Insulin sensitivity and glucose effectiveness estimated by the minimal model technique in spontaneously hypertensive and normal rats

Abstract

This study was performed to compare glucose metabolism in anaesthetised spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) in an attempt to clarify whether this animal model of hypertension approximates the insulin-resistant state seen in human hypertension. With this aim the minimal model of glucose kinetics was applied to glucose and insulin data derived from a 12-sample, 120 min intravenous glucose tolerance test (IVGTT) performed in ten SHR and nine WKY rats under pentobarbital anaesthesia. This method provided two metabolic indices: the glucose effectiveness, S(G), which quantifies the ability of glucose per se to enhance its rate of disappearance and to inhibit hepatic glucose production, and the insulin sensitivity, S(I), which measures the ability of insulin to enhance plasma glucose disappearance and to inhibit hepatic glucose production. Systolic and diastolic arterial pressures in the SHR group were significantly higher (P < 0.0005) than in the WKY group. Mean S(G) and S(I) estimates from the SHR group (S(G) = 16.2 (≠ 2.0) x 10-2 dl min-1 kg-1 and S(I) = 12.5 (± 1.9) x 10-4 dl min-1 kg-1 (μU ml-1)-1) were not significantly different (P > 0.05) from mean estimates that characterised the WKY group (S(G) = 13.1 (± 1.5) x 10-2 dl min-1 kg-1 and S(I) = 15.8 (± 4.3) x 10-4 dl min-1 kg-1 (μU ml-1)-1). This result is in contrast with reported findings from humans in which insulin sensitivity is significantly reduced in the presence of hypertension.