Redgrave T G, Kodali D R, Small D M
Department of Medicine, Housman Medical Research Center, Boston University School of Medicine, Massachusetts 02118.
J Biol Chem. 1988 Apr 15;263(11):5118-23.
A systematic study was undertaken to observe the effects of dietary (dioleoyl) triacyl-sn-glycerol structure on chylomicron composition and metabolism. First studied was a series of 1,2-dioleoyl-3-(saturated)acyl-sn-glycerols, where the fatty acid esterified at the 3-position was varied from 14 to 24 carbons. Next a series of 1,3-dioleoyl-2-acyl glycerols was studied, with various fatty acids esterified at the glycerol 2-position. These stereospecific triacyl-sn-glycerols were fed to donor rats and lymph chylomicrons were isolated, analyzed, and reinjected into recipient rats to study their disappearance from plasma and delivery to tissues. As shown by their compositions, chylomicrons obtained after feeding triacylglycerols containing all sn-3 fatty acid of chain length greater than 20 carbons were under-represented, possibly due to poorer digestion by lipases, or poorer absorption by the intestine. The 18-carbon saturated chain fatty acid (stearic acid) was equally well represented in chylomicrons whether in the 2- or 3-position of the fed triacylglycerol. The presence of increased amounts of long-chain saturated fatty acids in donor chylomicron triacylglycerols affected the metabolism of chylomicrons injected into the bloodstream of recipient rats. In particular the rate of removal of labeled cholesteryl esters, tracing removal of the partially degraded chylomicron remnants was slowed by the saturated chains, with palmitic acid and the 20-carbon fatty acid, arachidic acid, showing the most severe effects. There were clear differences in the removal from plasma of injected lymph chylomicrons derived from fed triacylglycerols containing stearic acid in either the 2- or 3-position, with evidence for remnants from the symmetrical triacylglycerols being less rapidly removed from the circulating blood. This effect was investigated further by injected model emulsions of chylomicrons, where the 2-position was substituted with saturated or transunsaturated acyl chains. Quantitation of removal from the blood stream of these model lipoproteins confirmed that a saturated or transunsaturated long chain fatty acid at the 2-position of the emulsion triacylglycerols slowed remnant removal from the blood. In some cases, with both lymph chylomicron and with emulsions, the lipolytic step mediated by lipoprotein lipase was also slowed.
开展了一项系统性研究，以观察膳食（二油酰基）三酰基 - sn - 甘油结构对乳糜微粒组成和代谢的影响。首先研究了一系列1,2 - 二油酰基 - 3 - （饱和）酰基 - sn - 甘油，其中在3位酯化的脂肪酸碳链长度从14到24个碳不等。接下来研究了一系列1,3 - 二油酰基 - 2 - 酰基甘油，甘油2位酯化有各种脂肪酸。将这些立体特异性三酰基 - sn - 甘油喂给供体大鼠，分离、分析淋巴乳糜微粒，并将其重新注入受体大鼠以研究它们从血浆中的消失情况以及向组织的递送情况。从其组成来看，喂食含有链长大于20个碳的所有sn - 3脂肪酸的三酰甘油后获得的乳糜微粒含量不足，这可能是由于脂肪酶消化较差或肠道吸收较差所致。无论喂食的三酰甘油中18碳饱和链脂肪酸（硬脂酸）在2位还是3位，其在乳糜微粒中的含量都同样良好。供体乳糜微粒三酰甘油中长链饱和脂肪酸含量增加会影响注入受体大鼠血流中的乳糜微粒的代谢。特别是，标记胆固醇酯的去除速率（追踪部分降解的乳糜微粒残余物的去除情况）因饱和链而减慢，棕榈酸和20碳脂肪酸花生酸的影响最为严重。源自喂食的三酰甘油中硬脂酸在2位或3位的注入淋巴乳糜微粒从血浆中的去除存在明显差异，有证据表明对称三酰甘油的残余物从循环血液中的去除速度较慢。通过注入乳糜微粒的模型乳剂进一步研究了这种效应，其中2位被饱和或反式不饱和酰基链取代。对这些模型脂蛋白从血流中去除情况的定量分析证实，乳剂三酰甘油2位的饱和或反式不饱和长链脂肪酸会减慢残余物从血液中的去除。在某些情况下（无论是淋巴乳糜微粒还是乳剂），脂蛋白脂肪酶介导的脂解步骤也会减慢。
