Angiotensin type 1a receptor-deficient mice develop diabetes-induced cardiac dysfunction, which is prevented by renin-angiotensin system inhibitors.
BACKGROUND
Diabetes-induced organ damage is significantly associated with the activation of the renin-angiotensin system (RAS). Recently, several studies have demonstrated a change in the RAS from an extracellular to an intracellular system, in several cell types, in response to high ambient glucose levels. In cardiac myocytes, intracellular angiotensin (ANG) II synthesis and actions are ACE and AT1 independent, respectively. However, a role of this system in diabetes-induced organ damage is not clear.


METHODS
To determine a role of the intracellular ANG II in diabetic cardiomyopathy, we induced diabetes using streptozotocin in AT1a receptor deficient (AT1a-KO) mice to exclude any effects of extracellular ANG II. Further, diabetic animals were treated with a renin inhibitor aliskiren, an ACE inhibitor benazeprilat, and an AT1 receptor blocker valsartan.


RESULTS
AT1a-KO mice developed significant diastolic and systolic dysfunction following 10 wks of diabetes, as determined by echocardiography. All three drugs prevented the development of cardiac dysfunction in these animals, without affecting blood pressure or glucose levels. A significant down regulation of components of the kallikrein-kinin system (KKS) was observed in diabetic animals, which was largely prevented by benazeprilat and valsartan, while aliskiren normalized kininogen expression.


CONCLUSIONS
These data indicated that the AT1a receptor, thus extracellular ANG II, are not required for the development of diabetic cardiomyopathy. The KKS might contribute to the beneficial effects of benazeprilat and valsartan in diabetic cardiomyopathy. A role of intracellular ANG II is suggested by the inhibitory effects of aliskiren, which needs confirmation in future studies.
Qian Chen
QC
Yong
Candice M
CM
Thomas
Rachid
R
Seqqat
Niketa
N
Chandel
Kenneth M
KM
Baker
Division of Molecular Cardiology, Department of Medicine, Texas A&M Health Science Center, College of Medicine; Scott & White; Central Texas Veterans Health Care System, 1901 South First Street, Building 205, Temple, Texas 76504, USA. kumar@medicine.tamhsc.edu.
Rajesh
R
Kumar
D000577:Amides / Q000494:pharmacology; D000804:Angiotensin II / Q000502:physiology*; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D002478:Cells, Cultured; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D058065:Diabetic Cardiomyopathies / Q000000981:diagnostic imaging / Q000235:genetics* / Q000378:metabolism; D004195:Disease Models, Animal; D015536:Down-Regulation; D005650:Fumarates / Q000494:pharmacology; D007610:Kallikreins / Q000235:genetics / Q000378:metabolism; D007704:Kininogens / Q000235:genetics / Q000378:metabolism; D007705:Kinins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D032383:Myocytes, Cardiac / Q000378:metabolism*; D044140:Receptor, Angiotensin, Type 1 / Q000235:genetics* / Q000502:physiology; D012084:Renin-Angiotensin System / Q000502:physiology; D013777:Tetrazoles / Q000494:pharmacology; D014463:Ultrasonography; D014633:Valine / Q000031:analogs & derivatives / Q000494:pharmacology; D000068756:Valsartan; D000092502:Renin Inhibitors
D000577:Amides; D000804:Angiotensin II; D047228:Angiotensin II Type 1 Receptor Blockers; D000806:Angiotensin-Converting Enzyme Inhibitors; D001552:Benzazepines; D005650:Fumarates; D007610:Kallikreins; D007704:Kininogens; D007705:Kinins; D044140:Receptor, Angiotensin, Type 1; D013777:Tetrazoles; D014633:Valine; D000068756:Valsartan; D000092502:Renin Inhibitors; C544066:Agtr1a protein, mouse; C446481:aliskiren; C052133:benazeprilat