Dietary Fish Oil Research Articles

Maternal fish oil consumption has a negative impact on mammary gland tumorigenesis in C3(1) Tag mice offspring.

Omega-3 fatty acids have been shown to reduce the incidence and slow the growth of mammary gland cancer in rodent models. Since exposure to dietary components during the critical developmental times of gestation and lactation may alter risk for mammary gland cancer in females, we tested whether exposure to increased levels of long-chain omega-3 fatty acids from fish oils would be preventive or promotional to mammary gland cancer in the offspring. Normal SV129 female mice were fed AIN 76 diets containing either 10% corn oil (control, 50% omega 6, n-6) or 5% of an omega-3 (n-3) fatty acid concentrate (fish oil 60% n-3) + 5% canola oil (10% n-3 + 20% n-6). Females were then mated with C(3)1 TAg transgenic mice. At weaning (3weeks), pups were randomized to either the corn (C) or fish oil (F) diet, 15-17 mice per group. Four experimental groups were generated: FF, FC, CF and CC. Tumor incidence and multiplicity were assessed at the following time points 120, 130 and 140days of age. A panel of genes encoding signal transduction proteins were analyzed in mammary glands at 130days. Mice never exposed to fish oil (CC group) had a significantly higher incidence and multiplicity of mammary gland tumors than mice exposed to fish oil throughout life (FF group). Mice exposed to fish oil during a portion of life (CF or FC) had intermediate tumor incidences and multiplicities. Results also indicate that maternal consumption of fish oil increased the expression of genes associated with immune system activation (Ccl20, Cd5, Il2, Lef1, Lta). Adequate omega-3 fatty acids in the maternal diet may reduce the risk for mammary gland cancer in the offspring. If humans make dietary change by consuming more omega-3 fat instead of corn oil with 0% omega 3 fat, breast cancer may be reduced in the next generation.

Short‐ and Long‐Term Effects of Dietary Supplementation with Fish Oil on Inflammatory Pain in Rats

Introduction Dietary supplementation with fish oil is promising as a complementary therapy for inflammatory pain. However, further studies are needed to support its therapeutic potential. For example, the antinociceptive effect of fish oil is widely suggested to be dependent on decreased prostaglandin E2 (PGE2) synthesis, but no previous study has investigated if it affects PGE2-induced nociceptive response. Similarly, beneficial long-term effects on inflammatory response are related to early exposure to fish oil, however, whether these effects include decreased inflammatory pain throughout life is not known. Objective The aim of this study was to investigate the short- and long-term effects of fish oil on inflammatory pain. Methods Dietary fish oil supplementation was performed through two protocols: in adult rats, during 20 days, or in dams, during pregnancy and lactation, with tests performed in adult offspring. The hyperalgesic response induced by carrageenan and its final mediators PGE2 and norepinephrine was used to model inflammatory pain. Results The findings demonstrated for the first time that dietary fish oil (1) decreases the hyperalgesia induced by carrageenan; (2) but not that induced by its final mediator PGE2 and norepinephrine; (3) increase omega-3 polyunsaturated fatty acids in peripheral neural tissue; and (4) attenuates inflammatory pain in individuals exposed to fish oil during pre-natal life and lactation. Conclusion Together, these findings support that fish oil decreases inflammatory pain either when consumed during adult life or during prenatal development. Future studies should confirm the therapeutic potential of fish oil in humans, which is essential for the development of public policies to encourage a fish oil richer diet.

Lipotoxicity dysregulates the immunoproteasome in podocytes and kidneys in type 2 diabetes.

Palmitic acid (PA) leads to lipotoxicity in type 2 diabetes and induces oxidative stress in podocytes. Oxidized cellular proteins are degraded by proteasomes. The role of proteasomes in PA- or oxidative stress-induced podocyte injury and pathogenesis of diabetic nephropathy (DN) is unknown. We investigated the effects of PA on expression of 20S and 26S proteasomes, proteasome activator 28 (PA28) regulators, and the immunoproteasome in cultured podocytes and renal cortical tissues of db/db and db/m mice using Western blot analysis. Glomerular areas and glomerular basement membrane (GBM) widths of db/db and db/m mice were examined using morphometry. Short-term incubation of PA or low levels of H2O2 upregulated only the immunoproteasome in cultured podocytes. Long-term exposure of podocytes to PA ultimately downregulated the immunoproteasome as with other proteasomes, whereas oleic acid (OA) or eicosapentaenoic acid (EPA) restored the PA-induced decreased protein levels. In db/db mice, renal cortical immunoproteasome expression with PA28α was significantly decreased compared with db/m mice, and glomerular areas and GBM widths were significantly increased compared with db/m mice. Feeding of an OA-rich olive oil or EPA-rich fish oil protected db/db mice against the reduced renal cortical immunoproteasome expression, glomerular enlargement, and GBM thickening. These results demonstrate that lipotoxicity downregulates the immunoproteasome in podocytes and kidneys in type 2 diabetes and that OA and EPA protected type 2 diabetic mice against decreased renal cortical immunoproteasome expression and the progression of DN. Given this, lipotoxicity-induced podocyte injury with impaired immunoproteasome expression appears to play an important role in the pathogenesis of DN.NEW & NOTEWORTHY In podocytes, PA rapidly induced immunoproteasome expression but ultimately decreased it, while OA and EPA restored the decreased immunoproteasome levels. In the renal cortex of type 2 diabetic mice, immunoproteasome expression was significantly decreased, whereas feeding of OA-rich olive oil or EPA-rich fish oil diets protected them against the reduced immunoproteasome expression and progression of diabetic nephropathy. Thus, lipotoxicity-induced podocyte injury with impaired immunoproteasome expression may be related to the pathogenesis of diabetic nephropathy.

Regulation of gene expression associated with LC‐PUFA metabolism in juvenile tambaqui ( Colossoma macropomum ) fed different dietary oil sources

Given the ecological unsustainability of using fish oil (FO) as the main source of long-chain polyunsaturated fatty acids (LC-PUFA), the investigation of alternative dietary LC-PUFA sources is crucial for aquaculture. Tambaqui (Colossoma macropomum) is a valuable economic aquaculture resource in Brazil, capable of endogenously elongating and desaturating linoleic (LA; 18:2n-6) and α-linolenic (ALA; 18:3n-3) acids to longer and physiologically vital LC-PUFA. Yet, it is unclear how this pathway is regulated by different oil sources in tambaqui. Thus, we designed an experiment with 2 different oil diets (fish oil—FO and vegetable oil—VO) at 2 different concentrations (5% or 10%) to investigate the molecular regulation of fatty acid biosynthesis in this species. We observed no differences in survival, body weight gain (BWG) and feed conversion ratio between the treatments. Gene expression analysis shows that fads2 and elovl5 are up-regulated in liver, while fads2 and elovl2 are up-regulated in brain of tambaqui fed with VO. The transcription factors pparβb and pparγ are also up-regulated in the brain by VO diet, when compared to FO diet. The VO diet also contributed to the biosynthesis of LC-PUFA in liver and specifically DHA in the brain. Overall, our approach shows that lipid metabolism-relevant genes are regulated by different dietary lipid sources.

Effects of different dietary lipid resources on sperm quality and reproductive success in rainbow trout ( Oncorhynchus mykiss )

The present study evaluated the effects of dietary fish oil replacement with linseed or sesame oil on sperm quality and reproductive performance in rainbow trout (Oncorhynchus mykiss) during a 7-month feeding trial. Male (≈ 970 g) broodfish were fed three isonitrogeneous and isolipidic formulated diets containing fish oil (FO diet), linseed oil (LO diet) and sesame oil (SO diet). Commercial trout broodfish diet was fed to another group to serve as control (CD). Growth performance was not affected by diet. Slight variations in volume, pH and density were recorded in the semen produced by rainbow trout subjected to the different dietary treatments (p > 0.05). Similarly, motility and kinematic parameters were not influenced by diets (p > 0.05). However, osmolality differed in the dietary groups, with semen from SO and LO fed fish having comparatively higher values (p < 0.05). Fatty acid (FA) profile of fish spermatozoa reflected dietary FA composition. FA profile of spermatozoa showed evidence of de novo biosynthesis of eicosapentaenoic acid, docosahexaenoic acid and arachidonic acid. Dietary treatments did not significantly affect reproductive performance (fertilization, eyeing and hatching rates). This may be suggestive of the ability of male rainbow trout to synthesize HUFA in vivo to meet their reproductive needs in the event of low dietary n-3 HUFA supplementation.

N-3 PUFAs protect against adiposity and fatty liver by promoting browning in postnatally overfed male rats: a role for NRG4

Early-life nutrition plays an important role in regulating adult metabolism. This study evaluated the effects of early nutrition during the suckling and postweaning periods on expression of the adipocytokine Neuregulin 4 (Nrg4) and its relationship with nonalcoholic fatty liver disease (NAFLD) in adulthood. In vivo, male rats were adjusted to litter sizes of three (small litter, SL) or ten (normal litter, NL) on postnatal day 3. Pups were fed control chow (NL and SL groups) or a high-fat diet (NL-HF and SL-HF groups), and SL pups specifically were fed a fish oil diet rich in n-3 polyunsaturated fatty acids (n-3 PUFAs) (SL-FO group), from postnatal weeks 3 to 13. The results demonstrated that postnatal overnutrition increased weight, hepatic de novo lipogenesis (DNL) gene expression and NAFLD and decreased body temperature and Nrg4, Ucp1 and Pgc1a mRNA expression in adipose tissues in SL, SL-HF and NL-HF rats compared to NL rats in adulthood. The opposite trends were observed in SL-FO rats. Moreover, in vitro, recombinant NRG4 protein reduced lipid accumulation by inhibiting DNL gene expression in fatty HepG2 cells stimulated with sodium oleate. In HPAs, eicosapentaenoic acid (EPA) treatment elevated NRG4 production and caused adipocyte browning, and these effects were abrogated by PPARG antagonism. In conclusion, a postweaning n-3 PUFA diet enhanced Nrg4 expression in adipose tissues, associated with attenuation of NAFLD induced by SL rearing. Additionally, external NRG4 reduced lipogenesis in steatotic hepatocytes. Thus, white adipose tissue browning induced by n-3 PUFAs may promote NRG4 production through the PPARG pathway.

Partial replacement of dietary fish oil by beef tallow does not impair antioxidant capacity and innate immunity of red swamp crayfish, Procambarus clarkii

Beef tallow (BT) has attracted research interests of fish oil (FO) sparing in aquafeed, but total replacement of dietary FO by BT might damage aquatic animal health as a controversial issue for years. This study aimed to investigate the effects of BT partially or completely replacing FO on the health of red swamp crayfish (Procambarus clarkii), especially antioxidant capacity and immune response. Three experimental diets containing FO, BT and a blend of FO and BT (FB, 1:1) as lipid sources, respectively, were formulated to feed crayfish for 8 weeks. The results showed crayfish exhibited no significant differences (p > 0.05) in growth and body proximate composition regardless of dietary lipids. Crayfish fed a BT diet were observed higher contents of haemolymph triglyceride and free fatty acid (FFA) compared with crayfish fed FO (p < 0.05), while FB diet tended to reverse this effect. For hepatopancreas antioxidants, crayfish in the FB group showed higher levels of catalase and glutathione and lower malondialdehyde content than those in the FO group (p < 0.05). Furthermore, BT diet feeding decreased the contents of haemolymph acid phosphatase, lysozyme and total protein compared with FO diet, but FB diet tended to improve these immunological parameters. FB inclusion reversed the BT-induced suppression of nuclear factor kappa beta mRNA expression and enhancement of mitochondrial manganese mRNA expression versus BT, implying ameliorative immunity function. Taken together, total replacement of dietary FO by BT might be detrimental to the health of crayfish, while partial substitution of dietary FO with BT neither suppresses growth nor impairs antioxidant capacity and innate immunity of crayfish.

Effects of High Levels of Dietary Linseed Oil on the Growth Performance, Antioxidant Capacity, Hepatic Lipid Metabolism, and Expression of Inflammatory Genes in Large Yellow Croaker (Larimichthys crocea).

A growth experiment was conducted to evaluate the effects of dietary fish oil (FO) replaced by linseed oil (LO) on the growth performance, antioxidant capacity, hepatic lipid metabolism, and expression of inflammatory genes in large yellow croaker (Larimichthys crocea). Fish (initial weight: 15.88 ± 0.14 g) were fed four experimental diets with 0% (the control), 33.3%, 66.7%, and 100% of FO replaced by LO. Each diet was randomly attributed to triplicate seawater floating cages (1.0 × 1.0 × 2.0 m) with 60 fish in each cage. Results showed that the growth performance of fish fed the diet with 100% LO was markedly decreased compared with the control group (P < 0.05), while no remarkable difference was observed in the growth performance of fish fed diets within 66.7% LO (P > 0.05). The percentage of 18:3n-3 was the highest in the liver and muscle of fish fed the diet with 100% LO among the four treatments. When dietary FO was entirely replaced by LO, fish had a markedly higher total cholesterol, total triglyceride, low-density lipoprotein cholesterol content, and alanine transaminase activity in the serum than the control group (P < 0.05). The concentration of malondialdehyde was markedly higher, while the activity of catalase was markedly lower in fish fed the diet with 100% LO than the control group (P < 0.05). When dietary FO was entirely replaced by LO, hepatic lipid content, transcriptional levels of fatp1 and cd36, and CD36 protein expression were significantly higher, while transcriptional level of cpt-1 and CPT-1 protein expression were significantly lower than the control group (P < 0.05). As for the gene expression of cytokines, fish fed the diet with 100% LO had markedly higher transcriptional levels of il-1β, tnfα, and il-6 than the control group (P < 0.05). In conclusion, the substitution of 66.7% FO with LO had no significant effects on the growth performance of fish, while 100% LO decreased the growth performance and increased the inflammation and hepatic lipid content of fish. The increase of hepatic lipid content was probably due to the increased fatty acid uptake and decreased fatty acid oxidation in fish.

Dietary manipulation of vulnerability to traumatic brain injury-induced neuronal plasma membrane permeability

Traumatic brain injury (TBI) can produce physical disruptions in the plasma membranes of neurons, referred to as mechanoporation, which lead to increased cell permeability. We suspect that such trauma-induced membrane disruptions may be influenced by the physical properties of the plasma membrane, such as elasticity or rigidity. These membrane properties are influenced by lipid composition, which can be modulated via diet, leading to the intriguing possibility of prophylactically altering diet to confer resiliency to this mechanism of acute neuronal damage in TBI. In this proof-of-concept study, we used three different diets—one high in polyunsaturated fatty acids suggested to increase elasticity (Fish Oil), one high in saturated fatty acids and cholesterol suggested to increase rigidity (High Fat), and one standard rat chow (Control)—to alter brain plasma membrane lipid composition before subjecting rats to lateral fluid percussion injury (FPI). Lipid analysis (n = 12 rats) confirmed that diets altered brain fatty acid composition after 4 weeks of feeding, with the Fish Oil diet increasing unsaturated fatty acids, and interestingly, the High Fat diet increasing omega-6 docosapentaenoic acid. One cohort of animals (n = 34 rats) was assessed immediately after FPI or sham injury for acute changes in neuronal membrane permeability in the injury-adjacent cortex. Surprisingly, sham animals fed Fish Oil had increased membrane permeability, suggesting altered passive membrane properties. In contrast, injured animals fed the High Fat diet displayed less intense uptake of permeability marker, suggesting a reduced extent of injury-induced plasma membrane disruption, although the density of affected cells matched the other diet groups. In a separate cohort survived for 7 days after FPI (n = 48 rats), animals fed the High Fat diet exhibited a reduced lesion area. At both time points there were no statistically significant differences in inflammation. Unexpectedly, these results indicate that the High Fat diet, as opposed to the Fish Oil diet, beneficially modulated acute plasma membrane permeability and resulted in a smaller lesion size at 7 days post-injury. Additional studies are necessary to determine the impact of these various diets on behavioral outcomes post-TBI. Further investigation is also needed to understand the physical properties in neuronal plasma membranes that may underlie increased resiliency to trauma-induced disruptions and, importantly, to understand how these properties may be influenced by targeted dietary modifications for vulnerable populations.

Effects of dietary fish oil replacement by poppy seed oil on growth performance and fillet quality of rainbow trout (Oncorhynchus mykiss)

Rainbow trout (Oncorhynchus mykiss) were fed replacement of fish oil with diets including poppy seed oil (PSO; 0%, 50% and 100%). At the end of the 90-day feeding period, the water holding capacity of the fillets decreased when the storage time increased. The colour and pH values were affected by both storage and diets. The hardness, springiness, gumminess and chewiness index of the fillet samples decreased as a consequence of increasing storage time, whereas the cohesiveness values of the fillets increased. The addition of PSO increased unsaturated fatty acids and reduced saturated fatty acids in the fatty acid composition of the fillets. These results demonstrated that the fatty acid (FA) composition of the rainbow trout fillets was reflecting the FA composition of dietary treatments and oils sources. The total mesophilic and psychrophilic bacteria count of the fish oil (FO), poppy seed oil/fish oil (PSO/FO) and poppy seed oil (PSO) samples was found within the legal limit on the third day of storage; however, it was found above the legal limits on the fifth day of storage. The sensory evaluation results showed that the fish fed with PSO diet were found to be non-desirable. The results of the study suggested that the blend of 50% fish oil and 50% poppy seed oil could be used as a replacer of fish oil in diets for rainbow trout to obtained the best growth performance, fillet quality and storage conditions.

Effect of Differently Fed Farmed Gilthead Sea Bream Consumption on Platelet Aggregation and Circulating Haemostatic Markers among Apparently Healthy Adults: A Double-Blind Randomized Crossover Trial.

Fish consumption beneficially affects coagulation markers. Few dietary intervention studies have investigated differently fed farmed fish against these cardio-metabolic risk factors in humans. This double-blind randomized crossover trial evaluated differently fed farmed gilthead sea bream consumption against platelet aggregation and circulating haemostatic markers among apparently healthy adults. Subjects aged 30–65 years, with a body mass index 24.0–31.0 kg/m2, consuming less than 150 g cooked fish per week, were recruited in Attica, Greece. Participants were randomized (n = 38, 1:1) to one of two sequences; consumption of fish fed with fish oil diet (conventional fish, CF)/fish fed with olive pomace-enriched diet (enriched fish, EF) versus EF/CF. The primary outcomes were ex vivo human platelet aggregation and circulating plasminogen activator inhibitor-1 (PAI-1) and P-selectin (sP-selectin) concentrations. EF consumption had no significant effect on platelet sensitivity or haemostatic markers compared to CF. Platelet sensitivity to platelet-activating factor (PAF) decreased after CF consumption during the second period (p < 0.01). Plasma PAI-1 and sP-selectin concentrations increased after CF consumption during both periods (p < 0.01 for both). Based on current findings, consumption of enriched farmed gilthead sea bream had no greater effect on coagulation markers in adults compared to the conventionally fed fish.

Growth performance, antioxidant capacity, tissue fatty acid composition and lipid metabolism of juvenile green mud crab Scylla paramamosain in response to different dietary n-3 PUFA lipid sources

An six-week feeding trial was conducted to evaluate the effects of dietary n-3 polyunsaturated fatty acid (n-3 PUFA) lipid sources on growth performance, antioxidant capacity, tissue fatty acid profiles, and expression levels of genes involved in lipid metabolism of juvenile green mud crab (Scylla paramamosain) (initial weight 45.3 ± 0.07 g). Three isonitrogenous and isoenergetic experimental diets were formulated to contain fish oil (FO), krill oil (KO) and linseed oil (LO), respectively. The results indicated that crabs fed the KO diet had significantly higher percent weight gain (PWG), specific growth rate (SGR) and feed efficiency (FE) than those fed the LO diet, while no statistic differences were observed between KO and FO diets. Dietary FO could significantly increase the concentrations of malondialdehyde (MDA) and lipid hydroperoxide (LPO) in hemolymph and hepatopancreas compared to dietary KO and LO, similar results were found in the levels of hepatopancreas 8-hydroxy-2-deoxyguanosine (8-OHDG). Crabs fed the KO diet could significantly increase the activities of total superoxide dismutase (T-SOD) and catalase (CAT) in comparison with FO and LO diets. Crabs fed with FO and KO had significantly higher contents of 20:5n-3 (EPA) and 22:6n-3 (DHA) in hepatopancreas and muscle than those fed with LO. While dietary LO could significantly promote the accumulation of C18:3n-3 (ALA) in hepatopancreas and muscle. The anabolic pathway relevant genes: fas and 6 pg d were up-regulated in KO diet. The catabolic pathway relevant genes, hsl, was up-regulated in FO and KO diets, cpt1, was up-regulated in KO diet. Moreover, crabs fed diet supplemented with KO could significantly increase the expression levels of srb2, srebp1 and hnf4α. These findings will provide the reference for the development of the diet for the growth stage of S. paramamosain, and could contribute to deepen the understanding of the physiological metabolism of dietary fatty acids for S. paramamosain.

Dietary Eicosapentaenoic Acid and Docosahexaenoic Acid Ethyl Esters Influence the Gut Microbiota and Bacterial Metabolites in Rats.

Dietary fish oil containing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) has been reported to affect the diversity and composition of gut microbiota and bacterial metabolites. However, few reports have focused on the effects of EPA and DHA on gut microbiota diversity and bacterial metabolites. This study evaluated the effects of dietary EPA-ethyl ester (EE) and DHA-EE on steroid metabolism, gut microbiota, and bacterial metabolites in Wistar rats. Male rats were fed the experimental diets containing 5% (w/w) soybean oil-EE (SOY diet), EPA-EE (EPA diet), and DHA-EE (DHA diet) for four weeks. The lipid contents in the serum and liver, mRNA expression levels in the liver, and the diversity, composition, and metabolites of the gut microbiota were evaluated. The EPA and DHA diets decreased serum and liver cholesterol contents compared to the SOY diet. In addition, there were no significant changes in gene expression levels related to steroid metabolism in the liver between the EPA and DHA groups. Rats fed the DHA diet had lower microbiota diversity indices, such as Simpson and Shannon indices, than rats fed the SOY and EPA diets. In addition, rats fed EPA and DHA had significant differences in the relative abundance of microbiota at the genus level, such as Phascolarctobacterium, Turicibacter, and [Eubacterium]. Therefore, it was concluded that EPA and DHA have different effects on the diversity and composition of gut microbiota under the experimental conditions employed herein.

Putative imbalanced amino acid metabolism in rainbow trout long term fed a plant-based diet as revealed by 1H-NMR metabolomics.

The long-term effect of a plant (P)-based diet was assessed by proton nuclear magnetic resonance (1H-NMR) metabolomics in rainbow trout fed a marine fish meal (FM)-fish oil (FO) diet (M), a P-based diet and a control commercial-like diet (C) starting with the first feeding. Growth performances were not heavily altered by long-term feeding on the P-based diet. An 1H-NMR metabolomic analysis of the feed revealed significantly different soluble chemical compound profiles between the diets. A set of soluble chemical compounds was found to be specific either to the P-based diet or to the M diet. Pterin, a biomarker of plant feedstuffs, was identified both in the P-based diet and in the plasma of fish fed the P-based diet. 1H-NMR metabolomic analysis on fish plasma and liver and muscle tissues at 6 and 48 h post feeding revealed significantly different profiles between the P-based diet and the M diet, while the C diet showed intermediate results. A higher amino acid content was found in the plasma of fish fed the P-based diet compared with the M diet after 48 h, suggesting either a delayed delivery of the amino acids or a lower amino acid utilisation in the P-based diet. This was associated with an accumulation of essential amino acids and the depletion of glutamine in the muscle, together with an accumulation of choline in the liver. Combined with an anticipated absorption of methionine and lysine supplemented in free form, the present results suggest an imbalanced essential amino acid supply for protein metabolism in the muscle and for specific functions of the liver.

Effect of Dietary Fish Oil on Semen Quality and Reproductive Performance of Iranian Zandi Rams.

The current study was conducted to evaluate the effect of dietary fish oil on the semen quality and fertility potential of Zandi rams. For this purpose, a total of 15 Iranian Zandi rams were randomly assigned into three equal groups. The first group was a negative control and were fed without oil supplement. The second group was a positive control, and their diet contained palm oil, and the last group had a diet containing fish oil. All the diets were isocaloric and isonitrogenous. The rams were fed for 70 days, and the semen smaples were collected every 10 days. In experiment I, the evaluated parameters included semen volume, sperm concentration, motility, membrane integrity, and viability. In experiment II, 210 Iranian Zandi rams received CIDR for 12 days and 400 IU of equine chorionic gonadotropin at the time of CIDR removal. Then, they were assigned into three equal groups and artificially inseminated with semen samples. According to the obtained results, the supplementation of ram diet with fish oil as a source of omega-3 fatty acids improved the semen volume, sperm concentration, total motility, progressive motility, viability, membrane integrity, pregnancy rate, parturition rate, and lambing rate of the rams (P≤0.05). In conclusion, fish oil as a dietary supplement for rams could be an effective strategy to improve the semen quality of rams for artificial insemination and other goals.

Intermittent dietary supplementation with fish oil prevents high fat diet-induced enhanced sensitivity to dopaminergic drugs.

Eating a high fat diet can lead to obesity, type 2 diabetes, and dopamine system dysfunction. For example, rats eating high fat chow are more sensitive than rats eating standard chow to the behavioral effects (e.g., locomotion and yawning) of dopaminergic drugs (e.g., quinpirole and cocaine). Daily dietary supplementation with 20% (w/w) fish oil prevents high fat diet-induced enhanced sensitivity to quinpirole-induced yawning and cocaine-induced locomotion; however, doctors recommend that patients take fish oil just two to three times a week. To test the hypothesis that intermittent (i.e., 2 days per week) dietary supplementation with fish oil prevents high fat diet-induced enhanced sensitivity to quinpirole and cocaine, rats eating standard chow (17% kcal from fat), high fat chow (60% kcal from fat), and rats eating standard or high fat chow with 20% (w/w) intermittent (e.g., 2 days per week) dietary fish oil supplementation were tested once weekly with quinpirole [0.0032-0.32 mg/kg, intraperitoneally (i.p.)] or cocaine (1.0-17.8 mg/kg, i.p.) using a cumulative dosing procedure. Consistent with previous reports, eating high fat chow enhanced sensitivity of rats to the behavioral effects of quinpirole and cocaine. Intermittent dietary supplementation of fish oil prevented high fat chow-induced enhanced sensitivity to dopaminergic drugs in male and female rats. Future experiments will focus on understanding the mechanism(s) by which fish oil produces these beneficial effects.

High broodstock fads2 expression combined with nutritional programing through broodstock diet improves the use of low fishmeal and low fish oil diets in gilthead seabream (Sparus aurata) progeny

One of the factors that limits the replacement of fish meal (FM) and fish oil (FO) by plant ingredients in diets for marine fish, is their lack of long chain-polyunsaturated fatty acids (LC-PUFA). LC-PUFA are essential fatty acids for these fish species, which lack sufficient fatty acyl desaturase 2 (Fads2) activity to synthesize them. Nutritional programing or the use of broodstock with a higher Fads2 activity could improve marine fish ability to synthesize LC-PUFA and their ability to use low FM and FO diets. The aim of this study was to determine the effect of gilthead seabream broodstock with inherently high or inherently low fads2 gene expression and nutritional programing with broodstock diets rich in FO or rapeseed oil (RO) on the progeny growth performance, liver morphology, biochemical composition and expression of selected genes. Sea bream juveniles (2.31± 0.01 g initial body weight, mean ± SD) obtained from broodstock with either high (H) or low (L) fads2 expression and fed a broodstock diet based on FO or RO were randomly distributed into 12 × 250 L tanks and nutritionally challenged for 45 days with a diet containing only 7.5% FM and no FO. The highest growth was found in juveniles from broodstock with a high fads2 expression and fed the RO diet, whereas the lowest growth was obtained in those from broodstock with a low fads2 expression and fed the RO diet. Juveniles from broodstock with high fads2 expression showed significantly higher fads2 expression in liver and increased PUFA contents in liver and muscle. Replacement of FO by RO in broodstock diets led to a significantly increased hepatic 18:3n-6/18:2n-6 ratio and reduction in the viscerosomatic index of the progeny juveniles, the hepatocyte size and the ghr-1/ghr-2 expression in muscle. Overall, the results showed significant trans-generational effects of both the broodstock fads2 expression and the type of lipid in the broodstock diet on the metabolism and performance of the juvenile progeny challenged with a diet low in FM and FO.

Application of the fish oil-finishing strategy in a lean marine teleost, tiger puffer (Takifugu rubripes)

A feeding trial was conducted to test the efficacy of the fish oil-finishing strategy in a lean marine teleost, tiger puffer (average initial body weight, 19.50 g). During the 50-day growing-out period, fish was fed diets differing only in supplemented lipid source (6% of dry dietary matter), namely, fish oil (FO), tiger puffer liver oil (TO), linseed oil (LO), soybean oil (SO), rapeseed oil (RO), palm oil (PO), and beef tallow (BT). In the fish oil-fishing period, all the fish were fed diet FO for 30 days. The results showed that the fish oil-finishing strategy restored the muscle DHA content in terrestrially sourced oil (TSO)-based groups to be 82.8–91.6% of that in fish fed fish oil continuously. Compared to DHA, muscle EPA was less easily retained during the growing-out period, but more easily restored during the fish oil-finishing period. Compared to muscle, the LC-PUFA contents in liver of tiger puffer were much lower and more difficult to restore by the fish oil-finishing strategy. LO, RO and BT resulted in significant growth reduction than FO at the end of growing-out period, but this reduction no longer existed at the end of the fish oil-finishing period. Compensatory effects of fish oil re-feeding were also observed for LC-PUFA deposition. Very little difference was observed in fish proximate composition, somatic parameters, and muscle texture among dietary groups during the whole feeding period, but the lipid metabolism-related biochemical parameters in the serum were significantly affected by diet. Liver oil of farmed tiger puffer can be used a suitable and safe lipid source for diets of tiger puffer, and beef tallow seems a better dietary lipid source for tiger puffer than other TSO in terms of easy restoration of LC-PUFA and growth by the fish oil-finishing strategy. In conclusion, the fish oil-finishing strategy had high efficiency in restoring LC-PUFA and growth of tiger puffer previously fed TSO-based diets.

No Effect of Dietary Fish Oil Supplementation on the Recruitment of Brown and Brite Adipocytes in Mice or Humans under Thermoneutral Conditions.

Brown and brite adipocytes within the mammalian adipose organ provide non-shivering thermogenesis and thus, have an exceptional capacity to dissipate chemical energy as heat. Polyunsaturated fatty acids (PUFA) of the n3-series, abundant in fish oil, have been repeatedly demonstrated to enhance the recruitment of thermogenic capacity in these cells, consequently affecting body adiposity and glucose tolerance. These effects are scrutinized in mice housed in a thermoneutral environment and in a human dietary intervention trial. Mice are housed in a thermoneutral environment eliminating the superimposing effect of mild cold-exposure on thermogenic adipocyte recruitment. Dietary fish oil supplementation in two different inbred mouse strains neither affects body mass trajectory nor enhances the recruitment of brown and brite adipocytes, both in the presence and absence of a β3-adrenoreceptor agonist imitating the effect of cold-exposure on adipocytes. In line with these findings, dietary fish oil supplementation of persons with overweight or obesity fails to recruit thermogenic adipocytes in subcutaneous adipose tissue. Thus, the authors' data question the hypothesized potential of n3-PUFA as modulators of adipocyte-based thermogenesis and energy balance regulation.

Replacing fish oil and astaxanthin by microalgal sources produced different metabolic responses in juvenile rainbow trout fed 2 types of practical diets.

Dietary fish oil supplementation provides n-3 long-chained polyunsaturated fatty acids for supporting fish growth and metabolism and enriching fillet with eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; c22:6n-3). Two experiments were performed as a 3 × 2 factorial arrangement of dietary treatments for 16 wk to determine effects and mechanisms of replacing 0%, 50%, and 100% fish oil with DHA-rich microalgae in combination with synthetic vs. microalgal source of astaxanthin in plant protein meal (PM)- or fishmeal (FM)- based diets for juvenile rainbow trout (Oncorhynchus mykiss). Fish (22 ± 0.26 g) were stocked at 17/tank and 3 tanks/diet. The 100% fish oil replacement impaired (P < 0.0001) growth performance, dietary protein and energy utilization, body indices, and tissue accumulation of DHA and EPA in both diet series. The impairments were associated (P < 0.05) with upregulation of hepatic gene expression related to growth (ghr1and igf1) and biosynthesis of DHA and EPA (fads6 and evol5) that was more dramatic in the FM than PM diet-fed fish, and more pronounced on tissue EPA than DHA concentrations. The source of astaxanthin exerted interaction effects with the fish oil replacement on several measures including muscle total cholesterol concentrations. In conclusion, replacing fish oil by the DHA-rich microalgae produced more negative metabolic responses than the substitution of synthetic astaxanthin by the microalgal source in juvenile rainbow trout fed 2 types of practical diets.