Influence of oilseed supplement ranging in n-6-3 ratio on fatty acid composition and Delta 5-, Delta 6-desaturase protein expression in steer muscles.

摘要

This study investigated effects of roasted or extruded oilseed supplementation ranging in n-6-3 ratios from 0.3 to 5.0 on the fatty acid composition and expression of delta-5 desaturase ( Delta 5d) and Delta 6-desaturase ( Delta 6d) protein in commercial steer cheek (m. masseter) and diaphragm (pars costalis diaphragmatis) muscles. In general, the n-6-3 ratio of the diet had a subsequent effect on the muscle n-6-3 ratio (P<0.05), with muscle 18:2n-6 and 18:3n-3 content relating to proportion of dietary soya bean and linseed (P<0.01). Compared with canola, pure linseed and soya bean diets reduced 14:1c-9 and 16:1c-9 (P<0.05) but increased 18:1t-11 and c-9,t-11 conjugated linoleic acid (CLA) content (P<0.01). Oilseed processing had a minor influence but extruded oilseeds increase 18:1t-11 and c-9,t-11 CLA compared with roasted (P<0.05). Polar lipid 18:3n-3 and n-3 long-chain polyunsaturated fatty acid (LC, >=20 carbons PUFA) derivative content increased in relation to dietary linseed supplementation in the diaphragm (P<0.01), whereas only 18:3n-3 was increased in the cheek (P<0.01). Protein expression did not differ between diets; however, in each muscle the Delta 5d protein expression had a stronger association with the desaturase products rather than the precursors. The relationship between Delta 5d protein expression and the muscle LC n-6-3 ratio was negative in both muscles (P<0.05). The relationship between Delta 6d protein expression and the LC n-6-3 ratio was positive in the cheek (P<0.001) and negative in the diaphragm (P<0.05). In conclusion, diet n-6-3 ratio affected muscle 18:2n-6 and 18:3n-3 deposition, whereas the Delta 5d and Delta 6d protein expression had some influence on the polar lipid LC-PUFA profile. Results reaffirm that processed oilseeds can be used to increase the proportion of fatty acids potentially beneficial for human health, by influencing the formation of LC-PUFA and reducing the n-6-3 ratio.