Diabetes mellitus results in a diabetic cardiomyopathy (DC) with decreased cardiac contractile function and heart failure independent of vascular disease. Abnormal calcium (Ca) handling importantly contributes to DC with the sarcoplasmic reticulum (SR) CaATP'ase (SERCa2) being significantly decreased resulting in abnormal diastolic calcium flux.
In Aim I, we will determine if in transgenic (Tg) mice made diabetic (D)tetracycline (Tet) transactivator based conditional increases in SERCa2 activity have a positive or a negative Iongterm effect on contractile function and survival. Our result show that Tet based SERCa2 expression is feasible in DC hearts and has a positive contractile effect. We will also explore the effect of SERCa2 expression on the high energy phosphate status and positive or negative cardiac remodeling using Tg mice or viral vectors. Our results show that systolic Ca flux is abnormal and in Aim II, we will use conditional expression of putative ryanodine receptor (RyR2) interacting proteins: Sorcine, Homerlc and FKBP12.6 to influence systolic Ca handling. Our results show a positive effect of Sorcine, Homerlc, and FKBP12.6 expression on contractile function in DC hearts. We are interested in comparing the effects of SERCa2 vs.RyR2 interacting protein on the energetic status of the heart, remodeling and survival. In addition, D induced abnormalities in mitochondrial Ca handling, which we recently identified, will be explored.
In aim III, the contribution which O-linked glycosylation and hexosamine pathway activity makes to DC will be explored.Our result indicate that increased viral vector based expression of the O-GIcNAcase enzyme which removes N-acetyl glucosamine from proteins in myocytes from D hearts under in vivo conditions can improve Ca flux and contractile handling in spite of persistent hyperglycemia. These interesting results will be extended and specific proteins having altered O-glycosylation are identified. Novel insights and approaches to improve contractile function of the D heart in spite of persistent hyperglycemia will result from these investigations. ? ? ?
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