Restoration of Cardiac Function After Myocardial Infarction by Long-Term Activation of the CNS Leptin-Melanocortin System.

Animal study investigating the effects of central leptin and MC4R activation on cardiac function after myocardial infarction

“In the present study we tested the hypothesis that leptin improves cardiac metabolism and attenuates cardiac dysfunction after MI via CNS actions.”

Male Sprague-Dawley rats and MC4R-knockout rats

“Experiments were performed in 12- to 14-week-old male Sprague-Dawley rats purchased from Harlan/Envigo (Houston, Texas), and MC4R-knockout rats from our colony maintained at the animal facilities at the University of Mississippi Medical Center.”

Groups of 4 to 8 rats per treatment condition

“Values are mean ± SEM obtained on day 28 of chronic ICV infusion.ICV = intracerebroventricular; MTII = melanotan II.∗p < 0.05 compared with vehicle (n = 6 to 8 per group).”

28 days of intracerebroventricular infusion following myocardial infarction

“to deliver leptin (0.62 μg/h), vehicle (saline, 0.5 μl/h), or the MC4R agonist melanotan II (MTII) (10 ng/h) for 28 consecutive days.”

Central leptin infusion improved cardiac function and attenuated heart failure progression after myocardial infarction

“ICV leptin infusion post-MI significantly improved ejection fraction and fractional shortening compared with vehicle treatment (Figures 2C and 2D).”

Activation of brain MC4R recapitulated the cardiac protective effects of leptin

“ICV MTII infusion prevented the decreases in BP and HR that were observed in vehicle-treated rats after MI (Figures 2A and 2B), and similar to our observations with ICV leptin infusion, MTII also markedly improved ejection fraction and fractional shortening compared with vehicle treatment (Figures 2C and 2D).”

Leptin's cardiac protective effects require functional brain MC4R

“ICV leptin infusion failed to improve cardiac function in MC4R-knockout rats post-MI, and we observed similar reductions in cardiac output, ejection fraction, fractional shortening, and radial strain in ICV leptin–treated rats compared with vehicle treatment (Figures 5A to 5D).”

The study used intracerebroventricular administration, which is impractical for clinical settings, and the causal link between early metabolic changes and later functional improvements is not fully established

“A limitation of our study is that we used ICV administration of leptin and MC4R agonist, which is impractical in clinical settings.”