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

Recently, a new approach has been proposed to estimate insulin sensitivity (S _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 _I and a plausible reconstruction of Ra. Mean S _I estimates were virtually identical: S _I ^P=6.81±0.87 (SE); S _I ^S=6.53±0.80; and S _I ^D=6.62±0.79. S _I strongly correlated with the integral-equation index (I) S _I ^I:r=0.99, p<0.01 for models D and S, and r=0.97, p<0.01 for P. Also, S _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 _I ^IVGTT). Finally, the novel approach allows estimation of S _I from a shorter test (120 min): model P yielded S _I ^R=7.16±1.0 (R for reduced) which correlated very well with S _I ^P and S _I ^I (respectively, r=0.94, p<0.01; r=0.95, p<0.01) and still satisfactorily with S _I ^IVGTT (r=0.77, p<0.01).