The Protein Status of Rats Affects the Rewarding Value of Meals Due to their Protein Content
The Journal of Nutrition. 2018-06-01; 148(6): 989-998
DOI: 10.1093/jn/nxy060
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Chaumontet C(1), Recio I(1), Fromentin G(1), Benoit S(1), Piedcoq J(1), Darcel N(1), Tomé D(1).
Author information:
(1)Unité Mixte de Recherches (UMR) Physiologie de la Nutrition et du
Comportement Alimentaire (PNCA), AgroParisTech, Institut National de la
Recherche Agronomique (INRA), Université Paris-Saclay, 75005 Paris, France 3.
Erratum in
J Nutr. 2019 Feb 1;149(2):354. doi: 10.1093/jn/nxy254.
BACKGROUND: Protein status is controlled by the brain, which modulates feeding
behavior to prevent protein deficiency.
OBJECTIVE: This study tested in rats whether protein status modulates feeding
behavior through brain reward pathways.
METHODS: Experiments were conducted in male Wistar rats (mean ± SD weight;
230 ± 16 g). In experiment 1, rats adapted for 2 wk to a low-protein (LP; 6% of
energy) or a normal-protein (NP; 14% of energy) diet were offered a choice
between 3 cups containing high-protein (HP; 50% of energy), NP, or LP feed;
their intake was measured for 24 h. In 2 other experiments, the rats were
adapted for 2 wk to NP and either HP or LP diets and received, after overnight
feed deprivation, a calibrated HP, NP, or LP meal daily. After the meal, on the
last day, rats were killed and body composition and blood protein,
triglycerides, gut neuropeptides, and hormones were determined. In the brain,
neuropeptide mRNAs in the hypothalamus and c-Fos protein and opioid and
dopaminergic receptor mRNAs in the nucleus accumbens (NAcc) were measured.
RESULTS: Rats fed an LP compared with an NP diet had 7% lower body weight,
significantly higher protein intake in a choice experiment (mean ± SD:
30.5% ± 0.05% compared with 20.5% ± 0.05% of energy), higher feed-deprived blood
ghrelin, lower postmeal blood leptin, and higher neuropeptide Y (Npy) and
corticotropin-releasing hormone (Crh) mRNA expression in the hypothalamus. In
contrast to NP, rats fed an LP diet showed postmeal c-Fos protein expression in
the NAcc, which was significantly different between meals, with LP < NP < HP. In
contrast, in rats adapted to an HP diet compared with an NP diet, energy intake
was lower; and in the NAcc, meal-induced c-Fos protein expression was 20% lower,
and mRNA expression was 17% higher for dopamine receptor 2 (Drd2) receptors and
38% lower for κ opioid receptor (Oprk1) receptors.
CONCLUSION: A protein-restricted diet induced a reward system-driven appetite
for protein, whereas a protein-rich diet reduced the meal-induced activation of
reward pathways and lowered energy intake in male rats.
DOI: 10.1093/jn/nxy060
PMID: 29878268 [Indexed for MEDLINE]