Dietary alpha-linolenic acid and immunocompetence in humans

Nutritional skin care: health effects of micronutrients and fatty acids

Human skin is continuously exposed to internal and external influences that may alter its condition and functioning. As a consequence, the skin may undergo alterations leading to photoaging, inflammation, immune dysfunction, imbalanced epidermal homeostasis, or other skin disorders. Modern nutritional science is developing new insights into the relation between food intake and health, and effects of food ingredients may prove to be biologically relevant for optimal skin condition. The objective of this review was to evaluate the present knowledge about the interrelation of nutrients and skin, particularly the photoprotective effects of nutrients, the influences of nutrients on cutaneous immune responses, and therapeutic actions of nutrients in skin disorders. The nutrients of focus were vitamins, carotenoids, and polyunsaturated fatty acids. Supplementation with these nutrients was shown to provide protection against ultraviolet light, although the sun-protection factor was relatively small compared with that of topical sunscreens. An increase in delayed-type hypersensitivity skin responses after supplementation with nutrients has proven beneficial, especially in elderly people, and may boost cell-mediated immunity. Dietary consumption of certain plants or fish oil is known to modulate the balance of lipid inflammatory mediators and, therefore, is valuable in the treatment of inflammatory skin disorders. It was concluded that nutritional factors exert promising actions on the skin, but information on the effects of low-to-moderate doses of nutrients consumed long term by healthy individuals is obviously lacking, as are data on direct effects on basal skin properties, including hydration, sebum production, and elasticity.

Flaxseed in Lupus Nephritis: A Two-Year Nonplacebo-Controlled Crossover Study

OBJECTIVE

The objective of this study was to determine the renoprotective effects of ground flaxseed in patients with lupus nephritis.

METHODS

Forty patients with lupus nephritis were asked to participate in a randomized crossover trial of flaxseed. Twenty-three agreed and were randomized to receive 30 grams of ground flaxseed daily or control (no placebo) for one year, followed by a twelve-week washout period and the reverse treatment for one year. At baseline and six month intervals, serum phospholipids, flaxseed sachet counts, serum creatinine, 12-hour urine albumin excretion and urine albumin to creatinine ratios, serum viscosity and plasma lipids were measured.

RESULTS

There were eight drop-outs and of the 15 remaining subjects flaxseed sachet count and serum phospholipid levels indicated only nine were adherent to the flaxseed diet. Plasma lipids and serum viscosity were unaltered by the flaxseed supplementation whereas serum creatinine in the compliant patients during flaxseed administration declined from a mean of 0.97+/-0.31 mg/dL to a mean of 0.94+/-0.30 mg/dL and rose in the control phase to a mean of 1.03+/-0.28 mg/dL [p value <0.08]. Of the fifteen patients who completed the study, similar changes were noted [p value <0.1]. The nine compliant patients had lower serum creatinines at the end of the two-year study than the 17 patients who refused to participate [p<0.05]. Microalbumin at baseline declined in both control and flaxseed time periods, but there was a trend for a greater decline during flaxseed administration [p<0.2].

CONCLUSIONS

Flaxseed appears to be renoprotective in lupus nephritis, but this interpretation is affected by under powering due to poor adherence and potential Hawthorne effects.

Dietary polyunsaturated fatty acids alter lymphocyte subset proportion and proliferation, serum immunoglobulin G concentration, and immune tissue development in chicks

The effects of fat source on immune response of the offspring of the Single Comb White Leghorn laying hens were investigated. The laying hens were fed for 6 wk with a wheat-soybean meal basal diet with added sunflower oil (SO), animal oil (AO), linseed oil (LO), or menhaden fish oil (FO) at 5% (wt/wt). Upon hatching, the chicks (30/group) were given the same types of diets for 8 wk. The dietary SO, AO, and LO provided different n-6 to n-3 polyunsaturated fatty acids (PUFA) ratios. The FO and LO had ratios of n-6 to n-3 PUFA that were close but had different components of n-3 PUFA. The results demonstrated that the chicks fed LO or FO had significantly lower (P < 0.05) splenocyte proliferative response to ConA than the chicks fed SO or AO at either 4 wk or 8 wk of age, with a stronger (P < 0.05) suppressive effect produced by LO at 4 wk. A significantly lower (P < 0.05) splenocyte response to PWM was produced by the chicks fed AO, LO, and FO compared with the chicks fed SO at 8 wk. The thymus lymphocyte proliferation in response to ConA at 4 wk was lower (P < 0.05) in the chicks fed AO, LO, and FO than in the chicks fed SO. Both LO and FO elevated (P < 0.05) the proportion of IgM+ lymphocytes in spleen, but only FO increased (P < 0.05) the serum IgG concentration. The LO elevated (P < 0.05) the percentage of CD8+ T-lymphocytes but not the ratio of CD4+ to CD8+ cells (P > 0.05) in spleen. Growths of thymus, spleen, and bursa were impacted significantly (P < 0.05) by the amount of dietary PUFA, the ratio of n-6 to n-3 fatty acids, and n-3 PUFA components.

Oxidative stress as a mechanism of diabetes in diabetic BB prone rats: effect of secoisolariciresinol diglucoside (SDG)

Secoisolariciresinol diglucoside (SDG) isolated from flaxseed has antioxidant activity and has been shown to prevent hypercholesterolemic atherosclerosis. An investigation was made of the effects of SDG on the development of diabetes in diabetic prone BioBreeding rats (BBdp rats), a model of human type I diabetes [insulin dependent diabetes mellitus (IDDM)] to determine if this type of diabetes is due to oxidative stress and if SDG can prevent the incidence of diabetes. The rats were divided into three groups: Group I, BioBreeding normal rats (BBn rats) (n = 10); group II, BBdp untreated (n = 11); and group III, BBdp treated with SDG 22 mg/kg body wt, orally) (n = 14). Oxidative stress was determined by measuring lipid peroxidation product malondialdehyde (MDA) an index of level of reactive oxygen species in blood and pancreas; and pancreatic chemiluminescence (Pancreatic-CL), a measure of antioxidant reserve. Incidence of diabetes was 72.7% in untreated and 21.4% in SDG-treated group as determined by glycosuria and hyperglycemia. SDG prevented the development of diabetes by approximately 71%. Development of diabetes was associated with an increase in serum and pancreatic MDA and a decrease in antioxidant reserve. Prevention in development of diabetes by SDG was associated with a decrease in serum and pancreatic-MDA and an increase in antioxidant reserve. These results suggest that IDDM is mediated through oxidative stress and that SDG prevents the development of diabetes.

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.

Flaxseed ameliorates interstitial nephritis in rat polycystic kidney disease

BACKGROUND

Flaxseed has demonstrated useful antiinflammatory properties in a number of animal models and human diseases. We undertook a study to determine if flaxseed would also modify clinical course and renal pathology in the Han:SPRD-cy rat.

METHODS

Male Han:SPRD-cy rats were pair fed a 10% flaxseed of control rat chow diet for eight weeks from weaning. Tissue was harvested for analysis of cystic change, apoptosis, cell proliferation, and fibrosis. Tissue was also harvested for lipid analysis using gas chromatography.

RESULTS

Animals thrived on both diets. Flaxseed-fed animals had lower serum creatinine (69 vs. 81 mumol/liter, P = 0.02), less cystic change (1.78 vs. 2.03 ml/kg, P = 0.02), less renal fibrosis (0.60 vs. 0.93 ml/kg, P = 0.0009), and less macrophage infiltration (13.8 vs. 16.7 cells/high-power video field) of the renal interstitium than controls. The groups did not differ in renal tubular epithelial cell apoptosis and proliferation. Lipid analysis revealed significant renal enrichment of 18 and 20 carbon omega 3 polyunsaturated fatty acids (total omega 6:omega 3 ratio 3.6 vs. 9.1, P < 0.0001).

CONCLUSIONS

Flaxseed ameliorates Han:SPRD-cy rat polycystic kidney disease through moderation of the associated chronic interstitial nephritis. The diet alters renal content of polyunsaturated fatty acids in a manner that may promote the formation of less inflammatory classes of renal prostanoids.

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.

Reduction of hypercholesterolemic atherosclerosis by CDC-flaxseed with very low alpha-linolenic acid

Flaxseed (Type I flaxseed) with 51-55% alpha-linolenic acid in its oil and richest source of plant lignans, has been shown to reduce hypercholesterolemic atherosclerosis by 46% without lowering serum lipids. Antiatherogenic activity was claimed to be due to its alpha-linolenic acid and/or lignan content. If alpha-linolenic acid component of flaxseed is responsible for antiatherogenic activity, then, CDC-flaxseed (Type II flaxseed) which has similar oil and lignan content but has very little (2-3% of the total oil) alpha-linolenic acid would have no antiatherogenic effect. An investigation, therefore, was made of Type II flaxseed on high cholesterol diet-induced atherosclerosis and serum lipids [total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C)] in rabbits. Rabbits were assigned to four groups: Group I, Control; Group II, Type II flaxseed diet (7.5 g/kg orally daily); Group III, 1% cholesterol diet; Group IV, 1% cholesterol diet supplemented with Type II flaxseed (7.5 g/kg orally daily). Blood samples were collected before (0 time) and after 4 and 8 weeks of experimental diets for measurement of serum lipids. Aorta was removed at the end of 8 weeks for assessment of atherosclerotic plaques. Serum TC, LDL-C, TC/HDL-C, and LDL-C/HDL-C were lower in Group IV as compared to Group III by 14 and 31%, 17 and 32%, 28 and 34% and 24 and 32%, respectively, at 4 and 8 weeks. HDL-C was not affected by Type II flaxseed in hypercholesterolemic rabbit. TG and VLDL-C were markedly increased in Group IV as compared to Group III. Type II flaxseed reduced the development of atherosclerosis by 69%. Histological changes in the atherosclerotic regions were qualitatively similar in Groups III and IV. Results indicate that reduction in hypercholesterolemic atherosclerosis by Type II flaxseed is due to a decrease in serum TC and LDL-C. In conclusion, antiatherogenic activity of Type II flaxseed is not due to alpha-linolenic acid.

N-3 polyunsaturated fatty acids and immune cell function

The amount and type of eicosanoids made can be affected by the type of fat consumed in the diet. It is now apparent that both eicosanoids and n-3 PUFAs are potent modulators of lymphocyte and M phi functions in vitro. Inclusion in the diet of high levels of certain lipids containing n-3 PUFAs markedly affects the functions of cells of the immune system subsequently tested in vitro. Cellular components of both natural and acquired immunity are affected. In vivo tests are perhaps the most appropriate approach for determining the effect of different dietary n-3 PUFAs upon immune function. Several studies indicate that diets rich in n-3 PUFAs are anti-inflammatory and immunosuppressive in vivo, although there have been relatively few studies in man. Although some of the effects of n-3 PUFAs may be brought about by modulation of the amount and types of eicosanoids made, it is clear that these fatty acids can also elicit their effects by eicosanoid-independent mechanisms (Fig. 12). Such n-3 PUFA-induced effects may be of use as a therapy for acute and chronic inflammation, for disorders which involve an inappropriately-activated immune response and for the enhancement of graft survival.

Dietary flax seed in prevention of hypercholesterolemic atherosclerosis

Oxygen free radicals (OFRs) have been implicated in the development of hypercholesterolemic atherosclerosis. Flax seed is the richest source of omega-3 fatty acid and lignans. omega-3 Fatty acid suppresses the production of interleukin-1 (IL-1), tumor necrosis factor (TNF) and leukotriene B4 (LTB4), and of OFRs by polymorphonuclear leukocytes (PMNLs) and monocytes. Lignans possess anti-platelet activating factor (PAF) activity and are antioxidant. PAF, IL-1, TNF and LTB4 are known to stimulate PMNLs to produce OFRs. Flaxseed would, therefore, reduce the levels of OFRs and hence would prevent the development of hypercholesterolemic atherosclerosis. The effects of dietary flax seed on a high cholesterol diet induced atherosclerosis, lipid profile and OFR-producing activity of PMNLs (PMNL-CL) were investigated in rabbits. The rabbits were divided into 4 groups: group I, control; group II, flax seed diet (7.5 g/kg daily, orally); group III, 1% cholesterol diet; and group IV, same as group III but received flax seed (7.5 g/kg daily, orally). Blood samples were collected before and after 4 and 8 weeks on their respective diets for biochemical measurements and aortae were removed at the end of 8 weeks for estimation of atherosclerotic changes. The high cholesterol diet increased the serum level of total cholesterol (TC) and PMNL-CL without altering the levels of serum triglycerides (TG). These changes were associated with a marked development of atherosclerosis in the aorta. Flax seed reduced the development of aortic atherosclerosis by 46% and reduced the PMNL-CL without significantly lowering the serum cholesterol. Flax seed in normocholesterolemic rabbits increased serum total cholesterol and decreased PMNL-CL without significantly affecting the serum TG. Modest dietary flax seed supplementation is effective in reducing hypercholesterolemic atherosclerosis markedly without lowering serum cholesterol. Its effectiveness against hypercholesterolemic atherosclerosis could be due to suppression of enhanced production of OFRs by PMNLs in hypercholesterolemia. Dietary flax seed supplementation could, therefore, prevent hypercholesterolemia-related heart attack and strokes.

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.

Hydroxyl radical-scavenging property of secoisolariciresinol diglucoside (SDG) isolated from flax-seed

Recently there has been a moderate resurgence in the use of flax-seed in a variety of ways including bread. The scientific basis of its use is very limited. There is some claim for beneficial effects in cancer and lupus nephritis. These claims could be due to its ability to scavenge oxygen radicals. However, its antioxidant activity is not known. Recently a method has been developed to isolate secoisolariciresinol diglucoside (SDG) from defatted flax-seed in large quantity (patent pending). We investigated the ability of SDG to scavenge .OH using high pressure liquid chromatography (HPLC) method. .OH was generated by photolysis of H2O2 (1.25-10.0 mumoles/ml) with ultraviolet light and was trapped with salicylic acid which is hydroxylated to produce .OH-adduct products 2,3-dihydroxybenzoic acid (DHBA) and 2,5-DHBA. H2O2 produced a concentration-dependent .OH as estimated by 2,3-DHBA and 2,5-DHBA. A standard curve was constructed for known concentrations of 2,3-DHBA and 2,5-DHBA against corresponding area under the peaks which then was used for measurement of 2,3-DHBA and 2,5-DHBA generated by UV irradiation of H2O2 in the presence of salicylic acid. SDG in the concentration range of 25, 50, 100, 250, 500, 750, 1000 and 2000 micrograms/ml (36.4, 72.8, 145.6, 364.0, 728.0, 1092.0, 1456.0 and 2912.0 microM respectively) produced a concentration-dependent decrease in the formation of 2,3-DHBA and 2,5-DHBA, the inhibition being 4 and 4.65% respectively with 25 micrograms/ml (36.4 microM) and 82 and 74% respectively with 2000 micrograms/ml (2912.0 microM). The decrease in .OH-adduct products was due to scavenging of .OH and not by scavenging of formed 2,3-DHBA and 2,5-DHBA. SDG prevented the lipid peroxidation of liver homogenate in a concentration-dependent manner in the concentration range from 319.3-2554.4 microM. These results suggest that SDG scavenges .OH and therefore has an antioxidant activity.

Antithromboxane activity of dietary alpha-linolenic acid: a pilot study

Two decades of research conclusively demonstrated the antithrombotic properties of the long-chain n-3 polyunsaturated fatty acids (PUFA) present in lipids from marine fishes. Most American consumers, however, given their preference for meat, will not realize the benefits of a fish-rich diet. Could alpha-linolenic acid (18:3, n-3) be similarly effective via modulation of the synthesis of vasoactive eicosanoids, i.e., thromboxane and prostacyclin? The present pilot study is a contribution toward answering this question. We determined that the urinary excretion of 11-dehydrothromboxane B2 declined by 34% from baseline level 7 weeks after the n-6/n-3 ratio of dietary PUFA was reduced from 28:1 to 1:1. The excretion of 2,3-dinor-6-oxo-prostaglandin F1 alpha was similarly affected. The dietary adjustment was brought about by substituting measured amounts of canola and flaxseed oils (3:1) for measured amounts of olive and corn oils (3:1) in an otherwise fat-free basal diet. This study demonstrates that dietary alpha-linolenic acid is an effective modulator of thromboxane and prostacyclin biosynthesis. Therefore, we can expect that the eicosanoid-mediated effects of alpha-linolenic acid are similar to those elicited by marine lipids.

Flaxseed: a potential treatment for lupus nephritis

Flaxseed is rich in alpha-linolenic acid (alpha-LA) which has anti-atherogenic properties, and lignans which are platelet activating factor (PAF)-receptor antagonists. These constituents of flaxseed, and its beneficial effects in the MRL/lpr lupus mouse prompted us to perform this dosing study in lupus nephritis patients. Nine patients were enrolled, eight of whom completed the study. After the baseline studies, patients were given 15, 30, and 45 g of flaxseed/day sequentially at four week intervals, followed by a five-week washout period. Compliance, disease activity, blood pressure, plasma lipids, rheology, PAF-induced platelet aggregation, renal function, and serum immunology were assessed. Flaxseed-sachet count and a significant increase of serum alpha-LA indicated good compliance for 15 and 30 g doses. Total and LDL cholesterol, and blood viscosity were significantly reduced with 30 g and to a lesser extent 45 g doses. PAF-induced platelet aggregation was inhibited by all doses. There was a significant decline in serum creatinine with 30 and 45 g, and a concomitant increase in creatinine clearance with increasing flaxseed dose. Proteinuria was reduced with 30 g and to a lesser extent with 45 g of flaxseed. Complement C3 was significantly elevated by all three doses. CD11b expression on neutrophils, a measure of C3bi receptors, was significantly reduced with the 30 g dose. In conclusion, 30 g flaxseed/day was well tolerated and conferred benefit in terms of renal function as well as inflammatory and atherogenic mechanisms important in the pathogenesis of lupus nephritis.

Effects of flaxseed and flax oil diets in a rat-5/6 renal ablation model

The objective of this study was to assess the effects of flaxseed and flax oil diets in the rat renal ablation model. Flaxseed is a rich source of alpha-linolenic acid, an 18:3n3 omega-3 fatty acid, which has anti-atherogenic and anti-inflammatory properties. Flaxseed, but not flax oil, is also rich in lignans, which are platelet-activating factor-receptor antagonists. Rats were subjected to 5/6 nephrectomy, fed a regular laboratory diet (RLD) for 1 week, then divided into three groups to receive either the RLD (n = 8), a 15% flaxseed diet (n = 8), or a 15% flax oil diet (n = 7). Blood pressure, proteinuria, glomerular filtration rate, and urinary prostaglandins (thromboxane B2 and 6-keto prostaglandin F1 alpha) were measured presurgery and at 1 week (before dietary allotment) and 20 weeks postnephrectomy when blood for plasma lipids and kidneys for histology and tissue-phospholipid analyses were obtained. Blood pressure increased progressively in the RLD group but not in the flax diet groups. Plasma triglycerides and cholesterol increased in all groups, but this increase was significantly attenuated by both flax diets. Proteinuria increased 1 week postsurgery and continued to increase in the RLD group but not in the flax diet groups. Glomerular filtration rate decreased progressively, but this decline in renal function was attenuated significantly by the flax diets. Both of the flax diets prevented glomerulosclerosis and mesangial expansion. Renal alpha-linolenic acid was increased by both the flax diets (flax oil > flaxseed), but eicosapentaenoic acid increased in the flax oil group only. The flaxseed group had greater renal-arachidonic acid levels than the flax oil and RLD groups. The total omega-3 fatty acids increased twofold to threefold in the flax oil group compared with the two other groups. The total saturated fatty acids were lower and the polyunsaturated fatty acids were increased in both flax diet groups. A progressive increase in urinary thromboxane B2 occurred in the RLD group but not in the flaxseed group; the level decreased in the flax oil group. The ratio of prostaglandin F1 alpha/thromboxane B2 was preserved in the flax oil group only. In conclusion, the dietary flax seed and flax oil attenuated the decline in renal function and reduced glomerular injury with favorable effects on blood pressure, plasma lipids, and urinary prostaglandins. While we have not proven any specific synergistic effects of the constituents of the flaxseed diet, the benefits of flax-derived alpha-linolenic acid with or without lignans in the rat-5/6 renal ablation model seem clear from this experiment.

Omega-3 fatty acid supplementation in clinical and experimental lupus nephritis

Nutrients rich in omega-3 fatty acids (fish oil and flaxseed) have the potential to abrogate inflammatory and atherosclerotic mechanisms known to be involved in the pathogenesis of vascular damage of systemic lupus erythematosus nephritis. Fish oil dietary supplementation decreases proteinuria and preserves renal morphology in the NZB/NZW, BXSB, and MRL/lpr mouse models of lupus nephritis and decreases mortality in the NZB/NZW and BXSB models. The anti-inflammatory and anti-atherosclerotic potential, coupled with the animal experimental data, encouraged us to carry out a dosing study of low (6 g) and higher (18 g) doses of fish oil (MaxEPA) therapy in human lupus nephritis. At the lower dose, the fish oil inhibited inflammatory mechanisms; at the higher dose, it altered both the inflammatory and atherosclerotic mechanisms. This led to a double-blind cross-over study of fish oil therapy in 26 patients with lupus nephritis followed for 2 years 10 weeks. The fish oil dietary supplementation had no significant effect on proteinuria, isotope glomerular filration rate, disease activity index, or steroid consumption. However, it did have a significant effect on lipid levels. The cross-over design suffered carryover effects (even with a 10-week wash-out period) and placebo effects of the olive oil, which created a risk of type II error. Our interest in omega-3 fatty acids led us to assess the effects of dietary supplementation with flaxseed. Not only is the flaxseed a major source of alpha-linolenic acid but it is also the richest natural source of lignan, a natural platelet-activating factor receptor antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Abrogation of MRL/lpr lupus nephritis by dietary flaxseed

A diet supplemented with flaxseed, rich in alpha-linolenic acid and plant lignans (the latter, potent platelet-activating factor receptor antagonists), was tested in a murine model of lupus nephritis. MRL/lpr female mice (n = 25) were fed 15% flaxseed diet for 14 weeks commencing at 10 weeks of age. As controls, 30 MRL/lpr mice received a standard rodent diet without flaxseed. Isotope-glomerular filtration rate (14C-inulin clearance) was measured at 9, 16, and 24 weeks of age. Proteinuria was assessed at 2-week intervals. Spleen lymphocyte proliferation, quantitated by DNA analysis, was evaluated using flow cytometry at 9, 13, 19, and 21 weeks of age. Mortality was recorded throughout the study. Glomerular filtration rate at 16 weeks was greater in flaxseed-fed mice (0.15 +/- 0.03 mL/min) compared with controls (0.06 +/- 0.04 mL/min; P = 0.01). The onset of proteinuria (Albustix, Ames Division, Miles Laboratories, Rexdale, Ontario, Canada; > or = 2+) was delayed by 4 weeks in the flax-treated mice. The percentage of flaxseed-fed mice with proteinuria was lower than the control mice up to 21 weeks of age (39% v 58%; P = 0.01). Spleen lymphocyte proliferation (percentage of cells in S-phase) at 13 weeks of age was significantly higher in the control group (22.9 +/- 5.0, P = 0.01) but not in the flaxseed group (17.2 +/- 4.9) compared with baseline (9 weeks of age) values (13.0 +/- 3.5). Mortality was lower in the flaxseed-fed mice versus the control mice (assessed by Mantel-Haenszel (log-rank) test; P < 0.05).(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)

Influence of dietary fatty acids on cytokine production and its clinical implications

Cytokines and eicosanoids are important biologic mediators with tightly regulated production. Overproduction contributes to pathogenesis of chronic and acute inflammatory, autoimmune, atherosclerotic, and neoplastic diseases. Animal and human studies have shown that production of cytokines and eicosanoids can be reduced by certain dietary fatty acids, specifically those containing long-chain (n-3) polyunsaturated fatty acids (PUFAs). This in turn results in reduction of the severity of certain autoimmune, inflammatory, and atherosclerotic diseases. Because these cytokines are also involved in control of the host defense, substantial reduction in their production could also result in the impairment of normal immune response. Increased intake of (n-3) PUFAs without adequate antioxidant protection could result in increased free radical formation and lipid peroxidation. Thus, when (n-3) PUFAs are used to reduce the pathogenesis of these diseases, its possible adverse effects should be considered and prevented.

Concentration of dietary N-6 polyunsaturated fatty acids and the human immune status

We examined the effect of the dietary concentration of total fat and n-6 polyunsaturated fatty acids (PUFA) on the immune status of seven healthy women (age 30-65 years) who lived at our metabolic suite. During the first 20 days all subjects consumed a stabilization diet that contained 5.2 energy percent (en%) PUFA and 41.1 en% fat. For the next 40 days, three subjects consumed a diet with 3.2 en% PUFA and 26.1 en% fat, while the remaining four subjects consumed a diet with 9.1 en% PUFA and 31.1 en% fat. For the next 40 days, the diets of the two groups were crossed over. Blastogenesis of peripheral blood mononuclear cells cultured with phytohemagglutinin, concanavalin A, protein A, and pokeweed, and the serum concentrations of complement fractions C3 and C4 were significantly increased upon the feeding of both low fat (26.1 or 31.1 en%) diets compared to the values when the high fat (41.1 en%) diet was fed. None of the indices tested were different when the high PUFA (9.1 en%) and low PUFA (3.1 en%) diets were compared. Our results indicate that low fat diets improve some of the indices of human immune status and that a moderate increase in the level of n-6 PUFA in an otherwise low fat diet does not suppress the human immune system.