Evaluation of different methods for assessment of insulin sensitivity in Göttingen minipigs: introduction of a new, simpler method

The use of animal models in diabetes research requires reliable tests for evaluation of insulin sensitivity and beta-cell function. Minipigs are being increasingly used in metabolic research, and the aim of this study was to compare different tests and indexes for evaluation of insulin sensitivity and beta-cell function in Göttingen minipigs. Hyperinsulinemic, isoglycemic clamp, intravenous (IVGTT) and oral glucose tolerance tests (OGTT), and a modified insulin tolerance test were performed in minipigs fed either low- or high-energy diet. Furthermore, the reproducibility of IVGTT-derived parameters was assessed. Previously described insulin sensitivity indexes [steady-state glucose infusion rate/glucose concentration/insulin concentration from clamp (M/G/I); oral glucose insulin sensitivity (OGIS) and ISI(comp) from OGTT; S(I) from minimal model analysis of IVGTT; and quantitative insulin sensitivity check index from fasting values] were calculated together with an insulin sensitivity index from the modified insulin tolerance test (ISI(ITT)) and a new simple index (S2) derived from the first 30 min of the IVGTT. beta-Cell function was assessed from the IVGTT and the OGTT. Reproducibility of the IVGTT-derived parameters was calculated as median intraindividual coefficient of variation (CV%).M/G/I correlated significantly only with S2 (P < 0.05, r = 0.54). S2 furthermore correlated with S(I) (P < 0.001, r = 0.81), ISI(ITT) (P < 0.001, r = 0.57), and the two indexes from OGTT, ISI(comp) (P < 0.001, r = 0.78) and OGIS (p < 0.05, r = 0.48). No correlation was found between beta-cell function indexes from OGTT and IVGTT. The median CV% of the new S2 index was 13. In conclusion, the new simple index of insulin sensitivity, S2, was revealed to be useful for evaluation of insulin sensitivity in pigs.