W3 - Fat metabolism

Question 1

What is LDL associated with?

Answer 1

⬆️ risk of heart disease

Question 2

What are each ends of the FA called?

Answer 2

Omega

Carboxyl

Question 3

How might adipose tissue turnover decline?

Answer 3

If health status declines

i.e athletes have a very high turnover rate

Question 4

What cytokines does adipose tissue secrete?

Answer 4

Inflammatory cytokines

Question 5

When are lipids insoluble?

Answer 5

In aqueous solutions

i.e blood

Question 6

How is fat transported in the blood?

Answer 6

In chylomicrons or lipoproteins

Question 7

FAs oxidised in the mitochondria of skeletal muscle during exercise are derived from 2 main sources. What are these?

Answer 7

Adipose tissue

Muscle TAG (delivered in chylomicrons + VLDL).

(Plasma TAG may also be used).

Question 8

TAG in adipose tissue is split into FA + glycerol. What happens to these?

Answer 8

Glycerol is released into circulation w/ some of the FAs,

Small & of FAs are NOT released into circulation but used to form new TAF in the adipose tissue = Reesterification.

Question 9

What happens to the FAs that have been released from adipose tissue?

Answer 9

Transported to other tissues + can be uptake by skeletal muscle during exercise.

Question 10

What happens to the glycerol released from the adipose tissue?

Answer 10

Transported to liver

• Acts as a gluconeogenic substrate to form glucose.

Question 11

What can circulating TAG i.e VLDL do temporarily?

Answer 11

Bind to LPL to allow FAs to be split off so that they can be taken up by muscle.

Question 12

What are IMTG split by?

Answer 12

HSL

Question 13

What are the steps that could limit fat oxidation

Answer 13

Lipolysis

Removal of FA from fat cell

Transport of fat by bloodstream

Transport of FAs into muscle cell

Transport of FAs into mitochondria

Oxidation of FAs in b-oxidation pathway + TCA cycle

Question 14

Where are most FAs stores as?

Answer 14

TAG in subcutaneous adipose tissue.

These must be mobilised + transported to the site of oxidation.

Question 15

What do adipocytes contain?

Answer 15

Lipases that breaks down TAG

Question 16

What does the SNN stimulate HSL to do?

Answer 16

Split TAG into FAs + glycerol.

Question 17

What does the conversion of the inactive form of HSL to the active form depend on?

Answer 17

SNN + circulating epinephrine.

Question 18

Where is norepinephrine release from in the SNN?

Answer 18

It’s nerve endings

Question 19

What is often used as a measure of lipolysis?

Answer 19

Measurement of glycerol in the blood

Question 20

What % of FAs are reesterified in lipolysis at rest?

Answer 20

~70%

Question 21

What happens to reesterification during exercise?

Answer 21

Suppressed to incr availability of FAs in adipocyte.

Question 22

What stimulates lipolysis during exercise?

Answer 22

Catecholamines released from the adrenal gland

Question 23

What does reesterification depend on?

Answer 23

Rate at which FA are removed from the adipocyte by the blood

Rate of G-3-P prod

Activity of TAG synthesising enzymes

Question 24

What does the removal of FAs from adipocyte into the bloodstream depend on?

Answer 24

Blood flow to adipose tissue

Albumin conc in blood

No. of free binding sites for FAs on albumin

Question 25

What is the most abundant protein in plasma?

Answer 25

Albumin - Acts as a carrier protein transporting FAs

Question 26

What happens when albumin arrives at target tissue?

Answer 26

Binds to specific ABPs Binding to this aids the release of FAs from albumin + their uptake.

Question 27

What does LPL in the vascular wall do?

Answer 27

Hydrolyses some TAG in circulating lipoproteins passing through the capillary bed. == FA are released, muscle takes them up to use for oxidation.

Question 28

FA uptake from plasma lipoprotein TAG

Answer 28

Happens slowly Accounts for less than 3% of the energy expenditure during prolonged exercise.

Question 29

What transport proteins are found in the sarcolemma/

Answer 29

FABPpm protein FAT/CD36 protein

Question 30

What does muscle contraction do to plasma membrane FAT/CD36?

Answer 30

Increases it = incr. FA transport into cells.

Question 31

What are FAs bound to in the sarcoplasm?

Answer 31

FA-binding protein (FABPc). -- Thought to be responsible for the transport of FAs from sarcolemma to mitochondria.

Question 32

Which muscle fibres have a higher content of IMTG?

Answer 32

Type 1

Question 33

Muscle contains HSL What is it activated by

Answer 33

b-adrenergic stimulation

Question 34

Muscle contains HSL What is it inhibited by

Answer 34

Insulin

Question 35

What can happen with the FAs liberated from IMTG?

Answer 35

Can be released into blood Reesterified Oxidised w/in muscle

Question 36

What are FAs bound to until transported into mitochondria?

Answer 36

FABPc

Question 37

What can FAs in the cytoplasm be activated by?

Answer 37

ACoA synthetase or thiokinase

Question 38

What is formed once the ACoA synthetase or thiokinase meets with the FAs in the cytoplasm?

Answer 38

Forms ACoA complex

Question 39

FAs in cytoplasm can be activated by ACoA synthetase or thiokinase to form ACoA complex. What happens next with this complex?

Answer 39

Used for synthesis of IMTGs OR Is bound to carnitine under the influence of the CPT1 enzyme.

Question 40

What is the 1st step in transport of FA into the mitochondria?

Answer 40

Bonding of carnitine + activated FA

Question 41

What is released when carnitine binds to FA?

Answer 41

CoA

Question 42

CHO + fat are always oxidised as a mixture What does the prominent fuel used depend on?

Answer 42

Intensity Duration Level of aerobic fitness Diet CHO intake before or during exercise

Question 43

What does the rate of lipolysis in adipose tissue depend on?

Answer 43

Circulating conc of hormones (epinephrine stimulates lipolysis + insulin inhibits lipolysis).

Question 44

When does fat oxidation peak ?

Answer 44

~50-60% vo2 max

Question 45

What does training do to fat oxidation?

Answer 45

Enhances

Question 46

What are the adaptations contributing to stimulation of fat oxidation in trained athletes?

Answer 46

⬆️ mit density + ⬆️ no, of oxidative enzymes in trained muscle ⬆️ capillary density = enhances FA delivery to muscle ⬆️ FABP conc which may facilitate uptake of FAs across sarcolemma ⬆️ CPT conc which facilitates transport of FAs into mitochondria