Question

Under normal conditions, healthy heart cells (cardiac myocytes)prefer fatty acids as their fuel which ultimately results in energy being generated from oxidative phosphorylation through the electron transport chain. We will talk about how fatty acids are oxidatively metabolized in lecture 10. The condition ischemic cardiomyopathy is a result of narrowing of heart arteries which leads to decreased blood flow and a decrease in oxygen delivery to the muscle cells of the heart. In the ischemic heart, metabolism shifts from fatty acid oxidation to glucose metabolism via glycolysis to generate ATP and supply energy needs. a) Please explain why the ischemic heart shifts from energy generated by fatty acids to energy generated by glucose. b) In the ischemic heart, an increase in glycolysis is not associated with an increase in glycolytic enzyme expression. What is the general means by which the increase in glycolysis is mediated if it is not via an increase in enzyme expression? c) In ischemic cardiomyopathy, the decreased blood flow to the heart results in a decrease in blood glucose moving through hart arteries. Given that glycolysis is increased in the ischemic heart, discuss two potential ways that heart cells can acutely (in a rapid time period) increase glucose levels to supply the increased demand for glycolysis.

Answer 1

1. The ischemic heart shifts from energy generated by fatty acids to energy generated by glucose because glucose is an important source of energy in ischemic heart because glycolysis can occur in the absence of oxygen.
2. The cells in ischemic heart will undergo Warburg effect. It is a conversion of glucose to lactic acid.
3. The heart can use stored glycogen and fatty acid oxidation are two potential ways that heart cells can acutely (in a rapid time period) increase glucose levels to supply the increased demand for glycolysis.