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

ABSTRACT: The increasing use of terrestrial plant lipids to replace of fish oil in commercial aquafeeds requires understanding synthesis and storage of long chain-polyunsaturated fatty acids (LC-PUFA) in farmed fish. Manipulation of dietary fatty acids may maximize tissue storage of LC-PUFA, through increased production and selective utilization. A data synthesis study was conducted to estimate optimal levels of fatty acids that may maximize the production and storage of LC-PUFA in the edible portion of salmonids. Data were compiled from four studies with Atlantic salmon, rainbow trout, and steelhead trout (total n = 180) which were fed diets containing different terrestrial-based oils to replace fish oil. LC-PUFA (%) were linearly correlated between diet and muscle tissue (p < 0.001; r2 > 44%), indicating proportional storage after consumption. The slope, or retention rate, was highest for docosahexaenoic acid (DHA) at 1.23, indicating that an additional 23% of DHA was stored in the muscle. Dietary saturated fatty acids were positively related to DHA stored in the muscle (p < 0.001; r2 = 22%), which may involve membrane structural requirements, as well as selective catabolism. DHA was found to be optimally stored with a dietary n-3: n-6 ratio of 1.03: 1. These new results provide a baseline of optimal dietary ratios that can be tested experimentally to determine the efficacy of balancing dietary fatty acids for maximum LC-PUFA storage.

SUBMITTER: Colombo SM

PROVIDER: S-EPMC6179257 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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

Colombo Stefanie M SM Parrish Christopher C CC Wijekoon Manju P A MPA

PloS one 20181010 10

The increasing use of terrestrial plant lipids to replace of fish oil in commercial aquafeeds requires understanding synthesis and storage of long chain-polyunsaturated fatty acids (LC-PUFA) in farmed fish. Manipulation of dietary fatty acids may maximize tissue storage of LC-PUFA, through increased production and selective utilization. A data synthesis study was conducted to estimate optimal levels of fatty acids that may maximize the production and storage of LC-PUFA in the edible portion of s ...[more]

PMID: 30304012

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Project description:BackgroundΔ6-Desaturase (Fads2) is widely regarded as rate-limiting in the conversion of dietary α-linolenic acid (18:3n-3; ALA) to the long-chain omega-3 polyunsaturated fatty acid docosahexaenoic acid (22:6n-3; DHA). However, increasing dietary ALA or the direct Fads2 product, stearidonic acid (18:4n-3; SDA), increases tissue levels of eicosapentaenoic acid (20:5n-3; EPA) and docosapentaenoic acid (22:5n-3; DPA), but not DHA. These observations suggest that one or more control points must exist beyond ALA metabolism by Fads2. One possible control point is a second reaction involving Fads2 itself, since this enzyme catalyses desaturation of 24:5n-3 to 24:6n-3, as well as ALA to SDA. However, metabolism of EPA and DPA both require elongation reactions. This study examined the activities of two elongase enzymes as well as the second reaction of Fads2 in order to concentrate on the metabolism of EPA to DHA.Methodology/principal findingsThe substrate selectivities, competitive substrate interactions and dose response curves of the rat elongases, Elovl2 and Elovl5 were determined after expression of the enzymes in yeast. The competitive substrate interactions for rat Fads2 were also examined. Rat Elovl2 was active with C(20) and C(22) polyunsaturated fatty acids and this single enzyme catalysed the sequential elongation reactions of EPA→DPA→24:5n-3. The second reaction DPA→24:5n-3 appeared to be saturated at substrate concentrations not saturating for the first reaction EPA→DPA. ALA dose-dependently inhibited Fads2 conversion of 24:5n-3 to 24:6n-3.ConclusionsThe competition between ALA and 24:5n-3 for Fads2 may explain the decrease in DHA levels observed after certain intakes of dietary ALA have been exceeded. In addition, the apparent saturation of the second Elovl2 reaction, DPA→24:5n-3, provides further explanations for the accumulation of DPA when ALA, SDA or EPA is provided in the diet. This study suggests that Elovl2 will be critical in understanding if DHA synthesis can be increased by dietary means.

Project description:Docosahexaenoic acid (DHA, 22:6n-3) and arachidonic acid (ARA, 20:4n-6) are the major long chain polyunsaturated fatty acids (LCPUFA) of the central nervous system. We examined the alterations in transcriptional profiles in neonate baboon cerebral cortex brain tissue using high-density Affymetrix oligonucleotide arrays ("U133 plus 2.0"). Twelve neonates were divided into 3 groups: Control (C, no DHA-ARA); 1× LCPUFA (L, 0.33%DHA-0.67%ARA); 3× LCPUFA (L3, 1.00%DHA-0.67%ARA). Significance analysis (P < 0.05) of a total of >54,000 probe sets (ps) identified changes in expression levels of 1108 ps, representing 2.05% of the total ps on the oligoarray, with most ps showing <2-fold change. Comparing L and C, 534 ps were upregulated with supplementation, and 574 ps were downregulated. For the L3/C comparisons, 666 ps were upregulated and 442 ps were downregulated. Characterization of differentially regulated genes by gene ontology assign them to diverse biological functions, notably lipid metabolism, ion channel and transport, G-protein and signal transduction, development, visual perception, membrane function, apoptosis, cytoskeleton, peptidases, cell cycle, stress response, kinases and phosphatases, transcription regulation, receptors, and ubiquitin, with about 400 transcripts having no defined function. Of differentially expressed genes involved in lipid metabolism, PLA2G6, a phospholipase recently associated with infantile neuroaxonal dystrophy, was downregulated in both LCPUFA groups. ELOVL5, a PUFA elongase, was the only enzyme in the LCPUFA biosynthetic pathway that was differentially expressed. Mitochondrial fatty acid carrier, CPT2, was among several genes associated with mitochondrial fatty acid oxidation to be downregulated, while the mitochondrial proton carrier, UCP2, was upregulated. PUFA-regulated receptor, Retinoic acid receptor alpha (RARA) was repressed in both groups, while HNF4A, a PUFA regulated factor, was downregulated in L3/C. Genes involved in neural development, TIMM8A, NRG1, SEMA3D and NUMB, were upregulated while HES1 and SIM1 showed decreased expression. LUM, EML2, TIMP3 and TTC8 which have roles in visual perception were upregulated and TIA1, a silencer of COX2 gene translation is upregulated in L3/C. Ingenuity network analysis identified a top network associated with nervous system development and function with EGFR as the outstanding interaction partner. In this network EGFR interacts with genes involved in neural or visual perception, TIMP3, NRG1, ADAM17, EDG7 and FGF7. Quantitative real time-PCR analysis on selected genes confirmed the array results. The L and L3 groups have DHA and ARA content within the ranges observed in human and baboon breastmilk, and thus these data indicate that LCPUFA concentrations within the normal range of human breastmilk induce global changes in gene expression across numerous functions including transcripts involved in neural development, visual perception, etc. Keywords: dietary dose response

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

Publications

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

Similar Datasets

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