An Association between Low Levels of Dietary Protein, Elevated NPY Gene Expression in the Basomedial Hypothalamus and...

We sought to extend our previous observation that low dietary protein could increase the gene expression of neuropeptide Y (NPY) in the basomedial hypothalamus. To better define the relationship between the level of dietary protein, NPY gene expression, and food intake, we examined the effect of 5 isocaloric diets, each containing a different level of dietary protein (5%, 10%, 15%, 20%, 35% casein). Test diets were fed for 11 days. Food intakes and body weights were monitored throughout. Total RNA was isolated from the basomedial hypothalamus and a dot blot analysis was performed to determine NPY mRNA levels. A body composition analysis was also performed. The average daily food intake was increased by about 20% in rats fed the 5% casein diet. These rats also had an increase in NPY gene expression. Body weight gain was severely attenuated due mainly to a decrease in body water, but also to a decrease in body protein. However, total body fat was increased such that there was no effect on total body energy content. These results suggest that low dietary protein can increase the capacity for NPY synthesis in the hypothalamus and that this may lead to an increase in food intake.