Lecture 7 - Lipid metabolism during exercise

Question 1

Pyruvate can also turn into ____

Answer 1

Lactate

Question 2

As you increase the power output, the concentration of lactate in the blood willl…

Answer 2

increase slowly and then at higher intensities will increase quite dramatically

Question 3

What happens if you exercise above and below the lactate threshold?

Answer 3

Below: blood lactate will level off, any decrease slightly

Above: continuous rise in lactate

Question 4

Lactate is produced even below the…

Answer 4

maximum oxygen uptake

I.e the hypoxia is not the reason pryuvate is forced down the path towards lactate

Question 5

The production of lactate is determined by the

Answer 5

Balance between the rates of pyruvate formation and the rates of pyruvate oxidation (of course there are factors that affect both of these)

Question 6

List the factors involved in the regulation of lactate metabolism during exercise:

Answer 6

Production determined by balance between rates of pyruvate formation and oxidation

Blood levels determined by rates of lactate production and clearance

Muscle oxidative capacity

LDH isoenzymes favours the production of lactate (more = more lactate for a given amount of pyruvate)

o(2) supply to contracting muscle - If you hold your breath and exercise you’ll produce more lactate

Adrenaline - increases the rate of glycogen breakdown - will see more lactate

Muscle [glycogen] - more glycogen broken down = more lactate

Question 7

The lactate threshold is used as a measure in sports science because…

Answer 7

provides a measure of the muscle oxidative capacity without having to take a muscle biopsy and measure the mitochondria

Question 8

Following a period of training, what will be the effect on lactate?

Answer 8

low blood and muscle levels - one of the hallmarks of training

Question 9

Fats can only be oxidised meaning their metabolism is only…..

Answer 9

aerobic

Question 10

The power output from fat oxidation is lower than…

Answer 10

the output from carbohydrate oxidation

Question 11

After exercise and training, if you have a fatty meal you’re better able to …

Answer 11

remove triglycerides from the bloodstream as they go into the muscle

Here they are more likely to be oxidized so that’s why it is a good way to regulate fat mass

Question 12

Lipolysis is usually measured from the appearance of..

Answer 12

glycerol

Question 13

There is a reciprocal relationship between FAs from adipose tissue and

Answer 13

FAs from muscle - When you prevent the FAs release from

Question 14

What does the hormone sensitive lipase (HSL) do?

Answer 14

breaks down triglycerides

sensitive to hormones that mobilise glycerol

Question 15

monoglyeride (MGL) lipase…

Answer 15

breaks down FA and cleaes off glycerol

Question 16

What is responsible fot he regulation of adipose tissue lipolysis during exercise?

Answer 16

It is mediated by apipose triglyceride lipase (ATGL) and hormone sensitive lipase (HSL)

Beta-adrenergi stimulation

decease in insulin - an anabolic hormone

adipose tissue blood flow - during exercise this is reduced, so less enters the blood stream

FFA/albumin ratio - albumin is the most abundadnt plasma protein which has binding sites for FAs

Blood (glucose) and lactate - decreases lipolysis

Caffeine - probably acting via adrenaline - mobilise FAs.

Question 17

How is lipolysis regulated with the muscle?

Answer 17

mediated by adipose triglyceride lipase (ATGL) and hormone sensitive lipase (HSL)

B-adrenergic stimulation (via PKA) - Adrenaline

ERK (activated by Ca2+) - another kinase

AMPK inhibits HSL activation - AMPK promotes energy breakdown (a bit counter-inituitive, reason not known)

Blood (glucose)

plasma FFA availability

Question 18

What are the determinants of muscle FA uptake?

Answer 18

Arterial plasma (FAs)

Ability of muscle to oxidise FAs - maintain lower intracellular conc. and maintain diffusion gradient

FA transporter (FABP,CD36, FATP)

Carnitine (helps get them across the mitochondrial membrane), CPT activity

Beta-oxidative capacity (HAD: an ezyme involved in the first step in Mitochondria breakdown of FA) - more mitochrondria, more breakdown

Question 19

What are the means of msucle FA uptake?

Answer 19

1- simple diffusion

2 CD36 and FABP act to enhance local (FA) for diffusion

3. CD36 and FABP facilitate FA uptake
4. FA uptake via FATP
5. Long chain FA uptake via FATP

Question 20

Carnitine can act to…

Answer 20

facilitate FA uptake into the mitochondria

a credible “fat”drug

Question 21

carnitine can act as a buffer for an increase in

Answer 21

glycolytic rate (exercise intensity)

Question 22

The more HAD you have in the muscle, the greater your

Answer 22

FAT oxidation - will burn more fat

Therefore when you exercise more = increase in mitochondria - increase in HAD = will burn more fat over a day

Question 23

Which intensity is there maximum fat oxidation?

Answer 23

25% Vo2MAX

Question 24

Why is FA oxidation reduced with increasing exercise intensity?

Answer 24

reduced plasma FA availability

Increased glycolytic flux inhibits CPT activity and mitochondrial FA uptake (malonyl-CoA?, pH)

Reduced carinitine availabilty

(oxidation of CHO requires less O2 for given ATP production)

Question 25

Medium chain Triglycerides don’t need ____ to get in to the mitochondria

Answer 25

CPT - can be oxidised easier

Question 26

from 40-80% VOC2 peak, what happens to long chain, and medium chain triglycerides?

Answer 26

long chain - goes down

medium chain - doesn’t change (will be added to sports supplements)

Question 27

How does training effect lipid metabolism

Answer 27

trainsed has a greater FA uptake and oxidation (muscle uses more triglyceride)

Trained muscle has a greater capacity for fat oxidation, using FAs from blood and FAs from muscle triglyercides (the latter to a greater extent)

Question 28

What is the adaptation to trained muscle which makes FA oxidation better?

Answer 28

Increase the amountof CPT and the abililty of FAs transported into the mitochondria