Milk Fatty Acid Unsaturation: Genetic Parameters and Effects of Stearoyl-CoA Desaturase (SCD1) and Acyl CoA: Diacylglycerol Acyltransferase 1 (DGAT1)

Abstract

With regard to human health aspects of milk fat, increasing the amount of unsaturated fatty acids in milk is an important selection objective. The cow's diet has an influence on the degree of unsaturation, but literature suggests that genetics also plays a role. To estimate genetic variation in milk fatty acid unsaturation indices, milk fatty acid composition of 1,933 Dutch Holstein Friesian heifers was measured and unsaturation indices were calculated. An unsaturation index represents the concentration of the unsaturated product proportional to the sum of the unsaturated product and the saturated substrate. Intraherd heritabilities were moderate, ranging from 0.23 +/- 0.07 for conjugated linoleic acid (CLA) index to 0.46 +/- 0.09 for C16 index. We genotyped the cows for the SCD1 A293V and DGAT1 K232A polymorphisms, which are known to alter milk fatty acid composition. Both genes explain part of the genetic variation in unsaturation indices. The SCD1 V allele is associated with lower C10, C12, and C14 indices, and with higher C16, C18, and CLA indices in comparison to the SCD1 A allele, with no differences in total unsaturation index. In comparison to the DGAT1 K allele, the DGAT1 A allele is associated with lower C10, C12, C14, and C16 indices and with higher C18, CLA, and total indices. We conclude that selective breeding can contribute to higher unsaturation indices, and that selective breeding can capitalize on genotypic information of both the SCD1 A293V and the DGAT1 K232A polymorphism.

MicroRNA-26a/b and their host genes synergistically regulate triacylglycerol synthesis by targeting theINSIG1gene

“…Both DGAT1 and AGPAT6 are key components of the overall pathway leading to synthesis of milk lipid droplets and affect milk fat yield and composition. 42 , 41 , 33 Although the expression of AGPAT6 did not change, the fact that overexpression of miR-26a/b and their host genes had a significant effect on DGAT1 mRNA expression provides evidence of a mechanistic link between the miRNA and the process of desaturation and esterification…”

Characterization of milk fatty acids based on genetic and herd parameters

“…Note that % genetic differs from the intraherd heritability as defined by Stoop et al (2008) and Schennink et al (2007Schennink et al ( , 2008. Herd correlations were estimated using bivariate analyses and model 1 as:…”

“…Fatty acids were grouped into 5 groups based on general knowledge about their synthesis; (1) evenchain saturated FA (C4:0-C16:0), (2) odd-chain saturated FA (C5:0-C17:0), (3) branched-chain FA, (4) C18 FA including C20:0 and (5) cis 9-unsaturated FA. Results on 16 of the major FA have been published previously (Schennink et al 2008;Stoop et al 2008). Here we will additionally report parameters for 23 FA that occur in lower concentrations.…”

Effect of polymorphisms in the ABCG2, LEPR and SCD1 genes on milk production traits in Holstein cows

“…In the presence of prolactin, leptin has been shown to increase fatty acid synthesis in the mammary gland (Feuermann et al, 2004). Furthermore, in support of the authors' hypothesis, it has been demonstrated that leptin, acting through its receptor, modulates some functions of DGAT1 (Chen et al, 2002) as a key enzyme in triacylglycerol synthesis (Schennink et al, 2008), though the underlying physiological mechanisms remain unclear. The threonine → methionine amino acid substitution in the intracellular domain of LEPR may change its signalling capability.…”

“…The enzyme is abundantly expressed in the mammary gland of lactating ruminants and plays a major role in the synthesis of milk fat (Bionaz & Loor, 2008). An SNP in exon 5 of the bovine SCD1, which causes the replacement of valine with alanine at residue 293 (SCD1-A293V), has been reported to be associated with milk fatty acid composition in various cattle populations (Mele et al, 2007;Schennink et al, 2008;Kgwatalala et al, 2009). However, literature that reports a significant effect of this polymorphism on milk production traits is limited, though an effect of this SNP on milk and protein yield has been described in Italian Holsteins (Macciotta et al, 2008) and Canadian Jerseys (Kgwatalala et al, 2009).…”