l-Tryptophan Activates Mammalian Target of Rapamycin and Enhances Expression of Tight Junction Proteins in Intestinal Porcine Epithelial Cells  

Oleh:

Hao, Wang ; Yun, Ji ; Guoyao, Wu ; Kaiji, Sun ; Yuli, Sun

Jenis: Article from Journal - ilmiah internasional
Dalam koleksi: JN: The Journal of Nutrition vol. 145 no. 06 (Jun. 2015), page 1156-1162 .
Topik: tryptophan; cell proliferation; mammalian target of rapamycin; tight junction; intestinal epithelial cells; pig

Ketersediaan

Perpustakaan FK Nomor Panggil: J42.K Non-tandon: 1 (dapat dipinjam: 0) Tandon: tidak ada

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Isi artikel

Background: Besides serving as a substrate for protein synthesis, l-tryptophan (l-Trp) is used via serotonin-, kynurenine-, and niacin-synthetic pathways to produce bioactive compounds crucial for whole-body homeostasis. It is unknown whether l-Trp itself can regulate metabolic pathways in animal cells. Objective: This study tested the hypothesis that l-Trp may activate mammalian target of rapamycin (mTOR) complex 1 and enhance expression of tight junction (TJ) proteins in intestinal porcine epithelial cells. Methods: Jejunal enterocytes, intestinal porcine epithelial cell line 1 (IPEC-1) isolated from newborn pigs, were cultured in customized Dulbecco's modified Eagle medium (DMEM) supplemented with or without l-Trp for the indicated time periods. Cell proliferation, l-Trp metabolism, protein turnover, mRNA abundance for l-Trp transporters [solute carrier family 3 member 1 (SLC3A1), solute carrier family 6 member 14 (SLC6A14), solute carrier family 6 member 19 (SLC6A19), and Na+/K+ ATPase subunit-a1 (ATP1A1)], abundance of proteins involved in mTOR signaling, and TJ proteins were determined. Results: l-Trp was not degraded in IPEC-1 cells. Compared with basal medium containing 0.04 mmol/L l-Trp, 0.4 and 0.8 mmol/L l-Trp enhanced (P < 0.05) protein synthesis by 45–52% and cell growth by 17% and 25% on day 1 and 72% and 51% on day 2, respectively, while reducing (P < 0.05) protein degradation by 12% and 22%, respectively. These effects of l-Trp were associated with mTOR activation and increased (P < 0.05) mRNA abundance for l-Trp transporters (SLC6A19, SLC6A14, and SLC3A1) by 1.5–2.7 fold and ATP1A1 by 3 fold. l-Trp also upregulated (P < 0.05) the abundance of occludin, claudin-4, zonula occludens (ZO) 1 and 2 by 0.5–2 fold but did not affect expression of claudin-1 or ZO-3 in IPEC-1 cells. Conclusion: l-Trp is not catabolized by pig small intestinal epithelial cells but can regulate intracellular protein turnover and expression of TJ proteins in these cells.

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