L26-cardiac Metabolism Flashcards
% of fuels to heart
60-80% from free fatty acids and triglycerides
10-30% from carbs
10-30% lactate
Ketone bodies under certain conditions
When are carbohydrates used as source of energy instead of FFA and what are the 3 main sources
In cases of ischemia
1-extracellular glucose
2-extracellular lactate
3-glycogen stores
Glucose transporters and location
GLUT1 GLUT4(predominant) In sarcolemmal membrane and intracellular microsomal vesicles
What happens to glucose when it enters the cell
Phosphorylation by hexokinase forming glucose 6 phosphate
Glucose and lactate converted to pyruvate
CAC
What does randle’s cycle refer to
Significant reduction in uptake and utilization of glucose that occurs in muscle when fatty acid oxidation is intense
What are the main effects of FFA and ketone bodies
To inhibit Activity of PDH and dec conversion of pyruvate to acetyl coA
What is the rate of pyruvate oxidation dependent on
Degree of phosphorylation of PDH
phosphorylation= dec activity by PDH kinase
DePhosphorylation=inc activity by PDH phosphatase
When is activity of PDH kinase inc
By inc in levels of actylcoA/CoA and NADH/NAD ratios
What do partial FFA oxidation inhibitors do
Ex:pFOX inhibitors
Group of anti anginal drugs
Shift cardiomyocyte metabolism to utilization of CHO rather than FFA (less O2 demand)
Sparing O2 to ischemic myocardium
Effects of insulin on carbohydrate metabolism in heart
Causes heart to take up and oxidize more glucose and lactate through direct and indirect mechanisms:
1-directly inc glucose uptake by stimulation of GLUT1 and 4
2-inc activity of hexokinase enzyme
3-inc activity of glycogen synthase and inc glycogen storage
Effect of insulin on fatty acids
Lowers circulating FFA by:
1-suppressing fatty acid release(lipolysis) from fat cells
2-high insulin results in low fatty acid levels and low rates of fatty acid uptake and oxidation by heart and dramatic inc in glucose and lactate uptake and oxidation
