Novel work has demonstrated a mechanistic link between changes in the intestinal microbiota and severity of myocardial infarction. Treatment of Dahl S rats with the commercially available probiotic bacterium Lactobacillus plantarum 299v, and a non-absorbed antibiotic vancomycin to alter abundance of multiple microbiota reduced circulating leptin levels, reduced myocardial infarct size, and improved recovery of post-ischemic mechanical function. Pretreatment with leptin abolished cardioprotection by the probiotic and the antibiotic.