Ochi H, Tazuma S, Kajiyama G
First Department of Internal Medicine, Hiroshima University School of Medicine, Japan.
Biochem J. 1996 Aug 15;318 ( Pt 1)(Pt 1):139-44. doi: 10.1042/bj3180139.
The present study was performed to determine whether the degree of lecithin hydrophobicity regulates bile metastability and, therefore, affects the process of cholesterol crystallization. Supersaturated model bile (MB) solutions were prepared with an identical composition on a molar basis (taurocholate/lecithin/cholesterol, 73:19.5:7.5; total lipid concentration 9 g/dl) except for the lecithin species; egg yolk phosphatidylcholine, soybean phosphatidylcholine, 1-palmitoyl-2-linoleoyl-sn-phosphatidylcholine, dilinoleoyl phosphatidylcholine and dipalmitoyl phosphatidylcholine. Each MB solution was incubated and sequentially examined. Video-enhanced contrast microscopy demonstrated that the rate of vesicular aggregation and fusion correlated with the degree of lecithin hydrophobicity, and that the rate of cholesterol crystal nucleation correlated with the degree of lecithin hydrophilicity. In MBs containing less hydrophobic lecithin, needle-like crystals developed and transformed into mature plate-like crystals, whereas classical plate-like crystals were consistently observed in MBs composed of hydrophobic lecithin. Laser-diffraction particle size analysis demonstrated that the increase in lecithin hydrophobicity enlarged the vesicle dimension, enhancing its cholesterol-holding capacity. Correlation between vesicular cholesterol packing density and lecithin hydrophobicity suggests that the process of bile cholesterol nucleation and growth is regulated, in part, by acyl chain unsaturation in lecithin. Since the composition of biliary lecithins is responsive to dietary manipulations, this study provides new insights into the prevention of cholesterol gallstones.
本研究旨在确定卵磷脂疏水性程度是否调节胆汁亚稳定性，从而影响胆固醇结晶过程。除卵磷脂种类不同外，制备了等摩尔组成相同的过饱和模型胆汁（MB）溶液（牛磺胆酸盐/卵磷脂/胆固醇，73:19.5:7.5；总脂质浓度9 g/dl）；蛋黄磷脂酰胆碱、大豆磷脂酰胆碱、1-棕榈酰-2-亚油酰-sn-磷脂酰胆碱、二亚油酰磷脂酰胆碱和二棕榈酰磷脂酰胆碱。对每种MB溶液进行孵育并依次检查。视频增强对比显微镜显示，囊泡聚集和融合速率与卵磷脂疏水性程度相关，胆固醇晶体成核速率与卵磷脂亲水性程度相关。在含有疏水性较低卵磷脂的MB中，针状晶体形成并转变为成熟的板状晶体，而在由疏水性卵磷脂组成的MB中始终观察到经典的板状晶体。激光衍射粒度分析表明，卵磷脂疏水性增加会扩大囊泡尺寸，增强其胆固醇容纳能力。囊泡胆固醇堆积密度与卵磷脂疏水性之间的相关性表明，胆汁胆固醇成核和生长过程部分受卵磷脂中酰基链不饱和度的调节。由于胆汁卵磷脂的组成对饮食操作有反应，本研究为预防胆固醇胆结石提供了新的见解。
