Characterization and tissue expression of twelve selenoproteins in yellow catfish Pelteobagrus fulvidraco fed diets varying in oxidized fish oil and selenium levels

BACKGROUND

Selenium (Se) functions through selenoproteins and is essential to growth and metabolism of vertebrates. The present study was conducted to identify twelve selenoproteins genes (selenoe, selenof, selenoh, selneoi, selenom, selenok, selneon, selenoo, selenot, selenos, selenou and msrb1) from yellow catfish. Their mRNA expression patterns, as well as their response to dietary oxidized fish oils and Se addition were explored.

METHODS

We use 3'and 5' RACE PCR to clone full-length cDNA sequence of twelve selenoprotein genes from yellow catfish. Their mRNA expression patterns were assessed via quantitative real-time PCR. Yellow catfish were fed diet adequate Se+ fresh fish oil, adequate Se+ oxidized fish oil, high Se+ fresh fish oil and high Se+ oxidized fish oil, respectively, for 10 weeks. Their kidney, heart, brain and testis were used to assess the mRNA expression of twelve selenoprotein.

RESULTS

Twelve selenoprotein genes had similar domains with mammals and the other fish. Their mRNAs were expressed widely in eleven tissues but varied with the tissues. Dietary oxidized fish oils and Se addition influenced their mRNA abundances of twelve selenoproteins in a tissue-dependent manner.

CONCLUSION

Our study demonstrated the characterization and expression of twelve selenoproteins, and elucidated their responses in yellow catfish fed diets varying in oxidized fish oils and Se addition, which increased our knowledge into the biological function and regulatory mechanism of Se and selenoproteins in fish.

Protective effects of chlorogenic acid on growth, intestinal inflammation, hepatic antioxidant capacity, muscle development and skin color in channel catfish Ictalurus punctatus fed an oxidized fish oil diet

Under oxidative stress condition, the protective effects of dietary chlorogenic acid (CGA) supplementation on liver antioxidant capacity, intestinal inflammation and barrier function, muscle development and skin coloration in channel catfish Ictalurus punctatus were explored in the current study. With that purpose, I. punctatus were fed five experimental diets containing 2% fresh fish oil (FFO, 9.2 meqO₂/kg) or 2% oxidized fish oil (OFO, 897.4 meqO₂/kg) without or with CGA supplementation (0.02%, 0.04% and 0.08%) for 8 weeks. Upon comparative analysis, the oxidized fish oil consumption significantly lowered weight gain rate, decreased intestinal villi length and muscular thickness values and the tight junction proteins mRNA abundance, augmented the intestinal proinflammatory factors, attenuated hepatic antioxidant enzymes activities and related genes mRNA expression levels, influenced the myogenic regulatory factors expression profile and impacted the myocyte density, myocyte area values as well as the skin pigments contents compared to the FFO treatment. Collectively, long-term feeding of the oxidized fish oil diet suppressed the growth performance, destroyed intestinal structural integrity, caused intestinal inflammation and hepatic oxidative stress, impacted the skeletal development and skin color of I. punctatus. Whereas CGA supplementation in oxidized fish oil diets partially counteracted the negative effects of the oxidized fish oil on I. punctatus in terms of increasing the growth performance, improving the intestinal mucosal structure, alleviating hepatic oxidative stress and intestinal inflammation, recompiling the myogenic regulatory factors expression and improving skin color. In conclusion, CGA has great potential to be an aquatic feed additive.

Evaluation of intervention effects of dietary coenzyme Q10 supplementation on oxidized fish oil-induced stress response in largemouth bass Micropterus salmoides

The aim of this experiment was to investigate whether dietary coenzyme Q10 could alleviate stress response of Micropterus salmoides caused by oxidized fish oil. Four isonitrogenous and isoenergetic diets were formulated to contain 100% fresh fish oil (FFO), 50% fresh fish oil + 50% oxidized fish oil (BFO), 100% oxidized fish oil (OFO) and 100% oxidized fish oil + 0.1% coenzyme Q10 (QFO) and were fed to Micropterus salmoides (95 ± 0.60 g) for 70 days. Higher weight gain rate was recorded in fish fed diet supplemented with coenzyme Q10 (CoQ10). FFO and BFO significantly increased contents of fat and energy in whole-body, while protein and energy retention significantly decreased in fish fed OFO. Apparent digestibility of energy and fat showed a significant decrease trend with increased the proportion of dietary oxidized fish oil. Fish fed OFO significantly increased activities of superoxide dismutase and catalase, while CoQ10 supplementation significantly reduced activities of alanine aminotransferase and aspartate aminotransferase in plasma. Contents of n-3 polyunsaturated fatty acids and highly unsaturated fatty acids, especially EPA and DHA in liver and muscle significantly decreased in fish fed OFO. Transcriptome analysis indicated that a total of 1238, 1189 and 1773 differentially expressed genes (DEGs, |log₂(fold change) | >= 1 and q-value<=0.001) were found in the three comparison groups (FFO vs. OFO, FFO vs. QFO, OFO vs. QFO), respectively. After KEGG enrichment, the main changed pathways in the two comparison groups (FFO vs. OFO, OFO vs. QFO) related to the immune system. Dietary OFO up-regulated the expression of immune-related genes and inflammatory factors, while dietary CoQ10 supplementation reduced these effects.

Emodin ameliorates metabolic and antioxidant capacity inhibited by dietary oxidized fish oil through PPARs and Nrf2-Keap1 signaling in Wuchang bream (Megalobrama amblycephala)

Dietary lipids and fatty acids are involved in cell metabolism and animal physiological regulation. However, oxidized lipids could induce oxidative stress and disorder normal growth and physiological health in fish. A 12-week rearing experiment with 6% fish oil (6F), 6% oxidized fish oil (6OF) and emodin supplemented diets (6F + E, 6OF + E) was conducted to evaluate the protective mechanism of emodin on oxidized fish oil stress in Megalobrama amblycephala. Results indicate that, under oxidized fish oil stress, emodin rescued the growth performance inhibition, improved special growth ratio (SGR), and reduced feed conversion ratio (FCR) and hepatosomatic index (HSI); rescued intestine histological impairment, ameliorated the structural expansion and membrane damage of mitochondria in intestine cells, and increased the length and intensity of intestinal villus. Moreover, emodin enhanced serum immune and antioxidant enzyme activity, increased metabolic activity through PPARs signaling, increased antioxidant capacity through PPARs and Nrf2-Keap1 signaling based on the transcriptional expression of specific genes. These results indicate emodin could be used as an effective immunostimulant to protect organism form oxidative stress induced by dietary oxidized lipid. This may provide insights for oxidized lipid prevention in aquaculture production.

L-carnitine regulated Nrf2/Keap1 activation in vitro and in vivo and protected oxidized fish oil-induced inflammation response by inhibiting the NF-κB signaling pathway in Rhynchocypris lagowski Dybowski

Nrf2/Keap1 pathway is associated with oxidative stress. l-carnitine is currently under preclinical evaluation as a antioxidant, but the use of l-carnitine in aquaculture has been poorly evaluated and so far no mechanism has been demonstrated. Here, we explored the effects of l-carnitine in vitro and in vivo and discussed the possible molecular mechanisms involved. Firstly, Nrf2-siRNA significantly knocked down the mRNA level of Nrf2 in FHM cells. Thus, the activities of antioxidant enzymes (T-SOD, CAT, GSH-PX) and the level of antioxidant substance (GSH) and the level of MDA showed that Nrf2-siRNA pretreatment weakened the protective effect of l-carnitine. Moreover, the mRNA levels of Keap1, Nrf2, Maf and HO-1 indicated that l-carnitine regulated Nrf2/Keap1 activation. Furthermore, oxidized fish oil remarkably suppressed growth in Rhynchocypris lagowski Dybowski, and the lower antioxidant capacity was also observed in liver. According to the results of immune related indexes (the levels of IL-1β, TNF-α, LZM, AKP) in serum and the mRNA levels of immune related genes (NF-κB, IL-1β, TNF-α, IL-8, IL-10 and TGF-β) in liver, oxidized fish oil also induced inflammatory response in fish. Also, l-carnitine supplementation can relieve this bad condition. In conclusion, l-carnitine regulated Nrf2/Keap1 activation in vitro and in vivo and protected oxidized fish oil-induced inflammation response by inhibiting the NF-κB signaling pathway in Rhynchocypris lagowski Dybowski.

Effects of soybean isoflavone on intestinal antioxidant capacity and cytokines in young piglets fed oxidized fish oil

To investigate the effect of glycitein, a synthetic soybean isoflavone (ISF), on the intestinal antioxidant capacity, morphology, and cytokine content in young piglets fed oxidized fish oil, 72 4-d-old male piglets were assigned to three treatments. The control group was fed a basal diet containing fresh fish oil, and the other two groups received the same diet except for the substitution with the same dosage of oxidized fish oil alone or with ISF (oxidized fish oil plus ISF). After 21 d of feeding, supplementation of oxidized fish oil increased the levels of malondialdehyde (MDA), oxidized glutathione (GSSG), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), interleukin-2 (IL-2), nuclear factor κ B (NF-κB), inducible nitric oxide synthase (iNOS), NO, and Caspase-3 in jejunal mucosa, and decreased the villous height in duodenum and the levels of secretory immunoglobulin A (sIgA) and IL-4 in the jejunal mucosa compared with supplementation with fresh oil. The addition of oxidized fish oil plus ISF partially alleviated this negative effect. The addition of oxidized fish oil plus ISF increased the villous height and levels of sIgA and IL-4 in jejunal mucosa, but decreased the levels of IL-1β and IL-2 in jejunal mucosa (P<0.05) compared with oxidized fish oil. Collectively, these results show that dietary supplementation of ISF could partly alleviate the negative effect of oxidized fish oil by improving the intestinal morphology as well as the antioxidant capacity and immune function in young piglets.

The PBMC transcriptome profile after intake of oxidized versus high-quality fish oil: an explorative study in healthy subjects

BACKGROUND

Marine long-chain polyunsaturated fatty acids are susceptible to oxidation, generating a range of different oxidation products with suggested negative health effects. The aim of the present study was to utilize sensitive high-throughput transcriptome analyses to investigate potential unfavorable effects of oxidized fish oil (PV: 18 meq/kg; AV: 9) compared to high-quality fish oil (PV: 4 meq/kg; AV: 3).

METHODS

In a double-blinded randomized controlled study for seven weeks, 35 healthy subjects were assigned to 8 g of either oxidized fish oil or high quality fish oil. The daily dose of EPA+DHA was 1.6 g. Peripheral blood mononuclear cells were isolated at baseline and after 7 weeks and transcriptome analyses were performed with the illuminaHT-12 v4 Expression BeadChip.

RESULTS

No gene transcripts, biological processes, pathway or network were significantly changed in the oxidized fish oil group compared to the fish oil group. Furthermore, gene sets related to oxidative stress and cardiovascular disease were not differently regulated between the groups. Within group analyses revealed a more prominent effect after intake of high quality fish oil as 11 gene transcripts were significantly (FDR < 0.1) changed from baseline versus three within the oxidized fish oil group.

CONCLUSION

The suggested concern linking lipid oxidation products to short-term unfavorable health effects may therefore not be evident at a molecular level in this explorative study.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT01034423.