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.

Public Health Relevance

Type 2 diabetes mellitus incidence has increased dramatically. The prognosis for many of these subjects is poor, impacting healthcare costs, substantially. The proposed experiments are relevant to public health because they will enhance our understanding of the pathogenesis of diabetes-induced heart failure and provide information regarding targets for preventive and therapeutic interventions that will aid in the treatment of diabetes mellitus in the type 2 diabetic patient. Thus, the proposed research is relevant to the NIH's mission that pertains to the pursuit of fundamental knowledge to extend healthy life and reduce the burden of illness.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
High Priority, Short Term Project Award (R56)
Project #
1R56HL128485-01
Application #
9130443
Study Section
Myocardial Ischemia and Metabolism Study Section (MIM)
Program Officer
Wong, Renee P
Project Start
2015-09-08
Project End
2016-08-31
Budget Start
2015-09-08
Budget End
2016-08-31
Support Year
1
Fiscal Year
2015
Total Cost
$409,705
Indirect Cost
$135,043
Name
West Virginia University
Department
Physiology
Type
Schools of Medicine
DUNS #
191510239
City
Morgantown
State
WV
Country
United States
Zip Code
26505
Nichols, Cody E; Shepherd, Danielle L; Hathaway, Quincy A et al. (2018) Reactive oxygen species damage drives cardiac and mitochondrial dysfunction following acute nano-titanium dioxide inhalation exposure. Nanotoxicology 12:32-48
Shepherd, Danielle L; Hathaway, Quincy A; Nichols, Cody E et al. (2018) Mitochondrial proteome disruption in the diabetic heart through targeted epigenetic regulation at the mitochondrial heat shock protein 70 (mtHsp70) nuclear locus. J Mol Cell Cardiol 119:104-115
Stapleton, P A; Hathaway, Q A; Nichols, C E et al. (2018) Maternal engineered nanomaterial inhalation during gestation alters the fetal transcriptome. Part Fibre Toxicol 15:3
Baradan, Rohini; Hollander, John M; Das, Samarjit (2017) Mitochondrial miRNAs in diabetes: just the tip of the iceberg. Can J Physiol Pharmacol 95:1156-1162
Shepherd, Danielle L; Hathaway, Quincy A; Pinti, Mark V et al. (2017) Exploring the mitochondrial microRNA import pathway through Polynucleotide Phosphorylase (PNPase). J Mol Cell Cardiol 110:15-25
Corbin, Deborah R; Rehg, Jerold E; Shepherd, Danielle L et al. (2017) Excess coenzyme A reduces skeletal muscle performance and strength in mice overexpressing human PANK2. Mol Genet Metab 120:350-362
Shepherd, Danielle L; Nichols, Cody E; Croston, Tara L et al. (2016) Early detection of cardiac dysfunction in the type 1 diabetic heart using speckle-tracking based strain imaging. J Mol Cell Cardiol 90:74-83