Simple Assessment of Insulin Sensitivity in the Zucker Rat

The model-based assessment of insulin sensitivity in Zucker rat from Intravenous Glucose Tolerance Test (IVGTT) data is a common procedure. The minimal model methodology provides a very reliable assessment but requires specific competence for running the model. The aim of this study was presenting calculated SI (CSI), as a surrogate index for the simple assessment of insulin sensitivity in the Zucker Rat from IVGTT data. To this aim 25 Zucker Lean Rats (ZLR) and 25 Zucker Fatty Rats (ZFR) were considered. Reference insulin sensitivity (SI) was estimated in each rat through the minimal model methodology. CSI is defined as the ratio between the rate of glucose disappearance (KG) and the mean supra-basal area under the insulin curve during the test (ΔAUCINS), corrected by the proportionality term, α. Regression analysis between SI and KG/ΔAUCINS was performed to identify the α coefficient. Results showed as the computed value of CSI presented a high correlation (r = 0.89, R-square = 0.80 and p < 0.0001, slope ≈1) with SI. Mean value of CSI over the whole population was not significantly different from correspondent SI value (p = 0.17). CSI is able to detect the wellknown reduction of insulin sensitivity in the ZFR group (1.0±0.1 vs. 5.0±0.7 min-1/μU·ml-1, p < 0.001), in accordance with the results provided by SI. In conclusion, the present study proposes CSI, as a suitable empiric index for a simple and reliable assessment of insulin sensitivity in Zucker rat and able to provide the same quantitative information of modelbased SI.