6+7. integrative metabolism lipids Flashcards Preview

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Flashcards in 6+7. integrative metabolism lipids Deck (22):
1

fat utilization during type of exercise

- decrease with intensity
- increase with duration

2

fat form in adipose and muscle

triacylglycerol (TAG)
triglyceride (TG)

3

blood fat in what forms
- where from

- albumin-free fatty acids (FFA or FA - from adipose)
- chylomicrons (intestinal derived)
- VLDL (liver)

4

advantages of fat as fuel

- more energy/gram
- more storage (~120h of marathon running)
- dont need to consume before or after

5

disadvantages of fat as fuel

- ~65VO2 max is max intensity sustained fat exclusively
- fatty acids must be bound
- cant be used anaerobically

6

potential limiting factors for fatty acid use

1. mobilization FFA from adipose
2. FFA uptake by muscle (transport across sarcolemma)
3. mitochondrial membrane transport
4. fat oxidation

7

role of insulin in fat metabolism

inhibits hormone sensitive lipase (HSL)

result
- reduces intracellular lipolysis of TG
- promotes TAG storage in adipocyte

8

role of EPI in FFA mobilization

binds membrane receptor (adenylate cyclase)
- cAMP produced
- activates (phosphorylates protein kinase A
- moves "perilipin" coating on lipid droplet
- allows hormone sensitive lipase (HSL) to bind
- TAG converted to FFAs

9

perilipins

proteins coating on lipid droplets that prevents HSL from binding
- removed by phosphorylated protein kinase A

10

affects of exercise on adipose tissue lipolysis

increased HSL amount and sensitivity to stim by EPI (5 or 20 min)
- levels vary depending on fat deposit

11

FFA release from adipose tissue during high intensity
- rate limiting step?

impaired
- reduced blood flow to adipose tissue
- not enough albumin reaches adipocyte for transport
- FAs must be bound in blood

*limiting step
- infused FA into blood improves fat oxidation at high intensities

12

FFA uptake into skeletal muscle and usage

FFA freely crosses membrane into cytosol
- converted to "fatty acyl CoA"
- crosses into mitochondria
- beta oxidation
- acetyl CoA
- citric acid cycle

13

exercise and lipoprotein lipase (LPL) concentration in skeletal muscle

increased
- higher post 8h
- even higher post 22h
ensures increased flux of fatty acids to contracting muscle

14

FA sacrolemmal transporters in muscle

FAT/CD36
- fatty acid translocase
- most important **

FABPpm
- fatty acid binding protein (plasma membrane)
- peripheral protein
- doesnt span the membrane

FATP1-6
- family of fatty acid transporters

15

ACS1

plasma membrane acyl-CoA synthetase
- FA to acyl-CoA

16

how FA enters muscle
- 5 ways

1. FA into cell simple diffusion

2. CD36 alone / with FABPpm increase local conc, and increase diffusion

3. CD36 active transport, binds FAs to FABPc before entering pathways

4. some transported by FA transport proteins, rapidly activated by acyl-CoA synthatse --> aceyl CoA esters

5. very long chain FAs transported by FATPs, converted to VLC-acyl-CoA

17

how FA receptors stimulated to move to plasma membrane

same as glucose
- glut4 and FAT/CD36

insulin
- PI3-k pathway
muscle contraction
- AMPK pathway

*additive effect

18

FA entry into mitochondria

- FA activated by acyl CoA synthetase
- FA acyl CoA
- Carnitine pamitoyl transferase 1 (CPT1)
- fatty acyl carnitine
now can cross into mitochondria

*CPT1 rate limiting step
- found FAT/CD36 on mitochondria membrane (significance still unclear)

19

AMPK regulation of fat metabolism

activates
- malonyl CoA decarboxylase (MCD)
- malonyl CoA --> acetyl CoA

inactivates
- acetyl-CoA carboxylase (ACC)
- acetyl CoA --/--> malonyl CoA

*malonyl CoA inhibits CPT1
AMPK decrease malonyl CoA --> increases CPT1 --> increase FA oxidation

20

enzymes increased in concentration with training to improve FA oxidation

beta hydroxyacyl dehydrogenase (betaHAD)
- beta oxidation

citrate synthase (CS)
- krebs cycle

cytochrome oxidase
- etc cycle

CPT1
- makes fatty acyl carnitine in cytosol

* classical markers for training status

21

what happens to plasma FFA with aerobic training

return to baseline levels quicker
- lower levels in blood
- more dependency on intramuscular TGs
- more FA transporters (FAT/CD36***)

22

high IMTG seen in obese, why also seen in trained

skeletal muscle remains insulin sensitive