Mosley Erin E, Powell Gary L, Riley Melissa B, Jenkins Thomas C
Department of Animal and Veterinary Sciences, Clemson University, Clemson, SC 29634, USA.
J Lipid Res. 2002 Feb;43(2):290-6.
Ruminant products are significant sources of dietary trans fatty acids. Trans fatty acids, including various conjugated linoleic acid isomers, have been shown to act as metabolic modifiers of lipid metabolism. Trans fatty acids originate from biohydrogenation of dietary unsaturated fatty acids by gut microbes; however, the exact synthetic pathways are unclear. It was our goal to examine the biohydrogenation pathway for oleic acid, where oleic acid is hydrogenated directly to stearic acid. Our objective in this study was to trace the time course of appearance of 13C in labeled oleic acid to determine if trans monoenes are formed from the 13C-labeled oleic acid or if the 13C appears only in stearic acid as described in reviews of earlier work. Enrichments were calculated from the mass abundance of 13C in major fatty acid fragments and expressed as a percentage of total carbon isotopomers. Significant 13C enrichment was found in stearic acid, oleic acid, trans-6, trans-7, and in all trans C18:1 in positions 9-16. We concluded that the biohydrogenation of oleic acid by mixed ruminal microbes involves the formation of several positional isomers of trans monoenes rather than only direct biohydrogenation to form stearic acid as previously described.
反刍动物产品是膳食反式脂肪酸的重要来源。反式脂肪酸，包括各种共轭亚油酸异构体，已被证明可作为脂质代谢的代谢调节剂。反式脂肪酸源于肠道微生物对膳食不饱和脂肪酸的生物氢化作用；然而，确切的合成途径尚不清楚。我们的目标是研究油酸的生物氢化途径，即油酸直接氢化为硬脂酸的过程。我们在本研究中的目的是追踪标记油酸中13C出现的时间进程，以确定反式单烯是否由13C标记的油酸形成，或者13C是否仅如早期工作综述中所述出现在硬脂酸中。通过主要脂肪酸片段中13C的质量丰度计算富集量，并表示为总碳同位素异构体的百分比。在硬脂酸、油酸、反式-6、反式-7以及9-16位的所有反式C18:1中均发现了显著的13C富集。我们得出结论，瘤胃混合微生物对油酸的生物氢化作用涉及形成几种反式单烯的位置异构体，而不是如先前所述仅直接生物氢化为硬脂酸。
