Optimizing long chain-polyunsaturated fatty acid synthesis in salmonids by balancing dietary inputs

n-3 polyunsaturated fatty acids delay intervertebral disc degeneration by inhibiting nuclear receptor coactivator 4-mediated iron overload

n-3 polyunsaturated fatty acids (PUFAs) are closely related to the progression of numerous chronic inflammatory diseases, but the role of n-3 PUFAs in the intervertebral disc degeneration (IVDD) remains unclear. In this study, male C57BL/6 wildtype mice (WT group, n = 30) and fat-1 transgenic mice (TG group, n = 30) were randomly selected to construct the IVDD model. The results demonstrated that the optimized composition of PUFAs in the TG mice had a significant impact on delaying IVDD and cellular senescence of intervertebral disc (IVD). Mechanismly, n-3 PUFAs inhibited IVD senescence by alleviating NCOA4-mediated iron overload. NCOA4 overexpression promoted iron overload and weakened the pro-proliferation and anti-senescence effect of DHA on the IVD cells. Furthermore, this study futher revealed n-3 PUFAs downregulated NCOA4 expression by inactiviting the LGR5/β-catenin signaling pathway. This study provides an important theoretical basis for preventing and treating IVDD and low back pain.

An overview of microalgae biomass as a sustainable aquaculture feed ingredient: food security and circular economy

Sustainable management of natural resources is critical to food security. The shrimp feed and fishery sector is expanding rapidly, necessitating the development of alternative sustainable components. Several factors necessitate the exploration of a new source of environmentally friendly and nutrient-rich fish feed ingredients. Microalgal biomass has the potential to support the growth of fish and shrimp aquaculture for global food security in the bio-economy. Algal biorefineries must valorize the whole crop to develop a viable microalgae-based economy. Microalgae have the potential to replace fish meal and fish oil in aquaculture and ensure sustainability standards. Microalgae biomasses provide essential amino acids, valuable triglycerides such as lipids, vitamins, and pigments, making them suitable as nutritional supplements in livestock feed formulations. Fish and microalgae have similar nutritional profiles, and digestibility is a critical aspect of the aquafeed formulation. A highly digestible feed reduces production costs, feed waste, and the risk of eutrophication. Due to low input costs, low carbon footprint, wastewater treatment benefits, and carbon credits from industrial CO₂ conversion, microalgae-based fish and shrimp feeds have the potential to provide significant economic benefits. However, several challenges must be addressed before microalgal biomass and bioproducts may be used as fish feeds, including heavy metal bioaccumulation, poor algal biomass digestion, and antinutrient effects. Knowledge of biochemical composition is limited and diverse, and information on nutritional value is scattered or contradictory. This review article presents alternative approaches that could be used in aquaculture to make microalgal biomass a viable alternative to fish meal.

Production of rainbow trout (Oncorhynchus mykiss) using black soldier fly (Hermetia illucens) prepupae-based formulations with differentiated fatty acid profiles

The aquaculture sector is expanding rapidly and needs an increasing supply of fishery products. To ensure an ecological transition of this sector, alternative feed ingredients are required for fish nutrition. Potential alternatives include insects, particularly the black soldier fly (BSF, Hermetia illucens L. 1758), which is being increasingly targeted for their nutritional qualities and their sustainable production practices. BSF have a well-balanced amino acid profile; however, their fatty acid profile is not sufficiently balanced for most aquafeed formulations but can be modulated through their feed. In this study, two different batches of BSF prepupae (BSFP) were firstly produced: BSFP with a standard ω3 content (C18:3n-3 ≈ 1.36%) and ω3-enriched BSFP (C18:3n-3 ≈ 9.67%). Then, three isoproteic, -lipidic and -energetic trout feeds were formulated and produced: one control and two feeds containing 75% BSF meal as a substitute for fish meal (standard vs ω3-enriched-BSF). Finally, a trout feeding trial (n = 3 for each feed batch) in a recirculating aquaculture system was carried out for 75 days. BSFP meal inclusion in trout diets did not impact most nutritional and growth parameters of trout compared to the control; however, the coefficient of fatness increased, weight gain decreased and fatty acid profiles of fillets were altered. In conclusion, this study presents a more sustainable model of trout production by including insects from bioconversion of local byproducts in aquafeed.

Dietary Polyunsaturated Fatty Acids (PUFAs): Uses and Potential Health Benefits

PURPOSE OF REVIEW

Polyunsaturated fatty acids (PUFAs) are obtained from various sources, which can be incorporated in the routine diet to maintain the health. They provide protection from several diseases like osteoarthritis, cancer, and autoimmune disorders. Major focus is given to the PUFAs omega-3 (ω-3) and omega-6 (ω-6) fatty acids which are available in both terrestrial and in the marine environment. The main concern of this article is to review the key scientific reports in context with the human health consequences and advantages of the food sources of ω-3 and ω-6 fatty acids.

RECENT FINDINGS

ω-3 and ω-6 fatty acids are consumed by the population globally in the form of foods that are rich in fatty acids. Their nutritional effects have the capability to improve the physical functioning and metabolic rate of the body. These PUFAs contribute in various cellular activities like cell signaling, structural integrity and fluidity of cell membrane, the regulation of blood pressure, glucose level, the nervous system, inflammatory reactions, and hematic clotting. Animal and cell-based models represent that ω-3 and ω-6 PUFAs can regulate the skeletal muscle metabolism. The main concern of this article is to review the key scientific reports in context with the human health consequences and advantages of the food sources of ω-3 and ω-6 fatty acids.

Schizochytrium sp. (T18) Oil as a Fish Oil Replacement in Diets for Juvenile Rainbow Trout (Oncorhynchus mykiss): Effects on Growth Performance, Tissue Fatty Acid Content, and Lipid-Related Transcript Expression

In this study, we evaluated whether oil extracted from the marine microbe, Schizochytrium sp. (strain T18), with high levels of docosahexaenoic acid (DHA), could replace fish oil (FO) in diets for rainbow trout (Oncorhynchus mykiss). Three experimental diets were tested: (1) a control diet with fish oil (FO diet), (2) a microbial oil (MO) diet with a blend of camelina oil (CO) referred to as MO/CO diet, and (3) a MO diet (at a higher inclusion level). Rainbow trout (18.8 ± 2.9 g fish-1 initial weight ± SD) were fed for 8 weeks and evaluated for growth performance, fatty acid content and transcript expression of lipid-related genes in liver and muscle. There were no differences in growth performance measurements among treatments. In liver and muscle, eicosapentaenoic acid (EPA) was highest in trout fed the FO diet compared to the MO/CO and MO diets. Liver DHA was highest in trout fed the MO/CO diet compared to the FO and MO diets. Muscle DHA was highest in trout fed the MO and MO/CO diets compared to the FO diet. In trout fed the MO/CO diet, compared to the MO diet, fadsd6b was higher in both liver and muscle. In trout fed the FO or MO/CO diets, compared to the MO diet, cox1a was higher in both liver and muscle, cpt1b1a was higher in liver and cpt1a1a, cpt1a1b and cpt1a2a were higher in muscle. Schizochytrium sp. (T18) oil was an effective source of DHA for rainbow trout.

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.

Influence of Dietary Long-Chain Polyunsaturated Fatty Acids and ω6 to ω3 Ratios on Head Kidney Lipid Composition and Expression of Fatty Acid and Eicosanoid Metabolism Genes in Atlantic Salmon (Salmo salar)

The interaction of dietary eicosapentaenoic acid and docosahexaenoic acid (EPA+DHA) levels with omega-6 to omega-3 ratios (ω6:ω3), and their impact on head kidney lipid metabolism in farmed fish, are not fully elucidated. We investigated the influence of five plant-based diets (12-week exposure) with varying EPA+DHA levels (0.3, 1.0, or 1.4%) and ω6:ω3 (high ω6, high ω3, or balanced) on tissue lipid composition, and transcript expression of genes involved in fatty acid and eicosanoid metabolism in Atlantic salmon head kidney. Tissue fatty acid composition was reflective of the diet with respect to C₁₈ PUFA and MUFA levels (% of total FA), and ω6:ω3 (0.5–1.5). Fish fed 0.3% EPA+DHA with high ω6 (0.3% EPA+DHA↑ω6) had the highest increase in proportions (1.7–2.3-fold) and in concentrations (1.4-1.8-fold) of arachidonic acid (ARA). EPA showed the greatest decrease in proportion and in concentration (by ~½) in the 0.3% EPA+DHA↑ω6 fed fish compared to the other treatments. However, no differences were observed in EPA proportions among salmon fed the high ω3 (0.3 and 1.0% EPA+DHA) and balanced (1.4% EPA+DHA) diets, and DHA proportions were similar among all treatments. Further, the transcript expression of elovl5a was lowest in the 0.3% EPA+DHA↑ω6 fed fish, and correlated positively with 20:3ω3, 20:4ω3 and EPA:ARA in the head kidney. This indicates that high dietary 18:3ω3 promoted the synthesis of ω3 LC-PUFA. Dietary EPA+DHA levels had a positive impact on elovl5a, fadsd5 and srebp1 expression, and these transcripts positively correlated with tissue ΣMUFA. This supported the hypothesis that LC-PUFA synthesis is positively influenced by tissue MUFA levels in Atlantic salmon. The expression of pparaa was higher in the 0.3% EPA+DHA↑ω6 compared to the 0.3% EPA+DHA↑ω3 fed fish. Finally, significant correlations between head kidney fatty acid composition and the expression of eicosanoid synthesis-related transcripts (i.e., 5loxa, 5loxb, cox1, cox2, ptges2, ptges3, and pgds) illustrated the constitutive relationships among fatty acids and eicosanoid metabolism in salmon.

Evaluation of triacylglycerol (TAG) profiles and their contents in salmon muscle tissue using ESI-MS/MS spectrometry with multiple neutral loss scans

Identification and quantification of triacylglycerols (TAGs) in salmon muscle tissue were conducted using electrospray ionization (ESI)-MS/MS in a triple quadrupole mass spectrometer. The confirmation of three fatty acid moieties of individual TAGs was determined using the multiple neutral loss (NL) scanning mode. A total of 98 TAGs were identified, and the predominant TAG species were 16:0-18:0-20:5 (10.4%), 18:1-18:2-22:6 (9.0%), and 18:0-18:1-22:6 (16.4%) in salmon muscle tissue. NL scanning was an effective means to confirm the three fatty acid moieties of the TAGs, leading to the rapid and accurate identification of individual TAGs. To the best of our knowledge, this is the first application of multiple neutral loss scanning to identify TAGs in salmonoid tissue, and many TAG species have been newly identified (i.e., 18:1-18:2-22:6, 16:0-18:2-20:5, 18:1-18:2-20:5, etc.). This study showed that the shotgun lipidomic approach along with NL scans is a useful means for studying TAG metabolism in fish.