Dietary supplementation with fish oil enhances in vivo synthesis of tumor necrosis factor

Honey Bee Pollen in Meagre (Argyrosomus regius) Juvenile Diets: Effects on Growth, Diet Digestibility, Intestinal Traits, and Biochemical Markers Related to Health and Stress

This research aimed to evaluate the effects of the inclusion of honey bee pollen (HBP) in meagre (Argyrosoumus regius) juveniles' diets on growth performance, diet digestibility, intestinal morphology, and immunohistochemistry. Furthermore, stress-related molecular markers and biochemical blood profile of fish were evaluated, together with mineral trace and toxic element concentration in pollen and diets. Specimens of meagre (360) of 3.34 ± 0.14 g initial body weight, were randomly allocated to twelve 500 L circular tanks (30 fish per tank). Four diets were formulated: a control diet and three experimental diets with 1%, 2.5%, and 4% of HBP inclusion. All the growth parameters and crude protein and ether extract digestibility coefficients were negatively linearly affected by increased HBP inclusion (p < 0.0001). Histology of medium intestine showed slight signs of alterations in group HPB1 and HPB2.5 compared to control. Fish from HBP4 group showed severe alterations at the intestinal mucosa level. Immunohistochemical detection of TNF-α in the medium intestine showed the presence of TNF-α+ cells in the lamina propria, which resulted in accordance with the increased level of the TNF-α protein detected by immunoblotting in the liver. This stress situation was confirmed by the increased hepatic level of HSP70 (p < 0.05) in fish fed the HBP4 diet and by the linear decrease of total serum protein levels in HBP-containing diets (p < 0.0001). These negative effects can be related to the ultrastructure of the bee pollen grain walls, which make the bioactive substances unavailable and can irritate the intestine of a carnivorous fish such as meagre.

Omega-3 fatty acids modulate cyclophosphamide induced markers of immunosuppression and oxidative stress in pigs

Immunosuppression directly correlates with economic benefits in livestock. Although omega-3, known as an energy source, is used as a pharmaceutical molecule, it remains unknown whether dietary supplementation with omega-3 can alleviate cyclophosphamide-induced immunosuppression in pigs. Omega-3 treatment increased the number of white blood cell, lymphocytes, and monocytes and decreased tumor necrosis factor (TNF)-α production under CTX challenge. In addition, we confirmed that omega-3 decreased the expression of nuclear factor (NF)-κB, TNF-α, interferon (IFN)-γ, and interleukin (IL)-8 in peripheral blood mononuclear cells. Additionally, omega-3 alleviated the activities of liver injury markers (alanine transaminase [ALT] and aspartate transaminase [AST]) and modulated oxidative stress markers (superoxide dismutase [SOD], malondialdehyde [MDA], and glutathione peroxidase [GPx]) in the blood serum after the CTX challenge. Based on these results, we suggest that omega-3 treatment modulates CTX-induced immunosuppression and oxidative stress in pigs. These results may have important implications in the development of new therapeutic approaches to improve immunosuppression, hepatic injury and dysfunction, and oxidative stress in pigs.

Fish oil supplementation benefits the murine host during the acute phase of a parasitic infection from Trypanosoma cruzi

Long-chain omega-3 polyunsaturated fatty acids (LC n-3 PUFA) are known to modulate a variety of immune cell functions. On occasion, this has led to diminished host resistance to certain viral and bacterial infections. Little is known about the impact of n-3 PUFA on host resistance to parasitic infection, however, based on results from a small study conducted more than two decades ago, we hypothesized that providing mice LC n-3 PUFA will diminish host resistance to Trypanosoma cruzi, the parasitic pathogen responsible for Chagas disease. To investigate this, C57BL/6 mice were supplemented by gavage (0.6% v/w) with phosphate-buffered saline, corn oil (CO), or menhaden fish oil (FO, a fat source rich in LC n-3 PUFA) for 15 days prior to T cruzi (Y strain) challenge and throughout the acute phase of infection. FO supplementation was associated with a transient 2-fold greater peak of blood parasitemia at 7 days postinfection (dpi), whereas subsequent cardiac parasitemia was ~60% lower at 12 dpi. FO treatment also ameliorated the leukopenia and thrombocytopenia observed in the early stages of a T cruzi infection. FO supplementation reduced circulating and cardiac nitric oxide at 7 and 12 dpi, respectively. FO supplementation altered ex vivo prostaglandin E₂ and cytokine and chemokine production by splenocytes isolated from uninfected and infected mice. Overall, our results suggest that oral administration of LC n-3 PUFA from FO can have beneficial effects on the host in the early course of a T cruzi infection.

Production and characterization of refined oils obtained from Indian oil sardine (Sardinella longiceps)

Crude Sardinella longiceps oil was refined in different stages such as degumming, neutralization, bleaching, and deodorization. The efficiency of these processes was evaluated on the basis of free fatty acid (FFA), peroxide (PV), p-anisidine (pAV), total oxidation (TOTOX), thiobarbituric acid reactive species (TBARS) values, Lovibond CIE-L*a*b* color analyses, and (1)H NMR or GC-MS experiments. The utilities of NMR-based proton signal characteristics as new analytical tools to understand the signature peaks and relative abundance of different fatty acids and monitoring the refining process of fish oil have been demonstrated. Phosphoric acid (1%) was found to be an effective degumming reagent to obtain oil with the lowest FFA, PV, pAV, TOTOX, and TBARS values and highest color reduction. Significant reduction in the contents of hydrocarbon functionalities as shown by the decrease in proton integral in the characteristic (1)H NMR region was demonstrated by using 1% H3PO4 during the course of the degumming process. A combination (1.25:3.75%) of activated charcoal and Fuller's earth at 3% concentration for a stirring time of 40 min was found to be effective in bleaching the sardine oil. This study demonstrated that unfavorable odor-causing components, particularly low molecular weight carbonyl compounds, could successfully be removed by the refining process. The alkane-dienals/alkanes, which cause unfavorable fishy odors, were successfully removed by distillation (100 °C) under vacuum with aqueous acetic acid solution (0.25 N) to obtain greater quality of refined sardine oil, a rich source of essential fatty acids and improved oxidative stability. The present study demonstrated that the four-stage refinement process of sardine oil resulted in a significant improvement in quality characteristics and nutritional values, particularly n-3 PUFAs, with improved fish oil characteristics for use in the pharmaceutical and functional food industries.

N-3 polyunsaturated fatty acids regulate lipid metabolism through several inflammation mediators: mechanisms and implications for obesity prevention

Obesity is a growing problem that threatens the health and welfare of a large proportion of the human population. The n-3 polyunsaturated fatty acids (PUFA) are dietary factors that have potential to facilitate reduction in body fat deposition and improve obesity-induced metabolic syndromes. The n-3 PUFA up-regulate several inflammation molecules including serum amyloid A (SAA), tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in hepatocytes and adipocytes. Actions of these inflammation mediators resemble those of n-3 PUFA in the modulation of many lipid metabolism-related genes. For instance, they both suppress expressions of perilipin, sterol regulatory element binding protein-1 (SREBP-1) and lipoprotein lipase (LPL) to induce lipolysis and reduce lipogenesis. This review will connect these direct or indirect regulating pathways between n-3 PUFA, inflammation mediators, lipid metabolism-related genes and body fat reduction. A thorough knowledge of these regulatory mechanisms will lead us to better utilization of n-3 PUFA to reduce lipid deposition in the liver and other tissues, therefore presenting an opportunity for developing new strategies to treat obesity.

Source of dietary lipid may modify the immune response in stressed feeder cattle

Five studies were conducted to evaluate the effects of lipid source on performance and health of stressed feeder cattle. A total of 332 heifers (195 +/- 2.37 kg initial BW) in trial 1 and 336 heifers (206 +/- 1.70 kg initial BW) in trial 2 were fed diets containing ground flaxseed (FLAX), rolled full-fat soybeans (SOY), or tallow (TAL) at 13, 20, or 4%, respectively (DM basis). All diets were formulated to be isonitrogenous and isocaloric. The ADG and G:F for the first 7 d and for the entire feeding period were greater (P < 0.05) for TAL and FLAX than for SOY. Percentage of animals treated and retreated for bovine respiratory disease did not differ among dietary treatments. The FLAX treatment increased (P < 0.05) total n-3 PUFA concentrations in the plasma, whereas SOY increased (P < 0.05) plasma concentrations of total n-6 PUFA. In trial 3, 18 steers were individually fed diets containing TAL and 18 steers were fed a diet containing SOY (20% of DM). In trials 4 and 5, 18 steers were individually fed diets containing TAL and 18 steers were fed diets containing FLAX (12.9% of DM). On d 14 and 17 of study 3, 4, and 5, 16 steers from each dietary treatment were injected i.v. with Escherichia coli O55:B5 lipopolysaccharide (LPS), and 2 steers from each diet were injected with saline. Rectal temperatures after LPS challenge were lower (P < 0.05) for SOY and FLAX than for TAL, and plasma TNF was greater (P < 0.05) for SOY than for TAL. Serum haptoglobin and blood fibrinogen increased and white blood cell count decreased in response to LPS, but none of these variables was affected by treatment. Although this research failed to measure an effect of lipid source on feedlot morbidity or mortality, these studies indicate that altering the source and type of dietary fatty acids may modify the immune response in stressed feeder cattle and that performance may be hindered by feeding full-fat soybeans to receiving cattle.

The effects of omega-3 polyunsaturated fatty acids on TNF-alpha and IL-10 secretion by murine peritoneal cells in vitro

Omega-3 polyunsaturated fatty acids (PUFA) affect immune response, partly by affecting cytokine secretion. Omega-3 PUFA decrease tumor necrosis factor (TNF)-alpha secretion by RAW 264.7 macrophages but increase TNF-alpha secretion by primary elicited peritoneal macrophages in vitro. In this study, the effects of omega-3 and omega-6 PUFA on lipopolysaccharide induced TNF-alpha and interleukin (IL)-10 secretion by murine primary resident and elicited peritoneal macrophages and by RAW 264.7 macrophages, were examined in vitro using an enzyme-linked immunosorbent assay. In addition, the effects of dietary omega-3 PUFA on the number of cells secreting these cytokines were examined with enzyme-linked immunospot assay. All cell types secreted more TNF-alpha but similar amounts of IL-10 when incubated with the omega-3 PUFA, eicosapentaenoic acid or docosahexaenoic acid, compared with that when incubated with the omega-6 PUFA, linoleic acid or arachidonic acid. Dietary fish oil did not affect the number of TNF-alpha secreting resident peritoneal macrophages but decreased the number of macrophages secreting IL-10 ex vivo. These results show that dietary omega-3 PUFA and omega-3 PUFA added to cells in vitro increase TNF-alpha secretion by resident peritoneal macrophages, probably by a direct effect on the cells. In contrast, omega-3 PUFA did not affect IL-10 secretion by the cells but decreased the number of cells secreting IL-10 ex vivo, possibly by affecting cell recruitment, maturation or proliferation.

Dietary fish oil increases the number of splenic macrophages secreting TNF-alpha and IL-10 but decreases the secretion of these cytokines by splenic T cells from mice

Dietary fish oil has immunomodulatory effects that are partly mediated by its effects on cytokine secretion. In this paper, we examine whether dietary fish oil has different effects on cytokine secretion by T cells and macrophages. Female BalbC mice were fed diets supplemented with 18% fish oil + 2% corn oil or 20% corn oil. Concanavalin A (ConA)- and LPS-induced TNF-alpha and IL-10 secretion by splenocytes was examined using ELISA. Dietary fish oil decreased ConA induced-, but increased LPS-induced, TNF-alpha and IL-10 secretion by total murine splenocytes. Dietary fish oil increased the number of splenocytes secreting TNF-alpha and IL-10, following stimulation with LPS, by 123 and 38%, respectively, but did not affect cytokine secretion by each cell, as determined using enzyme-linked immunospot. Spleens from mice fed the fish oil diet had over 2-fold higher proportion of macrophages with high expression of CD11b than spleens from mice fed the corn oil diet. In addition, fish oil increased the proportion of total and CD11b(+) splenocytes that expressed the LPS receptor complex molecules, CD14 and toll-like receptor (TLR)4/myeloid differentiation factor-2 (MD-2), by 85 and 28%, respectively. The increased proportion of macrophages expressing the LPS receptor complex molecules, CD14 and TLR4/MD-2, in spleens from mice fed the fish oil diet may explain the increased number of cells that secreted the cytokines after LPS stimulation.

Effects of acute or chronic omega-3 and omega-6 polyunsaturated fatty acid treatment on behavioral, neuroendocrine and cytokine changes elicited by exogenous interleukin-1beta challenge

Chronic omega-3 or omega-6 polyunsaturated fatty acid (n-3; n-6 respectively) treatment attenuated human interleukin-1beta (hIL-1beta; 5.0 microg/kg)-elicited rise of circulating ACTH levels and attenuated the sickness behavior and locomotor suppression elicited by the cytokine. Furthermore, hIL-1beta markedly elevated circulating levels of plasma IL-6, an effect attenuated by n-3, but not n-6 treatment. Such protective effects were not evident upon short-term (3 day) n-3 exposure. These results demonstrate that long-term administration of either n-3 or n-6 confers protection against several neuroendocrinological, immunological and behavioral actions of hIL-1beta challenge, although in general the effects of n-3 were more pronounced.

Different ratios of eicosapentaenoic and docosahexaenoic omega-3 fatty acids in commercial fish oils differentially alter pro-inflammatory cytokines in peritoneal macrophages from C57BL/6 female mice

The use of fish oil (FO) as a dietary supplement to prevent or reduce the severity of cardiovascular diseases and autoimmune disorders such as rheumatoid arthritis is receiving much attention. Several recent reports indicate that eating fish often or the use of small doses of FO capsules appears to have benefits against cardiovascular diseases. We have reported in the past that diets enriched with FO protect against renal diseases and prolong the life span of autoimmune-prone mice compared to corn oil (CO) diets. However, the optimum ratio of eicosapentaenoic acid (EPA) to docosahexaenoic acid (DHA) in commercially available FOs to reduce the production of various pro-inflammatory cytokines has not been well established. We, therefore, obtained deodorized FO from three sources containing different EPA/DHA contents, fed them to C57BL/6 mice for 8 weeks in a 10% (vol/wt) diet (oil A, 11/10; oil B, 14/9; oil C, 23/14) and compared them with (10%) CO-fed mice as control. TNF-alpha, IL-6 and IL-1beta were measured by enzyme-linked immunosorbent assay in thioglycollate-induced macrophages, 8 and 24 h after lipopolysaccharide treatment. The results showed a significant decrease in TNF-alpha after only 8 h in oil C. After 24 h, TNF-alpha, IL-6 and IL-1beta levels decreased only in mice fed oil C, although nonsignificant decreases were seen in mice fed oil A compared to mice fed CO. The antioxidant enzymes, catalase and glutathione transferase, were higher in kidneys of mice fed oil C compared to mice fed CO. The study suggests that anti-inflammatory activity may vary among different sources of FO due to variations in EPA/DHA content.

Eicosapentaenoic acid modulates the immune response but has no effect on a mimic of antigen-specific responses

OBJECTIVE

It has been suggested that the omega-3 polyunsaturated fatty acid eicosapentaenoic acid (EPA) has immunosuppressive effects and that these may be detrimental in some circumstances. Many studies have used high-fat diets or have concentrated on one aspect of immune function, such as mitogen-induced proliferation. In the present study we assessed the effect of high-purity EPA provided as a novel diester with propane-1,3-diol, which was delivered orally within the normal dietary fat content.

METHODS

Mitogen-induced proliferation and a mimic of antigen-specific splenocyte proliferation were examined. Proinflammatory cytokine production in response to lipopolysaccharide ex vivo was also measured. Balb/c mice were fed a fat-free diet to which was added oil to make up 5% of the final diet weight by using corn oil or 95% pure EPA as a diester with propane-1,3-diol (4%, plus 1% corn oil).

RESULTS

There was no difference in food consumption or weight gain between mice fed the control and EPA-enriched diets for 10 or 24 d. There was a significant decrease in the splenocyte proliferation index in animals fed the EPA-enriched diet after 10 and 24 d when stimulated by concanavalin A (P<0.05), but no difference when cells were stimulated with anti-CD3 and interleukin-2. There was a significant increase in the production of tumor necrosis factor by splenocytes of mice fed the EPA-enriched diet when stimulated by lipopolysaccharide (P<0.0005). However, there was no difference in ex vivo lipopolysaccharide-stimulated production of interleukin-6 between the two diets at either time point (P>0.05).

CONCLUSIONS

The present study found that, rather than producing a generalized immunosuppression, the administration of approximately 10 g of EPA/kg of body weight has more subtle effects in modulating the immune system. The observed effects of EPA may explain some of its reported beneficial effects in inflammatory conditions without producing detrimental effects on antigen-specific immunosurveillance.

Dietary fish oil increases tumor necrosis factor secretion but decreases interleukin-10 secretion by murine peritoneal macrophages

Dietary fish oil has immunomodulatory effects that are mediated in part by its effects on cytokines. Secretion of the inflammatory and the anti-inflammatory cytokines tumor necrosis factor (TNF) and interleukin (IL)-10 by murine resident peritoneal macrophages was monitored after ex vivo stimulation with lipopolysaccharide. Macrophages were obtained from mice fed a corn oil diet containing 200 g/kg corn oil or a fish oil diet containing 180 g/kg fish oil and 20 g/kg corn oil. Dietary fish oil increased secretion of the proinflammatory cytokine, TNF, but decreased secretion of the anti-inflammatory cytokine, IL-10. The cytokines appeared in the medium after 1.5 h and peaked at 6-12 h. Neutralizing antibodies against TNF and IL-10 had little effect on secretion of the other cytokine, indicating that the effects of fish oil on TNF and IL-10 secretion by these cells are independent of one another. Furthermore, although inhibiting prostaglandin production enhanced TNF secretion by macrophages from mice fed the corn oil diet, it did not affect IL-10 secretion by macrophages in this group. Blocking leukotriene B(4) production also did not affect IL-10 secretion in macrophages from mice fed a nonpurified diet. These results demonstrate that fish oil has an overall pro-inflammatory effect given its effects on secretion of both inflammatory and anti-inflammatory cytokines by resident peritoneal macrophages.

R3230AC rat mammary tumor and dietary long-chain (n-3) fatty acids change immune cell composition and function during mitogen activation

Because anticancer immunity declines progressively with tumor growth, a major focus of current research in tumor immunology is the development of means to stimulate the host immune system. This study determined the effects of dietary long-chain (n-3) fatty acids and tumor burden on immune cell phospholipid composition and membrane-mediated immune defense in rats implanted with the R3230AC mammary adenocarcinoma. Fischer 344 rats (145 +/- 2 g) were fed one of two semipurified diets (20 g/100 g fat) for 21 d before and 17 d after tumor implantation. Diets provided long-chain (n-3) fatty acids at 0 or 50 g/kg of total fat. Mammary tumor growth was 31% lower (P = 0.1) in rats fed long-chain (n-3) fatty acids. Dietary long-chain (n-3) fatty acids had beneficial effects on several host immune defenses, including activation of CD8(+) T cells and type-1 cytokine (interferon-gamma and tumor necrosis factor-alpha) production (P < 0.05). Upregulated immune function in tumor-bearing rats fed the high (n-3) diet occurred concurrently with specific changes in the major membrane phospholipids phosphatidylcholine and phosphatidylethanolamine in high (n-3)-fed rats. Because membrane composition plays a critical role in immune function, additional work is needed to determine the relationship between alterations in the phospholipid composition of immune cells during cancer and subsequent upregulation of host defense in the tumor-bearing state.

Effects of sesamin-supplemented dietary fat emulsions on the ex vivo production of lipopolysaccharide-induced prostanoids and tumor necrosis factor alpha in rats

BACKGROUND

Sesamin, a nonfat constituent of sesame oil, inhibits Delta(5)-desaturase activity, resulting in accumulation of dihomo-gamma-linolenic acid (DGLA), which displaces arachidonic acid (AA) and consequently decreases the formation of proinflammatory 2-series prostaglandins.

OBJECTIVE

We sought to determine whether dietary supplementation with sesamin augments the antiinflammatory effects of dietary linseed oil in rats.

DESIGN

We investigated the effects of continuous tube feedings of emulsions containing safflower oil or linseed oil with sesamin (SO+ and LO+) or without sesamin (SO and LO) on liver fatty acid composition and on endotoxin-induced production of prostaglandin E(2), 6-keto-prostaglandin F(1alpha), and tumor necrosis factor alpha (TNF-alpha) by whole blood from rats (n = 6 per diet group).

RESULTS

We found a significant accumulation of DGLA only in the liver phospholipids of animals fed SO+ and LO+ (1.8 +/- 0.2 and 1.4 +/- 0.3 mol%, respectively), which suggests that sesamin inhibited Delta(5)-desaturation of n-6 fatty acids. These changes were associated with significant reductions in plasma prostaglandin E(2) concentrations in animals fed SO+ compared with those fed SO (P: < 0. 05). Despite a significant reduction in tissue AA content in the LO group, the prostaglandin E(2) concentrations did not differ significantly from those of the SO group. Plasma concentrations of TNF-alpha were significantly lower (P: < 0.05) in the animals fed LO+ than in those fed SO (199 +/- 48 and 488 +/- 121 ng/L, respectively).

CONCLUSION

These data indicate that in rats, tube feedings of diets containing sesamin exerted antiinflammatory effects that were augmented by concurrent consumption of linseed oil.

Activation state alters the effect of dietary fatty acids on pro-inflammatory mediator production by murine macrophages

Studies investigating the effect of dietary fats on pro-inflammatory cytokine production by macrophages (M phis) have yielded conflicting results. We hypothesised that this may be due to the different capacities of the M phis studied commonly (resident, thioglycollate-elicited) to produce prostaglandin E(2)(PGE(2)) and leukotriene B(4)(LTB(4)) which inhibit and stimulate, respectively, tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) production. To investigate this, male C57Bl6 mice were fed for 6 weeks on a low fat (LF) diet or on high fat diets which contained coconut oil (CO), olive oil (OO), safflower oil (SO) or fish oil (FO) as the main fat source. Production of TNF-alpha, IL-1 beta, PGE(2)and LTB(4)by lipopolysaccharide-stimulated resident and thioglycollate-elicited (i.e. inflammatory) peritoneal M phis was measured. PGE(2)production by both inflammatory and resident M phis was significantly decreased by FO feeding. FO also decreased LTB(4)production by resident M phis compared with LF feeding. Production of both cytokines by inflammatory M phis decreased with increasing unsaturation of the high fat diets, such that cells from FO-fed mice showed significantly decreased production of TNF-alpha and IL-1 beta compared to those from mice fed on each of the other diets. In contrast, resident M phis from mice fed FO showed increased TNF-alpha production compared to those from CO-fed mice. Thus, FO feeding decreases production of TNF-alpha and IL-1 beta by inflammatory M phis and increases production of TNF-alpha by resident M phis, at least in comparison to some other dietary fats. These results indicate the mechanisms by which dietary fats exert their effects upon pro-inflammatory cytokine production are most likely different for resident and inflammatory M phis.

Modulatory effects of dietary lipids on immune system functions

Dietary lipid manipulation may affect a great number of immune parameters, such as lymphocyte proliferation, cytokine synthesis, natural killer (NK) cell activity, phagocytosis and so on. The immunomodulation induced by dietary fatty acids may be applied in the amelioration of inflammatory disorders, such as autoimmune diseases. However, the mechanisms that participate in these processes are still poorly understood. It is probable that modulation of immune system by fatty acids of the diet may occur by alteration of membrane fluidity, lipid peroxide formation, eicosanoid production or regulation of gene expression. However, recent studies have reported the effects of several free fatty acids on apoptosis induction of in vitro cultures. In fact, a possible explanation of the effects that fatty acids promote on the immune system cells could be associated with an apoptotic process performed in an irreversible way. In vivo studies have demonstrated the ability of fatty acids to alter the survival of animals fed diets containing oils and infected with a pathogenic bacterium. Experimental infection in animals fed dietary lipids produces a modification of resistance to micro-organisms. The present review analyses all of these parameters that dietary fatty acids are capable of altering in order to modify the immune response. Further studies will be needed to establish the mechanisms involved in immune system regulation, reduction of symptoms derived from autoimmune pathologies and so on.

Dietary fats affect macrophage-mediated cytotoxicity towards tumour cells

In the present study, the effects of feeding mice diets of different fatty acid compositions on the production of TNF-alpha and nitric oxide by lipopolysaccharide-stimulated peritoneal macrophages and on macrophage-mediated cytotoxicity towards L929 and P815 cells were investigated. C57Bl6 mice were fed on a low-fat (LF) diet or on high-fat diets (21% fat by weight), which included coconut oil (CO), olive oil (OO), safflower oil (SO) or fish oil (FO) as the principal fat source. The fatty acid composition of the macrophages was markedly influenced by that of the diet fed. Lipopolysaccharide (LPS)-stimulated macrophages from FO-fed mice showed significantly lower production (up to 80%) of PGE2 than those from mice fed on each of the other diets. There was a significant positive linear correlation between the proportion of arachidonic acid in macrophage lipids and the ability of macrophages, to produce PGE2. Lipopolysaccharide-stimulated TNF-alpha production by macrophages decreased with increasing unsaturated fatty acid content of the diet (i.e. FO < SO < OO < CO < LF). Macrophages from FO-fed mice showed significantly lower production of TNF-alpha than those from mice fed on each of the other diets. Nitrite production was highest for LPS-stimulated macrophages from mice fed on the LF diet. Macrophages from FO-fed mice showed significantly higher production of nitrite than those from mice fed on the OO and SO diets. Compared with feeding the LF diet, feeding the CO, OO or SO diets significantly decreased macrophage- mediated killing of P815 cells (killed by nitric oxide). Fish oil feeding did not alter killing of P815 cells by macrophages, compared with feeding the LF diet; killing of P815 cells was greater after FO feeding than after feeding the other high fat diets. Compared with feeding the LF diet, feeding the OO or SO diets significantly decreased macrophage-mediated killing of L929 cells (killed by TNF). Coconut oil or FO feeding did not alter killing of L929 cells by macrophages, compared with feeding the LF diet. It is concluded that the type of fat in the diet affects macrophage composition and alters the ability of macrophages to produce cytotoxic and immunoregulatory mediators and to kill target tumour cells.

Dietary lipids modify the cytokine response to bacterial lipopolysaccharide in mice

To investigate the effect of dietary lipids with different fatty acid compositions upon the in vivo cytokine response to bacterial lipopolysaccharide (LPS), mice were fed for 5 weeks on a low-fat diet or on one of four high-fat diets that contained 20%, by weight, of coconut oil (CO), olive oil (OO), safflower oil (SO) or fish oil (FO). The mice were injected intraperitoneally with a non-lethal dose of Escherichia coli LPS (100 micrograms/20 g body weight) and killed 90 or 180 min later. Plasma tumour necrosis factor-alpha (TNF-alpha), interleukin (IL)-1alpha, IL-6 and IL-10 concentrations were measured by enzyme-linked immunosorbent assay (ELISA). Plasma TNF-alpha and IL-10 concentrations were higher 90 min postinjection than after 180 min, whereas plasma IL-1beta and IL-6 concentrations were higher 180 min postinjection than after 90 min. Peak plasma TNF-alpha, IL-1beta and IL-6 concentrations were lower in the CO- and FO-fed mice than in those fed the SO diet. Peak plasma IL-10 concentrations were higher in CO-fed mice than in those fed some of the other diets. These observations suggest that, relative to the n-6 polyunsaturated fatty acid-rich SO diet, CO and FO diminish production of proinflammatory cytokines in vivo. This indicates that these fatty acids might be useful therapies in acute and chronic inflammatory diseases. The enhanced production of IL-10 following CO feeding appears to be an additional antiinflammatory effect of this oil, which could give added benefit in various clinical conditions.

Effect of intravenous omega-6 and omega-3 fat emulsions on nitrogen retention and protein kinetics in burned rats

The effect of omega-3 fat emulsion on nitrogen retention and kinetics in relation to fatty acid profile were investigated in burned rats receiving total parenteral nutrition (TPN). A fat emulsion of a structured symmetrical triacylglycerol containing only eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (2:1) was prepared. Sprague-Dawley rats were fed by fat-free chow for 2 wk. Then rats were fed exclusively with one of three types of TPN for 7 d. Animals in group C received fat-free TPN (n = 11). Group omega 6 received safflower oil fat emulsion, which accounted for 20% of total caloric intake (n = 11). Group omega 3 received fat emulsion containing only EPA and DHA (1% of total calories, n = 11), in addition to safflower oil emulsion (19% of total calories). On day 5, each rat was subjected to 20% full-thickness scald burns. Rats were sacrificed under ether anesthesia 48 h after burning. The rats in group C became deficient in omega-6 essential fatty acids. Cumulative nitrogen balance was decreased significantly in group omega 6. The rates of whole-body protein synthesis were increased significantly in both groups omega 6 and omega 3. In omega 6, however, the rates of whole-body protein breakdown were increased significantly. In conclusion, the rates of whole-body protein breakdown increased and nitrogen retention was aggravated significantly in animals administered the safflower oil emulsion. Significant increases of urinary excretion of total catecholamine were also observed. Prostaglandin E2 and thromboxane B2 concentrations were not significantly different among three groups. Supplementation with the new omega-3 fat emulsion, however, improved protein metabolism in burned rats receiving TPN.

Nutritional alterations and the effect of fish oil supplementation in dogs with heart failure

Alterations in body composition and nutritional status are common in humans with heart failure and are related, in part, to increases in cytokine concentrations. Cytokines have not been studied previously in dogs with naturally occurring cardiac disease nor has fish oil administration been used in this population to decrease cytokine production. The purposes of this study were to characterize nutritional and cytokine alterations in dogs with heart failure and to test the ability of fish oil to reduce cytokines and improve clinical outcome. Body composition, insulinlike growth factor-1, fatty acids, and cytokines were measured in 28 dogs with heart failure and in 5 healthy controls. Dogs with heart failure then were randomized to receive either fish oil or placebo for 8 weeks. All parameters were measured again at the end of the study period. At baseline, 54% of dogs with heart failure were cachectic and the severity of cachexia correlated with circulating tumor necrosis factor-alpha concentrations (P = .05). Cytokine concentrations at baseline, however, were not significantly increased in dogs with heart failure compared to controls. Baseline plasma arachidonic acid (P = .02), eicosapentaenoic acid (P = .03), and docosahexaenoic acid (P = .004) concentrations were lower in dogs with heart failure than in controls. Fish oil supplementation decreased interleukin-1 beta (IL-1) concentrations (P = .02) and improved cachexia (P = .01) compared to the placebo group. The mean caloric intake of the heart failure dogs as a group was below the maintenance energy requirement (P < .001), but no difference was found in food intake between the fish oil and placebo groups. Insulinlike growth factor-1 concentrations (P = .01) and reductions in circulating IL-1 concentrations over the study period (P = .02) correlated with survival. These data demonstrate that canine heart failure is associated with cachexia, alterations in fatty acids, and reduced caloric intake. Fish oil supplementation decreased IL-1 concentrations and improved cachexia. In addition, reductions in IL-1 predicted survival, suggesting that anticytokine strategies may benefit patients with heart failure.

Increased production of TNF-alpha and decreased levels of dienoic eicosanoids, IL-6 and IL-10 in mice fed menhaden oil and juniper oil diets in response to an intraperitoneal lethal dose of LPS

Eicosapentaenoic acid (EPA) and the non-methylene interrupted fatty acids (NMIFA) displace arachidonic acid (AA: 20:4omega6 -5,8,11,14) in the membrane phospholipids. Unlike EPA (20:5omega3 -5,8,11,14,17), the NMIFA (20:3omega6 -5,11,14 and 20:4omega3 -5,11,14,17) lacking the delta-8 double bond are not substrates for the formation of eicosanoids. For 20 days, the mice were fed diets containing 5wt% dietary fats from various sources. The magnitudes in the production of eicosanoids and cytokines produced in response to an intraperitoneal injection of endotoxin in mice fed menhaden fish oil (MO) diets enriched with EPA were compared with those maintained on juniper oil (JO) containing NMIFA or on safflower oil (SO), a major source of the AA precursor, linoleic acid. The levels of PGE2, 6-keto-PGF1alpha and TXB2 were markedly lower (P < 0.01) in animals fed either MO or JO diets compared to the controls. The plasma levels of tumor necrosis factor (TNF)-alpha were significantly higher (P < 0.05) with a concomitant decrease of interleukin (IL)-6 and of IL-10 in mice fed MO or JO diets (P < 0.01) compared to those fed SO diet. These data suggest that the effects of consuming NMIFA of JO despite their inability to form eicosanoids are similar to those of feeding EPA which forms biologically active alternate metabolites.

Dietary alpha-linolenic acid increases TNF-alpha, and decreases IL-6, IL-10 in response to LPS: effects of sesamin on the delta-5 desaturation of omega6 and omega3 fatty acids in mice

Sesamin (a non-fat portion of sesame seed oil) inhibits delta-5 desaturase activity resulting in an accumulation of dihomo-gamma-linolenic acid (DGLA) which can displace arachidonic acid (AA) and decrease the formation of pro-inflammatory mediators. We investigated the effects of consumption of diets containing 0.25wt% sesamin and 15 wt% safflower oil (SO) (providing 12% of the added fat as linoleic acid) or a 15 wt% 2:1 mixture of linseed oil and SO (LOSO) (providing 6% alpha-linolenic acid and 6% linoleic acid) for 3 weeks on the liver membrane fatty acid composition and on the production of prostaglandin (PG) E2, TNF-alpha, IL-6 and IL10 in mice. Consumption of sesamin-supplemented SO and LOSO diets resulted in a significant increase in the levels of 20:3omega6 (DGLA), suggesting that sesamin inhibited delta-5 desaturation of omega6 fatty acids. In animals fed LOSO diets, the levels of alpha-linolenic acid, eicosapentaenoic acid (EPA) and of docosahexaenoic acid (DHA) were elevated with a concomitant decrease of arachidonic acid (AA) in the liver membrane phospholipids. Further, in animals fed LOSO diets with or without sesamin, an increase in the circulating levels of TNF-alpha was associated with a concomitant decrease in PGE2. Despite a lack of differences in the levels of AA, the PGE2 levels were significantly lower in mice fed sesamin-supplemented SO compared to those fed SO alone. Thus, these data suggest that irrespective of the availability of a specific fatty acid as a substrate, through regulating the PGE2 synthesis, the production of TNF-alpha could be modulated.

Metabolic-cytokine responses to a second immunological challenge with LPS in mice with T. gondii infection

Injection of 10 cysts of Toxoplasma gondii (Me49 strain) into Swiss Webster mice results in 1) an acute phase of infection lasting for 2-3 wk, characterized by weight loss, and 2) a chronic phase in which surviving mice show either partial weight recovery (Gainers) or persistent, although stable, cachexia (Nongainers). In response to a second immunological stimulation with lipopolysaccharide (LPS) in the chronic phase of the infection, it is shown that 1) the increase in energy expenditure was more prolonged in both groups of infected mice than in controls, 2) the intensity and duration of hypophagia were also differently affected with Nongainers > Gainers > controls, and 3) the infected mice had higher serum levels of tumor necrosis factor-alpha (TNF-alpha) and interleukin (IL)-10 and a lower ratio of IL-10 to TNF-alpha than controls. In contrast, serum IL-4 increased to the same level in all three groups. Evaluation of the permeability of the blood-brain barrier by intravenous injection of Evans blue revealed a marked staining in the brain of only the infected Nongainers. Taken together, these results indicate that, in mice with chronic toxoplasmosis, a second nonspecific challenge (with LPS) exacerbates the hypophagic and hypermetabolic states, the latter being associated with hyperresponsiveness in TNF-alpha and IL-10 production. Furthermore, the greater exacerbation of the hypophagic state in mice showing persistent cachexia may be due to a preexisting higher permeability of the blood-brain barrier, which would allow a greater access of plasma-borne cytokines and/or other neuroimmunologically active substances to the central nervous system.

A randomized double-blind controlled study of 6 months of oral nutritional supplementation with arginine and omega-3 fatty acids in HIV-infected patients. Swiss HIV Cohort Study

OBJECTIVE

To evaluate the effects of an oral nutritional supplement enriched with two potentially immunostimulant compounds (arginine and omega-3 fatty acids) on the changes in food intake, body composition, immune parameters and viraemia in HIV-infected outpatients.

DESIGN

Six-month prospective randomized double-blind controlled study.

SETTING

University hospital outpatient nutrition clinic.

PATIENTS

Sixty-four HIV-infected outpatients with CD4 lymphocyte count > or = 10O x 10(6)/l.

INTERVENTION

All patients received a daily oral nutritional supplement (606 kcal supplemented with vitamins, trace elements and minerals). In addition, half of the patients were randomized to receive 7.4 g arginine plus 1.7 g omega-3 fatty acids.

MAIN OUTCOME MEASURES

Disease progression measured by AIDS-defining events, CD4 and CD8 lymphocyte counts, viraemia, tumour necrosis factor soluble receptors, nutritional status determined by anthropometric, bioelectrical impedance and dietetic assessment.

RESULTS

Fifty-five patients completed the protocol. Compliance with and tolerance of oral nutritional supplement during the 6-month period was excellent. In both groups of patients the following were found: total energy intake was transiently increased and then returned to baseline level; nitrogen/energy intake ratio was increased throughout the study; gain of body weight and fat mass were approximately 2 and 1kg, respectively, over 6 months, and were similar in both groups. In addition, CD4 and CD8 lymphocyte counts, viraemia, tumour necrosis factor soluble receptors remained statistically unchanged and were similar in both groups.

CONCLUSIONS

Enrichment of an oral nutritive supplement with arginine and omega-3 fatty acids did not improve immunological parameters. However, body weight increased in both groups.

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 fish oil and cytokine and eicosanoid production during human immunodeficiency virus infection

BACKGROUND

Dietary fish oil (FO) has been shown to modulate the immune system. The purpose of this study was to explore the effects of FO supplementation on the production of dienoic eicosanoids and cytokines in patients with human immunodeficiency virus (HIV) infection.

METHODS

This was a randomized, prospective, double-blind study that included homosexual males with HIV infection. Patients were asked to consume voluntarily five food bars daily containing FO (n = 10) or safflower oil (SO) (n = 9) for 6 weeks. At baseline and week 6, plasma was obtained to measure incorporation of omega-3 fatty acids. At baseline, week 3, and week 6, measurements were made of changes in dienoic eicosanoids and cytokines from lipopolysaccharide (LPS)-stimulated peripheral blood mononuclear cells (PBMC) or spontaneously releasing cells.

RESULTS

In the FO group but not the SO group, there was increased incorporation of the omega-3 fatty acid docosahexaenoic acid (DHA) into the phospholipids of the fatty acids of the plasma. In the FO group, there was a significant decrease (p = .01) in 6-keto prostaglandin (PG) F1 alpha released from PBMC. There was a significant increase (p = .01) in interleukin (IL)-6 released from the PBMC in the FO group between baseline and week 3 and between week 3 and week 6. At week 6, there was significantly more IL-6 (p = .01) released from the PBMC in the FO group compared with the SO group. There was no change in CD4 cell counts by analysis of variance.

CONCLUSIONS

The FO-containing food bars were well tolerated and allowed incorporation of omega-3 fatty acids to occur. Despite evidence of significant metabolic effects on eicosanoid and cytokine production, widespread clinical use of FO for HIV-infected patients is not warranted without further study, particularly given the trend toward a decline in CD4 cell numbers at this dose and with this type of fish oil.

Fish oil enhances macrophage tumor necrosis factor-alpha mRNA expression at the transcriptional level

Dietary supplementation with fish oil has previously been shown to enhance in vivo and in vitro (macrophage) synthesis of tumor necrosis factor-alpha (TNF-alpha) in response to bacterial lipopolysaccharide (LPS) stimulation. The studies reported here were conducted to gain insight into the molecular mechanisms of this nutrient-immune interaction by comparing the concentration, rate of synthesis, and rate of decay of TNF-alpha mRNA upon LPS stimulation of macrophages obtained from mice fed high-fat diets, rich in either fish oil, corn oil, or coconut oil, or a low-fat diet for a period of 4 weeks. The results indicate that compared with the other diet groups, LPS stimulation of macrophages from mice fed fish oil resulted in (1) enhanced levels of mRNA and protein for TNF-alpha, and (2) increased transcription of TNF-alpha mRNA as assessed by nuclear run-on assays. Posttranscriptional studies showed that the rate of decay of TNF-alpha mRNA did not vary significantly for macrophages from mice fed with fish oil as compared with corn oil. Further studies using actinomycin D and cycloheximide suggested that RNA synthesis, but not protein synthesis, was necessary for TNF-alpha mRNA accumulation. Taken together, the present studies suggest that fish oil enhances macrophage TNF-alpha mRNA expression at the transcriptional level. Although such TNF-alpha upregulation may provide a mechanism for the beneficial effects of fish oil in certain inflammatory and immune disorders, it can also underlie its potential deleterious effects if the degree of upregulation leads to exaggerated TNF-alpha production that exceeds the limits of benefit to reach toxic levels.

Modulation of the endogenous leukotriene production by fish oil and vitamin E

We investigated the effects of fish oil and vitamin E on the endogenous leukotriene production. 10 healthy volunteers were supplemented for 1 week with fish oil (containing 40 mg/kg body weight per day of eicosapentaenoic and docosahexaenoic acid), vitamin E (540 mg, i.e., 800 IU of D-alpha-tocopherol per day), or with both agents. Treatment resulted in a significant increase in the eicosapentaenoate concentration in red blood cell membranes and/or in the vitamin E concentration in serum. In addition, nine obese patients were investigated who were on a hypocaloric diet including 10 mg vitamin E/day for 8 weeks. This diet was associated with a significant decrease in serum vitamin E concentration. The urinary concentration of leukotriene E4 plus N-acetylleukotriene E4 served as a measure for the endogenous leukotriene production. Fish oil reduced leukotriene production in eight of the 10 healthy individuals. After vitamin E supplementation, urinary leukotrienes were significantly reduced in all of the healthy volunteers. The combination of vitamin E plus fish oil had no synergistic effect on leukotriene production in the individuals tested. The decrease in serum vitamin E concentration during the hypocaloric, 10 mg vitamin E/day diet was associated with an increase in urinary leukotrienes in 8 of the 9 obese patients. Urinary prostaglandin metabolites, determined as tetranorprostanedioic acid, increased or decreased in parallel with urinary leukotrienes in most individuals; however, changes were less pronounced than those observed with leukotrienes. We conclude that the endogenous leukotriene production can be reduced effectively by high doses of fish oil or vitamin E, whereas vitamin E depletion is associated with an increase in leukotriene generation.

Effects of continuous tube feeding of dietary fat emulsions on eicosanoid production and on fatty acid composition during an acute septic shock in rats

The effects of a short-term (5 days) continuous intragastric tube feeding of diets containing n - 6 polyunsaturated fatty acids (PUFA) from safflower oil (SO) or n - 3 PUFA from menhaden oil (MO) on the production of proinflammatory mediators, and on the number of animals surviving after an intravenous injection of lipopolysaccharide (LPS) were investigated in rats. The phospholipid fatty acid composition of cell membranes from several organs and of plasma were also analyzed. No marked differences in the number of animals surviving or in the production of tumor necrosis factor-alpha were observed between the 2 groups of animals. However, 90 min after LPS exposure the plasma levels of prostaglandin (PG) E2 and 6-keto-PGF1 alpha decreased significantly (40% and 60%, respectively) for the group of rats fed MO diet compared to those fed SO diet (P < 0.05). Following continuous infusion of liquid MO diet, the amount of arachidonic acid (AA) detected was significantly lower in plasma (23%), spleen (43%), lungs (41%), and liver (38%), but was unchanged in the heart tissues. The percent of eicosapentaenoic acid (EPA) incorporated into phospholipids of plasma, spleen, lungs, liver, and heart were 7.6, 4.4, 2.1, 7.2, and 1.1%, respectively. These data indicate that after continuous MO feeding, a significant decrease in the production of proinflammatory eicosanoids was associated with a marked reduction in AA content. Further, these data suggest that nutritional intervention may have a therapeutic potential to ameliorate clinical symptoms due to excessive productions of eicosanoids during acute septic complications.

Effect of dietary linseed oil on tumoricidal activity and eicosanoid production in murine macrophages

Diets that contain high levels of n-3 fatty acids from fish oil have been shown to significantly effect macrophage cytolytic capacity, tumor necrosis factor alpha production and eicosanoid production. The present study was undertaken to determine whether n-3 fatty acids from vegetable origin [linseed oil (LIN)] would have the same effects on murine macrophage tumoricidal capacity and eicosanoid production as would fish oil. Mice were fed for three weeks diets that contained 10% (wt/wt) of either LIN, which is high in linolenic acid (18:3n-3), menhaden fish oil (MFO), which is high in eicosapentaenoic (20:5n-3) and docosahexaenoic (22:6n-3) acids, or safflower oil (SAF), which is high in linoleic acid (18:2n-6). In vivo- or in vitro-activated macrophages were assessed for select functions. As expected, macrophages from mice fed LIN and MFO produced significantly lower levels of both prostaglandins and leukotriene C4 when compared with macrophages from mice fed SAF. In addition, LIN and MFO macrophages were able to synthesize leuko-triene C5, which could not be produced by macrophages from mice fed SAF. The effects of LIN, however, were not as pronounced as those of MFO. With respect to specific functions, macrophages from mice fed LIN did not have altered cytolytic capacity when compared with macrophages from mice fed SAF and activated in vitro with either lipopolysaccharide (LPS) alone for 24 h or with LPS plus interferon gamma (IFN gamma) for 5 h. Diet did not significantly alter tumoricidal capacity of macrophages activated completely in vivo either.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged lymphocyte proliferation following incorporation and retention of dietary omega-3 fatty acids

T cell activation involves events at the plasma membrane; therefore, molecules such as long chain omega-3 fatty acids that alter the structure of the plasma membrane may affect the activation of aged T cells. In this project we investigated whether the incorporation of omega-3 fatty acids (from fish oil), in the presence of vitamin E, improves age-diminished T cell proliferation. Young and old mice were fed diets rich in either fish (menhaden) oil or saturated fat for various lengths of time. Splenocytes were harvested from these mice and stimulated in culture with either mitogen or the antigen keyhole limpet hemocyanin (for a secondary response); proliferation was estimated by [3H]thymidine incorporation. We found no discernible effect of dietary omega-3 fatty acids (with vitamin E supplementation) on lymphocyte proliferation stimulated by the mitogens concanavalin A or phytohemagglutinin. We did, however, find that the saturated fat diet and the menhaden oil diet in young mice lowered protein kinase C activities in the particulate fractions of spleen cells when compared to chow-fed mice. Middle-aged and old mice were less affected by the experimental diets than young mice, but they demonstrated decreased protein kinase C activity as well. These alterations did not affect the ability of splenocytes to respond to mitogenic stimulation. Fatty acid analysis revealed that lymphocytes from mice fed saturated fat for 8.5 months retained significant amounts of the omega-3 fatty acid docosahexaenoic acid, despite the lack of dietary omega-3 fatty acids. However, when aged (but not young) lymphocytes were clonally expanded by antigen in vivo in the presence of dietary omega-3 fatty acids, they produced a greater secondary proliferative response than old lymphocytes expanded during a saturated fat diet. Although our results suggest that omega-3 fatty acids may enhance aged lymphocyte proliferation, the tenacious retention of these fatty acids makes comparison with omega-3-depleted lymphocytes difficult.