Mobilisation of fatty acids from adipocytes

Fate of lipase action products

1. Glycerol backbone: Glyceraldehyde -3-phosphate

2. Fatty acid tails: B-oxidation

High blood glucose

High starch containing foods, high insulin hormone concentration.

These promote: glycolysis, glycogenesis, fatty acid synthesis and other lipid synthesis.

Inhibit: Fatty acid oxidation, gluconeogenesis and mobilisation of fats.

Under stress conditions

Reduced levels of glucose and insulin. Glucagon and epinephrine are elevated.

Promotion: Fatty acid oxidation. Gluconeogenesis. Mobilisation of fats.

Inhibition: Glycolysis. Glycogenesis. Fatty acid synthesis and Lipid biosynthesis.

Cyclic-AMP mediated cascade system

Highly influenced by hormones; three major stimulators (epinephrine, cortisol and growth hormone), one major inhibitor (insulin). These alter the activity of hormone sensitive lipase: hydrolysis of triglycerides from the lipid droplets to release fatty acids and glycerol into circulation. The activity 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 hormone sensitive lipase.

Insulin

Inhibits triacylglycerol breakdown by increasing the activity of a protein phosphatase that reverses the cAMP dependent phosphorylation of the hormone sensitive lipase.

Also decreases cAMP levels and decreases hormone sensitive lipase gene transcription.

Glycerol oxidation

Only 5% of total energy contributed by glycerol.