Contents lists available at ScienceDirect Process Biochemistry journal homepage: www.elsevier.com/locate/procbio Gly-Val-Arg, an angiotensin-I-converting enzyme inhibitory tripeptide ameliorates hypertension on spontaneously hypertensive rats Sivananthan Manoharan a , Adawiyah Suriza Shuib a,b,c, ⁎ , Noorlidah Abdullah a,c , Ali Ashrafzadeh d , Nurul Kabir a a Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia b University of Malaya Centre for Proteomic Research, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia c Mushroom Research Centre, Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia d Medical Biotechnology Laboratory, Faculty of Medicine, University of Malaya, 50603 Kuala Lumpur, Malaysia ARTICLE INFO Keywords: Pleurotus pulmonarius Tripeptide GVR Antihypertensive activity Endothelium-dependent vasorelaxation Metabolomic Proteomic ABSTRACT The tripeptide GVR was previously shown to inhibit ACE and was able to reduce systolic blood pressure in SHRs within 6 h after administration. To further analyse the potential of tripeptide GVR in lowering blood pressure, a long term study was carried out where the tripeptide was orally administered to SHRs for 21 days. Elevated systolic blood pressure was significantly reduced when the peptide was administered at 50 mg/kg body weight and 100 mg/kg body weight. Body weight of the SHRs did not change significantly between the studied groups and the histopathological findings indicated that there were no abnormalities in liver and kidney tissues. From the acute toxicity analysis of this tripeptide, using the Up and Down method revealed that the peptide was non- toxic to SHRs. Tripeptide GVR demonstrated endothelium-dependent vasorelaxation activity using thoracic aortas from SD rats in which vasorelaxation was not observed in denuded aortas. The metabolomic analysis carried out from the sera of SHRs demonstrated changes on metabolites associated with pathways related to renin angiotensin system. As for proteomic analysis, differentially expressed proteins detected were mainly proteins related with inflammation. Based on the results, tripeptide GVR has a potential to ameliorate the ele- vated blood pressure in SHRs. 1. Introduction High blood pressure is acknowledged as a risk factor for morbidity and mortality associated with stroke, heart failure and coronary artery disease in addition to the development of chronic kidney disease. The average occurrence of overall high blood pressure in 2009 was 37.6% and 40.1% for men and women, respectively, in the United States [1]. In 2015, data from 195 countries and territories estimated 874 million adults had systolic blood pressure (SBP) of 140 mm Hg or greater and 3500 million adults had SBP of at least 110–115 mm Hg [2]. This number is expected to further increase rapidly in future worldwide [3]. The ACE inhibitors, calcium channel antagonists, beta and alpha blockers, natriuretic agents and endothelin receptor antagonists are groups of drugs which fall into the antihypertensive drug category. Despite their effectiveness, these drugs have undesirable side effects like coughing, taste disturbance, kidney problems and angioneurotic oedema [4]. Hydrochlorothiazide and chlorthalidone can lessen po- tassium, magnesium, phosphorus, sodium, chloride, folate, B6, zinc, iodine, and CoQ10 blood level while augmenting homocysteine, cal- cium, creatinine and glucose levels [5]. Furthermore, these drugs can lead to the development of insulin resistance and type-2 diabetes mel- litus at a rate of 5% annually [5]. Thus, there is still a need to discover new drugs for hypertension with less or no side effects. Since nutritional factors have been recognised to play a significant role in the prevention and/or treatment of hypertension, efforts are being made for the production of foods with antihypertensive activity [6]. Mushrooms have received increasing attention in recent years be- cause of their health-promoting properties and medicinal effects. Some edible mushrooms have been reported to significantly reduce blood pressure after oral administration [7,8]. Previously, we have reported tripeptide GVR derived from the mycelial protein of Pleurotus pulmo- narius with the ability to inhibit ACE in vitro and lower the blood pressure in spontaneously hypertensive rats (SHRs) in vivo [9]. To fur- ther analyse the possibility of using tripeptide GVR in lowering blood pressure without giving any adverse side effects, long term treatment of tripeptide GVR on SHRs was carried out in this study. The tripeptide https://doi.org/10.1016/j.procbio.2018.03.014 Received 4 November 2017; Received in revised form 16 March 2018; Accepted 17 March 2018 ⁎ Corresponding author at: Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur, 50603, Malaysia. E-mail address: adawiyah@um.edu.my (A.S. Shuib). Process Biochemistry xxx (xxxx) xxx–xxx 1359-5113/ © 2018 Elsevier Ltd. All rights reserved. Please cite this article as: Manoharan, S., Process Biochemistry (2018), https://doi.org/10.1016/j.procbio.2018.03.014