Wasowska I, Maia M R G, Niedźwiedzka K M, Czauderna M, Ribeiro J M C Ramalho, Devillard E, Shingfield K J, Wallace R J
Rowett Research Institute, Bucksburn, Aberdeen, UK.
Br J Nutr. 2006 Jun;95(6):1199-211. doi: 10.1079/bjn20061783.
Dietary cis-9, trans-11-conjugated linoleic acid (CLA) is generally thought to be beneficial for human health. Fish oil added to ruminant diets increases the CLA concentration of milk and meat, an increase thought to arise from alterations in ruminal biohydrogenation of unsaturated fatty acids. To investigate the mechanism for this effect, in vitro incubations were carried out with ruminal digesta and the main biohydrogenating ruminal bacterium, Butyrivibrio fibrisolvens. Linoleic acid (LA) or alpha-linolenic acid (LNA) was incubated (1.67 g/l) with strained ruminal digesta from sheep receiving a 50:50 grass hay-concentrate ration. Adding fish oil (up to 4.17 g/l) tended to decrease the initial rate of LA (P=0.025) and LNA (P=0.137) disappearance, decreased (P<0.05) the transient accumulation of conjugated isomers of both fatty acids, and increased (P<0.05) the accumulation of trans-11-18:1. Concentrations of EPA (20:5n-3) or DHA (22:6n-3), the major fatty acids in fish oil, were low (100 mg/l or less) after incubation of fish oil with ruminal digesta. Addition of EPA or DHA (50 mg/l) to pure cultures inhibited the growth and isomerase activity of B. fibrisolvens, while fish oil had no effect. In contrast, similar concentrations of EPA and DHA had no effect on biohydrogenation of LA by mixed digesta, while the addition of LA prevented metabolism of EPA and DHA. Neither EPA nor DHA was metabolised by B. fibrisolvens in pure culture. Thus, fish oil inhibits ruminal biohydrogenation by a mechanism which can be interpreted partly, but not entirely, in terms of its effects on B. fibrisolvens.
膳食中的顺-9，反-11-共轭亚油酸（CLA）通常被认为对人体健康有益。添加到反刍动物日粮中的鱼油会提高牛奶和肉类中的CLA浓度，这种增加被认为是由于不饱和脂肪酸瘤胃生物氢化作用的改变所致。为了研究这种作用的机制，用瘤胃消化物和主要的瘤胃生物氢化细菌——溶纤维丁酸弧菌进行了体外培养。将亚油酸（LA）或α-亚麻酸（LNA）（1.67 g/l）与来自采食50:50干草-精料日粮的绵羊的过滤瘤胃消化物一起培养。添加鱼油（高达4.17 g/l）倾向于降低LA（P = 0.025）和LNA（P = 0.137）消失的初始速率，降低（P < 0.05）两种脂肪酸共轭异构体的瞬时积累，并增加（P < 0.05）反-11-18:1的积累。鱼油与瘤胃消化物培养后，鱼油中的主要脂肪酸二十碳五烯酸（EPA，20:5n-3）或二十二碳六烯酸（DHA，22:6n-3）的浓度较低（100 mg/l或更低）。向纯培养物中添加EPA或DHA（50 mg/l）会抑制溶纤维丁酸弧菌的生长和异构酶活性，而鱼油则没有影响。相反，类似浓度的EPA和DHA对混合消化物对LA的生物氢化没有影响，而添加LA会阻止EPA和DHA的代谢。在纯培养中，溶纤维丁酸弧菌既不代谢EPA也不代谢DHA。因此，鱼油通过一种机制抑制瘤胃生物氢化作用，这种机制可以部分但不能完全根据其对溶纤维丁酸弧菌的影响来解释。
