Differences between humans and mice in efficacy of the body fat lowering effect of conjugated linoleic acid: role of metabolic rate.
Differences between humans and mice in efficacy of the body fat lowering effect of conjugated linoleic acid: role of metabolic rate.
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DOI：
10.1093/jn/131.7.2067
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发表时间：
2001-07
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通讯作者：
A. Terpstra
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作者：
A. Terpstra
(1-6) 并且这种效应是通过增加能量消耗来介导的 (5-7)。 CLA 的降低体脂作用在人类中也有报道 (8 ‐12)，但似乎不如小鼠显着。给药剂量或喂养时间的长短可以部分解释小鼠和人类之间影响程度的差异，但代谢率的差异可能起着主要作用。不同体型哺乳动物的基础代谢率或能量消耗与体重之间的关系由函数 Y 5 aX 0.75 描述，其中 Y 是基础代谢率（kJ/d），X 是体重（kg），a 是每 kg 0.75 每天的基础代谢率，即；300 kJ/（kg 0.75 z d）（13-15）。由此可见，不同体型物种的基础代谢率与体重的0.75次方成正比，即所谓的代谢重。如果假设基础代谢率占总代谢率的75%，则总代谢率可以用函数Y 5 400 X 0.75 来描述。根据这一关系，70 公斤重的人的总代谢率为每公斤体重 400 3 70 0.75 5 9680 kJ 或 138 kJ。同样，30克小鼠的总代谢率为每公斤体重400 3 0.030 0.75 5 29 kJ或961 kJ。每公斤代谢重量的能量消耗相对增加 10%，也会导致每公斤体重的能量消耗增加 10%，但以千焦每公斤体重表示的能量消耗的绝对增加在小鼠中会比人类更大。因此，当以mg CLA每1000 kJ能量摄入量或mg CLA每公斤代谢重量表示的特定剂量的CLA[每1000 kJ能量摄入1 mg CLA 5 (400/1000) 5 0.4 mg CLA每公斤代谢重量]将导致小鼠和人类能量消耗类似的相对增加时，小鼠体内脂肪的减少也将比人类更大。例如，能量消耗增加10%，能量摄入不变，理论上会导致小鼠在30天期间减少0.10（能量消耗增加）3 961（每公斤体重的能量消耗，以kJ为单位）3 30（d）5 2883 kJ每公斤体重的能量，相当于每公斤体重2883/39.8 5 72.4克脂肪[体脂肪的总能量为每克39.8 kJ(16)]。同样，可以计算出，这10%的能量消耗增加，将导致人类每公斤体重减少414 kJ的能量，相当于每公斤体重减少10.4克脂肪。因此，理论计算表明，由于每公斤体重的代谢率高出七倍，因此小鼠体内脂肪的减少量将比人类高出约七倍。这些计算基于这样的假设：能量消耗的增加完全是以体脂肪为代价的，但这并不总是正确的（见表1的脚注2）。理论计算与小鼠和人类各种研究的实验数据一致。标准化结果表明，CLA 在人类中的降低体脂效果比在小鼠中低得多（表 1）。然而，针对小鼠和人类的各种研究的标准化结果存在很大差异。尽管如此，CLA 的标准化体脂降低效果在小鼠中平均比在人类中高出约七倍，这与理论计算的预测类似。表 1 中的结果似乎也支持上述假设，即特定剂量的 CLA 将导致小鼠和人类的能量消耗出现类似的相对增加。然而，尚不清楚这是否也适用于其他物种。因此，代谢率的差异可能在解释小鼠和人类之间 CLA 降脂作用的差异方面发挥着重要作用。应谨慎解释在小鼠中观察到的共轭亚油酸 (CLA) 对能量代谢的影响，并将其外推到人类也应谨慎。相比之下，与人类相比，小鼠的高代谢率可能使小鼠成为研究各种膳食脂肪和其他成分对能量代谢影响的绝佳模型。
(1‐ 6) and that this effect is mediated by an enhanced energy expenditure (5‐7). The body fat-lowering effect of CLA has also been reported in humans (8 ‐12), but it seems to be less prominent than in mice. The dose administered or the length of the feeding period may partly explain this difference in magnitude of the effect between mice and humans, but differences in metabolic rate may play a major role. The relationship between basal metabolic rate or energy expenditure and body weight in different size mammals is described by the function Y 5 aX 0.75 , where Y is basal metabolic rate (kJ/d), X is body weight (kg) and a is basal metabolic rate per kg 0.75 per day, which is ;300 kJ/ (kg 0.75 z d) (13‐15). Thus, the basal metabolic rate in different size species is proportional to the body weight raised to the 0.75 power, the so called metabolic weight. If one assumes that the basal metabolic rate comprises ;75% of the total metabolic rate, then the total metabolic rate can be described by the function Y 5 400 X 0.75 . From this relationship, it follows that the total metabolic rate of a 70-kg human is 400 3 70 0.75 5 9680 kJ or 138 kJ per kg body weight. Similarly, the total metabolic rate of a 30 g mouse is 400 3 0.030 0.75 5 29 kJ or 961 kJ per kg body weight. A relative increase of 10% in energy expenditure per kg metabolic weight will also result in a 10% increase in the energy expenditure per kg body weight but the absolute increase in energy expenditure expressed in kJ per kg body weight will be greater in mice than in humans. Consequently, the reduction in body fat will also be greater in mice than in humans when a particular dose of CLA expressed in mg CLA per 1000 kJ energy intake or in mg CLA per kg metabolic weight [1 mg CLA per 1000 kJ energy intake 5 (400/1000) 5 0.4 mg CLA per kg metabolic weight] will result in a similar relative increase in energy expenditure in both mice and humans. For example, an increase of 10% in energy expenditure and no change in energy intake will theoretically result in mice during a period of 30 d in a reduction of 0.10 (energy expenditure increase) 3 961 (energy expenditure in kJ per kg body weight) 3 30 (d) 5 2883 kJ energy per kg body weight, which is equivalent to 2883/39.8 5 72.4 g of fat per kg body weight [the gross energy of body fat is 39.8 kJ per g (16)]. Similarly, it can be calculated that this 10% increase in energy expenditure will result in humans in a reduction of 414 kJ of energy per kg body weight, which is equivalent to 10.4 g of fat per kg body weight. Thus, theoretical calculations indicate that the reduction in body fat will be about seven times higher in mice than in humans because of the seven times higher metabolic rate per kg body weight. These calculations are based on the assumption that the increase in energy expenditure is exclusively at the expense of body fat, which is not always true (see footnote 2 of Table 1). The theoretical calculations are in line with the experimental data from various studies in mice and humans. The normalized results indicate that the body fat-lowering effect of CLA is considerably lower in humans than in mice (Table 1). There are, however, large variations in the normalized results among the various studies in both mice and humans. Nevertheless, the normalized body fat-lowering effect of CLA is on average approximately seven times higher in mice than in humans, similar to what the theoretical calculations would predict. The results in Table 1 also seem to support the above assumption that a particular dose of CLA will result in a similar relative increase in energy expenditure in both mice and humans. However, it is not clear whether this might also be true for other species. Thus, differences in metabolic rate may play a major role in explaining the differences between mice and humans in the body fat-lowering effect of CLA. The effects of CLA on energy metabolism observed in mice should be cautiously interpreted and extrapolation to humans should be done carefully. In contrast, the high metabolic rate of the mouse compared with humans may make the mouse an excellent model to study the effects of various dietary fats and other components on energy metabolism.