Fed Fish Oil Research Articles

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.

Total substitution of fish oil by vegetable oils in Senegalese sole (Solea senegalensis) diets: effects on fish performance, biochemical composition, and expression of some glucocorticoid receptor-related genes

To study the substitution of fish oil by vegetable oils in fish diets, juveniles Senegalese sole (Solea senegalensis) were fed diets (56 % crude protein, 12 % crude lipid) containing either linseed (100LO) or soybean (100SO) oils in comparison with a 100 % fish oil-based diet (100FO) for 90 days. Samples of muscle, liver, and intestine were collected for biochemical analysis and for glucocorticoid receptor-related genes, including GR1 and GR2, and the associated heat shock proteins HSP70, HSP90AA, and HSP90AB. Besides, basal levels of plasma cortisol were also determined. After the feeding period, a stress test, consisting on 5 min of net chasing, was applied to a selected population of each dietary group. Total replacement of fish oil by vegetable oils did not induced changes in fish growth and performance, but affected fatty acid profile of muscle, liver, and intestine, reflecting those tissues the characteristic fatty acids of each type of dietary oil. A tendency to conserve the ARA/EPA ratio could be observed in the different tissues, despite of the level of these fatty acids in diet. Chasing stress induced an increase of muscle GR1 and a reduction in intestinal GR2 relative expressions at any of the experimental diets assayed. In liver, chasing stress induced an increase in both GR1 and GR2 gene expression in fish fed fish oil diets. Similarly, chasing stress induced an increase of muscle HSP70 and decrease of HSP90AB in liver at any of the experimental diet assayed. Besides, vegetable oils decreased the expression of HSP70 in intestine, being the relative expression of liver HSP90AA increased by the inclusion of linseed oil in the diet, at any of the experimental conditions assayed.

Effect of dietary fish oil supplementation on the exploratory activity, emotional status and spatial memory of the aged mouse lemur, a non-human primate

The data are inconsistent about the ability of dietary omega-3 fatty acids to prevent age-associated cognitive decline. Indeed, most clinical trials have failed to demonstrate a protective effect of omega-3 fatty acids against cognitive decline, and methodological issues are still under debate. In contrast to human studies, experiments performed in adult rodents clearly indicate that omega-3 fatty acids supplement can improve behavioural and cognitive functions. The inconsistent observations between human and rodent studies highlight the importance of the use of non-human primate models. The aim of the present study was to address the impact of omega-3 fatty acids (given in the form of dietary fish oil) on exploratory activity, emotional status and spatial reference memory in the aged mouse lemur, a non-human primate.Aged animals fed fish oil exhibited decreased exploratory activity, as manifested by an increase in the latency to move and a reduced distance travelled in an open-field. The fish oil-supplemented animals exhibited no change in the anxiety level, but they were more reactive to go into the dark arms of a light/dark plus-maze. In addition, we found that fish oil supplementation did not significantly improve the spatial memory performance in the Barnes maze task.This study demonstrated for the first time that a fish oil diet initiated late in life specifically modifies the exploratory behaviour without improving the spatial memory of aged non-human primates. Omega-3 fatty acid supplementation may be effective when started early in life but less effective when started at later ages.

Effects of dietary fat energy restriction and fish oil feeding on hepatic metabolic abnormalities and insulin resistance in KK mice with high-fat diet-induced obesity

We investigated the effects of dietary fat energy restriction and fish oil intake on glucose and lipid metabolism in female KK mice with high-fat (HF) diet-induced obesity. Mice were fed a lard/safflower oil (LSO50) diet consisting of 50 energy% (en%) lard/safflower oil as the fat source for 12 weeks. Then, the mice were fed various fat energy restriction (25 en% fat) diets — LSO, FO2.5, FO12.5 or FO25 — containing 0, 2.5, 12.5, or 25 en% fish oil, respectively, for 9 weeks. Conversion from a HF diet to each fat energy restriction diet significantly decreased final body weights and visceral and subcutaneous fat mass in all fat energy restriction groups, regardless of fish oil contents. Hepatic triglyceride and cholesterol levels markedly decreased in the FO12.5 and FO25 groups, but not in the LSO group. Although plasma insulin levels did not differ among groups, the blood glucose areas under the curve in the oral glucose tolerance test were significantly lower in the FO12.5 and FO25 groups. Real-time polymerase chain reaction analysis showed fatty acid synthase mRNA levels significantly decreased in the FO25 group, and stearoyl-CoA desaturase 1 mRNA levels markedly decreased in the FO12.5 and FO25 groups. These results demonstrate that body weight gains were suppressed by dietary fat energy restriction even in KK mice with HF diet-induced obesity. We also suggested that the combination of fat energy restriction and fish oil feeding decreased fat droplets and ameliorated hepatic hypertrophy and insulin resistance with suppression of de novo lipogenesis in these mice.

Dietary linoleic acid elevates endogenous 2-arachidonoylglycerol and anandamide in Atlantic salmon (Salmo salarL.) and mice, and induces weight gain and inflammation in mice

Dietary intake of linoleic acid (LA) has increased dramatically during the twentieth century and is associated with a greater prevalence of obesity. Vegetable oils are recognised as suitable alternatives to fish oil (FO) in feed for Atlantic salmon (Salmo salar L.) but introduce high amounts of LA in the salmon fillet. The effect on fish consumers of such a replacement remains to be elucidated. Here, we investigate the effect of excessive dietary LA from soyabean oil (SO) on endocannabinoid levels in Atlantic salmon and mice, and study the metabolic effects in mice when SO replaces FO in feed for Atlantic salmon. Atlantic salmon were fed FO and SO for 6 months, and the salmon fillet was used to produce feed for mice. Male C57BL/6J mice were fed diets of 35% of energy as fat based on FO- and SO-enriched salmon for 16 weeks. We found that replacing FO with SO in feed for Atlantic salmon increased LA, arachidonic acid (AA), decreased EPA and DHA, elevated the endocannabinoids 2-arachidonoylglycerol (2-AG) and anandamide (AEA), and increased TAG accumulation in the salmon liver. In mice, the SO salmon diet increased LA and AA and decreased EPA and DHA in the liver and erythrocyte phospholipids, and elevated 2-AG and AEA associated with increased feed efficiency, weight gain and adipose tissue inflammation compared with mice fed the FO salmon diet. In conclusion, excessive dietary LA elevates endocannabinoids in the liver of salmon and mice, and increases weight gain and counteracts the anti-inflammatory properties of EPA and DHA in mice.

Effects of fish oil and conjugated linoleic acids on carnitine homeostasis in laying hens

1. The effects of n−3 polyunsaturated fatty acids (PUFA) and conjugated linoleic acids (CLA) on genes involved in carnitine homeostasis were compared in laying hens. Three groups of laying hens were fed on a control diet or a diet with either 3% of fish oil or CLA for 4 weeks. 2. Feed intake and egg production rate did not differ between the three groups. Diets with fish oil or CLA had only a weak effect on mRNA levels of PPARα target genes (ACO, CPT-I) in the liver and did not influence mRNA concentrations of the most important carnitine transporter OCTN2, enzymes of involved in carnitine synthesis (TMLD, TMABA-DH, BBD) or concentrations of carnitine in plasma, liver and total egg contents. 3. Hens fed the CLA diet had lower concentrations of free and total carnitine in egg yolk but higher concentrations of carnitine in albumen than control hens (P < 0·05), whereas the amount of free and total carnitine in whole egg did not differ. 4. In conclusion, the study showed that feeding fish oil or CLA causes only a weak activation of PPARα in tissues of laying hens that probably explained the lack of effect on carnitine homeostasis. The results contrast with those in humans and mice that show a significant effect of synthetic PPARα agonists on carnitine homeostasis in humans and mice.

Performance, carcass traits, muscle fatty acid composition and meat sensory properties of male Mahabadi goat kids fed palm oil, soybean oil or fish oil

This study examined the effect of palm, soybean or fish oils on the performance, muscle fatty acid composition and meat quality of goat kids. Twenty-four male Mahabadi kids (BW=19.4±1.2kg) were divided into three groups according to liveweight and randomly allocated to one of three diets. Animals were fed ad libitum for 84days. Different dietary fat sources had no effect on performance and/or carcass quality attributes. The soybean oil diet decreased 16:0 and 18:0 concentrations and increased 18:2 and 18:3 and the ratio of PUFA/SFA in the muscle compared with other treatments. Fish oil feeding increased 20:5 n-3 and 22:6 n-3 concentrations and decreased the ratio of n-6/n-3 in the muscle. The results demonstrate that the use of fish oil is a nutritional strategy to improve the health claimable long-chain omega-3 fatty acid content and n-6/n-3 ratio in goat meat without changing the sensory properties or colour of meat.

Plant proteins and vegetable oil do not have detrimental effects on post-mortem muscle instrumental texture, sensory properties and nutritional value of gilthead seabream

A trial was undertaken to evaluate if the concomitant replacement of fishmeal and fish oil by vegetable ingredients affects fillet quality of gilthead seabream. Fish were fed either a fishmeal/fish oil diet, a fishmeal/vegetable oil diet, a plant protein/fish oil or a plant protein/vegetable oil diet over 70days. Dietary treatments had no effect on the muscle proximate composition and free amino acid profile. The n−3/n−6 PUFA ratio in fillets was higher in seabream fed fish oil based diets. Fishmeal and fish oil replacement did not affect instrumental texture parameters, but fish fed plant protein-rich diets showed higher fibre density and lower mean fibre diameter. Dietary lipid sources had no effect on sensory attributes, while protein source affected significantly the perception of typical odour and colour (white) of the fillets and succulence in the mouth, with seabream fed plant protein-rich diets receiving the highest scores.

Alteration of colonic stem cell gene signatures during the regenerative response to injury

Since aberrant wound healing and chronic inflammation can promote malignant transformation, we determined whether dietary bioactive fish oil (FO)-derived n−3 polyunsaturated fatty acids (n−3 PUFA) modulate stem cell kinetics in a colitis-wounding model. Lgr5-LacZ and Lgr5-EGFP-IRES-creERT2 mice were fed diets enriched with n−3 PUFA vs n−6 PUFA (control) and exposed to dextran sodium sulfate (DSS) for 5days in order to induce crypt damage and colitis throughout the colon. Stem cell number, cell proliferation, apoptosis, expression of stem cell (Lgr5, Sox9, Bmi1, Hopx, mTert, Ascl2, and DCAMKL-1) and inflammation (STAT3) markers were quantified. DSS treatment resulted in the ablation of Lgr5+ stem cells in the distal colon, concurrent with the loss of distal crypt structure and proliferating cells. Lgr5, Ascl2 and Hopx mRNA expression levels were decreased in damaged colonic mucosa. Lgr5+ stem cells reappeared at day 5 of DSS recovery, with normal levels attained by day 6 of recovery. There was no effect of diet on the recovery of stem cells. FO fed animals exhibited higher levels of phospho-STAT3 at all time points, consistent with a higher wounding by DSS in FO feeding. n−3 PUFA-fed mice exhibited a reduction in stem cell associated factors, Ascl2, Axin2 and EphB3. These results indicate that rapidly cycling Lgr5+ stem cells residing at position 1 in the colon epithelium are highly susceptible to DSS-induced damage and that dietary cues can impact stem cell regulatory networks.

Interactions between aquaculture and fisheries

Aquaculture is increasingly interacting with fisheries from a socio-economic perspective at the level of the global food market. In addition, since 36% of landings from fisheries are used for the production of fishmeal and fish oil, which are essential feed elements for many aquaculture species, another source of interaction is at the level of the aqua feed market. The relevance of the interactions between the two sectors is becoming more evident as the process of transition from fishing to farming has reached a pivotal point, with almost 50% of the fish food supply now coming from aquaculture. The analyses on aquaculture and fisheries interactions often result in diverging views. This paper reviews the main positions in the recent scientific literature, structuring the discussion along the following themes: food market interactions; comparison of resources use by means of Life Cycle Assessment; use of fishmeal and fish oil and aqua feed markets; impacts on small pelagic fish stocks; food security; technical substitution of fishmeal and fish oil with alternative ingredients. The review is not aimed at taking a definitive position in respect of these complex issues but rather at summarising the different scientific contributions and indicating possible areas for further research. Research on fisheries and aquaculture interactions is considered beneficial in terms of policy support especially now that the reform of European Common Fishery Policy is assigning greater relevance to the growth of aquaculture and to its role in terms of socio-economic development for coastal and rural communities. In a more global perspective, the understanding of interactions between aquaculture and fisheries is important to evaluate the respective contributions to food security goals and the implications in terms of environmental sustainability and resource use efficiency.

Improvement in the High-Fat Diet-Induced Dyslipidemia and Adiponectin Levels by Fish Oil Feeding Combined with Food Restriction in Obese KKAy Mice

The effect on weight reduction of fish oil combined with food restriction in comparison with that of beef tallow was investigated in high-fat diet-induced obese KKAy mice. Although the reduction of body and white adipose tissue weight was similar in the two groups, fish oil increased adiponectin levels in the plasma, improved dyslipidemia accompanied by suppression of lipid synthesis in the liver when compared with beef tallow.

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.

Fish oil positively regulates anabolic signalling alongside an increase in whole-body gluconeogenesis in ageing skeletal muscle

Fish oil, containing mainly long-chain n-3 polyunsaturated fatty acids (LCn-3PUFA), has been found to acutely stimulate protein synthesis and insulin-mediated glucose metabolism. However, the underlying mechanism and more prolonged effect of fish oil during ageing remain to be determined. Fish oil (EPAX6000; 49.6 % eicosapentaenoic acid, 50.4 % docosahexaenoic acid) or control oil (60 % olive, 40 % soy) supplementation was delivered, via chocolate-derived sweets, to rats for 8 weeks. Throughout the study, food intake and body weight were recorded and body composition was investigated using EchoMRI. During the last 40 min of a 6 h infusion, with labelled dextrose ([U-(13)C]glucose) and amino acids ([1-(13)C]phenylalanine), blood samples were collected to assess glucose and phenylalanine kinetics. Soleus and longissimus dorsi muscles were extracted for protein and mRNA analyses. Fish oil had no effect on food intake or body composition. An increased whole-body glucose turnover, mainly accounted for via an increase in endogenous glucose production, was observed with fish oil feeding. No effects on whole-body phenylalanine turnover were observed. In longissimus dorsi, fish oil augmented the phosphorylation of phosphoinositide 3-kinase (PI3K)([Tyr458]) (P = 0.04) and 70 kDa ribosomal protein S6 kinase (p70s6k)([Thr389]) (P = 0.04). There were no differences in protein kinase B (Akt)([Ser473]), mammalian target of rapamycin (mTOR)([Ser2448]), protein phosphatase 2A (PP2A) 56 kDa regulatory B subunit γ (PP2A-B56-γ), forkhead box containing proteins O-subclass 3a (FOX03a)([Ser253]) or inflammatory markers (Interleukin-6, Interleukin-1 β, tumour necrosis factor-α, and cyclooxygenase-2). Our data suggest that the fish oil may stimulate endogenous glucose production and increase anabolic signalling in ageing rats.

Protective effect of ω-3 polyunsaturated fatty acids (PUFAs) on sodium nitroprusside–induced nephrotoxicity and oxidative damage in rat kidney

Sodium nitroprusside (SNP) a nitric oxide (NO) donor has proven toxic effects. Dietary ω-3 polyunsaturated fatty acid (PUFA) has been shown to reduce the severity of numerous ailments. Present study examined whether intake of fish oil (FO)/flaxseed oil (FXO, Omega Nutrition, St Vancouver, Canada) would have protective effect against SNP-induced toxicity. Male Wistar rats (150 ± 10 g) were used in this study. Initially animals were divided into two groups: one fed on normal diet and the other on 15% FO/FXO for 15 days. On the 16th day, SNP (1.5 mg/kg body weight) was administered intraperitoneally for 7 days daily. After 7 days animals were killed, kidneys were harvested for further analysis. SNP induced nephrotoxicity by increasing serum creatinine and blood urea nitrogen, SNP significantly decreased malate dehydrogenase, glucose-6-phosphatase, fructose-1,6-bisphosphatase and malic enzyme but increased lactate dehydrogenase and glucose-6-phosphate dehydrogenase. Brush border membrane enzymes such as alkaline phosphatase, γ-glutamyl transpeptidase and leucine amino peptidase were also decreased. The activity of catalase and glutathione peroxidase decreased concomitantly with increased lipid peroxidation, indicating that the significant kidney damage has been inflicted by SNP. Feeding of FO and FXO with SNP ameliorated the changes in various parameters caused by SNP. The results of the present study suggest that ω-3 PUFA-enriched FO and FXO from seafoods and plant sources, respectively, are similarly effective in reducing SNP-induced nephrotoxicity and oxidative damage. Thus, vegetarians who cannot consume FO can have similar health benefits from plant-derived ω-3 PUFA.

Protective effect of ω-3 polyunsaturated fatty acids onL-arginine-induced nephrotoxicity and oxidative damage in rat kidney

L-Arginine (ARG), an essential amino acid, is the endogenous source of the deleterious nitric oxide. Dietary ω-3 polyunsaturated fatty acid (PUFA)-enriched fish oil (FO) has been shown to reduce the severity of certain types of cancers, cardiovascular disease, and renal disease. Present study examined whether feeding of FO/flaxseed oil (FXO) would have protective effect against ARG-induced nephrotoxicity. ARG-induced nephrotoxicity was recorded by increased serum creatinine and blood urea nitrogen. ARG significantly altered the activities of metabolic and brush border membrane (BBM) enzymes. ARG caused significant imbalances in the antioxidant system. These alterations were associated with increased lipid peroxidation (LPO) and altered antioxidant enzyme activities. Feeding of FO and FXO with ARG ameliorated the changes in various parameters caused by ARG. Nephrotoxicity parameters lowered and enzyme activities of carbohydrate metabolism, BBM and inorganic phosphate (32Pi) transport were improved to near control values. ARG-induced LPO declined and antioxidant defense mechanism was strengthened by both FO and FXO alike. The results of the present study suggest that ω-3 PUFA-enriched FO and FXO from seafoods and plant sources, respectively, are similarly effective in reducing ARG-induced nephrotoxicity and oxidative damage. Thus, vegetarians who cannot consume FO can have similar health benefits from plant-derived ω-3 PUFA.

Abstract 1635: Effect of dietary fish oil on rat colonic prostaglandin (PG) E2 metabolism

Abstract PGE2, an eicosanoid generated from arachidonic acid (AA) by the cyclooxygenase function of prostaglandin H synthases (PGHS)-1 and 2, has been linked to the risk of many cancers including colorectal carcinogenesis. Targeting colonic PGE2 homeostasis by utilizing nutritional products such as fish oil may reduce endogenous PGE2 that, in turn, may decrease subsequent inflammatory events that lead to carcinogenesis. Rats were fed high fat fish oil diets contained different ratios of eicosapentaenoic acid (EPA) and n-6 fatty acid. The colon was horizontally divided into three equal length transections, first (proximal end), second (transverse) and third (distal end). Enzymes involved in PGE2 metabolism (15-hydroxyprostaglandin dehydrogenase (15-PGDH) and PGE synthase (mPGES)) were measured using quantitative PCR and semi-quantitative Western Blotting. GC-MS analysis was performed to detect fatty acid levels in serum and colon. LC-MS/MS analysis was used to examine eicosanoid levels. Our results showed that the colonic epithelial mucosa contained less PGE2 per mg of protein than did the whole colon. Colonic PGE2 and several eicosanoids including 13-Hydroxyoctadecadienoic acid(13HODE), 5-Hydroxyeico-satetraenoic acid (5 HETE), 15-Hydroxyeicosatetraenoic acid (15 HETE) and 12-Hydroxyeicosatetraenoic acid (12 HETE) were distributed differentially in different part of the colon. Dietary fish oil intake increased tissue levels of EPA in the colon. PGHS-2 gene was affected the most by dietary fish oil among all the genes tested in normal colon. Fish oil dose-dependently decreased PGHS-2 mRNA expression in all three colon sections. mRNA expression of 15-PGDH was higher in the third colonic section than the first two sections; however it was not altered by dietary fish oil. In conclusion, different parts of the colon have different eicosanoid profiles. The decreases in PGE2 in normal colon observed with fish oil feeding do not appear to be related to expression of PGHS-1, mPGES and 15-PGDH but are most closely correlated with PGHS-2 despite that PGHS-2 levels are already low in the normal colon. These data support the concept of anatomic variability in colonic carcinogenesis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1635. doi:1538-7445.AM2012-1635

Fish oil induced hyperlipidemia and oxidative stress in BioF1B hamsters is attenuated by elderberry extract

We have previously reported fish oil induced hyperlipidemia in BioF1B hamsters compared with Golden Syrian (GS) hamsters. Elderberry (Sambucus nigra L.) extract is abundant in anthocyanins and is believed to exert cardioprotective effects primarily by virtue of its hypolipidemic and antioxidant potential. In the current study, high-fat fish oil feeding increased oxidative stress in BioF1B hamsters compared with GS hamsters; this increase was associated with increased levels of omega-3 polyunsaturated fatty acids in plasma and liver. We then investigated whether cosupplementation with anthocyanin-rich elderberry extract would reverse fish oil induced hyperlipidemia and reduce lipid peroxidation in BioF1B hamsters. Plasma and hepatic lipids decreased significantly when hamsters were fed diets containing elderberry extract along with fish oil. Both plasma and liver thiobarbituric acid reactive substances showed significant reductions upon cosupplementation with elderberry extract in fish oil fed BioF1B hamsters. Our findings demonstrate that cosupplementation with elderberry extract reverses hyperlipidemia and lipid peroxidation observed with dietary fish oil alone in BioF1B hamsters.

Effects of contaminated fish oil on aberrant crypt foci formation and colonic cell kinetics

Fish oil is a rich source of n‐3 polyunsaturated fatty acids, which are known to prevent colon cancer. However this message is confounded by Food Drug Administration warnings which state that consumption of certain types of fish should be restricted due to contaminants such as polychlorinated biphenyls (PCBs). Therefore, this study examined the effects of fish oil contaminated with PCB (4000ng/ml fat) as compared to regular fish oil on the risk factors of colon cancer including aberrant crypt foci (ACF) formation and colonic cell kinetics (cell proliferation and apoptosis). Thirty Sprague‐Dawley rats were divided into three groups and fed corn oil, fish oil, or contaminated fish oil (PCB) for nine weeks and injected with saline or azoxymethane (2 times at wk 3 and 4). Fish oil‐fed rats had a lowered number of ACF (P=0.013) and high multiplicity ACF (P=0.024) compared to the corn oil and contaminated fish oil groups. Fish oil feeding resulted in lower cell proliferation index than corn oil and PCB groups (P=0.009). Cell apoptosis was not significantly different amongst any of the groups. These results suggest that dietary fish oil protects against colon cancer by lowering the number of early preneoplastic lesions through the inhibition of cell proliferation. PCB contaminated fish oil reduced the beneficial effects of fish oil on colon carcinogenesis. Supported by CHNR08‐810, SDSU UGP and NUTR 302L class.

Effects of dietary iron supplementation on growth performance, fatty acid composition and fatty acid metabolism in rainbow trout (Oncorhynchus mykiss) fed vegetable oil based diets

The complete and successful replacement of fish oil in aquafeed without compromising fillet omega-3 long chain polyunsaturated fatty acid (n−3 LC-PUFA) concentrations has yet to be achieved. As means of overcoming this issue, the potential of in vivo n−3 LC-PUFA biosynthesis in cultured fish has been widely investigated and may permit the future economical and sustainable development of aquaculture. Two of the key enzymes involved in this process include the fatty acid Δ-6 and Δ-5 desaturases, where, in the terminal protein of each complex, iron is present in the active di-iron centres. To the best of authors' knowledge, no investigations have thus far been attempted to elucidate the potential roles of dietary iron on the fatty acid metabolism of cultured fish. In this study, graded inclusions of dietary iron were tested in rainbow trout fed vegetable oil based diets. This study generated preliminary evidence suggesting that dietary iron concentration can have a positive effect on LC-PUFA biosynthesis in fish and data are herein reported. In particular, dietary iron level was shown to affect the final n−3 LC-PUFA content of fish tissues and also to modulate the activity of fatty acid desaturase enzymes. This activity was insufficient to compensate for a diet lacking in LC-PUFA but does highlight potential strategies to maximise this activity in cultured fish fed fish oil free diets.

Effect of graded dietary fish oil supplementation on body composition and fillet fatty acid composition of pike (Esox luciusL.)

A feeding experiment was conducted on northern pike, Esox lucius L. (123.6±33.3 g initial body weight) applying graded dietary fish oil supplementation resulting three dietary fat levels (without supplementation: 6.2% fat and 11.7, 17.4% fat levels with supplementations) in a recirculation system. Feed consumption, feed efficiency and protein utilization of pike was not affected by the treatment. Whole body lipid content analysis showed that the composition of pike was significantly affected by the increasing level of fish oil supplementation, although no relationship was detected between the dietary and the fillet lipid content, as well as the protein content of fish bodies. High docosahexaenoic acid (DHA, C22:6n-3) proportions were found in the muscle lipids (groups fed fish oil supplementation), as compared to the dietary fatty acid compositions suggesting that with dietary fish oil supplementation the dietary precursors (mainly EPA) enable pike to convert long chain highly unsaturated fatty acids, esp...