Similar effects of c9,t11-CLA and t10,c12-CLA on immune cell functions in mice

The Ethanol Extract of Holotrichia diomphalia Larvae, Containing Fatty acids and Amino acids, Exerts Anti-Asthmatic Effects through Inhibition of the GATA-3/Th2 Signaling Pathway in Asthmatic Mice

Holotrichia diomphalia larvae (HD), a natural product from an insect resource, possesses many pharmacological properties, including anticoagulant, antitumor, anti-inflammatory, and analgesic activity. The major bioactive ingredients include oleic acid, palmitic acid, palmitoleic acid, linoleic acid, proline, and glutamic acid. Although HD is associated with immunoregulatory activities in allergic diseases, the therapeutic mechanisms of the action of HD in allergic diseases have not been investigated. The aim of this study was to evaluate the anti-asthmatic potential of HD in an ovalbumin (OVA)-induced mouse model of allergic asthma. Moreover, the anti-inflammatory potential of HD was examined to identify a plausible mechanism of action of HD in vitro. HD strongly reduced goblet cell hyperplasia, eosinophil infiltration, and reactive oxygen species (ROS), which reduced airway hyperresponsiveness (AHR), inflammation, and the expression of Th2 cytokines (IL-5 and IL-13) in bronchoalveolar lavage fluid (BALF). The expression of IL-5, IL-4, eotaxin-2, lysyl oxidase-like 2 (loxl2), and GATA-binding protein 3 (GATA-3) was attenuated in the lungs. In an in vitro assay, HD exerted immunomodulatory effects through the suppression of Th2 cytokines (IL-5, IL-13), IL-17, and tumor necrosis factor (TNF)-α production through downregulation of GATA-3 expression in EL-4 T cells. These findings suggest that the anti-asthmatic activity of HD may occur through the suppression of Th2 cytokines and total Immunoglobulin E (IgE) production by inhibition of the GATA-3 transcription pathway. Our results suggest that HD may be a potential alternative therapy, or a novel therapeutic traditional medicine, for the treatment of allergic asthma.

Gut microbiota and mTOR signaling: Insight on a new pathophysiological interaction

The gut microbiota plays a substantial role in regulating the host metabolic and immune functions. Dysbiosis, resulting from disruption of gut microbiota, predisposes many morbid pathologies like obesity and its associated comorbidities, diabetes and inflammatory conditions including some types of cancer. There are numerous proposed signaling pathways through which alterations in gut microbiota and its metabolites can disturb the host's normal physiological functions. Interestingly, many of these processes happen to be controlled by the mammalian target of rapamycin (mTOR). The mTOR pathway responds to environmental changes and regulates accordingly many intracellular processes such as transcription, translation, cell growth, cytoskeletal organization and autophagy. In this review, we aim to highlight the cross-talk between the gut microbiota and the mTOR pathway and discuss how this emerging field of research gives a beautiful insight into how the mentioned cross-talk impacts the body's homeostasis thus leading to undesirable complications including obesity, diabetes, colon and pancreatic cancer, immune system malfunctioning and ageing. Although there are a limited number of studies investigating the crosstalk between the gut microbiota and the mTOR pathway, the results obtained so far are enough to elucidate the key role of the mTOR signaling in microbiota-associated metabolic and immune regulations.

Effects of dietary conjugated linoleic acids on cellular immune response of piglets after cyclosporin A injection

The present study investigated the effects of dietary conjugated linoleic acid (CLA) on the cellular immune response of piglets after cyclosporin A (CsA) treatment. The experimental study had a 2×2 factorial design, and the main factors consisted of diets (0% or 2% CLA) and immunosuppression treatments (CsA or saline injection). CsA injection significantly increased feed : gain (F : G) of piglets (P<0.05); however, dietary CLA significantly decreased F : G of piglets (P<0.05). Dietary CLA partly ameliorated the deterioration of the feed conversion rate caused by CsA treatment (P<0.01). CsA treatment significantly decreased the percentages of CD4+ and CD8+ T lymphocytes in the thymus (P<0.01). Dietary CLA increased the percentages of CD4+ CD8+ double-positive and CD8+ single-positive T lymphocytes in the thymus (P<0.05), and had the trend to inhibit the decrease of CD4+ T lymphocytes in the thymus after CsA injection (P=0.07). CsA treatment significantly depleted the peripheral blood CD3+, CD4+ and CD8+ T lymphocytes (P<0.01). Dietary CLA significantly increased the number of peripheral blood CD8+ T lymphocytes and interleukin-2 (IL-2) production (P<0.05), and inhibited the decreases of peripheral blood CD3+, CD4+ and CD8+ T lymphocytes counts (P<0.01) as well as IL-2 production (P<0.05) after CsA treatment. Dietary CLA partly rescued the decrease of lymphocyte proliferation after CsA injection (P<0.05). In summary, dietary CLA effectively ameliorated CsA-induced cellular immunosuppression in piglets.

The Immunomodulatory Activity of Jacaric Acid, a Conjugated Linolenic Acid Isomer, on Murine Peritoneal Macrophages

This study aims at demonstrating the immunomodulatory property of jacaric acid, a conjugated linolenic acid (CLNA) isomer that is present in jacaranda seed oil, on murine peritoneal macrophages. Our results showed that jacaric acid exhibited no significant cytotoxicity on the thioglycollate-elicited murine peritoneal macrophages as revealed by the neutral red uptake assay, but markedly increased their cytostatic activity on the T-cell lymphoma MBL-2 cells as measured by the fluorometric CyQuant® NF Cell Proliferation Assay Kit. Flow cytometric analysis indicated that jacaric acid could enhance the endocytic activity of macrophages and elevated their intracellular production of superoxide anion. Moreover, jacaric acid-treated macrophages showed an increase in the production of nitric oxide which was accompanied by an increase in the expression level of inducible nitric oxide synthase protein. In addition, the secretion of several pro-inflammatory cytokines, including interferon-γ, interleukin-1β and tumor necrosis factor-α, was up-regulated. Collectively, our results indicated that the naturally-occurring CLNA isomer, jacaric acid, could exhibit immunomodulating activity on the murine peritoneal macrophages in vitro, suggesting that this CLNA isomer may act as an immunopotentiator which can be exploited for the treatment of some immunological disorders with minimal toxicity and fewer side effects.

Modulation of inflammation and immunity by dietary conjugated linoleic acid

Conjugated linoleic acid (CLA) is a mixture of positional and geometric isomers of linoleic acid. This family of polyunsaturated fatty acids has drawn significant attention in the last three decades for its variety of biologically beneficial properties and health effects. CLA has been shown to exert various potent protective functions such as anti-inflammatory, anticarcinogenic, antiadipogenic, antidiabetic and antihypertensive properties in animal models of disease. Therefore, CLA represents a nutritional avenue to prevent lifestyle diseases or metabolic syndrome. Initially, the overall effects of CLA were thought to be the result of interactions between its two major isomers: cis-9, trans-11 and trans-10, cis-12. However, later evidence suggests that such physiological effects of CLA might be different between the isomers: t-10, c-12-CLA is thought to be anticarcinogenic, antiobesity and antidiabetic, whereas c-9, t-11-CLA is mainly anti-inflammatory. Although preclinical data support a benefit of CLA supplementation, human clinical findings have yet to show definitive evidence of a positive effect. The purpose of this review is to comprehensively summarize the mechanisms of action and anti-inflammatory properties of dietary CLA supplementation and evaluate the potential uses of CLA in human health and disease.

Dietary conjugated linoleic acid and its effect on immune response in pigs infected with the porcine reproductive and respiratory syndrome virus

The aim of this study was to evaluate the effects of dietary conjugated linoleic acid (CLA) on immune response in pigs infected with porcine reproductive and respiratory syndrome virus (PRRSV). A total of 18 pigs 4 weeks of age were allocated to 3 treatments, 6 per treatment: 0% CLA, 1% CLA, and 2% CLA. Serum IL-1β, IL-6 and TNF-α; lymphocyte proliferation; and IL-2, IFN-γ, IL-10, IL-4 and IL-12 in PBMCs were evaluated. NF-κB, COX2, iNOS and PPAR-γ mRNA were also evaluated. No differences were observed among treatment groups in most of the in vivo cytokine profiles; only TNF-α production was increased in infected pigs in the CLA-supplemented groups. The cytokine profile in vitro was not affected by CLA supplementation. CLA decreased the proliferation of PBMCs stimulated with PRRSVs. Inflammation mediators and PPAR-γ were not affected by CLA in infected pigs. CLA did not improve the immune response of PRRSV infected pigs.

Effect of conjugated linoleic acid on proliferation and cytokine expression of bovine peripheral blood mononuclear cells and splenocytes ex vivo

Twenty-five primiparous Holstein cows were divided into five experimental groups (five animals per group) by different feeding (control fat preparation [CON] or conjugated linoleic acid [CLA] supplement) and slaughtering times. The daily consumption of CLA was 6.0 g of the trans-10, cis-12 CLA-isomer and 5.7 g cis-9, trans-11 CLA isomer. An initial group (IG) was slaughtered one day post partum (pp) and the remaining 20 animals after 42 and 105 days pp, respectively. Blood for peripheral blood mononuclear cells (PBMC) separation was taken seven days ante partum and immediately before slaughter. The spleen was removed during dissection for isolation of splenocytes and samples for histopathological examination. Cell viability and Concanavalin A-stimulated proliferation was analysed by MTT and Alamar Blue assay. Basal expression of cytokines (interleukin [IL]-4, IL-10, IL-12, tumour necrosis factor alpha [TNF-alpha] and interferon gamma [IFN-gamma]) was measured by quantitative real time polymerase chain reaction (qRT-PCR) in unstimulated PMBC and splenocytes. With PBMC, stimulation indices increased from 1 day pp to 105 days pp with no differences between CLA and CON groups. With splenocytes, the stimulation index of the CLA group was lower compared to CON group 105 days pp. Baseline expression of cytokines was not effected by CLA feeding comparing similar time points. Also, no differences occurred in the expression of IL-4 in PBMC and IL-10 as well as TNF-alpha in both cell populations, when comparing the feeding groups separately with IG. IL-4 was more frequently expressed in CLA group 42 days pp in splenocytes. IFN-gamma expression was increased 105 days pp in CLA group in splenocytes and PBMC. IL-12 was higher expressed 105 days (PBMC) or 42 days pp (splenocytes) when compared to IG. There was no effect of CLA feeding or slaughter time on histopathology of the spleen. In conclusion, the present results demonstrate an inhibiting effect of CLA on the mitogen-induced activation of splenocytes.

Catalytic production of conjugated fatty acids and oils

The reactive double bonds in conjugated vegetable oils are of high interest in industry. Traditionally, conjugated vegetable oils are added to paints, varnishes, and inks to improve their drying properties, while recently there is an increased interest in their use in the production of bioplastics. Besides the industrial applications, also food manufactures are interested in conjugated vegetable oils due to their various positive health effects. While the isomer type is less important for their industrial purposes, the beneficial health effects are mainly associated with the c9,t11, t10,c12 and t9,t11 CLA isomers. The production of CLA-enriched oils as additives in functional foods thus requires a high CLA isomer selectivity. Currently, CLAs are produced by conjugation of oils high in linoleic acid, for example soybean and safflower oil, using homogeneous bases. Although high CLA productivities and very high isomer selectivities are obtained, this process faces many ecological drawbacks. Moreover, CLA-enriched oils can not be produced directly with the homogeneous bases. Literature reports describe many catalytic processes to conjugate linoleic acid, linoleic acid methyl ester, and vegetable oils rich in linoleic acid: biocatalysts, for example enzymes and cells; metal catalysts, for example homogeneous metal complexes and heterogeneous catalysts; and photocatalysts. This Review discusses state-of-the-art catalytic processes in comparison with some new catalytic production routes. For each category of catalytic process, the CLA productivities and the CLA isomer selectivity are compared. Heterogeneous catalysis seems the most attractive approach for CLA production due to its easy recovery process, provided that the competing hydrogenation reaction is limited and the CLA production rate competes with the current homogeneous base catalysis. The most important criteria to obtain high CLA productivity and isomer selectivity are (1) absence of a hydrogen donor, (2) absence of catalyst acidity, (3) high metal dispersion, and (4) highly accessible pore architecture.

Conjugated linoleic acid (CLA): is it time to supplement asthma therapy?

The limitations and side effects of existing asthma therapies prompt interest in complementary and alternative therapies. Conjugated linoleic acids (CLA) are a family of natural fatty acids found primarily in beef and dairy products. These molecules have a variety of biological properties which suggest potential benefit in asthma, including effects on energy regulation, lipid metabolism, inflammation and immune function. Here we review the evidence for these effects from pre-clinical and clinical studies, their significance in the context of human asthma, and discuss the potential role for CLA supplementation in asthma management.

Trans-10, cis-12-conjugated linoleic acid modulates NF-κB activation and TNF-α production in porcine peripheral blood mononuclear cells via a PPARγ-dependent pathway

The activation of PPARγ by ligands, including conjugated linoleic acid (CLA) isomers, plays an important role in the immune response. Among CLA isomers, trans-10, cis-12 (t10c12)-CLA is known to participate in the modulation of pro-inflammatory cytokine secretion. The aim of the present study was to assess the effect of t10c12-CLA on PPARγ activation, NF-κB activation and TNF-α expression in lipopolysaccharide (LPS)-naive and LPS-stimulated porcine peripheral blood mononuclear cells (PBMC). In addition, the effect of PPARγ inhibition on NF-κB activation and TNF-α expression in porcine PBMC was examined. t10c12-CLA was found to increase TNF-α expression and NF-κB activity in LPS-naive porcine PBMC. In contrast, t10c12-CLA decreased TNF-α expression and NF-κB activity in LPS-stimulated porcine PBMC. t10c12-CLA up-regulated PPARγ activity and mRNA expression in both LPS-naive and LPS-stimulated porcine PBMC. GW9662, a PPARγ antagonist, completely negated the modulating effects of t10c12-CLA on TNF-α expression and NF-κB activity in both LPS-naive and LPS-stimulated porcine PBMC. These results suggest that t10c12-CLA can modulate TNF-α production and NF-κB activation by a PPARγ-dependent pathway in porcine PBMC.

Effects of conjugated linoleic acid on myogenic and inflammatory responses in a human primary muscle and tumor coculture model

The antiproliferative and anti-inflammatory properties of conjugated linoleic acid (CLA) make it a potentially novel treatment in chronic inflammatory muscle wasting disease, particularly cancer cachexia. Human primary muscle cells were grown in coculture with MIA PaCa-2 pancreatic tumor cells and exposed to varying concentrations of c9,t11 and t10,c12 CLA. Expression of myogenic (Myf5, MyoD, myogenin, and myostatin) and inflammatory genes (CCL-2, COX-2, IL-8, and TNF-alpha) were measured by real-time PCR. The t10,c12 CLA isomer, but not the c9,t11 isomer, significantly decreased MIA PaCa-2 proliferation by between 15% and 19%. There was a marked decrease in muscle MyoD and myogenin expression (78% and 62%, respectively), but no change in either Myf5 or myostatin, in myotubes grown in coculture with MIA PaCa-2 cells. CLA had limited influence on these responses. A similar pattern of myogenic gene expression changes was observed in myotubes treated with TNF-alpha alone. Several-fold significant increases in CCL-2, COX-2, IL-8, and TNF-alpha expression in myotubes were observed with MIA PaCa-2 coculture. The c9,t11 CLA isomer significantly decreased basal expression of TNF-alpha in myotubes and could ameliorate its tumor-induced rise. The study provides insight into the anti-inflammatory and antiproliferative actions of CLA and its application as a therapeutic agent in inflammatory disease states.

Effect of CLA isomers and their mixture on aging C57Bl/6J mice

BACKGROUND

Dietary supplements containing conjugated linoleic acid (CLA) are widely promoted for weight loss management over the counter. Recently, FDA approved the CLA as Generally Recognized as Safe category so that it can be used in various food and beverages. The combined effect of CLA isomers have been studied extensively in animals and humans, however, the role of individual isomers remains unraveled.

AIM

The present investigation addresses the effects of CLA isomers on body composition and body weight as well as safety using female C57Bl/6J aging mice.

METHODS

Two main CLA isomers and their mixture were fed to 12-months-old female C57Bl/6J mice. Ten percent corn oil (CO) based fat diet supplemented with 0.5% purified cis 9 trans 11 (c9,t11) CLA or trans 10 cis 12 (t10,c12) CLA or their mixture (CLA mix, 50:50) for 6 months. The lean mass, fat mass, glucose, non-esterified fatty acids, and insulin were examined at the end of study.

RESULTS

As a result of 6 months dietary intervention, both t10,c12 CLA and CLA mix groups showed increased lean mass and reduced fat mass compared to that of c9,t11 CLA and CO group. However, insulin resistance and liver hypertrophy were observed in t10,c12 CLA and CLA mix groups based on the results of homeostasis model assessment, revised quantitative insulin-sensitivity check index (R-QUICKI), intravenous glucose tolerance test, and liver histology. Liver histology revealed that increased liver weight was due to hypertrophy.

CONCLUSION

In conclusion, the major CLA isomers have a distinct effect on fat mass, glucose, and insulin metabolism. The t10,c12 isomer was found to reduce the fat mass and to increase the lean mass but significantly contributed to increase insulin resistance and liver hypertrophy, whereas c9,t11 isomer prevented the insulin resistance. Between the two major CLA isomers, the t10,c12 was attributed to reduce fat mass whereas, c9,t11 improves the insulin sensitivity.

Higher immunoglobulin production in conjugated linoleic acid-supplemented rats during gestation and suckling

Conjugated linoleic acid (CLA) has been reported to exert beneficial physiological effects on body composition and the immune system. However, little information is available on the influence of CLA on immune function during early life periods. The present study evaluates the effect of feeding an 80:20 mixture of cis-9, trans-11- and trans-10, cis-12-CLA isomers during gestation and suckling on the systemic immune response of weaned Wistar rats. Pups received dietary CLA from dams through the placental barrier and during suckling by breast milk (group A) or by oral administration (group B). Pups from group C only received CLA during suckling by oral administration. Group D constituted the reference group. Milk from dams fed the CLA diet had a high content of CLA and higher IgA and IgG concentrations than rats fed the standard diet. The plasma of pups from groups A, B and C showed six, twelve and nine times higher content of the cis-9, trans-11-CLA isomer than that of the group D pups. Rats from group A exhibited higher serum IgG concentrations than rats from the rest of the groups (22.14 (SEM 2.14) v. about 5 mg/ml; P < 0.05), whereas rats from groups A and B showed approximately 2-fold higher splenocyte IgM production than rats from groups C and D. However, CLA supplementation did not influence significantly the splenocyte proliferative response or cytokine secretion. Supplementation during gestation and suckling with an 80:20 cis-9, trans-11-trans-10, cis-12 CLA mix enhances the production of the main in vivo and in vitro Ig isotypes in Wistar rats.

Effect of an oil byproduct from conjugated linoleic acid (CLA) purification on CLA accumulation and lipogenic gene expression in broilers

A previous study showed that supplementing broilers with an oil byproduct obtained during the purification process of conjugated linoleic acid (CLA) from safflower oil could result in CLA-enriched egg yolks more efficiently than feeding purified CLA (free fatty acid form). On this basis, this study evaluated whether dietary CLA byproduct (CBP) supplementation would enhance CLA accumulation in broiler muscle and its lipogenic mRNA expression in the liver. A total of 456 1-day-old male broiler chicks were randomly assigned to four groups, each of which was given one of the following 2% dietary supplements for 4 weeks: soybean oil (control), safflower oil (SAF), purified CLA, and CBP. During the feeding trial, little alteration in broiler performance was observed among the test groups. CLA accumulation efficiency in the breast muscle did not differ significantly between the CLA- and CBP-fed groups after feeding of the test diet for 3 weeks. CLA supplementation also induced lipogenesis in the livers of the broilers, and it significantly increased the relative mRNA levels of sterol regulatory element binding protein 1 (SREBP1), as well as its target genes: fatty acid synthase (FAS) and acetyl coenzyme A carboxylase (ACC) (p < 0.05). However, in the CBP-fed group, SREBP1 and ACC mRNA levels were not significantly different from the controls (p > 0.05). These results suggest that CBP could be an efficient dietary source that promotes CLA accumulation in broiler muscle without inducing lipogenesis in the liver or compromising performance and meat quality in the birds.

Long-term feeding of the cis-9,trans-11 isomer of conjugated linoleic acid reinforces the specific immune response in rats

Several effects on the immune system have been ascribed to the cis9,trans11 conjugated linoleic acid (CLA) isomer. We studied whether feeding a diet enriched with an 80:20 CLA isomer mix of cis9,trans11 and trans10,cis12 CLA from gestation to adulthood affects the capacity of adult rats to achieve a specific immune response. Pregnant Wistar rats were fed a 1% CLA diet or a control diet beginning on d 7 of gestation. Weaned pups received the same diet as dams until they were 15 wk old. Rats from both groups were immunized with ovalbumin (OVA) when they were 9 wk old. Dietary CLA enhanced splenocyte OVA-specific proliferation by approximately 50% (P < 0.05) and decreased the mitogen-induced proliferative responses of these cells by approximately 10-20% (P < 0.05). The diminished splenocyte proliferative response was accompanied by a lower interleukin-2 secretion (P < 0.05). Long-term CLA supplementation did not increase serum, spleen, or mesenteric lymph node production of OVA-specific antibodies (Ab) or the number of spleen anti-OVA Ab-secreting cells. Interestingly, dietary CLA increased intestinal anti-OVA IgA production by approximately 75% (P < 0.05). In conclusion, a 1% CLA diet administered from gestation to adulthood enhanced specific systemic cell-mediated immunity as well as the mucosal IgA immune response, whereas it downregulated the polyclonal activation of the immune system. These data support the long-term effects of dietary cis9,trans11 CLA isomer on the immune system.

Isomer specificity of conjugated linoleic acid (CLA): 9E,11E-CLA

Conjugated linoleic acids (CLA) were identified in 1980's, since then it has been intensively studied due to its various beneficial health effects such as anti-inflammatory, anti-atherogenic, anti-carcinogenic and anti-diabetic/obesity effects. Isomer specificity of a number of CLA isomers, especially predominant isomer 9Z,11E- and 10E,12Z-CLA, is now recognized. However, the less prevalent CLA isomers have not been well characterized. Recently, studies have reported the distinctively different effects of 9E,11E-CLA in colon cancer cells, endothelial cells, and macrophage cells compared to the rest of CLA isomers. In this review, various effects of CLAs, especially anti-inflammatory and anti-atherogenic effects, will be discussed with focusing on the isomer-specific effects and potential mechanism of action of CLA. At last, recent studies about 9E,11E-CLA in in vitro and animal models will be discussed.

Isomer-specific effects of conjugated linoleic acid on gene expression in RAW 264.7

Conjugated linoleic acid (CLA) is a mixture of dietary fatty acids that has various beneficial effects including decreasing cancer, atherosclerosis, diabetes and inflammation in animal models. Some controversy exists on the specific isomers of CLA that are responsible for the benefits observed. This study was conducted to examine how different CLA isomers regulate gene expression in RAW 264.7. A mouse macrophage cell line, RAW 264.7, was treated with five different CLA isomers (9E,11E-, 9Z,11E-, 9Z,11Z-, 10E,12Z- and 11Z,13E-CLA). Gene expression microarrays were performed, and several significantly regulated genes of interest were verified by a real-time polymerase chain reaction (PCR). Examination of the biological functions of various significantly regulated genes by the five CLA isomers showed distinct properties. Isomers 9E,11E-, 9Z,11Z-, 10E,12Z- and 11Z,13E-CLA decreased production of proinflammatory cytokines such as interleukin (IL)-1alpha, IL-1beta and IL-6. Many of CLA's effects are believed to be mediated by the fatty acid receptors such as the peroxisome proliferator-activated receptors (PPAR) and retinoid-X-receptors (RXR). Using PPAR and RXR specific antagonists and coactivator recruitment assays, it was evident that multiple mechanisms were responsible for gene regulation by CLA isomers. Coactivator recruitment by CLA isomers showed their distinct properties as selective receptor modulators for PPARgamma and RXRalpha. These studies demonstrate distinct isomer differences in gene expression by CLA and will have important ramifications for determining the potential therapeutic benefit of these dietary fatty acids in prevention of inflammation-related diseases.

Flaxseed oil prevents trans-10, cis-12-conjugated linoleic acid-induced insulin resistance in mice

Insulin resistance (IR) and non-alcoholic fatty liver disease (NAFLD) are found in 35 and 30 % of US adults, respectively. Trans-10, cis-12-conjugated linoleic acid (CLA) has been found to cause both these disorders in several animal models. We hypothesised that IR and NAFLD caused by CLA result from n-3 fatty acid deficiency. Pathogen-free C57BL/6N female mice (aged 8 weeks; n 10) were fed either a control diet or diets containing trans-10, cis-12-CLA (0.5 %) or CLA+flaxseed oil (FSO) (0.5 %+0.5 %) for 8 weeks. Weights of livers, concentration of circulating insulin, values of homeostatic model 1 (HOMA1) for IR and HOMA1 for beta cell function were higher by 160, 636, 985 and 968 % in the CLA group compared with those in the control group. FSO decreased fasting glucose by 20 % and liver weights by 37 % compared with those in the CLA group; it maintained circulating insulin, HOMA1-IR and HOMA1 for beta cell function at levels found in the control group. CLA supplementation decreased n-6 and n-3 wt% concentrations of liver lipids by 57 and 73 % and increased the n-6:n-3 ratio by 58 % compared with corresponding values in the control group. FSO increased n-6 and n-3 PUFA in liver lipids by 33 and 342 % and decreased the n-6:n-3 ratio by 70 % compared with corresponding values in the CLA group. The present results suggest that some adverse effects of CLA may be due to n-3 PUFA deficiency and that these can be corrected by a concomitant increase in the intake of alpha-linolenic acid, 18 : 3n-3.

Immunological and metabolic effects of cis-9, trans-11-conjugated linoleic acid in subjects with birch pollen allergy

Animal studies suggest that conjugated linoleic acid (CLA) may modulate the immune response, while studies in healthy human subjects have shown little effect and results are controversial. However, the effects of CLA may be more prominent in situations of immune imbalance, such as allergy. We studied the effects of the natural CLA isomer, cis-9, trans-11-CLA, on allergy symptoms and immunological parameters in subjects with birch pollen allergy. In a randomised, placebo-controlled study, forty subjects (20-46 years) with diagnosed birch pollen allergy received 2 g CLA/d in capsules, which contained 65.3 % cis-9, trans-11-CLA and 8.5 % trans-10, cis-12-CLA (n 20), or placebo (high-oleic acid sunflower-seed oil) (n 20) for 12 weeks. The supplementation began 8 weeks before the birch pollen season and continued throughout the season. Allergy symptoms and use of medication were recorded daily. Lymphocyte subsets, cytokine production, immunoglobulins, C-reactive protein, lipid and glucose metabolism and lipid peroxidation were assessed before and after supplementation. The CLA group reported a better overall feeling of wellbeing (P < 0.05) and less sneezing (P < 0.05) during the pollen season. CLA supplementation decreased the in vitro production of TNF-alpha (P < 0.01), interferon-gamma (P < 0.05) and IL-5 (P < 0.05). Total plasma IgE and birch-specific IgE concentrations did not differ between groups, whereas plasma IgA (P < 0.05), granulocyte macrophage colony-stimulating factor (P < 0.05) and eosinophil-derived neurotoxin (P < 0.05) concentrations were lower after CLA supplementation. Urinary excretion of 8-iso-PGF2alpha, a major F2-isoprostane (P < 0.01), and 15-keto-dihydro-PGF2alpha, a primary PGF2alpha metabolite (P < 0.05), increased in the CLA group. The results suggest that cis-9, trans-11-CLA has modest anti-inflammatory effects in allergic subjects.

Dietary fish oil n-3 fatty acids increase regulatory cytokine production and exert anti-inflammatory effects in two murine models of inflammation

The higher incidence of inflammatory diseases in Western countries might be related, in part, to a high consumption of saturated fatty acids and n-6 polyunsaturated fatty acids (PUFA) and an insufficient intake of n-3 fatty acids. The purpose of this study was to examine the effects of dietary n-3 fatty acids on innate and specific immune response and their anti-inflammatory action in models of contact and atopic dermatitis. Balb/C mice were fed for 3 wk either n-6 or n-3 PUFA-fortified diets. After inducing a contact or an atopic dermatitis, immunological parameters were analyzed to evaluate the anti-inflammatory potential of these n-3 PUFA. n-3 PUFA reduced innate and specific immune responses through inhibition of TH1 and TH2 responses, increase of immunomodulatory cytokines such as IL-10, and regulation of gene expression. The inhibition of both kinds of responses was confirmed by the anti-inflammatory effect observed in contact and atopic dermatitis. Reduction in weight, edema, thickness, leukocyte infiltration, and enhancement of antioxidant defenses in the inflamed ears of mice from both models along with the prevention of delayed-type hypersensitivity induced in atopic dermatitis proved n-3 PUFA efficacy. Our data suggest that dietary fish oil-derived n-3 fatty acids have immunomodulatory effects and could be useful in inflammatory disorders.

Upregulation of tumor necrosis factor-alpha expression by trans10-cis12 conjugated linoleic acid enhances phagocytosis of RAW macrophages via a peroxisome proliferator-activated receptor gamma-dependent pathway

The aim of this study was to examine whether tumor necrosis factor (TNF)-alpha expression in the phagocytic activity of RAW macrophages by trans10-cis12 (10t-12c) conjugated linoleic acid (CLA) is associated with peroxisome proliferator-activated receptor gamma (PPARgamma) activation. 10t-12c CLA induced the TNF-alpha expression in RAW macrophages. Phagocytic activity of naive RAW macrophages was increased either by recombinant mouse (rm) TNF-alpha or by culture supernatant from 10t-12c CLA-treated RAW macrophages. This phagocytic activity was inhibited by addition of anti-rmTNF-alpha polyclonal antibody (pAb). 10t-12c CLA also increased the level of PPARgamma protein and mRNA in RAW macrophages. When naive RAW macrophages were incubated with the culture supernatant from RAW macrophages treated with 10t-12c CLA plus GW 9662, a PPARgamma antagonist, their phagocytic activity was significantly inhibited. In addition, GW 9662 antagonized the effect of 10t-12c CLA in stimulating TNF-alpha expression. These results suggest that 10t-12c CLA modulates the phagocytic activity of RAW macrophages by upregulating TNF-alpha expression via a PPARgamma-dependent pathway.

The effects of conjugated linoleic acid on human health-related outcomes

Conjugated linoleic acid (CLA) is a collective term for a mixture of positional and geometric isomers of conjugated dienoic derivatives of linoleic acid. CLA has received considerable attention as a result of animal experiments that report anti-carcinogenic, anti-atherogenic and anti-diabetic properties, and modulation of body composition and immune function. Several studies of CLA supplementation in human subjects have now been published, but in contrast to animal studies there has been marked variation between reports on the health-related outcomes. The consensus from seventeen published studies in human subjects is that CLA does not affect body weight or body composition. Some detrimental effects of thetrans-10,cis-12 CLA isomer have also been reported in terms of altered blood lipid composition and impaired insulin sensitivity. Finally, CLA has only limited effects on immune functions in man. However, there have been reports of some interesting isomer-specific effects of CLA on the blood lipid profile, but not on immune function. These isomer-specific effects need further investigation. Until more is known, CLA supplementation in man should be considered with caution.

Effects of conjugated linoleic acids on growth performance, serum lysozyme activity, lymphocyte proliferation,and antibody production in broiler chicks

This study was conducted to investigate the effect of dietary conjugated linoleic acids (CLA) on growth performance and immune responses in broiler chicks. A total of 240 day-old Arbor Acre male broiler chicks were randomly allotted into four dietary treatments with different inclusion levels of CLA (0, 2.5, 5.0 or 10.0 g/kg) for six weeks. Growth performance, peripheral blood lymphocyte (PBL) proliferation, lysozyme activity, phagocytic activity (carbon clearance) and serum antibody titers against Newcastle disease virus (NDV) vaccine were examined. There were no significant differences in growth performance among treatments (p > 0.05). Chicks fed CLA diets produced more lysozyme activity in serum than the control group at 2 and 6 weeks of age (p < 0.05). Dietary CLA enhanced the PBL proliferation in response to concanavalin A (ConA) at the age of 42 d (p < 0.05). Phagocytic ability was also affected by dietary CLA and chicks fed CLA diets had faster carbon clearance rate (p < 0.05), but antibody titers to NDV was not influenced by dietary CLA. The results of the study suggested that dietary CLA could enhance innate and cellular immune response in broiler chicks, and not affect the growth performance.

Trans-10,cis-12-conjugated linoleic acid increases phagocytosis of porcine peripheral blood polymorphonuclear cellsin vitro

Trans-10,cis-12-conjugated linoleic acid (t10c12-CLA) has been shown to alter immune function. PPARγ has been shown to potentially play an important role in regulating inflammatory and immune responses by modulating the activity of monocytes and macrophages. Previous studies have indicated that the phagocytic capacity of porcine peripheral blood polymorphonuclear cells (PMN) was enhanced by the culture supernatant fraction from t10c12-CLA-stimulated porcine peripheral blood mononuclear cells (PBMC) but not by t10c12-CLA itself. In the present study, we examined the effects of t10c12-CLA on PPARγ and TNF-α expression of porcine PBMC and the phagocytic capacity of PMN. t10c12-CLA increased TNF-α mRNA expression and production by PBMC. The phagocytic capacity of porcine PMN was enhanced by either culture supernatant fraction from PBMC treated with t10c12-CLA or recombinant porcine (rp) TNF-α. Anti-rpTNF-α polyclonal antibody inhibited the enhancement of PMN phagocytic capacity. t10c12-CLA also up regulated PPARγ mRNA expression in porcine PBMC. Bisphenol A diglycidyl ether, a PPARγ antagonist, not only completely negated the t10c12-CLA-stimulating effects on TNF-α expression and production by porcine PBMC, but also decreased the enhancement of PMN phagocytic capacity by the t10c12-CLA-stimulated porcine PBMC culture supernatant fraction. These results suggest that t10c12-CLA has an immunostimulating effect on porcine PMN phagocytic capacity, which is mediated by TNF-α from PBMC via a PPARγ-dependent pathway.

Conjugated linoleic acid and chromium lower body weight and visceral fat mass in high-fat-diet-fed mice

More than half of the U.S. population has a body mass index of 25 kg/m2 or more, which classifies them as overweight or obese. Obesity is often associated with comorbidities such as diabetes, cardiovascular diseases, and cancer. CLA and chromium have emerged as major dietary supplements that reduce body weight and fat mass, and increase basal metabolic rate in animal models. However, studies show that CLA induces insulin resistance in mice and in humans, whereas Cr improves insulin sensitivity. Hence, we designed the present study to examine the combined effect of CLA and Cr on body composition and insulin sensitivity in a Balb/c mice (n = 10/group) model of high-fat-diet-induced obesity. CLA alone lowered body weight, total body fat mass, and visceral fat mass, the last of which decreased further with the combination of CLA and Cr. This effect was accompanied by decreased serum leptin levels in CLA-fed and CLA + Cr-fed mice, and by higher energy expenditure (EE) and oxygen consumption (OC) in CLA + Cr-fed mice. Serum levels of glucose, insulin, the pro-inflammatory cytokines, tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6), as well as insulin resistance index (IRI), decreased with CLA, whereas CLA and Cr in combination had significant effects on insulin and IL-6 concentrations and IRI. In summary, CLA + Cr decreased body weight and fat mass in high-fat-diet-fed mice, which may be associated with decreased leptin levels and higher EE and OC.

Conjugated linoleic acid enhances glutathione synthesis and attenuates pathological signs in MRL/MpJ-Faslpr mice

Conjugated linoleic acid (CLA), a naturally occurring peroxisome proliferator-activated receptor gamma (PPAR gamma) ligand, exhibits proapoptotic, immunomodulatory, and anticancer properties. In this study, we examined the biological effects of CLA administration in the MRL/MpJ-Fas(lpr) mouse, an animal model of systemic lupus erythematosus (SLE). We found that CLA exerted apparently opposed activities in in vitro experiments, depending on its concentration: 100 microM CLA downregulated IFN gamma synthesis and cell proliferation of splenocytes, in association with apoptosis induction and a decrease of intracellular thiols (GSH + GSSG), whereas 25 microM CLA did not significantly influence cell proliferation but enhanced the expression of gamma-glutamylcysteine ligase catalytic subunit (GCLC) and intracellular GSH concentration. Interestingly, the antiproliferative effect at 100 microM was not inhibited by the PPAR gamma antagonist GW9662. In vivo, CLA administration drastically reduced SLE signs (splenomegaly, autoantibodies, and cytokine synthesis), a condition paralleled by the enhancement of GCLC expression and intracellular GSH content. Moreover, CLA administration significantly downregulated nuclear factor kappaB activity independent of PPAR gamma activation and apoptosis induction. In conclusion, enhanced GSH content and GCLC expression in CLA-treated mice suggest a novel biochemical mechanism underlying its immunomodulatory activity and the beneficial effects on murine SLE signs.

Effects of cis-9, trans-11, CLA in rats at intake levels reported for breast-fed infants

CLA intake in exclusively breast-fed infants is close to levels found to have physiological effects in animals. However, in the majority of studies mixtures of CLA isomers have been used and the independent effects of the major CLA isomer in human milk, cis-9,trans-11 CLA, at the intake level in exclusively breast-fed infants have hardly been studied. We therefore studied the effects of cis-9,trans-11 CLA on plasma lipids and glucose, immune function, and bone metabolism in growing rats. Thirty male Sprague-Dawley rats (n = 10/group) were fed either 20 mg/kg/d cis-9,trans-11 CLA and 20 mg/kg/d sunflower oil (CLA20), 40 mg/kg/d cis-9,trans-11 CLA (CLA40), or 40 mg/kg/d sunflower oil (placebo) for 8 wk. No significant differences between groups were found in plasma lipids, glucose, insulin, C-reactive protein, or lipid peroxidation. Liver fat content was lowest in the CLA20 group. In vitro interleukin 2 (IL-2) production increased, and tumor necrosis factor alpha, IL-1beta, prostaglandin E2, and leukotriene B4 production decreased in the CLA20 group. No differences between groups were detected in IL-4, IL-6, or interferon gamma production, plasma osteocalcin, insulin-like growth factor, or urinary deoxypyridinoline crosslinks. Plasma tartrate-resistant acid phosphatase 5b activity was significantly increased in the CLA40 group. The results indicate anti-inflammatory effects and enhanced T-cell function for the CLA20 group. No adverse effects were seen in the CLA20 group, whereas indications of increased bone resorption rate were observed in the CLA40 group.

Biological effects of conjugated linoleic acids in health and disease

Conjugated linoleic acid (CLA) is a mixture of positional and geometric isomers of octadecadienoic acid [linoleic acid (LA), 18:2n-6] commonly found in beef, lamb and dairy products. The most abundant isomer of CLA in nature is the cis-9, trans-11 (c9t11) isomer. Commercially available CLA is usually a 1:1 mixture of c9t11 and trans-10, cis-12 (t10c12) isomers with other isomers as minor components. Conjugated LA isomer mixture and c9t11 and t10c12 isomers alone have been attributed to provide several health benefits that are largely based on animal and in vitro studies. Conjugated LA has been attributed many beneficial effects in prevention of atherosclerosis, different types of cancer, hypertension and also known to improve immune function. More recent literature with availability of purified c9t11 and t10c12 isomers suggests that t10c12 is the sole isomer involved in antiadipogenic role of CLA. Other studies in animals and cell lines suggest that the two isomers may act similarly or antagonistically to alter cellular function and metabolism, and may also act through different signaling pathways. The effect of CLA and individual isomers shows considerable variation between different strains (BALB/C mice vs. C57BL/6 mice) and species (e.g., rats vs. mice). The dramatic effects seen in animal studies have not been reflected in some clinical studies. This review comprehensively discusses the recent studies on the effects of CLA and individual isomers on body composition, cardiovascular disease, bone health, insulin resistance, mediators of inflammatory response and different types of cancer, obtained from both in vitro and animal studies. This review also discusses the latest available information from clinical studies in these areas of research.

Fatty acid composition of liver, adipose tissue, spleen, and heart of mice fed diets containing t10, c12-, and c9, t11-conjugated linoleic acid

Conjugated linoleic acid (CLA) isomers have unique effects on tissue lipids. Here we investigated the influence of individual CLA isomers on the lipid weight and fatty acid composition of lipid metabolizing (i.e. liver and retroperitoneal adipose) and lipid sensitive (i.e. spleen and heart) tissues. Female mice (8 week old; n=6/group) were fed either a control or one of the two CLA isomer supplemented (0.5%) diets for 8 weeks. The cis-9, trans-11-CLA diet reduced the 18:1n-9 wt% by 20-50% in liver, adipose tissue, and spleen, reduced the spleen n-3 polyunsaturated fatty acid (PUFA) by 90%, and increased the n-6 PUFA wt% by 20-50% in all tissues except heart. The trans-10, cis-12-CLA reduced both the n-6 and n-3 PUFA wt% in liver (>50%), reduced the heart n-3 PUFA wt% by 25%, and increased the wt% of spleen n-3 PUFA by 700%. The functional consequences of such changes in tissue fatty acid composition need to be investigated.

Conjugated linoleic acid enhanced the immune function in broiler chicks

This study was undertaken to investigate the growth performance and immune responses of broiler chicks fed diets supplemented with conjugated linoleic acid (CLA). Two hundred and forty day-old Arbor Acre male broiler chicks were randomly allotted into four dietary treatments with different inclusion levels of CLA (0, 2.5, 5.0 or 10.0 g pure CLA/kg) for 6 weeks. Growth performance, lysozyme activity, peripheral blood mononuclear cell (PBMC) proliferation, prostaglandin E2 (PGE2) synthesis and antibody production were investigated. There were no significant differences in growth performance among treatments (P>0.05). Chicks fed 10.0 g CLA/kg diet produced 40 % and 49 % more lysozyme activity in serum and spleen than the control group at 21 d of age (P<0.05). Dietary CLA enhanced the PBMC proliferation in response to concanavalin A at the age of 21 and 42 d (P<0.05). Systemic and peripheral blood lymphocytic synthesis of PGE2 in chicks fed 10.0 g CLA/kg diet was significantly decreased by 57 % and 42 % compared to chicks fed control diet (P<0.05). Antibody production to sheep red blood cell and bovine serum albumin were elevated in either 2.5 or 10.0 g CLA/kg dietary treatments (P<0.05). The results indicated dietary CLA could enhance the immune response in broiler chicks, but did not alter the growth performance.

Effects of the individual isomers cis-9,trans-11 vs. trans-10,cis-12 of conjugated linoleic acid (CLA) on inflammation parameters in moderately overweight subjects with LDL-phenotype B

Immune-modulating effects of CLA have been reported in animals, but results are inconsistent. In humans, CLA has shown no effects or only minor effects on immune function. The objective of this study was to evaluate the immune-modulating effects of 3 g cis-9,trans-11 (c9,t11) vs. trans-10,cis-12 (t10,c12) CLA isomers in a population with a high risk of coronary heart disease characterized by moderate overweight (body-mass index, 25-32.5 kg/m2) in combination with LDL-phenotype B (> or = 35% small LDL cholesterol, density > or = 1.040 g/mL). After a run-in period of 1 wk, 42 men and women were randomly allocated to the c9,t11 CLA group, the t10,c12 CLA group, or the placebo group. Effects of 13 wk of consumption of 3 g of CLA isomers on cytokine production by ex vivo lipopolysaccharide (LPS)-stimulated peripheral blood mononuclear cells (PBMC) and whole blood, and on plasma C-reactive protein (CRP) concentrations were evaluated. To generate hypotheses for future studies, protein expression patterns of 42 cytokines, chemokines, and growth factors were evaluated with an antibody array in pooled, nonstimulated, fasting plasma samples. LPS induced interleukin (IL)-6, IL-8, and tumor necrosis factor-alpha production by PBMC, and whole blood as well as plasma CRP concentrations were not significantly changed by the c9,t11 and the t10,c12 CLA isomers. The cytokine expression profile in nonstimulated plasma suggested that both CLA isomers induced a specific inflammatory signature, in which the c9,t11 CLA group showed more activity in terms of numbers of proteins regulated. We conclude that daily consumption of 3 g of c9,t11 or t10,c12 CLA isomer did not affect LPS-stimulated cytokine production by PBMC or whole blood and plasma CRP levels. Inflammatory signatures in fasting, nonstimulated plasma as determined by an antibody array may indicate enhanced immune function by both CLA isomers.

The effects of conjugated linoleic acid supplementation on immune function in healthy volunteers

OBJECTIVE

To assess the effects of dietary supplementation using two isomeric blends of conjugated linoleic acid (CLA) on immune function in healthy human volunteers.

DESIGN

Double-blind, randomised, placebo-controlled intervention trial.

SUBJECTS AND INTERVENTION

A total of 55 healthy volunteers (n=20 males, n=35 females) were randomised into one of three study groups who received 3 g/day of a fatty acid blend containing a 50:50 cis-9, trans-11: trans-10, cis-12 CLA isomer blend (2 g CLA), and 80:20 cis-9, trans-11: trans-10, cis-12 (80:20) CLA isomer blend (1.76 g CLA) or linoleic acid (control, 2 g linoleic acid) for 8 weeks.

RESULTS

Supplementation with the 80:20 CLA isomer blend significantly (P< or =0.05) enhanced PHA-induced lymphocyte proliferation. CLA decreased basal interleukin (IL)-2 secretion (P< or =0.01) and increased PHA-induced IL-2 and tumor necrosis factor alpha (TNF(alpha)) production (P< or =0.01). However, these effects were not solely attributable to CLA as similar results were observed with linoleic acid. CLA supplementation had no significant effect on peripheral blood mononuclear cells IL-4 production, or on serum-soluble intercellular adhesion molecule-1 (sICAM-1) or plasma prostaglandin E2 (PGE2) or leukotreine B4 (LTB4) concentrations.

CONCLUSIONS

This study shows that CLA supplementation had a minimal effect on the markers of human immune function. Furthermore, supplementation with CLA had no immunological benefit compared with linoleic acid.

Increased immune response in mice consuming rice bran oil

BACKGROUND

Polyunsaturated fatty acids play a key role in a number of biological functions. Rice bran oil (RBO) is rich in linoleic acid, an essential n-6 fatty acid. n-6 fatty acids are said to have proinflammatory effects as a result of an increase in n-6 fatty acid-derived eicosanoids. RBO is also rich in gamma-oryzanol, a compound from the unsaponifiable fraction, with antioxidant properties.

OBJECTIVE

The aim of this work is to examine the effect of RBO-and/or gamma-oryzanol-enriched diets on the regulation of the immune response.

METHODS

4 week-old Balb/C mice were fed diets enriched with either RBO or high oleic-sunflower oil (HOSO), for one month. Serum samples, bone marrow-derived macrophages and lymphocytes from the spleen were collected.

RESULTS

Compared to HOSO, our results show that RBO modulates the immune system by enhancing B-lymphocyte proliferation (6842 +/- 2959 vs 10073 +/- 4186 cpm; HOSO vs RBO; n = 10 per group) and TH1-type cytokines such as IL-2 (55.85 +/- 18.2 vs 101.7 +/- 21.6 pg/ml) or TNF-alpha (49.12 +/- 18.6 vs 184.9 +/- 46.2 pg/ml; HOSO vs RBO) in a significant way (n = 10 per group). Moreover, the reduction found in the TH2 cytokine IL-4 (7.59 +/- 2.3 vs 4.48 +/- 1.6 pg/ml) and IgE (56.9 +/- 39.2 vs 42.4 +/- 35.2 ng/ ml; HOSO vs RBO, n = 10 per group) levels suggests RBO may have antiallergenic properties. To elucidate the role of gamma-oryzanol, a similar study was also carried out including diets enriched with refined RBO or HOSO containing gamma-oryzanol (2 %). Our results suggest that although gamma-oryzanol may modulate the immune system, it is not responsible for the overall immunostimulation effect seen for RBO.

CONCLUSIONS

RBO-enriched diets could be useful in situations where a potentiation of the immune response was required. The fatty acids composition, more than the unsaponifiable fraction, might be responsible for this effect.

Effects of cis-9,trans-11 and trans-10,cis-12 conjugated linoleic acid on immune cell function in healthy humans

BACKGROUND

Animal studies have suggested that conjugated linoleic acid (CLA), a natural component of ruminant meat and dairy products, may confer beneficial effects on health. However, little information on the effects of CLA on immune function is available, especially in humans. Furthermore, the effects of individual isomers of CLA have not been adequately investigated.

OBJECTIVE

This study investigated the effects of supplementing the diet with 3 doses of highly enriched cis-9,trans-11 CLA (0.59, 1.19, and 2.38 g/d) or trans-10,cis-12 CLA (0.63, 1.26, and 2.52 g/d) on immune outcomes in healthy humans.

DESIGN

The study had a randomized, double-blind, crossover design. Healthy men consumed 1, 2, and 4 capsules sequentially that contained 80% of either cis-9,trans-11 CLA or trans-10,cis-12 CLA for consecutive 8-wk periods. This regimen was followed by a 6-wk washout and a crossover to the other isomer.

RESULTS

Both CLA isomers decreased mitogen-induced T lymphocyte activation in a dose-dependent manner. There was a significant negative correlation between mitogen-induced T lymphocyte activation and the proportions of both cis-9,trans-11 CLA and trans-10,cis-12 CLA in peripheral blood mononuclear cell lipids. However, CLA did not affect lymphocyte subpopulations or serum concentrations of C-reactive protein and did not have any consistent effects on ex vivo cytokine production.

CONCLUSION

CLA supplementation results in a dose-dependent reduction in the mitogen-induced activation of T lymphocytes. The effects of cis-9,trans-11 CLA and trans-10,cis-12 CLA were similar, and there was a negative correlation between mitogen-induced T lymphocyte activation and the cis-9,trans-11 CLA and trans-10,cis-12 CLA contents of mononuclear cells.

Detection of conjugated C16 PUFAs in rat tissues as possible partial beta-oxidation products of naturally occurring conjugated linoleic acid and its metabolites

In a previous paper, we showed that naturally occurring conjugated linoleic acid (CLA) from butter fat is metabolized in vivo to higher metabolites such as conjugated diene (CD) 18:3, CD 20:3 and CD 20:4, all the while retaining the conjugated diene structure. In this paper, we describe the detection of two more metabolites with characteristic conjugated diene UV spectra. HPLC retention times, UV and MS spectra identified the CLA metabolites as CD 16:2 and CD 16:3. The accumulation of CD 16:2 was significantly higher than that of CD 16:3 in all tissues examined. Tissue distributions of CD 16:2 and CD 16:3 were similar, with plasma and adipose tissue showing the highest levels, while kidney had the lowest and the liver an intermediate level. CD 16 fatty acids accounted for about 20% of the total CLA metabolites. The kidney, however, was an exception where CD 16 fatty acids accounted for only 11% of total metabolites. Analyses of liver lipid classes showed that CD 16:2 and CD 16:3 were preferentially incorporated into neutral lipids. This preferential incorporation was very similar to CLA as shown previously. We hypothesize that CD 16:2 and CD 16:3 may be derived from partial beta-oxidation of CLA and CD 20:4, respectively, even though we cannot rule out that CD 16:3 may also be derived from CD 18:3 and CD 20:3. Incubation of skin human fibroblasts from X-linked adrenoleukodystrophy (ALD) patients with c9,t11 CLA showed that CD 16:2 formation in ALD cells was about 50% lower than control cells. This result may tempt to hypothesize that, at least in part, CD 16:2 is beta-oxidized in peroxisomes.

Evidence for potential mechanisms for the effect of conjugated linoleic acid on tumor metabolism and immune function: lessons from n-3 fatty acids

Conjugated linoleic acid (CLA) and the long-chain polyunsaturated n-3 fatty acids have been shown in vivo and in vitro to reduce tumor growth. Tumor growth could occur by slowing or stopping cell replication (by interfering with transition through the cell cycle), increasing cell death (via necrosis and/or apoptosis), or both. The anticancer effects of fatty acids, shown in vivo, could also be mediated by effects on the host's immune system. Although it is widely recognized that n-3 fatty acids can alter immune and inflammatory responses, considerably less is known about CLA. For n-3 fatty acids, several candidate mechanisms have been proposed for their immune effects, including changes in 1) membrane structure and composition, 2) membrane-mediated functions and signals (eg, proteins, eicosanoids), 3) gene expression, and 4) immune development. Considerable work has been done that shows the potential importance of CLA as an anticancer treatment; however, many questions remain as to how this effect occurs. This review summarizes the CLA and cancer literature and then uses the evidence for the anticancer immune and tumor properties of the long-chain n-3 fatty acids docosahexaenoic and eicosapentaenoic acids to suggest future research directions for mechanistic studies on CLA and cancer.

Contrasting effects oft10,c12- andc9,t11-conjugated linoleic acid isomers on the fatty acid profiles of mouse liver lipids

The purpose of this study was to examine the effects of two purified isomers of CLA (c9,t11-CLA and t10,c12-CLA) on the weights and FA compositions of hepatic TG, phospholipids, cholesterol esters, and FFA. Eight-week-old female mice (n = 6/group) were fed either a control diet or diets supplemented with 0.5% c9,t11-CLA or t10,c12-CLA isomers for 8 wk. Weights of liver total lipids and those of individual lipid fractions did not differ between the control and the c9,t11-CLA groups. Livers from animals fed the t10, c12-CLA diet contained four times more lipids than those of the control group; this was mainly due to an increase in the TG fractions (fivefold), but cholesterol (threefold), cholesterol esters (threefold), and FFA (twofold) were also significantly increased. Although c9,t11-CLA did not significantly alter the weights of liver lipids when compared with the control group, its intake was associated with significant reductions in the weight percentage (wt% of total FAME) of 18:1n-9 and 18:1n-7 in the TG fraction and with significant increases in the weight percentage of 18:2n-6 in the TG, cholesterol ester, and phospholipid fractions. On the other hand, t10,c12-CLA intake was linked with a significant increase in the weight percentage of 18:1n-9 and a decrease in that of 18:2n-6 in all lipid fractions. These changes may be the result of alterations in the activity of delta9-desaturase (stearoyl CoA desaturase) and the enzymes involved in the metabolism of 18:2n-6. Thus, the two isomers differed not only in their effects on the weights of total liver lipids and lipid fractions but also on the FA profile of the lipid fractions.

Modulation of immune and inflammatory responses by dietary lipids

PURPOSE OF REVIEW

There continues to be considerable interest in the modulating effect of dietary lipids on immune and inflammatory responses. Although controversy still exists in research in this area, new concepts and approaches have emerged providing useful suggestions. Analysis of the recent findings will help in understanding certain paradoxical findings as well as introducing new strategies to guide future studies.

RECENT FINDINGS

The tissue polyunsaturated fatty acid composition was found to be correlated with changes in certain indices of immune function in individuals consuming habitual diets. It seems that individuals or animals with disordered immune systems are more reactive to polyunsaturated fatty acid supplementation, and genetic variation is also a determinant. N-3 polyunsaturated fatty acids were shown to reduce both resistance to bacterial infection and host survival. The studies on other non-classic fatty acids also demonstrated interesting findings. A proposed immuno-enhancing effect of conjugated linoleic acid has not been confirmed by studies and even an adverse effect has been implied. Trans fatty acids have been shown to increase the production of inflammatory cytokines, which may contribute to their pro-atherogenic property.

SUMMARY

Current data suggest that the intake of polyunsaturated fatty acids, particularly n-3 polyunsaturated fatty acids, can modulate immune and inflammatory responses, although a discrepancy is still present. Some recent studies have provided useful information explaining possible underlying reasons. Factors such as genetic variation, health status, disease, immune response stage, stimulation type, and possibly age, all contribute to the responsiveness to polyunsaturated fatty acid supplementation in terms of immune function.

Trans-10,cis-12 CLA increases liver and decreases adipose tissue lipids in mice: possible roles of specific lipid metabolism genes

Although consumption of CLA mixtures has been associated with several health effects, less is known about the actions of specific CLA isomers. There is evidence that the t10,c12-CLA isomer is associated with alterations in body and organ weights in animals fed CLA, but the mechanisms leading to these changes are unclear. The purpose of this study was to determine the effects of two commonly occurring isomers of CLA on body composition and the transcription of genes associated with lipid metabolism. Eight-week-old female mice (n = 11 or 12/group) were fed either a control diet or diets supplemented with 0.5% c9,t11-CLA or t10,c12-CLA isomers or 0.2% of the peroxisome proliferator-activated receptor alpha (PPARalpha) agonist fenofibrate for 8 wk. Body and retroperitoneal adipose tissue weights were significantly lower (6-10 and 50%, respectively), and liver weights were significantly greater (100%) in the t10,c12-CLA and the fenofibrate groups compared with those in the control group; body and tissue weights in the c9,t11-CLA group did not differ from those in the control group. Livers from animals in the t10,c12-CLA group contained five times more lipids than in the control group, whereas the lipid content of the fenofibrate group did not differ from that in the control group. Although fenofibrate increased the mRNA for PPARalpha, t10,c12-CLA decreased it. These results suggest that PPARalpha did not mediate the effects of t10,c12-CLA on body composition. The CLA isomers and fenofibrate altered mRNA levels for several proteins involved in lipid metabolism, but the most striking difference was the reduction of mRNA for leptin and adiponectin in the t10,c12-CLA group. These initial results suggest that changes associated with energy homeostasis and insulin action may mediate the effects of t10,c12-CLA on lipid metabolism.

Modulation of body composition and immune cell functions by conjugated linoleic acid in humans and animal models: benefits vs. risks

We have reviewed the published literature regarding the effects of CLA on body composition and immune cell functions in humans and in animal models. Results from studies in mice, hamsters, rats, and pigs generally support the notion that CLA reduced depot fat in the normal or lean strains. However, in obese rats, it increased body fat or decreased it less than in the corresponding lean controls. These studies also indicate that t10,c12-CLA was the isomer that reduced adipose fat; however, it also increased the fat content of several other tissues and increased circulating insulin and the saturated FA content of adipose tissue and muscle. Four of the eight published human studies found small but significant reductions in body fat with CLA supplementation; however, the reductions were smaller than the prediction errors for the methods used. The other four human studies found no change in body fat with CLA supplementation. These studies also report that CLA supplementation increased the risk factors for diabetes and cardiovascular disease including increased blood glucose, insulin, insulin resistance, VLDL, C-reactive protein, lipid peroxidation, and decreased HDL. Most studies regarding the effects of CLA on immune cell functions have been conducted with a mixture of isomers, and the results have been variable. One study conducted in mice with the purified c9,t11-CLA and t10,c12-CLA isomers indicated that the two isomers have similar effects on immune cell functions. Some of the reasons for the discrepancies between the effects of CLA in published reports are discussed. Although significant benefit to humans from CLA supplementation is questionable, it may create several health risks in both humans and animals. On the basis of the published data, CLA supplementation of adult human diets to improve body composition or enhance immune functions cannot be recommended at this time.

Prevention of mammary cancer with conjugated linoleic acid: role of the stroma and the epithelium

Conjugated linoleic acid (CLA), found naturally in dairy products and ruminant meats, refers to isomers of octadecadienoic acid with conjugated double bonds. CLA inhibits both DMBA- and NMU-induced rat mammary carcinogenesis, and its antitumor efficacy is similar whether it is fed only during puberty, or continuously during promotion. Pubertal feeding is associated with a reduced proliferation of the epithelial cells within the terminal end buds (TEBs) and lobular epithelium, and results in a decrease in the epithelial density, suggesting a reduction in the carcinogen-sensitive target population. During promotion, CLA feeding induces apoptosis of preneoplastic lesions. The effects of CLA are mediated by a direct action on the epithelium, as well as by an indirect effect through the stroma. CLA is incorporated into the neutral lipids of mammary adipocytes, where it can serve as a local reservoir of CLA. Additionally, CLA induces the adipogenic differentiation of multipotent mammary stromal cells in vitro, and inhibits their development into three-dimensional capillary networks. This suggested that CLA might inhibit angiogenesis in vivo, a hypothesis that was subsequently confirmed. The antiangiogenic effect is mediated, in part, through a CLA-induced decrease in serum VEGF (vascular endothelial growth factor) and mammary gland VEGF and flk-1. Together, the data suggest that CLA may be an excellent candidate for prevention of breast cancer.