Measurement of glucose appearance and disappearance in the presence
of changing glucose concentrations in humans: error analysis for the
estimation of glucose disappearance.
Caumo, Andrea, Mal Homan, Harold Katz, Claudio Cobelli, and Robert
Rizza.
Endocrine Research Unit,Department of Medicine, Mayo Clinic,
Rochester, MN 55905, Department of Electronics and
Informatics,University of Padua, Padua, Italy, San Raffaele
Scientific Institute, University of Milan, Milan, Italy
APStracts 2:0079E, 1995.
The present studies were undertaken to determine whether a) the cold-
and hot-GINF techniques used with Steele's model provide equivalent
estimates of the rate of glucose appearance, Ra, and the rate of
glucose disappearance, Rd, in the presence of physiologic changes in
glucose and insulin concentrations, b) the conditions for the best
estimation of Ra are the same as those for Rd, c) the magnitude of
error (if present) differs in diabetic and nondiabetic subjects, d)
situations exist where the knowledge of Rd allows inferences to be
made on whole-body glucose uptake. To do so we performed experiments
in NIDDM and nondiabetic subjects using simultaneous infusions of [6
-3H] glucose and [6-14C] glucose; glucose and insulin were infused to
mimic normal postprandial glucose and insulin profiles; the infused
glucose contained [6-14C] glucose but not [6-3H] glucose. Compared to
the hot-GINF method, the traditional cold-GINF method underestimated
(p<0.05) Ra and Rd by 10-15% and hepatic glucose release by 25-50%
during the first hour of the study, with the magnitude of error being
the same in both diabetic and nondiabetic subjects. Error analysis
demonstrated that errors in Ra and Rd have different analytical
expressions containing common structural but different volume errors.
Both Ra and Rd can be accurately measured in diabetic and nondiabetic
subjects if glucose specific activity is kept constant and if the
volume of the accessible pool is used to calculate glucose
disappearance. The relationship between Rd and whole-body glucose
uptake was also derived. While Rd can be determined by relying on
measurements in the accessible pool only, the assessment of whole
-body glucose uptake requires a model of the nonaccessible portion of
the glucose system. However, knowledge of Rd can provide useful
insights into the behaviour of whole-body glucose uptake.
Received 23 February 1994; accepted in final form 7 April 1995.
APS Manuscript Number E76-4.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 April 1995.