Total RNA was extracted from liquid-nitrogen-frozen jejuna using RNAiso plus (TaKaRa, Dalian, China) in accordance with the manufacturer's instructions. Meanwhile, RNA integrity and purity were assessed using 1% agarose gel electrophoresis and Nano Drop spectrophotometry (Nano Drop Technologies, Wilmington, DE, USA), respectively. Then, 1 μg of the total RNA was reverse transcribed using the PrimeScript® RT reagent Kit with gDNAEraser (TaKaRa, China) in compliance with the manufacturer's protocol. The generated cDNA was stored at −80°C until real-time PCR analysis.