Dietary fat affects immune response, production of antiviral factors, and immune complex disease in NZB/NZW mice

Possibilities for Dietary Fat and antioxidants as Modulators of Mammary Carcinogenesis

The problem of defining a threshold for even a single carcinogen is both old and new. If one defines “threshold” as the quantity of carcinogen or other etiologic agent just capable of producing a tumor, then at least a common ground is described. However, this “threshold level” may be modulated upwards or downwards in the organism by various environmental and internal factors. A specific case in point is the known influence of dietary fat, especially polyunsaturated fat as an enhancer of many types of tumors, i.e., it appears to be acting to lower the threshold level of carcinogen that is required to elicit a tumorigenic response. Conversely, many dietary antioxidants such as BHT, BHA, and propyl galIate have been shown to effectively raise the threshold level, or decrease the tumorigenic response to a given level of carcinogen. The possible mechanisms through which the dietary factors modify tumorigenesis will be discussed. These will include specific influences and interactions of dietary factors on 7, 12-dimethylbenz(a) anthracene-induced mammary car-cinogenesis, carcinogen uptake and retention by the target tissue, as well as influences on glandular development which may result in an alteration of the number of possible “targets” available at the time of carcinogen exposure.

Concentrated fish oil (Lovaza(R)) extends lifespan and attenuates kidney disease in lupus-prone short-lived (NZBxNZW)F1 mice

A growing number of reports indicate that anti-inflammatory actions of fish oil (FO) are beneficial against systemic lupus erythematosus (SLE). However, the majority of pre-clinical studies were performed using 5-20% FO, which is higher than the clinically relevant dose for lupus patients. The present study was performed in order to determine the effective low dose of FDA-approved concentrated FO (Lovaza®) compared to the commonly used FO-18/12 (18-Eicosapentaenoic acid [EPA]/12-Docosahexaenoic acid [DHA]). We examined the dose-dependent response of Lovaza® (1% and 4%) on an SLE mouse strain (NZBxNZW)F1 and compared the same with 1% and 4% placebo, as well as 4% FO-18/12, maintaining standard chow as the control. Results show for the first time that 1% Lovaza® extends maximal lifespan (517 d) and 4% Lovaza® significantly extends both the median (502 d) and maximal (600 d) life span of (NZBxNZW)F1 mice. In contrast, FO-18/12 extends only median lifespan (410 d) compared to standard chow diet (301 d). Additionally, 4% Lovaza® significantly decreased anti-dsDNA antibodies, reduced glomerulonephritis and attenuated lipopolysaccharide-induced pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) in splenocytes compared to placebo. 4% Lovaza® was also shown to reduce the expression of inflammatory cytokines, including IL-1β, IL-6 and TNF-α, while increasing renal anti-oxidant enzymes in comparison to placebo. Notably, NFκB activation and p65 nuclear translocation were lowered by 4% Lovaza® compared to placebo. These data indicate that 1% Lovaza® is beneficial, but 4% Lovaza® is more effective in suppressing glomerulonephritis and extending life span of SLE-prone short-lived mice, possibly via reducing inflammation signaling and modulating oxidative stress.

Distinct roles for complement in glomerulonephritis and atherosclerosis revealed in mice with a combination of lupus and hyperlipidemia

OBJECTIVE

Although the accelerating effect of systemic lupus erythematosus (SLE) on atherosclerosis is well established, the underlying mechanisms are unknown. The aim of this study was to explore the hypothesis that lupus autoimmunity modulates the effect of hypercholesterolemia in driving arterial pathologic development.

METHODS

Low-density lipoprotein receptor-deficient (Ldlr(-/-) ) mice were crossed with B6.129-Sle16 (Sle16)-congenic autoimmune mice to obtain Sle16. Ldlr(-/-) mice, which were compared with Ldlr(-/-) and Sle16 control mice. All mice were fed either a low-fat or high-fat diet. Groups of mice were compared, by strain and by diet group, for features of accelerated atherosclerosis and autoimmunity.

RESULTS

Presence of the Sle16 locus significantly increased the extent of atherosclerosis in Ldlr(-/-) mice. Circulating C3 levels were significantly reduced in Sle16.Ldlr(-/-) mice compared to Ldlr(-/-) control mice and this was paralleled by a marked reduction in arterial lesion C3 deposition despite similar levels of IgG deposition between the groups. Increased numbers of apoptotic cells in plaques were observed in the high-fat-fed Sle16.Ldlr(-/-) mice, consistent with the observed defective clearance of cellular debris. After receiving the high-fat diet, Sle16.Ldlr(-/-) mice developed glomerulonephritis and displayed enhanced glomerular C3 deposition.

CONCLUSION

These results indicate that accelerated atherosclerosis and renal inflammation in SLE are closely linked via immune complex formation and systemic complement depletion. However, whereas hyperlipidemia will enhance renal immune complex-mediated complement activation and the development of nephritis, accelerated atherosclerosis is, instead, related to complement depletion and a reduction in the uptake of apoptotic/necrotic debris. These results suggest that aggressive treatment of hyperlipidemia in patients with SLE may reduce the occurrence of lupus nephritis, as well as diminish the risk of accelerated atherosclerosis.

Intakes of vitamin B6 and dietary fiber and clinical course of systemic lupus erythematosus: a prospective study of Japanese female patients

Background

Intakes of selected vitamins and dietary fiber may influence the clinical course of systemic lupus erythematosus (SLE). Using a cohort study method, we investigated the associations of dietary intake of vitamin B6 and B12, folate, and dietary fiber with the risk of active disease and atherosclerotic vascular events in SLE.

Methods

The study included female SLE patients in the Miyagi Lupus Cohort, which was founded in 1995. Dietary nutrients at baseline were estimated by a semiquantitative food frequency questionnaire. The association of each nutrient intake with the risk of active disease was investigated in 216 patients who had inactive disease at baseline. The association with atherosclerotic vascular events was assessed in 196 women who had inactive disease and no history of atherosclerotic diseases at baseline.

Results

Forty-three cases of active disease were identified during 9966 person-months of follow-up (1995–1999). During 19 575 person-months of follow-up (1995–2005), 20 atherosclerotic vascular events were documented. The Cox proportional hazards model revealed an inverse association between vitamin B6 intake and the risk of active disease (hazard ratio for the highest as compared with the lowest tertile, 0.41; 95% confidence interval, 0.18–0.97; P for trend = 0.04). An inverse association was also found for dietary fiber intake (P for trend = 0.01). However, no significant association was observed between intakes of these nutrients and the risk of atherosclerotic vascular events.

Conclusions

Higher intake of vitamin B6 and dietary fiber may prevent the occurrence of active disease in SLE.

Effects of atherogenic diet on hepatic gene expression across mouse strains

Diets high in fat and cholesterol are associated with increased obesity and metabolic disease in mice and humans. To study the molecular basis of the metabolic response to dietary fat, 10 inbred strains of mice were fed atherogenic high-fat and control low-fat diets. Liver gene expression and whole animal phenotypes were measured and analyzed in both sexes. The effects of diet, strain, and sex on gene expression were determined irrespective of complex processes, such as feedback mechanisms, that could have mediated the genomic responses. Global gene expression analyses demonstrated that animals of the same strain and sex have similar transcriptional profiles on a low-fat diet, but strains may show considerable variability in response to high-fat diet. Functional profiling indicated that high-fat feeding induced genes in the immune response, indicating liver damage, and repressed cholesterol biosynthesis. The physiological significance of the transcriptional changes was confirmed by a correlation analysis of transcript levels with whole animal phenotypes. The results found here were used to confirm a previously identified quantitative trait locus on chromosome 17 identified in males fed a high-fat diet in two crosses, PERA x DBA/2 and PERA x I/Ln. The gene expression data and phenotype data have been made publicly available as an online tool for exploring the effects of atherogenic diet in inbred mouse strains (http://cgd-array.jax.org/DietStrainSurvey).

Fatty acids, the immune response, and autoimmunity: a question of n-6 essentiality and the balance between n-6 and n-3

The essentiality of n-6 polyunsaturated fatty acids (PUFA) is described in relation to a thymus/thymocyte accretion of arachidonic acid (20:4n-6, AA) in early development, and the high requirement of lymphoid and other cells of the immune system for AA and linoleic acid (1 8:2n-6, LA) for membrane phospholipids. Low n-6 PUFA intakes enhance whereas high intakes decrease certain immune functions. Evidence from in vitro and in vivo studies for a role of AA metabolites in immune cell development and functions shows that they can limit or regulate cellular immune reactions and can induce deviation toward a T helper (Th)2-like immune response. In contrast to the effects of the oxidative metabolites of AA, the longer-chain n-6 PUFA produced by gamma-linolenic acid (18:3n-6, GLA) feeding decreases the Th2 cytokine and immunoglobulin (Ig)G1 antibody response. The n-6 PUFA, GLA, dihomo-gamma-linolenic acid (20:3n-6, DHLA) and AA, and certain oxidative metabolites of AA can also induce T-regulatory cell activity, e.g., transforming growth factor (TGF)-beta-producing T cells; GLA feeding studies also demonstrate reduced proinflammatory interleukin (IL)-1 and tumor necrosis factor (TNF)-alpha production. Low intakes of long-chain n-3 fatty acids (fish oils) enhance certain immune functions, whereas high intakes are inhibitory on a wide range of functions, e.g., antigen presentation, adhesion molecule expression, Th1 and Th2 responses, proinflammatory cytokine and eicosanoid production, and they induce lymphocyte apoptosis. Vitamin E has a demonstrable critical role in long-chain n-3 PUFA interactions with immune functions, often reversing the effects of fish oil. The effect of dietary fatty acids on animal autoimmune disease models depends on both the autoimmune model and the amount and type of fatty acids fed. Diets low in fat, essential fatty acid deficient (EFAD), or high in long-chain n-3 PUFA from fish oils increase survival and reduce disease severity in spontaneous autoantibody-mediated disease, whereas high-fat LA-rich diets increase disease severity. In experimentally induced T cell-mediated autoimmune disease, EFAD diets or diets supplemented with long-chain n-3 PUFA augment disease, whereas n-6 PUFA prevent or reduce the severity. In contrast, in both T cell- and antibody-mediated autoimmune disease, the desaturated/elongated metabolites of LA are protective. PUFA of both the n-6 and n-3 families are clinically useful in human autoimmune-inflammatory disorders, but the precise mechanisms by which these fatty acids exert their clinical effects are not well understood. Finally, the view that all n-6 PUFA are proinflammatory requires revision, in part, and their essential regulatory and developmental role in the immune system warrants appreciation.

Dietary soy oil content and soy-derived phytoestrogen genistein increase resistance to alopecia areata onset in C3H/HeJ mice

Alopecia areata (AA) is a complex, multi-factorial disease where genes and the environment may affect susceptibility and severity. Diet is an environmental factor with the potential to influence disease susceptibility. We considered dietary soy (soya) oil content and the soy-derived phytoestrogen genistein as potential modifying agents for C3H/HeJ mouse AA. Normal haired C3H/HeJ mice were grafted with skin from spontaneous AA affected mice, a method previously shown to induce AA. Grafted mice were given one of three diets containing 1%, 5% or 20% soy oil and observed for AA development. In a separate study, mice on a 1% soy oil diet were injected with 1 mg of genistein three times per week for 10 weeks or received the vehicle as a control. Of mice on 1%, 5%, and 20% soy oil diets, 43 of 50 mice (86%), 11 of 28 mice (39%), and 2 of 11 mice (18%) developed AA, respectively. Four of 10 mice injected with genistein and 9 of 10 controls developed AA. Mice with AA had hair follicle inflammation consistent with observations for spontaneous mouse AA, but no significant association was observed between the extent of hair loss and diet or genistein injection. Mice that failed to develop AA typically experience white hair regrowth from their skin grafts associated with a moderate macrophage and dendritic cell infiltration. Soy oil and derivatives have previously been reported to modify inflammatory conditions. Hypothetically, soy oil compounds may act on C3H/HeJ mice through modulating estrogen-dependent mechanisms and/or inflammatory activity to modify AA susceptibility.

Relationship between the fatty acid composition of rat lymphocytes and immune functions

The effects of dietary lipids on the fatty acid composition, activation and proliferation of lymphocytes were investigated. Weanling male Wistar rats were fed for 8 weeks on one of two low-fat diets which contained 50 g lipid/kg, or one of two high-fat diets containing 200 g lipid/kg, from either coconut oil or soyabean oil. The fatty acid composition of phospholipids from splenocyte membranes was affected by dietary lipid manipulation, and these differences influenced lymphocyte functions. Increased levels of linoleic acid in spleen lymphocytes correlated negatively with interleukin-2 receptor alpha-chain expression determined either by measuring the mean fluorescence or by the proportion of cells staining positive for CD25, and with the cell proliferation index. However, we found a positive correlation between interleukin-2 receptor alpha-chain expression determined by measuring the mean fluorescence and the cell proliferation index with the oleic acid concentration of spleen lymphocytes. Since phospholipid hydrolysis occurs early in lymphocyte activation, immunosuppressive effects induced by polyunsaturated fatty acids, described in the literature, could be due to an increase of linoleic acid or a decrease of oleic acid affecting many components of plasma-membrane-associated events involved in lymphocyte activation.

In vivo effects of olive oil-based lipid emulsion on lymphocyte activation in rats

Numerous studies suggest that immune function may be compromised by lipid emulsions rich in polyunsaturated fatty acids, especially linoleic acid. In our study, we compared the effect of a new olive oil-based lipid emulsion (ClinOleic(R)) containing 18% linoleic acid, and an emulsion based on soybean oil (Ivelip(R); 52% linoleic acid) on lymphocyte functions. Weaning Wistar rats (n= 24) were fed for 4 weeks on an oral diet that contained 12% of total energy as lipids from soybean oil. Then they received, during 6 days, a total parenteral nutrition (260 kcal/kg/d) in which 12% of total energy was brought by one of the two lipid emulsions. The fatty acid profile of spleen lymphocyte phospholipids reflected lipid intakes, with a higher content of oleic acid in ClinOleic(R) group and linoleic acid in Ivelip(R) group. A greater proportion of cells expressed the interleukin-2 receptor a-chain (CD25) after administration of ClinOleic(R) when compared to Ivelip(R) (55.43 +/- 3.47 vs 45.48 +/- 3.26%, P<< 0.05). Moreover, the CD25 expression was positively correlated with oleic acid content of spleen lymphocyte phospholipids (r= 0.500, P<< 0.018). These results show that ClinOleic(R) is able to induce, in vivo, a greater proportion of cells expressing CD25, and suggest that oleic acid could have a role in the observed effects.

Effect of age, breed and dietary omega-6 (n-6): omega-3 (n-3) fatty acid ratio on immune function, eicosanoid production, and lipid peroxidation in young and aged dogs

The focus of this study was to examine the influence of age and diet on various parameters of immune function in young and old Fox Terriers and Labrador Retrievers. Eighteen young and old dogs were utilized for this study. Young and old dogs were fed a basal diet containing an (n-6):(n-3) ratio of 25:1 for sixty days (Phase I). Half of the dogs were then switched to a diet with an (n-6):(n-3) ratio of 5:1, and all were maintained on their respective diets for an additional sixty days (Phase II). Results from these studies revealed an age-associated decline in several immune parameters measured. Both these breeds demonstrated a reduction in sheep red blood cell titers, as well as in their ability to respond to different mitogens. Interestingly, this decline was greater in Fox Terriers, suggesting a decrease in cellular proliferative capacity in lymphocytes isolated from the larger breed. Neither cytokine production or DTH response was affected by age. Diet and breed interactions resulted in a significant increase in T- and B-cell mitogen responsiveness. In contrast, supplementation with n-3 fatty acids did not affect IL-1, IL-6 or TNF-alpha production. Supplementation with n-3 fatty acids resulted in increased PGE3 production from peritoneal macrophages but had no effect on PGE2 production from peripheral blood mononuclear cells or peritoneal macrophages. The n-3 fatty acid supplementation did not influence alpha-tocopherol status although older dogs had significantly lower serum alpha-tocopherol concentrations. Oxidative status of these dogs was assessed by serum levels of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE). Feeding an n-3-enriched diet did not affect 4-HNE levels but significantly decreased MDA levels in old dogs. In summary, this study indicates that feeding a diet containing an (n-6):(n-3) fatty acid ratio of 5:1 had a positive, rather than a negative, effect on the immune response of young or geriatric dogs.

Dose-dependent effects of dietary gamma-linolenic acid on rat spleen lymphocyte functions

Feeding rodents a diet rich in evening primrose oil (EPO), which contains 5-10 g gamma-linolenic acid (GLA)/100 g total fatty acids, has been shown to decrease lymphocyte proliferation and natural killer cell activity. However, EPO contains a very high level of linoleic acid which itself can affect lymphocyte functions and it is not clear to what extent the effects of EPO can be attributed to GLA. The current study investigated the effect of two levels of GLA in the rat diet upon immune cell functions; the level of linoleic acid was maintained below 30 g/100 g total fatty acids. Weanling rats were fed on high fat (178 g/kg) diets which contained 4.4 g or 10 g GLA/100 g total fatty acids in place of a proportion of linoleic acid. The total polyunsaturated fatty acid content and the n-6 to n-3 polyunsaturated fatty acid ratio of the diet were maintained at 35 g/100 g total fatty acids and 7, respectively. The fatty acid compositions of the serum and of spleen leukocytes were markedly influenced by that of the diet, with an increase in the proportions of GLA and dihomo-gamma-linolenic acid when the diets containing GLA were fed; these diets also increased the proportion of arachidonic acid in spleen leukocytes. Spleen lymphocyte proliferation in response to concanavalin A was significantly reduced (by 60%) by feeding the diet containing the higher level of GLA, but not by the diet containing the lower level of GLA. Spleen natural killer cell activity and prostaglandin E (PGE) production by spleen leukocytes were not significantly affected by inclusion of GLA in the diet, although there was a tendency towards decreased natural killer cell activity by cells from rats fed the high GLA diet. Thus, this study shows that dietary GLA is capable of altering the fatty acid composition of cells of the immune system and of exerting some immunomodulatory effects, but that the level of GLA in the diet must exceed 4.4 g/100 g total fatty acids for these effects to become apparent.

Dietary n-6 and n-3 fatty acids in immunity and autoimmune disease

Clearly there is much evidence to show that under well-controlled laboratory and dietary conditions fatty acid intake can have profound effects on animal models of autoimmune disease. Studies in human autoimmune disease have been less dramatic; however, human trials have been subject to uncontrolled dietary and genetic backgrounds, infection and other environmental influences, and basic trial designs have been inadequate. The impact of dietary fatty acids on animal autoimmune disease models appears to depend on the animal model and the type and amount of fatty acids fed. Diets low in fat, essential fatty acid-deficient, or high in n-3 fatty acids from fish oils increase the survival and reduce disease severity in spontaneous autoantibody-mediated disease, whilst linoleic acid-rich diets appear to increase disease severity. In experimentally-induced T-cell-mediated autoimmune disease, essential fatty acid-deficient diets or diets supplemented with n-3 fatty acids appear to augment disease, whereas n-6 fatty acids prevent or reduce the severity. In contrast, in both T-cell and antibody-mediated auto-immune disease the desaturated and elongated metabolites of linoleic acid are protective. Suppression of autoantibody and T lymphocyte proliferation, apoptosis of autoreactive lymphocytes, and reduced pro-inflammatory cytokine production by high-dose fish oils are all likely mechanisms by which n-3 fatty acids ameliorate autoimmune disease. However, these could be undesirable long-term effects of high-dose fish oil which may compromise host immunity. The protective mechanism(s) of n-6 fatty acids in T-cell- mediated autoimmune disease are less clear, but may include dihomo-gamma-linolenic acid- and arachidonic acid-sensitive immunoregulatory circuits such as Th1 responses, TGF beta 1-mediated effects and Th3-like responses. It is often claimed that n-6 fatty acids promote autoimmune and inflammatory disease based on results obtained with linoleic acid only. It should be appreciated that linoleic acid does not reflect the functions of dihomo-gamma-linolenic and arachidonic acid, and that the endogenous rate of conversion of linoleic to arachidonic acid is slow (Hassam et al. 1975, 1977; Phylactos et al. 1994; Harbige et al. 1995). In addition to effects of dietary fatty acids on immunoregulation, inflammation as a consequence of immune activation in autoimmune disease may also be an important mechanism of action whereby dietary fatty acids modulate disease activity. In conclusion, regulation of gene expression, signal transduction pathways, production of eicosanoids and cytokines, and the action of antioxidant enzymes are all mechanisms by which dietary n-6 and n-3 fatty acids may exert effects on the immune system and autoimmune disease. Probably the most significant of these mechanisms in relation to our current understanding of immunoregulation and inflammation would appear to be via fatty acid effects on cytokines. The amount, type and balance of dietary fatty acids and associated antioxidant nutrients appear to impact on the immune system to produce immune-deviation or immunosuppressive effects, and to reduce immune-mediated inflammation which will in turn affect the susceptibility to, or severity of, autoimmune disease.

Dietary polyunsaturated fatty acids decrease anti-dsDNA and anti-cardiolipin antibodies production in idiotype induced mouse model of systemic lupus erythematosus

OBJECTIVE

To examine the effect of diets with different polyunsaturated fatty acid contents, including linseed oil which contains 70% omega-3 fatty acids, on autoantibody production in idiotype induced mouse model of systemic lupus erythematosus (SLE).

METHODS

Five different fats were fed to mice with induced SLE and antibody titers to anti-DNA and anti-cardiolipin were determined and histological examination of kidneys were carried out.

RESULTS

SLE mice fed linseed oil showed lower titers of antibodies to DNA and to cardiolipin and less severe kidney damage than mice fed other diets, including fish oil.

CONCLUSION

Use of linseed oil may attenuate the severity of SLE and this diet may be recommended for other auto-immune diseases as well.

Reducing cell membrane n-6 fatty acids attenuate mucosal damage in food-sensitive enteropathy in mice

Mucosal damage is commonly observed in food-sensitive enteropathy in infants, and the generation of leukotrienes is involved in the pathogenesis of this enteropathy. Because supplementing n-3 fatty acids is known to modify the production of leukotrienes, we investigated whether a change of dietary fatty acid composition affects leukotriene synthesis and food hypersensitivity reactions in the intestine by using a mouse model of food-sensitive enteropathy. The model was prepared by feeding ovalbumin to BALB/c mice after intraperitoneal injection of cyclophosphamide. Diets were prepared from soybean oil (control), perilla oil, lard, corn oil, and 0.125 volume of corn oil (low fat diet) and given to mice for 4 wk. Villous heights, crypt depths, leukotriene B4 and C4 production in the intestine were measured. Crypt hyperplasia and villous atrophy were severer in the corn oil-fed group than those of control group, whereas mucosal damage in the perilla oil and low fat diet groups was minimal. In the corn oil-fed group, red blood cell membrane levels of n-3 fatty acids were lower than the control, and the synthesis of leukotrienes was highest among all groups. In the perilla oil and low fat diet groups, n-6 fatty acids were lower than those of control group and leukotriene production was significantly suppressed. These results indicate that reducing cell membrane levels of n-6 fatty acids by feeding less n-6 fatty acids or supplementing n-3 fatty acids, is important to suppress leukotriene biosynthesis for prevention from mucosal damage in food-sensitive enteropathy.

Dietary fat affects lipids and anti-cardiolipin antibody levels in autoimmune-prone NZB/W F1 mice

Studies in autoimmune-prone NZB/W F1 mice have demonstrated that the amount of dietary fat can affect autoantibody production and the disease course of autoimmune diseases. Anti-cardiolipin antibodies have been found to play a major role in thrombus formation and the increase of abortion rate in both human lupus patients and murine lupus. The present study investigated further the effect of dietary fat on lipid and anti-cardiolipin antibody production in autoimmune-prone mice. Two groups of NZB/W F1 mice were fed on diets containing 200 g dietary fat/kg and 50 g dietary fat/kg respectively, the fat being composed of equal amounts of lard and soyabean oil. Serum levels of lipids, immunoglobulin (Ig) anti-single stranded DNA and anti-cardiolipin antibodies were followed regularly every month and mice were killed for in vitro experiments after 5 months on the experimental diets. The results showed that serum triacylglycerol concentration was lower in mice fed on the high-fat diet than in those fed on 50 g fat/kg. There was no significant difference in hepatic lipid contents; however, the fatty acid contents were different between these two groups. Hepatic linoleic acid (18:2n-6) and arachidonic acid (20:4n-6) concentrations were higher in mice fed on the high-fat diet. There were no significant differences in serum IgM concentrations or IgM anti-cardiolipin antibody levels between these two groups. However, IgG anti-cardiolipin antibody levels were higher in mice fed on the high-fat diet at the age of 3-4 months. Total serum IgG concentration was noted to be higher, but in contrast, serum IgA was lower, in the high-dietary-fat group. These findings suggest that high dietary fat may affect lipid metabolism and autoantibody levels in autoimmune diseases.

Nutrition and immunity with emphasis on infection and autoimmune disease

Nutrition and nutritional status can have profound effects on immune functions, resistance to infection and autoimmunity in man and other animals. Nutrients enhance or depress immune function depending on the nutrient and level of its intake. Protein-energy malnutrition and vitamin A deficiency are strongly associated with impaired immunity and infectious disease. The essential role vitamin A plays in infection and maintenance of mucosal surfaces has long been known. Recent evidence shows that T-cell subpopulations, cytokines and antibody subclasses are all affected by vitamin A. In animal studies supplementation with vitamin E protects against infection and is linked to stimulatory effects on the immune system. In man vitamin E and other anti-oxidants increase the number of CD4+ cells. Dietary lipids and zinc have a substantial impact on autoimmunity from protective to potentiation of immuno-pathological processes in animals. There is considerable potential to modify human autoimmune disease by manipulation of lipid nutrition. Deficiency of pyridoxine induces atrophy of lymphoid organs, marked reduction in lymphocyte numbers, impairs antibody responses and IL-2 production. Dietary copper is important in the prevention of infection in some animal species and T-cell function is defective under deficiency states due to an inability to produce IL-2. Selenium has been linked to viral infection, enhanced T-cell functions and TNF beta induced increase in natural killer cell activity. Understanding the molecular and cellular immunological mechanisms involved in nutrient-immune interactions will increase our applications for nutrition of the immune system in health and in disease

The effect of dietary lipid manipulation on rat lymphocyte subsets and proliferation

Polyunsaturated fatty acids (PUFA) have been shown to suppress immune cell functions in vitro. Dietary studies investigating the effects of PUFA-containing oils on lymphocyte functions have yielded contradictory findings: such studies are difficult to compare as there are many variations in protocols. The present study investigated the effects of diets containing oils rich in saturated fatty acids, monounsaturated fatty acids, n-6 PUFA or n-3 PUFA on rat lymphocyte proliferation and on receptor and surface marker expression. Rats were fed for 10 weeks on a low-fat (LF) diet (approximately 2% fat by weight) or on one of five high-fat diets, which contained 20% (by weight) hydrogenated coconut oil (HCO), olive oil (OO), safflower oil (SO), evening primrose oil (EPO) or menhaden (fish) oil (MO). Compared with feeding the LF diet, all of the high-fat diets suppressed the proliferation of lymphocytes from the spleen: although there was no significant effect of diet on the proliferation of lymphocytes from the thymus, there was a trend towards decreased proliferation with high-fat feeding. Feeding the OO, EPO or MO diets significantly suppressed proliferation of mesenteric lymph node lymphocytes compared with feeding the LF, HCO or SO diets. Dietary lipid manipulation had no effect on the proportion of T cells, B cells or monocytes/macrophages in the spleen, thymus or lymph nodes. Dietary lipid manipulation also had no significant effect on the proportions of CD4+ or CD8+ lymphocytes in spleen, thymus or lymph nodes, either in freshly prepared cells or in cells cultured in the presence of mitogen. There were no significant effects of dietary lipid manipulation on the expression of IL-2 receptors or transferrin receptors by concanavalin A (Con A)-stimulated lymphocytes. However, there was a trend towards a decrease in transferrin receptor expression by Con A-stimulated lymphocytes from the thymus and lymph nodes of the MO-fed rats and towards a decrease in the expression of IL-2 receptors by lymphocytes from the spleens and thymi of the MO-fed rats. These observations provide evidence that some dietary oils, particularly OO, EPO and MO, possess immunosuppressive properties and so may be useful in the therapy of diseases involving inappropriate lymphocyte activation.

Effect of low dietary lipid on the development of Sjögren's syndrome and haematological abnormalities in (NZB x NZW)F1 mice

A diet low in fat was found to retard the development of autoimmune disease in (NZB x NZW)F1 mice, whereas diets high in fat content were associated with more severe disease. The ability of a reduced lipid intake to ameliorate the progression of autoimmune disease was indicated by preserved lacrimal gland secretion (measured by a modified Schirmer test), decreased infiltration of inflammatory cells into the exocrine tissue, and decreased severity of immunohaemolytic anaemia as indicated by near-normal packed cell volume and reticulocyte values. These results suggest that nutritional intervention may be of some help in reducing the severity of pathological abnormalities associated with human systemic lupus erythematosus and Sjögren's syndrome.

The type of dietary fat affects the severity of autoimmune disease in NZB/NZW mice

The type of dietary fat dramatically affects the onset of autoimmune disease in lupus-prone female New Zealand Black/New Zealand White F1 (B/W) mice. Disease development was strikingly slowed in mice fed a diet containing quantities of omega-3 fatty acids (fish oil, FO). By 10 months of age, 94% of the FO mice were still living, whereas all the mice fed a saturated fat diet (lard,L) were dead. Those mice fed a corn oil (CO) diet were intermediate with 35% alive at the 10-month time evaluation. Long after the L and CO groups had succumbed to glomerulonephritis, the FO group had negligible proteinuria. Both B and T cell function, particularly antibody production and resultant circulating immune complex (CIC) levels, were modified by the type of dietary fat. FO mice exhibited lower levels of anti-ds-DNA and lower levels of CICs than L or CO mice. B/W antibody response to a T-independent antigen (DNP-dextran) was enhanced at 8 months of age in FO mice, whereas it was suppressed in L mice. T-dependent (sheep red blood cell) responses at that time period were reduced in all the diet groups, a reflection of the reduced numbers of accessory T cells as determined by FACS analysis. The natural killer (NK) response to YAC-1 cells decreased in the L group from 5 to 9 months of age but remained unchanged in the CO and FO groups. Severe glomerulonephritis was the most common histopathologic finding in the L and CO groups. Arteritis was found in the spleens of nearly all the L and CO mice. Arteritis of the heart, colon and intestine, stomach, kidney, and liver were also seen principally in the L mice. In contrast, most FO mice had minimal to mild glomerulonephritis and no or minimal arteritis in the spleen. It is likely omega-3 fatty acids of fish oil reduce immune-complex-induced glomerulonephritis through production of prostaglandin metabolites with attenuated activity and/or through altering cell membrane structure and fluidity, which may, in turn, affect the responsiveness of immune cells.

Dietary fatty acid effects on T-cell-mediated immunity in mice infected with mycoplasma pulmonis or given carcinogens by injection

To test whether or not diets enriched in w-6 polyunsaturated fatty acids are significantly immunosuppressive, B10.D2, DBA/2, and C3B6F1 mice were fed diets enriched for fatty acids: linoleic (POLY), oleic (MONO), palmitic (SAT), or eicosapentanoic (FISH). The B10.D2 and DBA/2 mice were given injected methylcholanthrene several weeks later, and immune studies were performed several months after carcinogen treatment. In conventional quarters, DBA/2 fed the POLY diet survived poorly, and many were infected with Mycoplasma pulmonis, even if given the vehicle, tractinoin, only. B10.D2 mice survived well unless on the POLY diet and given methylcholanthrene. Nevertheless, only mice on the POLY diet were significantly immunosuppressed, and only T-cell-mediated cutaneous sensitivity reactions were affected. Antibody, natural killer cell, and natural cytotoxic cell responses were not influenced by the diets. The C3B6F1 mice were assessed for immune functions prior to carcinogen (ethylnitrosourea) instillation into the trachea, and no immunosuppression was detected. After instillation, mice on the POLY and MONO diets were suppressed for T-cell cutaneous responses. Deliberate infection with Mycoplasma pulmonis resulted in suppressed cutaneous T-cell responses in the POLY group of C3B6F1 mice, and aspirin partially reversed the immunosuppression. Mice on the FISH diet were resistant to immunosuppression. It is tentatively concluded that diets rich in w-6 polyunsaturated diets, while not directly immunosuppressive, do predispose animals to suppression of certain T-cell-mediated immune responses. This immunosuppression can be "triggered" by infection and/or by exposure to carcinogens.

Dietary fat influences the expression of autoimmune disease in MRL/lpr/lpr mice

Near-isocaloric diets with qualitative and quantitative differences in fat content have a profound influence on the manifestation and progression of the autoimmune syndrome that occurs in female MRL/lpr mice. In these animals, a high (9%) lipid intake resulted in a significantly higher mortality rate: 60% (saturated fat) and 75% (unsaturated fat) compared to 35% at 1 year for a group fed a diet low in fat. Furthermore, beginning at 7 months of age mice from both of the high fat diet groups exhibited a significantly higher incidence of proteinuria than mice in the low fat group. Immunologically, the group fed the high unsaturated fat diet had the highest incidence of anti-dsDNA autoantibodies, and the high saturated fat group had the poorest macrophage phagocytic function. The low fat diet preserved near 'normal' immune function in general, particularly IL-2 production. No significant differences were noted in either the production of rheumatoid factor or natural killer cell activity, irrespective of age or diet.

Dietary fat and neoplasia--the role of net energy in enhancement of carcinogenesis: effects of fat and calories on the immune system

The mechanism by which carcinogenesis is enhanced by dietary fat is not understood. We know that a minimum level of essential fatty acids (EFA) is necessary for mammary tumor development and that this level probably exceeds the normal requirements of rats. Once the minimum level of EFA has been supplied, the calorie contribution of dietary fat may account for its enhancement of carcinogenesis. In this regard, we must recognize that the efficiency with which dietary energy is utilized is known to increase as the fat content of the diet is raised. Hence even when fed isocalorically to low fat diets, high fat diets will provide more net energy. Modulation of host immunity has been proposed as a mechanism of action of both fat and calorie intake on neoplasia. We review the literature examining the effects of fat and calories on the cell-mediated immune system, that arm of the immune system most directly responsible for the killing of neoplastic cells.

Effects of specific nutrients on the immune response. Selected clinical applications

The importance of diet in multiple aspects of the immune response is inescapable. Although only a few trials have attempted to apply knowledge derived from in-vitro and animal data to humans, the ability to modulate or "reset" the immune response by manipulating dietary intake will surely continue to be studied in the future. The role of various nutrients in immunity is reviewed and clinical applications are noted.

Effects of nutrition on disease and life span. I. Immune responses, cardiovascular pathology, and life span in MRL mice

Mice of the autoimmune, lymphoproliferative strain MRL/lpr and the congenic, nonlymphoproliferative strain MRL/n were fed one of six diets from weaning on-ward. These mice were sacrificed at 3 or 5 months of age. Low fat diets resulted in lower cholesterol and higher triglyceride levels than did cholesterol-containing high-fat diets. Caloric restriction of MRL/lpr mice was associated with an increased plaque-forming cell response to trinitrophenylated polyacrylamide beads, less lymphoproliferation, and less severe glomerulonephritis. Diet did not affect the incidence of autoimmune vasculitis in MRL/lpr mice sacrificed at 5 months. MRL/lpr mice fed a low-fat, calorically restricted diet from 5 months of age to death lived longer than mice which were fed ad libitum a cholesterol-containing, high-fat diet. At death, MRL/lpr mice fed the former diet had the autoimmune vasculitis which had been evident in mice killed at 5 months, whereas mice fed the latter diet, in addition to the vasculitis, had a high incidence of atherosclerotic lesions of intrarenal and aortic branch arteries.

Enriched lipid diet accelerates lupus nephritis in NZB x W mice. Synergistic action of immune complexes and lipid in glomerular injury

The effect of a lipid-rich diet was investigated in autoimmune NZB x W mice with immune complex lupus nephritis. Mice on an enriched lipid diet died sooner than controls. This increase in dietary fat elevated serum cholesterol levels and was associated with an accelerated loss of renal function. Ultrastructural examination of glomeruli revealed lipid in the peripheral loops and mesangium adjacent to immune deposits. Increased lipid accumulation was confirmed by histochemical staining and biochemical extraction. Accelerated disease was not related to changes in immune parameters. Thus, a high lipid consumption accelerated lupus nephritis by a local vascular effect and not by a systemic influence on the immune response. Therefore, in our system, a combined immunologic and lipid glomerular capillary insult caused a more rapidly progressive renal disease than immune complex injury alone.

Chronic experimental allergic encephalomyelitis produced by bovine proteolipid apoprotein: immunological studies in rabbits

A chronic experimental allergic encephalomyelitis (EAE) has been produced in rabbits sensitized with bovine white matter proteolipid apoprotein. Eleven of 12 animals developed clinical disease one to six months after immunization with a single dose of the apoprotein. The clinical course was characterized by posterior ataxia, flaccid paralysis progressing to spastic paralysis, and incontinence. Spontaneous relapses and remissions were observed in 3 rabbits. Histologically, acute and chronic encephalomyelitis accompanied by primary demyelination were observed. Serum antibody production, assayed by both an enzyme-linked immunosorbent assay and an electroblot procedure, did not correlate with either the clinical course or the histopathological findings. Delayed hypersensitivity to proteolipid apoprotein was observed in all rabbits prior to the onset of clinical signs. The data suggest that lymphocytes specifically sensitized to the proteolipid may be involved in the pathogenesis of the demyelination in chronic EAE.