Developmental Relationship of Unsaturated Fatty Acid Composition and Stearoyl-CoA Desaturase mRNA Level in Hanwoo Steers` Muscle

Seung-Hwan Lee,Soo-Han Hwang,Il-Cheong Cheong,Chang-Soo Lee,Eun-Young Cheong,Nag-Jin Choi,Sung-Jong Oh,Du-Hak Yoon

doi:10.5713/ajas.2005.562

Abstract

This study was conducted to investigate the developmental relationship between fatty acid composition in different lipid fractions and stearoyl-CoA desaturase (SCD) gene expression in steer muscles during growth. Twenty Hanwoo steers were used at 6, 12, 18, 24 and 30 months of age. Fatty acid composition and SCD mRNA level were analyzed. In the total lipid fraction, developmental profiles of C18:1, as the product of SCD enzyme, and SCD mRNA level were significantly increased between 6 months and 12 months of age. During this period, the percentage of C18:1 increased from 31.9% to 49.5% in the total lipid. The increased C18:1 level was maintained until 30 months of age within the range of 44.8- 49.9%. In contrast, the C18:0 composition decreased with age and this decrease was compensated by the increase of the C18:1. However, the sum of C18:0 and C18:1 was changed before and after 12- month old by a 20% increase. Unlike the C18 fatty acids, the C16 fatty acids such as C16:0 and C16:1 did not show a consistent change with age in steers' muscle. On the other hand, C18:2 proportion as a major polyunsaturated fatty acid in muscle was significantly reduced from 21.1% at 6 months of age to 4.4% at 12-months old and then this reduced level was maintained until 30 months within the range of 7.4-11.4%. As in the C18:1 composition during early stages, a 2-fold significant increase was observed in the ∆ 9 -desaturase index of C18 fatty acid as a measure of SCD activity , but not in that of C16 fatty acid. Also, the steady-state level of SCD mRNA reached a peak at 12 months of age. Thus, the positive relationship between the C18:1 composition and the ∆ 9 -desaturase (SCD enzyme) index of C18 fatty acid or SCD mRNA level was demonstrated during growth, but the negative relationship between the C18:2 composition and the above three indices was demonstrated at the same time, indicating that the sharp induction of SCD mRNA may be closely related to the dramatic reduction of C18:2, which is known as a suppressor of SCD gene expression during growth. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 4 : 562-566)

Highlights

There has been a lot of interest in increasing unsaturated fatty acids in beef and decreasing saturated fatty acids due to their effects on human health
Ruminant animals in general have relatively high ratios of saturated to monounsaturated fatty acids in their lipids (Harfoot and Hazlewood, 1988), which are consumed by humans as marbled meat and milk products
High levels of unsaturated fatty acids in ruminants are desirable for human health (Malau-Aduli et al, 1997)

Summary

Introduction

There has been a lot of interest in increasing unsaturated fatty acids in beef and decreasing saturated fatty acids due to their effects on human health. The consumption of high levels of saturated fat in human diet, in conjunction with obesity, is a major risk factor for the development of vascular and coronary diseases (Department of Health, 1994). Monounsaturated fatty acid lowers serum LDL cholesterol and thereby may have a positive effect on coronary heart disease (Salter et al, 1998). Ruminant animals in general have relatively high ratios of saturated to monounsaturated fatty acids in their lipids (Harfoot and Hazlewood, 1988), which are consumed by humans as marbled meat and milk products. High levels of unsaturated fatty acids in ruminants are desirable for human health (Malau-Aduli et al, 1997). Efforts to increase the unsaturated fatty acid content of ruminant tissues have been tried through dietary supplement or genetic selection

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Results