title: Direct measurement of brain glucose concentrations in humans by 13C NMR spectroscopy.
abstract: Glucose is the main fuel for energy metabolism in the normal human brain. It is generally assumed that glucose transport into the brain is not rate-limiting for metabolism. Since brain glucose concentrations cannot be determined directly by radiotracer techniques, we used 13C NMR spectroscopy after infusing enriched D-[1-13C]glucose to measure brain glucose concentrations at euglycemia and at hyperglycemia (range, 4.5-12.1 mM) in six healthy children (13-16 years old). Brain glucose concentrations averaged 1.0 +/- 0.1 mumol/ml at euglycemia (4.7 +/- 0.3 mM plasma) and 1.8-2.7 mumol/ml at hyperglycemia (7.3-12.1 mM plasma). Michaelis-Menten parameters of transport were calculated to be Kt = 6.2 +/- 1.7 mM and Tmax = 1.2 +/- 0.1 mumol/g.min from the relationship between plasma and brain glucose concentrations. The brain glucose concentrations and transport constants are consistent with transport not being rate-limiting for resting brain metabolism at plasma levels greater than 3 mM.
authors.affiliation: Department of Molecular Biophysics, Yale University School of Medicine, New Haven, CT 06510.
authors.forename: R
authors.initials: R
authors.lastname: Gruetter
authors.forename: E J
authors.initials: EJ
authors.lastname: Novotny
authors.forename: S D
authors.initials: SD
authors.lastname: Boulware
authors.forename: D L
authors.initials: DL
authors.lastname: Rothman
authors.forename: G F
authors.initials: GF
authors.lastname: Mason
authors.forename: G I
authors.initials: GI
authors.lastname: Shulman
authors.forename: R G
authors.initials: RG
authors.lastname: Shulman
authors.forename: W V
authors.initials: WV
authors.lastname: Tamborlane
mesh_terms: D000293:Adolescent; D001692:Biological Transport; D001921:Brain / Q000378:metabolism; D001923:Brain Chemistry; D005947:Glucose / Q000032:analysis* / Q000378:metabolism; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*
chemical_list: D005947:Glucose