Carbonic anhydrase activation is associated with worsened pathological remodeling in human ischemic diabetic cardiomyopathy.

Background: Diabetes mellitus (DM) has multifactorial detrimental effects on myocardial tissue. Recently, carbonic anhydrases (CAs) have been shown to play a major role in diabetic microangiopathy but their role in the diabetic cardiomyopathy is still unknown.

Methods And Results: We obtained left ventricular samples from patients with DM type 2 (DM-T2) and nondiabetic (NDM) patients with postinfarct heart failure who were undergoing surgical coronary revascularization. Myocardial levels of CA-I and CA-II were 6- and 11-fold higher, respectively, in DM-T2 versus NDM patients. Elevated CA-I expression was mainly localized in the cardiac interstitium and endothelial cells. CA-I induced by high glucose levels hampers endothelial cell permeability and determines endothelial cell apoptosis in vitro. Accordingly, capillary density was significantly lower in the DM-T2 myocardial samples (mean±SE=2152±146 versus 4545±211/mm(2)). On the other hand, CA-II was mainly upregulated in cardiomyocytes. The latter was associated with sodium-hydrogen exchanger-1 hyperphosphorylation, exaggerated myocyte hypertrophy (cross-sectional area 565±34 versus 412±27 μm(2)), and apoptotic death (830±54 versus 470±34 per 10(6) myocytes) in DM-T2 versus NDM patients. CA-II is activated by high glucose levels and directly induces cardiomyocyte hypertrophy and death in vitro, which are prevented by sodium-hydrogen exchanger-1 inhibition. CA-II was shown to be a direct target for repression by microRNA-23b, which was downregulated in myocardial samples from DM-T2 patients. MicroRNA-23b is regulated by p38 mitogen-activated protein kinase, and it modulates high-glucose CA-II-dependent effects on cardiomyocyte survival in vitro.

Conclusions: Myocardial CA activation is significantly elevated in human diabetic ischemic cardiomyopathy. These data may open new avenues for targeted treatment of diabetic heart failure.