Premium
LC‐PUFA Biosynthesis in Rainbow Trout is Substrate Limited: Use of the Whole Body Fatty Acid Balance Method and Different 18:3n‐3/18:2n‐6 Ratios
Author(s) -
Thanuthong T.,
Francis D. S.,
Senadheera S. P. S. D.,
Jones P. L.,
Turchini G. M.
Publication year - 2011
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/s11745-011-3607-4
Subject(s) - rainbow trout , lipidology , substrate (aquarium) , clinical chemistry , biosynthesis , polyunsaturated fatty acid , chemistry , fatty acid , biochemistry , rainbow , balance (ability) , fish <actinopterygii> , food science , chromatography , biology , fishery , ecology , enzyme , physics , quantum mechanics , neuroscience
Five experimental diets with constant total C 18 PUFA and varying 18:3n‐3/18:2n‐6 ratios were fed to rainbow trout over an entire production cycle. The whole‐body fatty acid balance method demonstrated a clear trend of progressively reduced fatty acid bioconversion activity along the n‐3 and n‐6 pathways, up to the production of 20:5n‐3 and 20:4n‐6, respectively. This suggests that the pathway exhibits a “funnel like” progression of activity rather than the existence of a single rate limiting step. The production of 22:5n‐3 and 22:6n‐3 was more active than that of 20:5n‐3. However, despite this trend in reduced apparent in vivo net enzyme activity, the efficiency of the various bioconversion steps (measured as % of bioconverted substrate) confirmed an opposing trend. A 3.2‐fold higher Δ‐6 desaturase affinity towards 18:3n‐3 over 18:2n‐6 and an 8‐fold greater Δ‐5 desaturase affinity towards 20:4n‐3 over 20:3n‐6 were recorded. The main results of the study were that (1) rainbow trout are quite efficient at bioconverting 18:3n‐3 to 22:6n‐3, and (2) the LC‐PUFA biosynthetic pathway is substrate limited. Fillet n‐3 LC‐PUFA concentrations increased with the increasing dietary supply of 18:3n‐3. Despite an almost identical dietary supply of n‐3 LC‐PUFA, originating from the fish meal fraction of the diets, the fillets of trout fed the diet richest in 18:3n‐3 were 2‐fold higher in n‐3 LC‐PUFA than fish fed low 18:3n‐3 diets. Nevertheless, fillets of trout fed a fish oil control diet contained more than double the amount of n‐3 LC‐PUFA compared to fish fed the diets richest in 18:3n‐3.