The effect of a high-carbohydrate diet on glucose, insulin sensitivity and plasma insulin in rats

Long-term effects on pancreatic function of feeding a HC formula to rats during the preweaning period

We have investigated pancreatic changes associated with hyperinsulinemia and an insulin secretory response to an oral glucose load in a new rat model for obesity. Male Sprague-Dawley pups were reared on a high-carbohydrate (HC) or high-fat (HF) formula by gastrostomy during the suckling period and were weaned onto a stock diet. These animals remained either nutritionally unchallenged or challenged with a high-sucrose diet during the postweaning period. The HC formula-fed animals showed increased insulin concentrations in the plasma and pancreas and also showed impaired insulin secretory response compared with mother-fed control or HF animals in adult life. Immunocytochemical and morphometric studies revealed that hyperinsulinemia in the HC animals during the preweaning period and also in adult life was associated with hypertrophy of beta-cells in the pancreas. The results show that consumption of a HC formula during the suckling period influences pancreatic islet morphology resulting in hyperinsulinemia which eventually leads to the development of obesity later in adult life.

Effects of altered adipose tissue morphology on plasma insulin levels in the rat

The usual covariates of adiposity--adipocyte size, total body fat, and food intake--were experimentally dissociated using three new models of altered adipose tissue morphology in the rat. It was thereby possible to test the hypothesis that plasma immunoreactive insulin level (IRI) is a function of mean adipocyte size. In two of the models, experimental and control rats differ substantially in total body fat but show no difference in mean adipocyte size. In these models, no difference in plasma IRI was found between experimental and control animals. In a third model, experimental and control rats differ in mean adipocyte size but not in total body fat or daily food intake. In this model, plasma IRI was found to differ between experimental and control rats. These observations demonstrate a close link between adipocyte size and plasma IRI and suggest that the hyperinsulinemia and peripheral insulin resistance of obesity are more likely due to adipocyte hypertrophy than to increases in total body fat or daily food intake.