Central Injection of Neuropeptide Y Affects Dietary Macronutrient Composition‐Mediated Changes in Broiler Adipose Tissue mRNA Abundance

Abstract

Neuropeptide Y (NPY) is a potent orexigenic (hunger increasing) factor that also promotes adipose tissue development in birds and mammals. The purpose of this study was to investigate how dietary macronutrient composition and exogenous NPY affect expression of lipid metabolism‐associated factors in different anatomical adipose (fat) depots of chickens. Chicks were fed one of three isocaloric diets (3,000 kcal metabolizable energy (ME)/kg) and isonitrogenous (22% crude protein; CP) corn and soybean meal‐based diets after hatch: high carbohydrate (HC; control), high fat (HF; 30% of ME from soybean oil) or high protein (HP; 27% CP) post hatch. On day 4 post hatch, 0.2 nmol of NPY or vehicle was injected intra cerebroventricularly (into left lateral ventricle) and abdominal and subcutaneous fat were collected at 1‐hour post injection. Total RNA was isolated, reverse transcribed and real‐time PCR performed to quantify expression of genes associated with adipogenesis: Krüppel‐like factor 7 (KLF7), GATA‐binding protein 2 (GATA 2), CCAAT/enhancer‐binding protein alpha (CEBPα), CEBPβ, peroxisome proliferator‐activated receptor gamma (PPARγ), sterol regulatory element‐binding transcription factor 1 (SREBP‐1), and fatty acid binding protein 4 (FABP4). The statistical model (within fat depot) included the main effects of diet and NPY treatment, and the two‐way interaction. There was an effect of diet (P < 0.05) for all of the genes measured in abdominal and subcutaneous fat, except for CEBPβ in subcutaneous fat. Chicks fed the HC diet expressed more (P < 0.0001) KLF7, CEBPα, CEBPβ, PPARγ, SREBP‐1, and FABP4 in abdominal fat than chicks fed the HF or HP diet. There were interactions of diet and NPY treatment on PPARγ (P = 0.04) and FABP4 (P = 0.03) mRNA in abdominal fat, and CEBPα (P = 0.01), PPARγ (P = 0.001), SREBP‐1 (P = 0.001) and FABP4 (P = 0.001) mRNA in subcutaneous fat. Pairwise comparison tests revealed that CEBPα (P < 0.003), PPARγ (P = 0.007), SREBP‐1 (P = 0.008) and FABP4 (P = 0.001) mRNA showed a more pronounced increase in subcutaneous fat of the HF than HC and HP fed chicks after NPY injection. PPARγ (P = 0.01), SREBP‐1 (P = 0.01) and FABP4 (P = 0.04) also showed a more accentuated decrease in subcutaneous fat of HC than HF and HP fed chicks after NPY injection. PPARγ (P = 0.003) and FABP4 (P = 0.003) in abdominal fat increased more in expression in HF than HC and HP fed chicks after NPY injection. These data demonstrate that consumption of diets differing in fat content affect adipose tissue physiology, with differences in gene expression of some adipogenesis‐associated factors during the first week post‐hatch; in general mRNA was greater in chicks fed HC than the HF or HP diet, with similar effects observed in different anatomical fat depots. Injection of NPY affected expression of these factors in an adipose depot‐dependent manner. These results may have implications for understanding how early‐life nutrition and appetite‐regulatory neuropeptides affect development of different adipose tissue depots in birds.Support or Funding InformationFunding for this work was provided in part, by the Virginia Agricultural Experiment Station and the Hatch Program of the National Institute of Food and Agriculture, U.S. Department of Agriculture, and by a John Lee Pratt Undergraduate Research Scholarship awarded to CW.