Dietary α-linolenic acid increases brain but not heart and liver docosahexaenoic acid levels

Fish oil-enriched diets increase n−3 FA in tissue phospholipids; however, a similar effect by plant-derived n−3 FA is poorly defined. To address this question, we determined mass changes in phospholipid FA, individual phospholipid classes, and cholesterol in the liver, heart, and brain of rats fed diets enriched in flax oil (rich in 18∶3n−3), fish oil (rich in 22∶6n−3 and 20∶5n−3), or safflower oil (rich in 18∶2n−6) for 8 wk. In the heart and liver phospholipids, 22∶6n−3 levels increased only in the fish oil group, although rats fed flax oil accumulated 20∶5n−3 and 22∶5n−3. However, in the brain, the flax and fish oil diets increased the phospholipid 22∶6n−3 mass. In all tissues, these diets decreased the 20∶4n−6 mass, although the effect was more marked in the fish oil than in the flax oil group. Although these data do not provide direct evidence for 18∶3n−3 elongation and desaturation by the brain, they demonstrate that 18∶3n−3-enriched diets reduced tissue 20∶4n−6 levels and increased cellular n−3 levels in a tissuedependent manner. We hypothesize, based on the lack of increased 22∶6n−3 but increased 18∶3n−3 in the liver and heart, that the flax oil diet increased circulating 18∶3n−3, thereby presenting tissue with this EFA for further elongation and desaturation.     

The effects of dietary α-linolenic acid compared with docosahexaenoic acid on brain, retina, liver, and heart in the guinea pig

The aim of this study was to compare two different strategies to elevate brain, retina, liver, and heart docosahexaenoic acid (DHA) levels in guinea pigs. Fist, we used an increasing dose of α-linolenic acid (AIA) relative to a constant linoleic acid (LA) intake, and second, we used two levels of dietary DHA provided in conjunction with dietary arachidonic acid (AA). The percentage DHA and AA of total phospholipids in retina, liver, and heart, and in the brain phosphotidylethanolamine and phosphatidylcholine was studied in female pigmented guinea pigs (3 wk old) fed one of five semisynthetic diets containing 10% (w/w) lipid for 12 wk. The LA content in the diets was constant (17% of total fatty acids), with the ALA content varying from 0.05% (diet SFO), to 1% (diet Mix), and to 7% (diet CNO). Two other diets LCP) and LCP3) had a constant LA/ALA ratio (17.5∶1) but varied in the levels of dietary AA and DHA supplementation. Diet LCP1 was structured to closely replicate the principal long chain polyunsaturated fatty acids (PUFA) found in human breast milk and contained 0.9% AA and 0.6% DHA (% of total fatty acids) whereas diet LCP3 contained 2.7% AA and 1.8% DHA. At the end of the study, animals were sacrificed and tissues taken for fatty acid analyses. We found no significant effects of diets on the growth of guinea pigs. Diets containing ALA has profoundly different effects on tissue fatty acid compositions compared with diets which contained the long chain PUFA (DHA and AA). In the retina and brain phospholipids, high-ALA diets or dietary DHA supplementation produced moderate relative increases in DHA levels. There was no change in retinal or brain AA proportions following dietary AA supplementation, even at the highest level. This was in contrast to liver and heart where tissue DHA proportions were low and AA predominated. In these latter tissues, dietary ALA had little effect on tissue DHA proportions although the proportion of AA was slightly depressed at the highest dietary ALA intake, but dietary DHA and AA supplements led to large increases (up to 10-fold) in the proportions of these PUFA. Tissue uptake of dietary AA and DHA appeared maximal for the LCP1 diet (replicate of breast milk) in the heart. There were no significant changes in the plasma levels of 11-dehydrothromboxane B₂ (a thromboxane A₂ metabolite), for any diet. The data confirm that dietary ALA is less effective than dietary DHA supplementation (on a gram/gram basis) in increasing tissue DHA levels and that tissues vary greatly in their response to exogenous AA and DHA, with the levels of these long chain metabolites being most resistant to change in the retina and brain compared with liver and heart. Dietary DHA markedly increased tissue DHA proportions in both liver and heart, whereas the major effect of dietary AA was in the liver. Future studies of the effects of dietary DHA and AA supplementation should examine a variety of tissues rather than focusing only on neural tissue.     

Regulation of the α-tocopherol transfer protein in mice: Lack of response to dietary vitamin E or oxidative stress

The α-tocopherol transfer protein (TTP) plays an important role in the regulation of plasma α-tocopherol concentrations. We hypothesized that hepatic TTP levels would be modulated by dietary vitamin E supplementation and/or by oxidative stress. Mice were fed either a High E (1150 mg RRR-α-tocopheryl acetate/kg diet) or a Low E (11.5 mg/kg diet) diet for 2 wk. High E increased plasma and liver α-tocopherol concentrations approximately 8- and 40-fold, respectively, compared with Low E-fed mice, whereas hepatic TTP increased approximately 20%. Hepatic TTP concentrations were unaffected by fasting (24 h) in mice fed either diet. To induce oxidative stress, chow-fed mice were exposed for 3 d to environmental tobacco smoke (ETS) for 6 h/d (total suspended particulate, 57.4±1.8 mg/m3). ETS exposure, while resulting in pulmonary and systemic oxidative stress, had no effect on hepatic α-tocopherol concentrations or hepatic TTP. Overall, changes in hepatic TTP concentrations were minimal in response to dietary vitamin E levels or ETS-related oxidative stress. Thus, hepatic TTP concentrations may be at sufficient levels such that they are unaffected by either modulations of dietary vitamin E or by the conditions of environmentally related oxidative stress used in the present studies. The first and second investigators contributed equally to this work.     

Increased α-linolenic acid intake increases tissue α-linolenic acid content and apparent oxidation with little effect on tissue docosahexaenoic acid in the guinea pig

The essential fatty acids do not have identical roles in nutrition. Linoleic acid (LA) accumulates throughout the body of most mammals, whereas α-linolenic acid (ALA) is rarely found in tissue lipids to the same extent as LA. It has been argued that this is the result of metabolism of ALA to docosahexaenoic acid (DHA) or that ALA is rapidly β-oxidized to acetyl CoA and CO₂. In this study, we consider the effect of high and low ALA levels on the tissue distribution of ALA and other n-3 polyunsaturated fatty acids (PUFA) in all tissues. Guinea pigs were fed one of two defined diets for 3 wk from wearning with both diets containing 1.8% (by weight) of LA and either 1.7% ALA or 0.03% ALA. The high ALA diet was associated with significantly increased ALA levels in all tissues except the brain and significantly increased levels of long-chain n-3 PUFA in all tissues except intestines, brain, carcass, and skin. The long-chain n-3 PUFA content of the whole body was less than 5% of that of the ALA content in both diet groups, and the major long-chain n-3 PUFA (>66% of total) in the body was 22∶5n−3. The brain was the only tissue where the DHA content exceeded that of 22∶5n−3. On the low ALA diet, there appeared to be conservation of ALA based on a comparison of the ratio of LA to ALA in the tissues compared with that in the diet. On the high ALA diet there was a loss of ALA relative to LA in the tissues compared with the diet. These studies suggest that the low levels of tissue ALA in the guinea pig are likely the result of β-oxidation or excretion via the skin and fur rather than metabolism to DHA.     

Metabolism of dietary α-linolenic acid vs. eicosapentaenoic acid in rat immune cell phospholipids during endotoxemia

Short-term (i.e., 3 d) continuous enteral feeding of diets containing eicosapentaenoic (EPA) and γ-linolenic (GLA) polyunsaturated fatty acids (PUFA) to endotoxemic rats reduces the levels of arachidonic acid (AA) and linoleic acid (LA) in alveolar macrophage (AM) and liver Kupffer and endothelial (K&E) cell phospholipids with attendant decreases in prostaglandin formation by these cells in vitro. Diets that contain α-linolenic acid (LNA) as a substrate for endogenous formation of EPA may not be as effective in facilitating these immune cell modifications given the limited activity of Δ6 desaturase. In the present study we compared the effectiveness of an LNA-enriched diet vs. an (EPA+GLA)-enriched diet to displace phospholipid AA from AM and liver K&E cells in vivo in endotoxemic rats fed enterally for 3 or 6 d. We determined the fatty acid composition of AM and K&E cell phospholipids by gas chromatography. We found that AM and K&E cells from rats that had received the EPA+GLA diet for 3 d had significantly (P<0.001) higher mole percentage of EPA and the GLA metabolite, dihomoGLA, than corresponding cells from rats given the LNA diet or a control diet enriched with LA. Rats given the LNA diet had relatively low levels of stearidonic acid, EPA and other n−3 PUFA, while rats given the LA diet had low levels of GLA and dihomoGLA. We conclude that diets enriched with LNA or LA may not be as effective as those enriched with FPA+GLA for purposes of fostering incorporation of EPA or dihomoGLA into and displacement of AA from macrophage phospholipids under pathophysiologic conditions commonly found in acutely septic patients.     

Dietary α-linolenic acid lowers postprandial lipid levels with increase of eicosapentaenoic and docosahexaenoic acid contents in rat hepatic membrane

This study was designed to examine the effects of dietary n−3 and n−6 polyunsaturated fatty acids (PUFA) on postprandial lipid levels and fatty acid composition of hepatic membranes. Male Sprague-Dawley rats were trained for a 3−h feeding protocol and fed one of five semipurified diets: one fat-free diet or one of four diets supplemented with 10% (by weight) each of corn oil, beef tallow, perilla oil, and fish oil. Two separate experiments were performed, 4-wk long-term and 4-d short-term feeding models, to compare the effects of feeding periods. Postprandial plasma lipid was affected by dietary fats. Triacylglycerol (TG) and total cholesterol levels were decreased in rats fed perilla oil and fish oil diets compared with corn oil and beef tallow diets. Hepatic TG and total cholesterol levels were also reduced by fish oil and perilla oil diets. Fatty acid composition of hepatic microsomal fraction reflected dietary fatty acids and their metabolic conversion. The major fatty acids of rats fed the beef tallow diet were palmitic, stearic, and oleic. Similarly, linoleic acid (LA) and arachidonic acid in the corn oil group, α-linolenic acid (ALA) and eicosapentaenoic acid (EPA) in the perilla oil group, and palmitic acid and docosahexaenoic acid (DHA) in the fish oil group were detected in high proportions. Both long- and short-term feeding experiments showed similar results. In addition, microsomal DHA content was negatively correlated with plasma lipid levels. Hepatic lipid levels were also negatively correlated with EPA and DHA contents. These results suggest that n−3 ALA has more of a hypolipidemic effect than n−6 LA and that the hypolipidemic effect of n−3 PUFA may be partly related to the increase of EPA and DHA in hepatic membrane.     

Vitamin A deficiency enhances docosahexaenoic and Osbond acids in liver of rats fed an α-linoleic acid-adequate diet

The synthesis of docosahexaenoic (DHA, 22∶6n−3) and Osbond acid (OA, 22∶5n−6) is regulated by the heterodimer of peroxisome proliferator-activated receptor and retinoid X receptor (RXR). 9-Cis retinoic acid, a metabolite of vitamin A, is the most potent ligand of RXR. We tested whether vitamin A deficiency impairs DHA and OA synthesis in rats fed a vitamin A- and α-linolenic acid (ALA)-sufficient (VASALAS), vitamin A-sufficient and ALA-deficient (VASALAD), vitamin A-deficient and ALA-sufficient (VADALAS), or vitamin A- and ALA-deficient (VADALAD) diet. After 7 wk of feeding, liver and colon choline (CPG) and ethanolamine (EPG) phosphoglyceride FA were analyzed. The VADALAS compared with the VASALAS rats had elevated levels of both DHA (P<0.05) and OA (P<0.05) in liver CPG and EPG. In contrast, the VADALAD group had a lower DHA (P<0.01) and higher OA (P<0.005) level in CPG and EPG of both tissues than their VASALAD counterparts. ALA deficiency reduced DHA and enhanced OA levels in liver and colon CPG and EPG in both the vitamin A-sufficient (VASALAS vs. VASALAD) and-deficient (VADALAS vs. VADALAD) rats (P<0.005). The study demonstrates that ALA deficiency reduced DHA and enhanced OA levels in tissue membranes, and dietary vitamin A deficiency has a profound effect on membrane DHA and OA in rat tissues. Both vitamin A and DHA are involved in a myriad of vital physiological functions pertaining to growth and development and health. Hence, there is a need for a further study to unravel the mechanism by which vitamin A influences membrane DHA and OA.     

Comparison of growth and fatty acid metabolism in rats fed diets containing equal levels of γ-linolenic acid from high γ-linolenic acid canola oil or borage oil

We have utilized transgenic technology to develop a new source of γ-linolenic acid (GLA) using the canola plant as a host. The aim of the present study was to compare the growth and fatty acid metabolism in rats fed equal amounts of GLA obtained from the transgenic canola plant relative to GLA from the borage plant. Young male Sprague-Dawley rats (n=10/group) were randomized and fed a purified AIN93G diet (10% lipid by weight) containing either a mixture of high GLA canola oil (HGCO) and corn oil or a control diet containing borage oil (BO) for 6 wk. GLA accounted for 23% of the triglyceride fatty acids in both diets. Growth and diet consumption were monitored every 2–3 d throughout the study. At study termination, the fatty acid composition of the liver and plasma phospholipids was analyzed by gas chromatography. The growth and diet consumption of the HGCO group were similar to the BO group. There were no adverse effects of either diet on the general health or appearance of the rats, or on the morphology of the major organs. There was no significant difference between the diet groups for total percentage of n−6 polyunsaturated fatty acids present in either the total or individual phospholipid fractions of liver or plasma. The relative percentage of GLA and its main metabolite, arachidonic acid, in each phospholipid fraction of liver or plasma were also similar between groups. The percentage of 18∶2n−6 in liver phosphatidylethanolamine and phosphatidylinositol/serine was higher (P<0.05) and 22∶5n−6 was lower in the HGCO group than the BO group. This finding could be attributed to the higher 18∶3n−3 content in the HGCO diet than the BO diet. Results from this long-term feeding study of rats show for the first time that a diet containing transgenically modified canola oil was well-tolerated, and had similar biological effects, i.e., growth characteristics and hepatic metabolism of n−6 fatty acids, as a diet containing borage oil.     

Application of nickel(II) complexes to the efficient synthesis of α- or β-amino acids

Nonproteinogenic α- or β-amino acids have attracted tremendous attention, as they are widely utilized for biological, biochemical, pharmaceutical, and asymmetric chemical investigations. Recently, we developed a series of new strategies for preparing achiral and chiral nickel(ii) complexes for the synthesis of amino acids. We applied these new methods utilizing chiral nickel(ii) complexes for the asymmetric Mannich reaction to synthesize enantiopure α,β-diamino acids, the enantioselective tandem conjugate addition-elimination reaction to prepare glutamic acid derivatives, the Suzuki coupling reaction to yield β(2)-amino acid derivatives, the asymmetric Mannich reaction to synthesize 3-aminoaspartate, the asymmetric Michael addition reaction to give β-substituted-α,γ-diaminobutyric acid derivatives, the asymmetric alkylation reaction to prepare linear ω-trifluoromethyl containing amino acids, and the asymmetric Michael addition reaction to synthesize syn-β-substituted tryptophans.     

Changes of the transcriptional and fatty acid profiles in response to n−3 fatty acids in SH-SY5Y neuroblastoma cells

Synthesis of docosahexaenoic acid (DHA) from its metabolic precursors contributes to membrane incorporation of this FA within the central nervous system. Although cultured neural cells are able to produce DHA, the membrane DHA contents resulting from metabolic conversion do not match the high values of those resulting from supplementation with preformed DHA. We have examined whether the DHA precursors down-regulate the incorporation of newly formed DHA within human neuroblastoma cells. SH-SY5Y cells were incubated with gradual doses of alpha-linolenic acid (alpha-LNA), EPA, or docosapentaenoic acid (DPA), and the incorporation of DHA into ethanolamine glycerophospholipids was analyzed as a reflection of synthesizing activity. The incorporation of EPA, DPA, and preformed DHA followed a dose-response saturating curve, whereas that of DHA synthesized either from alpha-LNA, EPA, or DPA peaked at concentrations of precursors below 15-30 microM and sharply decreased with higher doses. The mRNA encoding for six FA metabolism genes were quantified using real-time PCR. Two enzymes of the peroxisomal beta-oxidation, L-bifunctional protein and peroxisomal acyl-CoA oxidase, were expressed at lower levels than fatty acyl-CoA ligase 3 (FACL3) and delta6-desaturase (delta6-D). The delta6-D mRNA slightly increased between 16 and 48 h of culture, and this effect was abolished in the presence of 70 microM EPA. In contrast, the EPA treatment resulted in a time-dependent increase of FACL3 mRNA. The terminal step of DHA synthesis seems to form a "metabolic bottleneck," resulting in accretion of EPA and DPA when the precursor concentration exceeds a specific threshold value. We conclude that the critical precursor- concentration window of responsiveness may originate from the low basal expression level of peroxisomal enzymes.     

Effects of diets enriched in n−6 or n−3 fatty acids on cholesterol metabolism in older rats chronically fed a cholesterol-enriched diet

Hypocholesterolemic effects in older animals after long-term feeding are unknown. Therefore, aged rats (24 wk of age) fed a conventional diet were shifted to diets containing 10% perilla oil [PEO; oleic acid+linoleic acid+α-linolenic acid; n−6/n−3, 0.3; polyunsaturated fatty acid/saturated fatty acid (P/S), 9.6], borage oil [oleic acid+linoleic acid+α-linolenic acid; n−6/n−3, 15.1; P/S, 5.3], evening primrose oil (FPO; linoleic acid+γ-linolenic acid; P/S, 10.5), mixed oil (MIO; oleic acid+linoleic acid+γ-linolenic acid+α-linolenic acid; n−6/n−3, 1.7; P/S, 6.7), or palm oil (PLO; palmitic acid+oleic acid+linoleic acid; n−6/n−3, 25.3; P/S, 0.2) with 0.5% cholesterol for 15 wk in this experiment. There were no significant differences in the food intake and body weight gain among the groups. The liver weight in the PEO (n−6/n−3, 0.3) group was significantly higher than those of other groups in aged rats. The serum total cholesterol and very low density lipoprotein (VLDL) +intermediate density lipoprotein (IDL)+low density lipoprotein (LDL)-cholesterol concentrations of the PLO (25.3) group were consistently higher than those in the other groups. The serum high density lipoprotein cholesterol concentrations of the PEO (0.3) and EPO groups were significantly lower than in the other groups at the end of the 15-wk feeding period. The liver cholesterol concentration of the PLO (25.3) group was significantly higher than those of other groups. There were no significant differences in the hepatic LDL receptor mRNA level among the groups. Hepatic apolipoprotein (apo) B mRNA levels were not affected by the experimental conditions. The fecal neutral steroid excretion of the PLO (25.3) group tended to be low compared to the other groups. The results of this study demonstrate that both n\t-6 fatty acid and n\t-3 fatty acids such as \gg-linolenic acid and \ga-linolenic acid inhibit the increase of serum total cholesterol and VLDL+IDL+LDL-cholesterol concentrations of aged rats in the presence of excess cholesterol in the diet compared with dietary saturated fatty acid.     

Arginine mimetics using α-guanidino acids: introduction of functional groups and stereochemistry adjacent to recognition guanidiniums in peptides

Arginine residues are broadly employed for specific biomolecular recognition, including in protein-protein, protein-DNA, and protein-RNA interactions. Arginine recognition commonly exploits the potential for bidentate electrostatic and hydrogen-bonding interactions. However, in arginine residues, the guanidinium functional group is located at the terminus of a flexible hydrocarbon side chain, which lacks the functionality to contribute to specific arginine-mediated recognition and may entropically disfavor binding. In order to enhance the potential for specificity and affinity in arginine-mediated molecular recognition, we have developed an approach to the synthesis of peptides that incorporates an α-guanidino acid as a novel arginine mimetic. α-Guanidino acids, derived from α-amino acids, with guanidinylation of the amino group, were incorporated stereospecifically into peptides on solid phase via coupling of an Fmoc amino acid to diaminopropionic acid (Dap), Fmoc deprotection, guanidinylation of the amine on solid phase, and deprotection, generating a peptide containing an α-functionalized arginine mimetic. This approach was examined by incorporating arginine mimetics into ligands for the Src, Grb, and Crk SH3 domains at the site of the key recognition arginine. Protein binding was examined for peptides containing guanidino acids derived from Gly, L-Val, L-Phe, L-Trp, D-Val, D-Phe, and D-Trp. We demonstrate that paralogue specificity and target site affinity may be modulated with the use of α-guanidino acid-derived arginine mimetics, generating peptides that exhibit enhanced Src specificity by selection against Grb and peptides that reverse the specificity of the native peptide ligand, with enhancements in Src target specificity of up to 15-fold (1.6 kcal mol(-1)).     

Effects of dietary supplementation of saturated fatty acids and of n−6 or n−3 polyunsaturated fatty acids on plasma and red blood cell membrane phospholipids and deformability in weanling guinea pigs

The fatty acid composition of plasma cholesteryl esters, plasma phospholipids, red blood cell (RBC) membrane phosphatidylcholine (corresponding to the outer membrane leaflet), and phosphatidylethanolamine (corresponding to the inner membrane leaflet) was investigated in weanling guinea pigs fed with diets of cacao (saturated fatty acids), sunflower oil [n−6 polyunsaturated fatty acids (PUFA)] or fish oil (n−3 PUFA) for 20 wk. RBC deformation was measured by means of a cell-transit analyzer (filtration) and a cone-plate rheoscope. The contents of saturated fatty acids in plasma phospholipids and RBC membrane leaflets were similar in all three groups. Diets with sunflower oil resulted in a high content of linoleic acid in plasma cholesteryl esters and in the outer leaflet of RBC membranes. Fatty acids of fish oil were mainly incorporated in plasma phospholipids and in the inner leaflet of RBC membranes. The arachidonic acid content was high in all groups in the plasma phospholipids and in the inner leaflet. The n−6 and n−3 PUFA were mainly incorporated in the inner leaflet. In all groups the polyunsaturated/saturated fatty acid ratio and the total PUFA content were similar in the inner RBC membrane. The RBC filtration times and the RBC deformation indices were not affected by the dietary treatment.     

The metabolism and n−6/n−3 ratio of essential fatty acids in rats: Effect of dietary arachidonic acid and a mixture of sesame lignans (sesamin and episesamin)

In this study, we examined the effect of dietary arachidonic acid (AA) and sesame lignans on the content and n-6/n-3 ratio of polyunsaturated fatty acid (PUFA) in rat liver and the concentrations of triglyceride (TG) and ketone bodies in serum. For 4 wk, rats were fed two types of dietary oils: (i) the control oil diet groups (CO and COS): soybean oil/perilla oil=5∶1, and (ii) the AA-rich oil group (AO and AOS): AA ethyl esters/palm oil/perilla oil=2∶∶1, with (COS and AOS) or without (CO and AO) 0.5% (w/w) of sesame lignans. Dietary AA and sesame lignans significantly affected hepatic PUFA metabolism. AA content and n-6/n-3 ratio in the liver were significantly increased in the AO group, despite the dietary total of n-6 PUFA being the same in all groups, while AOS diet reduced AA content and n-6/n-3 ratio to a level similar to the CO and COS groups. These results suggest that (i) dietary AA considerably affects the hepatic profile and n-6/n-3 ratio of PUFA, and (ii) dietary sesame lignans reduce AA content and n-6/n-3 ratio in the liver. In the AO group, the concentration of acetoacetate was significantly increased, but the ratio of β-hydroxybutyrate/acetoacetate was decreased. On the other hand, the AO diet increased the concentration of TG in serum by almost twofold as compared to other groups. However, the AOS diet significantly reduced serum IG level as compared to the AO group. In addition, the AOS diet signicantly increased the acetoacetate level, but reduced the β-hydroxybutyrate/acetoacetate ratio. These results suggest that dietary sesame lignans promote ketogenesis and reduce PUFA esterification into TG. This study resulted in two findings: (i) sesame lignans inhibited extreme changes of the n-6/n-3 ratio by reducing hepatic PUFA content, and (ii) the reduction of hepatic PUFA content may have occurred because of the effects of sesame lignans on PUFA degradation (oxidation) and esterification.     

Influence of dietary supplementation with long-chain n−3 or n−6 polyunsaturated fatty acids on blood inflammatory cell populations and functions and on plasma soluble adhesion molecules in healthy adults

Greatly increasing the amounts of flaxseed oil [rich in α-linolenic acid (ALNA)] or fish oil (FO); [rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] in the diet can decrease inflammatory cell functions and so might impair host defense. The objective of this study was to determine the effect of dietary supplementation with moderate levels of ALNA, γ-linolenic acid (GLA), arachidonic acid (ARA), DHA, or FO on inflammatory cell numbers and functions and on circulating levels of soluble adhesion molecules. Healthy subjects aged 55 to 75 yr consumed nine capsules per day for 12 wk. The capsules contained placebo oil (an 80∶20 mix of palm and sunflowerseed oils) or blends of placebo oil with oils rich in ALNA, GLA, ARA, or DHA or FO. Subjects in these groups consumed 2 g ALNA; approximately 700 mg GLA, ARA, or DHA; or 1 g EPA plus DHA (720 mg EPA+280 mg DHA) daily from the capsules. Total fat intake from the capsules was 4 g per day. None of the treatments affected inflammatory cell numbers in the bloodstream; neutrophil and monocyte phagocytosis or respiratory burst in response to E. coli; production of tumor necrosis factor-α, interleukin-1β, and interleukin-6 in response to bacterial lipopolysaccharide; or plasma concentrations of soluble intercellular adhesion molecule-1. In contrast, the ALNA and FO treatments decreased the plasma concentrations of soluble vascular cell adhesion molecule-1 (16 and 28% decrease, respectively) and soluble E-selectin (23 and 17% decrease, respectively). It is concluded that, in contrast to previous reports using higher amounts of these fatty acids, a moderate increase in consumption of long-chain n−6 or n−3 polyunsaturated fatty acids does not significantly affect inflammatory cell numbers or neutrophil and monocyte responses in humans and so would not be expected to cause immune impairment. Furthermore, we conclude that moderate levels of ALNA and FO, which could be incorporated into the diet, can decrease some markers of endothelial activation and that this mechanism of action may contribute to the reported health benefits of n−3 fatty acids.