ABSTRACT In the US there are >700,000 new heart attacks (acute myocardial infarctions) a year, and >300,000 patients undergo scheduled ischemia during cardiac surgery. Beyond tissue reperfusion (angioplasty, thrombolysis) there are no FDA-approved interventions to limit acute cardiac injury due to ischemia and reperfusion (IR). This renewal proposal supports our ongoing research program in cardiac metabolism, and is focused on novel cardioprotective metabolic signaling events downstream of glycolysis. It is built on the following premise: (i) Acidic pH during IR is cardioprotective, and many therapies that boost glycolysis work in-part by enhancing metabolic acidosis. (ii) Succinate accumulation is a key event in ischemia, and its oxidation at reperfusion drives reactive oxygen species generation. We propose acid can regulate succinate dynamics (accumulation, oxidation, transport). (iii) The glycolytic byproduct methylglyoxal (MGO) causes glycative stress in diabetes, but type-I diabetic hearts are acutely protected against IR injury, and MGO inhibits the mitochondrial permeability transition (PT) pore, a key event in IR injury. Some cardioprotective interventions also elevate MGO. (iv) The mitochondrial enzyme ALKBH7 is necessary for necrosis. Inhibition or ablation of ALKBH7 is cardioprotective, and this protection requires the MGO metabolizing enzyme GLO-1. Based on these published and preliminary findings, our central hypothesis is that the cardioprotective effects of elevated glycolysis are mediated by pH, succinate, and MGO. This hypothesis will be tested by addressing 3 related aims… Aim 1 will investigate succinate dynamics in IR injury and the impact of pH. Aim 2 will investigate the role of MGO as an acute cardioprotective signal, including identifying its targets in mitochondria. Aim 3 will study ALKBH7, identify its substrates, and develop ALKBH7 inhibitors as cardioprotective drugs. The aims will use established experimental systems (adult cardiomyocytes, perfused hearts, LC-MS based metabolomics, in-vivo IR injury, and a high-fat diet model of diabetes) and engineered mice including Alkbh7-/-, Glo1-/- and hGlo1TG. Innovation is embedded in the idea that MGO can serve an acute protective signaling role separate from its well-known chronic pathologic effects (i.e. hormesis). This work will advance basic knowledge on ischemic cardiac metabolism, will develop small molecule therapeutics, and will offer mechanistic insights to other pathologies beyond IR.

PROJECT NARRATIVE Heart attack (myocardial infarction) is a major killer in western society, so there is a drastic need for therapies to avoid myocardial injury. The heart is a very metabolically demanding organ, but there are still large gaps in our knowledge of cardiac metabolism. We have identified several key metabolic events that take place during and after heart attack, and this project will investigate how manipulating these events can impact the outcome of heart attack. Specifically, under conditions of chronic hyperglycemia such as seen in diabetes, there is an elevation of the metabolite methylglyoxal (MGO), and this is generally thought to be detrimental to the heart. However, we have identified novel mechanisms in which acute MGO may elicit beneficial signaling effects to protect against heart attack.