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Regulation of Adipocyte Lipolysis

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

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Regulation of Adipocyte Lipolysis

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

  2. 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

  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 forcatalyzing 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. 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

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