Trans10,cis12-18:2 is a more potent inhibitor of de novo fatty acid synthesis and desaturation than cis9,trans11-18:2 in the mammary gland of lactating mice

To investigate the effects of 2 conjugated linoleic acid (CLA) isomers and trans11-18:1 (TVA) on de novo lipogenesis and desaturation in liver and mammary gland, lactating mice were fed diets containing 3% canola oil (control) or 2% canola oil plus 1% stearic acid (SA), TVA, cis9,trans11 CLA (c9t11), or trans10,cis12 CLA (t10c12). In mammary tissue, TVA and CLA isomers reduced mRNA for acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) compared with control, but only c9t11 and t10c12 reduced mammary ACC activity. Of the 2 CLA isomers, t10c12 caused a greater reduction in mammary ACC activity. Hepatic ACC or FAS activity and mRNA abundance were not affected by dietary treatments. Feeding TVA, c9t11, or t10c12 reduced mammary stearoyl-CoA desaturase 1 (SCD) mRNA and activity. Reduction was greater due to feeding t10c12 compared with c9t11. Hepatic SCD mRNA was not affected by dietary treatments, but both CLA isomers depressed hepatic SCD activity. Results indicated that t10c12 is a more potent inhibitor of mammary lipogenesis and desaturation than is c9t11. A net gain of 77 and 1690 micro g of c9t11 in liver and mammary tissue, respectively, was found in the TVA-fed group over the control and SA-fed group. However, reduced mammary SCD mRNA or activity due to feeding TVA may indicate a limited capacity for desaturation of dietary TVA to c9t11 in vivo.     

Effect of dietary conjugated linoleic acid on body composition and energy balance in broiler chickens

The effect of dietary conjugated linoleic acid (CLA) on body composition and energy metabolism was investigated in broiler chickens. Male broiler chicks were assigned to receive either a control diet (1 % sunflower oil) or a diet containing CLA (1 % of a 1:1 mixture of trans-10, cis-12 and cis-9, trans-11 isomers of octadecadienoic acid). The diets were fed ad libitum for 3 weeks and there were eight replicates per diet, each replicate including four chickens so that each treatment had thirty-two animals. The proportion of body fat was lower in the control group than in the CLA group. No significant differences as to the proportions of body water, ash and protein were observed. Feed and energy intake were significantly lower in CLA-fed birds. The percentage of ingested energy lost in excreta was higher after CLA feeding and heat expenditure as a percentage of ingested energy was lower in the CLA-fed group. The CLA-fed group showed a higher percentage of SFA and lower percentages of MUFA and PUFA in carcass fat. It is concluded that CLA stimulated de novo fatty acid synthesis and lowered desaturase activity.     

The deposition of conjugated linoleic acids in eggs of laying hens fed diets varying in fat level and fatty acid profile

The objective of this study was to investigate the incorporation of conjugated linoleic acid (CLA) into eggs and its effect on the fatty acid metabolism when layers are fed diets with different fat sources and fat levels. Layers were fed either a low fat diet (LF) or one of three high fat diets based on soybean oil (SB), animal fat (AF) or flaxseed oil (FSO). CLA was added at a concentration of 1 g/100 g feed from two different CLA premixes with a different CLA profile. For the trial, 144 laying hens were allocated to 12 treatments (4 basal fat sources x 3 CLA treatments) with 3 replicates of 4 hens each. No significant differences were observed in feed intake, egg weight, feed conversion or laying rate between chickens fed control and CLA-supplemented diets. Differences in yolk fat, cholesterol or yolk color were not clearly related to the dietary CLA. However, the supplementation of CLA to the diets had clear effects on the fatty acid composition, i.e., a decrease in monounsaturated fatty acids (MUFA) and an increase in saturated fatty acids (SFA) was observed, whereas the polyunsaturated fatty acids (PUFA) content were essentially unaffected. The results suggest that CLA may influence the activity of the desaturases to a different extent in the synthesis of (n-6) and (n-3) long-chain fatty acids. These effects of CLA depend on the level of (n-6) and (n-3) fatty acids available in the feed. The apparent deposition rate (%) is clearly higher for the c9, t11 isomer than for the t10, c12 isomer. Adding CLA to layers diets rich in (n-3) fatty acids produces eggs that could promote the health of the consumer in terms of a higher intake of (n-3) fatty acids and CLA.     

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.     

Conjugated linoleic acid differentially modifies fatty acid composition in subcellular fractions of muscle and adipose tissue but not adiposity of postweaning pigs

This study examined the interaction between conjugated linoleic acid (CLA) and dietary fat type on the enrichment of subcellular fractions, the Delta(9) desaturase index and adiposity in pigs. Early weaned piglets (n = 6/group) were fed for 35 d diets supplemented with 15 g/100 g diet beef tallow or corn oil, or 12 g/100 g tallow or corn oil plus 3 g CLA. There were no effects of dietary fat or CLA on the mass of dissected skin, bone, muscle or adipose tissue of the 7th to 9th thoracic rib sections. Medial subcutaneous adipose tissue of pigs fed tallow had smaller adipocytes than that of pigs fed corn oil. The lateral subcutaneous site was unaffected by dietary fat type. Microsomes accumulated <50% the concentration of trans-10,cis-12, cis-11,trans-13, and cis-9,trans-11 CLA as membrane and nonmembrane fractions of adipose tissue and longissimus muscle. There was no evidence of preferential incorporation of any CLA isomer into any of the subcellular fractions. Addition of CLA to the diets reduced adipose tissue nonmembrane monounsaturated fatty acids (MUFA; g/100 g total fatty acids) by 15% in corn oil-fed pigs and by 19% in tallow-fed pigs. Total saturated fatty acids (SFA) were increased by CLA commensurately in this lipid fraction. This resulted in a reduced Delta(9) desaturase index [MUFA/(SFA + MUFA)] in the nonmembrane lipid fraction of pigs fed either the corn oil or tallow diets. Thus, in spite of marked effects on fatty acid composition and the Delta(9) desaturase index, CLA had no effect on adiposity in early weaned piglets fed high fat diets.     

Combined effects of dietary conjugated linoleic acid and sesamin triacylglycerol and ketone body production in rat liver

The effects of a combination of dietary conjugated linoleic acid (CLA) supplemented with sesamin on hepatic ketogenesis and triacylglycerol secretion were compared using the livers of rats fed diets containing 1% CLA or linoleic acid (LA) in combination with 0.2% sesamin for 14 d, respectively. The feeding of CLA, as compared to LA, caused a significant reduction in the weight of perirenal adipose tissue but not that of epididymal adipose tissue, and affected neither growth parameters nor hepatic lipid concentration. Hepatic production of ketone bodies was consistently higher in rats fed CLA than in those fed LA, while triacylglycerol secretion was reversed. No significant difference was noted in the hepatic secretion of cholesterol among the groups. Although there was no effect of the dietary combination of CLA with sesamin on adipose tissue weight, hepatic lipid parameters and ketone body production were observed: i.e., triacylglycerol secretion tended to be reduced. These results suggest that the dietary combination of CLA with sesamin may be an effective approach for lowering serum triacylglycerol levels. The decreased hepatic secretion of triacylglycerol is, in part, due to enhanced fatty acid oxidation in the liver.     

Effects of dietary conjugated linoleic acid on fatty acid composition and cholesterol content of hen egg yolks

The main objectives of the present study were to determine the effect of dietary conjugated linoleic acid (CLA) isomers on the fatty acid composition and cholesterol content of egg-yolk lipids. Forty-five 25-week-old laying hens were randomly distributed into five groups of nine hens each and maintained in individual laying cages, throughout 12 weeks of the experiment. They were assigned to the five treatments that consisted of commercial layer diets containing 0, 5, 10, 15 or 20 g pure CLA/kg. Feed intake of hens varied little and insignificantly. Egg mass was uniformly lower (P<0.05) in the hens fed the CLA-enriched diets. Feed conversion efficiency, when expressed per kg eggs, was impaired (P<0.05), although without obvious relation to the dietary CLA concentration. Feeding the CLA-enriched diets resulted in gradually increasing deposition of CLA isomers (P<0.01) in egg-yolk lipids. Saturated fatty acids were increased (P<0.01) and monounsaturated fatty acids decreased (P<0.01). Polyunsaturated fatty acids (PUFA), when expressed as non-CLA PUFA, were also significantly decreased (P<0.01). The most striking effects (P<0.01) were observed for palmitic (16 : 0) and stearic (18 : 0) acids, which increased from 23.6 to 34 % and from 7.8 to 18 %, respectively. On the other hand, oleic acid (18 : 1n-9) decreased from 45.8 to 24.3 %. Among non-CLA PUFA, linoleic (18 : 2n-6) and alpha-linolenic (18 : 3n-3) acids were strongly (P<0.01) decreased, from 14.2 to 7.7 % and from 1.3 to 0.3 %, respectively. The same was true for arachidonic (20:4n-6) and docosahexaenoic (22 : 6n-3) acids. The cholesterol content of egg yolks, when expressed in mg/g yolk, was not affected by the dietary CLA concentrations. In conclusion, unless the adverse effects of CLA feeding to laying hens on the fatty acid profile of egg yolks are eliminated, the CLA-enriched eggs cannot be considered functional food products.     

Eicosapentaenoic acid and 3,10 dithia stearic acid inhibit the desaturation of trans-vaccenic acid into cis-9, trans-11-conjugated linoleic acid through different pathways in Caco-2 and T84 cells

Stearoyl-CoA desaturase (SCD) is a key enzyme that determines the composition and metabolic fate of ingested fatty acids, in particular the conversion of trans-vaccenic acid (TVA) to conjugated linoleic acid (CLA). The present study addressed the hypothesis that intestinal TVA absorption and biotransformation into CLA can be modulated by EPA and 3,10-dithia stearic acid (DSA) via altered SCD mRNA levels and desaturation indices (cis-9, trans-11-CLA:TVA and oleic acid:stearic acid ratios) in Caco-2 and T84 cells, two well-established in vitro models of the human intestinal epithelium. The study determined the effect of acute (3 h with 0.3 mm-EPA or 0.3 mm-DSA) and acute-on-chronic (1 week with 0.03 mm-EPA or -DSA, followed by respectively, 0.3 mm-EPA or -DSA for 3 h) treatments. In both cell lines, acute EPA treatment did not alter SCD desaturation indices, whereas the acute-on-chronic treatment affected these surrogate markers of SCD activity. This was associated with reduced sterol regulatory-element binding protein-1c and SCD mRNA levels. In contrast, acute and acute-on-chronic DSA treatments significantly reduced SCD desaturation indices without affecting SCD mRNA levels in Caco-2 cells. The present study on intestinal cells shows that the conversion rate of TVA to c9, t11-CLA is affected by other fatty acids present in the diet such as EPA, confirming previous observations in hepatic and mammary cell models.     

Effect of dietary fat and vitamin E on mouse lung lipids.

To examine the effect of dietary fat on lung lipids, male weanling mice (CD-1 strain) were fed purified diets containing 5% stripped lard or corn oil and kept in chambers supplied with air filtered free of airborne bacteria. Vitamin E was fed at 0, 10.5 or 105 mg dl-alpha-tocopheryl acetate/kg diet. Dietary fat and vitamin E (0 or 10.5 mg/kg) had no significant effects on the lung levels of triacylglycerol (TG) or phospholipid (PL) molecular species through 4 weeks of intake. Alterations in lung fatty acid composition were followed through 6 weeks of intake at 0, 10.5 and 105 mg vitamin E/kg diet. Vitamin E, at all levels of supplementation, had no significant effect on mouse lung fatty acid composition. Saturated fatty acids of the lung also showed little alteration by diet, but feeding the lard diet significantly elevated oleic and palmitoleic acids. In mice fed the corn oil diet the levels of linoleic acid (18:2) were twice those of lard-fed mice, and arachidonic acid (20:4) was elevated by 15.8%. The diet elevated the mean peroxidizability index (PI) on lung tissue in corn oil-fed mice.     

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.     

A diet rich in conjugated linoleic acid and butter increases lipid peroxidation but does not affect atherosclerotic, inflammatory, or diabetic risk markers in healthy young men

Intake of conjugated linoleic acid (CLA) has been demonstrated to beneficially affect risk markers of atherosclerosis and diabetes in rats. CLA is naturally found in milk fat, especially from cows fed a diet high in oleic acid, and increased CLA intake can occur concomitantly with increased milk fat intake. Our objective was to investigate the effect of CLA as part of a diet rich in butter as a source of milk fat on risk markers of atherosclerosis, inflammation, diabetes type II, and lipid peroxidation. A total of 38 healthy young men were given a diet with 115 g/d of CLA-rich fat (5.5 g/d CLA oil, a mixture of 39.4% cis9, trans11 and 38.5% trans10, cis12) or of control fat with a low content of CLA in a 5-wk double-blind, randomized, parallel intervention study. We collected blood and urine before and after the intervention. The fatty acid composition of plasma triacylglycerol, cholesterol esters, and phospholipids reflected that of the intervention diets. The CLA diet resulted in increased lipid peroxidation measured as an 83% higher 8-iso-prostaglandin F2alpha concentration compared with the control, P < 0.0001. We observed no other significant differences in the effect of the interventions diets. In conclusion, when given as part of a diet rich in butter, a mixture of CLA isomers increased lipid peroxidation but did not affect risk markers of cardiovascular disease, inflammation, or fasting insulin and glucose concentrations.     

Effects of conjugated linoleic acid on serum leptin concentration, body-fat accumulation, and beta-oxidation of fatty acid in OLETF rats

We investigated the efficacy of a 4-wk supplementation of conjugated linoleic acid (CLA) as free fatty acid (FFA) or triacylglycerol (TG) on serum leptin concentration, body-fat accumulation, and mitochondrial beta-oxidation in Otsuka Long-Evans Tokushima Fatty (OLETF) rats. A significant reduction of serum leptin concentration (42%) and a decrease in the wet weights of perirenal, epididymal, and omental/visceral-adipose tissue in TG-CLA and FFA-CLA groups were found in comparison with the OLETF control group. Both forms of CLA supplementation produced a 5.2% decrease in body weight compared with the control even though food intake was similar in the OLETF groups. Moreover, both forms of CLA enhanced carnitine-palmitoyltransferase activity in brown adipose tissue, perirenal adipose tissue, red gastrocnemius muscle, and liver in comparison with the OLETF control group. Serum concentrations of non-esterified fatty acid and TG also were reduced in rats fed diets supplemented with TG-CLA and FFA-CLA.     

Effects of conjugated linoleic acid on skeletal muscle triacylglycerol metabolism in hamsters

OBJECTIVE: The present work evaluated the effects of conjugated linoleic acid (CLA) on various aspects of triacylglycerol metabolism in skeletal muscle to determine the potential involvement of this tissue in the effect of CLA to decrease body fat. METHODS: Animals were randomized to three groups that were fed atherogenic diets that provided different amounts of trans-10,cis-12 CLA (0%, 0.5%, or 1%) for 6 wk. Muscle triacylglycerol, protein, water, glycogen, and DNA contents and fatty acid profile in triacylglycerols were analyzed. Lipoprotein lipase and carnitine palmitoyltransferase-I (CPT-I) activities were assessed. Triacylglycerol, glucose, and insulin concentrations were evaluated in serum. RESULTS: The high dose of CLA increased food efficiency and gastrocnemius muscle weight. CLA feeding resulted in decreased muscle triacylglycerol content without changes in protein, water, glycogen, and DNA contents or in cell size (protein/DNA ratio) and produced decreased lipoprotein lipase activity and increased CPT-I activity. No differences were found between CLA doses. CLA feeding led to the saturation of stored triacylglycerols. CONCLUSIONS: Decreased fatty acid uptake and increased fatty acid oxidation can contribute to the decreased muscle triacylglycerol content observed in hamsters fed the CLA diets. The increase in muscle fatty acid beta-oxidation might ultimately prevent storage of triacylglycerols in adipose tissue. Nevertheless, the lack of matching of lipoprotein lipase and CPT-I modifications makes it difficult to ensure that skeletal muscle is responsible, at least in part, for the effect of CLA on decreasing body fat; thus, further research is needed.     

Effects of conjugated linoleic acid on growth performance, feed conversion efficiency, and subsequent carcass quality in broiler chickens

The effect of dietary conjugated linoleic acid isomers (CLA) on growth performance, carcass composition, fatty acid composition of adipose and muscle tissues, and serum lipoproteins was investigated in broiler chickens. A total of 160 (eighty male and eighty female) chickens were allocated to four dietary treatments (0.0, 0.5, 1.0, and 1.5 % CLA) and fed a standard starter diet from 8 to 21 d, and a grower-finisher diet from 22-42 d. When determined for the total period 8-42 d, feed intake and body weight gains of broiler chickens were significantly reduced (from 3.31 to 3.12 kg and from 1615 to 1435 g respectively; P < 0.05), particularly at the 1.5 % dietary CLA level. Feed conversion efficiency and carcass yield values showed no significant effects of dietary CLA. Abdominal fat deposition was significantly reduced (from 2.68 to 1.78 %; P < 0.05), the relative proportion of breast muscles was unaffected, and that of leg muscles significantly increased (from 19.0 to 20.6 %; P < 0.05). The concentration of CLA isomers (% of total methyl esters of fatty acids) increased linearly in tissue samples from broilers fed 0.5, 1.0, and 1.5 % dietary CLA. The relative proportions of saturated fatty acids (16:0, 18:0) were significantly (P < 0.01) increased, and those of monounsaturated (16:1, 18:1) and polyunsaturated fatty acids (18:2, 20:4 in muscle tissues) significantly (P < 0.05) reduced. Total serum cholesterol concentrations reached a maximum in broilers fed 1.0 % CLA and then decreased slightly (from 141.73 to 136.47 mg/dl; P < 0.01). The same was true also for HDL-cholesterol (from 113.58 to 109.97 mg/dl; The HDL cholesterol:total cholesterol ratio and serum triacylglycerol concentration was unaffected. In conclusion, feeding CLA to broiler chickens resulted in substantial incorporation of CLA isomers into their tissue lipids, thus providing a potential CLA-rich source for human consumption.     

Metabolic effects of dietary conjugated linoleic acid (CLA) isomers in rats

To know the effect of individual conjugated linoleic acid (CLA) isomers on lipid metabolism, male rats were fed diets containing either linoleic acid (LA, a control fatty acid), CLA containing mainly 9c,11t-isomer, 10t,12c-isomer (at the 0.8% level) or an equivalent mixture of these isomers (at the 0.4% level) for 26 days. Although there were no differences in food intake and body weight gain among the groups, the food efficiency was low in rats fed the CLA containing 10t,12c-isomer in comparison with those fed 9c,11t-CLA. The weight of white (epididymal and perirenal) adipose tissues decreased in all CLA groups, while that of brown adipose tissue increased in rats fed 10t,12c-CLA, the difference between 9c,11t- and 10t,12c-isomers being significant. The concentration of serum total cholesterol, triacylglycerol and phospholipid tended to be lower in rats fed CLA preparations containing 10t,12c-CLA, while there was a trend toward an increasing concentration of serum HDL-cholesterol in all CLA groups. The rate of fatty acid β-oxidation in the liver peroxisomes was slightly higher in rats fed CLA than in those fed LA, and the activity of mitchondrial carnitine parmitoyltranceferase (CPT) in the CLA-mix group significantly increased compared to the LA group. The effect of CLA on the concentration of spleen and serum IgE, IgG and IgA level was variable. No CLA effect was observed on the concentration of serum leptin and TNF-. Thus, individual isomers of CLA may have different effects on some metabolic parameters in rats. The results also suggested a probable interaction of different isomers on lipid metabolism.     

Dietary conjugated linoleic acids promote fatty streak formation in the C57BL/6 mouse atherosclerosis model.

Conjugated linoleic acids (CLA) are positional isomers of linoleic acid which have been suggested by some to possess antiatherosclerotic properties. To test this hypothesis, three groups of twenty C57BL/6 mice were fed on atherogenic diets containing: 5 g CLA/kg, 2.5 g CLA + 2.5 g linoleic acid/kg or 5 g linoleic acid/kg. All diets were fed for 15 weeks and contained (g/kg): triacylglycerol 145, free fatty acids 5, cholesterol 10 and cholic acid 5. At the completion of the experimental period, when data from both groups fed on CLA were combined, dietary CLA did not produce significant differences in body weight, serum total cholesterol concentration or serum HDL-cholesterol concentration. However, mice receiving CLA developed a significantly higher serum HDL-cholesterol: total cholesterol ratio and a significantly lower serum triacylglycerol concentration than controls. Despite causing a serum lipoprotein profile considered to be less atherogenic, the addition of CLA to the atherogenic diet increased the development of aortic fatty streaks. Considering the increased atherogenesis associated with dietary CLA in the present study, and the failure to demonstrate a significant beneficial effect of CLA in other animal studies, there is currently no conclusive evidence to support the hypothesis that CLA protect against atherogenesis.     

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.     

Short-term feeding of conjugated linoleic acid does not induce hepatic steatosis in C57BL/6J mice

We investigated the effect of short-term feeding of conjugated linoleic acid (CLA) on adipose tissue weights, liver weight, hepatic lipid metabolism, and serum lipoprotein profiles in C57BL/6J mice. Mice were fed semi-synthetic diets containing either 6%, high-linoleic safflower oil (HL-SAF) or 4% HL-SAF+2% CLA for 1 wk. Short-term feeding of CLA showed an anti-obesity effect without inducing hepatomegaly in mice. In addition to the decline of hepatic triglyceride concentration, significant inhibition of A9 desaturation of fatty acid in the total liver lipids was found in CLA-fed mice. The CLA diet significantly increased the activities of peroxisomal beta-oxidation and decreased the activities of diacylglycerol acyltransferase, a triglyceride synthesis-related enzyme, in the liver. Moreover, serum lipoprotein profiles of CLA-fed mice showed preferable changes in the atherogenic indices. However, serum leptin and adiponectin were drastically decreased by CLA feeding, suggesting that prolonged administration of CLA would induce further decrease of serum adipocytokine levels, which may be a cause of lipodystrophy in mice. These results show that short-term feeding of CLA does not induce adverse effect in C57BL/6J mice.     

Conjugated linoleic acid in combination with supplemental dietary fat alters pork fat quality

Interest in fortification of human foods, including pork, with conjugated linoleic acid (CLA) is growing and may provide benefits as a neutraceutical based on research evaluating CLA as an anticarcinogen, immune modulator, antiatherogenic agent and a body composition modulator. This study evaluated the combined effects of dietary CLA and supplemental fat source on growth, fatty acid composition and belly quality of lean genotype gilts (n = 144). Pigs (49.3 kg) were randomly assigned to six diets (3 x 2 factorial) varying in supplemental fat (none, 4 g/100 g yellow grease or 4 g/100 g tallow) and linoleic acid [1 g/100 g corn oil (CO) or 1 g/100 g CLA (CLA-60)] for 47 d. Both the cis-9, trans-11 and the trans-10, cis-12 isomers of CLA were increased in belly and longissimus fat depots from pigs fed CLA, and that increase was up to 92% greater when CLA was fed with 4 g/100 g supplemental fat (fat source x linoleic acid interaction, P < 0.05). Pigs fed CLA had a greater concentration of 18:0 and less 18:1 cis-9 (P < 0.01) in various fat depots, suggesting a reduction in Delta(9) desaturase activity. The iodine value of belly fat from pigs consuming tallow and CLA combined was reduced to 62.0 from an initial value of 70.4. CLA supplementation also increased belly weights (P < 0.05). CLA did not affect longissimus muscle area, backfat depth and the percentage of fat-free lean (P > 0.10), but it increased the subjective intramuscular fat score by 18.8% (P < 0.01). In conclusion, CLA enrichment of pork products may be enhanced when combined with additional supplemental dietary fat, and together with tallow can be used to increase the saturated fatty acid content of pork.