Dietary l-glutamine supplementation modulates microbial community and activates innate immunity in the mouse intestine
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This study was conducted to determine effects of dietary supplementation with 1 % l-glutamine for 14 days on the abundance of intestinal bacteria and the activation of intestinal innate immunity in mice. The measured variables included (1) the abundance of Bacteroidetes, Firmicutes, Lactobacillus, Streptococcus and Bifidobacterium in the lumen of the small intestine; (2) the expression of toll-like receptors (TLRs), pro-inflammatory cytokines, and antibacterial substances secreted by Paneth cells and goblet cells in the jejunum, ileum and colon; and (3) the activation of TLR4-nuclear factor kappa B (NF-κB), mitogen-activated protein kinases (MAPK), and phosphoinositide-3-kinases (PI3K)/PI3K-protein kinase B (Akt) signaling pathways in the jejunum and ileum. In the jejunum, glutamine supplementation decreased the abundance of Firmicutes, while increased mRNA levels for antibacterial substances in association with the activation of NF-κB and PI3K-Akt pathways. In the ileum, glutamine supplementation induced a shift in the Firmicutes:Bacteroidetes ratio in favor of Bacteroidetes, and enhanced mRNA levels for Tlr4, pro-inflammatory cytokines, and antibacterial substances participating in NF-κB and JNK signaling pathways. These results indicate that the effects of glutamine on the intestine vary with its segments and compartments. Collectively, dietary glutamine supplementation of mice beneficially alters intestinal bacterial community and activates the innate immunity in the small intestine through NF-κB, MAPK and PI3K-Akt signaling pathways.
KeywordsGlutamine Paneth cell Firmicutes NF-κB Innate immunity
Protein kinase B
RNase angiogenin 4
Mitogen-activated protein kinases
Myeloid differentiation factor-88
Nuclear factor kappa B
Regenerating islet-derived 3 gamma
Secretory group II A phospholipase A2
Tumor necrosis factor
This study was supported by the National Basic Research Program of China (2013CB127301, 2012CB124704, 2012CB126305), NSFC (31330075, 31101729, 31301989, 31101730, 31201813, 31301988), Hunan Provincial Natural Science Foundation of China (13JJ2034), Hunan Provincial Key Laboratory of Materials Protection for Electric Power and Transportation (No. 2013CL06), Changsha University of Science & Technology, P. R. China, Hubei Provincial Research and Development Program (Grant No. 2010BB023), Natural Science Foundation of Hubei Province (No. 2012FFB04805), Hubei One Hundred Talent Program, and Texas A&M AgriLife Research (H-82000).
Conflict of interest
The authors declare that they have no conflict of interests.
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