Techniques for the measurement of ketone body and lactate kinetics in vivo

Tracers are widely used to determine the kinetics of substrates. Although all tracer applications require assumptions, the issues that surround the study of the ketone bodies (β-hydroxybutyrate) and acetoacetate) and lactate-pyruvate-alanine are particularly difficult. The presence of isotopic disequilibrium between reversibly interconverting substrates such as these requires a more sophisticated approach, often with multiple tracers. Empirical validation, although always desirable, is difficult to accomplish when studying lactate metabolism. Additional work is needed to develop better methods for quantifying the kinetics of pyruvate carbon (i.e., lactate, pyruvate, and alanine).