The main objective of this study was to investigate the effects of increasing dietary supplementation of crushed sunflower seeds (CSS) in dairy cow diet on mammary expression of genes involved in de novo fatty acid (FA) synthesis, FA desaturation, FA transport/uptake, cholesterol homeostasis, and regulation of transcription. Twenty-four cows were allocated to one of four diets supplemented with CSS at 0% (Control), 5%, 10%, or 15% of dry matter in randomized block design. After a five week experimental period, mammary tissue was biopsied, and milk and plasma samples were obtained. Milk proportion of preformed FA was increased at all levels of CSS supplementation while the proportion of FA ≤ C16 was reduced. This change in milk fat composition was reflected in a sustained mammary transcription of genes involved in FA transport, i.e. Lipoprotein Lipase (LPL), Fatty Acid Binding Protein 3 (FABP3), and FA Translocase, and a reduced transcription of a gene involved in regulation of transcription, i.e. Sterol Response Element Binding Factor 1 (SREBF1) as well as genes involved in FA synthesis in cows supplemented with CSS. Milk proportion of unsaturated fatty acids (UFA) was increased from 27.5% in control to 40.3% and 43.0% of total FA in cows supplemented with 10 and 15% CSS, respectively, in spite of reduced mammary transcription of two desaturase enzymes, i.e. Stearoyl CoA Desaturase 1 (SCD1) and FA Desaturase 1 (FADS1) in these two treatment groups. Transcription of Sterol Response Element Binding Protein Cleavage Activating Protein (SCAP), Niemann Pick disease type 1C (NPC1) and Acetyl-CoA Carboxylase α (ACAC) were also reduced by CSS supplementation to various degrees. Transcription of Insulin Induced Gene 1 (INSIG1), FA Desaturase 2 (FADS2), and ATP Binding Cassette, sub-family G member 2 (ABCG2) was not significantly changed by CSS supplementation. Our data show a coordinated down-regulation of mammary transcription of major lipogenic transcription factor, SREBF1, its target genes FAS and ACAC, and its activator protein SCAP during lipid supplementation even though overall milk fat secretion was unaltered.

这项研究的主要目的是调查奶牛日粮中增加日粮添加碾碎向日葵种子（CSS）对涉及新生基因的乳腺表达的影响。脂肪酸（FA）合成，FA脱饱和，FA转运/摄取，胆固醇稳态和转录调控。在随机区组设计中，将24头奶牛分配到4种添加CSS的日粮中，其中0％（对照），5％，10％或15％干物质。经过五周的实验期后，对乳腺组织进行活检，并获得牛奶和血浆样品。在所有添加CSS的情况下，预成型FA的牛奶比例都会增加，而FA≤C16的比例会降低。乳脂成分的这种变化反映在与FA转运有关的基因的持续乳腺转录中，即脂蛋白脂酶（LPL），脂肪酸结合蛋白3（FABP3））和FA Translocase，以及在补充CSS的奶牛中参与转录调控的基因（即Sterol Response Element Binding Factor 1（SREBF1））和参与FA合成的基因的转录降低。尽管两种去饱和酶即硬脂酰酶的乳腺转录降低，但补充有10％和15％CSS的母牛的乳中不饱和脂肪酸（UFA）的比例分别从对照组的27.5％增至总FA的40.3％和43.0％。这两个治疗组中的CoA去饱和酶1（SCD1）和FA去饱和酶1（FADS1）。Niemann Pick病1C型（NPC1）的甾醇反应元件结合蛋白裂解激活蛋白（SCAP）的转录。）和CSS补充也降低了乙酰辅酶A羧化酶α（ACAC）。补充CSS并没有显着改变胰岛素诱导基因1（INSIG1），FA去饱和酶2（FADS2）和ATP结合盒的转录，亚家族G成员2（ABCG2）。我们的数据显示，在补充脂质的过程中，主要的脂肪生成转录因子SREBF1，其靶基因FAS和ACAC及其激活蛋白SCAP的乳腺转录的协调下调，即使总体乳脂分泌不变。