Lecture 7 Flashcards
What is the lactate threshold?
Increased power output increases the lactate released. At a certain power output the lactate produced increases dramatically and begins to accumulate in the bloodstream. This is the lactate threshold
What happens below the lactate threshold to lactate production?
Below the lactate threshold the amount of lactate produced levels off.
What factors affect lactate production in muscles?
Rate of pyruvate formation and oxidation
Blood levels determined by rate of lactate production and clearance
Higher muscle oxidative capacity increases lactate threshold
LDH isoenzymes
O2 supply to muscles
Adrenaline levels
Muscle glycogen
What is a possible consequence of reduced splanchnic blood flow during exercise?
Clearance of lactate can often be prevented by decreased splanchnic blood flow
How does the type of LDH affect the amount of lactate produced?
Some LDH isozymes have a greater affinity for lactate and others for pyruvate. This affects blood lactate levels.
How does oxygen in muscles affect lactate production?
Less oxygen in muscles causes increase in lactate production
How does adrenaline affect lactate production during exercise?
More adrenaline causes more production of lactate during exercise.
How do high levels of glycogen affect lactate production during exercise?
Higher glycogen levels in muscles causes more lactate production during exercise
How does training affect lactate levels at a given power output?
Training decreases lactate production at a given power output
What is the function of MCT1?
MCT 1 facilitates lactate uptake
What is the function of MCT4?
MCT 4 facilitates lactate release
How does training affect lactate transporter expression?
After training there’s more MCT-1 and increased muscle oxidative capacity this lactate is oxidised
Where in the body do FFA come from?
FFAs are derived from adipose tissue and muscle triglycerides
How do muscles take up FFA
Muscles take up FFA via simple and facilitated diffusion.
What are the major determinants of fat oxidation?
FFA availability, transport capacity and muscle oxidative capacity are the major determinants of fat oxidation.
How does training change fat metabolism?
Training increases the amount of lipid oxidised and decreases carbohydrate oxidation.
How do fatty acids generate energy?
Fatty acids can be oxidised. They cannot produce energy in humans in any other way.
What happens to glycerol during lipid metabolism?
Glycerol is released into the bloodstream and converted to glucose by the liver via gluconeogenesis.
What happens to fat absorbed from the gut when exercising right after a fatty meal?
Fat is absorbed from the gut as chylomicrons and LDL. Muscles have LDL lipase which allows them to utilize fat consumed in a fatty meal.
What generates more power; carbohydrate metabolism or fatty acid oxidation?
Carbohydrate oxidation generates more power than fatty acid oxidation
What happens when FA mobilization from adipose tissue decreases?
When fatty acid mobilization from adipose tissue is decreased the muscles rely more on triglyerides found in muscle tissue.
Where can ATGL be found?
Adipose tissue TriGlyceride Lipase is present in both adipose tissue and muscles
What is the function of ATGL?
ATGL breaks down fatty acid in triglyceride leaving a diglyceride
What is the function of HSL?
HSL breaks down diglycerides
What is the consequence of the ability of ATGL and HSL to be phosphorylated?
ATGL and HSL can be regulated
What factors regulate adipose tissue lipolysis?
ATGL and HSL Beta-adrenergic stimulation Low insulin levels Adipose tissue blood flow FFA/albumin ratio Blood glucose and lactate Caffeine
What happens to plasma FFA after exercise?
Plasma FFA stay at elevated levels when exercise is over and fatty acid breakdown continues into the resting period
What is the effect of high blood glucose and lactate on fat metabolism?
high blood glucose and lactate levels inhibit lipolysis
What effect does caffeine have on fatty acid mobilization?
caffeine increases mobilization of fatty acids and their use in exercise.
What factors regulate intramuscular lipolysis?
ATGL and HSL beta adrenergic stimulation ERK (responds to Ca2+) AMPK inhibits HSL activation Blood glucose Plasma FFA availability
What are the determinants of muscle FA uptake?
Arterial plasma FA Ability of muscle to oxidise fats FA transporters (FABP, CD36, FATP) Carnitine, CPT activity Beta oxidative capacity (HAD, mitochondria)
What is the function of HAD in mitochondria?
HAD in the mitochondria is part of the first step of beta oxidation
How are fatty acids transported across the plasma membrane?
Transport of fatty acids across the plasma membrane uses transport proteins
How do fatty acids get across the mitochondrial membrane?
Fatty acids get across mitochondrial membrane via CPT1 protein with the help of carnitine. Acetyl carnitine changes CPT2 back into CPT1.
Why do carnitine levels drop and acetyl carnitine levels rise during high intensity exercise?
Carnitine can act as a buffer for increase in glycolytic rate. This causes increase in acetyl-carnitine.
How does HAD affect lipid metabolism?
The more HAD in the muscle the more fat oxidation. Exercise increases HAD concentration.
Why is FA oxidation reduced with increasing exercise intensity?
Reduced plasma FA availability
Increase in glycolysis inhibits CPT activity due to carnitine acting as a buffer within the cell.
Interesting Fact
Oxidation of carbohydrates require less O2 to make ATP
Why are medium chained fatty acids different to other fatty acids?
Medium chained fatty acids don’t need CPT to get into the mitochondria.
How does training affect fatty acid uptake and oxidation?
trained athletes have greater fatty acid uptake and oxidation using both fatty acids from blood and intramuscular triglyerides.
Muscle CPT levels are increased after training.
