The Regulatory Roles of Peptide IRW on angiotensin-converting enzyme 2 (ACE2) in High-Fat Diet-Induced Mice and Spontaneously Hypertensive Rats
Creators: Ashkar, Fatemeh
Publisher: name: University of Alberta Library
Year: 2023

<p>Metabolic syndrome (MetS) refers to a cluster of various risk factors commonly associated with cardiovascular diseases (CVDs) and diabetes. Up-regulation of angiotensin-converting enzyme 2 (ACE2), a key member of the renin-angiotensin system (RAS), is generally protective against CVDs and diabetes. IRW, a tripeptide derived from ovotransferrin, was previously studied to reduce blood pressure in spontaneously hypertensive rats (SHRs) via a mechanism of up-regulation of ACE2 in artery. This peptide was also able to improve glucose intolerance in a high-fat diet (HFD)-induced insulin-resistant mouse model, but ACE2 was not affected in the skeletal muscle, the main tissue of glucose metabolism. <br>
Study #1 of the thesis was to investigate the regulatory role of the peptide IRW on aortic ACE2 and its associated signaling pathways in HFD-induced insulin-resistant mice.<br>
In the aorta of HFD mice treated with IRW (at a dose of 45 mg/kg body weight), ACE2 level was significantly increased, while the abundance of angiotensin II receptor (AT1R) and angiotensin-converting enzyme (ACE) was significantly reduced, in comparison to the HFD group. IRW supplementation also improved the abundance of glucose transporter 4 (GLUT4) and the expression of AMP-activated protein kinase (AMPK), Sirtuin 1 (SIRT1), and endothelial nitric oxide (eNOS) in IRW-treated mice. Moreover, IRW down-regulated the inflammatory pathways of endothelin-1 (ET-1) and p38 mitogen-activated protein kinases (P38 MAPK). ACE2 knockdown in vascular smooth muscle cells (VSMCs) reduced the levels of AMPK and eNOS. Our results indicate that the up-regulation of aortic ACE2 by the peptide IRW in HFD-induced insulin-resistant mice is responsible for activating pathways associated with vasodilation of blood vessels, potentially contributing to the improvement of insulin resistance and glucose metabolism.<br>
Study #2 was aimed to understand the regulatory role of peptide IRW on epithelial cadherin (E-cadherin), a transmembrane glycoprotein that enables specific cell-cell adhesion, and its interactions with ACE2. Our previous transcriptome analysis showed that gene expression of E-cadherin was significantly elevated in IRW-treated SHRs. Up-regulation of E-cadherin has been linked to reduced hyperplasia, anti-apoptotic, anti-migratory, and anti-epithelial-mesenchymal transition (EMT) effects in the vasculature. In SHRs, IRW treatment also increased the protein level of E-cadherin, while that of Zinc finger protein SNAI1 (Snail1) was decreased. Similar trend was also observed in VSMCs. Treatment with IRW led to a notable reduction in Orai Calcium Release-Activated Calcium Modulator 1 (Orai1) levels in cells, although no significant change was observed in SHRs. In VSMCs, both angiotensin II (Ang II) stimulation and ACE2 knockdown resulted in a significant decrease in E-cadherin levels. The expression of E-cadherin was significantly increased when VSMCs were treated with either Tamoxifen or IRW. Tamoxifen is commonly utilized for the treatment of breast cancer due to its ability to activate the E-cadherin, thereby causing an increase in the expression of E-cadherin mRNA and protein levels. <br>
Taken together, our studies supported that peptide IRW up-regulates ACE2 in artery to exert its beneficial signaling pathways in both animal models.</p>