Trans-vaccenic Acid Research Articles

Comparison of nutritional quality between conventional and organic dairy products: a meta‐analysis

As a contribution to the debate on the comparison of nutritional quality between conventional versus organic products, the present study would like to provide new results on this issue specifically on dairy products by integrating the last 3 years' studies using a meta-analysis approach with Hedges' d effect size method. The current meta-analysis shows that organic dairy products contain significantly higher protein, ALA, total omega-3 fatty acid, cis-9,trans-11 conjugated linoleic acid, trans-11 vaccenic acid, eicosapentanoic acid, and docosapentanoic acid than those of conventional types, with cumulative effect size ( ± 95% confidence interval) of 0.56 ± 0.24, 1.74 ± 0.16, 0.84 ± 0.14, 0.68 ± 0.13, 0.51 ± 0.16, 0.42 ± 0.23, and 0.71 ± 0.3, respectively. It is also observed that organic dairy products have significantly (P < 0.001) higher omega-3 to -6 ratio (0.42 vs. 0.23) and Δ9-desaturase index (0.28 vs. 0.27) than the conventional types. The current regulation on organic farming indeed drives organic farms to production of organic dairy products with different nutritional qualities from conventional ones. The differences in feeding regime between conventional and organic dairy production is suspected as the reason behind this evidence. Further identical meta-analysis may be best applicable for summarizing a comparison between conventional and organic foodstuffs for other aspects and food categories.

Conversion of t11t13 CLA into c9t11 CLA in Caco-2 cells and inhibition by sterculic oil.

BackgroundConjugated linoleic acids (CLA), and principally c9t11 CLA, are suspected to have numerous preventive properties regarding non-infectious pathologies such as inflammatory diseases, atherosclerosis and several types of cancer. C9t11 CLA is produced in the rumen during biohydrogenation of linoleic acid, but can also be synthesized in mammalian tissues from trans-vaccenic acid (C18:1 t11) through the action of delta-9 desaturase (D9D). For several years, it is also known that c9t11 CLA can be synthesized from conjugated linolenic acids (CLnA), i.e. c9t11c13 CLnA and c9t11t13 CLnA. This study aimed at investigating to which extent and by which route c9t11 CLA can be produced from another isomer of CLA, the t11t13 CLA that is structurally very similar to c9t11t13 CLnA, in Caco-2 cells.Methodology/Principal FindingsCaco-2 cells were incubated for 24 h with 20 µmol/l of t11t13 CLA in the absence or presence of sterculic oil used as an inhibitor of D9D. Caco-2 cells were able to convert t11t13 CLA into c9t11 CLA, and c9t11t13 CLnA was formed as an intermediate compound. In the presence of sterculic oil, the production of this intermediate was decreased by 46% and the formation of c9t11 CLA was decreased by 26%. No other metabolite was detected.Conclusions/SignificanceThese results not only highlight the conversion of t11t13 CLA into c9t11 CLA but demonstrate also that this conversion involves first a desaturation step catalysed by D9D to produce c9t11t13 CLnA and then the action of another enzyme reducing the double bond on the Δ13 position.

Ruminal microbe of biohydrogenation of trans-vaccenic acid to stearic acid in vitro

BackgroundOptimization of the unsaturated fatty acid composition of ruminant milk and meat is desirable. Alteration of the milk and fatty acid profile was previously attempted by the management of ruminal microbial biohydrogenation. The aim of this study was to identify the group of ruminal trans-vaccenic acid (trans-11 C18:1, t-VA) hydrogenating bacteria by combining enrichment studies in vitro.MethodsThe enrichment culture growing on t-VA was obtained by successive transfers in medium containing t-VA. Fatty acids were detected by gas chromatograph and changes in the microbial composition during enrichment were analyzed by denaturing gradient gel electrophoresis (DGGE). Prominent DGGE bands of the enrichment cultures were identified by 16S rRNA gene sequencing.ResultsThe growth of ruminal t-VA hydrogenating bacteria was monitored through the process of culture transfer according to the accumulation of stearic acid (C18:0, SA) and ratio of the substrate (t-VA) transformed to the product (SA). A significant part of the retrieved 16S rRNA gene sequences was most similar to those of uncultured bacteria. Bacteria corresponding to predominant DGGE bands in t-VA enrichment cultures clustered with t-VA biohydrogenated bacteria within Group B.ConclusionsThis study provides more insight into the pathway of biohydrogenation. It also may be important to control the production of t-VA, which has metabolic and physiological benefits, through management of ruminal biohydrogenation bacterium.

Grazing Period Variations in Cow Milk Vaccenic Acid (VA) and Conjugated Linoleic Acid (CLA)

The primary objective of this study was to examine the effect of breed, lactation and grazing period on the cis 9, trans 11-Conjugated Linoleic Acid (c9,t11-CLA) and trans 11-Vaccenic Acid (VA) levels in cow's milk. The secondary objective was to compare the properties of cheese products made from the study milk to commercially available cheeses. Milk samples from a commercial dairy farm representing 3 breeds (Fleckvieh Cross, n=19; Holstein, n=18; Jersey, n=12) were analyzed at three points in the grazing period. Daily yield, CLA yield, VA, yield and the percentage of VA in milk were greatest in June, intermediate in July and lowest in September. The percentage of c9,t11-CLA in milk was lower in September compared to June and July. The VA and c9,t11-CLA content of cheese made from the milk samples were ~2-fold higher than commercially available samples of Cheddar and ~1.5-fold higher than commercially available samples of Mozzarella. In conclusion, the c9,t11-CLA and VA contents of milk decrease over the June through September grazing period, likely due to the grazing material.

Trans Fatty Acids Induce Vascular Inflammation and Reduce Vascular Nitric Oxide Production in Endothelial Cells

Intake of trans fatty acids (TFA), which are consumed by eating foods made from partially hydrogenated vegetable oils, is associated with a higher risk of cardiovascular disease. This relation can be explained by many factors including TFA's negative effect on endothelial function and reduced nitric oxide (NO) bioavailability. In this study we investigated the effects of three different TFA (2 common isomers of C18 found in partially hydrogenated vegetable oil and a C18 isomer found from ruminant-derived—dairy products and meat) on endothelial NF-κB activation and nitric oxide (NO) production. Human endothelial cells were treated with increasing concentrations of Elaidic (trans-C18:1 (9 trans)), Linoelaidic (trans-C18:2 (9 trans, 12 trans)), and Transvaccenic (trans-C18:1 (11 trans)) for 3 h. Both Elaidic and Linoelaidic acids were associated with increasing NF-κB activation as measured by IL-6 levels and phosphorylation of IκBα, and impairment of endothelial insulin signaling and NO production, whereas Transvaccenic acid was not associated with these responses. We also measured superoxide production, which has been hypothesized to be necessary in fatty acid-dependent activation of NF-κB. Both Elaidic acid and Linoelaidic acid are associated with increased superoxide production, whereas Transvaccenic acid (which did not induce inflammatory responses) did not increase superoxide production. We observed differential activation of endothelial superoxide production, NF-κB activation, and reduction in NO production by different C18 isomers suggesting that the location and number of trans double bonds effect endothelial NF-κB activation.

Association of an ACSL1 gene variant with polyunsaturated fatty acids in bovine skeletal muscle

BackgroundThe intramuscular fat deposition and the fatty acid profiles of beef affect meat quality. High proportions of unsaturated fatty acids are related to beef flavor and are beneficial for the nutritional value of meat. Moreover, a variety of clinical and epidemiologic studies showed that particularly long-chain omega-3 fatty acids from animal sources have a positive impact on human health and disease.ResultsTo screen for genetic factors affecting fatty acid profiles in beef, we initially performed a microsatellite-based genome scan in a F2 Charolais × German Holstein resource population and identified a quantitative trait locus (QTL) for fatty acid composition in a region on bovine chromosome 27 where previously QTL affecting marbling score had been detected in beef cattle populations. The long-chain acyl-CoA synthetase 1 (ACSL1) gene was identified as the most plausible functional and positional candidate gene in the QTL interval due to its direct impact on fatty acid metabolism and its position in the QTL interval. ACSL1 is necessary for synthesis of long-chain acyl-CoA esters, fatty acid degradation and phospholipid remodeling. We validated the genomic annotation of the bovine ACSL1 gene by in silico comparative sequence analysis and experimental verification. Re-sequencing of the complete coding, exon-flanking intronic sequences, 3' untranslated region (3'UTR) and partial promoter region of the ACSL1 gene revealed three synonymous mutations in exons 6, 7, and 20, six noncoding intronic gene variants, six polymorphisms in the promoter region, and four variants in the 3' UTR region. The association analysis identified the gene variant in intron 5 of the ACSL1 gene (c.481-233A>G) to be significantly associated with the relative content of distinct fractions and ratios of fatty acids (e.g., n-3 fatty acids, polyunsaturated, n-3 long-chain polyunsaturated fatty acids, trans vaccenic acid) in skeletal muscle. A tentative association of the ACSL1 gene variant with intramuscular fat content indicated that an indirect effect on fatty acid composition via modulation of total fat content of skeletal muscle cannot be excluded.ConclusionsThe initial QTL analysis suggested the ACSL1 gene as a positional and functional candidate gene for fatty acid composition in bovine skeletal muscle. The findings of subsequent association analyses indicate that ACSL1 or a separate gene in close proximity might play a functional role in mediating the lipid composition of beef.

Distinct regulation of stearoyl-CoA desaturase 1 gene expression by cis and trans C18:1 fatty acids in human aortic smooth muscle cells

Consumption of trans fatty acids is positively correlated with cardiovascular diseases and with atherogenic risk factors. Trans fatty acids might play their atherogenic effects through lipid metabolism alteration of vascular cells. Accumulation of lipids in vascular smooth muscle cells is a feature of atherosclerosis and a consequence of lipid metabolism alteration. Stearoyl-CoA desaturase 1 (scd1) catalyses the production of monounsaturated fatty acids (e.g. oleic acid) and its expression is associated with lipogenesis induction and with atherosclerosis development. We were interested in analysing the regulation of delta-9 desaturation rate and scd1 expression in human aortic smooth muscle cells (HASMC) exposed to cis and trans C18:1 fatty acid isomers (cis-9 oleic acid, trans-11 vaccenic acid or trans-9 elaidic acid) for 48h at 100μM. Treatment of HASMC with these C18:1 fatty acid isomers led to differential effects on delta-9 desaturation; oleic acid repressed the desaturation rate more potently than trans-11 vaccenic acid, whereas trans-9 elaidic acid increased the delta-9 desaturation rate. We then correlated the delta-9 desaturation rate with the expression of scd1 protein and mRNA. We showed that C18:1 fatty acids controlled the expression of scd1 at the transcriptional level in HASMC, leading to an increase in scd1 mRNA content by trans-9 elaidic acid treatment, whereas a decrease in scd1 mRNA content was observed with cis-9 oleic acid and trans-11 vaccenic acid treatments. Altogether, this work highlights a differential capability of C18:1 fatty acid isomers to control scd1 gene expression, which presumes of different consequent effects on cell functions.

Consumption of dairy products of biodynamic origin is correlated with increased contents of rumenic and trans-vaccenic acid in the breast milk of lactating women

Our previous work showed that incorporation of organic dairy products in the maternal diet may lead to increased contents of the conjugated linoleic acid isomers (CLA) in human breast milk, which might positively affect infant’s health. Now, the effect of biodynamic—a special form of organic—dairy products in the diet on the CLA content in human breast milk has been analysed. The content of rumenic acid (the main CLA) in breast milk was higher in the women consuming biodynamic products (n = 64, 0.323% of total fat, P < 0.001) than in the women with a conventional diet (n = 175, 0.254%), with the group of women consuming other dairy products including organic (but not biodynamic) showing an intermediate value (n = 44, 0.279%). The contents of the CLA-precursor trans-vaccenic acid (TVA) paralleled those of rumenic acid, whereas the opposite was found for those of elaidic acid that often occurs in high concentrations in partially hydrogenated fats. Both the higher contents of CLA and TVA as well as the lower level of elaidic acid in the milk of women consuming biodynamic products might conceivably contribute to a better infant’s health.

Subcutaneous and intramuscular adipose tissue stearoyl-coenzyme A desaturase gene expression and fatty acid composition in calf- and yearling-fed Angus steers1

We proposed that stearoyl-CoA desaturase (SCD) activity dictates fatty acid composition of adipose tissue and muscle in beef cattle, regardless of ruminal or hepatic fatty acid hydrogenation or desaturation. Twelve Angus steers were assigned to a calf-fed (CF) group and slaughtered at weaning (8 mo of age; n=4), 12 mo of age (n=4), or 16 mo of age (n=4). Twelve steers were assigned to a yearling-fed (YF) group and slaughtered at 12 mo of age (n=4), 16 mo of age (n=4), and 17.5 mo of age (n=4; 525 kg, market weight). Data were analyzed based on time on the corn-based finishing diet, with terminal age as a covariate, and orthogonal polynomial contrasts were tested on the main effects of treatment group and time on the finishing diet. Fatty acids from duodenal digesta, plasma, liver, LM, and subcutaneous and intramuscular adipose tissue were measured, and SCD gene expression was measured in intramuscular and subcutaneous adipose tissues. In duodenal digesta, palmitic and linoleic acids increased by 100% over the sampling period, α-linolenic acid decreased over the sampling period, and trans-vaccenic acid was greater in YF than in CF steers (all P < 0.01). The proportion of α-linolenic acid decreased over time in all tissues, including liver. The SCD index (ratio of SCD fatty acid products to SCD fatty acid substrates) increased over time in LM and in intramuscular and subcutaneous adipose tissues. The SCD:glyceraldehyde 3-phosphate dehydrogenase mRNA ratio was virtually undetectable at the initial sampling periods in subcutaneous adipose tissue of YF and CF steers, and it increased over time (P < 0.01). The SCD index and SCD:glyceraldehyde 3-phosphate dehydrogenase ratio were greater in intramuscular adipose tissue of CF steers than in that of YF steers. The SCD index did not change over time in liver and decreased over time in duodenal digesta. We conclude that, unlike essential fatty acids, the SFA and MUFA composition of adipose tissue is regulated by adipose tissue fatty acid desaturation, with little contribution from hepatic or duodenal fatty acids.

Bovine milk fat enriched in conjugated linoleic and vaccenic acids attenuates allergic dermatitis in mice

Orally administered milk fat enriched in conjugated linoleic acid (CLA) and trans-vaccenic acid (VA) ('enriched milk fat'), produced by supplementing the diet of pasture-fed cows with fish and sunflower oil, has been shown previously to suppress the development of allergic airway disease in mice. To investigate whether topical or oral application of enriched milk fat and its two major fatty acids cis-9, trans-11 CLA (c9,t11-CLA) and VA inhibit allergic dermatitis in mice. Allergic dermatitis was induced in C57BL/6 mice by epicutaneous sensitization of tape-stripped skin with ovalbumin (OVA). Enriched milk fat and its two major fatty acids were either topically applied to the OVA-sensitized skin, or orally fed to mice by supplementation of the diet. Blood and skin tissues were collected for analysis after the third skin sensitization. Both topical and oral administration of enriched milk fat and its two major fatty acids led to significant suppression of allergic dermatitis as evidenced by reduced clinical and histological scores of affected skins, infiltration of inflammatory cells, and circulating allergen-specific IgE levels, compared with treatment with normal milk fat or the base control diet. C9,t11-CLA and VA individually inhibited multiple facets of allergic dermatitis when topically applied, and their combination produced a strong additive effect. Enriched milk fat, and its two major fatty acids c9,t11-CLA and vaccenic acid attenuate allergic dermatitis in mice.

Fatty acid composition of ruminal bacteria and protozoa, and effect of defaunation on fatty acid profile in the rumen with special reference to conjugated linoleic acid in cattle

Objectives of this study were to compare fatty acid (FA) composition of ruminal bacterial (B) and protozoal (P) cells, and to investigate effect of protozoa on FA profile in the rumen of cattle. Three cows were used to prepare ruminal B and P cells. Four faunated and three defaunated cattle (half-siblings) were used to study effect of protozoa on ruminal FA profile. Proportions of C16:0 and C18:0 in total fatty acids in B cells were 20.7% and 37.4%, whereas those in P cells were 33.4% and 11.6%, respectively. Proportions of trans-vaccenic acid (VA) and cis-9, trans-11 conjugated linoleic acid (CLA) in B cells were 3.9% and 1.0%, and those in P cells were 5.5% and 1.6%, respectively, being higher in P cells. Proportions of C18:1, C18:2 and C18:3 in P cells were two to three times higher than in B cells. Proportions of unsaturated fatty acids, VA and CLA in B cells of faunated cattle were higher than those of defaunated. VA and CLA in the ruminal fluid of faunated were also 1.6 to 2.5 times higher than those of defaunated. This tendency was similar for cell-free fraction of ruminal fluid. These results indicate that protozoa contribute greatly in VA and CLA production in the rumen.

A comparative study of fatty acid composition and CLA concentration in commercial cheeses

A total of 52 Italian and French commercial cheeses were analysed for fatty acid composition and conjugated linoleic acid (CLA) concentration. The cheeses were first grouped according to the ruminant species of the milk used in manufacturing, then according to the following criteria: (1) cheeses obtained from milk of the same ruminant species but using different production technologies; (2) cheeses produced from milk of different ruminant species but through similar cheesemaking processes. Comparative studies of fatty acid composition and CLA levels in the different cheese classes were carried out. In our study, the arrangement of the ruminant species according to the increasing CLA concentration in cheese was: goat = cow < sheep. Sheep cheeses had the highest levels of CLA (9.86 mg/g fat), α-linolenic acid (0.75%) and trans-vaccenic acid (1.63%), and the lowest contents of linoleic acid (1.80%) and oleic acid (16.83%). The comparison of cheeses obtained from milk of the same ruminant species but through different production technologies reported statistically significant differences in the fatty acid profiles that could be due to a different degree of lipolysis in the cheeses compared. Nevertheless, statistically significant differences in CLA concentration were not found; this suggests that the factors involved in the cheesemaking process generally do not affect the CLA content in milk fat.

Increased hypolipidemic benefits of cis-9, trans-11 conjugated linoleic acid in combination with trans-11 vaccenic acid in a rodent model of the metabolic syndrome, the JCR:LA-cp rat

BackgroundConjugated linoleic acid (cis-9, trans-11 CLA) and trans-11 vaccenic acid (VA) are found naturally in ruminant-derived foods. CLA has been shown to have numerous potential health related effects and has been extensively investigated. More recently, we have shown that VA has lipid-lowering properties associated with reduced hepatic lipidogenesis and chylomicron secretion in the JCR:LA-cp rat. The aim of this study was to evaluate potential additional hypolipidemic effects of purified forms of CLA and VA in an animal model of the metabolic syndrome (the JCR:LA-cp rat).MethodsTwenty four obese JCR:LA-cp rats were randomized and assigned to one of three nutritionally adequate iso-caloric diets containing 1% w/w cholesterol and 15% w/w fat for 16 wk: 1) control diet (CD), 2) 1.0% w/w cis-9, trans-11 CLA (CLA), 3) 1.0% w/w VA and 1% w/w cis-9, trans-11 CLA (VA+CLA). Lean rats were fed the CD to represent normolipidemic conditions.ResultsFasting plasma triglyceride (TG), total cholesterol and LDL-cholesterol concentrations were reduced in obese rats fed either the CLA diet or the VA+CLA diet as compared to the obese control group (p < 0.05, p < 0.001; p < 0.001, p < 0.01; p < 0.01, p < 0.001, respectively). The VA+CLA diet reduced plasma TG and LDL-cholesterol to the level of the normolipidemic lean rats and further decreased nonesterified fatty acids compared to the CLA diet alone. Interestingly, rats fed the VA+CLA diet had a higher food intake but lower body weight than the CLA fed group (P < 0.05). Liver weight and TG content were lower in rats fed either CLA (p < 0.05) or VA+CLA diets (p < 0.001) compared to obese control, consistent with a decreased relative protein abundance of hepatic acetyl-CoA carboxylase in both treatment groups (P < 0.01). The activity of citrate synthase was increased in liver and adipose tissue of rats fed, CLA and VA+CLA diets (p < 0.001) compared to obese control, suggesting increased mitochondrial fatty acid oxidative capacity.ConclusionWe demonstrate that the hypolipidemic effects of chronic cis-9, trans-11 CLA supplementation on circulating dyslipidemia and hepatic steatosis are enhanced by the addition of VA in the JCR:LA-cp rat.

Preparation and characterization of control materials for the analysis of conjugated linoleic acid and trans-vaccenic acid in beef

Beef and beef fat control composites (CC) were prepared for a large multi-year study of conjugated linoleic acid (CLA) and trans-vaccenic acid (TVA) in beef. Raw ground beef and beef suet were each frozen in liquid nitrogen, ground to a fine powder, dispensed into subsamples, and stored at − 60 °C under nitrogen. The CCs, reference materials (beef/pork fat; meat homogenate), and standards prepared at two concentrations of CLA and TVA added to a total lipid extract of beef (differing by 0.27 g/100 g CLA and 1.2432 g/100 g TVA) were analyzed via alkaline saponification of lipids, derivatization to fatty acid methyl esters, and GC. CLA and TVA recoveries from the standards were 95–113% (CLA) and 103–106% (TVA). Fatty acids quantified in the reference materials were within the certified ranges. Relative standard deviations ( n = 3 in each of 5 assay batches) were < 5% (TVA) and < 10% (CLA) for both CCs, at both laboratories.

Dietary Trans-11 Vaccenic Acid Increases Intestinal PPAR Alpha and Gamma Expression in the JCR:LA-cp Rat

Dietary Trans-11 Vaccenic Acid Increases Intestinal PPAR Alpha and Gamma Expression in the JCR:LA-cp Rat

Effects of oil source and fish oil addition on ruminal biohydrogenation of fatty acids and conjugated linoleic acid formation in beef steers fed finishing diets

Four Hereford steers (500 +/- 4.5 kg of BW) cannulated in the proximal duodenum were used to evaluate the effects of vegetable oil source or fish oil quantity on ruminal biohydrogenation (BH) and CLA outflow. Steers were fed 1 of 4 treatment diets in a 2 x 2 factorial arrangement of treatments (oil source: canola vs. corn oil; fish oil quantity: 0 or 1%) in a 4 x 4 Latin square design. The remainder of the diet included chopped bermudagrass hay, dry-rolled corn, and protein/mineral supplement. Duodenal samples were collected for 4 d after 11-d diet adaptation periods. Data were analyzed with animal, period, oil source, fish oil, and 2-way interaction among oil source and fish oil quantity in the model. All interactions among oil source and fish oil inclusion were nonsignificant with the exception of trans-11 vaccenic acid (TVA) and trans-9 octadecenoic acid. Intake and duodenal flow of total long-chain fatty acids did not differ between treatments. Apparent ruminal DM digestibility was not altered by oil source or fish oil inclusion. Apparent ruminal digestion of fatty acids did not differ among oil sources but was increased (P = 0.03) with fish oil supplementation. Ruminal BH of oleic and linolenic acids was increased (P = 0.01) for diets containing supplemental canola oil compared with corn oil. Ruminal BH of linoleic acid was greater (P = 0.01) for diets containing supplemental corn oil compared with canola oil. Fish oil addition reduced (P = 0.01) oleic acid BH but did not alter (P > 0.26) linoleic or linolenic acid BH. Duodenal flow of palmitic acid was greater (P = 0.05) for steers supplemented with corn oil compared with canola oil. Fish oil inclusion in the diet increased (P = 0.01) flow of n-3 fatty acids (eicosapentaenoic acid, docosapentaenoic acid, docosahexaenoic acid), trans-10 octadecenoic acid, trans-12 octadecenoic acid, and cis-9, trans-11 CLA. Trans-9 octadecenoic acid and TVA flows to the duodenum were increased (P = 0.01) when fish oil was included in the canola oil-supplemented diet; however, no changes were observed when fish oil was included in the corn oil-supplemented diet (P of interaction = 0.06 and 0.08). Fish oil inclusion increased the outflow of n-3 fatty acids, trans-10 octadecenoic acid, and the majority of CLA isomers including cis-9, trans-11. These results suggest that fish oil addition alters ruminal formation of BH intermediates that is dependent on oil source supplemented in the diet.

A review of fatty acid profiles and antioxidant content in grass-fed and grain-fed beef.

Growing consumer interest in grass-fed beef products has raised a number of questions with regard to the perceived differences in nutritional quality between grass-fed and grain-fed cattle. Research spanning three decades suggests that grass-based diets can significantly improve the fatty acid (FA) composition and antioxidant content of beef, albeit with variable impacts on overall palatability. Grass-based diets have been shown to enhance total conjugated linoleic acid (CLA) (C18:2) isomers, trans vaccenic acid (TVA) (C18:1 t11), a precursor to CLA, and omega-3 (n-3) FAs on a g/g fat basis. While the overall concentration of total SFAs is not different between feeding regimens, grass-finished beef tends toward a higher proportion of cholesterol neutral stearic FA (C18:0), and less cholesterol-elevating SFAs such as myristic (C14:0) and palmitic (C16:0) FAs. Several studies suggest that grass-based diets elevate precursors for Vitamin A and E, as well as cancer fighting antioxidants such as glutathione (GT) and superoxide dismutase (SOD) activity as compared to grain-fed contemporaries. Fat conscious consumers will also prefer the overall lower fat content of a grass-fed beef product. However, consumers should be aware that the differences in FA content will also give grass-fed beef a distinct grass flavor and unique cooking qualities that should be considered when making the transition from grain-fed beef. In addition, the fat from grass-finished beef may have a yellowish appearance from the elevated carotenoid content (precursor to Vitamin A). It is also noted that grain-fed beef consumers may achieve similar intakes of both n-3 and CLA through the consumption of higher fat grain-fed portions.

Biochemical Characterization of the Oxygenation of Unsaturated Fatty Acids by the Dioxygenase and Hydroperoxide Isomerase of Pseudomonas aeruginosa 42A2

We have studied oxygenation of fatty acids by cell extract of Pseudomonas aeruginosa 42A2. Oleic acid ((9Z)-18:1) was transformed to (10S)-hydroperoxy-(8E)-octadecenoic acid ((10S)-HPOME) and to (7S,10S)-dihydroxy-(8E)-octadecenoic acid (7,10-DiHOME). Experiments under oxygen-18 showed that 7,10-DiHOME contained oxygen from air and was formed sequentially from (10S)-HPOME by isomerization. (10R)-HPOME was not isomerized. The (10S)-dioxygenase and hydroperoxide isomerase activities co-eluted on ion exchange chromatography and on gel filtration with an apparent molecular size of approximately 50 kDa. 16:1n-7, 18:2n-6, and 20:1n-11 were also oxygenated to 7,10-dihydroxy fatty acids, and (8Z)-18:1 was oxygenated to 6,9-dihydroxy-(7E)-octadecenoic acid. A series of fatty acids with the double bond positioned closer to ((6Z)-18:1, (5Z,9Z)-18:2) or more distant from the carboxyl group ((11Z)-, (13Z)-, and (15Z)-18:1) were poor substrates. The oxygenation mechanism was studied with [7S-(2)H]18:1n-9, [7R-(2)H]18:2n-6, and [8R-(2)H]18:2n-6 as substrates. The pro-R hydrogen at C-8 was lost in the biosynthesis of (10S)-HPODE, whereas the pro-S hydrogen was lost and the pro-R hydrogen was retained at C-7 during biosynthesis of the 7,10-dihydroxy metabolites. Analysis of the fatty acid composition of P. aeruginosa revealed relatively large amounts of (9E/Z)-16:1 and (11E/Z)-18:1 and only traces of 18:1n-9. We found that (11Z)-18:1 (vaccenic acid) was transformed to (11S,14S)-dihydroxy-(12E)-octadecenoic acid and to a mixture of 11- and 12-HPOME, possibly due to reverse orientation of (11Z)-18:1 at the active site compared with oleic acid. The reaction mechanism of the hydroperoxide isomerase suggests catalytic similarities to cytochrome P450.

Effects of substitution of a proportion of the concentrate in grass silage/concentrate-based diets with extruded linseed on performance and meat quality of dairy bulls

This study investigated effects of substituting a proportion of the concentrate in a grass silage:concentrate-based diet with 0, 400, 800 or 1200 g extruded linseed/head/day on the performance and meat quality of dairy bulls. Forty-eight dairy-breed bulls ( i.e. 18 Holstein-Friesian, 6 Norwegian, 4 Norwegian × Holstein-Friesian, 12 Holstein × Norwegian and 8 Jersey × Holstein-Friesian), initial live weight (LW) and age 350 ± 30.9 kg and 11 ± 0.7 months, respectively were used. Grass silage was fed ad libitum and concentrates were fed daily on top of the silage. Concentrate intake was adjusted to ensure that total metabolizable energy intake from the supplement component of the diet ( i.e. concentrate plus linseed) was constant among all treatments. Animals were slaughtered at a target LW at slaughter of 540 kg and so were slaughtered in three batches after 120, 147 and 185 days on experiment. Substitution of a proportion of the concentrate diet with extruded linseed had no effects on animal performance ( i.e. dry matter intake, LW gain or carcass characteristics). Meat quality, in terms of cooking loss, sarcomere length, Warner Bratzler Shear Force, Commision Internationale de l’Eclairage (CIELAB) colour parameters L*, a*, b*, C* and Hue angle were not affected by dietary treatment. Substitution of a proportion of the concentrate diet with extruded linseed decreased palmitic acid (C16:0) and arachidonic acid (C20:4) concentrations ( P<0.05), saturated:unsaturated fatty acid (FA) ratio ( P<0.05) and the n-6:n-3 polyunsaturated FA (PUFA) ratio ( P<0.001) in muscle. Trans vaccenic acid (C18:1 t11), α-linolenic acid (C18:3n-3), n-3 PUFA ( P<0.05) and the ratio of PUFA:saturated (P:S) FA ( P<0.01) in muscle were increased by the linseed treatment. Results demonstrate the ability to manipulate the FA composition of the meat of dairy bulls by substituting a proportion of the concentrate diet with extruded linseed, with no detrimental effects on their performance or instrumental meat quality.

Trans-11 Vaccenic Acid Reduces Hepatic Lipogenesis and Chylomicron Secretion in JCR:LA-cp Rats1–3

Trans-11 vaccenic acid (VA) is the predominant trans isomer in ruminant fat and a major precursor to the endogenous synthesis of cis9,trans11-conjugated linoleic acid in humans and animals. We have previously shown that 3-wk VA supplementation has a triglyceride (TG)-lowering effect in a rat model of dyslipidemia, obesity, and metabolic syndrome (JCR:LA-cp rats). The objective of this study was to assess the chronic effect (16 wk) of VA on lipid homeostasis in both the liver and intestine in obese JCR:LA-cp rats. Plasma TG (P < 0.001), total cholesterol (P < 0.001), LDL cholesterol (P < 0.01), and nonesterified fatty acid concentrations, as well as the serum haptoglobin concentration, were all lower in obese rats fed the VA diet compared with obese controls (P < 0.05). In addition, there was a decrease in the postprandial plasma apolipoprotein (apo)B48 area under the curve (P < 0.05) for VA-treated obese rats compared with obese controls. The hepatic TG concentration and the relative abundance of fatty acid synthase and acetyl-CoA carboxylase proteins were all lower (P < 0.05) in the VA-treated group compared with obese controls. Following acute gastrointestinal infusion of a VA-triolein emulsion in obese rats that had been fed the control diet for 3 wk, the TG concentration was reduced by 40% (P < 0.05) and the number of chylomicron (CM) particles (apoB48) in nascent mesenteric lymph was reduced by 30% (P < 0.01) relative to rats infused with a triolein emulsion alone. In conclusion, chronic VA supplementation significantly improved dyslipidemia in both the food-deprived and postprandial state in JCR:LA-cp rats. The appreciable hypolipidemic benefits of VA may be attributed to a reduction in both intestinal CM and hepatic de novo lipogenesis pathways.