Long-chain polyunsaturated fatty acid synthesis in fish: Comparative analysis of Atlantic salmon (Salmo salar L.) and Atlantic cod (Gadus morhua L.) Δ6 fatty acyl desaturase gene promoters

Transcriptional control mechanisms of genes of lipid and fatty acid metabolism in the Atlantic salmon (Salmo salar L.) established cell line, SHK-1

“…However, the present study has revealed that Elovl5, an important enzyme for the conversion of the C 18 PUFA, 18:3n-3, to LC-PUFA, EPA and DHA, appears to be regulated differently in salmon compared to mammals, possibly being a direct target for LXR, rather than being regulated primarily by SREBP-1, albeit in an LXRdependent pathway. This finding requires confirmation by direct promoter analyses involving the identification of functional binding sites of the salmon elovl5 gene, similar to those studies recently performed on fish fad genes [18]. The regulation of endogenous LC-PUFA biosynthesis pathway in salmon is particularly important considering the critical role of n-3 LC-PUFA for human health, the role of oily fish such as salmon for provision of n-3 LC-PUFA in the human diet, and the changes to salmon feed driven by environmental, ecological and sustainability issues.…”

“…However, although the regulation of lipid biosynthesis and metabolism in Atlantic salmon is of great importance for nutrition and quality of farmed fish and also for understanding key life history transitions in wild fish, studies at the molecular level have been hampered by a lack of suitable experimentally tractable systems and manipulatable candidate genes. Previous studies in mammalian species [6] and in salmon [16,18] have indicated the importance of SREBP transcription factors, particularly in relation to the control of lipid and cholesterol biosynthesis. One aim of the present study was to identify and compare salmon SREBPs with characterised SREBPs from other species.…”

“…Furthermore the human Δ6 desaturase gene contains a SREBP-1 response element which mediates LC-PUFA suppression of expression [47] and this element is conserved in the salmon gene [18]. However, it will be necessary to more fully characterise the salmon LXR with regard to its activation by synthetic ligands in order to fully distinguish LXR and SREBP regulation.…”

“…Furthermore, gene promoter studies have implicated SREBPs as important transcriptional regulators of salmon Δ6 Fad [18]. However, there is very little information regarding SREBF genes and their regulatory functions and controls in fish.…”

“…The LC-PUFA synthesis pathway has been extensively studied and salmon were shown to have multiple Fad proteins with the necessary Δ6 and Δ5 activities [12][13][14], and Elovls, including Elovl5 and Elovl2 [15] 4 for biosynthesis of EPA and DHA. Several studies have shown that salmon Fad and Elovl genes are regulated at the transcriptional level after reduced dietary LC-PUFA resulting in increased expression and correspondingly increased LC-PUFA biosynthesis [15][16][17][18].…”