9. CHO and Fat Flashcards
What is the cross-over concept of fats and carbs?
the intensity where the contributions of carbs and fat oxidation are equal.
What is the relative contribution of carbs and fat as VO2 (intensity) increases?
When Vo2 is low. Fats are used and this increases to about 65% of max HR. Then begins to decrease.
Carbs contribution is a constant steady increase.
Why does carbohydrate oxidation increase with increasing intensity?
- Energy charge of cell, Ca2+, pH, PCr, NADH etc. regulate glycolysis
- Glycogenolysis requires free phosphate
- Adrenaline + AMP activate glycogen phosphorylase
- AMPK increases GLUT 4 translocation
What are the 3 reasons what fat oxidation increase at moderate intensity but decreases at high intensity?
- Fatty acid release/availability
- Fatty acid uptake into the cell
- Fatty acid uptake into mitochondria
How does fatty acid release/availability contribute to fat oxidation?
Availability is dependent on:
- Fatty acid conc in plasma. - Blood flow to the tissue
At rest - blood flow to muscle is lower than to adipose
At moderate exercises- muscle want more cardiac output
At v high - virtually all carbs to muscles - none to fatty acid stores - no blood to take FA to muscle from stores
Lipolysis can limit fat oxidation
How does fat uptake into the cell regulate fat metabolism. and why is this not a limiting factor?
AMPK levels rise to activate more fat transporters
As exercise intensity rises AMPK levels rise so you’d expect fat use to rise as well so fat uptake isn’t a limiting factor
How does Fatty Acid uptake into the mitochondria regulate fat metabolism?
AMPK is thought to release inhibition of CPT1 caused by malonyl CoA
- Intense exercise activates CHO metabolism, increasing acetyl CoA, increasing malonyl CoA, decreasing CPT1
- Increased acetyl CoA causes increase acetyl carnitine and decreased carnitine
- decreased pH inhibits CPT1.
The FA chains require CPT1 to move across into the mitochondria
What is the effect of elevating plasma FA concentrations
Probably dont remember as much
It stimulates the cardiac autonomic nervous system
what is the role of Heparin?
Breaks LPL off the inside of the capillary so its free. so is more likely to catalyse the TAG to 3FA. Therefore there is a increase FA availability
What is the potential role of malonyl CoA in fatty acid oxidation?
can inhibit the function of CPT1. this is turn causes it to be a suppressor of fatty acid oxidation
What is the role of AMPK in fatty acid oxidation?
regulates the transport of fatty acids into the cell through FAT/CD36
It increases GLUT 4 translocation so more fat is taken up into the call
