Beschreibung:
<jats:title>Abstract</jats:title><jats:p>The current low consumption of n‐3 long chain polyunsaturated fatty acids (n‐3 LCPUFA) led scientists to wonder about the possible enrichment of human food, including meats such as beef, with n‐3 LCPUFA. However, their biosynthesis from dietary n‐3 PUFA seems limited in mammalian tissues implying that a better understanding of the molecular mechanisms responsible for this down regulation is needed. This study aimed at identifying and comparing the limiting steps of n‐3 LCPUFA synthesis in liver, intermuscular adipose tissue (IM‐AT) and semitendinosus muscle (ST) from six Limousin bulls. Tissue FA composition was analysed by GLC and mRNA abundance of enzymes and transcription factors involved in n‐3 LCPUFA synthesis was assessed by RT‐qPCR. In liver, mRNA encoding proteins involved in n‐3 LCPUFA synthesis were present in agreement with the significant high content of n‐3 LCPUFA (8.4 mol% of total FA, 257 mg/100 g of fresh tissue) in this organ. In IM‐AT, these mRNA were all present, but at a tenfold lower intensity than in liver in agreement with the low contents of n‐3 LCPUFA in this tissue. In ST muscle, these mRNA were all present except elongase 5 mRNA which was only present as trace, the corresponding protein being undetectable, probably inducing a break of n‐3 LCPUFA synthesis from 18:4n‐3. In conclusion, Limousin bull ST muscle seemed unable to synthesize n‐3 LCPUFA. However, the presence of 20:5n‐3 (EPA) and 22:5n‐3 (DPAn‐3) in muscle raised the question of the origin of these n‐3 LCPUFA.</jats:p>