Regulation of Adipocyte Lipolysis Catecholamines –Epinephrine & Norepinephrine Beta Adrenergic...
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Transcript of Regulation of Adipocyte Lipolysis Catecholamines –Epinephrine & Norepinephrine Beta Adrenergic...
![Page 1: Regulation of Adipocyte Lipolysis Catecholamines –Epinephrine & Norepinephrine Beta Adrenergic Receptors –Stimulate Alpha Adrenergic Receptors –Inhibit.](https://reader033.fdocuments.us/reader033/viewer/2022061601/5515528f55034673228b653d/html5/thumbnails/1.jpg)
Regulation of Adipocyte Lipolysis
• Catecholamines– Epinephrine & Norepinephrine
• Beta Adrenergic Receptors– Stimulate
• Alpha Adrenergic Receptors– Inhibit
• Insulin– Inhibitory
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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
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•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
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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
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Insulin
Lipoprotein Lipase (LPL)
Phosphatidylinositol 3-Kinase (PI3K)
Phosphodiesterase-3
Degrades
cAMP
Hydrolyzes
Plasma Triglycerides
Into
FFA
Phosphorylates
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Insulin & LPL
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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