composition or energy expenditure in adult women, which contrasts with previous findings in animals.

Conjugated linoleic acid supplementation in humans: effects on circulating leptin concentrations and appetite

Conjugated linoleic acid (CLA) has been demonstrated to reduce body fat in animals. However, the mechanism by which this reduction occurs is unknown. Leptin may mediate the effect of CLA to decrease body fat. We assessed the effects of 64 d of CLA supplementation (3 g/d) on circulating leptin, insulin, glucose, and lactate concentrations in healthy women. Appetite was assessed as a physiological correlate of changes in circulating leptin levels. Analysis of plasma leptin concentrations adjusted for adiposity by using fat mass as a covariate showed that CLA supplementation significantly decreased circulating leptin concentrations in the absence of any changes of fat mass. Mean leptin levels decreased over the first 7 wk and then returned to baseline levels over the last 2 wk of the study in the CLA-treated group. Appetite parameters measured at around the time when the greatest decreases in leptin levels were observed showed no significant differences between supplementation and baseline determinations in the CLA-supplemented group or between the CLA and placebo-supplemented groups. There was a nonsignificant trend for mean insulin levels to increase toward the end of the supplementation period in CLA-treated subjects. CLA did not affect plasma glucose and lactate over the treatment period. Thus, 64 d of CLA supplementation in women produced a transient decrease in leptin levels but did not alter appetite. CLA did not affect these parameters in a manner that promoted decreases of adiposity.

Effect of dietary docosahexaenoic acid on desaturation and uptake in vivo of isotope-labeled oleic, linoleic, and linolenic acids by male subjects

The effect of dietary docosahexaenoic acid (22:6n-3, DHA) on the metabolism of oleic, linoleic, and linolenic acids was investigated in male subjects (n = 6) confined to a metabolic unit and fed diets containing 6.5 or <0.1 g/d of DHA for 90 d. At the end of the diet period, the subjects were fed a mixture of deuterated triglycerides containing 18:1n-9[d6], 18:2n-6[d2], and 18:3n-3[d4]. Blood samples were drawn at 0, 2, 4, 6, 8, 12, 24, 48, and 72 h. Methyl esters of plasma total lipids, triglycerides, phospholipids, and cholesterol esters were analyzed by gas chromatography-mass spectrometry. Chylomicron triglyceride results show that the deuterated fatty acids were equally well absorbed and diet did not influence absorption. Compared to the low-DHA diet (LO-DHA), clearance of the labeled fatty acids from chylomicron triglycerides was modestly higher for subjects fed the high DHA diet (HI-DHA). DHA supplementation significantly reduced the concentrations of most n-6[d2] and n-3[d4] long-chain fatty acid (LCFA) metabolites in plasma lipids. Accumulation of 20:5n-3[d4] and 22:6n-3[d4] was depressed by 76 and 88%, respectively. Accumulations of 20:3n-6[d2] and 20:4n-6[d2] were both decreased by 72%. No effect of diet was observed on acyltransferase selectivity or on uptake and clearance of 18:1n-9[d6], 18:2n-6[d2], and 18:3n-3[d4]. The results indicate that accumulation of n-3 LCFA metabolites synthesized from 18:3n-3 in typical U.S. diets would be reduced from about 120 to 30 mg/d by supplementation with 6.5 g/d of DHA. Accumulation of n-6 LCFA metabolites synthesized from 18:2n-6 in U.S. diets is estimated to be reduced from about 800 to 180 mg/d. This decrease is two to three times the amount of n-6 LCFA in a typical U.S. diet. These results support the hypothesis that health benefits associated with DHA supplementation are the combined result of reduced accretion of n-6 LCFA metabolites and an increase in n-3 LCFA levels in tissue lipids.

Docosahexaenoic acid ingestion inhibits natural killer cell activity and production of inflammatory mediators in young healthy men

The purpose of this study was to examine the effects of feeding docosahexaenoic acid (DHA) as triacylglycerol on the fatty acid composition, eicosanoid production, and select activities of human peripheral blood mononuclear cells (PBMNC). A 120-d study with 11 healthy men was conducted at the Metabolic Research Unit of Western Human Nutrition Reach Center. Four subjects (control group) were fed the stabilization diet throughout the study; the remaining seven subjects were fed the basal diet for the first 30 d, followed by 6 g DHA/d for the next 90 d. DHA replaced an equivalent amount of linoleic acid; the two diets were comparable in their total fat and all other nutrients. Both diets were supplemented with 20 mg D alpha-tocopherol acetate per day. PBMNC fatty acid composition and eicosanoid production were examined on day 30 and 113; immune cell functions were tested on day 22, 30, 78, 85, 106, and 113. DHA feeding increased its concentration from 2.3 to 7.4 wt% in the PBMNC total lipids, and decreased arachidonic acid concentration from 19.8 to 10.7 wt%. It also lowered prostaglandin E2 (PGE2) and leukotriene B4 (LTB4) production, in response to lipopolysaccharide, by 60-75%. Natural killer cell activity and in vitro secretion of interleukin-1beta and tumor necrosis factor alpha were significantly reduced by DHA feeding. These parameters remained unchanged in the subjects fed the control diet. B-cell functions as reported here and T-cell functions that we reported previously were not altered by DHA feeding. Our results show that inhibitory effects of DHA on immune cell functions varied with the cell type, and that the inhibitory effects are not mediated through increased production of PGE2 and LTB4.

Dietary fat, trans fatty acids, and risk of coronary heart disease

Results from human feeding studies and recent large-scale epidemiologic surveys suggest that dietary trans fatty acids enhance the risk of developing coronary heart diseases. Despite a lack of accurate data regarding dietary intake of trans fatty acids, existing epidemiologic data and evidence from experimental feeding studies support the idea that lowering current intakes of trans fatty acids may lower the risk of coronary heart disease.

Dietary docosahexaenoic acid and immunocompetence in young healthy men

The purpose of this study was to examine the effect of dietary docosahexaenoic acid (DHA), in the absence of eicosapentaenoic acid, on human immune response (IR). A 120-d study with 11 healthy men was conducted at the Metabolic Research Unit of the Western Human Nutrition Research Center. Four subjects (control group) were fed the stabilization or basal diet (15, 30, and 55% energy from protein, fat, and carbohydrate, respectively) throughout the study; the remaining seven subjects (DHA group) were fed the basal diet for the first 30 d, followed by 6 g DHA/d for the next 90 d. DHA replaced an equivalent amount of linoleic acid; the two diets were comparable in their total fat and all other nutrients. Both diets were supplemented with 20 mg d-alpha-tocopherol acetate per day. Indices of IR were examined on study day 22, 30, 78, 85, 106, and 113. Addition of DHA at moderately high levels did not alter the proliferation of peripheral blood mononuclear cells cultured with phytohemagglutinin or concanavalin A, or the delayed hypersensitivity skin response. Also, additional DHA did not alter the number of T cells producing interleukin 2 (IL2), the ratio between the helper/suppressor T cells in circulation, or the serum concentrations of immunoglobulin G, C3, and interleukin 2 receptor (IL2R). DHA supplementation, however, caused a significant (P = 0.0001) decrease in the number of circulating white blood cells which was mainly due to a decrease in the number of circulating granulocytes. The number of lymphocytes in peripheral circulation was not affected by Dietary DHA enrichment, but the percentage of lymphocytes in white blood cells increased because of a reduction in granulocyte numbers. None of these indices was changed in the control group. Our results show that when total fat intake is low and held constant, DHA consumption does not inhibit many of the lymphocyte functions which have been reported to be inhibited by fish oil consumption.

Effect of dietary arachidonic acid on metabolism of deuterated linoleic acid by adult male subjects

The influence of dietary supplementation with 20:4n-6 on uptake and turnover of deuterium-labeled linoleic acid (18:2n-6[d2]) in human plasma lipids and the synthesis of desaturated and elongated n-6 fatty acids from 18:2n-6[d21 were investigated in six adult male subjects. The subjects were fed either a high-arachidonic acid (HIAA) diet containing 1.7 g/d or a low-AA (LOAA) diet containing 0.21 g/d of AA for 50 d. Each subject was then dosed with about 3.5 g of 18:2n-6[d2] as the triglyceride (TG) at 8:00 A.M., 12:00, and 5:00 P.M. The total 18:2n-6[d21] fed to each subject was about 10.4 g and is approximately equal to one-half of the daily intake of 18:2n-6 in a typical U.S. male diet. Nine blood samples were drawn over a 96-h period. Methyl esters of plasma total lipid (TL), TG, phospholipid, and cholesterol ester were analyzed by gas chromatography-mass spectroscopy. Dietary 20:4n-6 supplementation did not affect uptake of 18:2n-6[d2] in plasma lipid classes over the 4-d study period nor the estimated half-life of 24-36 h for 18:2n-6[d2]. The percentages of major deuterium-labeled desaturation and elongation products in plasma TL, as a percentage of total deuterated fatty acids, were 1.35 and 1.34% 18:3n-6[d2]; 0.53 and 0.50% 20:2n-6[d2]; 1.80 and 0.92% 20:3n-6[d2] and 3.13 and 1.51% 20:4n-6[d2] for the LOAA and HIAA diet groups, respectively. Trace amounts (<0.1%) of the 22:4n-6[d2] and 22:5n-6[d2] metabolites were present. Plasma TL concentration data for both 20:3n-6[d2] and 20:4n-6[d2] were 48% lower (P < 0.05) in samples from the HIAA diet group than in samples from the LOAA diet group. For a normal adult male consuming a typical U.S. diet, the estimated accumulation in plasma TL of 20:4n-6 synthesized from 20 g/d (68 mmole) of 18:2n-6 is 677 mg/d (2.13 mmole). Dietary supplementation with 1.5 g/d of 20:4n-6 reduced accumulation of 20:4n-6 synthesized from 20 g/d of 18:2n-6 to about 326 mg/d (1.03 mmole).

Arachidonic acid supplementation enhances synthesis of eicosanoids without suppressing immune functions in young healthy men

This study was conducted to determine the effects of arachidonic acid (AA) supplementation on human immune response (IR) and on the secretion of prostaglandin E2 (PGE2) and leukotriene B4 (LTB4). Ten healthy men (20-38 yr) participated in the study and lived at the Metabolic Suite of the Western Human Nutrition Research Center. They were fed a basal diet (57, 27, and 16 energy percentage from carbohydrate, fat, and protein, respectively, and AA 200 mg/d) for the first 15 d of the study. Additional AA (1.5 g/d) was added to the diet of six men from day 16 to 65, while the remaining four subjects remained on the basal diet. The diets of the two groups were crossed-over from day 66 to 115. In vitro indices of IR were examined using blood drawn on days 15, 58, 65, 108, and 115. Influenza antibody titers were determined in the sera prepared from blood drawn on days 92 and 115 (23 d postimmunization). AA supplementation caused significant increases in the in vitro secretion of LTB4, and PGE2, but it did not alter the in vitro secretion of tumor necrosis factor alpha; interleukins 1 beta, 2, 6; and the receptor for interleukin 2. Nor did it change the number of circulating lymphocytes bearing markers for specific subsets (B, T, helper, suppressor, natural killer) and the serum antibody titers against influenza vaccine. The opposing effects of PGE2 and LTB4 may have led to the lack of change in immune functions tested.

The effect of dietary docosahexaenoic acid on platelet function, platelet fatty acid composition, and blood coagulation in humans

The effect of dietary docosahexaenoic acid (DHA) in the absence of eicosapentaenoic acid (EPA) has been studied infrequently in humans under controlled conditions. This 120-d study followed healthy, adult male volunteers who lived in the metabolic research unit (MRU) of the Western Human Nutrition Research Center for the entire study. The basal (low-DHA) diet consisted of natural foods (30 en% fat, 15 en% protein, and 55 en% carbohydrate), containing < 50 mg/d of DHA, and met the recommended daily intake for all essential nutrients. The high-DHA (intervention) diet was similar except that 6 g/d of DHA in the form of a triglyceride containing 40% DHA replaced an equal amount of safflower oil in the basal diet. The subjects (ages 20 to 39) were within -10 to +20% of ideal body weight, nonsmoking, and not allowed alcohol in the MRU. Their exercise level was constant, and their body weights were maintained within 2% of entry level. They were initially fed the low-DHA diet for 30 d. On day 31, six subjects (intervention, group A) were placed on the high-DHA diet; the other four subjects (controls, group B) remained on the low-DHA diet. Platelet aggregation in platelet-rich plasma was determined using ADP, collagen, and arachidonic acid. No statistical differences could be detected between the amount of agonist required to produce 50% aggregation of platelet-rich plasma before and after the subjects consumed the high-DHA diet. The prothrombin time, activated partial thromboplastin time, and the antithrombin-III levels in the subjects were determined, and, again, there were no statistically significant differences in these three parameters when their values were compared before and after the subjects consumed the high-DHA diet. In addition, the in vivo bleeding times did not show any significant difference before and after the subjects consumed the high-DHA diet (9.4 +/- 3.1 min before and 8.0 +/- 3.4 min after). Platelets from the volunteers exhibited more than a threefold increase in their DHA content from 1.54 +/- 0.16 to 5.48 +/- 1.21 (wt%) during the DHA feeding period. The EPA content of the subjects' platelets increased from 0.34 +/- 0.12 to 2.67 +/- 0.91 (wt%) during the high-DHA diet despite the absence of EPA in the subjects' diets. The results from this study on blood clotting parameters and in vitro platelet aggregation suggest that adding 6 g/d of dietary DHA for 90 d to a typical Western diet containing less than 50 mg/d of DHA produces no observable physiological changes in blood coagulation, platelet function, or thrombotic tendencies in healthy, adult males.

The effect of dietary docosahexaenoic acid on plasma lipoproteins and tissue fatty acid composition in humans

Normal, healthy male volunteers (n = 6) were fed diets [high docosahexaenoic acid-DHA] containing 6 g/d of DHA for 90 d. The stabilization (low-DHA) diet contained less than 50 mg/d of DHA. A control group (n = 4) remained on the low-DHA diet for the duration of the study (120 d). Blood samples were drawn on study days 30 (end of the stabilization period), 75 (midpoint of the intervention period), and 120 (end of the intervention period). Adipose tissue (AT) samples were taken on days 30 and 120. The plasma cholesterol (C), low density lipoprotein (LDL)-C and apolipoproteins (apo) [Al, B, and lipoprotein (a)] were unchanged after 90 d, but the triglycerides (TAG) were reduced from a mean value of 76.67 +/- 24.32 to 63.83 +/- 16.99 mg/dL (n = 6, P < 0.007 using a paired t-test) and the high density lipoprotein (HDL)-C increased from 34.83 +/- 4.38 mg/dL to 37.83 +/- 3.32 mg/dL (n = 6, P < 0.017 using a paired t-test). The control group showed no significant reduction in plasma TAG levels. Apo-E, however, showed a marked increase in the volunteers' plasma after 90 d on the high-DHA diet, from 7.06 +/- 4.47 mg/dL on study day 30 to 12.01 +/- 4.96 mg/dL on study day 120 (P < 0.002 using a paired t-test). The control subjects showed no significant change in the apo-E in their plasma (8.46 +/- 2.90 on day 30 vs. 8.59 +/- 2.97 on day 120). The weight percentage of plasma DHA rose from 1.83 +/- 0.22 to 8.12 +/- 0.76 after 90 d on the high-DHA diet. Although these volunteers were eating a diet free of eicosapentaenoic acid (EPA), plasma EPA levels rose from 0.38 +/- 0.05 to 3.39 +/- 0.52 (wt%) after consuming the high-DHA diet. The fatty acid composition of plasma lipid fractions--cholesterol esters, TAG, and phospholipid--showed marked similarity in the enrichment of DHA, about 10%, after the subjects consumed the high-DHA diet. The DHA content of these plasma lipid fractions varied from less than 1% (TAG) to 3.5% (phospholipids) at baseline, study day 30. EPA also increased in all plasma lipid fractions after the subjects consumed the high-DHA diet. There were no changes in the plasma DHA or EPA levels in the control group. Consumption of DHA also caused an increase in AT levels of DHA, from 0.10 +/- 0.02 to 0.31 +/- 0.07 (wt%) (n = 6, P < 0.001 using a paired t-test), but the amount of EPA in their AT did not change. Thus, dietary DHA will lower plasma TAG without EPA, and DHA is retroconverted to EPA in significant amounts. Dietary DHA appears to enhance apo-E synthesis in the liver. It appears that DHA can be a safe and perhaps beneficial supplement to human diets.

A human dietary arachidonic acid supplementation study conducted in a metabolic research unit: rationale and design

While there are many reports of studies that fed arachidonic acid (AA) to animals, there are very few reports of AA feeding to humans under controlled conditions. This 130-d study was conceived as a controlled, symmetrical crossover design with healthy, adult male volunteers. They lived in the metabolic research unit (MRU) of the Western Human Nutrition Research (WHNRC) for the entire study. All food was prepared by the WHNRC kitchen. The basal (low-AA) diet consisted of natural foods (30 en% fat, 15 en% protein, and 55 en% carbohydrate), containing 210 mg/d of AA, and met the recommended daily allowance for all nutrients. The high-AA (intervention) diet was similar except that 1.5 g/d of AA in the form of a triglyceride containing 50% AA replaced an equal amount of high-oleic safflower oil in the basal diet. The subjects (ages 20 to 39) were within -10 to +20% of ideal body weight, nonsmoking, and not allowed alcohol in the MRU. Their exercise level was constant, and their body weights were maintained within 2% of entry level. Subjects were initially fed the low-AA diet for 15 d. On day 16, half of the subjects (group A) wee placed on the high-AA diet, and the other group (B) remained on the low-AA diets. On day 65, the two groups switched diets. On day 115, group B returned to the low-AA diet. This design, assuming no carryover effect, allowed us to merge the data from the two groups, with the data comparison days being 65 (low-AA) and 115 (high-AA) for group B and 130 (low-AA) and 65 (high-AA) for group A. The main indices studied were the fatty acid composition of the plasma, red blood cells, platelets, and adipose tissue; in vitro platelet aggregation, bleeding times, clotting factors; immune response as measured by delayed hypersensitivity skin tests, cellular proliferation of peripheral blood mononuclear cells in response to various mitogens and antigens, natural killer cell activity, and response to measles/mumps/rubella and influenza vaccines; the metabolic conversion of deuterated linoleic acid to AA and the metabolic fate of deuterated AA in the subjects on and off the high-AA diet; and the production of eicosanoids as measured by excretion of 11-DTXB2 and PGI2-M in urine. The results of these studies will be presented in the next five papers from this symposium.

The effect of dietary arachidonic acid on platelet function, platelet fatty acid composition, and blood coagulation in humans

Arachidonic acid (AA) is the precursor of thromboxane and prostacyclin, two of the most active compounds related to platelet function. The effect of dietary AA on platelet function in humans is not understood although a previous study suggested dietary AA might have adverse physiological consequences on platelet function. Here normal healthy male volunteers (n = 10) were fed diets containing 1.7 g/d of AA for 50 d. The control diet contained 210 mg/d of AA. Platelet aggregation in the platelet-rich plasma was determined using ADP, collagen, and AA. No statistical differences could be detected between the aggregation before and after consuming the high-AA diet. The prothrombin time, partial thromboplastin time, and the antithrombin III levels in the subjects were determined also. There were no statistically significant differences in these three parameters when the values were compared before and after they consumed the high-AA diet. The in vivo bleeding times also did not show a significant difference before and after the subjects consumed the high-AA diet. Platelets exhibited only small changes in their AA content during the AA feeding period. The results from this study on blood clotting parameters and in vitro platelet aggregation suggest that adding 1.5 g/d of dietary AA for 50 d to a typical Western diet containing about 200 mg of AA produces no observable physiological changes in blood coagulation and thrombotic tendencies in healthy, adult males compared to the unsupplemented diet. Thus, moderate intakes of foods high in AA have few effects on blood coagulation, platelet function, or platelet fatty acid composition.

Influence of dietary arachidonic acid on metabolism in vivo of 8cis,11cis,14-eicosatrienoic acid in humans

This study investigated the influence of dietary arachidonic acid (20:4n-6) on delta 5 desaturation and incorporation of deuterium-labeled 8cis,11 cis, 14-eicosatrienoic acid (20:3n-6) into human plasma lipids. Adult male subjects (n = 4) were fed diets containing either 1.7 g/d (HI20:4 diet) or 0.21 g/d (LO20:4 diet) of arachidonic acid for 50 d and then dosed with a mixture containing ethyl esters of 20:3n-6[d4] and 18:1n-9[d2]. A series of blood samples was sequentially drawn over a 72-h period, and methyl esters of plasma total lipid, triacylglycerol, phospholipids, and cholesteryl ester were analyzed by gas chromatography-mass spectrometry. Based on the concentration of 20:3n6[d4] in total plasma lipid, the estimated conversion of 20:3n-6[d4] to 20:4n-6[d4] was 17.7 +/- 0.79% (HI20:4 diet) and 2.13 +/- 1.44% (LO20:4 diet). The concentrations of 20:4n-6[d4] in total plasma lipids from subjects fed the HI20:4 and LO20:4 diets were 2.10 +/- 0.6 and 0.29 +/- 0.2 mumole/mL plasma/mmole of 20:3n-6[d4] fed/kg of body weight. These data indicate that conversion of 20:3n-6[d4] to 20:4n-6[d4] was stimulated 7-8-fold by the HI20:4 diet. Phospholipid acyltransferase was 2.5-fold more selective for 20:3n-6[d4] than 18:1n-9[d2], and lecithin:cholesterol acyltransferase was 2-fold more selective for 18:1n-9[ds] than 20:3n-6[d4]. These differences in selectivity were not significantly influenced by diet. Absorption of ethyl 20:3n-6[d4] was about 33% less than ethyl 18:1n-9[d2]. The sum of the n-6 retroconversion products from 20:3n-6[d4] in total plasma lipids was about 2% of the total deuterated fatty acids. Neither absorption nor retroconversion appears to be influenced by diet.

The effect of dietary arachidonic acid on plasma lipoprotein distributions, apoproteins, blood lipid levels, and tissue fatty acid composition in humans

Normal healthy male volunteers (n = 10) were fed diets (high-AA) containing 1.7 g/d of arachidonic acid (AA) for 50 d. The control (low-AA) diet contained 210 mg/d of AA. Dietary AA had no statistically significant effect on the blood cholesterol levels, lipoprotein distribution, or apoprotein levels. Adipose tissue fatty acid composition was not influenced by AA feeding. The plasma total fatty acid composition was markedly enriched in AA after 50 d (P < 0.005). The fatty acid composition of plasma lipid fractions, cholesterol esters, triglycerides, free fatty acids, and phospholipid (PL) showed marked differences in the degree of enrichment in AA. The PL plasma fraction from the subjects consuming the low-AA diet contained 10.3% AA while the subjects who consumed the high-AA diet had plasma PL fractions containing 19.0% AA. The level of 22:4n-6 also was different (0.67 to 1.06%) in the plasma PL fraction after 50 d of AA feeding. After consuming the high-AA diet, the total red blood cell fatty acid composition was significantly enriched in AA which mainly replaced linoleic acid. These results indicate that dietary AA is incorporated into tissue lipids, but selectively into different tissues and lipid classes. Perhaps more importantly, the results demonstrate that dietary AA does not alter blood lipids or lipoprotein levels or have obvious adverse health effects at this level and duration of feeding.

Increased dietary arachidonic acid enhances the synthesis of vasoactive eicosanoids in humans

Data on the effect of dietary arachidonic acid (AA) (20:4n-6) on the synthesis of thromboxane and prostacyclin (PGI2) in humans are lacking. We measured the effect of 1.5 g/d (ca. 0.5 en%) of 20:4n-6 added isocalorically to a stabilization (low-AA) diet on the excretion of 11-dehydrothromboxane B2 (11-DTXB2) and 2,3-dinor-6-oxo-PGF1 alpha (PGI2-M). In a crossover design, 10 healthy men, living in a metabolic unit, were fed a diet (low-AA) containing 210 mg/d of 20:4n-6 for 65 d and an identical diet (high-AA) that contained 1.5 g/d of additional 20:4n-6 for 50 d. Three-day urine pools were collected at the end of each dietary period and analyzed for eicosanoids by gas chromatography-electron capture negative ion-tandem mass spectrometry. Mean excretion of 11-dehydrothromboxane B2 was 515 +/- 76, 493 +/- 154, and 696 +/- 144 ng/d (SD; n = 10) during the acclimation (15 d) low-AA diet and high-AA diet periods, respectively (41% increase from low-AA to high-AA diet, P = 0.0037); mean excretion of PGI2-M was 125 +/- 40, 151 +/- 36, and 192 +/- 55 ng/d (SD; n = 10) during acclimation (15 d) low-AA and high-AA diets; P = 0.0143). Thus both the metabolites of thromboxane and PGI2 increase on the high-AA diet. Furthermore, both indicated changes in metabolite excretion may be associated with measurable effects on several physiologically significant cellular functions, such as platelet aggregation in vivo and inflammation in response to immune challenges.

Effects of dietary arachidonic acid on human immune response

Arachidonic acid (AA) is a precursor of eicosanoids, which influence human health and the in vitro activity of immune cells. We therefore examined the effects of dietary AA on the immune response (IR) of 10 healthy men living at our metabolic suite for 130 d. All subjects were fed a basal diet containing 27 energy percentage (en%) fat, 57 en% carbohydrate, and 16 en% protein (AA, 200 mg/d) for the first and last 15 d of the study. Additional AA (1.5 g/d) was incorporated into the diet of six men from day 16 to 65 while the remaining four subjects continued to eat the basal diet. The diets of the two groups were crossed-over from day 66 to 115. In vitro indexes of IR were examined using the blood samples drawn on days 15, 58, 65, 108, 115, and 127. The subjects were immunized with the measles/mumps/rubella vaccine on day 35 and with the influenza vaccine on day 92. Dietary AA did not influence many indexes of IR (peripheral blood mononuclear cell proliferation in response to phytohemagglutinin, Concanavalin A, pokeweed, measles/mumps/rubella, and influenza vaccines prior to immunization, and natural killer cell activity). The post-immunization proliferation in response to influenza vaccine was about fourfold higher in the group receiving high-AA diet compared to the group receiving low-AA diet (P = 0.02). Analysis of variance of the data pooled from both groups showed that the number of circulating granulocytes was significantly (P = 0.03) more when the subjects were fed the high-AA diet than when they were fed the low-AA diet. The small increases in granulocyte count and the in vitro proliferation in response to influenza vaccine caused by dietary AA may not be of clinical significance. However, the lack of any adverse effects on IR indicates that supplementation with AA may be done safely when needed for other health reasons.

Low-fat diets do not lower plasma cholesterol levels in healthy men compared to high-fat diets with similar fatty acid composition at constant caloric intake

In most studies reporting the effects of high-fat (HF) and low-fat (LF) diets on human plasma fatty acids (FA) and lipoprotein levels, the design involved adding to the diet an oil that had an FA composition (FAC) very different from the FAC of the control diet. Thus, it is difficult to determine if simply reducing the fat content of the diet without changing the dietary FAC changes the tissue FAC or alters plasma lipid levels. In this study, we fed diets that contained either 22 or 39% of calories from fat, but had no differences in their FAC, for 50 d to a group (n = 11) of healthy men (20-35 y). Thus, the polyunsaturated/saturated ratios (1.0) of the diets were identical as were the n-3/n-6 ratio and the monounsaturated-to-total fat ratios. The diets contained (wt% of total fat) approximately 28% saturated FA, 33% monounsaturated cis-FA, 6% monounsaturated trans-FA, 22% n-6 polyunsaturated FA, and 7% n-3 polyunsaturated FA, and 4% other minor FA. The diets consisted of natural foods and were formulated to contain 16 en% protein, either 45 or 62 en% carbohydrate (CHO) and at least the recommended daily allowance for all micronutrients. Both diets contained 360 mg of cholesterol per day. All subjects were given the HF diet for 20 d, and then six were placed on the LF and the other five remained on the HF diet for 50 d. The two groups were crossed-over for the remaining 50 d of the study. The subjects' baseline total cholesterol level was 173 mg/dl, after 50 d on the HF diet it was 177 mg/dl and after 50 d on the LF diet, 173 mg/dl. The differences were not significant, and there were no significant changes in either the LDL or HDL cholesterol levels with either diet. Triglyceride levels, and consequently very low density lipoprotein levels, rose significantly on the LF, higher CHO diet compared to the levels found in the subjects on the HF diet (91.5 and 66.4 mg/dl respectively, P < 0.002). The linoleic acid content of the plasma, platelets, and red blood cells was significantly (P < 0.05) reduced in the LF diet compared to HF diet, without any obvious physiological effects. Hence, many earlier observations indicating reductions in plasma lipid levels when people are on LF diets may be due to changes in the FAC of the diet, not the reduction in fat calories.

Decreased systemic thromboxane A2 biosynthesis in normal human subjects fed a salmon-rich diet

Nine normal male subjects were fed a reference diet typical of that consumed in the United States and a diet containing approximately 450 g salmon (salmon-rich diet). The salmon diet contained approximately 6 g omega 3 fatty acids that comprised 2.0% energy intake/d for each individual. The percent energy contribution of protein, carbohydrate, and fat (19%, 56%, and 25%, respectively) was identical for the two diets. Urinary excretion of 2,3-dinor-thromboxane B2 was significantly lower (0.74 +/- 0.26 ng/24 h) with the salmon diet compared with the reference diet (0.95 +/- 0.31 ng/24 h). In addition, in vitro generation of thromboxane B2 in response to collagen-stimulated aggregation of platelet-rich plasma from subjects consuming the salmon diet was reduced (1.87 +/- 0.79 ng/mL) compared with subjects consuming the reference diet (3.10 +/- 1.81 ng/mL). Urinary 2,3-dinor-6-oxo-prostaglandin F1 alpha excretion in subjects was not significantly different between the salmon diet (0.69 +/- 0.33 ng/24 h) and the reference diet (0.81 +/- 0.44 ng/24 h).

The urinary excretion of thiobarbituric acid reactive substances and malondialdehyde by normal adult males after consuming a diet containing salmon

In this study we investigated the output of thiobarbituric acid reactive substances (TBARS) and malondialdehyde (MDA), as thiobarbituric acid (TBA)-MDA adduct, in the urine from subjects eating a diet in which the only source of n-3 long-chain, polyunsaturated fatty acids was fresh salmon. Nine healthy men, ages 30-65, were confined in the United States Department of Agriculture Western Human Nutrition Research Center, San Francisco, CA, for 100 d; food intake and exercise levels were controlled. All subjects were placed on a stabilization diet (StD) for 20 d, then six were fed the salmon diet for 40 d. The others remained on the StD. The groups switched diets for the last 40 d. Both diets were isocaloric (16% protein, 54% CHO and 30% fat by energy %). The salmon diet contained 7.5% of calories from n-6 fatty acids (FAs) and 2% from n-3 FAs, primarily eicosapentaenoic acid and docosahexaenoic acid in a 50:60 ratio, while the StD contained 7.5% from n-6 FAs and < 0.3% n-3 FAs (with presumably no significant amounts of C20 or C22 n-3 FAs). Twenty-four hour urinary output was collected, and 2% 3-d pool samples prepared for analysis of urinary TBARS and the TBA-MDA adduct. The total urinary output of each individual varied considerably, and on a daily basis the concentration of autoxidation products in an individual's urine varied also.(ABSTRACT TRUNCATED AT 250 WORDS)

Dietary alpha-linolenic acid alters tissue fatty acid composition, but not blood lipids, lipoproteins or coagulation status in humans

We examined the effect of dietary alpha-linolenic acid (ALA) on the indices of lipid and coagulation status and on the fatty acid composition of serum and peripheral blood mononuclear cell (PBMNC) lipids in ten healthy men (age 21-37 yr) who consumed all their meals at the Western Human Nutrition Research Center for 126 d. There was a stabilization period of 14 d at the start when all 10 subjects consumed the basal diet (BD) containing 23.4 energy percent (en%) fat and two intervention periods of 56 d each. During the first intervention period, 5 subjects consumed the BD containing 23.4 en% fat, and 5 subjects consumed a diet providing 6.3% calories from alpha-linolenic acid [flaxseed oil (FSO) diet containing 28.8 en% fat]. Diets were crossed over between the two groups during the second intervention period. Feeding the FSO diet did not significantly alter serum triglycerides, cholesterol, high-density lipoproteins, low-density lipoproteins, apoprotein A-I and apoprotein B when compared to the corresponding values in the subjects fed the BD, nor was there any effect of the FSO diet on the bleeding time, prothrombin time and partial prothrombin time for these subjects. Feeding the ALA-containing diet did cause a significant increase in ALA concentration in serum (P < 0.001) and PBMNC lipids (P < 0.05). It also caused a significant increase (P < 0.05) in the eicosapentaenoic and docosapentaenoic acid contents of PBMNC lipids, and a decrease (P < 0.01) in linoleic and eicosatrienoic acid contents of serum lipids.(ABSTRACT TRUNCATED AT 250 WORDS)

Salmon diet and human immune status

We examined the effect of feeding a salmon-containing diet on the immune status of nine healthy men (age 30-65 years) who lived at the metabolic suite of the Western Human Nutrition Research Center for 100 days. During the first 20 days all nine subjects consumed a basal diet (BD). For the next 40 days, three subjects continued to consume BD, while the diet of remainder six subjects was modified to contain 500 g salmon every day. During the last 40 days, the diets of the two groups were crossed over. Feeding 500 g salmon daily for 40 days did not significantly suppress the blastogenesis of peripheral blood mononuclear cells cultured with phytohemagglutinin, Concanavalin A, protein A or pokeweed when compared to the corresponding pre-salmon diet values. It also did not significantly affect the delayed hypersensitivity skin response to seven recall antigens, serum concentrations of immunoglobulins G, M, and A, and complement fractions C3 and C4. Our results indicate that the short-term consumption of a high fish (salmon)-containing diet does not adversely affect the immune system, as has been reported with fish oil supplements.

Effect of a salmon diet on the distribution of plasma lipoproteins and apolipoproteins in normolipidemic adult men

The effects of n-3 fatty acids on plasma lipids, lipoproteins and apoproteins have usually been studied in humans after feeding of purified fish oil. This study describes the effect of a natural diet, containing salmon as the source of n-3 fatty acids, on these parameters as compared to a diet very low in n-3 fatty acids. The subjects were nine normolipidemic, healthy males who were confined to a nutrition suite for 100 days. During the first 20 days of the study the participants were given a stabilization diet consisting of 55% carbohydrates, 15% protein, and 30% fat. The n-3 content of this diet was less than 1%, and it contained no 20- or 22-carbon n-3 fatty acids. After the stabilization period the men were split into two groups, one group continued on the stabilization diet while the other received the salmon diet that contained approximately 2.1 energy percent (En%) of calories from 20- and 22-carbon n-3 fatty acids. Both diets contained equal amounts of n-6 fatty acids. This regime continued for 40 days, then the two groups switched diets for the remainder of the study. Plasma triglycerides were lowered significantly (p less than 0.01) and high density lipoprotein cholesterol (HDL-C) was significantly elevated (p less than 0.01) after the men consumed the salmon diet for 40 days. The very low density lipoproteins (VLDL) were lowered, but the trend did not reach statistical significance during the intervention period.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of a salmon diet on blood clotting, platelet aggregation and fatty acids in normal adult men

This study was designed to measure the effect of dietary n-3 fatty acids (FA) on platelets and blood lipids. Healthy men (n = 9), ages 31 to 65, were fed diets in which salmon was the source of n-3 fatty acids. They were confined in a nutrition suite at this Center for 100 days. Food intake and exercise levels were rigidly controlled. Initially they were placed on a stabilization diet for 20 days, then six men were fed the salmon diet for 40 days. The others remained on the stabilization diet. The two groups switched diets for the last 40 days of the study. Both diets were isocaloric [16% protein, 54% carbohydrate, and 30% fat by energy-% (En%)]. The salmon diet contained 7.5% of calories from n-6 FA and 2% from n-3 FA, primarily eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in a 40:60 ratio, while the stabilization diet contained 7.5% of calories from n-6 FA and less than 0.3% n-3 FA, mainly 18:3n-3. The bleeding time was unaffected by the diets in this study. The prothrombin time was shortened (11.6 sec. vs. 12.6 sec., p less than 0.01) for the subjects consuming the salmon diet as compared to that measured after 20 days of the stabilization diet. Mean platelet volume increased significantly during the period in which the volunteers consumed the salmon diet compared to the baseline diet (p less than 0.01), while the mean platelet levels decreased. Platelet aggregation (PA) was measured in platelet rich plasma before, during, and after the salmon diet using collagen, ADP, arachidonic acid (AA), and thrombin agonists. The PA threshold for ADP was significantly increased for the subjects on the salmon diet (p less than 0.05). No change in the PA threshold was detected for collagen or thrombin. The PA threshold for AA was unchanged also, but the platelets in subjects consuming the salmon diet had a prolonged time to maximum aggregation (p less than 0.01) with this reagent compared to platelets from men on the stabilization diet. Plasma, red cell, and platelet total FA composition was determined by capillary GLC. While the men consumed the salmon diets, there were marked increases (3 to 10-fold) in the EPA and DHA levels in all blood components with concomitant decreases in linoleic acid and AA levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of type of dietary fat on indices of immune status of rabbits

We have compared the effects of dietary saturated and unsaturated fats of the n-6 and n-3 types on the immune status of male New Zealand white rabbits. Four groups of rabbits (n = 8) were fed purified diets containing one of the following fats (7.6% w/w, 23 kcal%) for 5 mo, hydrogenated soybean oil (HSO); safflower oil (SFO); linseed oil (LSO); or menhaden oil (MHO). In vitro proliferation of peripheral blood lymphocytes (PBL) cultured with T-cell mitogens was significantly higher in the LSO group than in the other three groups, and that in the HSO group was higher than in the MHO and SFO groups which were not different from each other. Proliferation of PBL in response to B-cell mitogens was significantly higher in the LSO group than in the SFO and MHO groups. In vitro proliferation of splenocytes (SPC) from the LSO group was higher than that from the other three groups only when SPC were cultured with T-cell mitogens. Serum antibody levels against bovine serum albumin were significantly higher in the LSO group than in the SFO group after second and third immunizations. Spleen weights, number of SPC or PBL, and delayed-type hypersensitivity were not different among the four dietary groups. Our data show that linseed oil diet enhanced several indices of immune status in rabbits.

Absorption and transport of fat in mammals with emphasis on n-3 polyunsaturated fatty acids

The current state of knowledge concerning the absorption and transport of dietary fat with emphasis on long-chain polyunsaturated n-3 fatty acids in mammals is reviewed. It is apparent that long-chain polyunsaturated n-3 fatty acids, either as free acids or as part of triglycerides, are readily absorbed in the gut and transported by the circulatory system. Indeed, it would appear that long-chain polyunsaturated n-3 fatty acids are digested, absorbed and transported similarly to other long-chain fatty acids with only minor variations, although there is much that is still not understood about these processes. The main unresolved issues in the area of the absorption and transport of long-chain polyunsaturated n-3 fatty acids appear to be: 1) If they, when located in the 2-position of triglycerides, have unique metabolic pathways; and 2) whether the unnatural forms, i.e., methyl or ethyl ester derivatives, are suitable vehicles for administration as dietary supplements. The effect in man of dietary, long-chain polyunsaturated n-3 fatty acids on blood serum lipid and lipoprotein levels, particularly the low density lipoproteins, remains controversial, except for the well-documented reduction in serum triglyceride levels. Also, there is uncertainty regarding their distribution and metabolism in tissues. Finally, if the consumption of long-chain polyunsaturated n-3 fatty acids has beneficial health consequences, what is the appropriate therapeutic dose? In view of these important, unresolved issues and uncertainties, it would seem prudent to direct additional research toward a better understanding of the overall process by which fat is digested, absorbed and transported.

The influence of dietary fat on the lipogenic activity and fatty acid composition of rat white adipose tissue

The in vivo fatty acid synthesis rate, selected enzyme activities and fatty acid composition of rat white adipose tissue from animals fed semisynthetic diets of differing fat type and content were studied. All animals were starved for 48 hr and then refed a fat-free (FF) diet for 48 hr. They were then divided into three groups. One group was continued on the FF diet for 48 hr. Another group was fed a diet containing 44% of calories from corn oil (CO). The final group was fed a diet containing 44% of calories from completely hydrogenated soybean oil (HSO). The animals on the FF diet had a marked increase in adipose tissue fatty acid synthesis during the 96-hr feeding period (as measured by 3H incorporation into adipose fatty acids). Addition of either CO or HSO to the diets did not significantly inhibit fatty acid synthesis in dorsal or epididymal adipose tissue. The activities of the enzymes' fatty acid synthetase, ATP-citrate lyase and glucose-6-phosphate dehydrogenase increased on the FF diet and generally were not inhibited significantly by the addition of either fat to the diets. Linoleic acid was the major polyunsaturated fatty acid (ca. 22%) in adipose tissue. Monounsaturated fatty acids (palmitoleic, oleic, cis-vaccenic) made up ca. 38% of the total adipose fatty acids, while saturated fatty acids accounted for about 32% (myristic, palmitic and stearic). White adipose tissue in mature male rats was a major depot for n-3 fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of fat-free, saturated and polyunsaturated fat diets on rat liver and plasma lipids

The liver and plasma lipids and fatty acid composition of rats fed synthetic diets of differing fat type and content were studied. All animals were starved for 48 hr and then refed a high carbohydrate, fat-free diet for 48 hr. They were then divided into three groups and fed for an additional 48 hrs the following: group 1, the fat-free diet; group 2, a diet containing 44% of calories from corn oil; and group 3, a diet containing 44% calories from completely hydrogenated soybean oil. The total lipid concentration of the liver in the animals on the fat-free diet was elevated at 72 and 96 hr. The addition of either saturated or unsaturated fat in the diet at 48 hr prevented this accumulation. The total phospholipid and cholesterol concentrations of the liver were relatively uninfluenced by any diet in this study. Plasma total fatty acid concentration was elevated at 72 hr in the animals on a fat-free diet compared to those fed the stock diet, starved for 48 hr or fed the fat-containing diets. By 96 hr, however, plasma fatty acid concentrations in all groups were similar to those in animals fed only the stock diet. The release of de novo synthesized fatty acids into plasma from the liver was strongly inhibited by dietary fat, either saturated or polyunsaturated. With the fat-free diet there was a significant increase in the saturated and monounsaturated fatty acids in both liver and plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of nutritional status on the fatty acid composition of rat liver and cultured hepatocytes

The lipid concentration and fatty acid composition of the whole liver and of cultured hepatocytes isolated from the livers of rats fed ad libitum (fed), fasted for 24 hr (fasted), or fasted for 48 hr and then refed a fat-free, high carbohydrate diet for 48 hr (refed) was studied. Hepatocytes were maintained as monolayer cultures in serum-free, lipid-free media and their fatty acid composition was analyzed at 3, 24, 48, 72 and 96 hr. The livers of fed animals, as well as their hepatocytes, contained less total lipid than those from animals on either of the other dietary regimes. Livers of fasted animals had three times the amount of lipid found in the livers of fed animals, and the livers of refed animals contained five times the amount of lipid as the livers of fed animals (all based on mg lipid/g wet weight of liver). The fatty acid composition of hepatocytes after 3 hr of culturing was very similar to that of fresh liver when compared in each of the dietary regimes. However, while the fatty acid compositions of livers and hepatocytes from fed and fasted animals were similar, the pattern in liver of refed animals was quite distinct from that of the fed animals. In the fed and fasted animals palmitic acid (16:0), stearic acid (18:0), oleic acid (18:1[n-9]), linoleic acid (18:2[n-6]) and arachidonic acid (20:4[n-6]) were the major fatty acids of the liver; in refed animals 16:0, palmitoleic acid (16:1[n-7]), 18:0, 18:1(n-9) and cis-vaccenic acid (the n-7 isomer of oleic acid) were the major fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of prior nutritional status on the activity of lipogenic enzymes in primary monolayer cultures of rat hepatocytes

Effect of prior nutritional status of the animal on the activity of lipogenic enzymes and the fatty acid content of cultured hepatocytes was investigated. Hepatocytes were isolated from rats that were starved for 24 h ('starved') or continuously fed ('fed'), or starved for 48 h and then re-fed for 48 h ('re-fed') with a carbohydrate-rich fat-free diet, and maintained as monolayer cultures for 96 h in a serum-free glucose-rich medium (Waymouth's MB752/1) supplemented with insulin, dexamethasone and tri-iodothyronine. The fatty acid content and the activities of acetyl-CoA carboxylase, fatty acid synthase, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were determined initially at 3 h after plating and then every 24 h. Initially the activities of all the four enzymes were highest in hepatocytes isolated from the re-fed rats and lowest in those from the starved rats. With time in culture, the activity of all these enzymes increased severalfold (2-5, depending on the enzyme under consideration) in hepatocytes isolated from fed and starved rats, whereas there was a severalfold (2-5) decrease in the activity of these enzymes in hepatocytes isolated from re-fed rats. The initial fatty acid content of the hepatocytes from re-fed rats was 2-3 times that in the other two groups of hepatocytes. The fatty acid content seemed to increase in all three groups of hepatocytes during the 96 h in culture, but these apparent increases were not statistically significant.

Effect of cholesterol supplementation of diets of thyroidectomized dogs on the fatty acid composition of erythrocyte phospholipids and plasma phosphatidylcholine

Thyroidectomized foxhounds were fed: (a) a control diet, (b) the control diet supplemented with 15% beef tallow or cottonseed oil, with or without added cholesterol, or (c) the control diet supplemented with beef tallow (15%), safflower oil (1.5%) and cholesterol. After 23 weeks on the diet, the content of the individual phospholipids of the erythrocytes was not altered appreciably. However, supplementing either the saturated (beef tallow) or polyunsaturated (cottonseed oil) diets with cholesterol produced similar changes in the fatty acid compositions of the phospholipid classes. Most consistently, there were increases in the percentages on 18:2 omega 6 and 20:3 omega 6 and decreases in the percentages of 20:4 omega 6 and 22:4 omega 6. Cholesterol supplementation of the diets similarly affected the fatty acid composition of phosphatidylcholine isolated from the platelet-free plasma of these animals.

Effects of diets high in saturated fat and cholesterol on the lipid composition of canine platelets

The phospholipid composition of platelets from dogs on various experimental diets was determined. Thyroidectomized foxhounds were fed a control diet or the control diet supplemented with (1) beef tallow, (2) beef tallow and cholesterol, or (3) beef tallow, cholesterol, and safflower oil for 23 weeks prior to isolation of platelets. Platelets from animals fed the control diet contained 36.7% phosphatidylcholine (PC), 22.8% phosphatidylethanolamine (PE), 18.4% sphingomyelin (Sph), 11.8% phosphatidylserine (PS), 6.3% phosphatidylinositol (PI), and 2.2% lysophosphatidylcholine. The PE was 77.6% in the plasmalogen form. No highly significant changes in the phospholipid class composition resulted from the experimental diets. Cholesterol supplementation of the diets, however, caused consistent alterations in the fatty acid compositions of the platelet phospholipids including increases in the percentages of 18:1 omega 9 (oleic acid), 18:2 omega 6 (linoleic acid), and 20:3 omega 6 (homo-gamma linolenic acid) and a decrease in the percentage of 20:4 omega 6 (arachidonic acid). Addition of safflower oil to the tallow-cholesterol diet partially reversed these effects. These cholesterol-induced alterations in fatty acid composition could be due to exchange with plasma lipids, de novo synthesis, or altered platelet metabolism. The mechanism remains to be determined.

Pilot epidemiological studies in thrombosis

Some differences in the blood of farmers in Nurmijarvi, Finland, Canino, Italy, and Beltsville, Maryland in the United States apparently were associated with differences, among the areas, in the farmers' diets. Those associations suggested that diets that are high in saturated fats (Nurmijarvi) could predispose humans to develop intravascular disease. Such predisposition has been observed in experimental animals. Low levels of the parameters that are considered active in such predisposition apparently were associated with diets that were low in saturated fats (Canino) or with diets that were low in saturated and high in unsaturated fats (Beltsville). Within the limits of the experimental design, the data from the three population groups indicated that a more comprehensive study might establish a relation between diet and intravascular disease in humans.