Fig. 1

Incorporation of ¹³C-labeled substrate can be measured by mass changes in product metabolites. U-[¹³C₆]-glucose incorporation into acetyl-CoA and subsequently into HMG-CoA is shown here as an example. Carbons derived from glucose can be incorporated into acetyl-CoA, and subsequently into HMG-CoA in units of 2. Thus, 2, 4 or 6 labeled carbons can be added to a HMG-CoA molecule, producing the M2, M4 or M6 isotopologues, respectively