The Relative Role of Insulin Action and Secretion in Experimental Animal Models of Metabolic Syndrome

Abstract

In the present study we evaluated insulin action and secretion in a group of 7 young Zucker fatty rats (ZFR), and in a group of 8 spontaneously hypertensive rats (SHR), compared with two control groups of 7 young Zucker lean rats (ZLR) and 8 Wistar Kyoto rats (WKY), respectively. Our goal is to broaden the characterization of glucose tolerance, including insulin secretion, in two animal models used for the characterization of human metabolic syndrome: The ZFR and the SHR. Reliable estimates of insulin sensitivity index, SI, was provided by minimal model analysis of IVGTT data. To characterize insulin secretion we calculated an index based on IVGTT data: AIRG, i.e. the acute insulin response after glucose bolus, related to the first phase insulin secretion. The ZFR showed a significantly (p<0.005) lower mean estimate of SI, and a significantly (p<0.001) higher mean value of AIRG, compared to control groups (ZLR and WKY) and hypertensive rats (SHR). Thus, only the ZFR shows a reduced insulin action, compensated only partially by insulin hypersecretion. This suggests obesity, with respect to hypertension, as a primary factor in the deterioration of glucose tolerance.