Leucine stimulates ASCT2 amino acid transporter expression in porcine jejunal epithelial cell line (IPEC-J2) through PI3K/Akt/mTOR and ERK signaling pathways

Abstract

Leucine has been shown to influence intestinal protein metabolism, cell proliferation and migration. Furthermore, our previous study demonstrated that branched-chain amino acids could modulate the intestinal amino acid and peptide transporters in vivo. As the possible mechanisms are still largely unknown, in the present work, we studied the transcriptional and translational regulation of leucine on amino acid transporter production in IPEC-J2 cells and the signaling pathways involved. Treatment of IPEC-J2 cells with 7.5 mM leucine enhanced the mRNA expression of the Na(+)-neutral AA exchanger 2 (ASCT2) and 4F2 heavy chain (4F2hc) and caused an increase in ASCT2 protein expression. Leucine also activated phosphorylation of 4E-BP1 and eIF4E through the phosphorylation of mTOR, Akt and ERK signaling pathways in IPEC-J2 cells. Pre-treatment of IPEC-J2 cells with inhibitors of mTOR and Akt (rapamycin and wortmannin) or an inhibitor of ERK (PD098059) for 30 min before leucine treatment attenuated the positive effect of leucine in enhancing the protein abundance of ASCT2. These results demonstrate that leucine could up-regulate the expression of the amino acid transporters (ASCT2) through transcriptional and translational regulation by ERK and PI3K/Akt/mTOR activation.

Structure of protein emulsion in food impacts intestinal microbiota, caecal luminal content composition and distal intestine characteristics in rats

“…Moreover, in porcine intestinal epithelial cells line, the addition of leucine up-regulated expression of Slc1a5, a gene that encodes for transport system ASC for neutral AA [55], in accordance with the present results which show increased expression of this latter gene in rats fed LFE diet. Thus, this supports our two aforementioned hypotheses: an increase AA supply in the ileum/cecum with the LFE diet and/or a longer transit time in the cecum that has been associated with increased protein degradation by the gut microbiota [56].…”

Maternal N-Carbamylglutamate Supplementation during Early Pregnancy Enhances Embryonic Survival and Development through Modulation of the Endometrial Proteome in Gilts

“…Total RNA extraction and realtime qRT-PCR was performed as described previously (27), with a Values are means 6 SEMs, n = 8 (control) or 7 (NCG). *P , 0.05, **P , 0.01 compared with the control group.…”

Novel metabolic and physiological functions of branched chain amino acids: a review

“…Supplementing 1.4 g L-leucine/kg body weight to breast-fed neonates improves intestinal development and increases the expression of neutral amino acid transporters (ATB 0,+ , B 0 AT1 and b 0,+ AT) [90]. In a study conducted in our lab, we demonstrated that meeting BCAA requirement (supplementing 0.1% L-Leu, 0.34% L-Val, and 0.19% L-Ile in 17% crude protein diet) is necessary for maintaining intestinal health and amino acid transporter expression [63], the latter of which might be through the PI3K/Akt/mTOR and ERK signaling pathways [91]. Interestingly, we found that leucine not only increased the expression of neutral amino acid transporters (ASCT2, rBAT and 4F2hc), but also cationic amino acid transporters (CAT1) which emphasizes the importance of BCAA in intestinal nutrient absorption.…”