regulation of adipocyte lipolysis
DESCRIPTION
Regulation of Adipocyte Lipolysis. Catecholamines Epinephrine & Norepinephrine Beta Adrenergic Receptors Stimulate Alpha Adrenergic Receptors Inhibit Insulin Inhibitory. Catecholamines. Stimulatory B-Adrenergic Receptors Activates Stimulatory G-Protein Activates Adenylate Cyclase - PowerPoint PPT PresentationTRANSCRIPT
Regulation of Adipocyte Lipolysis
• Catecholamines– Epinephrine & Norepinephrine
• Beta Adrenergic Receptors– Stimulate
• Alpha Adrenergic Receptors– Inhibit
• Insulin– Inhibitory
Catecholamines
• Stimulatory– 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
•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
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
Insulin
Lipoprotein Lipase (LPL)
Phosphatidylinositol 3-Kinase (PI3K)
Phosphodiesterase-3
Degrades
cAMP
Hydrolyzes
Plasma Triglycerides
Into
FFA
Phosphorylates
Insulin & LPL
Insulin
• LPL– Hydrolyzes
triglycerides in the blood to increase FFA levels
• PI3K– Inhibits lipolysis in
adipose cells– Mediates insulin-
stimulated glucose uptake
PI3K
Phosphodiestesterase-3
Phosphorylates
Degrades