Cardiac Fuels

Question 1

Almost ….. of cardiac emergy is generated from oxidative phosphorylation.

Answer 1

> 95%

Question 2

….. of cardiac ATP is used for contraction, the rest is used for ….

Answer 2

60-70%

Fueling ion pumps esp Ca-ATPase

Question 3

Mention ATP & PCr content of cardiac muscle & the turnover rate of ATP.

Answer 3

5 micromol/g (ATP)
8 micromol/g (PCr)
10s

Question 4

PCr is formed from ATP by …., while ATP is formed from PCr by…..

Answer 4

Mitochondrial creatine kinase

Cytosolic creatine kinase

Question 5

Mention the cardiac fuels & the two most used.

Answer 5

Fatty acid (major source, 80%)
Glucose metabolism (remaining quantity)
Lactate
Ketone bodiea

Question 6

Mention effect of low to moderate exercise in contrast to effect of high intensity exercise on cardiac muscle metabolism

Answer 6

L to M, increased uptake of glucose from blood and lactate generated from skeletal muscle, without change in fatty acid oxidation.
H, glucose utilization relatively drops.

Question 7

Glucose is transported though ……

Answer 7

GLTU-4, GLUT-1 (less)

Question 8

Mention factors increasing rate of glucose transport and uptake.

Answer 8

Insulin stimulation, increased work demand or ischemia.

Question 9

Net ATP production per 1 glucose molecule is ….

Answer 9

36-38

Question 10

Mention factors which increse FFA level in plasma

Answer 10

Physical exercise, fasting or myocardial ischemia

Question 11

FFA enter cardiomyocyte by …..& …

Answer 11

Passive diffusion or protein mediated transport

Question 12

Mention fate of long chain fatty acyl CoA in cardiomyocyte

Answer 12

Either esterified to triacyglycerol OR converted to acycarnitine by CAT1 then transported into mitochondria, where AcylCoA is regenerated by CAT2 to share in beta-oxidation.

Question 13

Net energy generated by beta-oxidation of palmitate.

Answer 13

129 ATP

Question 14

The two functional water soluble KB are ……

Answer 14

Acetoacetate

3-hydroxybutyrate

Question 15

The primary physiological regulator of PDH activity is ……

Answer 15

Fatty acid oxidation

Question 16

The mechanism by which FA oxidation inhibits PDH

Answer 16

Increase mitochondrial acetyl-CoA/free CoA and NADH/NAD+ which activates PDH kinase

Question 17

Stressful conditions increase …. which stimulate ….., resulting in inhibition of …. oxidation

Answer 17

Catecholamines
Lipolysis
Glucose

Question 18

Mention the downstream effects of of high anaerobic glycolysis and low glucose oxidation in cardiac muscle.

Answer 18

Lactate and protons accumulate leading to myocardial tissue acidosis. Accumulation of lactate can kead to accumulation sodium and calcium so more ATP is needed for homeostasis. This redirection of ATP from contraction to ion homeostasis decreases cardiac efficiency.
+futile cycles

Question 19

Write a short note of futile cycles.

Answer 19

• CAUSED BY increased fatty acids decreasing cardiac efficiency by
• Activation of fatty acids to long chain acul CoA forming TAG uses ATP
• Increasing uncoupling proteins activity
• High fatty acids activate sarcolemal calcium channels, so more ATP is needed for homeostasis.

Question 20

Mention the role of metabolic agents in heart disease & give an example

Answer 20

Inhibits fatty acid oxidation partly and stimulate glucose and lactate oxidation which can improve cardiac efficiency and cardiac function in ischemic heart failure.
Trimerazidine in angina pectoris