KETOGENESIS

What are ‘ketone bodies’?

• acetoacetate (primary ketone body)

• β-hydroxy butyrate (secondary). Can only measured in blood.

• acetone (secondary)

What is the normal level of serum / ketone bodies in the blood?

1mg/dL (0.2 mmol/L)

What is the normal amount of ketone bodies excreted in the urine?

<100 mg/day

What is Ketogenesis? Site of Ketogenesis?

Synthesis of ketone bodies from acetyl CoA.

Site: mitochondria of liver cells

Starting Compound of Ketogenesis?

Acetyl CoA

What is post-absorptive state/fasting?

Metabolic state after the complete absorption, digestion and storage.

In what state does both Ketogenesis and Ketolysis occur in?

In Fasting State

How many ATPs can ketolysis generate?

22 ATPs

What is the condition called when there is a high accumulation of ketone bodies?

Ketoacidosis.

Where are ketone bodies transported?

To extrahepatic tissue, renal cortex, brain and heart muscles so it can be utilized for energy.

Why can’t liver utilize ketone bodies?

It is cuz it lacks the ketolytic enzyme thiophorase.

REACTION PATHWAY OF KETOGENESIS?

• 2 molecules of Acetyl CoA In Beta oxidation is converted to acetoacetyl CoA by the enzyme thiolase (acetyl CoA transferase).

REGULATION OF KETOGENESIS?

• Ketone body formation occurs due to the non availability of carbohydrates in tissues.

• Activator: Glucagon

• Inhibitor: Insulin

• Increase in glucagon/insulin promote ketone body formation due to disturbances in carbohydrate and lipid metabolism.

State 3 levels where Ketone Body Metabolism is regulated?

• Lipolysis - breakdown of triglycerides to fatty acid and glycerol by the enzyme Lipase.

• Entry of fatty acid to mitochondria - Explain the Carnitine Shuttle.

• Oxidation of acetyl CoA: Acetyl CoA is broken down to ketone bodies (undergoes ketogenesis incase of diabetes mellitus) and CO2 (formed in citric cycle)