Regulation of Lipid Metabolism Lecture Notes PDF

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Human Metabolism

Regulation of Lipid Metabolism: 

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Fatty acid oxidation o Regulated by concentrations of fatty acid concentration in the blood  This is controlled by hydrolysis rate of triacylglycerol’s in adipose tissue by hormone-sensitive triacylglycerol lipase  This enzyme is susceptible to change from cAMP levels o Glucagon, norepinephrine and epinephrine increase adipose tissue cAMP levels  cAMP activates PKA – phosphorylation of certain enzymes o This activates hormone sensitive lipase  Stimulating lipolysis in adipose tissue  Raising blood fatty acid levels o Stimulating beta oxidation o PKA inactivates Acetyl-CoA carboxylase  cAMP dependent phosphorylation simultaneously stimulates fatty acid oxidation and inhibits fatty acid synthesis Insulin o Pancreatic hormone o Released in response to high glucose levels o Stimulates formation of glycogen and triacylglycerol’s o Decreased cAMP levels  Leading to dephosphorylating of hormone sensitive lipase  Inactivating them o Reducing fatty acid availability for oxidation o Activates acetyl-CoA carboxylase Glucagon o Released in response to low glucose levels o Increases cAMP levels  Leading to phosphorylation of hormone sensitive lipases  Activating them o Increasing fatty acid availability for oxidation Carnitine palmitoyl transferase I o Inhibited by malonyl-CoA o Keeps newly synthesised fatty acids out of the mitochondria  Away from beta oxidation AMPK o Phosphorylates ACC  Inactivating it o Activated by AMP o Inhibited by ATP  ATP levels – high

Human Metabolism

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Kinase inhibited  ACC dephosphorylates – activating it  Stimulating malonyl-CoA production for fatty acid synthesis in adipose tissue

Figure 1: Lipid Metabolism in the Liver

Figure 2: Lipid Metabolism in Adipocytes...