Description of a local cardiac adiponectin system and its deregulation in dilated cardiomyopathy

AIMS: Despite recent advances in medical therapy, heart failure remains a leading cause for cardiovascular mortality, and its complex pathogenesis is incompletely understood. This study was performed to identify possible new therapeutic targets in dilated cardiomyopathy (DCM). METHODS AND RESULTS: Oligonucleotide microarray analysis was performed on endomyocardial biopsies (EMBs) from patients with early DCM (LVEDD > or = 55 mm, LVEF 60%, no cardiac pathology, n = 4). Adiponectin, an adipocytokine involved in cellular metabolism, survival, and immunmodulation, was six-fold downregulated in DCM patients. Microarray data for adiponectin were confirmed by TaqMan-PCR (9.2-fold downregulation, control n= 9 vs. DCM n= 9, respectively, P < 0.05). Immunohistological analysis of EMBs showed significant downregulation of cardiac adiponectin protein expression independent of serum adiponectin (P = 0.36, ns) or serum TNFalpha concentrations (P = 0.46, ns). Neither the adiponectin receptor 1 (adipo-R1) nor adipo-R2 was deregulated in early DCM. Adiponectin mRNA and protein downregulation were confirmed in explanted hearts of patients with advanced DCM (LVEF < 25%, n= 8). In vitro, adiponectin incubation of neonatal rat ventricular myocytes led to activation of the pro-survival kinase PKB/Akt, increased eNOS-phosphorylation, and prevented stress-induced apoptosis of cardiomyocytes in an Akt-dependent manner. Moreover, inhibition of adiponectin secretion was accompanied by an increase in the expression of the cytokine and its receptors. CONCLUSION: These data indicate the existence of a local cardiac adiponectin system regulated independent of adiponectin and TNFalpha serum levels and its disturbance in cardiac pathology. The study suggests a role for adiponectin in the pathogenesis of DCM and implicates the adipocytokine as a possible future therapeutic target in DCM.