Dietary PUFA Research Articles

Maternal omega-3 fatty acid intake increases placental labyrinthine antioxidant capacity but does not protect against fetal growth restriction induced by placental ischaemia–reperfusion injury

Placental oxidative stress plays a key role in the pathophysiology of several placenta-related disorders. Oxidative stress occurs when excess reactive oxygen species (ROS) damages cellular components, an outcome limited by antioxidant enzymes; mitochondrial uncoupling protein 2 (UCP2) also limits ROS production. We recently reported that maternal dietary omega-3 polyunsaturated fatty acid (n-3 PUFA) supplementation reduced placental oxidative damage and enhanced fetal and placental growth in the rats. Here, we examined the effect of n-3 PUFAs on placental antioxidant defences and whether n-3 PUFA supplementation could prevent growth restriction induced by placental ischaemia-reperfusion (IR), a known inducer of oxidative stress. Rats were fed either standard or high-n-3 PUFA diets from day 1 of pregnancy. Placentas were collected on days 17 and 22 in untreated pregnancies (term=day 23) and at day 22 following IR treatment on day 17. Expression of several antioxidant enzyme genes (Sod1, Sod2, Sod3, Cat, Txn1 and Gpx3) and Ucp2 was measured by quantitative RT-PCR in the placental labyrinth zone (LZ) and junctional zone (JZ). Cytosolic superoxide dismutase (SOD), mitochondrial SOD and catalase (CAT) activities were also analyzed. Maternal n-3 PUFA supplementation increased LZ mRNA expression of Cat at both gestational days (2- and 1.5-fold respectively; P<0.01) and female Sod2 at day 22 (1.4-fold, P<0.01). Cytosolic SOD activity increased with n-3 PUFA supplementation at day 22 (1.3-fold, P<0.05). Sod1 and Txn1 expression decreased marginally (30 and 22%, P<0.05). JZ antioxidant defences were largely unaffected by diet. Despite increased LZ antioxidant defences, maternal n-3 PUFA supplementation did not protect against placental IR-induced growth restriction of the fetus and placental LZ.

Dietary fish oil and DHA down-regulate antigen-activated CD4+T-cells while promoting the formation of liquid-ordered mesodomains

We have demonstrated previously that n-3 PUFA endogenously produced by fat-1 transgenic mice regulate CD4+ T-cell function by affecting the formation of lipid rafts, liquid-ordered mesodomains in the plasma membrane. In the present study, we tested the effects of dietary sources of n-3 PUFA, i.e. fish oil (FO) or purified DHA, when compared with an n-6 PUFA-enriched maize oil control diet in DO11.10 T-cell receptor transgenic mice. Dietary n-3 PUFA were enriched in CD4+ T-cells, resulting in the increase of the n-3:n-6 ratio. Following antigen-specific CD4+ T-cell activation by B-lymphoma cells pulsed with the ovalbumin 323-339 peptide, the formation of liquid-ordered mesodomains at the immunological synapse relative to the whole CD4+ T-cell, as assessed by Laurdan labelling, was increased (P<0·05) in the FO-fed group. The FO diet also suppressed (P<0·05) the co-localisation of PKCθ with ganglioside GM1 (monosialotetrahexosylganglioside), a marker for lipid rafts, which is consistent with previous observations. In contrast, the DHA diet down-regulated (P<0·05) PKCθ signalling by moderately affecting the membrane liquid order at the immunological synapse, suggesting the potential contribution of the other major n-3 PUFA components of FO, including EPA.

Algal diets and natural xenobiotics impact energy allocation in cladocerans. II. Moina macrocopa and Moina micrura

In freshwater lakes, changing mineral and biochemical food qualities as well as exposure to natural xenobiotics, such as humic substances (HSs) are common challenges to life history traits of zooplankters. In this contribution, we tested the bottom-up effect of different food qualities alone and in concert with exposure to increasing HS concentrations in a clone of each Moina micrura (inhabitant of Brazilian coastal lagoons) and Moina macrocopa (invasive species). Carbon, nitrogen, and phosphorus contents, fatty acid (FA) and the amino acid (AA) patterns of three coccal green algae of the summer aspect in the lagoons were analyzed. All algae were deficient in P, differed in their content of α-linolenic acid (ALA), histidine, and arginine and were lacking long-chained polyunsaturated fatty acids (PUFAs >C18). M. micrura did not grow on Desmodesmus armatus . Maximal mean lifespan and total lifespan reproduction were achieved on Pseudokirchneriella subcapitata . M. macrocopa fed all algae offered. Multiple regressions showed that ALA triggered longevity and the P-content reproduction. Exposure to HSs revealed that M. micrura reduced either its lifespan on Monoraphidium minutum or its reproduction on P. subcapitata . Conversely in M. macrocopa , lifespan on M. minutum was extended by a factor of 1.7 and offspring numbers increased by 1.4 upon HS exposure. On D. armatus an originally very low reproductive output increased maximal by a factor 4.6. Relating HS-mediated lifespan and offspring modulations of the 1.08 mM exposure to food components, it appears that ALA controls lifespan modulation even under HS stress, whereas offspring modulation seems to be controlled by C and total AA content. This indicates that, upon HS exposure, the investment of energy in body maintenance or reproduction would depend at least partly on the biochemical composition of the food available. This also shows that even short-chained dietary PUFAs may play a major role in keeping lipid peroxidation low. A comparison of the two Moina species tested revealed that M. macrocopa has the capacity to outcompete M. micrura , since it had the greater clutch size, never reduced the reproductive output upon HS-exposure, and fed all diets offered.

PPARβ mRNA expression, reduced by n − 3 PUFA diet in mammary tumor, controls breast cancer cell growth

The effect of numerous anticancer drugs on breast cancer cell lines and rodent mammary tumors can be enhanced by a treatment with long-chain n−3 polyunsaturated fatty acids (n−3 PUFA) such as docosahexaenoic acid (DHA, 22:6n−3) which is a natural ligand of peroxisome proliferator-activated receptors (PPAR). In order to identify the PPAR regulating breast cancer cell growth, we tested the impact of siRNA, selected to suppress PPARα, PPARβ or PPARγ mRNA in MDA-MB-231 and MCF-7 breast cancer cell lines. The siPPARβ was the most effective to inhibit breast cancer cell growth in both cell lines. Using PPARα, PPARβ and PPARγ pharmacological antagonists, we showed that PPARβ regulated DHA-induced inhibition of growth in MDA-MB-231 and MCF-7 cells. In addition, the expressions of all 3 PPAR mRNA were co-regulated in both cell lines, upon treatments with siRNA or PPAR antagonists. PPAR mRNA expression was also examined in the NitrosoMethylUrea (NMU)-induced rat mammary tumor model. The expressions of PPARα and PPARβ mRNAs were correlated in the control group but not in the n−3 PUFA group in which the expression of PPARβ mRNA was reduced. Although PPARα expression was also increased in the n−3 PUFA-enriched diet group under docetaxel treatment, it is only the expression of PPARβ mRNA that correlated with the regression of mammary tumors: those that most regressed displayed the lowest PPARβ mRNA expression. Altogether, these data identify PPARβ as an important player capable of modulating other PPAR mRNA expressions, under DHA diet, for inhibiting breast cancer cell growth and mammary tumor growth.

Omega-3 and omega-6 PUFAs induce the same GPR120-mediated signalling events, but with different kinetics and intensity in Caco-2 cells

BackgroundOmega-3 PUFAs are known to have anti-inflammatory properties, and different mechanisms are involved. GPR120 is a G-protein coupled receptor that has recently received attention because of its anti-inflammatory signalling properties after binding omega-3 PUFAs. However, both omega-3 and omega-6 PUFAs are natural GPR120 ligands. The aim of this study was to study possible differences in GPR120-mediated signalling events after treatment with different long-chain PUFAs in intestinal epithelial cells. We also investigated possible GPR120-mediated anti-inflammatory effects of different long-chain PUFAs that may be relevant in the understanding of how dietary PUFAs influence inflammatory responses in inflammatory diseases such as IBD.MethodsWe used Caco-2 cells as a model system to study GPR120-mediated signalling events because we found this cell line to express GPR120, but not GPR40, another plasma membrane receptor for medium- and long chain fatty acids. Increase in cytosolic Ca2+concentration, activation of MAP kinase ERK1/2 and the inhibition of IL-1β induced NF-κB activity were studied to reveal potential differences in the activation of GPR120 by the omega-3 PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and the omega-6 PUFA arachidonic acid (AA).ResultsWe found that EPA, DHA and AA enhanced the cytosolic concentration of the second messenger Ca2+ with the same efficiency, but with different kinetics. Both omega-3 and omega-6 PUFAs activated MAP kinase ERK1/2, but differences regarding kinetics and intensity were also observed in this pathway. ERK1/2 activation was shown to be dependent upon EGFR and Raf-1. We further investigated the ability of EPA, DHA and AA to inhibit NF-κB activity in Caco-2 cells. All PUFAs tested were able to inhibit IL-1β induced breakdown of IκBα after binding to GPR120, but with different potency.ConclusionsOur results show that EPA, DHA and AA elicit the same signalling events, but with different kinetics and efficiency through GPR120 in Caco-2 cells. We show, for the first time, that both omega-3 and omega-6 PUFAs inhibit NF-κB activation in intestinal epithelial cells. Our results may be important for understanding how dietary PUFAs influence inflammatory processes relevant in delineating effects of PUFAs in the treatment of IBD.

Dietary PUFA Intervention Affects Fatty Acid- and Micronutrient Profiles of Beef and Related Beef Products.

The study investigated the dietary impact of 18:3n-3 vs. 18:2n-6 on fatty acid- and micronutrient concentration of beef muscle and the extent of diet- and processing-induced changes of lipid- and micronutrient concentrations of beef products made thereof (German Corned beef (GCB), tea sausage spread (TSS), scalded sausage (SS)). Beef and beef products were obtained from German Holstein bulls which either received a control diet consisting of maize silage and concentrate with soybean meal (41%), or an experimental diet of grass silage and concentrate plus rapeseed cake (12%) and linseed oil (3%). The study revealed that upon an 18:3n-3 vs. 18:2n-6 intervention the amounts of 18:3n-3, EPA and Σn-3 LC-PUFA were significantly increased by 2.6, 2.3 and 1.7 fold, respectively. Experimental diet significantly increased β-carotene contents, and the γ-tocopherol contents were decreased. During beef processing, n-3 PUFA from beef were found to be product-specifically transferred into the corresponding beef products. 18:3n-3 and Σn-3 LC-PUFA contents were found to be 1.4 and 1.5 times higher in GCB from grass silage- than maize silage-fed bulls. The trace element contents in GCB (iron, copper, zinc, selenium) were not affected by the diet; however γ-tocopherol contents were decreased by experimental diet. In conclusion, dietary n-3 PUFA were completely transferred into beef products unaffected by beef processing conditions.

Polyunsaturated Fatty Acids Modulate the Association between PIK3CA-KCNMB3 Genetic Variants and Insulin Resistance

BackgroundNeighboring genes PIK3CA and KCNMB3 are both important for insulin signaling and β-cell function, but their associations with glucose-related traits are unclear.ObjectiveThe objective was to examine associations of PIK3CA-KCNMB3 variants with glucose-related traits and potential interaction with dietary fat.DesignWe first investigated genetic associations and their modulation by dietary fat in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study (n = 820). Nine single-nucleotide polymorphisms (SNPs) were selected for analysis, covering more than 80% of the SNPs in the region. We then sought to replicate the findings in the Boston Puerto Rican Health Study (BPRHS) (n = 844).ResultsFor KCNMB3 missense mutation rs7645550, meta-analysis indicated that homeostasis model assessment of insulin resistance (HOMA-IR) was significantly lower in minor allele T homozygotes compared with major allele C carriers (pooled P-value = 0.004); for another SNP rs1183319, which is in moderate LD with rs7645550, minor allele G carriers had higher HOMA-IR compared with non-carriers in both populations (pooled P-value = 0.028). In GOLDN, rs7645550 T allele homozygotes had lower HOMA-IR only when dietary n-3: n-6 PUFA ratio was low (≤0.11, P = 0.001), but not when it was high (>0.11, P-interaction = 0.033). Similar interaction was observed between rs1183319 and n-3: n-6 PUFA ratio on HOMA-IR (P-interaction = 0.001) in GOLDN. Variance contribution analyses in GOLDN confirmed the genetic association and gene-diet interaction. In BPRHS, dietary n-3: n-6 PUFA ratio significantly modulated the association between rs1183319 and HbA1c (P-interaction = 0.034).Conclusion PIK3CA-KCNMB3 variants are associated with insulin resistance in populations of different ancestries, and are modified by dietary PUFA.

1. The anticonvulsant effects of n-3 PUFA: Animal studies

The omega-3 polyunsaturated acids (n-3 PUFA) show great promise as a therapy for epileptic seizures. There has been considerable confusion, however, in the animal data related to the n-3 PUFAs’ anticonvulsant effects. Our own recent work has clarified this confusion, and led to a simple, reproducible animal preparation in which to study the n-3 PUFAs’ mechanism(s) of action. We first attempted to replicate the studies of Yehuda et al. (1994), who had reported dramatic seizure suppression after 21 days of 40 mg/kg injections of the “SR 3” formula i.p in rats. In our replication, we found no effect at all at this dose (Taha et al., 2006). We therefore tested the higher dose of 200 mg/kg of the SR-3 mixture. At 200 mg/kg, we found a significant increase in PTZ seizure latency, although no change in severity (Taha et al., 2009). We subsequently tried acute administration of a single dose in rats, switching from SR 3 to docosahexaenoic acid (DHA). Injecting subcutaneously (s.c.), we found a significant elevation in PTZ-seizure latency following after a single injection (Taha et al., 2010). Our dose–response curves in this study, however, were “inverted U” shaped. In parallel studies, we tested dietary (p.o.) administration. Working in rats with chronically implanted electrodes, we found that dietary PUFAs elevated thresholds in both the cortex and the amygdala of rats. These effects, however, took several months to occur (Taha et al., in preparation). To simplify the kinetics, we have moved to intravenous (i.v.) injections of DHA (tail vein in rats). Our i.v. experiments have now shown anticonvulsant effects 5 min after injection and plasma concentrations that rise rapidly, plateau at 5 min, and drop to baseline a minute after infusion (Trepanier et al., in preparation). We have therefore finally evolved a preparation in which anticonvulsant effects and plasma concentrations parallel the known kinetics of DHA. This preparation will now allow a meaningful study of DHA’s mechanisms of anticonvulsant action.

Lower plasma DHA and EPA and their related oxylipins are potential contributors to vascular disease in hemodialysis patients

Hemodialysis patients (HDP) have high blood pressure compared to healthy controls and greater incidence of chronic inflammation, higher C‐reactive protein and risk for cardiovascular disease. Moreover, HDP patients typically demonstrate unusually low plasma n‐3 PUFA levels. The purpose of our investigation was to characterize the oxylipins and endocannabinoids in female HDP (55.5 ± 14.2 y, 8.1± 8.4 y on dialysis) and healthy matched controls (54.8 ± 5 y). Plasma was extracted and subsequently analyzed using ultra performance liquid chromatography followed by electrospray ionization and tandem mass spectrometry for oxylipins and endocannabinoids, while RBC and plasma lipid fatty acids were analyzed by GC. HDP showed lower EPA and family related oxylipids 5‐ and 12‐HEPE and 14–15‐ and 17,18‐DiHETE in plasma compared to controls. The potent n‐3 vasodilators 17(18)–EpETrE and 19(20)‐EpDPE were lower in the HDP compared to the controls raising the possibility that hypertension in HDP could in part be due to reduced peripheral vascular relaxation. Further, the levels of 2‐OG, 1‐LG and 2‐LG were higher in HDP compared to the healthy controls. Herein, we report novel findings on oxylipins and endocannabinoids in female HDP that demonstrate differences compared to controls. This research will provide new opportunities to evaluate the role of dietary PUFA in clinical disease in kidney dialysis patients.

Composition of Dietary Fat Source Shapes Gut Microbiota Architecture and Alters Host Inflammatory Mediators in Mouse Adipose Tissue

High‐fat diet consumption has a significant impact on the development of obesity and inflammation. Studies have shown that dietary factors alter gut microbiota resulting in metabolic and immunologic effects within the host through adipose tissue. The objective of this study is to address how consumption of specific high saturated (SFA) and polyunsaturated (PUFA) fat shapes the intestinal microbiota and how these changes affect adipose tissue‐mediated inflammation.Adult male C57Bl/6 mice were fed SFA and PUFA diets for four weeks. Body mass and food consumption data were collected weekly. Bacterial DNA from stool samples was extracted and analyzed by T‐RFLP and HiSeq methods. Adipose depots were excised and analyzed for lipogenic and inflammatory gene expression via qRT‐PCR.Mice fed high‐fat diets showed increased caloric consumption and weight gain compared to low‐fat fed mice. High‐fat diets also resulted in a dramatic shift in gut microbiota, stratifying based on the specific source of dietary fat. These changes led to significantly altered expression of inflammatory markers (MCP‐1, CD192, resistin, APN) in adipose depots.Collectively, our findings show that gut microbiota resulting from dietary modulation of fat source can influence inflammatory outcome and should be considered a potential therapeutic target to alleviate obesity‐induced inflammation.Grant Funding Source: T32 DK07074

High-Fat Fish Oil Diet Prevents Hypothalamic Inflammatory Profile in Rats

Whether PUFA diets affect inflammatory mediators in central and peripheral sites is not clear. We investigated the effect of high-fat PUFA diets on the expression of proteins involved in inflammatory pathways in hypothalamus, muscle, and liver. Male rats were fed for 2 months with either chow or high-fat diets enriched with either soy (n-6 PUFAs) or fish oil (n-3 PUFAs). The fish group had normal body weight, low serum NEFA, reduced hypothalamic levels of TNF-α, IL-6, and TRAF6, and increased levels of IL-10 receptor. In contrast, the soy group had increased body weight and hypothalamic levels of TRAF6 and NFκBp65. In muscle, the fish diet reduced TNF-α and IL-6 levels. Both PUFA diets increased muscle IL-10 levels and reduced liver TNF-α and IL-6 levels. The data showed that the high-fat soy diet induced activation of the hypothalamic NFκB inflammatory pathway, a feature predisposing to feeding and energy expenditure disturbances associated with the development of obesity. On the other hand, the high-fat fish diet improved the central and the peripheral inflammatory profile via reduction of intracellular inflammatory mediators, suggesting a protection against obesity.

Dietary omega-3 PUFA and health: Stearidonic acid-containing seed oils as effective and sustainable alternatives to traditional marine oils

The daily consumption of dietary omega-3 PUFA is recommended by governmental agencies in several countries and by a number of health organizations. The molecular mechanisms by which these dietary PUFA affect health involve the enrichment of cellular membranes with long-chain 20- and 22-carbon omega-3 PUFA that impacts tissues by altering membrane protein functions, cell signaling, and gene expression profiles. These changes are recognized to have health benefits in humans, especially relating to cardiovascular outcomes. Cellular membrane enrichment and health benefits are associated with the consumption of long-chain omega-3 PUFA found in marine oils, but are not generally linked with the consumption of alpha-linolenic acid, the 18-carbon omega-3 PUFA found in plant seed oils. However, the supply of omega-3 PUFA from marine sources is limited and may not be sustainable. New plant-derived sources of omega-3 PUFA like stearidonic acid-soy oil from genetically modified soybeans and Ahiflower oil from Buglossoides arvensis seeds that are enriched in the 18-carbon omega-3 PUFA stearidonic acid are being developed and show promise to become effective as well as sustainable sources of omega-3 PUFA. An example of changes in tissue lipid profiles associated with the consumption of Ahiflower oil is presented in a mouse feeding study.

Omega-3 Fatty Acid Supplementation Affects Selected Phospholipids in Peripheral White Blood Cells and in Plasma of Full-Sized and Miniature Mares

Dietary omega-3 fatty acids (n-3 PUFA), notably eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), impart health benefits in humans and animals. In horses, dietary n-3 PUFAs elevate EPA and DHA and may promote anti-inflammatory effects. No reports document effects of dietary n-3 PUFA on fatty acyl components of circulating and cellular phospholipids in horses nor whether responses to dietary n-3 PUFA are similar among horse breeds. Ten Quarter Horse and 10 American Miniature Horse mares were assigned to n-3 PUFA (64.4 mg· kg body weight [BW]−1·d−1) or control diet for 56 days. Blood was sampled at 0, 28, and 56 days. Apparent phospholipid molecular species from several classes (phosphatidylcholine [PC]; “ether-linked” phosphatidylcholine [i.e., alk(en)yl, acyl glycerophosphocholine] [ePC]; phosphatidylethanolamine [PE]; phosphatidylinositol [PI]; and phosphatidylserine [PS]) were determined in plasma and peripheral blood mononuclear cells (PBMC) by mass spectrometry. Statistical analysis showed that six phospholipid species had diet × day interactions (P < .05) for both plasma and PBMC. Further evaluation of these species demonstrated that the mole percentage of PC(38:6), PC(40:7), PC(42:10), PE(38:5), PE(40:6), and PE(40:7) (where x:y represents total acyl carbon:total carbon-carbon double bonds) in both plasma and PBMC phospholipids was elevated in horses fed n-3 PUFA (P < .001 for all). Analysis of the acyl product ions revealed that these contained an acyl chain of mass consistent with an n-3 PUFA. Thus, supplementation increased n-3 PUFA in selected plasma and PBMC phospholipids. The absence of breed effects suggests that miniature and full-size horses responded similarly to dietary treatment.

Maternal Dietary Omega-3 Fatty Acid Supplementation Reduces Placental Oxidative Stress and Increases Fetal and Placental Growth in the Rat1

Placental oxidative stress plays a key role in the pathophysiology of several placenta-related disorders including intrauterine growth restriction. Oxidative stress occurs when accumulation of reactive oxygen species damages DNA, proteins, and lipids, an outcome normally limited by antioxidant defenses. Dietary supplementation with omega-3 polyunsaturated fatty acids (n-3 PUFAs) may limit oxidative stress by increasing antioxidant capacity, but n-3 PUFAs are also highly susceptible to lipid peroxidation; so n-3 PUFA supplementation is potentially harmful. Here we examined the effect of n-3 PUFAs on placental oxidative stress and on placental and fetal growth in the rat. We also investigated whether diet-induced changes in maternal plasma fatty acid profiles are associated with comparable changes in placental and fetal tissues. Rats were fed either standard or high n-3 PUFA diets from Day 1 of pregnancy, and tissues were collected on Day 17 or 22 (term = Day 23). Dietary supplementation with n-3 PUFAs increased fetal (6%) and placental (12%) weights at Day 22, the latter attributable primarily to growth of the labyrinth zone (LZ). Increased LZ weight was accompanied by reduced LZ F(2)-isoprostanes (by 31% and 11% at Days 17 and 22, respectively), a marker of oxidative damage. Maternal plasma PUFA profiles were altered by dietary fatty acid intake and were strongly predictive of corresponding profiles in placental and fetal tissues. Our data indicate that n-3 PUFA supplementation reduces placental oxidative stress and enhances placental and fetal growth. Moreover, fatty acid profiles in the mother, placenta, and fetus are highly dependent on dietary fatty acid intake.

Omega-6 polyunsaturated fatty acids and the early origins of obesity

The incidence of obesity and its related metabolic disorders has increased significantly over the past 3 decades, culminating in the current global epidemic of metabolic disease and leading to the search for contributing factors. Exposure of the developing foetus/neonate to a typical Western diet increases their risk of obesity and metabolic disorders throughout the life-course, creating an intergenerational cycle of metabolic disease. In Western countries, this epidemic of metabolic disease has coincided with a marked increase in the intake of omega-6 polyunsaturated fatty acids (omega-6 PUFA), leading to suggestions that the two may be causally related. Recent studies have emphasized the proadipogenic properties of the omega-6 PUFA, and provided evidence that rodents fed on diets with omega-6 PUFA contents similar to the typical US diet (6-8% energy) have an increased fat mass. Importantly, recent studies have shown that perinatal exposure to a high omega-6 PUFA diet results in a progressive accumulation of body fat across generations. This review highlights the recent evidence supporting the role of the omega-6 PUFA in the early life origins of obesity and metabolic disease, the need for more clinical studies and the potential need for health agencies to re-evaluate current recommendations to further increase omega-6 PUFA intakes.

Diets rich inn-6 PUFA induce intestinal microbial dysbiosis in aged mice

Controversies have emerged regarding the beneficial v. detrimental effects of dietary n-6 PUFA. The alteration of the intestinal microbiota, a phenomenon termed dysbiosis, occurs during several chronic inflammatory diseases, but has not been well studied in an aged population. With present ‘Western’ diets predominantly composed of n-6 PUFA, we hypothesised that PUFA-rich diets cause intestinal dysbiosis in an aged population. C57BL/6 mice (aged 2 years) were fed a high-fat (40% energy), isoenergetic and isonitrogenous diet composed of rapeseed oil, maize oil or maize oil supplemented with fish oil. We examined ileal microbiota using fluorescence in situ hybridisation and stained tissues by immunofluorescence for the presence of immune cells and oxidative stress. We observed that feeding high-fat diets rich in n-6 PUFA promoted bacterial overgrowth but depleted microbes from the Bacteroidetes and Firmicutes phyla. This corresponded with increased body mass and infiltration of macrophages and neutrophils. Fish oil supplementation (rich in long-chain n-3 PUFA like DHA and EPA) restored the microbiota and inflammatory cell infiltration and promoted regulatory T-cell recruitment. However, fish oil supplementation was associated with increased oxidative stress, evident by the increased presence of 4-hydroxynonenal, a product of lipid peroxidation. These results suggest that an n-6 PUFA-rich diet can cause dysbiosis and intestinal inflammation in aged mice. However, while fish oil supplementation on an n-6 PUFA diet reverses dysbiosis, the combination of n-6 and n-3 PUFA, like DHA/EPA, leads to increased oxidative stress, which could exacerbate gastrointestinal disorders in the elderly.

How Selected Tissues of Lactating Holstein Cows Respond to Dietary Polyunsaturated Fatty Acid Supplementation

The effect of a 10-week supplementation with polyunsaturated fatty acids [via sunflower oil/DHA-rich algae (SUNA) or linseed oil/DHA-rich algae (LINA) enriched diets] versus saturated fatty acids (SAT) of lactating German Holstein dairy cows in mid-lactation on expression patterns of lipid metabolism-associated genes and gene products in hepatic, longissimus muscle and subcutaneous/perirenal/omental adipose tissue was assessed. Most pronounced transcriptomic responses to dietary PUFA were obtained in hepatic [down-regulated ACACA (FC=0.83, SUNA; FC=0.86, LINA), FADS1 (FC=0.60, SUNA; FC=0.72, LINA), FADS2 (FC=0.64, SUNA; FC=0.79, LINA), FASN (FC=0.64, SUNA; FC=0.72, LINA), SCD (FC=0.37, SUNA; FC=0.47, LINA) and SREBF1 (FC=0.79, SUNA, LINA) expression] and omental adipose [up-regulated ACACA (FC=1.58, SUNA; FC=1.22, LINA), ADFP (FC=1.33, SUNA; FC=1.32, LINA), CEBPA (FC=1.75, SUNA; FC=1.40, LINA), FASN (FC=1.57, SUNA; FC=1.21, LINA), LPL (FC=1.50, SUNA; FC=1.20, LINA), PPARG (FC=1.36, SUNA; FC=1.12, LINA), SCD (FC=1.41, SUNA; FC=1.17, LINA) and SREBF1 (FC=1.56, SUNA; FC=1.18, LINA) expression] tissue. Interestingly, gene/gene product associations were comparatively low in hepatic and omental adipose tissue compared with longissimus muscle, perirenal adipose and subcutaneous adipose tissue, indicating matches only in regard to minor concentrations of SCD product 18:1c9, FADS1 product 20:4n-6 and FADS2 product 18:3n-6 in hepatic tissue, and higher concentrations of ACACA and FASN gene products 12:0 and 14:0 and SCD product 18:2c9,t11 in omental adipose tissue. Whereas all analyzed tissues accumulated dietary PUFA and their ruminally generated biohydrogenation products, tissue-divergent preferences for certain fatty acids were identified. This descriptive study reports tissue-divergent effects of dietary PUFA and outlines the significance of a PUFA intervention with regard to dairy cows' nutritional management.

Mammary tumor development is directly inhibited by lifelong n-3 polyunsaturated fatty acids

IntroductionDespite the advocacy that diet may be a significant contributor to cancer prevention, there is a lack of direct evidence from epidemiological and experimental studies to substantiate such claims. Experimental studies suggest that n-3 polyunsaturated fatty acids (n-3 PUFA) from marine oils may reduce breast cancer risk, however, findings are equivocal. Thus, in this study, novel transgenic mouse models were employed to provide, for the first time, direct evidence for an anti-cancer role of n-3 PUFA in mammary tumorigenesis. Methodsfat-1 Mice, which are capable of endogenous n-3 PUFA synthesis, were bred with mouse mammary tumor virus (MMTV)-neu(ndl)-YD5 mice, an aggressive breast cancer model. The resultant offspring, including novel hybrid progeny, were assessed for tumor onset, size and multiplicity as well as n-3 PUFA composition in mammary gland and tumor tissue. A complementary group of MMTV-neu(ndl)-YD5 mice were fed n-3 PUFA in the diet. ResultsMice expressing MMTV-neu(ndl)-YD5 and fat-1 displayed significant (P<.05) reductions in tumor volume (~30%) and multiplicity (~33%), as well as reduced n-6 PUFA and enriched n-3 PUFA in tumor phospholipids relative to MMTV-neu(ndl)-YD5 control mice. The effect observed in hybrid progeny was similarly observed in n-3 PUFA diet fed mice. ConclusionUsing complementary genetic and conventional dietary approaches we provide, for the first time, unequivocal experimental evidence that n-3 PUFA is causally linked to tumor prevention.

Linoleic Acid Augments Oxidative Damage and Initiates Fibrosis in Cardiomyocytes and Fibroblasts

Cardiac fibrosis following the demise of cardiomyocytes is pivotal to cardiac remodeling and heart failure. Considering the rising rates of cardiovascular disease (CVD) and the preponderance of linoleic acid (LA) in the Canadian diet, we hypothesized that excess LA could initiate cell death and fibrosis in the heart. Four-month-old female C57/Bl6 mice were fed a high LA diet (HLA; corn oil rich) for 5 weeks, and a separate low LA diet group (LLA, canola oil rich) was kept as the isocaloric, isonitrogenous control. HLA feeding increased cardiac TUNEL positivity as amarker of cell death, protein expression of matrix metalloproteases (MMP-2 and -9) and downregulated tissue inhibitor of metalloproteases (TIMP-1 and -2). Sirius red and Masson's Trichrome staining of heart sections demonstrated augmented collagen deposition. Oxidative stress biomarkers such as nitrotyrosine and 4-hydroxynonenal also increased, whereas antioxidants including glutathione and superoxide dismutase were downregulated. To confirm that LA specifically plays a causative role, NIH-3T3 fibroblasts and differentiated H9c2 cardiomyoblasts were incubated with oleic, palmitic, or linoleic acid at concentrations from 0.1 to 1.0 mM over 24 hours. Mitochondrial redox potential in H9c2 cardiomyocytes was decreased with both palmitic acid and LA, but not oleic acid. Only incubation with LA demonstrated a dose-dependent reduction in cell viability in H9c2 cardiomyocytes. These results suggest that excess LA, a common dietary omega-6 PUFA, can augment cell death, oxidative damage, and loss of mitochondrial membrane potential in the heart and can contribute to current CVD rates in Canada.

Different Dietary Protein and PUFA Interventions Alter the Fatty Acid Concentrations, but Not the Meat Quality, of Porcine Muscle

The present study investigated the effect of a reduced protein diet in combination with different vegetable oils (sunflower seed oil or linseed oil) on carcass traits, meat quality and fatty acid profile in porcine muscle. Forty male Landrace pigs were allocated into four experimental groups (each n = 8) and one control group (n = 8) at a live weight of approximately 60 kg. The pigs were fed ad libitum from 60 kg to 100 kg live weight and restricted to 2.8 kg/day until they reached 120 kg. In contrast to other studies, the intramuscular fat content (IMF) did not increase in animals of groups fed a reduced protein diet and vegetable oils. The IMF ranged between 1.2% and 1.4%. The growth performance and meat quality of the longissimus muscle was not affected by the diet, but the average daily gain (ADG) and drip loss were affected. The muscle fatty acid concentrations were significantly affected by the diet, resulting in higher n-3 FA concentrations up to 113 mg/100 g muscle and lower n-6/n-3 PUFA ratio for pigs fed linseed oil-containing high- and reduced protein diets, compared to sunflower seed oil-containing diets.