Dietary Macronutrient Composition Affects the Influence of Exogenous Prolactin-Releasing Peptide on Appetite Responses and Hypothalamic Gene Expression in Chickens.
BACKGROUND
The interaction between the effects of exogenous neurotransmitters and dietary composition on appetite regulation in nonmammalian species is unclear.


OBJECTIVE
The objective of this study was to determine the effects of exogenous prolactin-releasing peptide (PrRP) and dietary macronutrient composition on food intake regulation in broiler chicks.


METHODS
Three isocaloric diets were formulated: high-carbohydrate (HC), high-fat (HF; 60% of ME from lard) and high-protein (HP) diets. In Expt. 1, 4-d-old Hubbard × Cobb-500 chicks fed 1 of the 3 diets since hatch were intracerebroventricularly injected with 0 (vehicle), 3, or 188 pmol PrRP (n = 10). Food intake was measured for 180 min. In Expt. 2, hypothalamic mRNA abundance of appetite-associated factors was measured in hypothalamus samples obtained 1 h postinjection of 0 or 188 pmol PrRP. In Expt. 3, chicks were given free access to all diets before and after intracerebroventricular injection and food intake was measured.


RESULTS
Three and 188 pmol PrRP increased (P = 0.0008 and 0.04) HP diet intake, but only 188 pmol PrRP was efficacious at increasing HC (P = 0.0011) and HF (P = 0.01) consumption compared with the vehicle. There was a diet effect on mRNA abundance of all genes (P < 0.05), with greater expression in chicks fed the HF or HP than the HC diet. Whereas neuropeptide Y (NPY) mRNA was similar between vehicle- and PrRP-injected chicks that consumed HP or HF diets, expression was greater (P < 0.05) in PrRP- than vehicle-injected chicks that consumed the HC diet. When chicks had access to all diets, 188 pmol PrRP caused preferential (P < 0.0001) intake of the HP over the HC and HF diets.


CONCLUSIONS
The HP diet enhanced the sensitivity of chicks to the food intake-stimulating effects of PrRP, and PrRP in turn increased preference for the HP diet. Thus, dietary macronutrient composition influences PrRP-mediated food intake, and PrRP in turn affects nutrient intake and transcriptional regulation in chicks.
Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA; and.
Guoqing
G
Wang
Department of Agrobiological Science, Faculty of Agriculture, Ehime University, Matsuyama, Japan.
Tetsuya
T
Tachibana
Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA; and.
Elizabeth R
ER
Gilbert
Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA; and macline2@vt.edu.
Mark A
MA
Cline
D000818:Animals; D001069:Appetite Regulation / Q000187:drug effects*; D019167:Appetite Stimulants / Q000008:administration & dosage / Q000494:pharmacology*; D002645:Chickens; D003433:Crosses, Genetic; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D004044:Dietary Proteins / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D002149:Energy Intake / Q000187:drug effects; D005518:Food Preferences; D018565:Food-Drug Interactions; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D007031:Hypothalamus / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D007276:Injections, Intraventricular; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009478:Neuropeptide Y / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D056690:Prolactin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D011897:Random Allocation; D051381:Rats; D015430:Weight Gain / Q000187:drug effects
D019167:Appetite Stimulants; D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D009478:Neuropeptide Y; C534379:Prlh protein, rat; D056690:Prolactin-Releasing Hormone
chicken; food intake; hypothalamus; macronutrient; prolactin-releasing peptide