Changes in cerebral blood flow and carbohydrate metabolism during
acute hyperketonemia.
Hasselbalch, Steen G., Peter Lund Madsen, Lars Pinborg Hageman,
Karsten Skovgaard Olsen, Niels Justesen, Soren Holm, and Olaf B.
Paulson.
Departments of Neurology, Anesthesiology, and #Nuclear Medicine,
and Hospital Pharmacy, Rigshospitalet, National University Hospital,
Copenhagen, Denmark
APStracts 2:0251E, 1995.
During starvation brain energy metabolism in humans changes towards
oxidation of ketone bodies. In order to investigate if this shift is
directly coupled to circulating blood concentrations of ketone bodies
we measured global cerebral blood flow and global cerebral
carbohydrate metabolism with the Kety-Schmidt technique before and
during intravenous infusion with ketone bodies. During acute
hyperketonemia (mean beta-hydroxybutyrate blood concentration 2.16
mM) cerebral uptake of ketones increased from 1.11 to 5.60
[mu]molx100 g-1xmin-1, counterbalanced by an equivalent reduction of
the cerebral glucose metabolism from 25.8 to 17.2 [mu]molx100g-1xmin
-1, the net result being an unchanged cerebral uptake of
carbohydrates. In accordance with this, global cerebral oxygen
metabolism was not significantly altered (144 vs. 135 [mu]molx100g
-1xmin-1). The unchanged global cerebral metabolic activity was
accompanied by a 39% increase in CBF from 51.0 to 70.9 mlx100g-1xmin
-1. Regional analysis of the glucose metabolism by PET-FDG indicated
that mesencephalon does not oxidize ketone bodies to the same extent
as the rest of the brain. It was concluded that the immediate
oxidation of ketone bodies induced a decrease in cerebral glucose
uptake in spite of an adequate glucose supply to the brain.
Furthermore, acute hyperketonemia caused a resetting of the coupling
between cerebral blood flow and metabolism, which could not be
explained by alterations in PaCO2 or pH.
Received 8 September 1995; accepted in final form 21 November
1995.
APS Manuscript Number E439-5.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 December 95