Dietary conjugated linoleic acid differentially alters fatty acid composition and increases conjugated linoleic acid content in porcine adipose tissue

Conjugated linoleic acids (CLA) have been shown to decrease body fat content in pigs. It is possible that feeding pigs diets rich in CLA may increase carcass lipid CLA to levels that could provide health benefits when included as a part of a healthy diet. Therefore, the aim of the present study was to determine whether dietary CLA supplementation has any effect on the fatty acid composition of subcutaneous and intramuscular adipose tissue in pigs. Thirty-five female cross bred (Large White x Landrace) pigs (initial weight 57.2 kg and initial P2 back fat 11.5 mm) were used in the present study. Pigs were housed individually and randomly allocated to one of six dietary treatments (0.00, 1.25, 2.50, 5.00, 7.50 and 10.00 g CLA55 (55 g CLA isomers/100 g total fatty acids; Natural Lipids Ltd, Hovdebygda, Norway)/kg) and fed their respective diets for 8 weeks. Twelve CLA isomers in the diet and in pig tissue lipids were separated by Ag+-HPLC. CLA was incorporated at fivefold higher levels in subcutaneous fat as compared with intramuscular fat and in a dose-dependant manner. Overall, the transfer efficiency of CLA was maximized at 5.00 g CLA55/kg. However, there was clear selectivity in the uptake or incorporation of cis,trans-9,11 isomer over the trans,cis-10,12 isomer. In general, CLA supplementation produced significant changes in skeletal muscle and adipose tissue fatty acid composition, indicating that dietary CLA had a potent affect on lipid transport and metabolism in vivo. Significant increases in myristic, palmitic and palmitoleic acids and a reduction in arachidonic acid were observed, suggesting an alteration in activity of delta5-, delta6- and delta9-desaturases in pig adipose tissue. In conclusion, feeding pigs diets supplemented with CLA increases carcass lipid CLA, but also results in changes in the fatty acid profile in pig fat that could potentially outweigh the benefits of CLA.     

Incorporation of conjugated linoleic acid isomers into porcine erythrocytes

Purpose

The aim of the current study was to determine the incorporation of cis (c) 9, trans (t) 11-conjugated linoleic acid (CLA) and t10, c12-CLA into porcine erythrocytes—both isomers were supplemented in equal proportions.

Methods

The study group consisted of 16 piglets randomly assigned into experimental and control group. For the period of 5 weeks, the piglets from the experimental group were receiving a 1.2 % CLA supplement while the controls were supplemented with the same amount of sunflower oil. For the remaining 7 weeks, the piglets were fed without a supplement. Blood samples to evaluate incorporation of CLA into erythrocyte membranes were taken from all animals on weekly basis.

Results

Compared to t10, c12-CLA isomer, proportion of c9, t11-CLA isomer in the membrane of erythrocytes was higher for the whole time of the study period. After 4 weeks of feeding, it approaches the plateau. The peak value for both isomers was measured at the end of week 5, with a value of 3.24 g c9, t11-CLA/100 g of fatty acids and a 1.09 g t10, c12-CLA/100 g of fatty acids (p < 0.0001). After cessation of supplementation, the proportion of both isomers gradually decreased to be almost completely washed out—in 7 weeks.

Conclusions

During supplementation with equivalent amounts of CLA isomers, their proportion in membranes of porcine erythrocytes increases with time, with higher proportion of c9, t11-CLA. CLA isomers probably differently incorporate into different cell membranes at different species which could explain its various biological functions.     

Nutritional regulation of porcine bacterial-induced colitis by conjugated linoleic acid

Excessive intake of saturated fatty acids and/or linoleic acid favors the induction of an array of lipid mediators and cytokines enhancing inflammatory responses. Conversely, dietary supplementation with (n-3) fatty acids or vitamin D ameliorates inflammation and autoimmune diseases. Although it was well accepted that conjugated linoleic acid (CLA) prevented diseases with a common inflammatory pathogenesis (i.e., cancer and atherosclerosis), no studies were available on the roles of CLA in mucosal inflammation. The present study was designed to investigate the anti-inflammatory actions and molecular mechanisms underlying the regulation of colonic health by CLA. We hypothesized that colonic inflammation can be ameliorated by dietary CLA supplementation. To test this hypothesis, inflammation of the colonic mucosa was triggered by challenging pigs fed either soybean oil-supplemented or CLA-supplemented diets with an enteric bacterial pathogen (i.e., Brachyspira hyodysenteriae). Immunoregulatory cytokines and peroxisome proliferator-activated receptor-gamma (PPAR-gamma) mRNA expression were assayed in colonic lymph nodes and colon of pigs. Colonic mucosal lesions and lymphocyte subset distribution were evaluated by histology and immunohistochemistry. Supplementation of CLA in the diet before the induction of colitis decreased mucosal damage; maintained cytokine profiles (i.e., interferon-gamma and interleukin-10) and lymphocyte subset distributions (i.e., CD4+ and CD8+), resembling those of noninfected pigs; enhanced colonic expression of PPAR-gamma; and attenuated growth failure. Therefore, CLA fed preventively before the onset of enteric disease attenuated inflammatory lesion development and growth failure.     

Dietary conjugated linoleic acid positively affects immunologic variables in lactating sows and piglets

We studied the effects of conjugated linoleic acid (CLA) on metabolic and immunologic variables in lactating sows and piglets. Gestating sows (n = 16) were assigned to 1 of 2 weight- and parity-matched groups supplemented with 0% (C) or 0.5% (T) of a CLA preparation containing 50% CLA isomers. Supplementation started in late pregnancy and continued throughout lactation. At weaning, 80 piglets, half from each group of sows, were assigned to 0% CLA (C) or 0.5% CLA (T). Thus, there were four groups of 20 piglets: C-C, C-T, T-T, and T-C. Body weight and the number of piglets per litter at birth and weaning, and the chemical composition of colostrum did not differ among the groups. CLA affected the fatty acid composition of colostrum fat; palmitoleic and gamma-linolenic acid were significantly lower compared with controls, whereas eicosenoic and eicosatrienoic acids were significantly higher. Feeding CLA increased (P < 0.05) colostrum IgG in sows. Sows fed CLA had higher (P < 0.05) serum leptin, IgG, and lysozyme. Nursing piglets from CLA-fed sows had significantly higher (P < 0.01) serum lysozyme and IgG. Consumption of CLA did not affect postweaning growth. Postweaning piglets fed CLA (T-T, C-T) had a higher IgG titer at 25 d (P < 0.05) and 35 d (P < 0.01) after weaning. Serum lysozyme was also higher at 25 d (P < 0.05) in CLA-fed piglets (T-T, C-T). At 35 d, serum alpha-1 acylglicoprotein was lower (P < 0.05) in piglets fed CLA. Dietary CLA had a positive effect on immunologic variables in lactating sows and piglets.     

Dietary conjugated linoleic acid reduces adiposity in lean but not obese Zucker rats

Recent studies have demonstrated a reduction in body fat in growing animals fed conjugated linoleic acid (CLA). Two experiments were conducted to extend these observations to obese rats so that the mechanism of the actions of CLA might be more easily elucidated. In experiment 1, male lean and obese Zucker rats were fed diets containing either 0 or 0.5% CLA for 5 wk. There was no effect of diet on growth rate or food intake. Dietary CLA reduced retroperitoneal and inguinal fat pad weights in the lean rats but increased fat pad weights in the obese genotype (diet x genotype interaction; P < 0.05). Determination of fat pad cellularity indicated that these changes in fat pad weight were due to a reduction or increase in average fat cell size for the lean and obese Zucker rats, respectively. In experiment 2, we sought to reproduce these effects on fat pad size, as well as to determine the effect of dietary CLA on the catabolic response to bacterial endotoxin injection in obese Zucker rats. Growing female lean and obese Zucker rats were fed diets containing 0 or 0.5% CLA for 8 wk. On d 28, each rat was injected intraperitoneally with lipopolysaccharide from Escherichia coli serotype 055:B5 (1 mg/kg body weight) and body weight was determined over the next 96 h. There was a diet x genotype interaction (P < 0.05) for the body weight response to lipopolysaccharide 24 h postinjection. Lean rats fed CLA lost less weight than did lean controls, but obese rats fed CLA lost more weight than did obese controls. As in the first experiment, there was a diet x genotype (P < 0.05) for the effect of treatment on retroperitoneal fat pad weights determined at the end of the experiment. Lean rats fed CLA had smaller RP fat pads than did lean controls, but obese rats fed CLA once again had heavier RP fat pads than did obese controls. These results indicate that CLA reduces body fat and catabolic response to endotoxin injection in lean Zucker rats but not in the obese genotype. The observed interaction between diet and genotype warrants additional investigation into the specific mechanism(s) of the biological activities of CLA.     

Dietary conjugated linoleic acid reduces lipid peroxidation by increasing oxidative stability in rats

The antioxidative effect of conjugated linoleic acid (CLA) was examined by determining lipid peroxidation and antioxidative enzyme activities. Male Sprague-Dawley rats were fed one of the experimental diets-normal diet, vitamin E-deficient control diet, 0.5% CLA vitamin E-deficient diet, or 1.5% CLA vitamin E-deficient diet for 5 wk. Hepatic thiobarbituric acid reactive substances (TBARS) were increased in the vitamin E-deficient control group, but they were was significantly lowered in the CLA groups. Similarly, hepatic glutathione peroxidase activity was increased in the vitamin E-deficient diet and reduced by CLA supplementation. In addition, CLA caused a significant decrease in superoxide dismutase activity while having no effect on catalase activity. Analyses of the fatty acid composition revealed that dietary CLA was incorporated into hepatic microsomal membrane dose-dependently. Compared to the vitamin E-deficient control, CLA resulted in significantly higher saturated and monounsaturated fatty acids (palmitic and oleic acids) while lowering levels of oxidation-susceptible polyunsaturated fatty acids (linoleic, linolenic, and arachidonic acids) in both plasma and hepatic membrane. The concentrations of plasma cholesterol and triacylglycerol (TG) were lower in the 1.5% CLA group than in other groups. These results suggest that dietary CLA has antiatherosclerotic and antioxidant activity by increasing oxidative stability in plasma and hepatic membrane in the vitamin E-deficient rats.     

Effects of conjugated linoleic acid on linoleic and linolenic acid metabolism in man

Evidence from animal studies suggests that conjugated linoleic acid (CLA) modulates plasma and tissue appearance of newly synthesized PUFA. The effects of a 1.2g (0.5 % energy) daily intake of the cis-9,trans-11 (c9,t11) isomer of CLA, trans-10,cis-12 (t10,c12) isomer of CLA or olive oil (placebo) on linoleic acid (LA) and linolenic acid (LNA) metabolism in healthy human volunteers was investigated. Fifteen subjects were fed an experimental diet and supplemented with c9,t11-CLA, t10,c12-CLA or placebo for 7 d before consuming a tracer dose of U-[(13)C]LA (50 mg) and U-[(13)C]LNA (50 mg). Blood samples were taken at 0, 2, 4, 6, 8, 24, 48, 72 and 168 h and analysed using high-precision MS. No differences between the groups in peak plasma [(13)C]LA (10.3-11.6 % of dose), [(13)C]LNA (2.5-2.9 % of dose), [(13)C]arachidonic acid (0.09-0.12 % of dose), [(13)C]EPA (0.04-0.06 % of dose) or [(13)C]DHA (0.06-0.10 % of dose) were detected. Concentration v. time curves (area under the curve) also showed no significant differences between groups. This suggests that, in healthy human subjects consuming a diet with adequate intake of essential fatty acids, CLA does not affect metabolism of LA or LNA.     

The change in conjugated linoleic acid concentration in blood of Japanese fed a conjugated linoleic acid diet

Conjugated linoleic acid (CLA) is a collective term used for fatty acids with a conjugated double bond that are geometrical and positional isomers of linoleic acid. Anti-obesity and anti-cancer properties, an immunopotentiation effect, and promotion of bone formation by CLA have been shown in cell culture and animal studies. A mixture of 9c11t- and 10t12c-CLA is now used as a health food supplement after testing in clinical trials. These trials focused on improvement of lipid metabolism by CLA, whereas few studies have examined absorption and metabolism of CLA in humans. In addition, there is no report concerning absorption and metabolism of CLA in Japanese. This study was designed to examine CLA concentration in blood, the elimination rate of CLA, and metabolic differences between 9c11t-CLA and 10t12c-CLA in blood in Japanese who ingested CLA (about 2 g/d, equal weights of 9c11t-CLA and 10t12c-CLA) for 3 wk. Blood samples were collected 1 wk before the 3-wk period, on the first and last days of the period, and 1 wk after the end of the period, and the CLA concentration and distribution in blood were investigated. The CLA concentration in blood was significantly increased by CLA ingestion and reached 36 μmol/L. The CLA concentration in blood one week after the intake period was significantly lower than that at the end of CLA intake. The 10t12c-CLA level in plasma decreased faster than that of 9c11t-CLA. This suggests faster metabolism (fatty acid β oxidation) of 10t12c-CLA compared with 9c11t-CLA.     

Dietary conjugated linoleic acid reduces rat adipose tissue cell size rather than cell number

We investigated the basis for the reduction in fat pad size in rats fed conjugated linoleic acid (CLA). In the first study, growing female Sprague-Dawley rats (initial weight150 g) were fed diets containing 0, 0.25 and 0.5 g/100 g diet of a purified (97% CLA) and 0.5% of a feed-grade (55% CLA) source of CLA for 5 wk to determine the effects on growth performance and fat mass. There was no effect of CLA on growth rate or food intake. Dietary CLA reduced retroperitoneal fat pad weight 13, 25 and 32% in rats fed 0.25 and 0. 5% of the pure CLA and 0.5% of the feed-grade CLA, respectively (P < 0.05). Similar effects were observed in the parametrial fat pad. The reduced pad size was due to smaller adipocyte size rather than a reduced cell number. Relative to the control group, mean cell volume was 15, 28 and 29% lower in tissue from rats fed 0.25 and 0.5% of the pure CLA and 0.5% of the feed-grade CLA, respectively (P < 0.01). In the second study, rats were fed CLA (0 vs. 0.5%) for 7 or 49 d. Reductions in fat pad weight were observed within 7 d. In addition, the effects of CLA on energy metabolism were studied in the chronically fed rats. There were no significant effects of CLA on oxygen consumption, CO(2) or heat production. During wk 4 of feeding, but not at other times, there was a 5% lower respiratory quotient in CLA-fed rats (P < 0.05). There was a time-dependent accumulation of CLA in adipose tissue and a decrease in monounsaturated fatty acids. These results suggest that the reduction in fat mass in rats fed CLA can be accounted for by a reduction in cell size rather than a change in cell number.     

Dietary conjugated linoleic acid affects morphofunctional and chemical aspects of subcutaneous adipose tissue in heavy pigs

We investigated the in vivo effects of dietary conjugated linoleic acid (CLA) on subcutaneous adipose tissue from heavy pigs to clarify the involvement of possibly different causative effects in the established antiadipogenic effect of CLA. Pigs [n = 36; initial body weight, 106 kg live weight (LW)] were assigned to 1 of 2 LW-matched groups supplemented with either 0 or 0.75% of a CLA preparation containing 50% CLA isomers. The pigs were slaughtered at 155 kg LW and adipose tissue analyzed. CLA supplementation affected ash content, and decreased iodine values (P < 0.01) and adipocyte size (P < 0.05). The fat content of adipose tissue was lower (P < 0.05) in females than castrated males, and females had smaller (P < 0.01) adipocytes than castrated males. Neither CLA nor sex influenced adipocyte lipid droplet diameter or the extent of lipid peroxidation as determined by quantitation of Schiff's histochemical reaction. NADPH-diaphorase was not influenced by CLA treatment. Preadipocyte proliferation rates were lower in pigs fed CLA (P < 0.05), whereas the number of adipocyte apoptotic nuclei was greater (P < 0.05). Preadipocyte proliferation was also greater (P < 0.05) in females than castrated males. Neuronal and endothelial nitric oxide synthase activities did not differ between groups in adipose tissue vessels, but inducible nitric oxide synthase expression in adipocytes was lower in pigs fed CLA (P = 0.05). These findings suggest that the antiadipogenic effect of CLA in heavy pigs is not a direct effect but may occur by downregulation of a NO-mediated lipolytic pathway.     

Colonic anti-inflammatory mechanisms of conjugated linoleic acid

Conjugated linoleic acid (CLA) is a mixture of positional (e.g. 7,9; 9,11; 10,12; 11,13) and geometric (cis or trans) isomers of octadecadienoic acid. This compound was first shown to prevent mammary carcinogenesis in murine models. Later investigations uncovered a number of additional health benefits, including decreasing atherosclerosis and inflammation while enhancing immune function. The mechanisms of action underlying these biological properties are not clearly understood. The aim of this review is to highlight recent advances in CLA research related to experimental inflammatory bowel disease. In addition, two possible mechanisms of action (i.e. endoplasmic and nuclear) were discussed in detail in the context of enteric inflammatory disorders. Conjugated linoleic acid was first implicated in down-regulating the generation of inducible eicosanoids (i.e. PGE(2) and LTB(4)) involved in early micro-inflammatory events (endoplasmic). More recently, CLA has been shown to modulate the expression of genes regulated by peroxisome proliferator-activated receptors (PPARs; nuclear). In pigs, prolonged dietary CLA treatment stimulated the expression of PPAR-gamma in the muscle. Thus, evidence supporting both mechanistic theories of CLA acting through eicosanoid synthesis and PPAR activity is available. The further understanding of the anti-inflammatory mechanisms of action of CLA may yield novel nutritional therapies for enteric inflammation.     

Influence of conjugated linoleic acid on the porcine immune response and morbidity: a randomized controlled trial

Background  

Conjugated linoleic acid (CLA) has diverse influences on the immune response in different experimental models. In the present study we investigated the effect of CLA feeding on inflammatory and immune responses in a piglet model. We studied the duration of this effect and possible detrimental effects of CLA feeding. After 12 weeks of CLA and control supplementation and washout, animals were sacrificed and parenchymal organs were histologically examined.     

Dietary conjugated linoleic acid consumption during pregnancy and lactation influences growth and tissue composition in weaned pigs

We evaluated the effects of conjugated linoleic acid (CLA) on growth performance, tissue fatty acid composition and ex vivo lipogenic enzyme activity in piglets (n = 40) reared on sows fed diets supplemented with CLA or linoleic acid (LA). Weaned offspring of both sow groups were offered either a CLA- or LA-enriched starter diet for 35 d. The starter diets were formulated to contain 2 g CLA (containing 58.9 g CLA/100 g total fatty acids) or LA per 100 g feed. All piglets were slaughtered at 70 d of age and tissue samples of the back fat, omental fat and longissimus dorsi were collected. Irrespective of the dietary fat supplied in the starter period, piglets reared on the CLA sows had greater final body and warm carcass weights (P: < 0.01), and greater feed intake (P: = 0.02) than piglets reared on the LA sows. The dietary effect on the fatty acid composition was similar for the adipose and muscle tissues. Compared with the LA-enriched diets, CLA increased the level of total saturated fatty acids (P: < 0.05), whereas that of monounsaturated fatty acids was decreased (P: < 0.05). Dietary CLA increased glucose-6-phosphate dehydrogenase (P: < 0.01) and malic enzyme activities (P: < 0.06) in the fat tissues, but did not affect fatty acid synthase activity. The shift toward a higher deposition of saturated fatty acids and a lower deposition of monounsaturated fatty acids is the result of down-regulation of Delta9-desaturase activity that was induced by CLA rather than an altered rate of de novo synthesis.     

共轭亚油酸营养再分配作用及其安全性

共轭亚油酸(CLA)是一组具有共轭不饱和双键的亚油酸的位置和结构异构体,具有降脂增肌、促进生长、抗癌、抗动脉粥样硬化及调节免疫等生理功能。本文总结了CLA营养再分配活性及其安全性评价的研究成果,从分子药理水平,分析了CLA的作用机制与作用方式。     

Antimutagenic and some other effects of conjugated linoleic acid

Conjugated linoleic acid (CLA) is a collective term for positional and geometric isomers of octadecadienoic acid in which the double bonds are conjugated, i.e. contiguous. CLA was identified as a component of milk and dairy products over 20 years ago. It is formed as an intermediate in the course of the conversion of linoleic acid to oleic acid in the rumen. The predominant naturally occurring isomer is the cis-9, trans-11 modification. Treatment of linoleic acid-rich oils such as safflower oil, soybean oil, or maize oil with base and heat will result in the formation of CLA. Two isomers predominate in the synthetic preparation, c9,t11 and t10,c12. CLA has been shown to inhibit chemically-induced skin, stomach, mammary or colon tumours in mice and rats. The inhibition of mammary tumours in rats is effective regardless of type of carcinogen or type or amount of dietary fat. CLA has also been shown to inhibit cholesterol-induced atherosclerosis in rabbits. When young animals (mice, pigs) are placed on CLA-containing diets after weaning they accumulate more body protein and less fat. Since CLA is derived from the milk of ruminant animals and is found primarily in their meat and in products derived from their milk there is a concerted world-wide effort to increase CLA content of milk by dietary means. Its effect on growth (less fat, more protein) is also a subject of active research. The mechanisms underlying the effects of CLA are still moot.     

Bioconversion of vaccenic acid to conjugated linoleic acid in humans

BACKGROUND: Vaccenic acid (11-trans octadecenoic acid; VA), a major trans fatty acid in the fat of ruminants, is produced in the rumen and converted in tissues to rumenic acid (9-cis, 11-trans octadecenoic acid; RA), an isomer of conjugated linoleic acid, by Delta(9)-desaturase. There are indications that this conversion also occurs in humans. OBJECTIVE: The aim of this controlled intervention was to study the conversion of VA to RA in humans after consumption of diets with increasing amounts of VA. DESIGN: Thirty healthy subjects consumed a baseline diet rich in oleic acid for 2 wk. The subjects were then divided into 3 groups (n = 10 per group) and provided a diet containing 1.5, 3.0, or 4.5 g VA/d for 9 d. All diets contained equal amounts of macronutrients and differed only in their fatty acid compositions. The fats were mixed into conventional foods, and nearly all food was provided during the study. RESULTS: The proportion of VA in serum total fatty acids increased 94%, 307%, and 620% above baseline with the 1.5-, 3.0-, and 4.5-g diets, respectively. This was associated with a linear increase in the proportion of RA. The conversion rate was 19% on average, with significant interindividual differences with all 3 intakes of VA. The urinary excretion of 8-iso-prostaglandin F(2alpha) increased in all groups (P < 0.001). CONCLUSIONS: The results quantify the desaturation of VA to RA in humans. Conversion is likely to contribute significantly to the amount of RA available to the body, and dietary intakes of VA should thus be taken into account when predicting RA status.     

Dietary conjugated linoleic acids and lipid source alter fatty acid composition of juvenile yellow perch, Perca flavescens

A study was conducted to examine the effects of dietary conjugated linoleic acids (CLA; 0, 0.5 or 1.0 g/100 g total CLA) and lipid source (menhaden oil, soybean oil or a 1:1 mixture of menhaden:soybean oil) on growth rates and fatty acid composition of yellow perch. Dietary treatments were fed to apparent satiation to triplicate groups of fish initially weighing 37.9 g/fish. At the end of the 9-wk feeding trial, no significant differences were detected in weight gain or feed intake among fish fed any of the dietary treatments. Dietary CLA, lipid source and/or their interaction significantly affected feed efficiency, total liver lipid concentration, and muscle and liver fatty acid concentrations. Feed efficiency (g gain/g feed) was significantly lower in fish fed diets containing soybean oil (0.51) compared with fish fed menhaden oil (0.58) or menhaden:soybean oil (0.60). Liver total lipid concentrations were significantly reduced in fish fed 0.5 and 1.0 g/100 g CLA compared with fish fed the diets containing no CLA and in fish fed menhaden oil compared with those fed soybean oil or a 1:1 mixture of menhaden:soybean oil. Total CLA levels increased in both liver and muscle as dietary CLA concentration increased, irrespective of lipid source. However, total CLA concentrations were significantly lower in liver and muscle of fish fed soybean oil. Total muscle CLA concentrations were 0, 1.26 and 2.92 g/100 g fatty acids in fish fed diets containing menhaden oil and 0, 0.5 and 1.0 g/100 g CLA, respectively. Mono- and polyunsaturated fatty acid (PUFA) concentrations were significantly lower in muscle and liver of fish fed CLA compared with fish fed the diets containing no CLA. In contrast, liver concentrations of saturated fatty acids, 14:0, 16:0 and 18:0, were significantly higher in fish fed 1.0 g/100 g CLA.     

Dietary conjugated linoleic acid alleviates nonalcoholic fatty liver disease in Zucker (fa/fa) rats

Nonalcoholic fatty liver disease (NAFLD) is the preferred term to describe the spectrum of liver damage ranging from hepatic steatosis to steatohepatitis, liver fibrosis, and cirrhosis, and it is emerging as the most common liver disease in industrialized countries. Thus, the discovery of food components that would ameliorate NAFLD is of interest. Conjugated linoleic acid (CLA), a mixture of positional and geometric isomers of linoleic acid, has attracted considerable attention because of its potentially beneficial biological effects both in vitro and in vivo. We tested whether dietary CLA protects Zucker (fa/fa) rats from hepatic injury. After 8 wk of feeding, hepatomegaly, hepatic triglyceride (TG) accumulation, and elevated hepatic injury markers in plasma were markedly alleviated in CLA-fed Zucker rats compared with linoleic acid-fed (control) rats. These effects were attributed in part to the enhanced hepatic activities of carnitine palmitoyltransferase, a key enzyme of fatty acid beta-oxidation, and microsomal TG transfer protein, an important factor for lipoprotein secretion due to the CLA diet. We previously reported that the severe hyperinsulinemia in control Zucker rats was attenuated in CLA-fed rats due to an enhanced level of plasma adiponectin, which improves insulin sensitivity. In the present study, the adiponectin concentration was increased and the mRNA expression of tumor necrosis factor-alpha, an inflammatory cytokine, was markedly suppressed in the liver of CLA-fed Zucker rats. We speculate that the enhanced level of liver adiponectin may prevent the development and progression of NAFLD in CLA-fed Zucker rats.