Alpha-ketoglutarate suppresses the NF-κB-mediated inflammatory pathway and enhances the PXR-regulated detoxification pathway
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Liuqin He1,2,*, Huan Li3,*, Niu Huang3, Xihong Zhou1, Junquan Tian1,2, Tiejun Li1,4, Jing Wu3, Yanan Tian5, Yulong Yin1,4 and Kang Yao1,4
1Key Laboratory of Agro-Ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Hunan Provincial Engineering Research Center for Healthy Livestock and Poultry Production, Changsha, Hunan 410125, China
2University of Chinese Academy of Sciences, Huairou, Beijing 10008, China
3College of Animal Science and Technology, Hunan Agricultural University, Hunan, Changsha 410128, China
4Hunan Co-Innovation Center of Animal Production Safety, Hunan, Changsha 410128, China
5Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station, TX 77843, USA
*These authors have contributed equally to this work
Yulong Yin, email: [email protected]
Kang Yao, email: [email protected]
Yanan Tian, email: [email protected]
Keywords: AKG, pregnane X receptor, NF-κB, CYP450, intestinal inflammation
Received: January 28, 2017 Accepted: March 17, 2017 Published: April 06, 2017
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.
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