End products of glucose and glutamine metabolism by cultured cell lines

Rates of CO2 production from glucose and glutamine, intracellular metabolite levels, and release of metabolic end products into the culture medium were determined for 13 cultured cell lines, including a glycolysis-defective mutant. All the non-mutant lines synthesized pyruvate, lactate, alanine, proline, aspartate, and citrate, so that the metabolism of glucose and glutamine resulted mainly in the production of these compounds and only to a lesser extent in complete oxidation to CO2. These data and the pattern of metabolites produced by the mutant line were consistent with a model characterized by incomplete glutamine oxidation leading to end product accumulation. Multiple linear regression analysis identified the metabolite levels most highly correlated with the intracellular citrate level and with the amount of citrate released into the medium. The analysis also showed that the rates of CO2 production from glucose and glutamine were themselves positively correlated, suggesting that the oxidation of the two substrates is coordinately controlled under normal culture conditions.