Background
Peptides derived from brewer’s spent grain (BSG) and yeast (BSY) are promising natural substitutes of synthetic drugs to manage hypertension as inhibitors of angiotensin-converting enzyme (ACE). However, their impact on the vascular function, so far, remains to be verified. Accordingly, we aimed to evaluate the effect of brewing peptides on the arterial vasocontractile response to angiotensin (Ang) I (through vascular ACE-inhibition) to estimate their antihypertensive potential. The impact of the oral route (gastrointestinal digestion, intestinal absorption, and liver metabolism) in brewing peptides was also investigated.
Methods
Iliac arteries from adult spontaneously hypertensive rats were studied with isometric tension recording. After ensuring the function integrity of the arteries, concentration-response curves to addition of Ang I (10−9-10−6 M) were performed after 30 min incubation with MIX (50:50 mixture of BSG:BSY) or BSG (0.86 mg/mL), or captopril (an ACE-inhibitory drug) or Krebs solution.
Results
MIX peptides (without simulated oral administration) enhanced Ang I-induced vasoconstriction, but lacked vascular effects after simulated oral administration. By contrast, BSG peptides (without simulated oral administration) did not exhibit vascular effects, whereas they promoted a marked decrease in vasocontraction evoked by the generated Ang II after simulation of the oral route, implying their capability to inhibit ACE. Additionally, to elucidate this inhibitory mechanism, Michaelis-Menten and Lineweaver-Burk plots indicated a mixed inhibition type.
Conclusion
With simulation of the oral route, BSG peptides were able to inhibit vascular ACE with a similar efficacy as the antihypertensive drug captopril, suggesting the potential to mitigate the burden of hypertension.
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