• Info
  • Home
  • About
  • Editorial Board
  • Archive
  • Research Topics
  • View Some Authors
  • Review Guidelines
  • Subscribe to Alerts
  • Search
  • Article Type

    Publication Date

  • Author Info
  • Why Submit?
  • Fees
  • Article Types
  • Author Guidelines
  • Submission Checklist
  • Contact Editorial Office
  • Submit Manuscript
Start date should be earlier than end date. OK Please enter valid date format.

Original Research ARTICLE

Share 0
Like 0

Steady-state brain glucose transport kinetics re-evaluated with a four-state conformational model

1
Center for Biomedical Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
2
Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
3
Department of Radiology, University of Lausanne, Lausanne, Switzerland
4
Department of Radiology, University of Geneva, Geneva, Switzerland
Glucose supply from blood to brain occurs through facilitative transporter proteins. A near linear relation between brain and plasma glucose has been experimentally determined and described by a reversible model of enzyme kinetics. A conformational four-state exchange model accounting for trans-acceleration and asymmetry of the carrier was included in a recently developed multi-compartmental model of glucose transport. Based on this model, we demonstrate that brain glucose (Gbrain) as function of plasma glucose (Gplasma) can be described by a single analytical equation namely comprising three kinetic compartments: blood, endothelial cells and brain. Transport was described by four parameters: apparent half saturation constant Kt, apparent maximum rate constant Tmax, glucose consumption rate CMRglc, and the iso-inhibition constant Kii that suggests Gbrain as inhibitor of the isomerisation of the unloaded carrier. Previous published data, where Gbrain was quantified as a function of plasma glucose by either biochemical methods or NMR spectroscopy, were used to determine the aforementioned kinetic parameters. Glucose transport was characterized by Kt ranging from 1.5 to 3.5 mM, Tmax/CMRglc from 4.6 to 5.6, and Kii from 51 to 149 mM. It was noteworthy that Kt was on the order of a few mM, as previously determined from the reversible model. The conformational four-state exchange model of glucose transport into the brain includes both efflux and transport inhibition by Gbrain, predicting that Gbrain eventually approaches a maximum concentration. However, since Kii largely exceeds Gplasma, iso-inhibition is unlikely to be of substantial importance for plasma glucose below 25 mM. As a consequence, the reversible model can account for most experimental observations under euglycaemia and moderate cases of hypo- and hyperglycaemia.
Keywords:
glucose transport, GLUT, mathematical modelling, blood-brain-barrier
Citation:
Duarte JMN, Morgenthaler FD, Lei H, Poitry-Yamate C and Gruetter R (2009). Steady-state brain glucose transport kinetics re-evaluated with a four-state conformational model. Front. Neuroenerg. 1:6. doi: 10.3389/neuro.14.006.2009
Received:
08 June 2009;
 Paper pending published:
01 July 2009;
Accepted:
11 September 2009;
 Published online:
12 October 2009.

Edited by:

Mary McKenna, University of Maryland, USA

Reviewed by:

Caroline Rae, University of New South Wales, Australia
Alexander Shestov, University of Minnesota, USA
Anthony Carruthers, University of Massachusetts Medical School, USA
Copyright:
© 2009 Duarte, Morgenthaler, Lei, Poitry-Yamate and Gruetter. This is an open-access article subject to an exclusive license agreement between the authors and the Frontiers Research Foundation, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited.
*Correspondence:
João M. N. Duarte, Ecole Polytechnique Fédérale de Lausanne SB IPMC LIFMET (Bâtiment CH), Station 6, CH-1015 Lausanne, Switzerland. e-mail: joao.duarte@epfl.ch
Share 0
Like 0

© 2007 - 2012 Frontiers Media S.A. All Rights Reserved