The hot IVGTT two-compartment minimal model: indexes of glucose effectiveness and insulin sensitivity.

A two-compartment minimal model (2CMM) has been proposed [A. Caumo and C. Cobelli.Am. J. Physiol. 264 (Endocrinol. Metab. 27): E829–E841, 1993] to describe intravenous glucose tolerance test (IVGTT) labeled (hereafter hot) glucose kinetics. This model, at variance with the one-compartment minimal model (1CMM), allows the estimation of a plausible profile of glucose production. The aim of this study is to show that the 2CMM also allows the assessment of insulin sensitivity ($S_I^{2*}$ ), glucose effectiveness ($S_G^{2*}$ ), and plasma clearance rate (PCR). The 2CMM was identified on stable-isotope IVGTTs performed in normal subjects (n = 14). Results were (means ± SE) $S_G^{2*}$ = 0.85 ± 0.14 ml ⋅ kg⁻¹ ⋅ min⁻¹, PCR = 2.02 ± 0.14 ml ⋅ kg⁻¹ ⋅ min⁻¹, and $S_I^{2*}$ = 13.83 ± 2.54 × 10⁻²ml ⋅ kg⁻¹ ⋅ min⁻¹ ⋅ μU⁻¹ ⋅ ml. The 1CMM was also identified; glucose effectiveness and insulin sensitivity indexes were $S{*}_G$ V = 1.36 ± 0.08 ml ⋅ kg⁻¹ ⋅ min⁻¹and $S{*}_I$ V = 12.98 ± 2.21 × 10⁻²ml ⋅ kg⁻¹ ⋅ min⁻¹ ⋅ μU⁻¹ ⋅ ml, respectively, where V is the 1CMM glucose distribution volume.$S{*}_G$ V was lower than PCR and higher than $S_G^{2*}$ and did not correlate with either [r = 0.45 (NS) andr = 0.50 (NS), respectively], whereas $S{*}_I$ V was not different from and was correlated with$S_I^{2*}$ (r = 0.95;P < 0.001).$S{*}_G$ compares well (r = 0.78;P < 0.001) with PCR normalized by the 2CMM total glucose distribution volume. In conclusion, the 2CMM is a powerful tool to assess glucose metabolism in vivo.