title: Simultaneous measurement of glucose transport and utilization in the human brain.
abstract: Glucose is the primary fuel for brain function, and determining the kinetics of cerebral glucose transport and utilization is critical for quantifying cerebral energy metabolism. The kinetic parameters of cerebral glucose transport, K(M)(t) and V(max)(t), in humans have so far been obtained by measuring steady-state brain glucose levels by proton ((1)H) NMR as a function of plasma glucose levels and fitting steady-state models to these data. Extraction of the kinetic parameters for cerebral glucose transport necessitated assuming a constant cerebral metabolic rate of glucose (CMR(glc)) obtained from other tracer studies, such as (13)C NMR. Here we present new methodology to simultaneously obtain kinetic parameters for glucose transport and utilization in the human brain by fitting both dynamic and steady-state (1)H NMR data with a reversible, non-steady-state Michaelis-Menten model. Dynamic data were obtained by measuring brain and plasma glucose time courses during glucose infusions to raise and maintain plasma concentration at ∼17 mmol/l for ∼2 h in five healthy volunteers. Steady-state brain vs. plasma glucose concentrations were taken from literature and the steady-state portions of data from the five volunteers. In addition to providing simultaneous measurements of glucose transport and utilization and obviating assumptions for constant CMR(glc), this methodology does not necessitate infusions of expensive or radioactive tracers. Using this new methodology, we found that the maximum transport capacity for glucose through the blood-brain barrier was nearly twofold higher than maximum cerebral glucose utilization. The glucose transport and utilization parameters were consistent with previously published values for human brain.
authors.affiliation: Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Shestov
authors.forename: Uzay E
authors.initials: UE
authors.lastname: Emir
authors.forename: Anjali
authors.initials: A
authors.lastname: Kumar
authors.forename: Pierre-Gilles
authors.initials: PG
authors.lastname: Henry
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Seaquist
authors.forename: Gülin
authors.initials: G
authors.lastname: Öz
mesh_terms: D000293:Adolescent; D000328:Adult; D001692:Biological Transport; D001812:Blood-Brain Barrier / Q000378:metabolism; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D001923:Brain Chemistry / Q000187:drug effects / Q000502:physiology; D005260:Female; D005947:Glucose / Q000378:metabolism* / Q000493:pharmacokinetics*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011522:Protons; D015203:Reproducibility of Results; D014894:Weights and Measures; D055815:Young Adult
chemical_list: D011522:Protons; D005947:Glucose