Wide-gene expression analysis of lipid-relevant genes in nutritionally challenged gilthead sea bream (Sparus aurata).

Disturbances of lipid metabolism are a major problem in livestock fish and the present study analysed the different tissue expression patterns and regulations of 40 lipid-relevant genes in gilthead sea bream. Nineteen sequences, including fatty acid elongases (4), phospholipases (7), acylglycerol lipases (8) and lipase-maturating enzymes (1), were new for gilthead sea bream (GenBank, JX975700-JX975718JX975700JX975701JX975702JX975703JX975704JX975705JX975706JX975707JX975708JX975709JX975710JX975711JX975712JX975713JX975714JX975715JX975716JX975717JX975718). Up to six different lipase-related enzymes were highly expressed in adipose tissue and liver, which also showed a high expression level of Δ6 and Δ9 desaturases. In the brain, the greatest gene expression level was achieved by the very long chain fatty acid elongation 1, along with relatively high levels of Δ9 desaturases and the phospholipase retinoic acid receptor responder. These two enzymes were also expressed at a high level in white skeletal muscle, which also shared a high expression of lipid oxidative enzymes. An overall down-regulation trend was observed in liver and adipose tissue in response to fasting following the depletion of lipid stores. The white skeletal muscle of fasted fish showed a strong down-regulation of Δ9 desaturases in conjunction with a consistent up-regulation of the "lipolytic machinery" including key enzymes of tissue fatty acid uptake and mitochondrial fatty acid transport and oxidation. In contrast, the gene expression profile of the brain remained almost unaltered in fasted fish, which highlights the different tissue plasticity of lipid-related genes. Taken together, these findings provide new fish genomic resources and contribute to define the most informative set of lipid-relevant genes for a given tissue and physiological condition in gilthead sea bream.