This research will be done primarily in South Africa at Stellenbosch University by Dr. M. Faadiel Essop, as a (collaborative) extension of Dr. Stanley's NIH Grant No. P01 HL074237 (funded 8/15/2009 to 7/30/2014). This collaborative research project stems from Drs. Stanley and Essop's mutual interest in the role of myocardial substrate metabolism in heart failure. Dr. Essop is based at the Dept. Physiological Sciences at Stellenbosch University (South Africa), and has established a productive collaboration with Dr. Stanley. There has been a marked increase for the incidence of cardiovascular disease (CVD) in Africa, and recent data suggest that the dramatic surge in CVD rates are largely due to lifestyle changes. Epidemiological studies from the US and Europe recently showed that high intake of carbohydrates with a high glycemic index (e.g. sugars and refined starches) are a strong independent predictor of CVD, and public health efforts are now focused on removing "empty carbohydrates" from the diet. These findings have led Dr. Essop to study the link between suboptimal nutrition and the increased CVD. The foundations for this collaboration are the limited knowledge regarding the effects of macronutrient intake on cardiomyocyte function and the observation by Dr. Essop that increased flux through the hexosamine biosynthetic pathway plays a crucial role in hyperglycemia- induced myocardial cell death. This project will combine Dr. Essop's expertise in molecular and cell biology with Dr. Stanley's expertise in nutrition and the pathophysiology of heart failure. Extensive cell-based and biochemical studies will be performed in Stellenbosch, while in vivo functional studies will be performed in Dr. Stanley's laboratory. The general hypothesis is that oxidative stress resulting from intake of high glycemic foods activates the HBP leading to increased O-GlcNAcylation of cardiac apoptotic proteins and elevated myocardial apoptosis, thereby accelerating the development and progression to heart failure. Specifically, we propose that there is increased BAD O-GlcNAcylation and BAD-Bcl-2 dimerization, thus accelerating apoptosis. There are two Specific Aims:
Aim 1 : Evaluate the role of HBP in the acceleration of heart failure with a high sugar diet. Studies will be performed in normal mice and animals subjected to a chronic increase in arterial pressure to induce heart failure, and the dietary glycemic load will be manipulated. The role of ROS production will be assessed. Cardiomyocyte apoptosis will be determined, and the biochemical assessment of HBP and O- GlcNAcylation of apoptotic proteins will be preformed.
Aim 2 : Assess the effects of hyperglycemia-mediated induction of the HBP on O-GlcNAcylation of apoptotic proteins. Systematic in vitro studies will be performed in isolated cardiac cells to determine the mechanism(s) of hyperglycemia-mediated myocardial apoptosis.
There has been a marked increase for the incidence of cardiovascular disease (CVD) in Africa, which is associated with an increase in refined carbohydrate in the diet. Recent studies showed that high intake of sugars and refined starches are a strong independent predictor of CVD, though the mechanism for this effect is not known. This project will investigate the biochemical mechanisms behind this observation, specifically the role of oxidative stress and apoptosis in the heart.