Heart beat
Diabetic patients are more than twice as likely to die from a heart attack as non-diabetic patients, but the mechanisms that underlie increased heart attack-related mortality in diabetic patients are unknown. High levels of the oxidized form of the protein CamKII (ox-CaMKII) have been linked to increased risk of sudden death after heart attack. Additionally, hearts from diabetic patients have significantly greater ox-CAMKII compared to hearts from non-diabetic patients. Heart attack-related cell death changes the pacemaker and conduction activity, leading to a decrease in heart rate. Here, Min Luo and colleagues created a 2D mathematical model of sinoatrial node (SAN) activity based on cell death in the hearts of wild type mice and diabetic mice. Videos of SAN activity in wild type and diabetic hearts can be viewed here and here. Luo and colleagues engineered a transgenic mouse to express a form of CaMKII that cannot be oxidized in the heart muscle. They found that diabetic mice expressed the non-oxidizable form of CamKII were less likely to die after a heart attack than mice that expressed normal CamKII. These findings suggest that ox-CAMKII may also increase post-heart attack mortality in diabetic patients and indicate that therapies that reduce oxidation of CamKII could be useful in treating diabetic patients who suffer from cardiovascular disease.
Related articles
Abstract
Diabetes increases oxidant stress and doubles the risk of dying after myocardial infarction, but the mechanisms underlying increased mortality are unknown. Mice with streptozotocin-induced diabetes developed profound heart rate slowing and doubled mortality compared with controls after myocardial infarction. Oxidized Ca2+/calmodulin-dependent protein kinase II (ox-CaMKII) was significantly increased in pacemaker tissues from diabetic patients compared with that in nondiabetic patients after myocardial infarction. Streptozotocin-treated mice had increased pacemaker cell ox-CaMKII and apoptosis, which were further enhanced by myocardial infarction. We developed a knockin mouse model of oxidation-resistant CaMKIIδ (MM-VV), the isoform associated with cardiovascular disease. Streptozotocin-treated MM-VV mice and WT mice infused with MitoTEMPO, a mitochondrial targeted antioxidant, expressed significantly less ox-CaMKII, exhibited increased pacemaker cell survival, maintained normal heart rates, and were resistant to diabetes-attributable mortality after myocardial infarction. Our findings suggest that activation of a mitochondrial/ox-CaMKII pathway contributes to increased sudden death in diabetic patients after myocardial infarction.
Authors
Min Luo, Xiaoqun Guan, Elizabeth D. Luczak, Di Lang, William Kutschke, Zhan Gao, Jinying Yang, Patric Glynn, Samuel Sossalla, Paari D. Swaminathan, Robert M. Weiss, Baoli Yang, Adam G. Rokita, Lars S. Maier, Igor R. Efimov, Thomas J. Hund, Mark E. Anderson
Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)