Glutamine Enhances Tight Junction Protein Expression and Modulates Corticotropin-Releasing Factor Signaling in the Jejunum of Weanling Piglets
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BACKGROUND: Dysfunction of tight junction integrity is associated with decreased nutrient absorption and numerous gastrointestinal diseases in humans and piglets. Although l-glutamine has been reported to enhance intestinal-mucosal mass and barrier function under stressful conditions, in vivo data to support a functional role for l-glutamine on intestinal tight junction protein (TJP) expression in weanling mammals are limited. OBJECTIVE: This study tested the hypothesis that glutamine regulates expression of TJPs and stress-related corticotropin-releasing factor (CRF) signaling in the jejunum of weanling piglets. METHODS: Piglets were reared by sows or weaned at 21 d of age to a corn and soybean meal-based diet that was or was not supplemented with 1% l-glutamine for 7 d. Growth performance, intestinal permeability, TJP abundance, and CRF expression were examined. RESULTS: Weaning caused increases (P < 0.05) in intestinal permeability by 40% and in CRF concentrations by 4.7 times in association with villus atrophy (P < 0.05). Western blot analysis showed reductions (P < 0.05) in jejunal expression of occludin, claudin-1, zonula occludens (ZO) 2, and ZO-3, but no changes in the abundance of claudin-3, claudin-4, or ZO-1 in weanling piglets compared with age-matched suckling controls. Glutamine supplementation improved (P < 0.05) intestinal permeability and villus height, while reducing (P < 0.05) jejunal mRNA and protein levels for CRF and attenuating (P < 0.05) weanling-induced decreases in occludin, claudin-1, ZO-2, and ZO-3 protein abundances. CONCLUSION: Collectively, our results support an important role for l-glutamine in regulating expression of TJPs and CRF in the jejunum of weanling piglets.
author list (cited authors)
Wang, H., Zhang, C., Wu, G., Sun, Y., Wang, B., He, B., Dai, Z., & Wu, Z.