Fu Z, Attar-Bashi N M, Sinclair A J
Department of Food Science, RMIT University, Melbourne, Victoria, 3001, Australia.
Lipids. 2001 Mar;36(3):255-60. doi: 10.1007/s11745-001-0715-7.
A recent study on the metabolism of 1-14C-alpha-linolenic acid in the guinea pig revealed that the fur had the highest specific activity of all tissues examined, 48 h after dosing. The present study investigated the pattern of tissue lipid labeling following an oral dose of 1-14C-linoleic acid after the animals had been dosed for the same time as above. Guinea pigs were fed one of two diets with a constant linoleic acid content (18% total fatty acids) and a different content of alpha-linolenic acid (0.3 or 17.3%) from weaning for 3 wk and 1-14C-linoleic acid was given orally to each animal for 48 h prior to sacrifice. The most highly labeled tissues (dpm/mg of linoleic acid) were liver, followed by brain, lung and spleen, heart, kidney and adrenal and intestines, in both diet groups. The liver had almost a three-fold higher specific activity than skin and fur which was more extensively labeled than the adipose and carcass. Approximately two-thirds of the label in skin plus fur was found in the fur which, because of a low lipid mass, would indicate that the fur was highly labeled. All tissues derived from animals on the diet with the low alpha-linolenic acid level were significantly more labeled than the tissues from the animals on the high alpha-linolenic acid diet, by a factor of 1.5 to 3. The phospholipid fraction was the most highly labeled fraction in the liver, free fatty acids were the most labeled fraction in skin & fur, while triacyglycerols were the most labeled in the carcass and adipose tissue. In these tissues, more than 90% of the radioactivity was found in fatty acids with 2-double bonds in the tissue lipids. These data indicate that the majority of label found in guinea pig tissues 48 h after dosing was still associated with a fatty acid fraction with 2-double bonds, which suggests there was little metabolism of linoleic acid to more highly unsaturated fatty acids in this time frame. In this study, the labeling of guinea pig tissues with linoleic acid, 48 h after dosing, was quite different from the labeling with alpha-linolenic acid reported previously. The retention of the administered radioactivity from 14C-linoleic acid in the whole body lipids was 1.6 times higher in the group fed the low alpha-linolenic acid diet (diet contained a total of 1.8 g PUFA/100 g diet) compared with the group fed the high alpha-linolenic acid diet (diet contained 3.6 g PUFA/100 g diet). The lack of retention of 14C-labeled lipids in the whole body would be consistent with an increased rate of beta-oxidation of the labeled fatty acid on the diet rich in PUFA, a result supported by other studies using direct measurement of labeled carbon dioxide.
最近一项关于豚鼠体内1-14C-α-亚麻酸代谢的研究表明，给药48小时后，在所检测的所有组织中，皮毛的比活性最高。本研究在动物按照上述相同时间给药后，研究了口服1-14C-亚油酸后组织脂质标记的模式。从断奶开始，豚鼠被喂食两种亚油酸含量恒定（占总脂肪酸的18%）、α-亚麻酸含量不同（0.3%或17.3%）的饲料，为期3周，在处死前48小时给每只动物口服1-14C-亚油酸。在两个饲料组中，标记程度最高的组织（每毫克亚油酸的每分钟衰变数）是肝脏，其次是脑、肺和脾、心脏、肾脏、肾上腺和肠道。肝脏的比活性几乎比皮肤和皮毛高三倍，皮肤和皮毛的标记程度比脂肪和胴体更广泛。皮肤加皮毛中约三分之二的标记物存在于皮毛中，由于皮毛的脂质含量低，这表明皮毛的标记程度很高。与高α-亚麻酸饮食组的动物组织相比，低α-亚麻酸水平饮食组的动物所有组织的标记程度显著更高，高出1.5至3倍。磷脂部分是肝脏中标记程度最高的部分，游离脂肪酸是皮肤和皮毛中标记程度最高的部分，而三酰甘油是胴体和脂肪组织中标记程度最高的部分。在这些组织中，超过90%的放射性存在于组织脂质中具有两个双键的脂肪酸中。这些数据表明，给药48小时后在豚鼠组织中发现的大多数标记物仍与具有两个双键的脂肪酸部分相关，这表明在此时间范围内亚油酸向更高不饱和脂肪酸的代谢很少。在本研究中，给药48小时后豚鼠组织中亚油酸的标记情况与先前报道的α-亚麻酸的标记情况有很大不同。与高α-亚麻酸饮食组（饲料中含有3.6克多不饱和脂肪酸/100克饲料）相比，低α-亚麻酸饮食组（饲料中总共含有1.8克多不饱和脂肪酸/100克饲料）的动物全身脂质中14C-亚油酸的放射性保留率高1.6倍。全身缺乏14C标记脂质的保留情况与富含多不饱和脂肪酸的饲料中标记脂肪酸的β-氧化速率增加一致，其他使用直接测量标记二氧化碳的研究也支持这一结果。
