Expression of enzymes and transcription factors involved in n-3 long chain PUFA biosynthesis in limousin bull tissues.
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.
INRA, UR 1213 Herbivore, Site de Theix, 63122, Saint-Genès-Champanelle, France.
Maya
M
Cherfaoui
Denys
D
Durand
Muriel
M
Bonnet
Isabelle
I
Cassar-Malek
Dominique
D
Bauchart
Agnès
A
Thomas
Dominique
D
Gruffat
D044944:Acyl-CoA Dehydrogenases / Q000235:genetics / Q000378:metabolism; D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism; D000273:Adipose Tissue / Q000201:enzymology*; D000818:Animals; D002417:Cattle; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism; D015525:Fatty Acids, Omega-3 / Q000096:biosynthesis*; D015870:Gene Expression; D050356:Lipid Metabolism / Q000235:genetics*; D008099:Liver / Q000201:enzymology*; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology*; D012333:RNA, Messenger / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D015525:Fatty Acids, Omega-3; D012333:RNA, Messenger; D014157:Transcription Factors; D044943:Fatty Acid Desaturases; D044944:Acyl-CoA Dehydrogenases; D000217:Acyltransferases