What regulates ketone body synthesis?

The main regulator for ketone body synthesis is fatty acid availability. During periods that cause fatty acid concentration in the blood to be high, malonyl CoA concentration in the liver is low due to acetyl CoA carboxylase being in the phosphorylated state. Fatty acyl CoA is then able to freely enter the mitochondria as there is no inhibition of CAT I, and beta-oxidation occurs at a rapid rate. The subsequent high mitochondrial content of acetyl CoA causes active ketone body synthesis. HMG CoA synthase also plays a vital role in ketone body synthesis, as it is the rate-limiting step. HMG CoA regulation has a positive correlation with glucagon and is negatively regulated by insulin.