AMYLOPECTIN STARCH PROMOTES THE DEVELOPMENT OF INSULIN-RESISTANCE IN RATS

Starches that are high in amylopectin are digested and absorbed more q uickly than starches with a high amylose content and produce larger po stprandial glucose and insulin responses. The aim of this study was to test the hypothesis that feeding rats a diet containing quickly diges ted starch could promote insulin resistance. Sprague-Dawley rats were fed either a high amylopectin or high amylose diet (two 10-g meals per day), and insulin sensitivity was assessed after 9 wk by intravenous glucose tolerance test (IVGTT). In the rats fed the high amylopectin d iet, glucose tolerance was significantly lower (P < 0.05) and the insu lin response to IVGTT was twice as high as in rats fed the high amylos e diet (P < 0.05). A second study using Wistar rats investigated the t ime course of these changes. Differences in the insulin response to th e IVGTT were not evident at 4 wk but began to emerge at 8 wk, and by 1 2 wk the insulin response was 100% greater in rats fed the high amylop ectin diet (P < 0.05) than in those fed the high amylose diet. In addi tion, basal plasma insulin concentration was higher in rats fed the hi gh amylopectin diet (P < 0.05). There were no differences, however, in glucose tolerance at any time point. The results suggest that quickly digested starch promotes the development of insulin resistance in rat s. The relatively slow time course resembles the normal development of insulin resistance in humans.