Adiponectin is the most abundant plasma adipokine, and is well known for its role in\nenergy homeostasis and cardiac protection. In humans with dilated cardiomyopathy, myocardial\nadiponectin protein expression is reduced compared to normal hearts and has been implicated\nin the pathology of cardiomyopathy. Serum adiponectin levels are often conflicting, with higher\nlevels associated with poor survival in humans with congestive heart failure (CHF).We evaluated\nadiponectin serum concentrations and myocardial protein expression in dogs with naturally occurring\nmyxomatous mitral valve disease and CHF. We compared the findings to active and hibernating\nbrown bears as bears are adapted to endure an extreme period of low cardiac output during their\nannual hibernation. Bears exhibited largely the active high-molecular weight (HMW) versus the\nlow-molecular weight isoforms of myocardial adiponectin (HMW:LMW = 6.3) during both the active\nperiod and hibernation, while healthy dogs exhibited a more balanced mix of isoforms. Dogs with\nCHF expressed predominately HMW isoforms of adiponectin (HMW:LMW = 12.5), appearing more\nsimilar to bears. In contrast to humans, serum adiponectin was significantly lower in dogs with\nCHF and lowest levels in the severest CHF class. In both dogs and bears, myocardial adiponectin\nwas expressed independent of circulating adiponectin concentrations, suggesting a local regulatory\nmechanism within the heart.
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