Metformin and left ventricular remodeling after acute myocardial infarction: molecular mechanisms and clinical implications

Despite clear advances in reperfusion therapy and pharmacological treatment, a large proportion of patients with an acute myocardial infarction will die of its consequences. In this regard, it is very important to understand the molecular processes underpinning ischemia-reperfusion injury and occurrence of left ventricular dysfunction, with the aim to develop mechanism-based therapeutic strategies. Experimental evidence indicates that metformin, a biguanide often used in the treatment of diabetes, has favorable effects on left ventricular function. This effect is largely mediated by activation of AMP-activated protein kinase (AMPK), a key molecule orchestrating many biochemical processes such as glucose uptake, glycolysis, oxidation of free fatty acids and mitochondrial biogenesis. These processes significantly contribute to raise ATP levels and restore myocardial contractile efficiency. AMPK also activates endothelial nitric oxide synthase and promotes autophagy, thus preventing inflammation and cellular death. These basic studies prompted many researchers to test the cardioprotective effects of metformin in the clinical setting. In diabetic patients with ST-elevation myocardial infarction (STEMI), retrospective analyses showed that metformin is associated with reduced infarct size as compared to non-metformin-based strategies, implicating beneficial effects beyond glucose control. A recent randomized trial, the GIPS-III study, has postulated that metformin may improve left ventricular function following STEMI even in patients without diabetes. Metformin (500 mg twice/day), administered 3h after percutaneous coronary intervention, did not result in improved left ventricular ejection fraction after 4-month follow-up. Based on these results, it remains unclear whether metformin exerts a cardioprotective effect regardless of glycemic control. Further randomized studies in diabetic and nondiabetic patients are required to address these important questions. The present review critically discusses established knowledge and evidence gaps on the effects of metformin on left ventricular function in diabetic and nondiabetic patients with myocardial infarction.