Loss of Angiotensin-Converting Enzyme-2 Exacerbates Diabetic Cardiovascular Complications and Leads to Systolic and Vascular Dysfunction

Abstract

Rationale Diabetic cardiovascular complications are reaching epidemic proportions. Angiotensin-converting enzyme-2 (ACE2) is a negative regulator of the renin-angiotensin system. We hypothesize that loss of ACE2 exacerbates cardiovascular complications induced by diabetes. Objective To define the role of ACE2 in diabetic cardiovascular complications. Methods and Results We used the well-validated Akita mice, a model of human diabetes, and generated double-mutant mice using the ACE2 knockout (KO) mice (Akita/ACE2−/y). Diabetic state was associated with increased ACE2 in Akita mice, whereas additional loss of ACE2 in these mice leads to increased plasma and tissue angiotensin II levels, resulting in systolic dysfunction on a background of impaired diastolic function. Downregulation of SERCA2 and lipotoxicity were equivalent in Akita and Akita/ACE2KO hearts and are likely mediators of the diastolic dysfunction. However, greater activation of protein kinase C and loss of Akt and endothelial nitric oxide synthase phosphorylation occurred in the Akita/ACE2KO hearts. Systolic dysfunction in Akita/ACE2KO mice was linked to enhanced activation of NADPH oxidase and metalloproteinases, resulting in greater oxidative stress and degradation of the extracellular matrix. Impaired flow-mediated dilation in vivo correlated with increased vascular oxidative stress in Akita/ACE2KO mice. Treatment with the AT1 receptor blocker, irbesartan rescued the systolic dysfunction, normalized altered signaling pathways, flow-mediated dilation, and the increased oxidative stress in the cardiovascular system. Conclusions Loss of ACE2 disrupts the balance of the renin-angiotensin system in a diabetic state and leads to an angiotensin II/AT1 receptor-dependent systolic dysfunction and impaired vascular function. Our study demonstrates that ACE2 serves as a protective mechanism against diabetes-induced cardiovascular complications.

Angiotensin 1–7 mediates renoprotection against diabetic nephropathy by reducing oxidative stress, inflammation, and lipotoxicity

“…Picro-sirius red (PSR), dihydroethidium (DHE), ACE2, oil-O red, and hematoxylin and eosin (H&E) staining were performed as previously reported (31,35,50). Images for PSR, DHE, and ACE2 staining were captured by fluorescence microscopy and analyzed using MetaMorph software (Olympus IX81, Center Valley, PA).…”

“…Renal and urinary ACE2 activity was assessed using a fluorescent assay protocol as described previously (35,48). Briefly, 10 l of urine or 10 g total protein was added to the black microtiter plate containing assay buffer with 20 M 7-methoxycoumarin-YVADAPK-(2,4-dinitrophenyl)-OH (R&D Systems) as the fluorogenic substrate.…”

“…NADPH oxidase activity assay. We measured NADPH oxidase activity by using a lucigenin-enhanced chemiluminescence assay as reported previously (35,50).…”

“…These data suggest that ANG 1-7 induces renal ATGL expressions possibly via deacetylation of FOXO1 by SIRT1. We next determined renal ACE2 level in db/db mice since ACE2 is regulated by the SIRT1 pathway and in diabetic conditions (8,35). Immunofluorescence imaging showed increased ACE2 levels in renal cortical tubules in db/db mice, which was reversed by ANG 1-7 treatment (Fig.…”

Activation of the Cardiac Renin–Angiotensin System in High Oxygen-Exposed Newborn Rats

“…16 Ang II stimulation of ROS production in the heart also promotes calcium/calmodulin-dependent protein kinase II (CaMKII) oxidation and disruption of calcium (Ca 2+ ) homeostasis, a mechanism directly involved in the development of impaired myocardium contractility. [17][18][19] Further, alterations in the cardiac levels of angiotensin-converting enzyme 2 (ACE2), a counter-regulator of RAS activation in the heart, 20 may also be involved in the development of cardiac alterations induced by neonatal high O 2 exposure. Therefore, to better understand the participation of RAS on the developmental programming of cardiac dysfunction, the 2 aims in this study were (1) to determine whether RAS activation occurs during neonatal O 2 exposure and ≤28 days (P28) in rats and parallels the development of cardiac dysfunction and remodeling; and (2) to determine whether neonatal short-term treatment with an AT1 receptor blocker, losartan, in the last 3 days of neonatal O 2 exposure (from days 8 to day 10 of life) prevents cardiac alterations in young rats at P28.…”