Lecture 30 - Metabolic reprogramming of skeletal muscle stem-cells

Question 1

True or False

In quiscent SCs you wont see the volume of mitochondria and the complexity of the network as opposed to active SCs

Answer 1

true

Question 2

Glycolysis produces intermediates which can be used for what?

what cycle is it?

Answer 2

New biomass for proliferating cells

Pentose cycle:

• producing nucleotides for DNA
• producing phospholipids (essential for membranes)
• AAs - serine, glycine, cysteine

Question 3

There were approx 3000 genes that were heavily enriched in quiescent satellite cells. meaning upon activation of Satellite cells they were turned off or downregulated. what would these genes be responsible for?

what else has been found in activated SCs?

Answer 3

FA metabolism!. as well as cell adhesion and homeostatic processes

3000 genes that were upregulated in activated SCs. these were needed for:
- glucose metabolism!
-cell proliferation
cell cycle progression

Question 4

Is glycolysis happening in the quiescent state?

Answer 4

yes, but at very low/basal levels.

once active there is a huge increase - most being used to support the generation of new biomass

Question 5

histone acetylation does what for transcription?

Answer 5

increases transcription

Question 6

H4K16ac is an indicator of …

Answer 6

an activated satellite cell

Question 7

true or False

SirT1 requires NAD to work

Answer 7

true

deacetylates histones = represses transcription

Question 8

Does the total amount of SirT1 derease with satellite cell activation?

Answer 8

No.

doesn’t explain the increase in histone acetylation.

But NAD is required. and NAD levels are regulated through metabolism

Question 9

What happens to NAD levels from quiescent –> activated?

why?

Answer 9

NAD+ levels decrease

due to a rapid increase in glycolysis

this directly links the change in metabolism with the histone deaceylation

Question 10

describe the state of quiescent and activated SCs with respect to metabolism, NAD levels and SIRT1 activity

Answer 10

Quiescent
FA oxidation/oxphos
high NAD+
High SIRt1 activity
= transcriptional repression

Activated
Glycolysis
low NAD+
Low SIRT1 activity
= transcriptional activation

Question 11

true or false

The majority of proliferating SCs are MyoD+ and committed to the myogenic lineage

proliferating SCs are highly glycolytic

Answer 11

true

raises the question of whether they can be ‘‘pushed back’’ to a stem-like state by altering metabolism

Question 12

How can we test whether we can induce metabolic reprogramming?

Answer 12

culture media for proliferating cells

1. control = glucose
2. low glucose
3. galactose (becomes energy neutral as it requires ATP to break down - this forces the cell into oxphos using pyruvate)

then measure cellular metabolism and genetic profile

Question 13

True or false

Glycolysis is increased in cells cultured in galactose

Answer 13

False

it is reduced.

forcing the cell to use oxphos

Question 14

true or false

inhibiting glycolysis with galactose decreases myogenic specification

Answer 14

true

Question 15

what is TXNIP?

Answer 15

an essential regulator of glycolysis

acts by inhibiting glucose uptake and conversion to glucose-6-phosphate (first step of glycolytic pathway)

Question 16

overexpression of TXNIP leads to what?

Answer 16

inhibition of glycolysis

complete stop of cell cycle and proliferation

decline in the expression of MyoD - pushes away from myogenic commitment

Question 17

G(0) cell state is referring to..

Answer 17

quiescence (reversible G0)

but there is also:

differentiation (irreversible G0)

Senescence (irreversible G0) - happens with age

Question 18

PKM1 does what?

Answer 18

Pryuvate kinase 1 - promotes movement of phosphoenolpyruvate (PEP) into pyruvate

Question 19

high levels of PKM1 is associated with increased reliance on..

Answer 19

oxphos

Question 20

PKM2 has a much ____ afinity for PEP

Answer 20

PKM2 has a much lower afinity for PEP

allows for the build up of PEP and the upstream intermediates

remember these are neccessary for the generation of new biomass

Question 21

PKM1 will have high levels in _____ cell population

PKM2 will have high levels in _____ cell populations

Answer 21

PKM1 will have high levels in quiscent cell population

PKM2 will have high levels in activated cell populations

Question 22

The difference between PKM1 and PKM2 is…

Answer 22

one exon

and quiescent cells have more of the PKM1 exon expressed

Question 23

true or false

overexpression of PKM2 in proliferating SCs blocks the production of lactate and decreases the rate of cell proliferation

Answer 23

false

overexpression of PKM2 in proliferating SCs blocks the production of lactate, but increases the rate of cell proliferation

Question 24

true or false

it is possible to reprogram previously commited/specified myogenic cells through targeted changes in metabolism

Answer 24

true