Assessment of insulin sensitivity with the minimal model: role of
the model assumptions.
Mari, Andrea.
Institute of Systems Science and Biomedical Engineering, National
Research Council, Padova, Italy
APStracts 4:0025E, 1997.
Insulin sensitivity is frequently assessed with the minimal model (MM)
and the insulin-modified intravenous glucose tolerance test (MIVGTT).
To ascertain the validity of this approach, the mechanisms by which
the MM estimates SG and SI from the data are analyzed theoretically.
Published data and new labeled MIVGTTs in normal and non-insulin
-dependent diabetic (NIDDM) subjects are used as reference data.
Results: 1)Eone reason for the reported difficulty in estimating SI
in NIDDM is the inadequacy of the MM to describe the data. 2)ESG is a
biased estimate of the fractional glucose clearance (FGC) at basal
insulin and SI is a biased estimate of the average slope of the
insulin concentrationDFGC curve. The monocompartmental assumption and
the role of glucose production in the MM are causes of bias. The bias
is fairly constant across the spectrum of glucose tolerance (SG:E150%
overestimate; SI:E30% underestimate). 3) SI is not expected to
account satisfactorily for hepatic insulin sensitivity. 4)EUsing SG
and SI the FGC at a target insulin level (FGCMM) can be estimated.
FGCMM agrees well with the analogous clamp index (difference 10%;
correlation: r=0.88, p<0.002), and in NIDDM has a lower
coefficient of variation than SI (57 vs 82%). Conclusion: this
analysis indicates that the MM is a sufficiently reliable method for
the assessment of insulin sensitivity if it is cautiously used
(Accepted for the Modeling in Physiology section).
Received 28 March 1996; accepted in final form 8 January 1997.
APS Manuscript Number E159-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 19 February 1997