Green P H, Glickman R M, Riley J W, Quinet E
J Clin Invest. 1980 Apr;65(4):911-9. doi: 10.1172/JCI109745.
The role of the human intestine has been explored as a site of synthesis of apoA-IV, a major apoprotein of human intestinal triglyceride-rich lipoproteins. Intestinal biopsies were performed on normal volunteers while fasting and after lipid ingestion. Indirect immunofluorescence demonstrated a marked increase in immunofluorescence for apoA-IV during lipid absorption consistent with an increased intracellular content. ApoA-IV comprised 10-13% of chylomicron apoprotein and 24-30% of intestinal very low density lipoprotein (VLDL) as assessed by densitometry of sodium dodecyl sulfate gels of lipoproteins from chylous urine (mesenteric lymphatic-urinary fistula) and thoracic duct lymph (postoperative fistula). After one subject with chyluria ingested 40 g of corn oil, triglyceride excretion in urine was accompanied by an increased excretion of apoA-IV. 11.5 g of triglyceride and 81 mg of apoA-IV were recovered in the urine. In chylous urine 56% of apoA-IV was in the triglyceride-rich lipoproteins (chylomicrons and intestinal VLDL) and 44% in the d > 1.006-g/ml fraction. Normal plasma apoA-IV was 15.7+/-0.9 mg/dl (n = 14) whereas four subjects with abetalipoproteinemia had reduced levels 1.2, 7.6, 9.6, and 8.3 mg/dl, respectively. Lipid feeding in normal volunteers resulted in a rise in plasma apoA-IV (16.1+/-0.7 mg/dl to 18.5+/-0.7 mg/dl, n = 5, P < 0.01). In fasting plasma, 98% of apoA-IV was in the d > 1.21-g/ml fraction. In lipemic plasma, 10% of apoA-IV was associated with triglyceride-rich lipoproteins and 90% with the d > 1.21-g/ml fraction. Agarose column chromatography of fasting plasma confirmed that the bulk of plasma apoA-IV is free, unassociated with lipoproteins. These results demonstrate that apoA-IV is present in human intestinal epithelial cells and is secreted as a chylomicron and VLDL apoprotein. Within fasting plasma most of the apoA-IV is found free, unassociated with lipoproteins. After lipid ingestion apoA-IV is also found in plasma chylomicrons indicating that some apoA-IV remains associated with chylomicrons in plasma during chylomicron metabolism, although some may be transferred from the chylomicron surface.
人类肠道作为载脂蛋白A-IV（apoA-IV）的合成部位已被深入研究，apoA-IV是人类富含甘油三酯的肠道脂蛋白的主要载脂蛋白。对正常志愿者在空腹时以及摄入脂质后进行了肠道活检。间接免疫荧光显示，在脂质吸收过程中，apoA-IV的免疫荧光显著增加，这与细胞内含量增加一致。通过对来自乳糜尿（肠系膜淋巴管-尿道瘘）和胸导管淋巴（术后瘘）的脂蛋白进行十二烷基硫酸钠凝胶密度测定评估，apoA-IV占乳糜微粒载脂蛋白的10%-13%，占肠道极低密度脂蛋白（VLDL）的24%-30%。一名乳糜尿患者摄入40克玉米油后，尿中甘油三酯排泄增加的同时，apoA-IV的排泄也增加。尿中回收了11.5克甘油三酯和81毫克apoA-IV。在乳糜尿中，56%的apoA-IV存在于富含甘油三酯的脂蛋白（乳糜微粒和肠道VLDL）中，44%存在于密度大于1.006克/毫升的部分。正常血浆中apoA-IV为15.7±0.9毫克/分升（n = 14），而四名无β脂蛋白血症患者的水平分别降低至1.2、7.6、9.6和8.3毫克/分升。正常志愿者摄入脂质后，血浆apoA-IV升高（从16.1±0.7毫克/分升升至18.5±0.7毫克/分升，n = 5，P < 0.01）。在空腹血浆中，98%的apoA-IV存在于密度大于1.21克/毫升的部分。在脂血血浆中，10%的apoA-IV与富含甘油三酯的脂蛋白相关，90%与密度大于1.21克/毫升的部分相关。空腹血浆的琼脂糖柱层析证实，血浆中大部分apoA-IV是游离的，不与脂蛋白结合。这些结果表明，apoA-IV存在于人类肠道上皮细胞中，并作为乳糜微粒和VLDL载脂蛋白分泌。在空腹血浆中，大部分apoA-IV是游离的，不与脂蛋白结合。摄入脂质后，血浆乳糜微粒中也发现了apoA-IV，这表明在乳糜微粒代谢过程中，一些apoA-IV在血浆中仍与乳糜微粒结合，尽管有些可能从乳糜微粒表面转移。
