Numerous lines of evidence indicate that the pancreatic hormone amylin contributes to meal-ending satiation. This action seems to be mediated by direct action of amylin on area postrema (AP) neurons. Here, we investigated the effect of different nutrients on amylin’s ability to induce c-Fos expression and to reduce eating. Amylin (5g/kg SC) increased c-Fos expression in the AP more strongly in fasted rats and in rats fed a nutrient-deficient non-caloric diet (NCD) than in rats fed chowad libitum. Supplementation of NCD with protein, but not with glucose or fat, reduced the amylin-mediated AP c-Fos response. Similarly, parenteral injection of an amino acid mixture also significantly attenuated the amylininduced c-Fos expression in the AP in rats that had no access to food.
Feeding studies are in line with these findings in that amylin injection failed to reduce food intake in NCD/protein fed rats, whereas amylin did reduce food intake in animals fed NCD, NCD/glucose or NCD/fat. Amylin’s effect to reduce eating was particularly strong in rats fed a low-protein (1%) diet (85% reduction in eating compared
to controls versus approx. 50% in normal-protein [22%] diet). To summarize, our studies designed to understand the influence of dietary components on the effectiveness of amylin to reduce eating showed that amylin’s effect is particularly strong when the protein content of the diet is low. The exact mechanisms through which protein diets/amino acids reduce amylin’s effect to inhibit eating are still unknown.