Trans-vaccenic acid is desaturated to conjugated linoleic acid in mice

Trans-vaccenic acid reprograms CD8+ T cells and anti-tumour immunity

Diet-derived nutrients are inextricably linked to human physiology by providing energy and biosynthetic building blocks and by functioning as regulatory molecules. However, the mechanisms by which circulating nutrients in the human body influence specific physiological processes remain largely unknown. Here we use a blood nutrient compound library-based screening approach to demonstrate that dietary trans-vaccenic acid (TVA) directly promotes effector CD8+ T cell function and anti-tumour immunity in vivo. TVA is the predominant form of trans-fatty acids enriched in human milk, but the human body cannot produce TVA endogenously1. Circulating TVA in humans is mainly from ruminant-derived foods including beef, lamb and dairy products such as milk and butter2,3, but only around 19% or 12% of dietary TVA is converted to rumenic acid by humans or mice, respectively4,5. Mechanistically, TVA inactivates the cell-surface receptor GPR43, an immunomodulatory G protein-coupled receptor activated by its short-chain fatty acid ligands6-8. TVA thus antagonizes the short-chain fatty acid agonists of GPR43, leading to activation of the cAMP-PKA-CREB axis for enhanced CD8+ T cell function. These findings reveal that diet-derived TVA represents a mechanism for host-extrinsic reprogramming of CD8+ T cells as opposed to the intrahost gut microbiota-derived short-chain fatty acids. TVA thus has translational potential for the treatment of tumours.

Normal-Fat vs. High-Fat Diets and Olive Oil vs. CLA-Rich Dairy Fat: A Comparative Study of Their Effects on Atherosclerosis in Male Golden Syrian Hamsters

The relationship between milk fat intake (because of its high saturated fatty acid content) and the risk of suffering from cardiovascular diseases remains controversial. Thus, Golden Syrian hamsters were fed two types of fat-sheep milk fat that was rich in rumenic (cis9,trans11-18:2) and vaccenic (trans11-18:1) acids and olive oil-and two doses (a high- or normal-fat diet) for 14 weeks, and markers of lipid metabolism and atherosclerosis evolution were analyzed. The results revealed that the type and percentage of fat affected most plasma biochemical parameters related to lipid metabolism, while only the expression of five (CD36, SR-B1, ACAT, LDLR, and HMG-CoAR) of the studied lipid-metabolism-related genes was affected by these factors. According to aortic histology, when ingested in excess, both fats caused a similar increase in the thickness of fatty streaks, but the high-milk-fat-based diet caused a more atherogenic plasma profile. The compositions of the fats that were used, the results that were obtained, and the scientific literature indicated that the rumenic acid present in milk fat would regulate the expression of genes involved in ROS generation and, thus, protect against LDL oxidation, causing an effect similar to that of olive oil.

Serum Metabonomics Reveals Risk Factors in Different Periods of Cerebral Infarction in Humans

Studies of key metabolite variations and their biological mechanisms in cerebral infarction (CI) have increased our understanding of the pathophysiology of the disease. However, how metabolite variations in different periods of CI influence these biological processes and whether key metabolites from different periods may better predict disease progression are still unknown. We performed a systematic investigation using the metabonomics method. Various metabolites in different pathways were investigated by serum metabolic profiling of 143 patients diagnosed with CI and 59 healthy controls. Phe-Phe, carnitine C18:1, palmitic acid, cis-8,11,14-eicosatrienoic acid, palmitoleic acid, 1-linoleoyl-rac-glycerol, MAG 18:1, MAG 20:3, phosphoric acid, 5α-dihydrotestosterone, Ca, K, and GGT were the major components in the early period of CI. GCDCA, glycocholate, PC 36:5, LPC 18:2, and PA showed obvious changes in the intermediate time. In contrast, trans-vaccenic acid, linolenic acid, linoleic acid, all-cis-4,7,10,13,16-docosapentaenoic acid, arachidonic acid, DHA, FFA 18:1, FFA 18:2, FFA 18:3, FFA 20:4, FFA 22:6, PC 34:1, PC 36:3, PC 38:4, ALP, and Crea displayed changes in the later time. More importantly, we found that phenylalanine metabolism, medium-chain acylcarnitines, long-chain acylcarnitines, choline, DHEA, LPC 18:0, LPC 18:1, FFA 18:0, FFA 22:4, TG, ALB, IDBIL, and DBIL played vital roles in the development of different periods of CI. Increased phenylacetyl-L-glutamine was detected and may be a biomarker for CI. It was of great significance that we identified key metabolic pathways and risk metabolites in different periods of CI different from those previously reported. Specific data are detailed in the Conclusion section. In addition, we also explored metabolite differences of CI patients complicated with high blood glucose compared with healthy controls. Further work in this area may inform personalized treatment approaches in clinical practice for CI by experimentally elucidating the pathophysiological mechanisms.

A comparison of the satiating properties of medium-chain triglycerides and conjugated linoleic acid in participants with healthy weight and overweight or obesity

PURPOSE

Inconsistent evidence exists for greater satiety after medium-chain triglycerides (MCT) or conjugated linoleic acid (CLA) compared to long-chain triglycerides (LCT). Furthermore, the mechanisms are poorly understood and effects in people with a healthy weight and those with overweight/obesity have not been compared. This study aimed to compare appetite responses in these groups and examine the mechanisms behind any differences.

METHODS

Fifteen participants with healthy weight (BMI: 22.7 ± 1.9 kg·m-2) and fourteen participants with overweight/obesity (BMI: 30.9 ± 3.9 kg·m-2) consumed a breakfast containing either 23.06 g vegetable oil (CON), 25.00 g MCT oil (MCT), or 6.25 g CLA and 16.80 g vegetable oil (CLA). Appetite, peptide YY (PYY), total ghrelin (TG), β-hydroxybutyrate, and gastric emptying (GE) were measured throughout. Energy intake was assessed at an ad libitum lunch and throughout the following ~ 36 h.

RESULTS

Neither MCT nor CLA decreased ad libitum intake; however MCT decreased day 1 energy intake (P = 0.031) and the 48-h period (P = 0.005) compared to CON. MCT delayed GE (P ≤ 0.01) compared to CON, whereas CLA did not. PYY and TG concentrations were not different (P = 0.743 and P = 0.188, respectively), but MCT increased β-hydroxybutyrate concentrations compared to CON (P = 0.005) and CLA (P < 0.001). β-hydroxybutyrate concentrations were higher in participants with overweight/obesity (P = 0.009).

CONCLUSION

Consumption of MCT reduces energy intake in the subsequent 48 h, whereas CLA does not. Delayed gastric emptying or increased β-hydroxybutyrate concentrations may mediate this.

CYP4F13 is the Major Enzyme for Conversion of alpha-Eleostearic Acid into cis-9, trans-11-Conjugated Linoleic Acid in Mouse Hepatic Microsomes

Our previous studies have shown that α-eleostearic acid (α-ESA; cis-9, trans-11, trans-13 (c9,t11,t13)-conjugated linolenic acid (CLnA)) is converted into c9,t11-conjugated linoleic acid (CLA) in rats. Furthermore, we have demonstrated that the conversion of α-ESA into CLA is a nicotinamide adenine dinucleotide phosphate (NADPH)-dependent enzymatic reaction, which occurs mostly in the rat liver. However, the precise metabolic pathway and enzyme involved have not been identified yet. Therefore, in this study we aimed to determine the role of cytochrome P450 (CYP) in the conversion of α-ESA into c9,t11-CLA using an in vitro reconstitution system containing mouse hepatic microsomes, NADPH, and α-ESA. The CYP4 inhibitors, 17-ODYA and HET0016, performed the highest level of inhibition of CLA formation. Furthermore, the redox partner cytochrome P450 reductase (CPR) inhibitor, 2-chloroethyl ethyl sulfide (CEES), also demonstrated a high level of inhibition. Thus, these results indicate that the NADPH-dependent CPR/CYP4 system is responsible for CLA formation. In a correlation analysis between the specific activity of CLA formation and Cyp4 family gene expression in tissues, Cyp4a14 and Cyp4f13 demonstrated the best correlations. However, the CYP4F substrate prostaglandin A₁ (PGA₁) exhibited the strongest inhibitory effect on CLA formation, while the CYP4A and CYP4B1 substrate lauric acid had no inhibitory effect. Therefore, we conclude that the CYP4F13 enzyme is the major enzyme involved in CLA formation. This pathway is a novel pathway for endogenous CLA synthesis, and this study provides insight into the potential application of CLnA in functional foods.

Trans-palmitoleic acid (trans-9-C16:1, or trans-C16:1 n-7): Nutritional impacts, metabolism, origin, compositional data, analytical methods and chemical synthesis. A review

Since the early 2010s, dietary trans-palmitoleic acid (trans-9-hexadecenoic acid, trans-9-C16:1 in the Δ-nomenclature, trans-C16:1 n-7 in the Ω-nomenclature, TPA) has been epidemiologically associated with a lower risk of type 2 diabetes in humans. Thanks to these findings, TPA has become a nutrient of interest. However, there is a lot of unresolved crucial questions about this dietary fatty acid. Is TPA a natural trans fatty acid? What kind of foods ensures intakes in TPA? What about its metabolism? How does dietary TPA act to prevent type 2 diabetes? What are the biological mechanisms involved in this physiological effect? Clearly, it is high time to answer all these questions with the very first review specifically dedicated to this intriguing fatty acid. Aiming at getting an overview, we shall try to give an answer to all these questions, relying on appropriate and accurate scientific results. Briefly, this review underlines that TPA is indeed a natural trans fatty acid which is metabolically linked to other well-known natural trans fatty acids. Knowledge on physiological impacts of dietary TPA is limited so far to epidemiological data, awaiting for supplementation studies. In this multidisciplinary review, we also emphasize on methodological topics related to TPA, particularly when it comes to the quantification of TPA in foods and human plasma. As a conclusion, we highlight promising health benefits of dietary TPA; however, there is a strong lack in well-designed studies in both the nutritional and the analytical area.

Eighteen‑carbon trans fatty acids and inflammation in the context of atherosclerosis

Endothelial dysfunction is a pro-inflammatory state characterized by chronic activation of the endothelium, which leads to atherosclerosis and cardiovascular disease (CVD). Intake of trans fatty acids (TFAs) is associated with an increased risk of CVD. This risk is usually associated with industrial TFAs (iTFAs) rather than ruminant TFAs (rTFAs); however it is not clear how specific TFA isomers differ in their biological activity and mechanisms of action with regard to inflammation. Here we review the literature on 18‑carbon TFAs, including the research associating their intake or levels with CVD and studies relating 18‑carbon TFA exposure to modulation of inflammatory processes. The evidence associating iTFAs with CVD risk factors is fairly consistent and studies in humans usually show a relation between iTFAs and higher levels of inflammatory markers. In contrast, studies in humans, animals and in vitro suggest that rTFAs have null or mildly beneficial effects in cardiovascular health, metabolic parameters and inflammatory markers, although the evidence is not always consistent. More studies are needed to better identify the beneficial and detrimental effects of the different TFAs, including those with 18 carbons.

Fatty Acid Desaturase 3 (FADS3) Is a Specific ∆13-Desaturase of Ruminant trans-Vaccenic Acid

In mammalian species, the Fatty Acid Desaturase (FADS) gene cluster includes FADS1 (∆5-desaturase), FADS2 (∆6-desaturase), and a third gene member, named FADS3. According to its high degree of nucleotide sequence homology with both FADS1and FADS2, FADS3 was promptly suspected by researchers in the field to code for a new mammalian membrane-bound fatty acid desaturase. However, no catalytic activity was attributed to the FADS3 protein for a decade, until the rat FADS3 protein was shown in vitro to be able to catalyze the unexpected ∆13-desaturation of trans-vaccenic acid, producing the trans11,cis13-conjugated linoleic acid isomer. This review summarizes the recent investigations establishing the FADS3 enzyme as a reliable mammalian trans-vaccenate ∆13-desaturase in vivo and tries to identify further unresolved issues that need to be addressed.

Conversion of dietary trans-vaccenic acid to trans11,cis13-conjugated linoleic acid in the rat lactating mammary gland by Fatty Acid Desaturase 3-catalyzed methyl-end Δ13-desaturation

In vitro, the rat Fatty Acid Desaturase 3 (FADS3) gene was shown to code for an enzyme able to catalyze the unexpected Δ13-desaturation of trans-vaccenic acid, producing the trans11,cis13-conjugated linoleic acid (CLA) isomer. FADS3 may therefore be the first methyl-end trans-vaccenate Δ13-desaturase functionally characterized in mammals, but the proof of this concept is so far lacking in vivo. The present study therefore aimed at investigating further the putative in vivo synthesis of trans11,cis13-CLA from dietary trans-vaccenic acid in rodents. During one week of pregnancy and two weeks post-partum, Sprague-Dawley female rats were fed two diets either high (10.0% of fatty acids and 3.8% of energy intake) or low (0.4% of fatty acids and 0.2% of energy intake) in trans-vaccenic acid. The trans11,cis13-CLA was specifically detected, formally identified and reproducibly quantified (0.06% of total fatty acids) in the mammary gland phospholipids of lactating female rats fed the high trans-vaccenic acid-enriched diet. This result was consistent with FADS3 mRNA expression being significantly higher in the lactating mammary gland than in the liver. Although the apparent metabolic conversion is low, this physiological evidence demonstrates the existence of this new pathway described in the lactating mammary gland and establishes the FADS3 enzyme as a reliable mammalian trans-vaccenate Δ13-desaturase in vivo.

Milk fat components with potential anticancer activity-a review

During many years, the milk fat has been unfairly undervalued due to its association with higher levels of cardiovascular diseases, dyslipidaemia or obesity, among others. However, currently, this relationship is being re-evaluated because some of the dairy lipid components have been attributed potential health benefits. Due to this, and based on the increasing incidence of cancer in our society, this review work aims to discuss the state of the art concerning scientific evidence of milk lipid components and reported anticancer properties. Results from the in vitro and in vivo experiments suggest that specific fatty acids (FA) (as butyric acid and conjugated linoleic acid (CLA), among others), phospholipids and sphingolipids from milk globule membrane are potential anticarcinogenic agents. However, their mechanism of action remains still unclear due to limited and inconsistent findings in human studies.

Effects of quantitative feed restriction and sex on carcass traits, meat quality and meat lipid profile of Morada Nova lambs

BACKGROUND

An experiment was conducted to evaluate the effects of feed restriction (FR) and sex on the quantitative and qualitative carcass traits of Morada Nova lambs. Thirty-five animals with an initial body weight of 14.5 ± 0.89 kg and age of 120 d were used in a completely randomized study with a 3 × 3 factorial scheme consisting of three sexes (11 entire males, 12 castrated males and 12 females) and three levels of feeding (ad libitum - AL and 30% and 60% FR).

RESULTS

Entire males presented greater hot and cold carcass weights (P < 0.05), followed by castrated males and females. However, the hot carcass yield was higher for females and castrated males than for entire males. Luminosity values were influenced (P < 0.05) by sex, with entire males presenting higher values than castrated males and females. Females showed higher (P < 0.05) concentrations of linoleic acid and arachidonic acid in the meat of the longissimus thoracis muscle. The meat of animals submitted to AL intake and 30% FR showed similar (P > 0.05) concentrations, and the concentrations of palmitic acid, palmitoleic acid, stearic acid, oleic acid and conjugated linoleic acid were higher (P < 0.05) than those of animals with 60% FR. The meat of females had a higher ω6/ω3 ratio and lower h/H ratio, and females had greater levels of feeding. The meat of animals on the 60% FR diet had a greater ω6/ω3 ratio, lower h/H ratio and lower concentration of desirable fatty acids in addition to a greater atherogenicity index (AI) and thrombogenicity index (TI).

CONCLUSION

Lambs of different sexes had carcasses with different quantitative traits without total influence on the chemical and physical meat characteristics. The lipid profile of the meat was less favorable to consumer health when the animals were female or submitted to 60% feed restriction.

Trans-Fatty Acid-Stimulated Mammary Gland Growth in Ovariectomized Mice is Fatty Acid Type and Isomer Specific

We previously reported that the trans-18:2 fatty acid trans-10, cis-12 conjugated linoleic acid (t10,c12-CLA) stimulates mammary gland development independent of estrogen and its receptor. Given the negative consequences of dietary trans-fatty acids on various aspects of human health, we sought to establish whether other trans-fatty acids could similarly induce ovary-independent mammary gland growth in mice. Prepubertal BALB/cJ mice were ovariectomized at 21 days of age then were fed diets enriched with cis-9, trans-11 CLA (c9,t11-CLA), or mixtures of trans-18:1 fatty acids supplied by partially hydrogenated sunflower, safflower, or linseed oil. The resultant mammary phenotype was evaluated 3 weeks later and compared to the growth response elicited by t10,c12-CLA, or the defined control diet. Whereas partially hydrogenated safflower oil increased mammary gland weight, none of the partially hydrogenated vegetable oils promoted mammary ductal growth. Similarly, the c9,t11-CLA supplemented diet was without effect on mammary development. Taken together, our data emphasize a unique effect of t10,c12-CLA in stimulating estrogen-independent mammary gland growth manifest as increased mammary ductal area and elongation that was not recapitulated by c9,t11-CLA or the partially hydrogenated vegetable oil diets.

Effect of double-muscling in Belgian Blue young bulls on the intramuscular fatty acid composition with emphasis on conjugated linoleic acid and polyunsaturated fatty acids

The effect of double-muscling (DM) genotype (double-muscling, mh/mh; heterozygous, mh/+; normal, +/+) of Belgian Blue (BB) young bulls on the intramuscular fatty acid composition, in particular conjugated linoleic acid (CLA) and polyunsaturated fatty acids (PUFA) was examined in five different muscles. The relative fatty acid composition showed only minor differences between muscles within genotypes. However, the DM genotype had a large effect on both the intramuscular total fatty acid content and on the relative fatty acid composition. Across muscles, the mh/mh animals had a lower total fatty acid content compared with the +/+animals (907 v: 2656 mg/100 g muscle;P< 0·01) and a higher PUFA proportion in total fatty acids (27·5 v 11·3 g/100 g total fatty acids;P< 0001), resulting in a higher PUFA/saturated fatty acid ratio (0·55 v 0·18;P< 0·01) and a lower n-6/n-3 ratio (5·34 v. 6·17;P< 0·01). The heterozygous genotype was intermediate between the two homozygous genotypes. The relative CLA content was similar in the mh/mh and +/+ genotypes and approximated 0·4 to 0·5 g/100 g total fatty acids. From the data it is further suggested that differences in the metabolism of the n-3 and n-6 fatty acids could exist between DM genotypes.

Mucosal Interactions between Genetics, Diet, and Microbiome in Inflammatory Bowel Disease

Numerous reviews have discussed gut microbiota composition changes during inflammatory bowel diseases (IBD), particularly Crohn’s disease (CD). However, most studies address the observed effects by focusing on studying the univariate connection between disease and dietary-induced alterations to gut microbiota composition. The possibility that these effects may reflect a number of other interconnected (i.e., pantropic) mechanisms, activated in parallel, particularly concerning various bacterial metabolites, is in the process of being elucidated. Progress seems, however, hampered by various difficult-to-study factors interacting at the mucosal level. Here, we highlight some of such factors that merit consideration, namely: (1) the contribution of host genetics and diet in altering gut microbiome, and in turn, the crosstalk among secondary metabolic pathways; (2) the interdependence between the amount of dietary fat, the fatty acid composition, the effects of timing and route of administration on gut microbiota community, and the impact of microbiota-derived fatty acids; (3) the effect of diet on bile acid composition, and the modulator role of bile acids on the gut microbiota; (4) the impact of endogenous and exogenous intestinal micronutrients and metabolites; and (5) the need to consider food associated toxins and chemicals, which can introduce confounding immune modulating elements (e.g., antioxidant and phytochemicals in oils and proteins). These concepts, which are not mutually exclusive, are herein illustrated paying special emphasis on physiologically inter-related processes.

Low Dietary c9t11-Conjugated Linoleic Acid Intake from Dairy Fat or Supplements Reduces Inflammation in Collagen-Induced Arthritis

Dietary cis-9,trans-11 (c9t11) conjugated linoleic acid (CLA) fed at 0.5 % w/w was previously shown to attenuate inflammation in the murine collagen-induced (CA) arthritis model, and growing evidence implicates c9t11-CLA as a major anti-inflammatory component of dairy fat. To understand c9t11-CLA's contribution to dairy fat's anti-inflammatory action, the minimum amount of dietary c9t11-CLA needed to reduce inflammation must be determined. This study had two objectives: (1) determine the minimum dietary anti-inflammatory c9t11-CLA intake level in the CA model, and (2) compare this to anti-inflammatory effects of dairy fat (non-enriched, naturally c9t11-CLA-enriched, or c9t11-CLA-supplemented). Mice received the following dietary fat treatments (w/w) post arthritis onset: corn oil (6 % CO), 0.125, 0.25, 0.375, and 0.5 % c9t11-CLA, control butter (6 % CB), c9t11-enriched butter (6 % EB), or c9t11-CLA-supplemented butter (6 % SB, containing 0.2 % c9t11-CLA). Paw arthritic severity and pad swelling were scored and measured, respectively, over an 84-day study period. All c9t11-CLA and butter diets decreased the arthritic score (25-51 %, P < 0.01) and paw swelling (8-11 %, P < 0.01). Throughout the study, plasma tumor necrosis factor (TNFα) was elevated in CO-fed arthritic mice compared to non-arthritic (NA) mice but was reduced in 0.5 % c9t11-CLA- and EB-fed mice. Interleukin-1β and IL-6 were increased in arthritic CO-fed mice compared to NA mice but were reduced in 0.5 % c9t11-CLA- and EB-fed mice through day 42. In conclusion, 0.125 % c9t11-CLA reduced clinical arthritis as effectively as higher doses, and decreased arthritis in CB-fed mice suggested that the minimal anti-inflammatory levels of c9t11-CLA might be below 0.125 %.

Beef Fat Enriched with Polyunsaturated Fatty Acid Biohydrogenation Products Improves Insulin Sensitivity Without Altering Dyslipidemia in Insulin Resistant JCR:LA-cp Rats

The main dietary sources of trans fatty acids are partially hydrogenated vegetable oils (PHVO), and products derived from polyunsaturated fatty acid biohydrogenation (PUFA-BHP) in ruminants. Trans fatty acid intake has historically been associated with negative effects on health, generating an anti-trans fat campaign to reduce their consumption. The profiles and effects on health of PHVO and PUFA-BHP can, however, be quite different. Dairy products naturally enriched with vaccenic and rumenic acids have many purported health benefits, but the putative benefits of beef fat naturally enriched with PUFA-BHP have not been investigated. The objective of the present experiment was to determine the effects of beef peri-renal fat (PRF) with differing enrichments of PUFA-BHP on lipid and insulin metabolism in a rodent model of dyslipidemia and insulin resistance (JCR:LA-cp rat). The results showed that 6 weeks of diet supplementation with beef PRF naturally enriched due to flaxseed (FS-PRF) or sunflower-seed (SS-PRF) feeding to cattle significantly improved plasma fasting insulin levels and insulin sensitivity, postprandial insulin levels (only in the FS-PRF) without altering dyslipidemia. Moreover, FS-PRF but not SS-PRF attenuated adipose tissue accumulation. Therefore, enhancing levels of PUFA-BHP in beef PRF with FS feeding may be a useful approach to maximize the health-conferring value of beef-derived fats.

Advances in research on cis-9, trans-11 conjugated linoleic acid: a major functional conjugated linoleic acid isomer

Conjugated linoleic acid (CLA) consists of a group of positional and geometric conjugated isomers of linoleic acid. Since the identification of CLA as a factor that can inhibit mutagenesis and carcinogenesis, thousands of studies have been conducted in the last several decades. Among the many isomers discovered, cis-9, trans-11 CLA is the most intensively studied because of its multiple, isomer-specific effects in humans and animals. This paper provides an overview of the available data on cis-9, trans-11 CLA, including its isomer-specific effects, biosynthesis, in vivo/in vitro research models, quantification, and the factors influencing its content in ruminant products.

Trans-octadecenoic Acid Positional Isomers Have Different Accumulation and Catabolism Properties in Mice

Trans fatty acids (TFA) are considered risk factors for cardiovascular disease (CVD), while the details of distribution and metabolism of the individual isomers are not clear. Here we investigated the accumulation and catabolic rate of TFA positional isomers of octadecenoic acid (18:1) in mice. ICR mice were fed deuterium- and [1-(13)C] stable isotope-labeled trans-9-18:1 (9t-18:1*), trans-10-18:1 (10t-18:1*), or trans-11-18:1 (11t-18:1*) for 2 or 4 weeks, or a TFA mixture (9t-18:1*, 10t-18:1*, and 11t-18:1*) for 3 weeks. Analysis of whole-body tissues by gas chromatography-chemical ionization mass spectrometry revealed the highest 9t-18:1* levels in the heart. Significant differences in the accumulation of the respective trans-18:1 were observed in the heart and erythrocytes, where 9t- > 11t- > 10t-18:1*, but no significant difference was observed in the liver or white adipose tissue (WAT). Mice fed on 11t-18:1 demonstrated accumulation of endogenously synthesized conjugated linoleic acid in the liver, WAT, and heart, but any other metabolites were not found in other groups. Furthermore, we analyzed catabolic rates of single-dose-administered trans-18:1* isomers into [(13)C]-labeled CO2 using isotope-ratio mass spectrometry, and the 10t-18:1*catabolic rate was significantly higher than those of 9t- and 11t-18:1*. We found that the accumulation and catabolism of trans-18:1 positional isomers varied in these mice. Differential accumulation in tissues suggests that individual TFA positional isomers may play different roles in human health.

Modulation of inflammation and immunity by dietary conjugated linoleic acid

Conjugated linoleic acid (CLA) is a mixture of positional and geometric isomers of linoleic acid. This family of polyunsaturated fatty acids has drawn significant attention in the last three decades for its variety of biologically beneficial properties and health effects. CLA has been shown to exert various potent protective functions such as anti-inflammatory, anticarcinogenic, antiadipogenic, antidiabetic and antihypertensive properties in animal models of disease. Therefore, CLA represents a nutritional avenue to prevent lifestyle diseases or metabolic syndrome. Initially, the overall effects of CLA were thought to be the result of interactions between its two major isomers: cis-9, trans-11 and trans-10, cis-12. However, later evidence suggests that such physiological effects of CLA might be different between the isomers: t-10, c-12-CLA is thought to be anticarcinogenic, antiobesity and antidiabetic, whereas c-9, t-11-CLA is mainly anti-inflammatory. Although preclinical data support a benefit of CLA supplementation, human clinical findings have yet to show definitive evidence of a positive effect. The purpose of this review is to comprehensively summarize the mechanisms of action and anti-inflammatory properties of dietary CLA supplementation and evaluate the potential uses of CLA in human health and disease.

Ability of the gut microbiota to produce PUFA-derived bacterial metabolites: Proof of concept in germ-free versus conventionalized mice

SCOPE

The gut microbiota is able to modulate host physiology through the production of bioactive metabolites. Our recent studies suggest that changes in gut microbiota composition upon prebiotics supplementation alter tissue levels of PUFA-derived metabolites in mice. However, in vivo evidence that gut microbes produces PUFA-derived metabolites is lacking. This study aimed to decipher the contribution of gut microbes versus that of the host in PUFA-derived metabolite production.

METHODS AND RESULTS

To achieve this goal, we compared the proportion of PUFA-derived metabolites and the expression of fatty acid desaturases in germ-free (GF) and conventionalized (CONV) mice fed either a low fat or Western diet. Higher concentrations of PUFA-derived metabolites were found in the colonic contents of conventionalized mice (CONV) mice compared to GF mice. The abundance of these metabolites in host tissues was modulated by dietary treatments but not by microbial status. Although microbial status did significantly influence desaturase expression, no correlations between host enzymes and tissue PUFA-derived metabolite levels were observed.

CONCLUSION

Together, these results highlight the ability of the gut microbiota to produce PUFA-derived metabolites from dietary PUFA. However, microbial production of these metabolites in colonic contents is not necessarily associated with modifications of their concentration in host tissues.

Butter naturally enriched in cis-9, trans-11 CLA prevents hyperinsulinemia and increases both serum HDL cholesterol and triacylglycerol levels in rats

BACKGROUND

Evidence from in vitro and animal studies indicates that conjugated linoleic acid (CLA) possesses anti-diabetic properties, which appear to be attributed to cis-9, trans-11 CLA, the major CLA isomer in ruminant fat. However, there is a shortage of studies addressing CLA from natural source. The present study aimed to evaluate the effects of butter naturally enriched in cis-9, trans-11 CLA on parameters related to glucose tolerance, insulin sensitivity and dyslipidemia in rats.

METHODS

Forty male Wistar rats were randomly assigned to the following dietary treatments (n=10/group), for 60 days: 1) Normal fat-Soybean oil (NF-So): diet containing 4.0% soybean oil (SO); 2) High Fat-Control Butter (HF-Cb): diet containing 21.7% control butter and 2.3% SO; 3) High Fat-CLA enriched Butter (HF-CLAb): diet containing 21.7% cis-9, trans-11 CLA-enriched butter and 2.3% SO; and 4) High fat-Soybean oil (HF-So): diet containing 24.0% SO. HF-Cb and HF-CLAb diets contained 0.075% and 0.235% of cis-9, trans-11 CLA, respectively.

RESULTS

HF-CLAb-fed rats had lower serum insulin levels at fasting than those fed with the HF-Cb diet, while the PPARγ protein levels in adipose tissue was increased in HF-CLAb-fed rats compared to HF-Cb-fed rats. Furthermore, R-QUICK was lower in HF-Cb than in NF-So group, while no differences in R-QUICK were observed among NF-So, HF-CLAb and HF-So groups. Serum HDL cholesterol levels were higher in HF-CLAb-fed rats than in those fed NF-So, HF-Cb and HF-So diets, as well as higher in NF-So-fed rats than in HF-Cb and HF-So-fed rats. HF-CLAb, HF-Cb and HF-So diets reduced serum LDL cholesterol levels when compared to NF-So, whereas serum triacylglycerol levels were increased in HF-CLAb.

CONCLUSION

Feeding rats on a high-fat diet containing butter naturally enriched in cis-9, trans-11 CLA prevented hyperinsulinemia and increased HDL cholesterol, which could be associated with higher levels of cis-9, trans-11 CLA, vaccenic acid, oleic acid and lower levels of short and medium-chain saturated fatty acids from butter naturally modified compared to control butter. On the other hand CLA-enriched butter also increased serum triacylglycerol levels, which could be associated with concomitant increases in the content of trans-9 and trans-10 C18:1 isomers in the CLA-enriched butter.

Trans-vaccenate is Δ13-desaturated by FADS3 in rodents

Fatty acid desaturases play critical roles in regulating the biosynthesis of unsaturated fatty acids in all biological kingdoms. As opposed to plants, mammals are so far characterized by the absence of desaturases introducing additional double bonds at the methyl-end site of fatty acids. However, the function of the mammalian fatty acid desaturase 3 (FADS3) gene remains unknown. This gene is located within the FADS cluster and presents a high nucleotide sequence homology with FADS1 (Δ5-desaturase) and FADS2 (Δ6-desaturase). Here, we show that rat FADS3 displays no common Δ5-, Δ6- or Δ9-desaturase activity but is able to catalyze the unexpected Δ13-desaturation of trans-vaccenate. Although there is no standard for complete conclusive identification, structural characterization strongly suggests that the Δ11,13-conjugated linoleic acid (CLA) produced by FADS3 from trans-vaccenate is the trans11,cis13-CLA isomer. In rat hepatocytes, knockdown of FADS3 expression specifically reduces trans-vaccenate Δ13-desaturation. Evidence is presented that FADS3 is the first "methyl-end" fatty acid desaturase functionally characterized in mammals.

Current issues surrounding the definition of trans-fatty acids: implications for health, industry and food labels

The definition of trans-fatty acids (TFA) was established by the Codex Alimentarius to guide nutritional and legislative regulations to reduce TFA consumption. Currently, conjugated linoleic acid (CLA) is excluded from the TFA definition based on evidence (primarily preclinical studies) implying health benefits on weight management and cancer prevention. While the efficacy of CLA supplements remains inconsistent in randomised clinical trials, evidence has emerged to associate supplemental CLA with negative health outcomes, including increased subclinical inflammation and oxidative stress (particularly at high doses). This has resulted in concerns regarding the correctness of excluding CLA from the TFA definition. Here we review recent clinical and preclinical literature on health implications of CLA and ruminant TFA, and highlight several issues surrounding the current Codex definition of TFA and how it may influence interpretation for public health. We find that CLA derived from ruminant foods differ from commercial CLA supplements in their isomer composition/distribution, consumption level and bioactivity. We conclude that health concerns associated with the use of supplemental CLA do not repudiate the exclusion of all forms of CLA from the Codex TFA definition, particularly when using the definition for food-related purposes. Given the emerging differential bioactivity of TFA from industrial v. ruminant sources, we advocate that regional nutrition guidelines/policies should focus on eliminating industrial forms of trans-fat from processed foods as opposed to all TFA per se.

Implication of fermentable carbohydrates targeting the gut microbiota on conjugated linoleic acid production in high-fat-fed mice

In vitro experiments have shown that isolated human gut bacteria are able to metabolise PUFA into conjugated PUFA like conjugated linoleic acids (CLA). The hypothesis of the present paper was that high-fat (HF) diet feeding and supplementation with fermentable carbohydrates that have prebiotic properties modulate the in vivo production of CLA by the mouse gut microbiota. Mice were treated for 4 weeks as follows: control (CT) groups were fed a standard diet; HF groups were fed a HF diet rich in linoleic acid (18 : 2n-6); the third groups were fed with the HF diet supplemented with either inulin-type fructans (HF-ITF) or arabinoxylans (HF-Ax). HF diet feeding increased rumenic acid (cis-9,trans-11-18 : 2 CLA) content both in the caecal and liver tissues compared with the CT groups. ITF supplementation had no major effect compared with the HF diet whereas Ax supplementation increased further rumenic acid (cis-9,trans-11-18 : 2 CLA) in the caecal tissue. These differences between both prebiotics may be linked to the high fat-binding capacity of Ax that provides more substrates for bacterial metabolism and to differential modulation of the gut microbiota (specific increase in Roseburia spp. in HF-Ax v. HF). In conclusion, these experiments supply the proof of concept that the mouse gut microbiota produces CLA in vivo, with consequences on the level of CLA in the caecal and liver tissues. We postulate that the CLA-producing bacteria could be a mediator to consider in the metabolic effects of both HF diet feeding and prebiotic supplementation.

Conjugated linoleic acid synthesis-related protein proteasome subunit α 5 (PSMA5) is increased by vaccenic acid treatment in goat mammary tissue

This study was conducted to identify proteins associated with the endogenous synthesis of conjugated linoleic acid (CLA) from trans-vaccenic acid (TVA; trans-11 C18:1, a precursor for CLA endogenous synthesis) in mammary tissues. Six lactating goats were divided into 2 groups. One group was given an intravenous bolus injection of TVA (150mg) twice daily over 4 d; the other group received saline injections. Treatment with TVA increased the concentration of cis-9,trans-11 CLA and TVA in goat milk. Additionally, TVA treatment increased the expression of stearoyl-CoA desaturase (SCD) in mammary tissue. Using 2-dimensional gel electrophoresis and electrospray ionization quadrupole time-of-flight mass spectrometry, 3 proteins affected by infusions of TVA were identified. Proteasome (prosome, macropain) subunit α type 5 (PSMA5) was upregulated, whereas peroxiredoxin-1 and translationally controlled tumor protein 1 were downregulated in TVA-treated animals compared with the vehicle-injected controls. Only the effect of TVA on PSMA5 could be confirmed by Western blot analysis. To further explore the regulation of PSMA5 in mammary epithelial cells when TVA is converted into CLA, we used a differentiated bovine mammary epithelial cell line treated with TVA for 6h. Changes in cis-9,trans-11 CLA concentrations and mRNA expression patterns of both SCD and PSMA5 were monitored. The concentration of cis-9,trans-11 CLA increased after TVA treatment. The mRNA expression level of PSMA5 was significantly elevated to 6h, but SCD mRNA expression only increased in 2h after TVA treatment. These results indicate that PSMA5 is highly expressed in goat mammary tissue and bovine mammary epithelial cells when TVA is converted into CLA. Our data suggest that PSMA5 protein is associated with CLA biosynthesis in mammary tissue.

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

BACKGROUND

Conjugated 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 FINDINGS

Caco-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/SIGNIFICANCE

These 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.

Dietary conjugated linoleic acid isomers change the unsaturation degree of hepatic fatty acids in neutral lipids but not in polar lipids

The fatty acid composition of phospholipids plays a key role in the structural and functional properties of cellular membrane. In this study, it was hypothesized that conjugated linoleic acid (CLA) isomer supplementation changes the unsaturation degree of the fatty acids of neutral lipids (NLs) but not those of polar lipids (PLs). Thus, the main goal was to determine the pattern of fatty acid incorporation into hepatic PL and NL fractions. Wistar male rats were fed cis(c)9,trans(t)11 and t10,c12 CLA isomers, separately or as a mixture. Whereas the t10,c12 isomer incorporation in the PL fraction was similar when supplemented either individually or as a mixture, the c9,t11 isomer reached the highest values of incorporation when combined with t10,c12. In the PL fraction, the linoleic acid did not change; but the arachidonic acid decreased, especially in the rats given the mixture. Also in this fraction, the t10,c12 isomer, either separately or as a mixture, decreased the amounts of n-6 long-chain (LC) polyunsaturated fatty acids (PUFA) and increased those of the n-3 LC PUFA relative to the control. In the NL fraction, linoleic acid incorporation followed the diet composition, whereas the arachidonic acid was similar among treatments. Facing CLA isomer supplementation, the present study suggests that fatty acid incorporation into phospholipids, through the balance between n-6 and n-3 LC PUFA, is dependent upon maintaining the unsaturation degree of cellular membrane.

Fiber reduction and lipid enrichment in carotenoid-enriched distillers dried grain with solubles produced by secondary fermentation of Phaffia rhodozyma and Sporobolomyces roseus

Carotenoid-enriched distillers dried grain with solubles (DDGS) developed as a value-added animal feed to provide carotenoids from mono and mixed culture (Mx) fermentation of red yeasts Phaffia rhodozyma (PR) and Sporobolomyces roseus (SR) were evaluated for their nutritional composition and compared to the control (C) DDGS. Apart from providing carotenoids, all three fermentation treatments reduced fiber with best reduction of 77% in PR, enhanced crude fat with highest of 81% in Mx, and reduced protein, amino acids and nitrogen by 50% in PR. DDGS fiber reduction by 77% was achieved by P. rhodozyma in the absence of any pretreatment. Qualitative and quantitative differences in fatty acid profiles were seen among the treatments. Vaccenic acid, a monounsaturated fatty acid produced in SR and Mx fermentation, was absent in C and PR. All these nutritional modifications are highly desirable in different DDGS-based animal feeds and can be explored to obtain tailor-made feeds/feed blends for specific animal diets.

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

BACKGROUND

Conjugated 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).

METHODS

Twenty 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.

RESULTS

Fasting 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.

CONCLUSION

We 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.

Conjugated linoleic acid and inflammatory cell signalling

Conjugated linoleic acids (CLA) are a family of polyunsaturated fatty acids (PUFA), some isomers occurring naturally in beef and dairy products and others being formed as a result of bihydrogenation of vegetable oils to form margarine. Synthetic and natural sources of CLA may have beneficial effects in a range of inflammatory conditions including colitis, atherosclerosis, metabolic syndrome and rheumatoid arthritis. Most of the biological effects have been attributed to the cis9, trans11- (c9, t11-) and the trans10, cis12- (t10, c12-) isomers. Evidence suggests that c9, t11-CLA is responsible for the anti-inflammatory effect attributed to CLA while t10, t12-CLA appears to be responsible for anti-adipogenic effects. This review will focus on the effects of CLA on the inflammatory components associated with insulin resistance, atherosclerosis and Th1 mediated inflammatory disease, at a cellular, systemic and clinical level. Whist CLA may ameliorate certain aspects of the inflammatory response, particularly within cellular and animal models, the relevance of this has yet to be clarified within the context of human health.