Yang L Y, Kuksis A, Myher J J
Banting and Best Department of Medical Research, University of Toronto, Ont., Canada.
Biochem Cell Biol. 1989 Apr-May;67(4-5):192-204. doi: 10.1139/o89-030.
Simple alkyl (ethyl) esters of polyunsaturated fish oil fatty acids have been proposed as dietary supplements, but their relative efficiency of digestion and absorption have not been determined. Using stomach tubes, we gave rats menhaden or rapeseed oils, or the corresponding methyl and ethyl esters, and determined by chromatographic methods the lipid classes and molecular species recovered from the lumen of the jejunum during the first 1 to 2.5 h of digestion. Hydrolysis of menhaden oil resulted in a preferential retention of a high proportion of the polyunsaturated long chain acids in the sn-2-monoacylglycerols and in the residual triacyglycerols, while digestion of rapeseed oil led to a preferential release of free long chain monounsaturated fatty acids. In contrast, hydrolysis of the alkyl (methyl and ethyl) esters of the fatty acids of either menhaden or rapeseed oil resulted in a composition of free fatty acids which was much more representative of the original esters. It was therefore concluded that the differential lumenal liberation of the long chain and polyunsaturated (three or more double bonds) fatty acids from fish and rapeseed oil is largely due to their characteristic distribution between the primary and secondary positions in the glycerol molecule, and to a much lesser extent to a chain length discrimination by pancreatic lipase. This study also shows that the methyl and ethyl esters are hydrolyzed about 4 times more slowly than the corresponding triacylglycerols, which is sufficient to maintain a saturated micellar solution of fatty acids in the intestinal lumen during absorption.
多不饱和鱼油脂肪酸的简单烷基（乙基）酯已被提议用作膳食补充剂，但其消化和吸收的相对效率尚未确定。我们通过胃管给大鼠喂食鲱鱼油或菜籽油，或相应的甲酯和乙酯，并采用色谱法测定在消化的最初1至2.5小时内从空肠腔中回收的脂质类别和分子种类。鲱鱼油的水解导致在sn-2-单酰甘油和残留三酰甘油中优先保留高比例的多不饱和长链酸，而菜籽油的消化则导致游离长链单不饱和脂肪酸的优先释放。相比之下，鲱鱼油或菜籽油脂肪酸的烷基（甲基和乙基）酯水解产生的游离脂肪酸组成更能代表原始酯。因此得出结论，鱼和菜籽油中长链和多不饱和（三个或更多双键）脂肪酸在肠腔中的差异释放主要是由于它们在甘油分子的一级和二级位置之间的特征分布，而在较小程度上是由于胰脂肪酶对链长的区分。这项研究还表明，甲酯和乙酯的水解速度比相应的三酰甘油慢约4倍，这足以在吸收过程中在肠腔中维持脂肪酸的饱和胶束溶液。
