Protein Status Modulates the Hedonic Value of Protein Meals in Rat

Abstract

Protein is an indispensable component of the diet and a low protein status usually induces preferences fo rprotein‐rich food in animal and in human. This study hypothesized that these preferences involve a modulation of the activity of the hedonic reward system.MethodsMale adult Wistar rats received ad‐libitum for 15 days a normoprotein (NP) or a low‐protein (P6) diet containing either 14% or 6% protein as energy, and were trained to receive a morning calibrated meal. The last day of the feeding period each group was separated in 3 subgroups, which received a morning calibrated P6, NP or high‐protein (HP: 55% protein as energy) meal. The brain was removed 90 minutes after the meal and activation of the nucleus accumbens (NAcc), a brain area implicated in the reward system, was estimated by immunofluorescence staining of c‐Fos protein.ResultsFood intake was not different between groups but body weight gain was lower in P6 compared to NP‐diet rats. In the NP‐diet group, the HP and P6 meals both induced lower NAcc activation compared to the NP meal (NP>HP,P6). In the P6‐diet group, postprandial NAcc activation correlated with the protein content of the meal (HP>NP>P6), and it was significantly higher compared to NP‐diet rats after the HP and NP meals and remains low following P6 meal, respectively.DiscussionIn a situation of protein deficiency the preferences for protein could be related to higher hedonic value of protein‐containing meals. In contrast, protein sufficiency lowers the hedonic value of protein‐containing meals.