Navarro V, Fernández-Quintela A, Churruca I, Portillo M P
Department of Nutrition and Food Science, University of Pais Vasco, Paseo de la Universidad 7, 01006 Vitoria, Spain.
J Physiol Biochem. 2006 Jun;62(2):137-47. doi: 10.1007/BF03174074.
Different reasons which justify differences between rodents and humans in body fat reduction produced by conjugated linoleic acid (CLA) could be proposed. The doses used in humans are lower than those used in rodents. Human experiments have been performed with CLA isomer mixtures instead of isolated isomers. The variable dilution of t-10, c-12, the active isomer, among different preparations might explain the reduced responsiveness in humans. Diet composition may modulate CLA effects on body fat accumulation. As far as human studies are concerned, a specific dietary pattern has not been established. As a result differences among studies and also among subjects in the same study are likely. In rodents, the effects of CLA vary with genotype, suggesting that genetic predisposition to fat accumulation can play an important role in the effectiveness of CLA. Human volunteers with different body mass index have participated in the published studies and even in the same experiment. So, differences in lipid metabolism among subjects could help to explain the discrepancies observed in the literature. Age and maturity may also be crucial. Experiments using rodents have been conducted with growing animals and there is little evidence of CLA effectiveness in adult animals. By contrast, human studies have been performed with adults. Inhibition of lipogenesis in white adipose tissue is one of the mechanisms which have been proposed to explain the body-fat lowering effect of CLA, but lipogenesis in this tissue is very low in humans. Another mechanism suggested is increased fatty acid oxidation in the liver associated with peroxisome proliferation, but humans are relatively insensitive to this effect.
共轭亚油酸（CLA）在啮齿动物和人类身上产生的体脂减少差异，可能有不同的原因。人类使用的剂量低于啮齿动物。人体实验使用的是CLA异构体混合物，而非分离出的异构体。不同制剂中活性异构体t-10, c-12的可变稀释度，可能解释了人类反应性降低的原因。饮食组成可能会调节CLA对体脂积累的影响。就人体研究而言，尚未确立特定的饮食模式。因此，不同研究之间以及同一研究中的不同受试者之间都可能存在差异。在啮齿动物中，CLA的效果因基因型而异，这表明脂肪积累的遗传易感性可能在CLA的有效性中发挥重要作用。不同体重指数的人类志愿者参与了已发表的研究，甚至在同一实验中也是如此。因此，受试者之间的脂质代谢差异可能有助于解释文献中观察到的差异。年龄和成熟度也可能至关重要。对啮齿动物进行的实验是在生长中的动物身上进行的，几乎没有证据表明CLA在成年动物中有效果。相比之下，人体研究是在成年人身上进行的。抑制白色脂肪组织中的脂肪生成是被提出来解释CLA降低体脂作用的机制之一，但该组织中的脂肪生成在人类中非常低。另一种提出的机制是肝脏中与过氧化物酶体增殖相关的脂肪酸氧化增加，但人类对这种作用相对不敏感。
