Figure 5.

Glucose inhibits the oxidation of glutamine but not of pyruvate. Starved Huh7 or N2A cells were loaded in oxygraph chambers, and after basal respiration was recorded, cells were maintained without any exogenous substrate (−; white bars) or incubated with 5 mm glucose (Gluc) (dark gray bars); a substrate that cells have high capacity to use, 2.5 mm glutamine (Gln) for Huh7 or 10 mm pyruvate (Pyr) for N2A (black bars); or 5 mm glucose followed by the chosen substrate (light gray bars). After stabilization of the signal, OCR was recorded, and cells were treated with oligomycin for measurement of uncoupled OCR and FCCP for measurement of the maximal respiration. A, coupled OCR of Huh7 or N2A cells as indicated in the figure. B, maximum respiration achieved in the same experiments. For each graph, individual data points are represented with symbols. Error bars represent mean ± S.D. of four to five independent experiments, and asterisks show significant differences between coupled OCR without substrates and coupled OCR calculated after reintroduction of substrates: *, p < 0.05; **, p < 0.01.