Institute of Agricultural and Nutritional Sciences, Martin Luther University Halle-Wittenberg, Von-Danckelmann-Platz 2, 06120 Halle (Saale), Germany.
Nutr Metab (Lond). 2014 Feb 3;11(1):9. doi: 10.1186/1743-7075-11-9.
Lupin proteins exert hypocholesterolemic effects in man and animals, although the underlying mechanism remains uncertain. Herein we investigated whether lupin proteins compared to casein modulate sterol excretion and mRNA expression of intestinal sterol transporters by use of pigs as an animal model with similar lipid metabolism as humans, and cellular cholesterol-uptake by Caco-2 cells.
Two groups of pigs were fed cholesterol-containing diets with either 230 g/kg of lupin protein isolate from L. angustifolius or 230 g/kg casein, for 4 weeks. Faeces were collected quantitatively over a 5 d period for analysis of neutral sterols and bile acids by gas chromatographically methods. The mRNA abundances of intestinal lipid transporters were analysed by real-time RT-PCR. Cholesterol-uptake studies were performed with Caco-2 cells that were incubated with lupin conglutin γ, phytate, ezetimibe or albumin in the presence of labelled [4-14C]-cholesterol.
Pigs fed the lupin protein isolate revealed lower cholesterol concentrations in total plasma, LDL and HDL than pigs fed casein (P < 0.05). Analysis of faeces revealed a higher output of cholesterol in pigs that were fed lupin protein isolate compared to pigs that received casein (+57.1%; P < 0.05). Relative mRNA concentrations of intestinal sterol transporters involved in cholesterol absorption (Niemann-Pick C1-like 1, scavenger receptor class B, type 1) were lower in pigs fed lupin protein isolate than in those who received casein (P < 0.05). In vitro data showed that phytate was capable of reducing the uptake of labelled [4-14C]-cholesterol into the Caco-2 cells to the same extend as ezetimibe when compared to control (-20.5% vs. -21.1%; P < 0.05).
Data reveal that the cholesterol-lowering effect of lupin protein isolate is attributable to an increased faecal output of cholesterol and a reduced intestinal uptake of cholesterol. The findings indicate phytate as a possible biofunctional ingredient of lupin protein isolate.
羽扇豆蛋白在人和动物中具有降低胆固醇的作用，但其潜在机制尚不清楚。在此，我们使用与人类脂质代谢相似的动物模型猪，研究了羽扇豆蛋白与酪蛋白相比是否通过调节固醇排泄和肠道固醇转运体的 mRNA 表达来调节固醇排泄，并通过 Caco-2 细胞研究细胞胆固醇摄取。
两组猪分别用含有 230g/kg 羽扇豆蛋白（来自 L. angustifolius）或 230g/kg 酪蛋白的含胆固醇饮食喂养 4 周。在 5 天的时间内定量收集粪便，通过气相色谱法分析中性固醇和胆汁酸。通过实时 RT-PCR 分析肠道脂质转运体的 mRNA 丰度。用 Caco-2 细胞进行胆固醇摄取研究，在存在标记的 [4-14C]-胆固醇的情况下，用羽扇豆球蛋白 γ、植酸、依泽替米贝或白蛋白孵育 Caco-2 细胞。
与喂食酪蛋白的猪相比，喂食羽扇豆蛋白分离物的猪总血浆、LDL 和 HDL 中的胆固醇浓度更低（P<0.05）。粪便分析显示，喂食羽扇豆蛋白分离物的猪的胆固醇排泄量高于喂食酪蛋白的猪（+57.1%；P<0.05）。参与胆固醇吸收的肠道固醇转运体（尼曼-匹克 C1 样 1、清道夫受体 B 型，1 型）的相对 mRNA 浓度在喂食羽扇豆蛋白分离物的猪中低于喂食酪蛋白的猪（P<0.05）。体外数据显示，与对照相比，植酸能够将标记的 [4-14C]-胆固醇摄取到 Caco-2 细胞中的量减少到与依泽替米贝相同的程度（-20.5% vs. -21.1%；P<0.05）。
数据表明，羽扇豆蛋白分离物的降胆固醇作用归因于胆固醇粪便排泄量增加和肠道胆固醇摄取减少。研究结果表明植酸可能是羽扇豆蛋白分离物的一种生物功能性成分。
