Localized 13C NMR spectroscopy in the human brain of amino acid labeling from D-[1-13C]glucose

J Neurochem. 1994 Oct;63(4):1377-85. doi: 10.1046/j.1471-4159.1994.63041377.x.


Cerebral metabolism of D[1-13C]glucose was studied with localized 13C NMR spectroscopy during intravenous infusion of enriched [1-13C]glucose in four healthy subjects. The use of three-dimensional localization resulted in the complete elimination of triacylglycerol resonance that originated in scalp and subcutaneous fat. The sensitivity and resolution were sufficient to allow 4 min of time-resolved observation of label incorporation into the C3 and C4 resonances of glutamate and C4 of glutamine, as well as C3 of aspartate with lower time resolution. [4-13C]Glutamate labeled rapidly reaching close to maximum labeling at 60 min. The label flow into [3-13C]glutamate clearly lagged behind that of [4-13C]-glutamate and peaked at t = 110-140 min. Multiplets due to homonuclear 13C-13C coupling between the C3 and C4 peaks of the glutamate molecule were observed in vivo. Isotopomer analysis of spectra acquired between 120 and 180 min yielded a 13C isotopic fraction at C4 glutamate of 27 +/- 2% (n = 4), which was slightly less than one-half the enrichment of the C1 position of plasma glucose (63 +/- 1%), p < 0.05. By comparison with an external standard the total amount of [4-13C]glutamate was directly quantified to be 2.4 +/- 0.1 mumol/ml-brain. Together with the isotopomer data this gave a calculated brain glutamate concentration of 9.1 +/- 0.7 mumol/ml, which agrees with previous estimates of total brain glutamate concentrations. The agreement suggests that essentially all of the brain glutamate is derived from glucose in health human brain.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Amino Acids / biosynthesis*
  • Aspartic Acid / biosynthesis
  • Blood Glucose / metabolism
  • Brain / metabolism*
  • Carbon Isotopes
  • Female
  • Glucose / metabolism*
  • Glutamic Acid / biosynthesis
  • Humans
  • Isotope Labeling / methods
  • Magnetic Resonance Spectroscopy / methods*
  • Male
  • Reference Values
  • Time Factors


  • Amino Acids
  • Blood Glucose
  • Carbon Isotopes
  • Aspartic Acid
  • Glutamic Acid
  • Glucose