Elucidation of antihypertensive mechanism of small peptides and new proposal of physiological functional foods

本研究主要通过大鼠实验和细胞实验来阐明生物活性小肽的降压机制。典型的新发现如下：1.具有抗高血压作用的二肽瓦尔-Tyr（VY）具有年龄依赖性的降压作用;单次口服10 mg/kg VY后，18周龄SHR的血压明显降低，而24周龄SHR的血压降低较少。2. 18周龄SHR的肽吸收研究结果表明，在循环血液系统以及局部器官系统中观察到完整的VY吸收，特别是在肾和腹主动脉中，肽主要以ng/g-组织水平积累。因此，VY在体内的吸收主要集中在局部器官，而不是血液系统。3.为了明确ACE肽是否具有缓激肽增强作用，本研究探讨了ACE肽结构与其C/N结构域阻断的相关性。在65个合成肽中，仅Ile-Tyr和Ile-Phe-Tyr观察到显著的N-结构域ACE抑制。肽的疏水能的知识提供了有用的信息，即具有10.8至12.5kJ/mol的限制能的肽或化合物可以抑制N-结构域ACE活性。4.以人血管平滑肌细胞（VSMC）为模型，研究了具有ACE抑制活性的小肽的潜在生理功能。结果表明，VY能显著抑制VSMC的生长，抑制率为对照组的59.5%.此外，在测试的ACE抑制肽中，仅观察到VY抑制1 μM Ang II刺激的WST-8掺入增加。AT_1受体拮抗剂（1 μM losartan）对VY的抑制作用无影响。最后，VY抑制Bay K 8644刺激的VSMC增殖，表明具有ACE抑制活性的VY也作为L-型Ca ~（2+）通道阻断剂。

This study has focused on the elucidation of antihypertensive mechanism of bioactive small peptides on rat and cell-line experiments. Typical and new findings are as follows:1.Di-peptide, Val-Tyr(VY) with antihypertensive ability in mild hypertensive human showed an age-dependent blood pressure lowering ; a prominent lowering effect was observed in 18-wk SHR after a single oral administration of 10 mg/kg VY, whereas less effect was obtained in 24-wk SHR.2.As a result of peptide absorption study in 18-wk SHR, intact VY absorption was observed in the circulating blood system as well as local organ systems, in particular in the kidney and abdominal aorta the peptide was predominantly accumulated at ng/g-tissue level. Thus, it was found that VY absorbed preferably into local organs rather than blood system.3.To clarify whether ACE inhibitoty peptides act as a bradykinin potentiator or not, correlation between peptide structure and C-/N-domain blockade of ACE was investigated. Among 65 synthetic peptides, a significant N-domain ACE inhibition was observed only for Ile-Tyr and Ile-Phe-Tyr. Knowledge on hydrophobic energy of peptides provided a useful information that peptides or compounds having the restrictive energy of 10.8 to 12.5 kJ/mol could inhibit N-domain ACE activity..4.A potential physiological function of small peptides having ACE inhibitory activity was examined using human vascular smooth muscle cell (VSMC). As a result, VYsignificantly inhibited VSMC growth with a reduction to 59.5 % of control. In addition, inhibition of increase in 1 μM Ang II-stimulated WST-8 incorporation was observed only for VY among tested ACE inhibitory peptides. The VY-induced inhibition was not affected in the presence of AT_1 receptor antagonist (1 μM of losartan) at all. Finally, VY inhibited a Bay K 8644-stimulated VSMC proliferation, indicating that VY with ACE inhibitory activity also acts as an L-type Ca2+ channel blocker.