Hill J O, Peters J C, Swift L L, Yang D, Sharp T, Abumrad N, Greene H L
Department of Pediatrics, Vanderbilt University, Nashville, TN.
J Lipid Res. 1990 Mar;31(3):407-16.
Although medium chain triglyceride (MCT) is less calorically dense than long chain triglyceride (LCT), it produces a greater thermic effect following ingestion. We hypothesized that the previously observed high rate of thermogenesis produced by MCT overfeeding was due to hepatic de novo synthesis of long chain fatty acids (LCFA) from the excess medium chain fatty acids (MCFA). To study this, we compared the effects of overfeeding MCT- and LCT-containing diets on blood lipid profiles. Ten in-patient, nonobese males were overfed (150% of estimated energy requirements) two formula diets for 6 days each, in a randomized crossover design. Diets differed only in the composition of the fat and contained either 40% of energy as MCT or LCT (soybean oil). The major differences between diets in the resulting pattern of blood lipids were: 1) a reduction in fasting serum total cholesterol concentrations with the LCT, but not the MCT diet; and 2) a threefold increase in fasting serum triglyceride concentrations with MCT, but not LCT, diet. Moreover, 10% of the fasting triglyceride fatty acids were medium chain and 40% were 16:0 with the MCT diet. This compared to 1% and 20% for medium chain and 16:0, respectively, with the LCT diet. In addition, there were increases in 16:1, 18:0, and 18:1 in the triglycerides during MCT feeding. The changes in fatty acids in triglycerides with MCT feeding are consistent with the hypothesis that excess dietary MCT cause a significant increase in the hepatic synthesis of these fatty acids from MCFA through de novo synthesis and/or chain elongation and desaturation. These processes could account for the higher rate of postprandial thermogenesis with MCT as compared to LCT.
尽管中链甘油三酯（MCT）的热量密度低于长链甘油三酯（LCT），但摄入后它会产生更大的热效应。我们推测，之前观察到的MCT过量喂养产生的高热生成率是由于肝脏从过量的中链脂肪酸（MCFA）中重新合成了长链脂肪酸（LCFA）。为了研究这一点，我们比较了过量喂养含MCT和LCT饮食对血脂谱的影响。采用随机交叉设计，10名住院的非肥胖男性分别过量喂养两种配方饮食6天（估计能量需求的150%）。饮食仅在脂肪组成上有所不同，分别含有40%能量的MCT或LCT（大豆油）。两种饮食在血脂结果模式上的主要差异为：1）LCT饮食可降低空腹血清总胆固醇浓度，而MCT饮食则不能；2）MCT饮食可使空腹血清甘油三酯浓度增加三倍，而LCT饮食则不能。此外，MCT饮食时，空腹甘油三酯脂肪酸中有10%是中链的，40%是16:0。相比之下，LCT饮食时中链和16:0分别为1%和20%。另外，MCT喂养期间甘油三酯中的16:1、18:0和18:1也有所增加。MCT喂养时甘油三酯中脂肪酸的变化与以下假设一致，即过量的膳食MCT通过从头合成和/或链延长及去饱和作用，导致肝脏从MCFA合成这些脂肪酸的量显著增加。这些过程可以解释与LCT相比，MCT餐后产热率更高的原因。
