Mice Fed Fish Oil Research Articles

Incorporation of Fatty Acids as a Biomarker of Dietary Intake and Source is Fatty Acid and Blood Fraction Specific in CD-1 Mice

Abstract Objectives Accurate biomarkers of fatty acid (FA) intake and source (e.g., diet-derived FA) are an important assessment tool to study the role of dietary fat quality on metabolic health. The purpose of this study was to assess the incorporation of unique, dietary FA from fish oil, echium oil, and dairy fat into the red blood cell membranes (RBCM), plasma phospholipids (PPL), and plasma cholesterol esters (PCE) of genetically-outbred CD-1 mice. Methods At one month of age, mice were assigned to one of four isocaloric diets consisting either of a control fat blend or the control fat blend supplemented (30%) with fish oil, echium oil, or dairy fat (n = 10/diet/sex). After 52 weeks of feeding, cardiac blood was collected for FA analysis of RBCM, PPL, and PCE using gas-liquid chromatography. Results Expectedly, a higher proportion of fish-derived FA (eicosapentaenoic acid and docosahexaenoic acid) was observed in the RBCM and PCE of fish oil-fed mice (P < 0.0001). Accordingly, a greater proportion of echium oil-derived γ-linolenic acid was incorporated into all blood fractions of echium oil-fed mice (P < 0.0001). Yet, stearidonic acid, specific to echium oil, was not detected in the RBCM of mice, and no differences in the proportion of stearidonic acid were found in the PPL and PCE. Odd-chain FA (pentadecanoic acid and heptadecanoic acid) were not exclusively enriched in the blood fractions of dairy-fed mice. Conversely, trans-palmitoleic acid, vaccenic acid, rumenic acid, and branched-chain FA were differentially incorporated into the PPL and PCE, while not detected in the RBCM. Conclusions In summary, unique, diet-derived FA are differentially incorporated into the blood fractions of mice, indicating that the incorporation of dietary FA into blood fractions is highly dependent upon the FA species. Therefore, diet-derived FA cannot be used universally as a reliable biomarker to validate dietary FA source in mice, rather, the specific FA and blood fraction must be carefully considered. Funding Sources Armin Grams Memorial Research Award, UVM Robert Larner, M.D. College of Medicine; USDA-NIFA Hatch Fund (accession number: 1,006,628).

Omega-3 fatty acids and ERPR(-) and HER2/neu(+/-) breast cancer prevention.

TPS1589 Background: The most aggressive breast cancer subtypes tend to be estrogen and progesterone receptor negative (ERPR(-)) and human epidermal growth factor receptor type 2 positive (HER2(+)). Women with these breast cancer subtypes (triple negative, ERPR(-)HER2(+)) tend to experience worse clinical outcomes and have a relatively higher risk of recurrence. Our previous research demonstrated that dietary omega-3 (n-3) fatty acids can significantly inhibit ERPR(-) HER2(+) tumorigenesis in MMTV-HER2/neu transgenic mice fed fish oil vs corn oil-based diets. The fish oil diet group developed 30% fewer breast tumors, had lower Ki67 expression, and experienced less mammary atypia relative to the corn oil diet group. Other studies involving diet, nutrition and breast cancer point to the potentially protective effect of an anti-inflammatory diet on the risk of developing ER(-) and HER2(+) breast cancer, further supporting the evidence that the ERPR(-), HER2(±) subtypes may be highly responsive to this bioactive nutrient. Methods: This is a double-blinded, randomized clinical trial of high dose (~5.4 g EPA+DHA) vs low dose (~0.9 g EPA+DHA in fatty acid mix of the typical American diet) of n-3 fatty acids in breast cancer survivors of ERPR(-), HER2(±) breast cancer. Eligible participants will take 5 capsules/day for 12 months, with cellular samples of breast epithelial and/or adipose tissue obtained by fine needle aspirations of the contralateral breast. The study aims to determine whether n-3 fatty acid supplementation will modify fatty acid metabolite content in breast adipose tissue, modulate cytomorphology and/or cell proliferation in breast epithelial cells, affect DNA methylation patterns, and modulate pro- vs anti-inflammatory gene expression patterns in breast adipose tissue. Correlative aims will evaluate possible associations between factors such as breast adipose tissue, red cell membrane fatty acid profiles, BMI, and reported dietary intake. Sample size of 40 participants per arm was calculated to provide at least 80% power to detect a statistically significant difference for each primary endpoint. This study focuses on women survivors of high risk breast cancer subtypes, specifically triple negative or ERPR(-)HER2(+) disease, who are currently without long term adjuvant options. Eligibility criteria include prior diagnosis of ERPR(-) stage 0 to III breast cancer, ≤5 years from completion of standard therapy.The study was closed to accrual in November 2018; less than 9 months of follow-up remain for active study participants. Clinical trial information: NCT02295059.

Dietary fish oil, and to a lesser extent the fat-1 transgene, increases astrocyte activation in response to intracerebroventricular amyloid-β 1–40 in mice

Objectives: Increases in astrocytes and one of their markers, glial fibrillary acidic protein (GFAP) have been reported in the brains of patients with Alzheimer’s disease (AD). N-3 polyunsaturated fatty acids (PUFA) modulate neuroinflammation in animal models; however, their effect on astrocytes is unclear.Methods: Fat-1 mice and their wildtype littermates were fed either a fish oil diet or a safflower oil diet deprived of n-3 PUFA. At 12 weeks, mice underwent intracerebroventricular infusion of amyloid-β 1-40. Astrocyte phenotype in the hippocampus was assessed at baseline and 10 days post-surgery using immunohistochemistry with various microscopy and image analysis techniques.Results: GFAP increased in all groups in response to amyloid-β, with a greater increase in fish oil-fed mice than either fat-1 or wildtype safflower oil-fed mice. Astrocytes in this group were also more hypertrophic, suggesting increased activation. Both fat-1- and fish oil-fed mice had greater increases in branch number and length in response to amyloid-β infusion than wildtype safflower animals.Conclusion: Fish oil feeding, and to a lesser extent the fat-1 transgene, enhances the astrocyte activation phenotype in response to amyloid-β 1-40. Astrocytes in mice fed fish oil were more activated in response to amyloid-β than in fat-1 mice despite similar levels of hippocampal n-3 PUFA, which suggests that other fatty acids or dietary factors contribute to this effect.

Fish oil feeding attenuates neuroinflammatory gene expression without concomitant changes in brain eicosanoids and docosanoids in a mouse model of Alzheimer’s disease

BackgroundNeuroinflammation is a recognized hallmark of Alzheimer’s disease, along with accumulation of amyloid-β plaques, neurofibrillary tangles and synaptic loss. n-3 polyunsaturated fatty acids (PUFA) and molecules derived from them, including eicosapentaenoic acid-derived eicosanoids and docosahexaenoic acid-derived docosanoids, are known to have both anti-inflammatory and pro-resolving properties, while human observational data links consumption of these fatty acids to a decreased risk of Alzheimer’s disease. Few studies have examined the neuroinflammation-modulating effects of n-3 PUFA feeding in an Alzheimer’s disease-related model, and none have investigated whether these effects are mediated by changes in brain eicosanoids and docosanoids. Here, we use both a fat-1 transgenic mouse and a fish oil feeding model to study the impact of increasing tissue n-3 PUFA on neuroinflammation and the production of pro-inflammatory and pro-resolving lipid mediators. MethodsFat-1 mice, transgenic animals that can convert n-6 to n-3 PUFA, and their wildtype littermates were fed diets containing either fish oil (high n-3 PUFA) or safflower oil (negligible n-3 PUFA) from weaning to 12 weeks. Animals then underwent intracerebroventricular infusion of either amyloid-β 1-40 or a control peptide. Hippocampi were collected from non-surgery and surgery animals 10 days after infusion. Microarray was used to measure enrichment of inflammation-associated gene categories and expression of genes involved in the synthesis of lipid mediators. Results were validated by real-time PCR in a separate cohort of animals. Lipid mediators were measured via liquid chromatography tandem mass spectrometry. ResultsFat-1 and wildtype mice fed fish oil had higher total hippocampal DHA than wildtype mice fed the safflower oil diet. The safflower-fed mice, but not the fat-1 or fish oil-fed mice, had significantly increased expression in gene ontology categories associated with inflammation in response to amyloid-β infusion. These effects were independent of changes in the expression of genes involved in the synthesis of eicosanoids or docosanoids in any group. Gene expression was replicated upon validation in the wildtype safflower and fish oil-fed, but not the fat-1 mice. Protectin, maresin and D and E series resolvins were not detected in any sample. There were no major differences in levels of other eicosanoids or docosanoids between any of the groups in response to amyloid-β infusion. ConclusionsFish oil feeding decreases neuroinflammatory gene expression in response to amyloid-β. Neither amyloid-β infusion or increasing brain DHA affects the brain concentrations of specialized pro-resolving mediators in this model, or the concentrations of most other eicosanoids and docosanoids.

Interaction between dietary lipids and gut microbiota regulates hepatic cholesterol metabolism

The gut microbiota influences many aspects of host metabolism. We have previously shown that the presence of a gut microbiota remodels lipid composition. Here we investigated how interaction between gut microbiota and dietary lipids regulates lipid composition in the liver and plasma, and gene expression in the liver. Germ-free and conventionally raised mice were fed a lard or fish oil diet for 11 weeks. We performed lipidomics analysis of the liver and serum and microarray analysis of the liver. As expected, most of the variation in the lipidomics dataset was induced by the diet, and abundance of most lipid classes differed between mice fed lard and fish oil. However, the gut microbiota also affected lipid composition. The gut microbiota increased hepatic levels of cholesterol and cholesteryl esters in mice fed lard, but not in mice fed fish oil. Serum levels of cholesterol and cholesteryl esters were not affected by the gut microbiota. Genes encoding enzymes involved in cholesterol biosynthesis were downregulated by the gut microbiota in mice fed lard and were expressed at a low level in mice fed fish oil independent of microbial status. In summary, we show that gut microbiota-induced regulation of hepatic cholesterol metabolism is dependent on dietary lipid composition.

Crosstalk between Gut Microbiota and Dietary Lipids Aggravates WAT Inflammation through TLR Signaling

SummaryDietary lipids may influence the abundance of circulating inflammatory microbial factors. Hence, inflammation in white adipose tissue (WAT) induced by dietary lipids may be partly dependent on their interaction with the gut microbiota. Here, we show that mice fed lard for 11 weeks have increased Toll-like receptor (TLR) activation and WAT inflammation and reduced insulin sensitivity compared with mice fed fish oil and that phenotypic differences between the dietary groups can be partly attributed to differences in microbiota composition. Trif−/− and Myd88−/− mice are protected against lard-induced WAT inflammation and impaired insulin sensitivity. Experiments in germ-free mice show that an interaction between gut microbiota and saturated lipids promotes WAT inflammation independent of adiposity. Finally, we demonstrate that the chemokine CCL2 contributes to microbiota-induced WAT inflammation in lard-fed mice. These results indicate that gut microbiota exacerbates metabolic inflammation through TLR signaling upon challenge with a diet rich in saturated lipids.

Mice fed fish oil diet and upregulation of brown adipose tissue thermogenic markers.

Fish oil (FO) elicits diverse beneficial effects. Reduction in or prevention of body mass (BM) gain in animal models may be associated with modulation of brown adipose tissue (BAT). We aimed to evaluate the effects of different high-fat diets with FO on BAT metabolism and thermogenic markers. C57BL/6 male mice (3-month-old) were fed different diets during 8 weeks: standard-chow diet (SC 10% fat), high-fat lard diet (HF-L 50% fat), high-fat lard plus FO diet (HF-L+FO 50% fat), and high-fat FO diet (HF-FO 50% fat). We evaluated BM and performed an oral glucose tolerance test. At euthanasia, plasma was collected for leptin, and triacylglycerol measurement and interscapular BAT was dissected and stored for molecular analyses. HF-L group showed elevated BM; glucose intolerance associated with diminished TC10 and GLUT4 expressions; hypertriglyceridemia associated with increased CD36 and diminished CPT1 expression; elevated expression of pro-inflammatory cytokines; and reduced PPAR expression. Furthermore, these animals showed hyperleptinemia with increased expression of thermogenic markers (beta3-AR, PGC1alpha, and UCP1). Conversely, HF-L+FO and HF-FO groups showed reduced BM gain with regularization of glucose tolerance and triglyceridemia, GLUT4, TC10, CD36, CPT1, and cytokines expressions. Both groups exhibited elevated PPAR and thermogenic markers expression in a dose-dependent way. FO improves metabolic profile and upregulates thermogenic markers, suggesting an elevated thermogenesis that leads to reduced BM gain.

The effects of fish oil consumption on cardiovascular remodeling in ApoE deficient mice

Owing to their spontaneous development of atherosclerosis, apolipoprotein E knockout mice (ApoE(KO)) are one of the best studied animal models for this disease. Little is known about the utility of various omega-3 fatty acid regimens, in particular fish oils, in preventing cardiac disease in ApoE(KO) mice. The purpose of this study was to determine the cardiovascular effects of omega-3 fatty acid supplementation with either safflower oil (control), fish oil, flaxseed oil, or designed oil in ApoE(KO) mice fed a high-fat diet for a total of 16 weeks. In-vivo cardiac function was assessed weekly using murine echocardiography. Blood pressure, plasma lipid levels, and brain natriuretic peptide (BNP) were serially measured. The results show that ApoE(KO) mice fed fish oil demonstrated an increase in left ventricular wall thickness as a result of increased afterload. Despite chronic treatment with fish oil over 16 weeks, blood pressure increased in ApoE(KO) mice by 20% compared with the baseline. Both echocardiographic evidence of left ventricular hypertrophy and biochemical increase in BNP levels confirmed diastolic dysfunction in ApoE(KO) mice fed fish oil. This suggests that high-fat diet supplemented with fish oil may lead to adverse cardiovascular effects in ApoE deficient mice.

Dendritic cell activation, phagocytosis and CD69 expression on cognate T cells are suppressed by n‐3 long‐chain polyunsaturated fatty acids

Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are bioactive n-3 long-chain polyunsaturated fatty acids (LCPUFAs) in fish oil that exert immunosuppressive effects. A significant amount of literature shows that n-3 LCPUFAs suppress dendritic cell (DC) function in vitro; however, few studies have determined if the effects are emulated at the animal level. In this study, we first focused on the functional consequences of 5% (weight/weight) fish oil on splenic CD11c(+) DCs. Administration of n-3 LCPUFAs, modelling human pharmacological intake (2% of total kcal from EPA,1·3% from DHA), to C57BL/6 mice for 3 weeks reduced DC surface expression of CD80 by 14% and tumour necrosis factor-α secretion by 29% upon lipopolysaccharide stimulation relative to a control diet. The n-3 LCPUFAs also significantly decreased CD11c(+) surface expression and phagocytosis by 12% compared with the control diet. Antigen presentation studies revealed a 22% decrease in CD69 surface expression on transgenic CD4(+) T lymphocytes activated by DCs from mice fed fish oil. We then determined if the functional changes were mechanistically associated with changes in lipid microdomain clustering or plasma membrane microviscosity with n-3 LCPUFAs, as reported for B and T lymphocytes. Fish oil administration to mice did not influence cholera-toxin induced lipid microdomain clustering or microviscosity, even though EPA and DHA levels were significantly elevated relative to the control diet. Overall, our data show that n-3 LCPUFAs exert immunosuppressive effects on DCs, validating in vitro studies. The results also show that DC microdomain clustering and microviscosity were not changed by the n-3 LCPUFA intervention used in this study.

Fish oil disrupts B cell MHC class II lateral organization in the murine immunological synapse

Fish oil enriched long chain n‐3 polyunsaturated fatty acids disrupts the lateral organization of proteins on the T cell side of the immunological synapse. However, the impact of fish oil on the antigen presenting cell side of the immunological synapse is unclear. We previously demonstrated that B cells isolated from mice fed fish oil suppressed B cell microdomain clustering as well as the ability to activate naïve CD4+ T cells through antigen presentation. In this study, using a combination of quantitative imaging methods, we tested the effect of fish oil on the lateral organization of B cell major histocompatibility complex (MHC) class II molecules involved in forming the immunological synapse. Fish oil had no impact on pre‐synaptic B cell MHC II clustering. However, fish oil did suppress the recruitment of MHC class II to the synapse. As a consequence, T cell PKCθ recruitment to the synapse was also diminished. The effects were independent of changes in B‐T cell adhesion. Finally, we compared the impact from fish oil to cholesterol depletion using methyl‐β‐cyclodextrin treatment and found similar results. Overall, the results reveal commonality in the mechanism by which fish oil manipulates protein lateral organization of B cells compared to T cells. Furthermore, the data establish MHC class II lateral organization on the B cell side of the immunological synapse as a novel molecular target of fish oil.NIH R15AT006122

Dietary oils modify the host immune response and colonic tissue damage followingCitrobacter rodentiuminfection in mice

Inflammatory bowel disease is an intestinal inflammatory disorder of multifactorial origin, in which diets that favor high n-6 and low n-3 fatty acids have been implicated. The present study addressed whether dietary n-6 and n-3 fatty acids alter colonic mucosal response to Citrobacter rodentium (C. rodentium) infection. Mice were fed diets identical except for fatty acids, with an energy percentage of 15% 18:2n-6 and <0.06% 18:3n-3, 4.2% 18:2n-6 and 1.9% 18:3n-3, or 1.44% 20:5n-3, 4.9% 22:6n-3, 0.32% 18:2n-6, and 0.12% 18:3n-3 from safflower, canola, or fish oil, respectively for 3 wk before infection. Dietary oils had no effect on colonic C. rodentium growth but altered colon 20:4n-6/(20:5n-3+22:6n-3) with 9.40 ± 0.06, 1.94 ± 0.08, and 0.32 ± 0.03% in colon phosphatidylcholine and 3.82 ± 0.18, 1.14 ± 0.02, and 0.30 ± 0.02% in phosphatidylethanolamine of mice fed safflower, canola, or fish oil, respectively. At 10 days postinfection, histological damage, F4/80-positive macrophages, and myeloperoxidase-positive neutrophils in colonic mucosa were higher in infected mice fed safflower than fish oil. Colon gene transcripts for macrophage inflammatory protein 2, keratinocyte cytokine, and monocyte chemoattractant protein 1 expression were significantly higher in infected mice fed safflower than canola or fish oil; IFN-γ, IL-6, and IL-17A expression were significantly elevated in mice fed safflower rather than fish oil; and IL-10 was significantly higher in mice fed fish oil rather than canola or safflower oil. This study demonstrates that oils high in 18:2n-6 with minimal n-3 fatty acids exacerbate mucosal immune response, whereas oils high in n-3 fatty acids attenuate mucosal immune response to C. rodentium. These studies implicate dietary oils as environmental modifiers of intestinal inflammation in response to infection.

The inhibition of early stages of HER‐2/neu‐mediated mammary carcinogenesis by dietary n‐3 PUFAs

We previously demonstrated that lifelong feeding of diets enriched in n-3 fatty acids such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) significantly inhibits HER-2/neu-mediated mammary tumorigenesis in mice. Of interest is whether dietary n-3 fatty acids exert effects at early stages of mammary carcinogenesis. Seven-week-old female MMTV-HER-2/neu transgenic mice were randomized to AIN-based semipurified diets containing either fish or corn oil at 25% energy. Mice were evaluated at 25, 30, and 35 weeks with analysis of mammary glands for atypical ductal hyperplasia (hematoxylin and eosin), cell proliferation (Ki67 immunostaining), and fatty acid synthase and cyclooxygenase-2 gene expression (qRT-PCR). Tissue fatty acid profiles were quantitated by GC. Atypia grade decreased significantly in mice fed fish oil (p = 0.002). Mammary epithelial cells in mammary glands from mice fed fish oil also had an eightfold lower percentage of Ki67 expression. COX-2 expression in mammary fat-pads significantly decreased in mice fed fish versus corn oil enriched diets. Dietary fish oil inhibits atypical ductal hyperplasia at early stages of HER-2/neu-mediated mammary carcinogenesis relative to corn oil diets. This histologic change is associated with suppression of mammary epithelial cell proliferation and decreased COX-2 expression in mammary tissue.

Omega-3 From Fish Oil Augments Gvhd Through the Enhancement of Chemotherapy Conditioning Regimen and Selective Foxp3 Depletion

AbstractAbstract 4671 Background:Omega-3 has been reported to enhance the effects of some cancer chemotherapeutic agents and to play a role in the immune system as immunoregulator and immunosuppressant. The effect of a diet rich in omega-3 during immunosuppressed states of anticancer treatment and on bone marrow transplantation (BMT) outcome is not well known. Aims:To study the effect of omega-3 on busulfan-cyclophosphamide (Bu-Cy) conditioning regimen. Moreover, to evaluate the effect of omega-3 on the outcome of BMT after Bu-Cy conditioning. Methods:We evaluated the effects of menhadenfish oil (omega-3 rich) on the myeloablative treatment with Bu-Cy as well as on the outcome of BMT in mice compared to the effects of a diet containing corn oil (omega-6 rich) or to standard chow.Animals were divided into three groups, Group 1, Group 2 and Group 3. In all the groups, female BALB/c mice, 8–12 weeks old, were randomly selected to receive a diet enriched with fish oil, a diet enriched with corn oil or standard chow. The mice were fed for two weeks prior to conditioning. Thereafter, all the mice were injected IP with 80 mg/kg busulfan (Bu) for four days (day –7 to day –4) followed by 200 mg/kg cyclophosphamide (Cy) for two days (days –3 and −2). The mice in groups 1 and 2 were killed on day 0 (the proposed day for transplantation) and spleen and femur bone marrow cells were harvested. Organs were analysed with flow cytometry to evaluate the lymphoid and myeloid cells phenotype. Also, regulatory T cell number and function were studied. Mice in Group 3 were transplanted on day 0 with allogeneic bone marrow cells from 8–12 weeks old male C57BL/6 mice (2.0 × 107 bone marrow cells and 3.0 × 107spleen cells). Results:Fish oil-enriched chow significantly suppressed the function (Figure 1) of CD4+CD25+FoxP3+ regulatory T (Treg) cells compared to standard chow and corn oil fed mice at day 0. However, the percentage of FoxP3+ cells was significantly elevated in mice fed corn oil compared to standard chow. In concert with myeloablative chemotherapy, fish oil enhanced the suppressive effect of Bu-Cy on CD11b+ myeloid and CD11c+CD86+ dendritic cell populations in the bone marrow and spleen compared to the other dietary groups.Recipient mice fed fish oil had lower survival after BMT (Figure 2). A higher survival was observed for corn oil-fed recipients, but this survival rate was still inferior to that of recipients fed standard chow. Feeding recipients omega-3 enriched diet was associated with a more pronounced acute graft versus host disease (aGVHD). BM and spleen from mice fed corn oil demonstrated lower chimerism. Conclusion:Fish oil enhances the immunosuppressive effect of the conditioning regimen (Bu-Cy) in mice. BMT recipients fed a diet rich in polyunsaturated fatty acids either have lower engraftment (corn oil) or react with a lethal aGVHD (fish oil) associated with a suppression of Treg cells. These findings may have clinical implications. PUFA supplementation should be reconsidered and caution is advised in patients undergoing stem cell transplantation. [Display omitted] [Display omitted] Disclosures:No relevant conflicts of interest to declare.

N-3 fatty acids and membrane microdomains: From model membranes to lymphocyte function

This article summarizes the author's research on fish oil derived n-3 fatty acids, plasma membrane organization and B cell function. We first cover basic model membrane studies that investigated how docosahexaenoic acid (DHA) targeted the organization of sphingolipid-cholesterol enriched lipid microdomains. A key finding here was that DHA had a relatively poor affinity for cholesterol. This work led to a model that predicted DHA acyl chains in cells would manipulate lipid-protein microdomain organization and thereby function. We then review how the predictions of the model were tested with B cells in vitro followed by experiments using mice fed fish oil. These studies reveal a highly complex picture on how n-3 fatty acids target lipid-protein organization and B cell function. Key findings are as follows: (1) n-3 fatty acids target not just the plasma membrane but also endomembrane organization; (2) DHA, but not eicosapentaenoic acid (EPA), disrupts microdomain spatial distribution (i.e. clustering), (3) DHA alters protein lateral organization and (4) changes in membrane organization are accompanied by functional effects on both innate and adaptive B cell function. Altogether, the research over the past 10 years has led to an evolution of the original model on how DHA reorganizes membrane microdomains. The work raises the intriguing possibility of testing the model at the human level to target health and disease.

Dietary Combination of Fish Oil and Taurine Decreases Fat Accumulation and Ameliorates Blood Glucose Levels in Type 2 Diabetic/Obese KK‐Ay Mice

n-3 Polyunsaturated fatty acids (PUFAs) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), and taurine are functional compounds abundantly present in seafoods. In this study, we examined the combined effects of EPA- and DHA-rich fish oil and taurine on white adipose tissue (WAT) weight and blood glucose levels in diabetic/obese KK-A(y) mice. After a 4-wk administration of experimental diets (soybean oil or fish oil, supplemented with 0%, 2%, or 4% taurine), the increase in WAT weight of the mice fed the "fish oil + 4% taurine" diet was significantly suppressed compared to the "soybean oil + 4% taurine" and "fish oil only" diets. Serum triglycerides, free fatty acids, and total cholesterol levels decreased by fish oil administration. In addition, fish oil and taurine increased the activity of acyl-CoA oxidase, which is the rate-limiting enzyme of peroxisomal β-oxidation, increased in the liver of KK-A(y) mice. The activity of fatty acid synthase decreased by fish oil diets. Furthermore, blood glucose and insulin levels were significantly lower in the mice fed fish oil than in the soybean oil-fed mice. In fish oil + 4% taurine group, hyperglycemia and hyperinsulinemia were effectively improved in KK-A(y) mice compared to the fish oil only groups. In particular, the combination of fish oil and taurine enhanced the glucose transporter 4 (GLUT4) distribution in the plasma membrane of muscle tissue. These results suggest that EPA- and DHA-rich fish oil, especially in combination with taurine, exhibits preventive effects on WAT weight gain and hyperglycemia in diabetic/obese KK-A(y) mice.

Dietary fish oil results in a microenvironment with high anti-inflammatory potential, but does not inhibit mice from mounting an effective immune response to Borrelia burgdorferi. (51.9)

Abstract Dietary fish oil is suggested to alleviate a variety of inflammatory disorders by altering eicosanoid production. However, the extent of changes resulting from a diet high in omega-3 fatty acids is unknown, and any benefits resulting from these changes are unsubstantiated. Several studies conclude that the lack of phenotypic effects of fish oil result from an inability to consume sufficient quantities for any benefits to be evident. We fed mice either a control diet containing 18% by weight soybean oil or fish oil and infected the mice with Borrelia burgdorferi in order to quantify changes in temporal eicosanoid production throughout the course of disease. Using a lipidomics approach, we detected dramatic temporal and compositional changes in the majority of the 103 eicosanoids monitored. LOX metabolites produced in fish oil-fed mice were primarily generated non-enzymatically, and arachidonic acid metabolism was shunted from PGE2 synthesis to PGD2 synthesis resulting in the production and accumulation of 15d-PGJ2. Despite the fact that the fish oil diet led to a highly anti-inflammatory microenvironment, mice were able to mount an immune response and clear infection as well as mice fed a control diet. This study confirms that a diet high in fish oil results in a microenvironment with high anti-inflammatory potential but does not necessarily affect the ability of the organism to mount an effective immune response to infection with Borrelia burgdorferi.

Dietary fish oil regulates gene expression of cholesterol and bile acid transporters in mice

Fish oil rich in n-3 polyunsaturated fatty acids is known to affect hepatic lipid metabolism. Several studies have demonstrated that fish oil may affect the bile acid metabolism as well as lipid metabolism, whereas only scarce data are available. The aim of this study was to investigate the effect of fish oil on the gene expression of the transporters and enzymes related to bile acid as well as lipid metabolism in the liver and small intestine. Seven-week old male C57BL/6 mice were fed diets enriched in 10% soybean oil or 10% fish oil for 4 weeks. After 4 weeks, blood, liver and small intestine were obtained. Hepatic mRNA expression of lipids (Abcg5/8, multidrug resistance gene product 2) and bile acids transporters (bile salt export pump, multidrug resistance associated protein 2 and 3, organic solute transporter α) was induced in fish oil-fed mice. Hepatic Cyp8b1, Cyp27a1 and bile acid CoA : amino acid N-acyltransferase were increased in fish oil-fed mice compared with soybean-oil fed mice. Besides, intestinal cholesterol (Abcg5/8) and bile acid transporters (multidrug resistance associated protein 2 and organic solute transporter α) were induced in fish oil-fed mice. Fish oil induced the expression of cholesterol and bile acid transporters not only in liver but in intestine. The upregulation of Abcg5/g8 by fish oil is caused by an increase in cellular 27-HOC through Cyp27a1 induction. The hepatic induction of bile acid synthesis through Cyp27a1 may upregulate expression of bile acid transporters in both organs.

The Protective and Recovery Effects of Fish Oil Supplementation on Cedar Pollen-Induced Allergic Reactions in Mice

Obesity is associated with the production of pro-inflammatory cytokines and therefore can lead to worsening of allergic reactions. Thus, there is cross-talk between obesity and allergic reactions. In this study, we investigated whether the anti-obesity action of fish oil supplementation is involved in the anti-allergic action also induced by fish oil. We observed attenuation of cedar pollen-induced IgE serum increases in two experimental protocols: 15% fish oil supplementation for 8 weeks, which attenuated body weight increases compared with 15% soybean supplementation, and 4% fish oil supplementation for 2 weeks, which did not affect body weight increases compared with 4% soybean or 4% lard supplementation. The former but not the latter protocol attenuated sneezing after pollen challenge. Gene expression of TNF-α and IL-13, a Th2 cytokine, was moderately reduced in the trachea and nasal mucosa in mice fed fish oil supple- ments. In a third protocol, fish oil was administered for up to 15 weeks after a cedar pollen sensitization and challenge-induced increase in IgE levels. These levels decreased following fish oil supplementation but were almost unaffected by soybean oil supplementation. Surprisingly, the IL-13 gene expression level in the nasal mucosa and trachea was higher in the fish oil group than in the soybean oil group. These results suggest that fish oil supplementation before, during, or after antigen sensitization and challenge in mice helped to reduce cedar pollen-induced allergic reactions in- dependent of its anti-obesity action. Fish oil supplementation can also exhibit pro- or anti-inflammatory action against IL-13 expression depending on the experimental protocol.

Long-term intake of fish oil increases oxidative stress and decreases lifespan in senescence-accelerated mice

Objective The effects of fish oil including ω-3 polyunsaturated fatty acids on aging and lifespan are not well understood. In this study, the influence of long-term ingestion of fish oil on lifespan was examined in senescence-accelerated (SAMP8) mice. Methods We investigated the effects of dietary fish oil on lifespan and on lipid composition and oxidative stress in plasma and liver in SAMP8 mice. Male mice were fed a fish oil diet (5% fish oil and 5% safflower oil) or a safflower oil diet (10% safflower oil) from 12 wk of age. Results The SAMP8 mice fed fish oil did not have a longer maximum lifespan and had a shorter average lifespan than mice fed safflower oil. To examine the mechanism underlying these results, the effects on oxidative stress of long-term ingestion of fish oil were also examined. SAMP8 mice fed fish oil for 28 wk showed strong oxidative stress that caused hyperoxidation of membrane phospholipids and a diminished antioxidant defense system due to a decrease in tocopherol compared with mice fed safflower oil. Conclusion These findings suggest that intake of fish oil increases oxidative stress, decreases cellular function, and causes organ dysfunction in SAMP8 mice, thereby promoting aging and shortening the lifespan of the mice.

Porcine peroxisome proliferator-activated receptor δ mediates the lipolytic effects of dietary fish oil to reduce body fat deposition1

Peroxisome proliferator-activated receptor delta promotes fatty acid catabolism and energy expenditure in skeletal muscle and adipose tissues. A ligand for PPARdelta is required to activate PPARdelta function. Polyunsaturated fatty acids are potential ligands for PPARdelta activation. The current experiment was designed to determine the potential for PUFA, particularly from dietary fish oil, to activate porcine PPARdelta in vivo. Transgenic mice were generated to overexpress porcine PPARdelta in the adipose tissue. Mice were fed a high-saturated fat (13% beef tallow), or high-unsaturated fat (13% fish oil) diet, or a diet containing 4 mg/kg of a PPARdelta ligand (L165041) for 4 mo. Compared with beef tallow feeding, fish oil feeding reduced fat mass and decreased (P < 0.05) plasma triacylglycerol and FFA concentrations in the transgenic mice. Adipose tissue expression of genes involved in adipogenesis (i.e., lipoprotein lipase and adipocyte fatty acid-binding protein) was decreased in transgenic mice fed fish oil or the PPARdelta ligand. In the same mice, expression of the lipolytic gene, hormone-sensitive lipase was increased (P < 0.05). Fish oil feeding also stimulated expression of genes participating in fatty acid oxidation in the liver of transgenic mice compared with wild-type mice. Overall, these results indicate that PUFA may serve as natural and effective regulators of lipid catabolism in vivo and many of these effects may be generated from activation of PPARdelta.