Figure 4.

Multinuclear NMR spectroscopy data supports the presence of an active Leloir pathway in GBM cells. (A) Portions of the representative ¹³C NMR spectra of GBM cells treated with either [U-¹³C]Glc (lower) or [U-¹³C]Gal (upper), showing the C₁ carbon of Gal-1-P (inset). The presence of this metabolite is evidence of the active Leloir pathway in GBM cells. Galactitol was also detected in Gal-treated GBM cells, suggesting the presence of aldose reductase activity in GBM cells. (B) ¹H NMR signal of H-1 of the Gal-1-P in [U-¹³C]Gal-treated GBM cells, showing the ¹H-¹³C spin–spin coupling in Gal-1P. (C) ³¹P NMR signals of Glc-1-P and Gal-1-P in Gal-treated GBM cells (upper panel) and Glc-treated cells (lower panel). (D) Portions of the ¹³C NMR spectra of GBM115 cells treated with [U-¹³C]Gal (upper) and [U-¹³C]Glc (lower). Insets showing Glu4, Lac3, and Ala3 from both Gal- and Glc-treated cells.