Role of Ryanodine Receptors in Diabetic Cadiomyopathy

描述(由申请人提供)：细胞内钙循环的扰动是1型糖尿病(T1D)患者和所有T1D动物模型心肌收缩能力下降的主要原因。造成这种缺陷的蛋白质之一是2型Ryanodine受体(RyR2)，它是钙离子离开肌浆网实现收缩的通道。到目前为止，T1D期间RyR2功能障碍的确切分子机制仍不清楚。我们的实验室最近发现，链脲佐菌素(STZ)诱导的糖尿病大鼠心脏功能失调的RyR2在选定的碱性残基上含有羰基加合物。用吡哆胺治疗糖尿病大鼠，以清除活性羰基，钝化糖尿病引起的RyR2功能障碍，使心肌细胞兴奋-收缩偶联和心肌收缩能力正常化。运动训练STZ-糖尿病大鼠还减少了反应性羰基的产生，减少了RyR2上羰基加合物的形成，恢复了心室肌细胞的兴奋-收缩偶联，并钝化了糖尿病引起的心肌收缩能力下降。这些新数据表明，长寿的RyR2的羰基加合物(羰化)的形成在功能上是重要的，而不是糖尿病的附带现象。我们的中心假说是“糖尿病导致RyR2上关键氨基酸残基的甲基化，导致RyR2功能障碍、兴奋-收缩偶联功能障碍和心力衰竭。”我们将使用细胞培养和STZ-糖尿病大鼠模型来(I)阐明在糖尿病期间羰基加合物改变RyR2功能的分子机制，以及(Ii)确定吡哆胺治疗和运动训练减轻T1D期间RyR2功能障碍的分子机制。来自该项目的数据将为这组未被研究的细胞氧化剂(活性羰基物种)如何损害RyR2的活性，导致T1D期间兴奋-收缩偶联缺陷和心肌收缩能力降低提供有价值的机制见解。由于在2型糖尿病和代谢综合征中也会出现蛋白质的羰基应激和羰化，从这个项目中获得的知识也可能有助于设计新的治疗策略来管理这些人的心肌功能障碍。 综述：心力衰竭是糖尿病患者发病率和死亡率的主要原因。然而，这种心力衰竭的原因尚不完全清楚。该项目旨在加深我们对糖尿病患者心力衰竭原因的理解。这项研究特别重要，因为它可以帮助开发新的治疗策略/选择，以改善糖尿病患者的生活质量，并控制糖尿病护理不断上升的经济成本，估计每年超过1320亿美元。

DESCRIPTION (provided by applicant): Perturbation of intracellular Ca2+ cycling is a primary cause for the depressed myocardial contractility in individuals with type 1 diabetes (T1D) and in all animal models of T1D. One of the proteins that contribute to this defect is type 2 ryanodine receptor (RyR2), the channel through which Ca2+ leave the sarcoplasmic reticulum to effect contraction. To date, precise molecular mechanisms responsible for RyR2 dysfunction during T1D remain unknown. Our laboratory recently found that dysfunctional RyR2 from streptozotocin (STZ)-induced diabetic rat hearts contain carbonyl adducts on select basic residues. Treatment of diabetic rats with pyridoxamine to scavenge reactive carbonyl species blunted diabetes-induced dysfunction of RyR2, normalize myocyte excitation-contraction coupling and myocardial contractility. Exercise training STZ-diabetic rats also reduced production of reactive carbonyl species, decreased formation of carbonyl adducts on RyR2, restored excitation-contract coupling in ventricular myocytes and blunted diabetes- induced reduction in myocardial contractility. These new data suggest that formation of carbonyl adducts (carbonylation) of long-lived RyR2 is functionally important and not an epiphenomenon of diabetes. Our central hypothesis is "diabetes leads to carbonylation of critical amino acid residues on RyR2, causing RyR2 dysfunction, impairment of excitation-contraction coupling and heart failure." We will use cell culture and STZ-diabetic rat models to (i) elucidate molecular mechanisms by which carbonyl adducts alter RyR2 function during diabetes, and (ii) determine molecular mechanisms by which pyridoxamine treatment and exercise training attenuate RyR2 dysfunction during T1D. Data from this project will provide valuable mechanistic insights into how this group of understudied cellular oxidants (reactive carbonyl species) impairs the activity of RyR2, leading to defective excitation-contraction coupling and reduced myocardial contractility during T1D. Since carbonyl stress and carbonylation of proteins also occurs in type 2 diabetes and metabolic syndrome, knowledge gained from this project could also be useful in designing newer therapeutic strategies for management of myocardial dysfunction in these individuals as well. Lay summary: Heart failure is a primary cause of morbidity and mortality in diabetic patients. However, the cause of this heart failure is not fully understood. This project is designed to further our understanding as to why the heart fails in individuals with diabetes. This research is especially important since it could help in the development of newer therapeutic strategies/options to improve the quality of life of diabetic patients and control the escalating economic cost of diabetes care, which is estimated to be in excess of $132 billion annually.