Effects of Long-Term High-Fat/High-Energy and High-Protein Diets on Insulin and Ghrelin Expression in Developing Rats

Objective. This study investigated the long-term effects of high-fat/high-energy and high-protein diets on insulin secretion and ghrelin expression. Methods. Dams of Sprague-Dawley rats were fed a standard, high-fat/high-energy, or high-protein diet during pregnancy and lactation, and their pups were defined as control, high-fat and high-energy, and high-protein groups, respectively. The pups were fed the same diet as their dams after weaning. Plasma glucose, ghrelin, and insulin were analyzed on the first, third, seventh, and tenth postnatal days and at the end of second, third, fourth, eighth, and twelfth weeks. Ghrelin and insulin expression in the pancreas was measured using radioimmunoassay, double-staining immunohistochemistry, and confocal microscopy. Results. Fasting blood glucose, plasma insulin concentrations, and homeostasis model assessment-insulin resistance index increased with age. Total plasma ghrelin concentrations decreased with age. Plasma ghrelin concentrations were negatively correlated with glucose levels in all three groups. Plasma ghrelin was negatively correlated with plasma insulin only in the high-fat and high-energy group. Insulin secretion in the high-protein and high-fat and high-energy groups and pancreatic ghrelin content, pancreatic ghrelin-positive cells, and beta cells in all groups decreased with age. The percentage of ghrelin-positive cells correlated with the percentage of beta cells in all groups. Conclusion. Insulin and ghrelin expression in the plasma and pancreas was adversely affected by long-term high-fat/high-energy and high-protein diets.