Impact of Reduced Dietary Levels of Eicosapentaenoic Acid and Docosahexaenoic Acid on the Composition of Skin Membrane Lipids in Atlantic Salmon ( Salmo salar L.)

Investigation of the functions of n-3 very-long-chain PUFAs in skin using in vivo Atlantic salmon and in vitro human and fish skin models

The purpose of this study was to investigate the effect of dietary n-3 very-long-chain PUFA (n-3 VLC-PUFA) on the maturation and development of skin tissue in juvenile Atlantic salmon (Salmo salar) in vivo, as well as their effects on skin keratocyte and human skin fibroblast cell migration in vitro. Atlantic salmon were fed different dietary levels of n-3 VLC-PUFA from an initial weight of 6 g to a final weight of 11 g. Changes in skin morphology were analysed at two time points during the experiment, and the effects on skin tissue fatty acid composition were determined. Additionally, in vitro experiments using human dermal fibroblasts and primary Atlantic salmon keratocytes were conducted to investigate the effect of VLC-PUFA on the migration capacity of the cells. The results demonstrated that increased dietary levels of n-3 VLC-PUFA led to an increased epidermis thickness and more rapid scale maturation in Atlantic salmon skin in vivo, leading to a more mature skin morphology, and possibly more robust skin, at an earlier life stage. Additionally, human skin fibroblasts and salmon skin keratocytes supplemented with n-3 VLC-PUFA in vitro showed more rapid migration, indicating potentially beneficial effects of VLC-PUFA in wound healing. In conclusion, VLC-PUFA may have beneficial effects on skin tissue development, function and integrity.

Dietary Cholesterol Differentially Regulates the Muscle Lipidomics of Farmed Turbot and Tiger Puffer

Exogenous cholesterol has been supplemented into aqua-feeds due to the reduced proportions of fishmeal and fish oil. This study aimed to investigate the effects of dietary cholesterol supplementation on the muscle lipidomics of two marine fish species, turbot and tiger puffer. A 70-day feeding trial was conducted, where two low-fishmeal diets supplemented with 0 or 1% cholesterol were used. The lipidomic analysis with targeted tandem mass spectrometry showed that, in turbot, a total of 49 individual lipids exhibited significant differences in their abundance in response to dietary cholesterol, whereas the number was 30 for tiger puffer. Dietary cholesterol up-regulated the abundance of cholesterol and cholesterol ester in both species. In turbot, the dietary cholesterol also increased the abundance of triacylglycerol and acylcarnitine, whereas in tiger puffer, it primarily regulated the abundance of phospholipids and BMP. This was the first time the responses of marine fish muscle lipidomics to dietary cholesterol supplementation have been investigated.

Microalgae Oil as an Effective Alternative Source of EPA and DHA for Gilthead Seabream (Sparus aurata) Aquaculture

Simple Summary

Aquaculture must rely on sustainable aquafeeds to attain the future demand for farmed and high-quality seafood. Algae-derived ingredients, particularly oils from microalgae, have recently emerged as an alternative to fish oil and vegetable oils extracted from terrestrial plants. Such microalgae oils are sustainable alternatives, rich in essential fatty acids and free of dioxins and polychlorinated biphenyls (PCBs). This study assesses the incorporation of microalgae oils in the diet of gilthead seabream, which is a carnivorous species with typically high demand for fish-based ingredients, particularly fishmeal and fish oil. In particular, its effect on feed quality, seabream growth performance, fillet quality, and safety were compared when fish were fed a diet rich in fish oil versus diets formulated with microalgal oils (3.5 or 0.7% incorporation rate). Importantly, fish performance was maintained when fish oil was replaced by microalgae oil, and fish fillet showed noticeably lower levels of contamination and similar sensory quality. Collectively, the findings of this study showed that aquafeeds formulated with microalgae oils fulfil important nutritional requirements of gilthead seabream and result in a high quality product. Ultimately, these findings offer a more resilient means for sustaining the future growth of gilthead seabream aquaculture.

Abstract

Microalgal oils (AOs) emerged recently as an alternative to fish oil and to nutritionally poorer vegetable oils for fish species. In this trial, two experimental diets containing fish oil (negative control: 2.1%; positive control: 13.8%) and two diets incorporating AO at 3.5 and 0.7% were fed to grow out gilthead seabream (Sparus aurata) of 64.5 g initial body weight. After 110 days of experimental feeding, performance (final body weight mean = 147 g) and survival (>99%) were similar across treatments. The highest eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) content in positive control (PC) and 3.5 AO feeds (3.11 and 2.18% of diet, respectively) resulted in the highest EPA + DHA deposition in the fillets (18.40 and 12.36 g/100 g fatty acid, respectively), which entirely reflected the dietary fatty acid profile. Feed and fillets from fish fed the AO diets had lower levels of dioxins and polychlorinated biphenyls (PCBs). Moreover, sensory quality of AO fillets scored equally to the PC fish. Collectively, these findings offer a more resilient means for sustaining the future growth of seabream aquaculture, whilst maintaining the nutritional value of the resulting seafood. The data supports the addition of seabream to the list of aquaculture species where microalgal oil can be used as an ingredient to fulfil their challenging nutritional demands.

Increasing dietary n-6 fatty acids while keeping n-3 fatty acids stable decreases EPA in polar lipids of farmed Atlantic salmon (Salmo salar)

There is an increased use of vegetable oils containing n-6 fatty acids (FA) in aquafeeds, and several trials indicate that there might be an increased requirement of EPA and DHA for Atlantic salmon when they are fed higher dietary n-6 FA. With a limited supply of EPA and DHA for production of aquafeeds, it is important to know how to efficiently use these FA to maintain growth and health of the fish. In the present trial, three diets containing equal amounts of n-3 FA (about 7·7 % of total FA) and different n-6:n-3 FA ratios (about 1, 2 and 6), as well as one diet with n-6:n-3 FA ratio at about 1 but twice as much n-3 FA, were fed to Atlantic salmon. Despite constant dietary n-3, increasing dietary n-6 led to significantly reduced n-3 in tissue polar lipids. Interestingly, EPA was significantly reduced while DHA was not. Maintaining a stable n-3 content in the polar lipids when increasing dietary n-6 FA was only obtained by simultaneously increasing the dietary n-3 content and with this maintaining the same n-6:n-3 FA ratio. Polar lipid n-6 FA in tissues thus primarily reflected the dietary n-6:n-3 FA ratio and not the absolute dietary n-6 FA content. Neutral lipids, on the other hand, reflected the dietary absolute levels of both n-3 and n-6 FA. This study indicates that a better use of dietary EPA is achieved by keeping the dietary n-6:n-3 FA ratio low.

Untargeted Screening of EPA/DHA Structured Phospholipids in Krill Oil by Chain-Lock-Driven Hydrophilic Interaction Liquid Chromatography Tandem Mass Spectrometry

Eicosapentaenoic and docosahexaenoic acids structured phospholipids (PL_EPA/DHA) have multiple biochemical and pharmacological effects on human health. In this study, EPA and DHA chains were locked under precursor ion scan (PreIS) mode for untargeted screening PL_EPA/DHA in krill oil using hydrophilic interaction liquid chromatography tandem mass spectrometry (HILIC-MS/MS). The effect of collision energy and declustering potential on the fragmentation of EPA (m/z 301.2) and DHA (m/z 327.2) chains was studied. A total of 33 PL_EPA/DHA were characterized (sn-1/sn-2) and quantified using regression models, including 16 PC_EPA/DHA, 11 PE_EPA/DHA, and 6 PI_EPA/DHA. Afterward, this method was validated in terms of linearity (≥0.9978), sensitivity (LOD ≤ 4.02 μg·L^-1), precision (RSD_intraday ≤ 4.71%), and recovery (≥78.9%). Finally, the performance of HILIC-PreIS-MS/MS was compared with those of conventional methods, and the results indicated its superiority in selective screening PL_EPA/DHA in krill oil.

Effects of dietary arachidonic acid in European sea bass (Dicentrarchus labrax) distal intestine lipid classes and gut health

The use of low fishmeal/fish oil in marine fish diets affects dietary essential fatty acids (EFAs) composition and concentration and, subsequently, may produce a marginal deficiency of those fatty acids with a direct impact on the fish intestinal physiology. Supplementation of essential fatty acids is necessary to cover the requirements of the different EFAs, including the ones belonging to the n-6 series, such as arachidonic acid (ARA). ARA, besides its structural role in the configuration of the lipid classes of the intestine, plays an important role in the functionality of the gut-associated immune tissue (GALT). The present study aimed to test five levels of dietary ARA (ARA0.5 (0.5%), ARA1 (1%), ARA2 (2%), ARA4 (4%), and ARA6 (6%)) for European sea bass (Dicentrarchus labrax) juveniles in order to determine (a) its effect in selected distal intestine (DI) lipid classes composition and (b) how these changes affected gut bacterial translocation rates and selected GALT-related gene expression pre and post challenge. No differences were found between distal intestines of fish fed with the graded ARA levels in total neutral lipids and total polar lipids. However, DI of fish fed with the ARA6 diet presented a higher (P < 0.05) level of phosphatidylethanolamine (PE) and sphingomyelin (SM) than those DI of fish fed with the ARA0.5 diet. In general terms, fatty acid profiles of DI lipid classes mirrored those of the diet dietary. Nevertheless, selective retention of ARA could be observed in glycerophospholipids when dietary levels are low (diet ARA0.5), as reflected in the higher glycerophospholipids-ARA/dietary-ARA ratio for those animals. Increased ARA dietary supplementation was inversely correlated with eicosapentaenoic acid (EPA) content in lipid classes, when data from fish fed with the diets with the same basal composition (diets ARA1 to ARA6). ARA supplementation did not affect intestinal morphometry, goblet cell number, or fish survival, in terms of gut bacterial translocation, along the challenge test. However, after the experimental infection with Vibrio anguillarum, the relative expression of cox-2 and il-1β were upregulated (P < 0.05) in DI of fish fed with the diets ARA0.5 and ARA2 compared with fish fed with the rest of the experimental diets. Although dietary ARA did not affect fish survival, it altered the fatty acid composition of glycerophospholipids and the expression of pro-inflammatory genes after infection when included at the lowest concentration, which could be compromising the physical and the immune functionality of the DI, denoting the importance of ARA supplementation when low FO diets are used for marine fish.

Recessive GM3 synthase deficiency: Natural history, biochemistry, and therapeutic frontier

GM3 synthase, encoded by ST3GAL5, initiates synthesis of all downstream cerebral gangliosides. Here, we present biochemical, functional, and natural history data from 50 individuals homozygous for a pathogenic ST3GAL5 c.862C>T founder allele (median age 8.1, range 0.7-30.5 years). GM3 and its derivatives were undetectable in plasma. Weight and head circumference were normal at birth and mean Apgar scores were 7.7 ± 2.0 (1 min) and 8.9 ± 0.5 (5 min). Somatic growth failure, progressive microcephaly, global developmental delay, visual inattentiveness, and dyskinetic movements developed within a few months of life. Infantile-onset epileptic encephalopathy was characterized by a slow, disorganized, high-voltage background, poor state transitions, absent posterior rhythm, and spike trains from multiple independent cortical foci; >90% of electrographic seizures were clinically silent. Hearing loss affected cochlea and central auditory pathways and 76% of children tested failed the newborn hearing screen. Development stagnated early in life; only 13 (26%) patients sat independently (median age 30 months), three (6%) learned to crawl, and none achieved reciprocal communication. Incessant irritability, often accompanied by insomnia, began during infancy and contributed to high parental stress. Despite catastrophic neurological dysfunction, neuroimaging showed only subtle or no destructive changes into late childhood and hospitalizations were surprisingly rare (0.2 per patient per year). Median survival was 23.5 years. Our observations corroborate findings from transgenic mice which indicate that gangliosides might have a limited role in embryonic neurodevelopment but become vital for postnatal brain growth and function. These results have critical implications for the design and implementation of ganglioside restitution therapies.