Mobilisation from adipocytes

High starch containing food

Result in high blood glucose concentration. These promote glycolysis, glycogenesis, FA and other lipid synthesis. FA oxidation and glucogenesis are inhibited- including mobilization from adipocytes.

Under stress conditions

Reduced glucose levels and low insulin, glucagon and adrenaline (epinephrine) are elevated.

Decrease: glycolysis, glycogenesis, fatty acid synthesis, lipid synthesis.

Increase: fatty acid oxidation, gluconeogenesis, mobilization of fats

Cyclic-AMP mediated cascade system

Highly influenced by hormones: epinephrine, cortisol and growth hormone. Inhibited by insulin. These alter the activity of hormone sensitive lipase (hydrolysis of TAGs from the lipid droplets to release the free fatty acids and glycerol into circulation). The activity of of the hormone sensitive lipase activity is increased by phosphorylation.

Epinephrine

Increases cAMP production which in turn increases phosphorylation of the enzyme, and therefore increases the activity of the enzyme. Insulin inhibits triacylglycerol breakdown by increasing the activity of a protein phosphatase that reverses the cAMP dependent phosphorylation of the hormone sensitive lipase. Insulin also decreases cAMP levels and decreases hormone sensitive lipase gene transcription.

Glycerol oxidation

Only 5% of total energy contributed by glycerol.