J. Anim Sci.
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Published online first on September 12, 2008
J. Anim Sci. 1910. doi:10.2527/jas.2008-1005
© 2008 American Society of Animal Science
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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 cattle

Sinéad M. Waters1, James P. Kelly2, Padraic O’Boyle1, Aidan P. Moloney1 and David A. Kenny2

1 Teagasc, Animal Bioscience Centre, Grange, Dunsany, Co. Meath, Ireland 2 School of Agriculture, Food Science & Veterinary Medicine, University College Dublin, Belfield, Dublin 4. Ireland

Sinead.Waters{at}teagasc.ie

Abstract

The objective of this study was to examine the effect of level and duration of feeding of a 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 isolipid and isonitrogenous concentrate diets, fed for ad libitum intake, for a 100-d finishing period. Concentrates were supplemented with one of the following: (i) 6% SO (CON); (ii) 6% SO + 1% FO (FO1); (iii) 6% SO + 2% FO (FO2); or (iv) 8% palmitic acid for the first 50 d and 6% SO + 2% FO for the latter 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 on FO2 compared with CON (P < 0.05), whereas 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 n-6 PUFA concentration (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 • {triangleup}-9 desaturase • fish oil • n-3 PUFA • SREBP-1c






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