IGF-I alleviates diabetes-induced RhoA activation, eNOS uncoupling, and myocardial dysfunction.
IGF-I rescues diabetic heart defects and oxidative stress, although the underlying mechanism of action remains poorly understood. This study was designed to delineate the beneficial effects of IGF-I with a focus on RhoA, Akt, and eNOS coupling. Echocardiography was performed in normal or diabetic Friend Virus-B type (FVB) and IGF-I transgenic mice. Cardiomyocyte contractile properties were evaluated using peak shortening (PS), time-to-90% relengthening (TR90), and intracellular Ca2+ rise and decay. Diabetes reduced fraction shortening, PS, and intracellular Ca2+; it increased chamber size, prolonged TR90, and intracellular Ca2+ decay. Levels of RhoA mRNA, active RhoA, and O2(-) were elevated, whereas nitric oxide (NO) levels were reduced in diabetes. Diabetes-induced O2(-) accumulation was ablated by the NO synthase (NOS) inhibitor nitro-L-arginine methyl ester (L-NAME), indicating endothelial NOS (eNOS) uncoupling, all of which except heart size were negated by IGF-I. The IGF-I-elicited beneficial effects were mimicked by the Rho kinase inhibitor Y27632 and BH4. Diabetes depressed expression of Kv1.2 and dihydrofolate reductase (DHFR), increased beta-myosin heavy-chain expression, stimulated p38 MAPK, and reduced levels of total Akt and phosphorylated Akt/eNOS, all of which with the exception of myosin heavy chain were attenuated by IGF-I. In addition, Y27632 and the eNOS coupler folate abrogated glucose toxicity-induced PS decline, TR90 prolongation, while it increased O2(-) and decreased NO and Kv1.2 levels. The DHFR inhibitor methotrexate impaired myocyte function, NO/O2(-) balance, and rescued Y27632-induced cardiac protection. These results revealed that IGF-I benefits diabetic hearts via Rho inhibition and antagonism of diabetes-induced decrease in pAkt, eNOS uncoupling, and K+ channel expression.
Ren
Jun
J
School of Pharmacy, University of Wyoming, Laramie, WY 82071, USA. jren@uwyo.edu
Duan
Jinhong
J
Thomas
D Paul
DP
Yang
Xiaoping
X
Sreejayan
Nair
N
Sowers
James R
JR
Leri
Annarosa
A
Kajstura
Jan
J
Gao
Feng
F
Anversa
Piero
P
D000818:Animals; D001708:Biopterins / Q000031:analogs & derivatives / Q000378:metabolism; D009202:Cardiomyopathies / Q000000981:diagnostic imaging / Q000503:physiopathology*; D002469:Cell Separation; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D005493:Folic Acid Antagonists / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000235:genetics* / Q000502:physiology*; D051663:Kv1.2 Potassium Channel / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D051058:Oncogene Protein v-akt / Q000378:metabolism; D010084:Oxidation-Reduction; D010766:Phosphorylation; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism; D014463:Ultrasonography; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D054460:rho-Associated Kinases / Q000096:biosynthesis / Q000235:genetics; D020742:rhoA GTP-Binding Protein
D005493:Folic Acid Antagonists; D051663:Kv1.2 Potassium Channel; D001708:Biopterins; D007334:Insulin-Like Growth Factor I; D052250:Nitric Oxide Synthase Type III; D013762:Tetrahydrofolate Dehydrogenase; D051058:Oncogene Protein v-akt; D054460:rho-Associated Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D018995:Myosin Heavy Chains; C526380:RhoA protein, mouse; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; C003402:sapropterin