Fig. 3.
Lipid synthesis in proliferating glioblastoma cells. (A) The labeling of three fatty acyl (FA) resonances, the ω (methyl), ω-2, and methylene [−(CH2)n−] increased throughout the experiment at a constant rate, demonstrating continuous transfer of 13C from glucose into fatty acids. (B) Cells were cultured in medium containing [U-14C6]glucose, and then lipids were extracted and analyzed by thin-layer chromatography. The average and standard deviation for three parallel cultures are shown for each lipid species. (C) Cells were cultured in medium containing 10 mM [U-13C6]glucose, and then lipids were extracted and analyzed by NMR spectroscopy. The Inset shows an expansion of the 23-ppm region, highlighting the ω-1 multiplet (d, doublet; t, triplet). (D) Cells were cultured in medium containing 4 mM [3-13C]glutamine and 10 mM unlabeled glucose (time 0–6.25 h), followed by medium containing 4 mM [3-13C]glutamine and 10 mM [1,6-13C2]glucose (time 6.25–13 h). The relative rate (R.R.) for the increase in −(13CH2)n− signal was calculated for both halves of the experiment.