Alpha-ketoglutarate suppresses the NF-κB-mediated inflammatory pathway and enhances the PXR-regulated detoxification pathway

Abstract

Alpha-ketoglutarate (AKG) is a critical nutritional factor in the maintenance of intestinal homeostasis. However, the relative mechanism of AKG has not been well understood. It was recently shown that the interaction between nuclear factor kappa B (NF-κB)-mediated inflammatory pathway and pregnane X receptor (PXR)-regulated detoxification pathway is a check and balance mechanism for keeping the homeostatic state of the intestine, preventing the onset of intestinal inflammation which may lead to cancer. In the current study we used lipopolysaccharide (LPS)-challenged piglet and intestinal porcine epithelial cells-J2 models to investigate the effects of dietary AKG supplementation on the intestinal immune system and PXR regulated target expression. We found that LPS induced significant activation of the NF-κB-mediated inflammatory pathway with concomitant impairment of intestinal nutrient absorption. AKG administration increased intracellular AKG and its metabolite concentrations and enhanced the mRNA expression of alpha-ketoglutarate dehydrogenase in vivo and in vitro. Thus dietary AKG supplementation reversed the adverse effects induced by LPS. We also found a strong inhibitory effects on the NF-κB-mediated inflammatory pathway, especially, in the AKG-treated intestinal tissues, LPS-induced NF-κB phosphorylation was inhibited and TNF-α was suppressed. Interestingly, AKG has potent effects in regulating the PXR and its downstream targets such as CYP3As and CYP2Bs in vivo and in vitro, although AKG is not a known PXR ligand. One potential mechanism for the up-regulation of the PXR pathway is through the down-regulation of NF-κB pathway which in turn de-represses the PXR-regulated target expression. Taken together, our results suggest that AKG improves intestinal immune system through modulating the interaction between PXR and NF-κB. Our findings have important implications for the prevention and treatment of intestinal inflammatory diseases in neonates.

Transcriptional Profiling Suggests Extensive Metabolic Rewiring of Human and Mouse Macrophages during Early Interferon Alpha Responses

“…Lactate accumulation in the microenvironment has been shown to suppress cytokine production and migration of human cytotoxic T cells [ 60 , 61 ]. Similarly, α -ketoglutarate has been shown to quell inflammatory processes by suppressing NF- κ B-mediated inflammatory pathways [ 62 ]. Succinate can also modulate inflammatory cytokine production.…”

Administration of alpha-ketoglutarate improves epithelial restitution under stress injury in early-weaning piglets

“…One of our recent studies demonstrates that AKG exert beneficial effects on the modulation of inflammatory cytokines such as IL-2 IL-8, IL-10, TGF-β, TNF-α and IL-17 [ 24 ], which have a negative influence on gut integrity and epithelial restitution when excessively secreted [ 6 ]. This is consistent with our findings that the addition of AKG inhibited the secretion and mRNA expression of IL-1β, IL-6, and IL-12 in the small intestine of LPS-induced piglets, indicating the possible anti-inflammatory effect of enteral supply of AKG during stress injury.…”

“…Recently, Chen et al (2015) reported that AKG lowered body weight and affected intestinal innate immunity through influencing intestinal microbiota in mice [ 27 ]. Of note, our group also found that AKG could suppress NF-κB-mediated inflammatory pathway and enhance the PXR-regulated detoxification pathway to improve intestinal immune and self-detoxification system [ 24 , 28 ]. It is further confirmed by our study that AKG as a precursor for the biosynthesis of glutamate and glutamine, inproved the secretion and expression of inflammatory cytokines in response to LPS stimulation, thereby increasing intestinal immunity.…”

“…LPS ( Escherichia coli serotype 055:B5; Sigma Chemical, Inc., St Louis, MO, USA) was dissolved in a sterile physiological solution. The administration dosages of AKG (Wuhan Yuancheng Gongchuang Technology co., LTD, Wuhan, Hubei, China; purity ≥ 99.2%) and LPS were adopted according to the previous experiment [ 24 ].…”

“…The location of ZO-1, Occludin, and E-cadherin in jejunum and ileum of piglets were determined using Immunohistochemical analysis as described by He et al (2017) [ 24 ]. Sections were incubated with the anti ZO-1 (1:75; Proteintech Group, Inc., Los Angeles, CA, USA), Occludin (1:100; Abcam, Cambridge, LON, UK), E-cadherin (1:150; Proteintech group.,Inc.).…”