amylopectin and Insulin-Resistance

The effect of long-term consumption of diets of different carbohydrate composition was investigated be feeding rats for up to 52 wk on diets in which the carbohydrate was either glucose, amylose or amylopectin. A glucose-based diet was included to examine the relationship between the rate of carbohydrate absorption from the diet and the development of insulin resistance. Insulin sensitivity was assessed by subjecting animals to an intravenous glucose tolerance test (IVGTT). Amylopectin-fed animals became progressively insulin resistant from 12 to 26 wk of feeding. The area under the plasma insulin curves in response to a glucose load (IVGTT) for these animals rose progressively from 15.1 +/- 2.5 nmol/L.30 min at 8 wk to 45.8 +/- 3.5 nmol/L.30 min (P < 0.001) at 26 wk of feeding. Amylose-fed animals did not exhibit insulin resistance until 26 wk of feeding when insulin secretion in response to a glucose load was 28.3 +/- 0.9 vs. 14.6 +/- 3.2 nmol/L.30 min at 16 wk of feeding (P < 0.005). Glucose-fed animals displayed insulin resistance after only 8 wk of feeding. At this time, the area under their plasma insulin curves was almost double that for amylose- or amylopectin-fed animals (P < 0.001). We conclude that long-term consumption of a diet in which available carbohydrate is rapidly absorbed causes insulin resistance in rats. The more rapidly glucose is absorbed from the diet, the faster the insulin resistance develops.

Topics: Absorption; Amylopectin; Amylose; Animals; Blood Glucose; Dietary Carbohydrates; Glucose; Glucose Tolerance Test; Hyperinsulinism; Infusions, Intravenous; Insulin; Insulin Resistance; Male; Rats; Rats, Wistar; Time Factors; Weight Gain

Starches that are high in amylopectin are digested and absorbed more quickly than starches with a high amylose content and produce insulin resistance in rats during long-term feeding. The aim of this study was to determine whether amylopectin-induced insulin resistance could be prevented or reversed by a period of high amylose feeding. We employed a randomized design in which two groups of rats were fed either the high amylose and then the high amylopectin diet for two consecutive 8-wk periods or vice versa (high amylopectin and then high amylose). Four other groups were fed either a high amylose or a high amylopectin diet for 8 or 16 wk. All rats were fed two 10-g meals per day (300 kJ/d), and insulin sensitivity was assessed by intravenous glucose tolerance test (IVGTT) after 8 or 16 wk of feeding. We found no difference in glucose tolerance between any group at any time point. Insulin responses, however, were 50% higher (P < 0.01) after 16 wk of high amylopectin feeding [area under the plasma insulin curve (AUC) = 18.1 +/- 1.4 nmol.L-1 x 15 min] compared with high amylose feeding (AUC = 13.0 +/- 1.2 nmol.L-1 x 15 min). The two groups which received both diets developed a similar degree of insulin resistance, equivalent to that after 16 wk of high amylopectin feeding. The findings suggest that amylopectin-induced insulin resistance cannot be reversed or prevented by either a subsequent or previous period of amylose feeding. Taken together, the data suggest that the nature of starch in the Western diet influences the development of noninsulin-dependent diabetes mellitus in humans.

Topics: Amylopectin; Amylose; Animals; Glucose; Glucose Tolerance Test; Insulin; Insulin Resistance; Male; Random Allocation; Rats; Rats, Wistar; Time Factors

Starches that are high in amylopectin are digested and absorbed more quickly than starches with a high amylose content and produce larger postprandial glucose and insulin responses. The aim of this study was to test the hypothesis that feeding rats a diet containing quickly digested 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 diet, glucose tolerance was significantly lower (P < 0.05) and the insulin response to IVGTT was twice as high as in rats fed the high amylose diet (P < 0.05). A second study using Wistar rats investigated the time course of these changes. Differences in the insulin response to the IVGTT were not evident at 4 wk but began to emerge at 8 wk, and by 12 wk the insulin response was 100% greater in rats fed the high amylopectin diet (P < 0.05) than in those fed the high amylose diet. In addition, basal plasma insulin concentration was higher in rats fed the high amylopectin diet (P < 0.05). There were no differences, however, in glucose tolerance at any time point. The results suggests that quickly digested starch promotes the development of insulin resistance in rats. The relatively slow time course resembles the normal development of insulin resistance in humans.

Topics: Amylopectin; Amylose; Animals; Blood Glucose; Diabetes Mellitus, Type 2; Diet; Disease Models, Animal; Eating; Glucose Tolerance Test; Hyperglycemia; Insulin; Insulin Resistance; Male; Rats; Rats, Sprague-Dawley; Rats, Wistar; Specific Pathogen-Free Organisms; Time Factors; Weight Gain