Protein and glucose metabolism during isolated closed head
injury.
Flakoll, Paul J., Laura S. Wentzel, and Steve A. Hyman.
Departments of Surgery, Biochemistry and Anesthesiology, Vanderbilt
University Medical Center, Nashville, TN
APStracts 2:0098E, 1995.
Patients with isolated closed head injuries are characterized by
excessive nitrogen loss, hyperglycemia and increased caloric demand.
However, the relative contributions of specific metabolic events,
such as protein breakdown and synthesis or glucose production and
utilization to the physiological changes prevalent during isolated
closed head injury remains unestablished. Using isotopic dilutions of
L-[1-13C]leucine and D-[3-3H]glucose, components of protein and
glucose metabolism were examined in patients with isolated closed
head injury (n=7). Normal overnight-fasted volunteers (n=8) were also
studied as a reference point for comparison. Despite prevailing
hyperinsulinemia (29+/-5 [mu]U/ml), head injured patients had
elevated plasma leucine concentrations (183+/-22 vs 144+/-8
[mu]mol/l), whole-body proteolysis (331+/-44 vs 150+/-7 mg/kg.h),
protein synthesis (248+/-38 vs 126+/-11 mg/kg.h), and amino acid
oxidation (84+/-11 vs 23+/-3 mg/kg.h). Therefore, nitrogen loss
normally associated with isolated closed head injury is primarily due
to an increase in the rate of whole-body proteolysis with a greater
proportion of the resultant amino acids being oxidized for energy.
Furthermore, head injured patients were hyperglycemic (6.7+/-0.3
[mu]mol/l) with increased rates of glucose turnover (an estimate of
production and utilization) when compared to the controls (4.0+/-0.7
vs 2.5+/-0.2 mg/kg.min). Hence, these data suggest that head injury,
even in the absence of peripheral trauma, induces a physiological
state of accelerated metabolism associated with resistance to insulin
action.
Received 25 April 1994; accepted in final form 28 April 1995.
APS Manuscript Number E151-4.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 9 May 1995.