The oral glucose minimal model: Estimation of insulin sensitivity from a meal test

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Abstract
Recently, a new approach has been proposed to estimate insulin sensitivity (S/sub I/) from an oral glucose tolerance test or a meal using an "integral equation". Here, we improve on the "integral equation" by resorting to a "differential equation" approach. The classic glucose kinetics minimal model was used with the addition of a parametric model for the rate of appearance into plasma of oral glucose (Ra). Three behavioral models of Ra were proposed: piecewise-linear (P), spline (S) and dynamic (D). All three models performed satisfactorily allowing a precise estimation of S/sub I/ and a plausible reconstruction of Ra. Mean S/sub I/ estimates were virtually identical: S/sub I//sup P/=6.81/spl plusmn/0.87 (SE); S/sub I//sup S/=6.53/spl plusmn/0.80; and S/sub I//sup D/=6.62/spl plusmn/0.79. S/sub I/ strongly correlated with the integral-equation index (I) S/sub I//sup I/:r=0.99, p<0.01 for models D and S, and r=0.97, p<0.01 for P. Also, S/sub I/ compared well with insulin sensitivity estimated from intravenous glucose tolerance test in the same subjects (r=0.75, p<0.01; r=0.71, p<0.01; r=0.73, p<0.01, respectively, for P, S, and D models versus S/sub I//sup IVGTT/). Finally, the novel approach allows estimation of S/sub I/ from a shorter test (120 min): model P yielded S/sub I//sup R/=7.16/spl plusmn/1.0 (R for reduced) which correlated very well with S/sub I//sup P/ and S/sub I//sup I/ (respectively, r=0.94, p<0.01; r=0.95, p<0.01) and still satisfactorily with S/sub I//sup IVGTT/ (r=0.77, p<0.01).