Response of piglets weaned from sows fed diets supplemented with conjugated linoleic acid (CLA) to an Escherichia coli K88+ oral challenge

Seventy-eight Cotswold piglets weaned from sows receiving 0% or 2% conjugated linoleic acid (CLA)-supplemented rations from day 85 of gestation through lactation were allocated to nursery diets (ND) according to their dam's lactation ration (LR) as follows (1) 0%-0% (0% CLA LR: 0% CLA ND, n = 17); (2) 0%-2% (0% CLA LR: 2% CLA ND, n = 17); (3) 2%-0% (2% CLA LR: 0% CLA ND, n = 23); and (4) 2%-2% (2% CLA LR: 2% CLA ND, n = 21). At 28 ± 2 days of age all piglets received an oral Escherichia coli K88+ (enterotoxigenic Escherichia coli, ETEC) challenge and were subsequently monitored for scour development and overall health until 36 ± 2 days of age, after which blood and tissue samples were collected. Piglet BW was not affected by dietary CLA supplementation to LR (P > 0.05). However, by day 36 piglets receiving 2% CLA-supplemented ND were significantly lighter (P < 0.05) than piglets receiving control diets. Average daily gain and feed efficiency were not affected by CLA supplementation. Average daily feed intake (ADFI) was greater for piglets weaned from 2% CLA-supplemented sows from day 17 to 28 (P < 0.05), otherwise ADFI was unaffected by dietary CLA supplementation (P > 0.05). The development of scours was less severe in piglets weaned from 2% CLA-supplemented sows at 8, 24, 48 and 56 h after ETEC challenge (P < 0.05). Intestinal coliform and lactic acid bacteria populations post challenge were not affected by CLA supplementation. However, cecal ammonia-N was numerically greatest in 0%-0% piglets compared to the other treatment groups, and the total volatile fatty acid production was numerically lower in 0%-0% and 0%-2% piglets compared to 2%-0% and 2%-2% piglets. In addition, piglets weaned from 2% CLA-supplemented sows had increased serum immunoglobulin A (P < 0.001) and G (P < 0.05) levels and reduced (P < 0.05) intestinal mucosal inflammation compared to piglets weaned from control sows. Although there were no obvious additional health effects observed when CLA was provided in ND, supplementing sow rations with 2% CLA from mid-gestation through weaning appears to have immune-stimulating carry-over effects post weaning. Thus, supplementing sow rations with CLA may be a practical strategy for enhancing passive immune transfer and improving the immune status and overall gut health of nursery piglets.     

Effect of monensin, fish oil or their combination on in vitro fermentation and conjugated linoleic acid (CLA) production by ruminal bacteria

An in vitro study was conducted to examine the effect of adding monensin, fish oil, or their combination on rumen fermentation and conjugated linoleic acid (CLA) production by mixed ruminal bacteria when incubated with safflower oil. Concentrate (1 g/100 ml) with safflower oil (0.2 g/100 ml) was added to a mixed solution (600 ml) of strained rumen fluid and buffer (control). Monensin (10 ppm), fish oil (0.02 g/100 ml), or monensin plus fish oil was also added into control mixture. All the culture solutions prepared were incubated anaerobically at 39 °C for 12 h. A higher pH and ammonia concentration were observed from the culture solution containing monensin at 12 h of incubation than those from the control or the culture containing fish oil. Monensin increased (P < 0.007) the C₃ content over all the collection times of culture solution while reducing the C₄ content at 6 h (P < 0.018) and 12 h (P < 0.001) of incubations. Supplementation of monensin, fish oil or their combination changed the content of C₁₈-fatty acids of ruminal culture. Monensin alone reduced (P < 0.021) the content of cis-9, trans-11 CLA compared to fish oil at all sampling times, but increased (P < 0.041) the trans-10, cis-12 CLA production compared to fish oil addition and the control which were similar at incubation for 12 h. The combination of monensin and fish oil increased the content of cis-9, trans-11 CLA (P < 0.023) and transvaccenic acid (TVA, P < 0.018) significantly compared to the control or monensin alone at incubation for 12 h.     

Development of conjugated linoleic acid (CLA)-mediated lipoatrophic syndrome in the mouse

Conjugated linoleic acids (CLA) are positional and geometric dienoic isomers of linoleic acid. Dietary CLA supplementation leads to a drop in fat mass in various species, including in humans. The t10,c12-CLA isomer is responsible for this anti-obesity effect. The reduction of fat mass is especially dramatic in the mouse, in which it is associated with severe hyperinsulinemia, insulin resistance and massive liver steatosis. The origin of these adverse side effects and putative chronology of events leading to CLA-mediated lipoatrophic syndrome are presented and discussed in this review.     

Enzymatic fractionation of conjugated linoleic acid isomers by selective esterification

Attempt was done to prepare food supplements with high content of c9, t11-CLA or t10, c12-CLA. A free acid mixture containing CLA isomers was esterified with ethanol by enzyme catalysis. Novozyme 435 and Lipase AY30 were screened, and Lipase AY30 was employed to catalyze esterification reaction because of its high fractionation efficiency. Effect of reaction conditions on total esterification was investigated, and the optimal reaction conditions were: 140 U of lipase amount, reaction temperature at 50 °C, a pH of 6.5, and molar ratio of FFA–CLA to ethanol at 1:1. Based on the studies above, experiments of esterification and purification were done, and the best fractionation efficiency was obtained when the total esterification was 37%, and the corresponding purity and recovery of c9, t11-CLA were 75.50 and 49.85%, and that of t10, c12-CLA were 72.02 and 62.32%.     

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.     

Trans-10,cis-12 conjugated linoleic acid (CLA) interferes with lipid droplet accumulation during 3T3-L1 preadipocyte differentiation

In this study, we hypothesize that the biologically active isomers of conjugated linoleic acid (CLA), cis-9,trans-11 (c9,t11) and trans-10,cis-12 (t10,c12) CLA, have different effects on early and late stages 3T3-L1 preadipocyte differentiation. Both c9-t11 and t10-c12CLA stimulated early stage pre-adipocyte differentiation (day 2), while t10-c12CLA inhibited late differentiation (day 8) as determined by lipid droplet numbers and both perilipin-1 levels and phosphorylation state. At day 8, the adipokines adiponectin, chemerin and adipsin were all reduced in t10-c12CLA treated cells versus control cells. Immunofluorescence microscopy showed perilipin-1 was present solely on lipid droplets on day 8 in t10-c12 treated 3T3-L1 cells, whereas preilipin-1 was also located in the perinuclear region in control and c9-t11 treated cells. The t10-c12CLA isomer also decreased levels of hormone-sensitive lipase and inhibited lipolysis. These findings indicate that the decrease in lipid droplets caused by t10-c12CLA is the result of an inhibition of lipid droplet production during adipogenesis rather than a stimulation of lipolysis. Additionally, treatment with Gö6976 blocked the effect of t10-c12CLA on perilipin-1 phosphorylation, implicating PKCα in perilipin-1 phosphorylation, and thus a regulator of triglyceride catabolism. These data are supported by evidence that t10-c12CLA activated PKCα. These are the first data to show that CLA isomers can affect lipid droplet dynamics in adipocytes through PKCα.     

Antioxidant activity of conjugated linoleic acid isomers, linoleic acid and its methyl ester determined by photoemission and DPPH techniques

The chemiluminescent response of conjugated linoleic acid isomers (CLAs), linoleic acid (LA) and methyl linoleate (LAME) against the prooxidant t-butyl hydroperoxide (tBHP) was analyzed. The c9, t11-CLA and t10, c12-CLA isomers showed significant photoemission at the highest concentration used, while photoemission was not detected at any concentration of LA and LAME analyzed. These results show that CLAs are more susceptible to peroxidation than LA and LAME. Likewise, the effect of CLA, LA and LAME on lipid peroxidation of triglycerides rich in C20:5 omega3 and C22:6 omega3 (Tg omega3-PUFAs) was investigated. For that, chemiluminescence produced by triglycerides in the presence of tBHP, previously incubated with different concentrations of CLAs, LA and LAME (from 1 to 200 mM) was registered for 60 min. Triglycerides in the presence of t-BHP produced a peak of light emission (3151+/-134 RLUs) 5 min after addition. CLAs produced significant inhibition on photoemission, t10, c12-CLA being more effective than the c9, t11-CLA isomer. LA and LAME did not have an effect on lipid peroxidation of Tg omega3-PUFAs. CLA isomers, LA and LAME were also investigated for free radical scavenging properties against the stable radical (DPPH()). Both CLA isomers reacted and quenched DPPH() at all tested levels (from 5 to 25 mM), while LA and LAME did not show radical quenching activity even at the highest concentration tested. These data indicate that CLAs would provide protection against free radicals, but LA and LAME cannot.     

Effect of pH on conjugated linoleic acid (CLA) formation of linolenic acid biohydrogenation by ruminal microorganisms

Conventional beliefs surrounding the linolenic acid (LNA; cis-9 cis-12 cis-15 C18:3) biohydrogenation (BH) pathway propose that it converts to stearic acid (SA) without the formation of conjugated linoleic acid (CLA) as intermediate isomers. However, an advanced study (Lee and Jenkins, 2011) verified that LNA BH yields multiple CLAs. This study utilized the stable isotope tracer to investigate the BH intermediates of ¹³C-LNA with different pH conditions (5.5 and 6.5). The ¹³C enrichment was calculated as a ¹³C/¹²C ratio of labeled minus unlabeled. After 24 h, eight CLA isomers were significantly enriched on both pH treatment, this result verifies that these CLAs originated from ¹³C-LNA BH which supports the results of Lee and Jenkins (2011). The enrichment of cis-cis double bond CLAs (cis-9 cis-11 and cis-10 cis-12 CLA) were significantly higher at low pH conditions. Furthermore, the concentration of cis-10 cis-12 CLA at low pH was four times higher than at high pH conditions after a 3 h incubation. These differences support the LNA BH pathways partial switch under different pH conditions, with a strong influence on the cis-cis CLA at low pH. Several mono-, di-, and tri-enoic fatty acid isomers were enriched during 24 h of incubation, but the enrichment was decreased or restricted at low pH treatment. Based on these results, it is proposed that low pH conditions may cause a changed or limited capacity of the isomerization and reduction steps in BH.     

Impairment of 8-iso-PGF2ALPHA isoprostane metabolism by dietary conjugated linoleic acid (CLA)

8-iso-PGF_2α isoprostane (IP) is one of the most-used markers of lipid peroxidation in experimental models and humans. After its formation, it is promptly metabolized to 2,3 dinor (DIN) in peroxisomes.Conjugated linoleic acid (CLA) is preferentially β-oxidized in peroxisomes which may compete with IP, and thereby may affect its metabolism.In order to verify whether CLA is able to influence IP formation and/or metabolism and to explain the mechanism, we challenged rats supplemented with CLA or with triolein (as a control fatty acid), with a single dose of carbon tetrachloride (CCl₄) or of bacterial lipopolysaccharide (LPS). The results showed that IP and its precursor arachidonic acid hydroperoxide, as well as malondialdheyde (MDA), increase significantly in the liver of rats challenged with CCl₄, irrespective of the diet, while in LPS-treated rats only nitrites in liver and isoprostane in plasma increase. On the other hand, the peroxisomal β-oxidation products of IP, the DIN, is significantly lower in the CLA group with respect to control and triolein groups.To further investigate whether this is due to competition between CLA and IP at the cellular level, we incubated human fibroblasts from healthy subjects or patients with adrenoleukodystrophy (ALD), with CLA and/or commercially available IP. The rationale of this approach is based on the deficient peroxisomal β-oxidation of fibroblasts from ALD patients, leading to a reduced formation of DIN. In both normal and ALD cells, the presence of CLA significantly inhibits the formation of DIN from IP.We may conclude that both in vitro and in vivo studies strongly suggest that CLA may impair IP catabolism in peroxisomes. Consequently an increase of IP, as a sole result of CLA intake, cannot be considered as a marker of lipid peroxidation.     

Production of conjugated linoleic acid by probiotic Lactobacillus acidophilus La-5

Aims:  To study the ability of the probiotic culture Lactobacillus acidophilus La-5 to produce conjugated linoleic acid (CLA), which is a potent anti-carcinogenic agent.
Methods and Results:  The conversion of linoleic acid to CLA was studied both by fermentation in a synthetic medium and by incubation of washed cells. Accumulation of CLA was monitored by gas chromatography analysis of the biomass and supernatants. While the fermentation conditions applied may not be optimal to observe CLA production in growing La-5 cells, the total CLA surpassed 50% of the original content in the washed cells after 48 h under both aerobic and micro-aerobic conditions. The restriction of oxygen did not increase the yield, but favoured the formation of trans, trans isomers.
Conclusions:  The capability of L. acidophilus La-5 to produce CLA is not dependant on the presence of milk fat or anaerobic conditions. Regulation of CLA production in this strain needs to be further investigated to exploit the CLA potential in fermented foods.
Significance and Impact of the study:  Knowledge gained through the conditions on the accumulation of CLA would provide further insight into the fermentation of probiotic dairy products. The capacity of the nongrowing cells to produce CLA is also of great relevance for the emerging nonfermented probiotic foods.     

Effects of whole linseed and rumen-protected conjugated linoleic acid enriched diets on beef quality

Instrumental assessments and sensory tests were performed to evaluate the effects of diet and postmortem ageing time (1, 7 and 21 days) on beef quality. A total of 48 Friesian calves were randomly allocated to four dietary treatments: control, whole linseed (10% linseed), conjugated linoleic acid (CLA) (2% protected CLA), and whole linseed+CLA (10% linseed and 2% protected CLA). Animals were slaughtered at 458±16.6 kg live weight and 11 months of age. Ageing was more significant than diet on most instrumental parameters. Meat from linseed enriched diets had greater drip loss (P⩽0.001) and intramuscular fat (P⩽0.01) than meat from animals fed CLA. Beef aged for 7 and 21 days had lower cooking losses (P⩽0.01) and shear force (P⩽0.001) than beef aged for 1 day. Lightness was affected only by display time. The addition of CLA in the diet increased hue and yellowness, whereas the inclusion of linseed decreased these values, as well as increased redness. Linseed in the diet decreased fat odour (P⩽0.05), but increased beef (P⩽0.01) and liver (P⩽0.05) flavours. Meat aged for 21 days was significantly more rancid (P⩽0.001), even under vacuum storage. Several organoleptic properties were improved with the inclusion of linseed in the diet, whereas they remained unaffected by the inclusion of CLA.     

Metabolic regulation of fatty acid esterification and effects of conjugated linoleic acid on glucose homeostasis in pig hepatocytes

Conjugated linoleic acids (CLAs) are geometric and positional isomers of linoleic acid (LA) that promote growth, alter glucose metabolism and decrease body fat in growing animals, although the mechanisms are poorly understood. A study was conducted to elucidate the effects of CLA on glucose metabolism, triglyceride (TG) synthesis and IGF-1 synthesis in primary culture of porcine hepatocytes. In addition, hormonal regulation of TG and IGF-1 synthesis was addressed. Hepatocytes were isolated from piglets (n = 5, 16.0 ± 1.98 kg average body weight) by collagenase perfusion and seeded into collagen-coated T-25 flasks. Hepatocytes were cultured in William's E containing dexamethasone (10-8 and 10-7 M), insulin (10 and 100 ng/ml), glucagon (0 and 100 ng/ml) and CLA (1 : 1 mixture of cis-9, trans-11 and trans-10, cis-12 CLA, 0.05 and 0.10 mM) or LA (0.05 and 0.10 mM). Addition of CLA decreased gluconeogenesis (P < 0.05), whereas glycogen synthesis and degradation, TG synthesis and IGF-1 synthesis were not affected compared with LA. Increased concentration of fatty acids in the media decreased IGF-1 production (P < 0.001) and glycogen synthesis (P < 0.01), and increased gluconeogenesis (P < 0.001) and TG synthesis (P < 0.001). IGF-1 synthesis increased (P < 0.001) and TG synthesis decreased (P < 0.001) as dexamethasone concentration in the media rose. High insulin/glucagon increased TG synthesis. These results indicate that TG synthesis in porcine hepatocytes is hormonally regulated so that dexamethasone decreases and insulin/glucagon increases it. In addition, CLA decreases hepatic glucose production through decreased gluconeogenesis.     

Overexpression of stearoyl-CoA desaturase-1 results in an increase of conjugated linoleic acid (CLA) and n-7 fatty acids in 293 cells

The effect of human SCD1 heterologous expression on cellular fatty acid synthesis was investigated in the current study. The SCD1 gene expression cassette and PGK-neomycin-selectable marker cassette were co-introduced into HEK 293 cells by electroporation, and subsequently, SCD1 expression was evaluated by fatty acid analysis. RT-PCR analysis indicated that the foreign SCD1 gene could be expressed in transformed cell lines. Total lipid analysis of the transformed cells fed with vaccenic acid (t11-18:1) as a substrate showed that SCD1 expression resulted in an increase in c9t11-CLA from 0.73-1.03% to 2.69-2.86% (p < 0.05) and that the conversion efficiency was elevated from 5.11-6.88% to 16.49-20.06% (p < 0.05). Surprisingly, the concentration of t10c12-CLA was also increased, from 0.10-0.41% to 1.35-1.69% in SCD1 cells (p < 0.05). SCD1 expression also resulted in a significant (p < 0.05) increase in palmitoleic acid (16:1 n-7) from 1.56-2.26% to 3.47-4.04% and cis-vaccenic acid (18:1 n-7) from 2.42-3.97% to 6.20-7.22%, and the corresponding conversion ratio of n-7 fatty acid was elevated from 12.01-16.70% to 22.62-24.13% (p < 0.05). This study demonstrates that the foreign SCD1 gene was expressed with high efficiency and induced elevated c9t11-CLA, t10c12-CLA, and n-7 fatty acid levels in mammalian cells.     

Conjugated linoleic acid (CLA) prevents age-associated skeletal muscle loss

In this study, we examined the effect of CLA isomers in preventing age-associated muscle loss and the mechanisms underlying this effect, using 12-months-old C57BL/6 mice fed 10% corn oil (CO) or a diet supplemented with 0.5% c9t11-CLA, t10c12-CLA, or c9t11-CLA+t10c12-CLA (CLA-mix) for 6 months. Both t10c12-CLA and CLA-mix groups showed significantly higher muscle mass, as compared to CO and c9t11-CLA groups, measured by dual-energy X-ray absorptiometry and muscle wet weight. Enhanced mitochondrial ATP production, with higher membrane potential, and elevated muscle antioxidant enzymes (catalase and glutathione peroxidase) production, accompanied by slight increase in H₂O₂ production was noted in t10c12-CLA and CLA-mix groups, as compared to that of CO and c9t11-CLA groups. Oxidative stress, as measured by serum malondialdehyde and inflammation, as measured by LPS-treated splenocyte IL-6 and TNF-α, were significantly less in CLA isomers groups. Thus, CLA may be a novel dietary supplement that will prevent sarcopenia by maintaining redox balance during aging.     

Selective production of cis-9,trans-11 isomer of conjugated linoleic acid from trans-vaccenic acid methyl ester by Delacroixia coronata

Aims:  Bio-process development for isomer selective and efficient production of cis -9, trans -11-octadecadienoic acid (CLA) from trans -vaccenic acid ( t -VA, trans -11-octadecenoic acid) through microbial fatty acid Δ9-desaturation reaction.
Methods and Results:  A total of 550 strains of fungi and yeasts were screened for CLA production from t -VA through Δ9 desaturation. Delacroixia coronata IFO 8586 was selected as a potent producer of CLA from t -VA. Efficient CLA production was observed during cultivation in medium supplemented with the methyl ester of t -VA ( t -VAME). Under the optimal conditions with 33·3 mg ml⁻¹ of t -VAME as substrate, 10·5 mg ml⁻¹ CLA was produced by D. coronata IFO 8586 after 7 days of cultivation in the medium containing dextrin (5·0%), tryptone (2·0%) and thiourea (0·83 μmol ml⁻¹). The strain produced the cis -9, trans -11 isomer of CLA selectively (98% of total CLA), with a small amount of the trans -9, trans -11 isomer (2% of total CLA), mainly in the form of triacylglycerols (69% of total CLA).
Conclusions:  A practical bio-process for selective production of cis -9, trans -11 isomer of CLA using filamentous fungus D. coronata IFO 8586 was successfully established.
Significance and Impact of the Study:  Isomer selective bio-process for the practical production of cis -9, trans -11-CLA was first established. The process is benefitable for expanding the application of CLA for medicinal and nutraceutical purposes.     

9 cis,11 trans conjugated linoleic acid (CLA) is synthesised and desaturated into conjugated 18:3 in bovine adipose tissues

Although endogenous synthesis of conjugated linoleic acid (CLA) in the mammary gland of lactating cows has been already well documented, no study has determined so far as to which tissue and/or organ is involved in CLA synthesis in the growing ruminant except one study showing that CLA synthesis does not occur in ruminant liver. In this context, adipose tissue appears to be a good candidate for endogenous synthesis of CLA in the growing ruminant. The aim of this study was to compare the respective metabolisms of 11trans 18:1 (vaccenic acid, VA) and 9cis,11trans 18:2 (rumenic acid) to that of stearic acid (the preferential substrate of Δ9 desaturase) in adipose tissues (subcutaneous, SC and intermuscular, IM) of six Charolais steers by using the in vitromethod of incubated tissue slices. Samples of SC and IM adipose tissues were incubated at 37°C for 16 h under an atmosphere of 95% O2/5% CO2 in a medium supplemented with 0.75 mM of fatty acid (FA) mixture (representative of circulating non-esterified FA) and 186 μM [1-14C]-18:0 or 58.6 μM [1-14C]-VA or 56 μM [1-14C]-9cis,11trans CLA. Viability of explants was verified by measuring metabolic functions (glucose uptake and glucose-6-phosphate dehydrogenase activity). After 16 h of incubation, FA uptake was similar for all FA (18:0, VA and 9cis,11trans 18:2) in both SC and IM adipose tissues (around 40%). Once in adipose tissue, all FA were preferentially esterified (>80% of cell FA) favouring neutral lipid synthesis (around 90% of esterified FA). Stearic acid was highly (27%) desaturated into oleic acid in SC adipose tissue whereas this desaturation was much lower (6.8%) in IM adipose tissue (P < 0.0001). VA was desaturated into 9cis,11trans CLA at a low extent of about 2.5% to 4.4% in both adipose tissues probably because of a limited affinity of Δ9 desaturase for VA. 9cis,11trans CLA was itself converted by desaturation into 6cis, 9cis,11trans 18:3 at the intensity of 10.8% and 14.5% of cell 9cis,11trans CLA in SC and IM adipose tissues, respectively. In conclusion, bovine adipose tissues of the growing ruminant were especially involved in the endogenous synthesis of CLA from VA and in its desaturation into conjugated derivative, mainly 6cis, 9cis,11trans 18:3, of which biological properties need to be elucidated.     

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.     

Substrate selectivity of lipases in the esterification of cis/trans-isomers and positional isomers of conjugated linoleic acid (CLA)

The substrate selectivity of several microbial lipases has been examined in the esterification of the conjugated linoleic acid (CLA) isomers cis-9,trans-11-, cis-9,cis-11-, trans-9,trans-11- and trans-10,cis-12-octadecadienoic acid with n-butanol in n-hexane. Lipases from Candida cylindracea and Mucor miehei had a preference for the cis-9,trans-11-octadecadienoic acid, while Chirazyme L-5, a Candida antarctica lipase A, accepted the trans-9,trans-11-fatty acid with a high selectivity. Moreover, lipase from Candida cylindracea and Chirazyme L-5 catalysed the esterification of the cis-9,trans-11-octadecadienoic acid with n-butanol faster than the corresponding reaction of the trans-10,cis-12-fatty acid.     

Effects of dietary sources of vegetable fats on performance of dairy ewes and conjugated linoleic acid (CLA) in milk

Two experiments were carried out to study the effects of supplementing the ration of lactating ewes with vegetable fats (sunflower oil, SO or hydrogenated palm oil, HPO; HIDROPALM^®) on diet digestibility, milk yield and milk composition, and on the concentration of the conjugated linoleic acid (CLA) C18:2 cis-9 trans-11 and C18:1 trans-11 (vaccenic acid, VA) and other main fatty acids in milk fat. Treatments involved a control diet, without added oil, and 2 diets supplemented with either 12 g/kg SO or 12 g/kg HPO on a dry matter (DM) basis. In the first experiment, 6 non-pregnant, non-lactating Lacaune ewes were used following a 3 × 3 replicated Latin Square design. Addition of vegetable fat supplement to the diet increased digestibility of DM, organic matter (OM) and crude protein (CP), but did not affect that of the ether extract (EE), neutral detergent fibre (NDF) or acid detergent fibre (ADF). In the second experiment, 60 Lacaune dairy ewes mid-way through lactation (120 ± 12 days in milk, 0.98 ± 0.03 kg/day average milk yield) were divided into three equal-sized groups each of which was assigned to one of the three experimental diets for 4 weeks. Compared with the control treatment, supplementation with HPO increased milk yield and energy-corrected milk. But neither vegetable fat supplement modified percentages of fat and protein in milk. Supplementation with HPO increased C14:1, C16:1 and C16:0 content and reduced C18:0 and C18:1 cis-9 content in milk fat. Supplementation with SO increased the VA content in milk fat by 36% and that of cis-9 trans-11 CLA by 29% in comparison with the control diet. Supplementation with HPO led to milk fat with 15% more cis-9 trans-11 CLA than control milk. In conclusion, adding a moderate dose of HPO or SO to the diets increased CLA concentration in milk fat. Nevertheless, supplementation with SO was more effective than HPO in increasing CLA concentration in milk fat and reducing the atherogenicity index, improving milk quality from the human health standpoint.     

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

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