2008 — 2010 |
Hollander, John Michael [⬀] |
DP2Activity Code Description: To support highly innovative research projects by new investigators in all areas of biomedical and behavioral research. |
Mechanisms of Diabetic Cardiomyopathy: Mitochondria Subpopulations Brought to Foc @ West Virginia University
Project Summary / Abstract One to two million people in the United States, suffer from type 1 diabetes mellitus. Diabetic cardiomyopathy is an impairment of heart muscle that exists independently of coronary artery disease, and is associated with diabetes mellitus. Diabetic cardiomyopathy is characterized by contractile dysfunction which contributes to myocardial infarction and heart failure. Hyperglycemia associated with diabetes mellitus, increases reactive oxygen species (ROS) generation. Because the mitochondrion is the primary site for ROS generation, determination of how mitochondria are affected by diabetes mellitus is crucial for understanding the pathogenesis. Examination of mitochondria is complicated by the fact that two mitochondrial subpopulations are present in the cardiomyocyte, interfibrillar mitochondria (IFM), which situate between the contractile apparatus and subsarcolemmal mitochondria (SSM) that exist beneath the plasma membrane. Currently, it is unclear how spatially distinct mitochondrial subpopulations are effected by diabetes mellitus making it difficult to ascertain their specific contribution to diabetic cardiomyopathy. Our long-term goal is to elucidate the mechanisms involved in the pathogenesis of diabetic cardiomyopathy as a prerequisite to the development of therapeutics designed to lessen cardiac complications associated with diabetes mellitus. The central hypothesis of this application is that cardiac IFM are at greater risk from diabetic insult than SSM. The objectives of this application are to determine the effect of diabetic insult on spatially distinct mitochondrial subpopulations, identify key factors that contribute to dysfunction in specific mitochondrial subpopulations, and to develop therapeutics that target spatially distinct mitochondria subsets. Public Health Relevance Statement The proposed studies will enhance our understanding of the pathogenesis of diabetic cardiomyopathy providing information regarding targets for therapeutic interventions that will aid in the treatment of type 1 diabetes mellitus. The genesis of therapeutic tools designed to treat specific mitochondrial subsets will enhance therapy option flexibility, and provide a better means for the treatment of loci at risk from diabetes mellitus.
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0.948 |
2015 — 2019 |
Hollander, John Michael [⬀] |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. R56Activity Code Description: To provide limited interim research support based on the merit of a pending R01 application while applicant gathers additional data to revise a new or competing renewal application. This grant will underwrite highly meritorious applications that if given the opportunity to revise their application could meet IC recommended standards and would be missed opportunities if not funded. Interim funded ends when the applicant succeeds in obtaining an R01 or other competing award built on the R56 grant. These awards are not renewable. |
Mirna Regulation of the Mitochondrial Genome @ West Virginia University
? DESCRIPTION (provided by applicant): Type 2 diabetes mellitus incidence has increased dramatically. Among the life threatening complications is heart failure, which is preceded by bioenergetic dysfunction. Using mouse (db/db) and human (patient) type 2 diabetic models; we observed pronounced mitochondrial dysfunction culminating in a decreased ability to generate ATP for cardiac contraction. MicroRNAs (miRs) are non-coding RNAs that regulate translation. Using cross-linking immunoprecipitation and deep sequencing, we made the exciting observation, in both db/db and type 2 diabetic patients that miRs translocate into and out of cardiac mitochondria. Of particular interest was an increased miR- 378 presences in a functional regulatory context with mitochondrial genome-encoded ATP6 mRNA which codes for a subunit of the F0 proton motor that is part of the ATP synthase complex. Decreased ATP synthase functionality promotes bioenergetic deficit in the heart, promoting heart failure. Nevertheless, it is currently unclear whether miR-378 blockade can reduce mitochondrial dysfunction associated with the type 2 diabetic heart by direct interaction with the mitochondrial genome. Further, the mechanisms responsible for the dynamic flux of miRs into the mitochondrion are undefined. One potential mechanism involves the participation of the mitochondrial RNA import protein polynucleotide phosphorylase (PNPase) which we have observed to be increased in mitochondria from db/db mice and type 2 diabetic patients. The studies being proposed address these gaps in knowledge and integrate in vitro cellular approaches with animal and human experimental models in an effort to translate the findings to the type 2 diabetic patient. The central hypothesis of this application is that inhibition of miR-378 disrupts its ability to down-regulate ATP6 in the mitochondrion, preserving ATP synthase function as well as ATP levels, and limiting cardiac contractile dysfunction in the type 2 diabetic hearts. Further, miR-378 flux into the mitochondrion can be modulated by PNPase manipulation. The objectives of this application are: (1) determine the impact in vivo of a prophylactically delivered miR-378 inhibitor in a type 2 diabetic mouse model for restoring mitochondrial ATP6 protein expression and ATP generating capacity in the heart; (2) evaluate the therapeutic efficacy of a miR-378 inhibitor delivered to isolated human cardiomyocytes from type 2 diabetic patients; and (3) assess the contribution of PNPase to the mechanisms driving miR-378 flux into the mitochondrion. To test this hypothesis, an innovative approach has been proposed which employs antagomir intervention to manipulate mitochondrial genome-encoded proteins in an effort to mitigate diabetes- associated contractile dysfunction. The combination of work proposed is significant because it will provide insight into the mechanisms regulating miR distribution in the mitochondrion while providing translational insight into the therapeutic potential of miR-378 inhibition as a treatment strategy. Our approach merges mechanistic examination of a previously unexplored regulatory pathway contributing to mitochondrial dysfunction in the diabetic heart with preclinical evaluation of key molecular constituents participating in the axis.
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0.948 |