Thomson A B, Schoeller C, Keelan M, Smith L, Clandinin M T
Department of Medicine, University of Alberta, Edmonton, Canada.
Can J Physiol Pharmacol. 1993 Aug;71(8):531-55. doi: 10.1139/y93-078.
Lipids are components of our diet and luminal secretions, with physicochemical characteristics that determine their digestion and absorption in the gastrointestinal tract. Lipids include triglycerides, phospholipids, and cholesterol. Dietary lipids contain approximately 97% triglycerides, with small amounts of phospholipids and cholesterol. These components are important in cell membrane composition, fluidity, peroxidation, prostaglandin and leukotriene synthesis, and cellular metabolic processes. Lipids are implicated in the mechanisms of brain development, inflammatory processes, atherosclerosis, carcinogenesis, aging, and cell renewal. Duodenal hydrolysis of dietary lipids and biliary phospholipids and cholesterol is carried out by pancreatic lipase, colipase, phospholipase A2, and cholesterol esterase. Bile acid solubilization results in mixed micelles and liposomes, in gel and liquid crystal phases. Lipid digestion products pass across the intestinal unstirred water layer. For long-chain fatty acids and cholesterol, passage across the unstirred water layer is rate limiting, whereas passage of short- and medium-chain fatty acids is limited by the brush-border membrane. Within the unstirred water layer, an acidic microclimate aids micellar dissociation so that protonated, and to a lesser extent, nonprotonated monomers then pass across the intestinal brush-border membrane. Absorptive mechanisms have been studied extensively in relation to lipid composition, fatty acid chain length, degree of unsaturation, essential fatty acid content, phospholipid components, and cholesterol. Enterocytes may take up lipids from the intestinal lumen or from lipoproteins of the bloodstream, but these pools are likely to be functionally distinct. Recent advances are reviewed, including recent advances in the area of microclimates, compartmentation, lipid binding proteins, intracellular trafficking, intestinal lipoproteins, release of lipids across the basolateral membrane, and dietary effects.
脂质是我们饮食和管腔分泌物的组成成分，其物理化学特性决定了它们在胃肠道中的消化和吸收。脂质包括甘油三酯、磷脂和胆固醇。膳食脂质约含97%的甘油三酯，还有少量的磷脂和胆固醇。这些成分在细胞膜组成、流动性、过氧化、前列腺素和白三烯合成以及细胞代谢过程中很重要。脂质与大脑发育、炎症过程、动脉粥样硬化、致癌作用、衰老和细胞更新机制有关。膳食脂质以及胆汁中的磷脂和胆固醇在十二指肠的水解是由胰脂肪酶、辅脂酶、磷脂酶A2和胆固醇酯酶进行的。胆汁酸的增溶作用会形成处于凝胶相和液晶相的混合微团和脂质体。脂质消化产物穿过肠道的未搅动水层。对于长链脂肪酸和胆固醇来说，穿过未搅动水层是限速步骤，而短链和中链脂肪酸的穿过则受刷状缘膜的限制。在未搅动水层内，酸性微环境有助于微团解离，这样质子化的单体以及程度较轻的非质子化单体随后穿过肠道刷状缘膜。关于脂质组成、脂肪酸链长度、不饱和度、必需脂肪酸含量、磷脂成分和胆固醇，人们已对吸收机制进行了广泛研究。肠上皮细胞可以从肠腔或血流中的脂蛋白摄取脂质，但这些库在功能上可能是不同的。本文综述了近期的进展，包括在微环境、区室化、脂质结合蛋白、细胞内运输、肠脂蛋白、脂质跨基底外侧膜的释放以及饮食影响等方面的最新进展。
