Long-chain omega-3 fatty acids regulate bovine whole-body protein metabolism by promoting muscle insulin signalling to the Akt-mTOR-S6K1 pathway and insulin sensitivity.

* Gingras AA,
* White PJ,
* Chouinard PY,
* Julien P,
* Davis TA,
* Dombrowski L,
* Couture Y,
* Dubreuil P,
* Myre A,
* Bergeron K,
* Marette A,
* Thivierge MC.

Department of animal science, Faculty of Food Sciences and Agriculture, Laval University, Quebec, QC G1K 7P4 Canada. carole.thivierge@san.ulaval.ca.

The ability of the skeletal musculature to use amino acids to build or renew constitutive proteins is gradually lost with age and this is partly due to a decline in skeletal muscle insulin sensitivity. Since long-chain omega-3 polyunsaturated fatty acids (LCn-3PUFA) from fish oil are known to improve insulin-mediated glucose metabolism in insulin-resistant states, their potential role in regulating insulin-mediated protein metabolism was investigated in this study. Experimental data are based on a switchback design composed of three 5 week experimental periods using six growing steers to compare the effect of a continuous abomasal infusion of LCn-3PUFA-rich menhaden oil with an iso-energetic control oil mixture. Clamp and insulin signalling observations were combined with additional data from a second cohort of six steers. We found that enteral LCn-3PUFA potentiate insulin action by increasing the insulin-stimulated whole-body disposal of amino acids from 152 to 308 mumol kg(-1) h(-1) (P = 0.006). The study further showed that in the fed steady-state, chronic adaptation to LCn-3PUFA induces greater activation (P < 0.05) of the Akt-mTOR-S6K1 signalling pathway. Simultaneously, whole-body total flux of phenylalanine was reduced from 87 to 67 mumol kg(-1) h(-1) (P = 0.04) and oxidative metabolism was decreased (P = 0.05). We conclude that chronic feeding of menhaden oil provides a novel nutritional mean to enhance insulin-sensitive aspects of protein metabolism.

PMID: 17158167 [PubMed - as supplied by publisher]