Hudgins L C, Hellerstein M, Seidman C, Neese R, Diakun J, Hirsch J
Laboratory of Human Behavior and Metabolism, Rockefeller University, New York, NY 10021, USA.
J Clin Invest. 1996 May 1;97(9):2081-91. doi: 10.1172/JCI118645.
A new experimental approach was used to determine whether a eucaloric, low fat, high carbohydrate diet increases fatty acid synthesis. Normally volunteers consumed low fat liquid formula diets (10% of calories as fat and 75% as glucose polymers, n = 7) or high fat diets (40% of calories as fat and 45% as glucose polymers, n = 3) for 25 d. The fatty acid composition of each diet was matched to the composition of each subject's adipose tissue and compared with the composition of VLDL triglyceride. By day 10, VLDL triglyceride was markedly enriched in palmitate and deficient in linoleate in all subjects on the low fat diet. Newly synthesized fatty acids accounted for 44 +/- 10% of the VLDL triglyceride. Mass isotopomer distribution analysis of palmitate labeled with intravenously infused 13C-acetate confirmed that increased palmitate synthesis was the likely cause for the accumulation of triglyceride palmitate and "dilution" of linoleate. In contrast, there was minimal fatty acid synthesis on the high diet. Thus, the dietary substitution of carbohydrate for fat stimulated fatty acid synthesis and the plasma accumulation of palmitate-enriched, linoleate-deficient triglyceride. Such changes could have adverse effects on the cardiovascular system.
采用一种新的实验方法来确定等热量、低脂、高碳水化合物饮食是否会增加脂肪酸合成。正常情况下，志愿者食用低脂液体配方饮食（脂肪提供10%的热量，葡萄糖聚合物提供75%的热量，n = 7）或高脂饮食（脂肪提供40%的热量，葡萄糖聚合物提供45%的热量，n = 3），持续25天。每种饮食的脂肪酸组成与每个受试者脂肪组织的组成相匹配，并与极低密度脂蛋白甘油三酯的组成进行比较。到第10天，低脂饮食的所有受试者的极低密度脂蛋白甘油三酯中棕榈酸明显富集，亚油酸缺乏。新合成的脂肪酸占极低密度脂蛋白甘油三酯的44±10%。用静脉注射的13C-醋酸盐标记棕榈酸的质量同位素异构体分布分析证实，棕榈酸合成增加可能是棕榈酸甘油三酯积累和亚油酸“稀释”的原因。相比之下，高脂饮食时脂肪酸合成极少。因此，用碳水化合物替代脂肪的饮食刺激了脂肪酸合成以及富含棕榈酸、缺乏亚油酸的甘油三酯在血浆中的积累。这些变化可能会对心血管系统产生不利影响。
