Roy D M, Schneeman B O
J Nutr. 1981 May;111(5):878-85. doi: 10.1093/jn/111.5.878.
Dietary vegetable proteins may lower plasma cholesterol compared to animal proteins. We considered the possibility that lower digestibility and the trypsin inhibitor (TI) content of plant proteins could lead to alterations in bile acid metabolism and exocrine pancreatic function mediating some of this change. Mice were fed cholesterolemic diets of different protein source and TI content: casein, soy protein isolate, or casein plus TI for 4 weeks. Plasma and liver cholesterol were measured; pancreata, intestinal contents and mucosal scrapes were collected for bile acid, trypsin, chymotrypsin, amylase, and lipase assays. The soy group had lower plasma cholesterol levels. Intestinal bile acids in this group were higher, suggesting a causal relationship (increased bile acid secretion leading to increased cholesterol catabolism). Conversely, liver cholesterol in this group was raised, reflecting a possible shift in body cholesterol pools. TI addition did not affect lipid metabolism, though it did affect pancreatic function: it led to increased pancreatic weight and depressed intestinal trypsin activity, but elevated chymotrypsin and amylase levels in pancreas and intestine and increased trypsin levels in the pancreas. Therefore, soybean TI does not seem to affect cholesterol metabolism, though it greatly affects pancreatic secretion. On the other hand, soy protein has a marked effect on the bile acid and cholesterol metabolism, which may be a function of protein quality.
与动物蛋白相比，膳食中的植物蛋白可能会降低血浆胆固醇水平。我们考虑到植物蛋白消化率较低以及含有胰蛋白酶抑制剂（TI）可能会导致胆汁酸代谢和外分泌胰腺功能发生改变，从而介导了这种变化的一部分。给小鼠喂食不同蛋白质来源和TI含量的致胆固醇血症饮食：酪蛋白、大豆分离蛋白或酪蛋白加TI，持续4周。测量血浆和肝脏胆固醇；收集胰腺、肠内容物和黏膜刮片用于胆汁酸、胰蛋白酶、糜蛋白酶、淀粉酶和脂肪酶检测。大豆组的血浆胆固醇水平较低。该组的肠道胆汁酸较高，提示存在因果关系（胆汁酸分泌增加导致胆固醇分解代谢增加）。相反，该组的肝脏胆固醇升高，反映了体内胆固醇池可能发生了变化。添加TI虽未影响脂质代谢，但确实影响了胰腺功能：它导致胰腺重量增加，肠道胰蛋白酶活性降低，但胰腺和肠道中的糜蛋白酶和淀粉酶水平升高，胰腺中的胰蛋白酶水平也升高。因此，大豆TI似乎不影响胆固醇代谢，尽管它对胰腺分泌有很大影响。另一方面，大豆蛋白对胆汁酸和胆固醇代谢有显著影响，这可能是蛋白质质量的作用。
