10t,12c-conjugated linoleic acid inhibits lipopolysaccharide-induced cyclooxygenase expression in vitro and in vivo

Dietary conjugated linoleic acid modulates morphology, selective immune parameters, and gene expressions in the intestine of grass carp

Conjugated linoleic acid (CLA) has been shown to exhibit anti-inflammatory properties in the intestine in mammals. However, the effect of CLA on intestinal immune response in fish is still unknown. Therefore, a 65-day growth trial was conducted to investigate the effects of dietary conjugated linoleic acid (CLA) on morphology, selective immune parameters, and gene expressions in the intestine of grass carp. Seven isonitrogenous and isolipidic diets were formulated as follows: 0 (control), 0.5 (CLA0.5), 1 (CLA1), 1.5 (CLA1.5), 2 (CLA2), 2.5 (CLA2.5), and 3 (CLA3) g CLA per 100g of feed. RESULTS: showed that dietary supplementation of 1.5-3% CLA significantly (P < 0.05) increased the fold and enterocyte heights in the PI and MI of grass carp. Complement 3 (C3) and immunoglobulin M (IgM) contents in three intestinal segments were significantly (P < 0.05) higher in fish fed with CLA1.5 to CLA2.5 diets compared to fish fed the control diet. CLA1.5 to CLA2.5 diets significantly (P < 0.05) increased the mRNA expression levels of anti-inflammatory cytokines (IL-10 and TGFβ1) and significantly (P < 0.05) reduced the mRNA expression levels of pro-inflammatory cytokines (IL-1β, IL-8, and TNF-α) in the PI, MI, and DI. This improved expression of anti-inflammatory cytokines and the inhibited expression of pro-inflammatory cytokines in the intestine of grass carp, might be mediated via TLR4/NF-κB-signaling pathway. Our results suggested that CLA1.5 to CLA2 diets improved intestinal morphology, increased the expression of anti-inflammatory cytokines, and inhibited the expression of pro-inflammatory cytokines in the intestine of grass carp. In conclusion, dietary supplementation of 1.5%-2% CLA show the anti-inflammatory therapeutic potential in the intestine of grass carp. The anti-inflammatory therapeutic potential of CLA might be mediated via TLR4/NF-κB-signaling pathway.

Consumption of conjugated linoleic acid (CLA)-supplemented diet during colitis development ameliorates gut inflammation without causing steatosis in mice

Dietary supplementation with conjugated linoleic acid (CLA) has been proposed for weight management and to prevent gut inflammation. However, some animal studies suggest that supplementation with CLA leads to the development of nonalcoholic fatty liver disease. The aims of this study were to test the efficiency of CLA in preventing dextran sulfate sodium (DSS)-induced colitis, to analyze the effects of CLA in the liver function, and to access putative liver alterations upon CLA supplementation during colitis. So, C57BL/6 mice were supplemented for 3 weeks with either control diet (AIN-G) or 1% CLA-supplemented diet. CLA content in the diet and in the liver of mice fed CLA containing diet were accessed by gas chromatography. On the first day of the third week of dietary treatment, mice received ad libitum a 1.5%-2.5% DSS solution for 7 days. Disease activity index score was evaluated; colon and liver samples were stained by hematoxylin and eosin for histopathology analysis and lamina propria cells were extracted to access the profile of innate cell infiltrate. Metabolic alterations before and after colitis induction were accessed by an open calorimetric circuit. Serum glucose, cholesterol, triglycerides and alanine aminotransaminase were measured; the content of fat in liver and feces was also accessed. CLA prevented weight loss, histopathologic and macroscopic signs of colitis, and inflammatory infiltration. Mice fed CLA-supplemented without colitis induction diet developed steatosis, which was prevented in mice with colitis probably due to the higher lipid consumption as energy during gut inflammation. This result suggests that CLA is safe for use during gut inflammation but not at steady-state conditions.

Manipulating the immune system for pigs to optimise performance

Disease and enhanced microbial load are considered to be major factors limiting the performance and overall efficiency of feed use by pigs in Australian piggeries. It is recognised that pigs exposed to conventional housing systems with high microbial loads grow 10–20% more slowly than do gnotobiotic pigs or pigs kept in ‘clean’ environments. Consequently, a proportion of pigs in any production cycle are continuously being challenged by their immediate environment, which can cause an immune response to be mounted. Such a process is physiologically expensive in terms of energy and protein (comprised of amino acids), with, for example, the enhanced rate of protein turnover associated with the production of immune cells, antibodies and acute-phase proteins increasing energy expenditure by 10–15% of maintenance needs and protein requirements by 7–10%. The requirements for lysine, tryptophan, sulfur-containing amino acids and threonine can be increased by a further 10%. The over-stimulation of the immune response with excess production of pro-inflammatory cytokines causes excessive production primarily of the prostaglandin E2 (PGE2), which contributes to anorexia, fever and increased proteolysis, and a concomitant reduction in pig performance. Prostaglandin E2 is produced from dietary and cell-membrane phospholipids via secretory phospholipase A2 (sPLA2) to produce arachidonic acid, which is catalysed by the COX-2 enzyme. Negating the negative effects of PGE2 appears not to adversely affect the ability of the immune system to combat pathogens, but improves pig performance. There are negative outcomes for pig health and productivity through both under- and over-stimulation of the immune response. This review briefly outlines the impact of immune stimulation on pigs and discusses strategies to optimise the immune response for pig health and performance.

Host-targeted approaches to managing animal health: old problems and new tools

Our fellow medical and regulatory scientists question the animal producer's dependence on antibiotics and antimicrobial chemicals in the production of animal products. Retail distributors and consumers are putting even more pressure on the animal industry to find new ways to produce meat without antibiotics and chemicals. In addition, federal funding agencies are increasingly pressuring researchers to conduct science that has application. In the review that follows, we outline our approach to finding novel ways to improve animal performance and health. We use a strict set of guidelines in our applied research as follows: (1) Does the work have value to society? (2) Does our team have the skills to innovate in the field? (3) Is the product we produce commercially cost-effective? (4) Are there any reasons why the general consumer will reject the technology? (5) Is it safe for the animal, consumer, and the environment? Within this framework, we describe 4 areas of research that have produced useful products, areas that we hope other scientists will likewise explore and innovate such as (1) methods to detect infection in herds and flocks, (2) methods to control systemic and mucosal inflammation, (3) improvements to intestinal barrier function, and (4) methods to strategically potentiate immune defense. We recognize that others are working in these areas, using different strategies, but believe our examples will illustrate the vast opportunity for research and innovation in a world without antibiotics. Animal scientists have been given a new challenge that may help shape the future of both animal and human medicine.

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.

Dietary trans-10,cis-12 CLA reduces murine collagen-induced arthritis in a dose-dependent manner

Dietary trans-10,cis-12 (t10c12) conjugated linoleic acid (CLA) has been shown to reduce inflammation in a murine collagen-induced arthritis (CA) model. To understand the anti-inflammatory potential of t10c12-CLA in the diet, the minimum dose of pure dietary t10c12-CLA capable of reducing CA was investigated. Because plasma inflammatory cytokines often do not reflect the progression of late-stage arthritis, inflamed tissue cytokine concentrations were also investigated in relation to increasing dietary t10c12-CLA amounts. Mice were randomly assigned to the following dietary treatments upon the establishment of arthritis: corn oil (CO) or 0.125%, 0.25%, 0.375%, or 0.5% t10c12-CLA (wt:wt) for 84 d. Sham mice (no arthritis) were fed CO and served as controls. Arthritic paw score, based on subjective assessment of arthritic severity, and paw thickness decreased linearly overall [16-65% (P < 0.001) and 0.5-12% (P < 0.001), respectively] as dietary t10c12-CLA increased (P < 0.001, R(2) < 0.81). Increasing dietary t10c12-CLA was associated with a decrease in plasma interleukin (IL)-1β at days 21 and 42 compared with CO-fed arthritic mice, such that mice fed ≥0.25% t10c12-CLA had IL-1β concentrations that were similar to sham mice. Plasma cytokines returned to sham mice concentrations by day 63 regardless of treatment; however, an arthritis-induced elevation in paw IL-1β decreased linearly as dietary t10c12-CLA concentrations increased at day 84 (P = 0.007, R(2) = 0.92). Similarly, increasing dietary t10c12-CLA linearly decreased paw tumor necrosis factor (TNF)-α (P = 0.05, R(2) = 0.70). In conclusion, ≥0.125% t10c12-CLA dose-dependently reduced inflammation in a murine CA model.

Organic production enhances milk nutritional quality by shifting fatty acid composition: a United States-wide, 18-month study

Over the last century, intakes of omega-6 (ω-6) fatty acids in Western diets have dramatically increased, while omega-3 (ω-3) intakes have fallen. Resulting ω-6/ω-3 intake ratios have risen to nutritionally undesirable levels, generally 10 to 15, compared to a possible optimal ratio near 2.3. We report results of the first large-scale, nationwide study of fatty acids in U.S. organic and conventional milk. Averaged over 12 months, organic milk contained 25% less ω-6 fatty acids and 62% more ω-3 fatty acids than conventional milk, yielding a 2.5-fold higher ω-6/ω-3 ratio in conventional compared to organic milk (5.77 vs. 2.28). All individual ω-3 fatty acid concentrations were higher in organic milk—α-linolenic acid (by 60%), eicosapentaenoic acid (32%), and docosapentaenoic acid (19%)—as was the concentration of conjugated linoleic acid (18%). We report mostly moderate regional and seasonal variability in milk fatty acid profiles. Hypothetical diets of adult women were modeled to assess milk fatty-acid-driven differences in overall dietary ω-6/ω-3 ratios. Diets varied according to three choices: high instead of moderate dairy consumption; organic vs. conventional dairy products; and reduced vs. typical consumption of ω-6 fatty acids. The three choices together would decrease the ω-6/ω-3 ratio among adult women by ∼80% of the total decrease needed to reach a target ratio of 2.3, with relative impact “switch to low ω-6 foods” > “switch to organic dairy products” ≈ “increase consumption of conventional dairy products.” Based on recommended servings of dairy products and seafoods, dairy products supply far more α-linolenic acid than seafoods, about one-third as much eicosapentaenoic acid, and slightly more docosapentaenoic acid, but negligible docosahexaenoic acid. We conclude that consumers have viable options to reduce average ω-6/ω-3 intake ratios, thereby reducing or eliminating probable risk factors for a wide range of developmental and chronic health problems.

Conjugated linoleic acid and calcium co-supplementation improves bone health in ovariectomised mice

Osteoporosis is a significant health concern for the elderly; conjugated linoleic acid (CLA) has been shown to improve overall bone mass when calcium is included as a co-supplement. However, potential effects of CLA and calcium on bone mass during a period of bone loss have not been reported. The purpose of this study was to determine how dietary calcium modulates the effects of conjugated linoleic acid (CLA) in preventing bone loss, using an ovariectomised mouse model. CLA supplementation significantly prevented ovariectomy-associated weight and fat mass gain, compared to non-supplemented controls. CLA significantly increased bone markers without major changes in bone mineral composition in the femur compared to respective controls. CLA treatment increased serum parathyroid hormone (PTH) significantly (p=0.0172), while serum 1,25-dihydroxyvitamin D3 concentration was not changed by CLA. Meanwhile, CLA significantly reduced femur tartrate resistant acid phosphatase (TRAP) activity, suggesting potential reduction of osteoclastogenesis. The data suggest that CLA, along with dietary calcium, has great potential to be used to prevent bone loss and weight gain associated with menopause.

Enzymatic interesterification of palm stearin with Cinnamomum camphora seed oil to produce zero-trans medium-chain triacylglycerols-enriched plastic fat

It is known that Cinnamomum camphora seed oil (CCSO) is rich in medium-chain fatty acids (MCFAs) or medium-chain triacylglycerols (MCTs). The purpose of the present study was to produce zero-trans MCTs-enriched plastic fat from a lipid mixture (500 g) of palm stearin (PS) and CCSO at 3 weight ratios (PS:CCSO 60:40, 70:30, 80:20, wt/wt) by using lipase (Lipozyme TL IM, 10% of total substrate) as a catalyst at 65 °C for 8 h. The major fatty acids of the products were palmitic acid (C16:0, 42.68% to 53.42%), oleic acid (C18:1, 22.41% to 23.46%), and MCFAs (8.67% to 18.73%). Alpha-tocopherol (0.48 to 2.51 mg/100 g), γ-tocopherol (1.70 to 3.88 mg/100 g), and δ-tocopherol (2.08 to 3.95 mg/100 g) were detected in the interesterified products. The physical properties including solid fat content (SFC), slip melting point (SMP), and crystal polymorphism of the products were evaluated for possible application in shortening or margarine. Results showed that the SFCs of interesterified products at 25 °C were 9% (60:40, PS:CCSO), 18.50% (70:30, PS:CCSO), and 29.2% (80:20, PS:CCSO), respectively. The β' crystal form was found in most of the interesterified products. Furthermore, no trans fatty acids were detected in the products. Such zero-trans MCT-enriched fats may have a potential functionality for shortenings and margarines which may become a new type of nutritional plastic fat for daily diet.

Conjugated linoleic acid decreases prostaglandin synthesis in bovine luteal cells in vitro

Feeding conjugated linoleic acids (CLA) improves reproductive performance in dairy cows; however, the molecular mechanisms by which CLA improves reproduction are not understood. The effect of the CLA isomers, trans-10, cis-12 CLA and cis-9, trans-11 CLA on synthesis of progesterone, PGE(2) , and PGF(2α) , in bovine luteal cells was determined in this study. Luteal cells from three cows were cultured in medium containing 0 or 0.1 µM of trans-10, cis-12 CLA and cis-9, trans-11 CLA in varying ratios in the presence and absence of 1 µM of forskolin. Prostaglandin and progesterone concentrations were not altered by CLA isomer and ratio. Luteal cells cultured in the presence of CLA had lower PGF(2α) concentrations (62.6 ± 13.4 pg/ml vs. 55.7 ± 12.2 pg/ml; P = 0.005) and, in the absence of forskolin, lower PGE(2) concentrations (65.3 ± 15.1 pg/ml vs. 32.4 ± 14.1 pg/ml; P = 0.002) in culture media, while progesterone concentrations were not altered (P = 0.63). Relative steady-state mRNA amounts of COX-2 (1.7-fold decrease; P = 0.002), PGE synthase (1.5-fold decrease; P = 0.03) and 3β-hydroxysteroid dehydrogenase (1.6-fold decrease; P = 0.0003) were lower in CLA-treated cultures, but CLA did not significantly alter mRNA amounts of PGE(2) 9-keto-reductase, StAR, and cytochrome P450 side chain cleavage enzyme. In conclusion, a potential mechanism exists by which trans-10, cis-12 CLA and cis-9, trans-11 CLA may improve reproductive performance in dairy cows, by suppressing PGF(2α) synthesis in luteal cells via attenuation of COX-2 gene expression.

Triennial Growth Symposium: a review of science leading to host-targeted antibody strategies for preventing growth depression due to microbial colonization

In this review, the science used to develop host-targeted therapies for improving animal growth and feed efficiency is presented. In contrast to targeting the microbiota of the host, endogenous host proteins are targeted to regulate an overactive inflammatory response in the host. Activation of the immune/inflammatory systems of an animal is costly in terms of growth and feed efficiency. For example, reduced rates of BW gain and poorer feed efficiency in vaccinated animals compared with nonvaccinated animals have been well documented. Also, the growth rate and feed efficiency of animals colonized by microorganisms is only 80 to 90% of their germ-free counterparts. Further evidence of a cost associated with immune activation is that strategies that enhance the immune capability of an animal can reduce animal growth and feed efficiency. Research now indicates that the growth-promoting effects of antibiotics are indirect, and more likely the result of reduced immune activation due to decreased microbial exposure. Studies of mechanisms by which immune/inflammatory activation reduces animal growth and feed efficiency have shown that cytokines of the acute inflammatory response (i.e., IL-1 and tumor necrosis factor α) are key triggers for host muscle wasting. Cytokine-induced muscle wasting is linked to PG signaling pathways, and it has been proposed that regulation of the PG signaling pathways provide host targets for preventing an overreactive or unwarranted inflammatory event. Intestinal secretory phospholipase A(2) (sPLA(2)) has been found to be a useful and accessible (i.e., found in the intestinal lumen) host target for the regulation of an overreactive inflammatory response to conventional environments. This review presents the science and strategy for the regulation of intestinal sPLA(2) using orally administered egg yolk antibody against the enzyme. Clinically healthy animals fed egg antibodies to sPLA(2) had improved growth and feed efficiency. Literature presented indicates that use of host-targeted strategies for regulating the overexpression of inflammatory processes in an animal may provide new mechanisms to improve animal growth and feed efficiency.

Individual isomers of conjugated linoleic acid reduce inflammation associated with established collagen-induced arthritis in DBA/1 mice

Previously, dietary conjugated linoleic acid [(CLA), an equal mixture of cis-9, trans-11 (c9t11) and trans-10, cis-12 (t10c12) CLA isomers], was found to reduce inflammation in the murine collagen antibody-induced arthritis model, but less so in the murine collagen-induced arthritis (CIA) model, an arthritic model dependent upon acquired immunity. Because CLA is known to alter the acquired immune response, it was hypothesized that feeding CLA after the establishment of arthritis would reduce paw swelling in the CIA model. In this study, upon the establishment of arthritic symptoms, mice were randomized to the following dietary treatments: corn oil (CO) control (n = 6), 0.5% c9t11-CLA (n = 8), 0.5% t10c12-CLA (n = 6), or 1% combined CLA (1:1 c9t11:t10c12-CLA, n = 6). Paws were scored for severity of arthritis and measured for changes in thickness during an 84-d study period. Dietary c9t11- and combined-CLA similarly decreased the arthritic score (29%, P = 0.036, P = 0.049, respectively, when normalized to initial score) and paw thickness (0.11 mm, P = 0.027, P = 0.035, respectively) compared with CO. Dietary t10c12-CLA reduced the arthritic score (41%, P = 0.007 when normalized) and paw thickness (0.12 mm, P = 0.013) relative to CO. Reduced interleukin-1beta on d 7 and 21 for all CLA treatments (n = 3) relative to CO suggested that antiinflammatory effects of CLA isomers might work by common mechanisms of known pathways involved in chronic inflammation. In conclusion, dietary CLA reduced inflammation associated with CIA, and both c9t11-CLA and t10c12-CLA exhibited antiinflammatory effects.

Lipophilic compound-mediated gene expression and implication for intervention in reactive oxygen species (ROS)-related diseases: mini-review

In addition to exhibiting antioxidant properties, conjugated linoleic acid (CLA) and vitamin E may modulate gene expression of endogenous antioxidant enzymes. Depending on cellular microenvironments, such modulation reflects either antioxidant or prooxidant outcomes. Although epidemiological/experimental studies have indicated that CLA and vitamin E have health promoting properties, recent findings from clinical trials have been inconclusive. Discrepancies between the results found from prospective studies and recent clinical trials might be attributed to concentration-dependent cellular microenvironment alterations. We give a perspective of possible molecular mechanisms of actions of these lipophilic compounds and their implications for interventions of reactive oxygen species (ROS)-related diseases.

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.

t10c12 conjugated linoleic acid suppresses HER2 protein and enhances apoptosis in SKBr3 breast cancer cells: possible role of COX2

Background

HER2-targeted therapy with the monoclonal antibody trastuzumab (Herceptin®) has improved disease-free survival for women diagnosed with HER2-positive breast cancers; however, treatment resistance and disease progression are not uncommon. Current data suggest that resistance to treatment in HER2 cancers may be a consequence of NF-κB overexpression and increased COX2-derived prostaglandin E2 (PGE₂). Conjugated linoleic acid (CLA) has been shown to have anti-tumor properties and to inhibit NF-κB activity and COX2.

Methods

In this study, HER2-overexpressing SKBr3 breast cancer cells were treated with t10c12 CLA. Protein expression of the HER2 receptor, nuclear NF-κB p65, and total and phosphorylated IκB were examined by western blot and immunofluorescence. PGE₂ levels were determined by ELISA. Proliferation was measured by metabolism of 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), and apoptosis was measured by FITC-conjugated Annexin V staining and flow cytometry.

Results/Conclusions

We observed a significant decrease in HER2 protein expression on western blot following treatment with 40 and 80 µM t10c12 CLA (p<0.01 and 0.001, respectively) and loss of HER2 protein in cells using immunoflourescence that was most pronounced at 80 µM. Protein levels of nuclear NF-κB p65 were also significantly reduced at the 80 µM dose. This was accompanied by a significant decrease in PGE₂ levels (p = 0.05). Pretreatment with t10c12 CLA significantly enhanced TNFα-induced apoptosis and the anti-proliferative action of trastuzumab (p = 0.05 and 0.001, respectively). These data add to previous reports of an anti-tumor effect of t10c12 CLA and suggest an effect on the HER2 oncogene that may be through CLA mediated downregulation of COX2-derived PGE₂.

Dietary trans-10, cis-12 conjugated linoleic acid reduces early glomerular enlargement and elevated renal cyclooxygenase-2 levels in young obese fa/fa zucker rats

Conjugated linoleic acid (CLA) slows the progression of disease in models of chronic kidney disease. Because obesity is associated with nephropathy and increased renal cyclooxygenase (COX) levels, the effects of dietary CLA on kidney function, morphology, and COX protein levels in the kidneys of young obese (fa/fa) Zucker rats, a model of metabolic syndrome, were examined. In study 1, 6-wk-old fa/fa and lean Zucker rats were given a mixture of CLA isomers (1.5% CLA, wt:wt) or the control diet (CTL) with no CLA for 8 wk. To examine specific isomer effects, study 2 used the same model with the following diets: 0.4% (g/g) cis-9, trans-11 (c9,t11) CLA; 0.4% trans-10, cis-12 (t10,c12) CLA; a combination of these 2 isomers (0.4% each); or CTL diets with no CLA. In study 1, fa/fa rats given the CLA mixture had 11% smaller kidney weights and 28% smaller glomeruli, and feed intake and body weight did not differ from the CTL rats. In study 2, diet also did not affect body weights, but fa/fa rats given a diet containing t10,c12 CLA had 7% lower kidney weights, 20% smaller glomeruli, and 39% lower COX-2 protein levels than CTL rats. In conclusion, dietary t10,c12 CLA reduces the enlargement of glomeruli in young obesity-associated nephropathy and is associated with lower protein levels of renal COX-2. Long-term studies with CLA supplementation are required to determine whether these changes would lead to reduction in development of renal disease associated with obesity.

Troglitazone but not conjugated linoleic acid reduces gene expression and activity of matrix-metalloproteinases-2 and -9 in PMA-differentiated THP-1 macrophages

Gene expression and activity of matrix-metalloproteinases (MMP)-2 and -9 in macrophages are reduced through peroxisome proliferator-activated receptor gamma (PPARgamma)-dependent inhibition of NF-kappaB. Since conjugated linoleic acids (CLAs) are PPARgamma ligands and known to inhibit NF-kappaB via PPARgamma, we studied whether CLA isomers are capable of reducing gene expression and gelatinolytic activity of MMP-2 and -9 in PMA-differentiated THP-1 macrophages, which has not yet been investigated. Incubation of PMA-differentiated THP-1 cells with either c9t11-CLA, t10c12-CLA or linoleic acid (LA), as a reference fatty acid, resulted in a significant incorporation of the respective fatty acids into total cell lipids relative to control cells (P<.05). Treatment of PMA-differentiated THP-1 cells with 10 and 20 micromol/L troglitazone but not with 10 or 100 micromol/L c9t11-CLA, t10c12-CLA or LA reduced relative mRNA concentrations and activity of MMP-2 and MMP-9 compared to control cells (P<.05). DNA-binding activity of NF-kappaB and PPARgamma and mRNA expression of the NF-kappaB target gene cPLA2 were not influenced by treatment with CLA. In contrast, treatment of PMA-differentiated THP-1 cells with troglitazone significantly increased transactivation of PPARgamma and decreased DNA-binding activity of NF-kappaB and relative mRNA concentration of cPLA2 relative to control cells (P<.05). In conclusion, the present study revealed that CLA isomers, in contrast to troglitazone, did not reduce gene expression and activity of MMP-2 and -9 in PMA-differentiated THP-1 macrophages, which is probably explained by the observation that CLA isomers neither activated PPARgamma nor reduced DNA-binding activity of NF-kappaB. This suggests that CLA isomers are ineffective in MMP-associated extracellular matrix degradation which is thought to contribute to the progression and rupture of advanced atherosclerotic plaques.

Effect of conjugated linoleic acid on bone formation and rheumatoid arthritis

Conjugated linoleic acid (CLA) has shown a variety of biologically beneficial effects. Dietary CLA inhibits eddosteal bone resorption, increases endocortical bone formation, and modulates the action and expression of cyclooxygenase (COX) enzyme, thereby decreasing prostaglandin-dependent bone resorption. CLA also enhances calcium absorption and may improve bone formation in animals, although results are not consistent. Since CLA can also affect inflammatory cytokines, it is hypothesized that CLA may be a good tool for prevention or reduction of rheumatoid arthritis symptoms. The possible mechanisms by which CLA prevents rheumatoid arthritis as well as other inflammatory diseases is discussed.

Conjugated linoleic acids can change phagocytosis of human monocytes/macrophages by reduction in Cox-2 expression

Prostaglandin E2 produced endogenously (by cyclooxygenases) can regulate macrophage phagocytosis. Cyclooxygenase activity reduction (mainly through inhibition of inducible Cox-2) can induce PGE2 synthesis depression and can activate the phagocytosis process. There are no reports in the literature explaining whether conjugated linoleic acid dienes (trans-10, cis-12 CLA and cis-9, trans-11 CLA) modify the phagocytic activity of human macrophages. For the purpose of this study, monocytes were isolated from venous blood, incubated for 7 days with 30 microM CLAs, and then (in some experiments) LPS (1 microg/mL) was added to the medium. Subsequently, monocyte/macrophage phagocytosis, NF-kappaB transcription factor activity, Cox-2 and PPARgamma mRNA expression (and the amounts of Cox-2 and PPARgamma proteins) and PGE2 synthesis were determined. Both CLA isomers increased macrophage phagocytosis through inhibition of Cox-2 expression (might by inactivation the NF-kappaB pathway). The inhibition of mRNA Cox-2 expression contributed (particularly with respect to trans-10, cis-12 CLA) to a decrease in protein Cox-2 synthesis and to reduction of prostaglandin E2 content in the cell. The inhibition of PGE2 synthesis (by CLA treatment) enhanced the phagocytosis process in macrophages.

Mechanisms by which fatty acids regulate leucocyte function

Fatty acids (FAs) have been shown to alter leucocyte function and thus to modulate inflammatory and immune responses. In this review, the effects of FAs on several aspects of lymphocyte, neutrophil and macrophage function are discussed. The mechanisms by which FAs modulate the production of lipid mediators, activity of intracellular signalling pathways, activity of lipid-raft-associated proteins, binding to TLRs (Toll-like receptors), control of gene expression, activation of transcription factors, induction of cell death and production of reactive oxygen and nitrogen species are described in this review. The rationale for the use of specific FAs to treat patients with impaired immune function is explained. Substantial improvement in the therapeutic usage of FAs or FA derivatives may be possible based on an improvement in the understanding of the precise molecular mechanisms of action with respect to the different leucocyte types and outcome with respect to the inflammatory responses.

A mechanistic approach to understanding conjugated linoleic acid's role in inflammation using murine models of rheumatoid arthritis

A naturally occurring fatty acid, conjugated linoleic acid (CLA), reduces immune-induced TNF and inducible cyclooxygenase (COX-2) expression; key mediators of inflammation in rheumatoid arthritis (RA). On the basis of previous work, it was hypothesized that dietary CLA would act as an anti-inflammatory agent in select animal models of RA. In the collagen antibody-induced arthritis (CAIA) model, mice fed CLA (mixed isomers of c9, t11, and t10, c12-CLA) for 3 wk before anticollagen antibody injection had reduced lipopolysaccharide-induced plasma TNF levels and had arthritic scores that were 60% of mice fed corn oil (CO). In the collagen-induced arthritis (CIA) model, mice fed mixed isomers of CLA for 21 days before immunization had lower IgG(1) titers, earlier signs of joint inflammation, but similar arthritis scores compared with CO fed mice during the remaining 70-day post-injection period. Beginning on day 80 to 133, CLA-fed mice had arthritic scores 70% that of the CO-fed mice. In a second CIA experiment, CLA was fed only after the booster injection. Plasma IgG(1) levels were not reduced and arthritis onset was delayed 4 days in CLA-fed mice compared with the CO-fed mice. Peak arthritis score was similar between CLA and CO-fed mice from day 35 to 56. Because CLA reduced inflammation in the CAIA model, delayed onset of arthritis in the CIA model (CIA experiment 2) and reduced arthritis score after day 80 in the CIA model (CIA experiment 1), we concluded that dietary CLA exhibited anti-inflammatory activity that was dependent on antibody.

Conjugated linoleic acid: a functional nutrient in the different pathophysiological components of the metabolic syndrome?

PURPOSE OF REVIEW

Much attention has focused on the therapeutic potential of conjugated linoleic acid with the most abundant isomers being cis-9,trans-11 conjugated linoleic acid and trans-10,cis-12 conjugated linoleic acid. Initial animal studies associated conjugated linoleic acid with beneficial health properties, such as reducing the risk of cancer, diabetes, atherosclerosis, inflammation and obesity. This review has appraised the evidence in relation to the effect of conjugated linoleic acid on components of the metabolic syndrome (clinically or experimentally), in particular, obesity, insulin resistance, atherosclerosis and inflammation.

RECENT FINDINGS

More recent human conjugated linoleic acid supplementation studies have often shown conflicting and less convincing health benefits. The marked variation between studies may reflect the isomer-specific effect of the individual conjugated linoleic acid isomers, which can often have opposing effects. Detrimental effects have been observed in some studies, in particular after supplementation with the trans-10,cis-12 conjugated linoleic acid isomer.

SUMMARY

Further studies and long-term clinical trials will be required to determine the efficacy and safety of conjugated linoleic acid isomers before conjugated linoleic acid could be considered as a functional nutrient in humans.

t10,c12 conjugated linoleic acid induces compensatory growth after immune challenge

Previous work demonstrated that feeding commercial preparations of conjugated linoleic acid (CLA) [a 50:50 mixture of c9,t11 and t10,c12 CLA (cCLA)] partially overcame lipopolysaccharide (LPS)-induced growth depression. The objective of this study was to determine which CLA isomer was responsible for the reduction of LPS-induced growth depression. Dietary cCLA supplementation for 3 weeks protected mice from LPS-induced weight loss 24 h after injection compared to mice fed isocaloric and isonitrogenous control diets supplemented with either corn oil (CO) or a mixture of CO and olive oil. Dietary c9,t11 or t10,c12 CLA led to body weight loss intermediate to controls and cCLA. After LPS-induced weight loss, the t10,c12 CLA fed mice regained weight faster than the control or c9,t11 CLA fed mice. Dietary t10,c12 CLA and cCLA reduced plasma tumor necrosis factor 2 h after LPS stimulation. While neither c9,t11 nor t10,c12 CLA isomers alone protected from immune-induced weight loss, the t10,c12 CLA isomer induced compensatory gain.

NF-κB independent inhibition of lipopolysaccharide-induced cyclooxygenase by a conjugated linoleic acid cognate, conjugated nonadecadienoic acid

10t, 12c-CLA was shown to inhibit COX-2 expression through the NF-kappaB pathway. In the current study, conjugated nonadecadienoic acid (CNA) was shown to decrease inducible COX-2 protein and mRNA and PGE(2) release to the similar extent as 10t, 12c-CLA in Raw264.7 macrophage. However, unlike 10t, 12c-CLA, inhibition of COX-2 mRNA/protein by CNA was independent of the NF-kappaB pathway. The data indicate the regulation of COX-2 by select conjugated fatty acids and hence their anti-inflammatory actions could operate through different signal transduction pathways.

Selective conjugated fatty acids inhibit guinea pig platelet aggregation

Conjugated linoleic acids have been shown to reduce eicosanoid release from select tissues and/or cells. To elucidate effects of conjugated linoleic acid isomers on cyclooxygenase-1 (COX-1) activity and their application as platelet aggregation inhibitors, conjugated linoleic acid isomers and conjugated nonadecadienoic acid were incubated with ovine COX-1 and Raw264.7 macrophage to examine their effects on COX-1 activity. The effects were further examined in collagen and ADP-induced guinea pig whole blood platelet aggregation. Fatty acids tested were shown to inhibit COX-1 enzymatic activity. However, only 10t, 12c-conjugated linoleic acid, 9t, 11t-conjugated linoleic acid and conjugated nonadecadienoic acid inhibited collagen and ADP-induced platelet aggregation with IC(50) 125.9 microM (74.2 microM to 213.4 microM, 95% confidence interval), 99.3 microM (52.8 microM to 187.2 microM, 95% confidence interval) and 124.3 microM (85.1 microM to 181.5 microM, 95% confidence interval) respectively in collagen-induced aggregation. TxB(2) release was also appreciably inhibited by 10t, 12c-conjugated linoleic acid, 9t, 11t-conjugated linoleic acid and conjugated nonadecadienoic acid. Based on these data, we conclude 10t, 12c-conjugated linoleic acid, 9t, 11t-conjugated linoleic acid and conjugated nonadecadienoic acid are platelet aggregation inhibitors while 9c, 11t-conjugated linoleic acid is a moderate inhibitor and linoleic acid, and 9c, 11c-conjugated linoleic acid have no effect on whole blood platelet aggregation.