Keshore Bidasee - US grants

[unreadable] 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. [unreadable] 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. [unreadable] [unreadable] [unreadable]

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Individuals with diabetes mellitus (DM) have cerebral microvascular diseases including ischemic and lacunar strokes at rates three to five times higher than that of the general population. The extent of brain damage following a stroke is also aggravated in these individuals. Even more troubling, are the observations that diabetic patients who have tight blood glucose control still develop cognitive impairment and are at a higher risk of developing spontaneous Alzheimer's disease. Recent studies suggest that these defects stem in part from an increase in blood-brain-barrier (BBB) permeability. What remain elusive are the molecular triggers responsible for initiating BBB breach. Exciting new data emerging from our laboratory as well as a few others indicate that reactive carbonyl species (RCS) generated during diabetes may be one of these triggers. Our working hypothesis is that "RCS generated during diabetes interact with and compromise the function of endothelial cells resulting in BBB breach and increased incidence of Neurological disorders." We will use in vitro studies to elucidate mechanisms by which RCS compromise brain endothelial cell function and in vivo studies to show that chronic elevation of RCS leads to blood brain barrier breach and an increase in cerebral damage following cerebral artery occlusion. The proposed research will provide data in support of the concept of "RCS-ROC coupling." It will also provide mechanistic insights into how this group of understudied cellular oxidants impairs endothelial cell function leading to incrased BBB permeability, the basis for a direction of an R01 application. More globally, data from the proposed research could also be useful for developing newer therapeutic strategies to slow the progression of cardiovascular diseases during diabetes, 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.