Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany.
J Dairy Sci. 2012 Jul;95(7):3905-18. doi: 10.3168/jds.2011-4835.
Supplementation of conjugated linoleic acids (CLA) reduces milk fat content in dairy cows and, thus, may be a useful dietary strategy to improve energy balance during early lactation. The present study was performed to investigate whether supplementation of CLA could have adverse effects on hepatic lipid metabolism such as observed in rodents. For this aim, 40 Holstein cows were allotted to 2 groups, which were fed daily 172 g of either a CLA-free, rumen-protected control fat (control group) or a rumen-protected CLA fat supplying 4.3g of cis-9,trans-11 CLA and 3.8 g of trans-10,cis-12 CLA per day (CLA group). To identify potential changes of lipid metabolism, expression of several genes involved in lipid metabolism was determined in liver biopsy samples taken at wk 5 of lactation, using a whole-genome gene chip. In the CLA group, milk fat content and daily milk fat yield were lower than in the control group. Milk yield was higher, whereas fat-corrected milk and energy-corrected milk were lower in the CLA group than in the control group. The CLA group, moreover, had an improved energy balance. To study potential effects of CLA on hepatic lipid metabolism, we considered 6 genes encoding fatty acid transporters, 7 genes involved in intracellular fatty acid transport, 21 and 7 genes, respectively, involved in mitochondrial and peroxisomal β-oxidation, 6 genes of carnitine metabolism, 3 genes of ketogenesis, 21 genes involved in fatty acid and triacylglycerol synthesis, 17 genes involved in cholesterol metabolism, and 20 genes involved in lipoprotein metabolism. None of these genes was differentially regulated between the CLA group and the control group. Gene chip data were confirmed by quantitative PCR analysis, which revealed no difference in the expression of key enzymes of various pathways such as lipogenesis, β-oxidation, and ketogenesis between the 2 groups of cows. In line with those findings, concentrations of triacylglycerols and cholesterol in liver and plasma were not different between the 2 groups of cows. In conclusion, the present study shows that CLA supplementation at a dose effective for milk fat depression does not induce adverse effects on hepatic lipid metabolism in dairy cows.
反式共轭亚油酸（CLA）的补充可以降低奶牛乳脂含量，因此，在泌乳早期可能是一种改善能量平衡的有用的饮食策略。本研究旨在研究 CLA 的补充是否会对肝脏脂质代谢产生不利影响，就像在啮齿动物中观察到的那样。为此，将 40 头荷斯坦奶牛分为两组，每天分别饲喂 172g 无 CLA 的保护瘤胃脂肪（对照组）或提供 4.3g 顺式-9，反式-11CLA 和 3.8g 反式-10，顺式-12CLA 的保护瘤胃 CLA 脂肪（CLA 组）。为了确定脂质代谢的潜在变化，在泌乳第 5 周时使用全基因组基因芯片测定了肝脏活检样本中参与脂质代谢的几个基因的表达。在 CLA 组中，乳脂含量和日乳脂产量低于对照组。CLA 组的产奶量高于对照组，而校正脂肪和校正能量的牛奶产量则低于对照组。此外，CLA 组的能量平衡得到改善。为了研究 CLA 对肝脏脂质代谢的潜在影响，我们考虑了编码脂肪酸转运蛋白的 6 个基因、参与细胞内脂肪酸转运的 7 个基因、分别参与线粒体和过氧化物酶体β-氧化的 21 个和 7 个基因、肉碱代谢的 6 个基因、酮生成的 3 个基因、脂肪酸和三酰甘油合成的 21 个基因、胆固醇代谢的 17 个基因和脂蛋白代谢的 20 个基因。这些基因在 CLA 组和对照组之间均无差异调节。基因芯片数据通过定量 PCR 分析得到证实，两组奶牛各途径关键酶的表达（如脂肪生成、β-氧化和酮生成）无差异。这些发现与 2 组奶牛的肝脏和血浆中三酰甘油和胆固醇浓度无差异的结果一致。总之，本研究表明，CLA 的补充剂量有效降低乳脂含量，但不会对奶牛肝脏脂质代谢产生不利影响。
