The Effects of Dietary Macronutrient Composition on Lipid Metabolism‐Associated Factor Gene Expression in the Adipose Tissue of Chickens are Influenced by 3 Hours of Fasting

Abstract

Our objective was to determine how dietary macronutrient composition and fasting affect chick adipose tissue physiology during the early post‐hatch period. Broiler chicks were fed one of three isocaloric (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). At 4 days post hatch, chicks were fasted for 3 hours, and clavicular, gizzard and subcutaneous adipose depots were collected from fasted and fed chicks (n=10 per group). Total RNA was isolated, reverse transcribed and real‐time PCR performed to quantify 1‐acylglycerol‐3‐phosphate O‐acyltransferase 9 (AGPAT9), fatty acid binding protein 4 (FABP4), CCAAT/enhancer‐binding protein alpha (CEBPα), CEBPβ, peroxisome proliferator‐activated receptor gamma (PPARγ), monoglyceride lipase (MGLL), and sterol regulatory element‐binding transcription factor 1 (SREBP‐1) mRNA. The statistical model (within fat depot) included the main effects of diet and fasting, and the interaction. Means were separated within diet. There was greater CEBPα, PPARγ, and SREBP‐1, and less CEBPβ mRNA in clavicular, gizzard and subcutaneous fat in fasted than fed chicks (P < 0.05). In clavicular (P = 0.002) and subcutaneous (P = 0.01) fat, FABP4 expression was lower in chicks fed HP than HF or HC. In clavicular (P = 0.003) and gizzard (P = 0.009) fat, CEPBβ mRNA was greater in HF and HC than HP‐fed chicks. MGLL mRNA was greater (P = 0.007) in clavicular fat of HF than HP‐fed chicks. There were interactions of diet and fasting on PPARγ (P = 0.04) and SREBP‐1 (P = 0.008) in clavicular, PPARγ (P = 0.04) in gizzard, and CEBPα (P = 0.007) in subcutaneous fat. Post‐hoc testing revealed that CEBPα in subcutaneous (P < 0.003) and PPARg mRNA in gizzard (P < 0.03) fat showed a more pronounced decrease in expression during fasting in HC and HF than HP‐fed chicks. In clavicular fat, expression of AGPAT9 (P = 0.001), PPARg (P < 0.0001), and SREBP‐1 (P < 0.0001) mRNA decreased after 3 hours of fasting only in chicks that consumed the HC diet; expression was not affected by food withdrawal in chicks that consumed HF or HP. These data demonstrate that consumption of diets differing in fat and protein content affect gene expression of some lipid metabolism‐associated factors during the first week post‐hatch; in general mRNA was greater in chicks fed HC and HF than the HP diet, with similar effects observed in different anatomical fat depots. Fasting also influenced expression of these factors, in an adipose depot‐dependent manner. These results may have implications for understanding how early‐life nutrition affects 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 Fellowship awarded to Guoqing Wang.