Ketogenesis mechanisms

There have been reports of other glucagon actions in the liver which can be related to the elevation of cAMP, but whose molecular mechanisms are not well defined. Examples are the stimulations of ketogenesis, ureogenesis, amino acid transport, respiration and ion fluxes, the rapid changes in pyruvate dehydrogenase and pyruvate carboxylase, and the induction of P-enolpyruvate carboxykinase and other enzymes. 

This pattern of enzyme expression and activation may suggest that activation and inactivation of the enzyme, rather than altered expression during changing metabolic conditions seen in the rat may be more important as a mechanism for regulating and controlling ketogenesis subsequent to birth in human. 

Acetyl-CoA is therefore the substrate for two competing reactions with oxaloacetate to form citrate or with acetoacetyl-CoA to form ketone bodies (ketogenesis). Which reaction predominates depends partly on the rate of -oxidation itself and partly on the redox state of the mitochondrial matrix which controls the oxidation of malate to oxaloacetate, hence, the amount of oxaloacetate available to react with acetyl-CoA. The proportion of acetyl groups going into the TCA cycle relative to ketogenesis is often referred to as the acetyl ratio . The overall rate of -oxidation may be controlled by a number of well-known mechanisms ... 

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