Lack of osteopontin improves cardiac function in streptozotocin-induced diabetic mice.
The purpose of this study was to investigate the role of osteopontin (OPN) in diabetic hearts. Diabetes was induced in wild-type (WT) and OPN knockout (KO) mice by using streptozotocin (150 mg/kg) injection. Left ventricular (LV) structural and functional remodeling was studied 30 and 60 days after induction of diabetes. Induction of diabetes increased OPN expression in cardiac myocytes. Heart weight-to-body weight ratio was increased in both diabetic (D) groups. Lung wet weight-to-dry weight ratio was increased only in the WT-D group. Peak left ventricular (LV) developed pressures measured using Langendorff perfusion analyses were reduced to a greater extent in WT-D versus KO-D group. LV end-diastolic pressure-volume curve exhibited a significant leftward shift in WT-D but not in KO-D group. LV end-diastolic diameter, percent fractional shortening, and the ratio of peak velocity of early and late filling (E/A wave) were significantly reduced in WT-D mice as analyzed by echocardiography. The increase in cardiac myocyte apoptosis and fibrosis was significantly higher in the WT-D group. Expression of atrial natriuretic peptide and transforming growth factor-beta1 was significantly increased in the WT-D group. Induction of diabetes increased protein kinase C (PKC) phosphorylation in both groups. However, phosphorylation of PKC-betaII was significantly higher in the WT-D group, whereas phosphorylation of PKC-zeta was significantly higher in the KO-D group. Levels of peroxisome proliferator-activated receptor-gamma were significantly decreased in the WT-D group but not in the KO-D group. Thus increased expression of OPN may play a deleterious role during streptozotocin-induced diabetic cardiomyopathy with effects on cardiac fibrosis, hypertrophy, and myocyte apoptosis.
Subramanian
Venkateswaran
V
Dept. of Physiology, James H. Quillen College of Medicine, East Tennessee State Univ., PO Box 70576, Johnson City, TN 37614, USA. singhm@etsu.edu
Krishnamurthy
Prasanna
P
Singh
Krishna
K
Singh
Mahipal
M
D000818:Animals; D009202:Cardiomyopathies / Q000209:etiology* / Q000503:physiopathology*; D003921:Diabetes Mellitus, Experimental / Q000139:chemically induced / Q000150:complications* / Q000503:physiopathology*; D051379:Mice; D018345:Mice, Knockout; D013311:Streptozocin; D018487:Ventricular Dysfunction, Left / Q000209:etiology* / Q000503:physiopathology*
D013311:Streptozocin