1. Regulation of Adipocyte Lipolysis
Catecholamines
Epinephrine & Norepinephrine
Beta Adrenergic Receptors
Stimulate
Alpha Adrenergic Receptors
Inhibit
Insulin
Inhibitory

2. Catecholamines Stimulatory Inhibitory B-Adrenergic Receptors
Activates Stimulatory G-Protein
Activates Adenylate Cyclase
Generates cAMP
Activates cAMP-dependent protein kinase
Phosphorylates HSL & Perilipins
Break down triglycerides
Inhibitory
A-Adrenergic Receptors
Activates Inhibitory G-protein
Inhibits Adenylate Cyclase

3. Catecholamines stimulate HSL to break down triglycerides to fatty acids and glycerol
Fatty acids and glycerol are released into the blood and circulated to other body tissues

4. ATGL Adipose Triglyceride Lipase
Enzyme that may be responsible for catalyzing the initial steps of triglyceride hydrolysis.
Zimmermann et al. (2004)
HSL knock-out mice showed an accumulation of diglycerides, suggesting that additional lipases may be present that can hydrolyze the first ester bond of triglycerides
Still controversial

5. Lipoprotein Lipase (LPL) Phosphatidylinositol 3-Kinase (PI3K)
Insulin
Lipoprotein Lipase (LPL)
Phosphatidylinositol 3-Kinase (PI3K)
Hydrolyzes
Phosphorylates
Plasma Triglycerides
Phosphodiesterase-3
Degrades
Into
cAMP
FFA

6. Insulin & LPL

7. PI3K
Insulin
Phosphorylates
LPL
Hydrolyzes triglycerides in the blood to increase FFA levels
PI3K
Inhibits lipolysis in adipose cells
Mediates insulin-stimulated glucose uptake
Phosphodiestesterase-3
Degrades