Reduced-energy diet improves survival of obese KKAy mice with viral myocarditis: Induction of cardiac adiponectin expression

Obesity is an important risk factor for heart disease. Whether weight loss affects the severity of heart failure induced by viral myocarditis is a matter of debate. We hypothesized that weight loss could improve cardiac dysfunction by inducing cardiac expression of a cardioprotective cytokine, adiponectin. We examined the relationship between weight loss by food restriction and heart failure due to viral myocarditis in obese KKAy mice. We intraperitoneally injected encephalomyocarditis virus (500 plaque-forming units/mouse) into KKAy mice fed ad libitum as a control (CF) or 60% restriction of that eaten by ad libitum (RF). The 14-day survival rate was 0% in FF, whereas it was 23% in RF (P < 0.01). Heart weight/body weight ratio in RF was lower than that in FF on day 5 after viral inoculation (P < 0.05). Histological scores for myocardial necrosis and inflammation on day 5 were significantly lower in RF than in FF (P < 0.05). Circulating adiponectin level on day 0 was significantly elevated in RF compared with that in FF (32 + 9 vs. 22 + 2 μg/mL, P < 0.05). Comparative expression of cardiac adiponectin mRNA in RF was significantly higher than that in FF (5.1 + 0.3 vs. 1 + 0.2, P < 0.05). Cardiac tumor necrosis factor-alpha (TNF-alpha) mRNA in RF was significantly decreased compared with that in FF on day 5 (P < 0.05). Cardiac expression of nuclear factor kappa B was reduced and that of peroxisome proliferator-activated receptor gamma mRNA was increased in RF in comparison with FF on day 0. Cardiac adiponectin mRNA was negatively correlated with cardiac TNF-alpha mRNA (r = − 0.555; P = 0.0097). Weight loss improved the survival and myocardial damage in obese mice with viral myocarditis, with cardiac induction of adiponectin. The induction of adiponectin might provide benefit through a cardioprotective effect against acute heart failure due to viral myocarditis in obese subjects.