Differential expression of proteins involved in energy production along the crypt-villus axis in early-weaning pig small intestine.

Weaning of piglets reflects intestinal dysfunction and atrophy and affected the physiological state of enterocytes. However, few studies have defined physiological state of enterocytes along the crypt-villus axis in early-weaning piglets. A total of 16 piglets from 8 litters were used in the experiment. One group of piglets was nursed by sows until age 21 days, and another group was weaned at age 14 days and then fed creep feed instead of breast milk for 7 days. Piglets were killed at 21 days, and the jejunum segments were dissected. After sequential isolation of jejunum epithelial cells along the crypt-villus axis, their proteins were analyzed through the isobaric tags for relative and absolute quantification, and proteins involved in the mammalian target of rapamycin signaling pathway and proliferating cell nuclear antigen abundances in jejunal epithelial cells of weaning or suckling group were determined by Western blotting. The differential proteins in three cell fractions were identified and analyzed. The results showed that proteins involved in the tricarboxylic acid cycle, β-oxidation, and the glycolysis pathway were significantly downregulated in the upper and middle villus of the early-weaned group. However, proteins involved in glycolysis were significantly upregulated in crypt cells. In addition, Western blot analysis showed that the expression of mammalian target of rapamycin pathway-related proteins was decreased (P < 0.05) in the early-weaned group. The present results showed that early-weaning differentially affect the expression of proteins involved in energy production of enterocytes along the jejunal crypt-villus axis.