Shi Huaiping, Zhang Tianying, Li Cong, Wang Jianjue, Huang Jiangtao, Li Zhongyang
College of Animal Science and Technology, Northwest A&F University , Yangling, Shaanxi 712100, People's Republic of China.
J Agric Food Chem. 2017 Nov 1;65(43):9460-9467. doi: 10.1021/acs.jafc.7b02377. Epub 2017 Oct 19.
The molecular mechanisms on milk fat depression (MFD) in response to trans-10,cis-12-conjugated linoleic acid (t10,c12-CLA) supplementation in ruminants were elucidated in this research with dairy goats. A total of 30 2-year-old Xinong Saanen dairy goats [40 ± 5 days in milk (DIM)] at peak lactation stage were assigned to a 3 × 3 Latin square design (14 day treatment period, followed with 14 day washout). Three CLA treatments included (a) control, fed the basal diet only without CLA supplementation; (b) orally supplemented with 8 g/day of lipid-encapsulated CLA (low dose, CLA-1); and (c) orally supplemented with 16 g/day of lipid-encapsulated CLA (high dose, CLA-2). Expression levels of fatty acid metabolism genes in the mammary tissues were analyzed by real-time quantitative polymerase chain reaction (RT-qPCR) in three goats on day 1 and the other three goats on day 14 in each group after the discontinuation of CLA treatment in the third experimental period. Dietary supplementation of CLA led to a significant decrease of milk fat compared to the control (p < 0.05). Milk fat concentrations in CLA-1 and CLA-2 groups were 2.74 and 2.42%, respectively, while the milk fat concentration in the control group was 2.99%. Decreases in short- and medium-chain fatty acids (<16 carbons) and increases in unsaturated fatty acids were observed in the CLA-2 group (p < 0.05). The desaturation indexes of C16 and C18 fatty acids were obviously increased (p < 0.01). RT-qPCR results revealed decreases of the mRNA expression levels of SREBF1, PPARG, LPL, CD36, FABP3, ACSL1, FASN, ACACA, DGAT2, TIP47, ADRP, and BTN1A1 genes in mammary glands (p < 0.05) and an increase of the SCD gene because of CLA supplementation (p < 0.05). In conclusion, t10,c12-CLA-induced MFD was possibly the result from the downregulation of genes involved in lipogenesis in goat mammary glands.
本研究以奶山羊为对象，阐明了反刍动物补充反式-10，顺式-12-共轭亚油酸（t10，c12-CLA）后乳脂降低（MFD）的分子机制。选取30只处于泌乳高峰期的2岁西农萨能奶山羊[产奶天数（DIM）为40±5天]，采用3×3拉丁方设计（14天处理期，随后14天洗脱期）。三种CLA处理包括：（a）对照组，仅饲喂基础日粮，不补充CLA；（b）口服补充8克/天的脂质包封CLA（低剂量，CLA-1）；（c）口服补充16克/天的脂质包封CLA（高剂量，CLA-2）。在第三个实验期CLA处理停止后，于第1天每组选3只山羊、第14天每组选另外3只山羊，通过实时定量聚合酶链反应（RT-qPCR）分析乳腺组织中脂肪酸代谢基因的表达水平。与对照组相比，日粮中补充CLA导致乳脂显著降低（p<0.05）。CLA-1组和CLA-2组的乳脂浓度分别为2.74%和2.42%，而对照组的乳脂浓度为2.99%。CLA-2组中短链和中链脂肪酸（<16个碳）减少，不饱和脂肪酸增加（p<0.05）。C16和C18脂肪酸的去饱和指数明显升高（p<0.01）。RT-qPCR结果显示，CLA补充导致乳腺中SREBF1、PPARG、LPL、CD36、FABP3、ACSL1、FASN、ACACA、DGAT2、TIP47、ADRP和BTN1A1基因的mRNA表达水平降低（p<0.05），而SCD基因表达增加（p<0.05）。总之，t10，c12-CLA诱导的MFD可能是山羊乳腺中脂肪生成相关基因下调的结果。
