Dipartimento di Agronomia e Gestione dell'Agroecosistema, University of Pisa, 56124, Italy.
J Dairy Sci. 2010 Feb;93(2):753-63. doi: 10.3168/jds.2009-2581.
Several lipogenic genes have been shown to have effects on lipid metabolism: stearoyl CoA desaturase 1 (SCD1) catalyzes the desaturation of several fatty acids (FA) in the cis-Delta(9) position in mammary glands of ruminant animals, diacylglycerol acyltransferase 1 (DGAT1) is a key enzyme in triacylglycerol synthesis in the mammary gland, and sterol regulatory element binding protein (SREBP-1) is a transcription factor that regulates expression levels of the SCD1 gene and other genes relevant to lipid and FA metabolism in adipose tissue and mammary gland. In this work, 351 Italian Brown cows were genotyped for polymorphisms in the SCD1, SREBP-1, and DGAT1 genes to reveal the allelic distribution in the population. Subsequently, effects on individual milk FA composition and on cis-9 unsaturated/saturated FA ratios, a proxy of mammary stearoyl CoA desaturase activity, were investigated. The genotypes of SCD1 (A293V) and DGAT1 (K232A) were determined by an approach based on the ligation detection reaction and a universal array, whereas the genotype of SREBP-1 (84-bp insertion-deletion) was revealed by PCR amplification of intron 5. The genotype analysis showed an unbalanced distribution of alleles within all genes, being the allele with higher gene frequency at 82, 84, and 98% for SCD1, SREBP-1, and DGAT1, respectively. Significant associations between SCD1 and DGAT1 polymorphisms and milk FA composition were found, whereas SREBP-1 polymorphism was not associated with milk FA composition. In particular, SCD1 showed significant association with C14:1 cis-9 and C14:1 cis-9/C14:0, which is considered the best proxy of the desaturation activity in mammary gland. The DGAT1 polymorphism had the strongest association with milk FA composition, which confirmed the key role of DGAT1 in lipid metabolism of mammary gland. However, the unbalanced distribution of alleles in all polymorphisms investigated suggested that the size of population should be increased to confirm the results of the present study.
硬脂酰辅酶 A 去饱和酶 1（SCD1）催化反式-Delta（9）位置的几种脂肪酸（FA）在反刍动物乳腺中的去饱和，二酰基甘油酰基转移酶 1（DGAT1）是乳腺中三酰基甘油合成的关键酶，固醇调节元件结合蛋白（SREBP-1）是一种转录因子，调节脂肪组织和乳腺中 SCD1 基因和其他与脂质和 FA 代谢相关基因的表达水平。在这项工作中，对 351 头意大利棕色奶牛进行了 SCD1、SREBP-1 和 DGAT1 基因多态性的基因分型，以揭示其在群体中的等位基因分布。随后，研究了对个体乳 FA 组成和反式-9 不饱和/饱和 FA 比值（乳腺硬脂酰辅酶 A 去饱和酶活性的替代物）的影响。SCD1（A293V）和 DGAT1（K232A）的基因型是通过基于连接检测反应和通用阵列的方法确定的，而 SREBP-1（84-bp 插入-缺失）的基因型是通过 5 号内含子的 PCR 扩增揭示的。基因型分析表明，所有基因内的等位基因分布不平衡，SCD1、SREBP-1 和 DGAT1 的高基因频率等位基因分别为 82%、84%和 98%。发现 SCD1 和 DGAT1 多态性与乳 FA 组成之间存在显著关联，而 SREBP-1 多态性与乳 FA 组成无关。特别是，SCD1 与 C14:1 cis-9 和 C14:1 cis-9/C14:0 显著相关，这被认为是乳腺去饱和活性的最佳替代物。DGAT1 多态性与乳 FA 组成的关联最强，这证实了 DGAT1 在乳腺脂质代谢中的关键作用。然而，在所研究的所有多态性中，等位基因的不平衡分布表明应该增加群体规模以确认本研究的结果。
