DOI
https://doi.org/10.25772/EWXS-ZF90
Defense Date
2012
Document Type
Dissertation
Degree Name
Doctor of Philosophy
Department
Physiology
First Advisor
RAKESH KUKREJA
Abstract
Insulin resistance and chronic hyperglycemia promote vascular damage, increase circulating levels of inflammatory cytokines and lead to increased morbidity and mortality. MicroRNAs (miRs) -103/107 have been shown to negatively regulate insulin sensitivity and glucose homeostasis. Based on complimentary binding profiles, the downstream target gene of miR-103/107 is caveolin-1 (Cav-1). We hypothesized that daily administration of the phosphodiesterase-5 inhibitor tadalafil (TAD) ± the curcumin analogue (HO-3867) will attenuate inflammation, improve metabolic parameters and reduce infarct size after ischemia/reperfusion injury (IRI). Furthermore, we propose that TAD therapy will reduce myocardial expression of miR-103/107 and increase mRNA and protein levels of its target gene, Cav-1. Leptin receptor null mice were randomized to receive daily injections of TAD (1mg/kg), HO-3867 (25mg/Kg), combination therapy, or control for 12weeks with weight and fasting glucose monitored weekly. Upon completion, cardiomyocytes were isolated from each group and were subjected to simulated ischemia and reoxygenation (SI/RO) for cell viability and reactive oxygen species (ROS) measurement. Another set were subjected to IRI in a Langendorff model. Plasma samples were taken to measure plasma concentrations of cytokines. For miR expression, total RNA was isolated from TAD and DMSO treated mice and was subjected to reverse transcription and real time PCR using miR assay probes to determine expression. TAD, HO-3867 and the combination of both attenuated fasting glucose levels, reduced myocardial infarct size after IRI and inflammatory cytokines when compared to control (p<0.05 for each vs. control). Cardiomyocytes isolated from each treatment groups and subjected to SI/RO demonstrated reduced necrosis as shown by trypan blue exclusion assay, ROS generation, and improved mitochondrial membrane potential as compared to DMSO (control). Likewise, both mRNA and protein expression of Cav-1 were reduced in diabetic hearts but were significantly increased in TAD treated diabetic mice, which may be a mechanism to improve insulin signaling through downregulation of miR-103/107 and upregulation of Cav-1. These studies suggest that TAD alone or in combination may be a unique strategy to improve metabolic parameters and precondition diabetic hearts against IRI.
Rights
© The Author
Is Part Of
VCU University Archives
Is Part Of
VCU Theses and Dissertations
Date of Submission
November 2012