J. Anim Sci.
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J. Anim Sci. 2009. 87:244-252. doi:10.2527/jas.2008-1005
© 2009 American Society of Animal Science
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ANIMAL NUTRITION

Effect of level and duration of dietary n-3 polyunsaturated fatty acid supplementation on the transcriptional regulation of {Delta}9-desaturase in muscle of beef cattle1

S. M. Waters*,2, J. P. Kelly{dagger}, P. O’Boyle*, A. P. Moloney* and D. A. Kenny{dagger}

* Teagasc, Animal Bioscience Centre, Grange, Dunsany, Co. Meath, Ireland; and {dagger} School of Agriculture, Food Science & Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland

2 Corresponding author: Sinead.Waters{at}teagasc.ie

The objective of this study was to examine the effect of level and duration of feeding of an n-3 PUFA-enriched fish oil (FO) supplement in combination with soybean oil (SO) on the transcriptional regulation of {Delta}9-desaturase gene expression in bovine muscle. Beef bulls (n = 40) were assigned to 1 of 4 iso-lipid and isonitrogenous concentrate diets fed for ad libitum intake for a 100-d finishing period. Concentrates were supplemented with one of the following: 1) 6% SO (CON); 2) 6% SO + 1% FO (FO1); 3) 6% SO + 2% FO (FO2); or 4) 8% palmitic acid for the first 50 d and 6% SO + 2% FO for the second 50 d [FO2(50)]. Samples of LM were harvested and concentrations of fatty acids were measured. Total RNA was isolated and the gene expression of {Delta}9-desaturase was determined. The mRNA expression of putative regulators of {Delta}9-desaturase gene expression, sterol regulatory element binding protein-1c (SREBP-1c) and peroxisome proliferator activated receptor-{alpha} (PPAR-{alpha}), were also measured in the CON and FO2 groups. Expression of mRNA for {Delta}9-desaturase was decreased (P < 0.05) 2.6-, 4.4-, and 4.9-fold in FO1, FO2(50), and FO2 compared with CON, respectively. Expression of {Delta}9-desaturase mRNA tended to be reduced (P = 0.09) by increasing FO from 1 to 2%, but was not affected by duration of supplementation (P > 0.24). Expression of mRNA for SREBP-1c was decreased 2-fold in FO2 compared with CON (P < 0.05), whereas expression of PPAR-{alpha} was not affected (P > 0.30). There was a positive relationship between {Delta}9-desaturase and SREBP-1c gene expression (P < 0.01), but the expression of both genes was negatively related to tissue concentrations of n-3 PUFA (P < 0.05) and positively related to concentration of n-6 PUFA (P < 0.01). Simultaneous enhancement of tissue concentrations of CLA and n-3 PUFA concentrations in bovine muscle may be hindered by negative interactions between n-3 PUFA and {Delta}9-desaturase gene expression, possibly mediated through reduced expression of SREBP-1c.

Key Words: beef cattle • conjugated linoleic acid • {Delta}9-desaturase • fish oil • n-3 polyunsaturated fatty acids • sterol regulatory element binding protein-1c






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