Week 5: Adipose Lipolysis

Question 1

Adipose response to glucagon

Answer 1

has a glucagon receptor (heterotrimeric receptor Gαs) -> adenylate cyclase -> [cAMP] -> PKA -Pi-> ATGL

Triglyceride -ATGL-> Diglyceride + FA

FA transported by AP2 binding protein to the plasma membrane where it exits the cell via FATP via concentration driven facilitated diffusion

In the blood FA binds to Albumin in the blood

Question 2

ATGL AKA

Answer 2

Adipose Triglyceride Lipase

Question 3

Adipose response to epinephrine

Answer 3

Beta adrenergic receptor (Gαs) adenylate cyclase -> cAMP -> PKA -> further activates further than glucagon

But PKA also -Pi-> HSL

Diglyceride -HSL-> Monosaccharide + FA

Once monosaccharides are available, MGL Cleaves

Disaccharide -MGL-> Monosaccharide + FA

Question 4

HSL AKA

Answer 4

Hormone-sensitive lipase

Question 5

MGL AKA

Answer 5

Monoglyceride lipase

Question 6

MGL regulation

Answer 6

Not regulated

just becomes active when substrate is available

Question 7

What happens to the glycerol when the fatty acids have been removed?

Answer 7

Transported into the blood to the liver and is converted into glycerol-3-phosphate

Glycerol -glyceral kinase-> glycerol-3-phosphate

glycerol-3-phosphate + NAD –> DHAP

DHAP can be added with glyceraldehyde-3-phosphate and generate Fructose-1, 6- bisphosphate which can go into gluconeogenesis (ONLY IN THE LIVER)

Glycerol kinase is not present in adipocytes because glycerol-3-phosphate would be a substrate for the phosphatidic acid pathway and regenerate triglycerides (would be a futile loop in the adipocytes)