Effects of dietary conjugated linoleic acids on hepatic and muscle lipids in hybrid striped bass

Digestibility of Conventional and Novel Dietary Lipids in Channel Catfish Ictalurus punctatus

Lipid and fatty acid digestibility is presumably high in Channel Catfish, but data is lacking. We determined the lipid and fatty acid digestibility of traditional and alternative dietary lipids in Channel Catfish to inform lipid choice for commercial diets. Six diets contained 4% of different lipids: soybean oil (SBO), soybean oil containing conjugated linoleic acids (CLA-SBO), catfish offal oil (COO), flaxseed oil (FXO), menhaden fish oil (MFO) and poultry fat (PF). Diets were fed to Channel Catfish (150-200 g) maintained at 26.5 °C in each of six 110 L aquaria. Six hours post-prandial, feces were collected for analysis. Total lipid, crude protein and fatty acids of lyophilized feces were analyzed, and apparent digestibility coefficients (ADCs) were calculated. ADCs of lipid, saturated and monounsaturated fatty acids, linoleic acid and protein digestibility were similar among diets. CLA isomers (cis-9, trans-11 (84.1%) and trans-10, cis-12 (90%)) in the CLA-SBO diet were highly digestible. Oleic acid digestibility was highest in the PF diet. ADC was high for α-linolenic acid in the FXO diet, and for arachidonic acid and n-3 LC-PUFA in the MFO diet. Overall, total lipid digestibility was high, but ADCs of individual fatty acids differed by source.

Conjugated linoleic acid as a novel insecticide targeting the agricultural pest Leptinotarsa decemlineata

The Colorado Potato Beetle, Leptinotarsa decemlineata, is a major agricultural pest of solanaceous crops in the United States. Historically, a multitude of insecticides have been used to control problematic populations. Due to increasing resistance to insecticides, novel compounds and methodologies are warranted for the control of beetle populations. Mixed-isomer conjugated linoleic acid has been studied in-depth for its beneficial properties to mammalian systems. At the same time, studies have demonstrated that conjugated linoleic acid can manipulate fatty acid composition in non-mammalian systems, resulting in embryo mortality. Consequently, experiments were conducted to assess the effects of foliar-applied conjugated linoleic acid on larval growth, embryogenesis, and feeding preference in Colorado potato beetle. Both maternal and deterrent effects of dietary conjugated linoleic acid were assessed. Conjugated linoleic acid demonstrated desirable insecticidal properties, including increased larval mortality, slowed larval development, antifeedant effects, and decreased egg viability after maternal ingestion.

Conjugated linoleic acid alters growth performance, tissue lipid deposition, and fatty acid composition of darkbarbel catfish (Pelteobagrus vachelli)

Fatty liver syndrome is a prevalent problem of farmed fish. Conjugated linoleic acid (CLA) has received increased attention recently as a fat-reducing fatty acid to control fat deposition in mammals. Therefore, the aim of the present study was to determine whether dietary CLA can reduce tissue lipid content of darkbarbel catfish (Pelteobagrus vachelli) and whether decreased lipid content is partially due to alterations in lipid metabolism enzyme activities and fatty acid profiles. A 76-day feeding trial was conducted to investigate the effect of dietary CLA on the growth, tissue lipid deposition, and fatty acid composition of darkbarbel catfish. Five diets containing 0 % (control), 0.5 % (CLA0.5), 1 % (CLA1), 2 % (CLA2), and 3 % (CLA3) CLA levels were evaluated. Results showed that fish fed with 2-3 % CLA diets showed a significantly lower specific growth rate and feed conversion efficiency than those fed with the control diet. Dietary CLA decreased the lipid contents in the liver and intraperitoneal fat with the CLA levels from 1 to 3 %. Fish fed with 2-3 % CLA diets showed significantly higher lipoprotein lipase and hepatic triacylglycerol lipase activities in liver than those of fish fed with the control, and fish fed with 1-3 % CLA diets had significantly higher pancreatic triacylglycerol lipase activities in liver than those of fish fed with the control. Dietary CLA was incorporated into liver, intraperitoneal fat, and muscle lipids, with higher percentages observed in liver compared with other tissues. Liver CLA deposition was at the expense of monounsaturated fatty acids (MUFA). In contrast, CLA deposition appeared to be primarily at the expense of MUFA and n-3 polyunsaturated fatty acids (PUFA) in the intraperitoneal fat, whereas in muscle it was at the expense of n-3 PUFA. Our results suggested that CLA at a 1 % dose can reduce liver lipid content without eliciting any negative effect on growth rate in darkbarbel catfish. This lipid-lowering effect could be in part due to an increment in the activity of lipid metabolism enzymes and an extensive interconversion of fatty acids. Although CLA deposition in muscle (0.66-3.19 % of total fatty acids) are higher than presented in natural sources of CLA, EPA (C20:5n-3) in fish muscle appears simultaneously expendable, when the fish fed with 2-3 % CLA.

Effects of conjugated linoleic acid on growth, non-specific immunity, antioxidant capacity, lipid deposition and related gene expression in juvenile large yellow croaker (Larmichthys crocea) fed soyabean oil-based diets

The effects of conjugated linoleic acid (CLA) on growth performance, non-specific immunity, antioxidant capacity, lipid deposition and related gene expression were investigated in the large yellow croaker (Larmichthys crocea). Fish (7·56 (sem 0·60) g) were fed soyabean oil-based diets with graded levels of CLA (0, 0·42, 0·83, 1·70 %) for 70 d. Quantitative PCR was used to assess the effects of CLA on the transcription of inflammation- and fatty acid oxidation-related genes. Growth in fish fed the diet with 0·42 % CLA was significantly higher. Also, phagocytic index and respiratory burst activity were significantly higher in fish fed the diets containing 0·42 and 0·83 % CLA, respectively. Hepatic total antioxidative capacity and catalase activities increased significantly when CLA increased from 0 to 0·83 %, and then decreased with further increase of CLA. However, hepatic malondialdehyde content decreased significantly as dietary CLA increased. Lipid concentration in the whole body and muscle increased significantly with increasing dietary CLA. Transcription of genes related to inflammation (cyclo-oxygenase-2 and IL-β) in the liver and kidney and fatty acid oxidation (carnitine palmitoyl transferase I and acyl CoA oxidase) in the kidney decreased significantly as dietary CLA increased. PPARα and acyl CoA oxidase expression in the liver decreased significantly as CLA increased from 0·42 to 1·70 %. These results strongly suggest that dietary CLA could significantly affect growth performance, non-specific immunity, antioxidant capacity, lipid deposition and transcription of inflammation- and fatty acid oxidation-related genes of the large yellow croaker. This may contribute to our understanding of the mechanisms related to the physiological effects of dietary CLA in fish.

trans-10,cis-12 conjugated linoleic acid improved growth performance, reduced lipid deposition and influenced CPT I kinetic constants of juvenile Synechogobius hasta

trans-10,cis-12 (t10c12) Conjugated linoleic acid (CLA) reduced body lipid deposition in various experimental animals, but the mechanisms involved were still emerging. Carnitine palmitoyltransferase I (CPT I) catalyzes an important regulatory step in lipid metabolism. At present, no studies, to our knowledge, have evaluated the kinetic constants influenced by dietary CLA in fish. In the present study, we tested the hypothesis that changes in body lipid content in fish as a response to dietary t10c12 CLA was related to the change of CPT I kinetic constants [Michaelis constant (K m), maximal velocity and catalytic efficiency for carnitine and palmitoyl-CoA]. Juvenile Synechogobius hasta were fed three experimental diets with fish oil replaced with 0 (control), 1, or 2 % t10c12 CLA for 8 weeks. Weight gain, specific growth rate and protein efficiency rate increased with dietary t10c12 CLA level. Dietary t10c12 CLA addition significantly reduced lipid contents both in liver and muscle. Dietary CLA addition also improved CPT I activities in muscle but did not significantly influence hepatic CPT I activity. CPT I kinetic parameters (K m, V max and catalytic efficiency) were significantly influenced by t10c12 CLA. CPT I catalytic efficiencies with carnitine and palmitoyl-CoA as substrates were higher in muscle and liver of fish fed increasing t10c12 CLA. For the first time, the findings demonstrated effect of dietary CLA addition on CPT I kinetics in fish and supported our starting hypothesis that dietary t10c12 CLA addition induced alterations in CPT I kinetic constants of muscle and liver. Increased CPT I catalytic efficiency might be the main reason for reduced lipid deposition in these tissues by dietary t10c12 CLA supplementation.

Influence of dietary conjugated linoleic acid on growth, fatty acid composition and hepatic lipogenesis in large yellow croaker (Pseudosciaena crocea R.)

We examined the effects of conjugated linoleic acid (CLA) on growth, fatty acid composition and enzyme activity of fatty acid oxidation in the liver of large yellow croaker. We divided 1600 fish (average initial weight 150 g) into 4 groups and reared them in 8 cages. Four dietary treatments were formulated to contain 0%, 1%, 2% and 4% (w/w) CLA, respectively. The fish were fed for 10 weeks ad libitum twice daily. We found that the dietary CLA had no effect on growth, biometric parameters and whole body proximate (P>0.05), but showed some significant effects on the fatty acid composition in both muscle and the liver. The activities of lipogenic enzymes were slightly depressed in fish fed with increasing levels of CLA when compared with control (P>0.05). Dietary CLA supplementation had no effects on liver lipid content, but significantly increased the contents of saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA) (P<0.05) and decreased monounsaturated fatty acid (MUFA) content in both muscle and the liver. Dietary CLA inclusion resulted in significant increases of the biologically active cis-9, trans-11 and trans-10, cis-12 isomers in both tissues (P<0.05). The total accumulation of CLA was higher in the liver (3.83%, w/w) than in muscle (3.77%, w/w) when fed with 4% (w/w) CLA. This study demonstrates that large yellow croakers are capable of absorbing and depositing CLA and long-chain n-3 PUFA in the liver and muscle, showing that this species fed with CLA could be an important human food source for these healthful fatty acids.

Conjugated linoleic acid affects lipid composition, metabolism, and gene expression in gilthead sea bream (Sparus aurata L)

To maximize growth, farmed fish are fed high-fat diets, which can lead to high tissue lipid concentrations that have an impact on quality. The intake of conjugated linoleic acid (CLA) reduces body fat in mammals and this study was undertaken to determine the effects of dietary CLA on growth, composition, and postprandial metabolic variables in sea bream. Fish were fed 3 diets containing 48 g/100 g protein and 24 g/100 g fat, including fish oil supplemented with 0 (control), 2, or 4% CLA for 12 wk. Feed intake, specific growth rate, total body fat, and circulating somatolactin concentration were lower in fish fed CLA than in controls. Feed efficiency was greater in fish fed 2% CLA than in controls. Liver triglyceride concentrations were higher in fish fed 4% CLA and muscle triglyceride concentrations were lower in fish fed both CLA diets than in controls. Hepatic fatty acyl desaturase and elongase mRNA levels in fish fed CLA were lower than in controls. Metabolic differences between controls and CLA-fed fish were observed at 6 h but not at 24 h after the last meal, including lower postprandial circulating triglyceride concentrations, higher hepatic acyl-CoA-oxidase, and lower L-3-hydroxyacyl-CoA dehydrogenase activities in CLA-fed fish than in controls. Dietary CLA did not affect enzymes involved in lipogenesis including hepatic fatty acid synthase and malic enzyme, but it decreased glucose 6-phosphate dehydrogenase activity at 24 h, but not at 6 h after feeding. The data suggest that CLA intake in sea bream has little effect on hepatic lipogenesis, channels dietary lipid from adipose tissue to the liver, and switches hepatic mitochondrial to peroxisomal beta-oxidation.

Conjugated linoleic acid and its effects on animal products and health in single-stomached animals

Conjugated linoleic acids (CLA) have been shown to have anti-carcinogenic, anti-obesity, anti-atherogenic and immunomodulatory functions. The basis for these effects has not been fully explained, but probably involves effects of CLA on eicosanoid metabolism, cytokine production and\or gene expression. The predominant isomer (85–90%) in the natural sources of CLA has thecis-9, trans-11 configuration. As interest in CLA grew and synthetic forms became available, the number of studies examining the effects of dietary CLA in rodents, human subjects and livestock has increased greatly. In the late 1990 s the observation that CLA had anti-obesity effects was reported. Subsequently, it was determined that this effect in mice could be attributed to thetrans-10, cw-12 isomer that, along with thecis-9,trans-11 isomer, predominates in the synthetic forms of CLA. The santi-obesity response varies in magnitude depending on species, and has not been consistent in non-rodents. In general, the response is greatest in mice and less or absent in other species. The basis for this lack of consistency is not clear and is unlikely to be accounted for by differences in the source of CLA. In the pig variation in body fat of animals may account for differences in responsiveness. There is no direct evidence of an anti-carcinogenic effect of CLA in human subjects or livestock. Indirect evidence fromin vitrostudies with cell lines, as well as epidemiological studies, suggest that CLA may be relevant as a natural anti-carcinogen. The immunomodulatory effects of CLA may have application in livestock production as an alternative to the use of feed antibiotics, or as a means of improving the response to vaccination and conferring disease resistance. The recent literature on the effects of CLA, with emphasis on its anti-obesity effects, is reviewed.

Conjugated linoleic acid in diets for large-size rainbow trout (Oncorhynchus mykiss): effects on growth, chemical composition and sensory attributes

The effects of graded levels (0 %, 0·5 %, 0·75 and 1 %) of dietary conjugated linoleic acid (CLA) were assessed on 97 g rainbow trout. Fish were fed to satiation twice a day for 12 weeks. At the end of the experiment, all groups of fish weighed more than 250 g and no significant differences were detected in growth performance, feed conversion, nutrient or energy utilisation or body composition between treatments. A decrease in liver lipid content resulted from including CLA and was accompanied by a reduction in malic enzyme activity. The muscle saturated acid and PUFA content did not vary between dietary treatments, despite the increasing concentration of stearic acid and CLA. In the liver, however, both fractions increased significantly with dietary CLA. Moreover, the MUFA decreased significantly in both muscle and liver. CLA was incorporated into tissue lipids, with levels in flesh (2·1–4·2 %) being 2-fold higher than in liver (0·8–1·9 %). In muscle, the percentage of cis-9, trans-11 isomer ranged from 39·5 % to 41·8 % and that of trans-10, cis-12 isomer from 31·4 % to 33·4 % of total CLA. The incorporation of CLA isomers in the liver varied with dietary treatment, and the cis-9, trans-11 isomer seemed to be more efficiently incorporated than trans-10, cis-12. Sensory data indicated slight-to-moderate differences between the trout fed with and without CLA. The present results suggest that 250 g rainbow trout can incorporate CLA in both muscle and liver, contributing to the production of a functional food.

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.

Influence of dietary oil content and conjugated linoleic acid (CLA) on lipid metabolism enzyme activities and gene expression in tissues of Atlantic salmon (Salmo salar L.)

The overall objective is to test the hypothesis that conjugated linoleic acid (CLA) has beneficial effects in Atlantic salmon as a result of affecting lipid and FA metabolism. The specific aims of the present study were to determine the effects of CLA on some key pathways of FA metabolism, including FA oxidation and highly unsaturated FA (HUFA) synthesis. Salmon smolts were fed diets containing two levels of fish oil (low, approximately 17%, and high, approximately 34%) containing three levels of CLA (a 1:1 mixture of cis-9,trans-11 and trans-10,cis-12 at 0, 1, and 2% of diet) for 3 mon. The effects of dietary CLA on HUFA synthesis and beta-oxidation were measured, and the expression of key genes in the FA oxidation and HUFA synthesis pathways, and the potentially important transcription factors peroxisome proliferators activated receptors (PPAR), were determined in selected tissues. Liver HUFA synthesis and desaturase gene expression was increased by dietary CLA and decreased by high dietary oil content. Carnitine palmitoyltransferase-I (CPT-I) activity and gene expression were generally increased by CLA in muscle tissues although they were relatively unaffected by dietary oil content. In general CPT-I activity or gene expression was not correlated with P-oxidation. Dietary CLA tended to increase PPARalpha and beta gene expression in both liver and muscle tissues, and PPARgamma in liver. In summary, gene expression and activity of the FA pathways were altered in response to dietary CLA and/or oil content, with data suggesting that PPAR are also regulated in response to CLA. Correlations were observed between dietary CLA, liver HUFA synthesis and desaturase gene expression, and liver PPARalpha expression, and also between dietary CLA, CPT-I expression and activity, and PPARalpha expression in muscle tissues. In conclusion, this study suggests that dietary CLA has effects on FA metabolism in Atlantic salmon and on PPAR transcription factors. However, further work is required to assess the potential of CLA as a dietary supplement, and the role of PPAR in the regulation of lipid metabolism in fish.

Effect of dietary conjugated linoleic acid (CLA) on lipid composition, metabolism and gene expression in Atlantic salmon (Salmo salar) tissues

Dietary conjugated linoleic acid (CLA) affects fat deposition and lipid metabolism in mammals, including livestock. To determine CLA effects in Atlantic salmon (Salmo salar), a major farmed fish species, fish were fed for 12 weeks on diets containing fish oil or fish oil with 2% and 4% CLA supplementation. Fatty acid composition of the tissues showed deposition of CLA with accumulation being 2 to 3 fold higher in muscle than in liver. CLA had no effect on feed conversion efficiency or growth of the fish but there was a decreased lipid content and increased protein content after 4% CLA feeding. Thus, the protein:lipid ratio in whole fish was increased in fish fed 4% CLA and triacylglycerol in liver was decreased. Liver beta-oxidation was increased whilst both red muscle beta-oxidation capacity and CPT1 activity was decreased by dietary CLA. Liver highly unsaturated fatty acid (HUFA) biosynthetic capacity was increased and the relative proportion of liver HUFA was marginally increased in salmon fed CLA. CLA had no effect on fatty acid Delta6 desaturase mRNA expression, but fatty acid elongase mRNA was increased in liver and intestine. In addition, the relative compositions of unsaturated and monounsaturated fatty acids changed after CLA feeding. CLA had no effect on PPARalpha or PPARgamma expression in liver or intestine, although PPARbeta2A expression was reduced in liver at 4% CLA feeding. CLA did not affect hepatic malic enzyme activity. Thus, overall, the effect of dietary CLA was to increase beta-oxidation in liver, to reduce levels of total body lipid and liver triacylglycerol, and to affect liver fatty acid composition, with increased elongase expression and HUFA biosynthetic capacity.

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.

Influence of dietary conjugated linoleic acid (CLA) on lipid and fatty acid composition in liver and flesh of Atlantic salmon (Salmo salar)

The aim of the present study was to determine the effects of conjugated linoleic acid (CLA) on lipid and fatty acid metabolism in Atlantic salmon. The overall objective being to test the hypotheses that CLA has beneficial effects in salmon including growth enhancement, improved flesh quality through decreased adiposity and lipid deposition thereby minimising detrimental effects of feeding high fat diets, and increased nutritional quality through increased levels of beneficial fatty acids including n-3 highly unsaturated fatty acids (HUFA) and CLA itself. Salmon smolts were fed diets containing two levels of fish oil (low, approximately 18% and high, approximately 34%) containing three levels of CLA (a 1:1 mixture of 9-cis,trans-11 and trans-10,cis-12. at 0, 1 and 2% of diet) for 3 months and the effects on growth performance, liver and muscle (flesh) lipid contents and class compositions, and fatty acid compositions determined. The diets were also specifically formulated to investigate whether the effects of CLA, if any, were more dependent upon absolute content of CLA in the diet (as percentage of total diet) or the relative level of CLA to other fatty acids. Dietary CLA in salmon smolts had no effect on growth parameters or biometric parameters. However, there was a clear trend of increased total lipid and triacylglycerol contents in both liver and flesh in fish fed CLA, particularly in fish fed the high oil diets. Finally, CLA was incorporated into tissue lipids, with levels in flesh being 2-fold higher than in liver, but importantly, incorporation in liver was at the expense of saturated and monounsaturated fatty acids whereas in flesh it was at the expense of n-3HUFA.

Protein and lipid sources affect cholesterol concentrations of juvenile Pacific white shrimp, Litopenaeus vannamei (Boone)

Two experiments were conducted to evaluate the effects of protein and lipid sources on cholesterol, AA, and fatty acid content, and on biological performance of juvenile Pacific white shrimp, Litopenaeus vannamei (Boone). In Exp. 1, seven isonitrogenous and isocaloric diets were prepared using fish meal; soybean meal; casein; fish meal + soybean meal; fish meal + casein; soybean meal + casein; and fish meal + soybean meal + casein. In Exp. 2, seven isonitrogenous and isocaloric diets were prepared using fish oil; soy oil; poultry fat; fish oil + soy oil; fish oil + poultry fat; soy oil + poultry fat; and fish oil + soy oil + poultry fat. Nine shrimp (average BW 570 mg) were stocked per 60-L tank, with three tanks per diet in each experiment. Shrimp were fed to apparent satiation twice daily for 28 d. Protein sources affected shrimp cholesterol, feed consumption, feed efficiency, protein consumption, protein efficiency ratio, and crude body fat (P < or = 0.05), but not weight gain, survival, hepatosomatic index, body protein, ash, and AA composition. Body (without hepatopancreas) cholesterol concentrations were the highest in shrimp fed the diet containing fish meal (0.81%), lowest for those fed the casein diet (0.64%), and intermediate in the other dietary treatment groups (range 0.71 to 0.74%). Lipid source also affected shrimp body cholesterol, body fatty acid profiles, and fatty acid profiles in the hepatopancreas (P < or = 0.05), but not growth performance, body protein, fat, ash, and cholesterol concentrations in the hepatopancreas. Shrimp fed the fish oil diet had the highest body cholesterol (0.75%), whereas those fed the soy oil or poultry fat diets were lowest (0.66 and 0.65%, respectively). Results indicate that by replacing fish meal and fish oil with soybean meal and soy oil, shrimp growth performance is not affected, but body cholesterol concentration is reduced.

Effects of specific conjugated linoleic acid isomers on growth characteristics in obese Zucker rats

Growing female obese Zucker (fa/fa) rats were treated (via intragastric gavage) for 21 d with either a (i) vehicle [corn oil; 0.9 g/kg body weight (BW)], (ii) CLA mixture [50:50; trans-10, cis-12 and cis-9, trans-11 CLA], (iii) cis-9,trans-11 CLA, or (iv) trans- 10, cis-12 CLA (CLA treatments at 1.5 g CLA/kg BW). Compared with controls, average daily gain (g/d) was reduced 24 and 44% by the CLA mixture and trans-10, cis-12 CLA, respectively. There was no treatment effect on average whole-body (minus heart and liver) composition (dry matter basis): fat (70.2%), protein (21.0%), and ash (4.3%). Compared with animals treated with cis-9,trans-11 CLA, obese Zucker rats treated with trans-10, cis-12 and the CLA mixture had 7.8% more carcass water. Treatment had no effect on heart or liver weights or on heart or liver weights as a percentage of body weight, but compared with the other treatments trans-10, cis-12 CLA increased liver lipid content by 33%. Hepatic lipid ratios of 16:1/16:0 and 18:1/18:0 (a proxy for delta9-desaturase capability) were not affected by treatment (0.1 and 0.6, respectively). Similar to previous reports, CLA increased hepatic lipid content and altered both liver and carcass FA composition (i.e., reduced arachidonic acid content), but the ability of CLA to manipulate body composition in obese Zucker rats remains questionable.

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.

Dietary conjugated linoleic acid alters hepatic lipid content and fatty acid composition in broiler chickens

We examined the effect of dietary conjugated linoleic acid (CLA) on growth performance and liver composition in broiler chickens. Day-old male broiler chicks were assigned to receive a diet supplemented with corn oil (5%; n = 48) or CLA (5%; n = 48) for 21 d. Broilers fed CLA weighed less and grew at slower rates than broilers fed corn oil. Feed intake and feed conversion were higher for the corn-oil group than for the CLA dietary group. Hepatic lipid and triacylglycerol concentrations were significantly reduced by dietary CLA. The proportions of saturated fatty acids (SFA) in liver lipids increased, whereas those of monounsaturated fatty acids (MUFA) decreased with CLA supplementation. Although the total concentration of polyunsaturated fatty acids (PUFA) did not change with dietary treatment, the concentration of linoleic acid as a percentage of total methylated fatty acids decreased, and that of linolenic add increased in broilers fed CLA. The concentration of CLA isomers in liver lipids increased substantially with CLA feeding. The relative proportion of the c9,t11 CLA isomer in hepatic lipids was much higher than that of the t10,c12 or t9,t11 CLA isomers. These studies provide evidence that feeding CLA to broilers results in substantial reduction in liver fat accumulation and promotes CLA incorporation into hepatic lipid pools.

Isomer-specific effects of conjugated linoleic acid (CLA) on adiposity and lipid metabolism

Isomers of conjugated linoleic acid (CLA), unsaturated fatty acids found in ruminant meats and dairy products, have been shown to reduce adiposity and alter lipid metabolism in animal, human, and cell culture studies. In particular, dietary CLA decreases body fat and increases lean body mass in certain rodents, chickens, and pigs, depending on the isomer, dose, and duration of treatment. However, the effects of CLA on human adiposity are conflicting because these studies have used different mixtures and levels of CLA isomers and diverse subject populations. Potential antiobesity mechanisms of CLA include decreased preadipocyte proliferation and differentiation into mature adipocytes, decreased fatty acid and triglyceride synthesis, and increased energy expenditure, lipolysis, and fatty acid oxidation. This review will address the current research on CLA's effects on human and animal adiposity and lipid metabolism as well as potential mechanism(s) responsible for CLA's antiobesity properties.

Effect of dietary conjugated linoleic acid on the growth rate of live birds and on the abdominal fat content and quality of broiler meat

Two experiments were conducted to investigate the influence of dietary conjugated linoleic acid (CLA) on the growth, body composition, abdominal fat accumulation, and meat quality in broilers. In Experiment 1, 50 broilers that were 3 wk old (total of 200 birds) were assigned to one of the four diets containing 0, 0.25, 0.5, or 1% CLA and were fed for 3 wk. In Experiment 2, 40 broilers that were 3 wk old (total of 120 birds) were assigned to one of the three diets containing 0, 2, or 3% CLA and fed for 5 wk. At the end of the 3-wk feeding trial, the average body weight of broilers for Experiment 1 was about 2.20 kg per bird for all treatments. For Experiment 2, after 5-wk feeding trial, the average body weights of birds were 4.04, 3.99, and 3.93 kg for the control, 2% CLA, and 3% CLA groups, respectively, with a non significant reduction in body weight as the levels of dietary CLA increased. There was no difference in abdominal fat weight, the total body fat, and protein content in broilers among the CLA treatments for Experiment 1. However, when the dietary CLA was increased to 2 or 3%, the total body fat content was reduced. The whole body fat content decreased from 14.2% in the control to 11.9 and 12.2% for 2 and 3% CLA, respectively. Dietary CLA at 2 and 3% levels influenced meat quality. After cooking, the breast meat from 2 or 3% dietary CLA treatment was harder and drier, and the color was a little darker than that of the control. These changes could be caused by the decreased unsaturated fatty acid content in meat after CLA feeding, which increased the melting point of the fat.

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.