Fat Flashcards
What is the structure of a fatty acid?
Hydrocarbon chain
Carboxyl group
How is a triglyceride formed?
Fatty acid bonds covalently with a glycerol element
What type of reaction occurs to join a fatty acid with glycerol?
Esterification reaction
How are fatty acids mobilised for oxidation?
In the tissue and muscle, hormone-sensitive lipase is sensitive to alterations in adrenaline, which activate and liberate fatty acids
In the blood, lipoprotein lipase in capillary walls can be activated and liberate fatty acids
Fatty acids are transported in the blood to the muscle to be used by mitochondria to produce ATP and CO2
GLycerol can be kept to create more TAG or transferred to the liver
How are fatty acids transported into the mitochondria?
Fatty acids move from the vascular space into the interstitial space via diffusion
Fatty acids move from the interstitial space into the sarcolemma via CD36
Binds to binding protein by muscle fatty acid-binding proteins (FABPc)
Fatty acids combine with CoA to form fatty-acyl-CoA via the action of acyl-CoA synthase
Fatty-acyl-CoA moves across the outer mitochondrial membrane via CPT1 whereby it combines with carnitine to from acyl-carnitine
Acyl-carnitine move across the inner mitochondrial membrane via CPT1 whereby it combines with CoA to form fatty-acyl-CoA
How are fatty acids transported in the blood?
Bound to albumin
By what process are fatty acids oxidised?
Fatty-acyl-CoA via B oxidation leads to acetyl-CoA (precursor to TCA cycle)
What protein converts pyruvate to acetyl-CoA?
Pyruvate dehydrogenase complex
The effect of exercise on substrate oxidation?
We change substrate oxidation dependent on exercise intensity
Fat oxidation predominates at ar lower exercise intensities and rest
As intensity increases, CHO contribution begins to predominate
What exercise intensity does fat oxidation predominate carbohydrate oxidation?
Lower exercise intensity
Rest
60-65%
What is the consequence of fat oxidation?
High muscle glycogen utilisation
Limited muscle glycogen stores
Fatigue
Why is fat oxidation limited at high exercise intensities?
Slow mobilisation of fatty acids from adipose tissue/skeletal muscle
Transport of fatty acids into the muscle cell
Transport of fatty acid into the membrane
Oxidation of fatty acids in B-oxidation
What can slow mobilisation of fatty acids from adipose tissue/skeletal muscle to limit fat oxidation at high exercise intensities?
Limitation of hormone-sensitive lipase
Reduced blood flow
What can limit the transport of fatty acids into the muscle cell that limit fat oxidation at high exercise intensities?
Reductions in CD36 translocation to the membrane
What limits the transport of fatty acid across the membrane that will limit fat oxidation at high exercise intensities?
CPT1
Carnitine availability
What are the adaptations to fat oxidation from training? (Talanian et al. 2017; Tunstall et al. 2002)
The shift from CHO oxidation to fat oxidation
Talanian et al. 2017 - in pre-trained state fat oxidation increases over-exercise, but training elevates fat oxidation at all time points
Tunstall et al. 2002 - post-training fat oxidation is increased
How are fatty acids converted to ketones?
Via acetyl CoA
What are the two main ketones used for energy-transport into tissues?
Acetoacetate
B-hydroxybuterate
Define ketosis?
Serum (ketone) 1-3mmol/l
Low insulin and glucose
What fuel does the brain predominantly rely on?
Glucose
How do ketones reach the brain and what are they used for?
Ketones can cross the blood-brain barrier and used as a fuel source
What ketone cannot be converted back into acetyl CoA?
Acetone
Overview of low carbohydrate, high-fat diets for exercise performance?
Increase fat oxidation during exercise
This metabolic adaption occurs;
- in as little as 5 days
- even when muscle glycogen is restored and CHO is available
No performance benefit and performance of high-intensity exercise may be impaired
Why is it that despite sparing muscle glycogen we do not observe an increase in exercise performance with a high-fat diet?
Using fat is less economical
The Randle Cycle
Transcriptional regulation
