Corl Benjamin A, Baumgard Lance H, Griinari J Mikko, Delmonte Pierluigi, Morehouse Kim M, Yurawecz Martin P, Bauman Dale E
Department of Animal Science, Cornell University, Ithaca, New York, USA.
Lipids. 2002 Jul;37(7):681-8. doi: 10.1007/s11745-002-0949-4.
Cis-9,trans-11 and trans-7,cis-9 CLA are the most prevalent CLA isomers in milkfat. The majority of cis-9,trans-11 CLA is synthesized endogenously by delta9-desaturase. We tested the hypothesis that trans-7,cis-9 CLA originates from endogenous synthesis by inhibiting delta9-desaturase with a source of cyclopropene FA (sterculic oil: SO) or with a trans-10,cis-12 CLA supplement. Experiment 1 (four cows; Latin square) involved four treatments: control, SO, partially hydrogenated vegetable oil (PHVO), and PHVO + SO. Milk, plasma, and rumen fluid were collected. Experiment 2 treatments (four cows) were 0 or 14.0 g/d of 10,12 CLA supplement; milk and plasma were collected. Samples were analyzed by GC and Ag+-HPLC to determine FA. In Experiment 1, SO decreased milkfat content of trans-7,cis-9 CLA by 68 to 71% and cis-9,trans-11 CLA by 61 to 65%. In Experiment 2, the 10,12 CLA supplement decreased milkfat content of trans-7,cis-9 CLA and cis-9,trans-11 by 44 and 25%, respectively. Correcting for the extent of treatment-induced inhibition of delta9-desaturase based on changes in myristic and myristoleic acids, endogenous synthesis of trans-7,cis-9 CLA represented 85 and 102% in Experiments 1 and 2, respectively. Similar corrected values were 77 and 58% for endogenous synthesis of cis-9,trans-11 CLA. Thus, milkfat cis-9,trans-11 CLA was primarily from endogenous synthesis with a minor portion from rumen escape. In contrast, trans-7,cis-9 CLA was not present in rumen fluid in significant amounts. Results indicate this isomer in milkfat is derived almost exclusively from endogenous synthesis via delta9-desaturase.
顺-9，反-11共轭亚油酸（CLA）和反-7，顺-9 CLA是乳脂肪中最常见的CLA异构体。大部分顺-9，反-11 CLA是由Δ9-去饱和酶内源性合成的。我们通过用环丙烯脂肪酸源（苹婆油：SO）或反-10，顺-12 CLA补充剂抑制Δ9-去饱和酶，来验证反-7，顺-9 CLA源自内源性合成的假说。实验1（4头奶牛；拉丁方设计）涉及4种处理：对照、SO、部分氢化植物油（PHVO）以及PHVO+SO。收集牛奶、血浆和瘤胃液。实验2的处理（4头奶牛）为每天补充0或14.0 g的10,12 CLA；收集牛奶和血浆。通过气相色谱法（GC）和银离子高效液相色谱法（Ag+-HPLC）分析样品以测定脂肪酸。在实验1中，SO使乳脂肪中反-7，顺-9 CLA含量降低了68%至71%，使顺-9，反-11 CLA含量降低了61%至65%。在实验2中，10,12 CLA补充剂使乳脂肪中反-7，顺-9 CLA和顺-9，反-11 CLA含量分别降低了44%和25%。根据肉豆蔻酸和肉豆蔻油酸的变化对处理诱导的Δ9-去饱和酶抑制程度进行校正后，实验1和实验2中反-7，顺-9 CLA的内源性合成分别占85%和102%。顺-9，反-11 CLA内源性合成的类似校正值分别为77%和58%。因此，乳脂肪中的顺-9，反-11 CLA主要来自内源性合成，一小部分来自瘤胃逃逸。相比之下，瘤胃液中反-7，顺-9 CLA的含量并不显著。结果表明，乳脂肪中的这种异构体几乎完全源自通过Δ9-去饱和酶的内源性合成。
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