The Effects Of α-Ketoglutarate On Growth And Metabolism Of Muscle And Intestinal Mucosa With Reference To The Molecular Mechanism In Piglets After Lipopolysaccharide Challenge

The study was conducted to investigate the effects ofα-ketoglutarate (AKG) on growth and metabolism of muscle and intestina mucosal with reference to the molecular mechanism in piglets chronically challenged with lipopolysaccharide. The immunological stress model was set up by repeatedly challenged with lipopolysaccharide (LPS) in piglets. Eighteen healthy crossbred (Duroc×Landrace×Yorkshire) piglets were randomly assigned into 3 treatment groups (6 replicates per group and one pig per replicate): control group, LPS group and AKG group. The control and LPS groups were fed the basal diet+1% starch, and the AKG group was fed with the basal diet+1% AKG. On d 10, 12, 14 and 16, the piglets in the LPS group and AKG group were injected intraperitoneally with LPS at 80μg/kg·BW, piglets in the control group were injected intraperitoneally with same dose of physiological saline. On d 10 and d 16, blood samples were collected 3 h after LPS challenge. All the piglets were sacrificed on d 17 to examine small intestinal mucosal morphology and collect gastrocnemius and intestinal mucosa for further analysis.1. The effects of AKG on blood biochemical measurements, levels of plasma hormones and inflammatory cytokines in piglets after LPS challenge.The results showed that: LPS challenge reduced globin and albumin / globin (P<0.05), increased plasma TNF-α(P<0.05) and IL-6 content (P<0.1), dietary supplementation of 1% AKG can alleviate the immunological stress induced by LPS challenge.2. The mechanism by which AKG exerted its growth-promoting effect and positive effects on protein synthesis in skeletal muscleThe results showed that: (1) LPS challenge reduced plasma insulin content (P<0.05), AKG supplementation alleviated the decline of insulin content induced by LPS challenge. (2) LPS challenge reduced the ratio of P-mTOR / mTOR and P-p70S6K / p70S6K (P<0.05) in gastrocnemius, AKG supplementation alleviated the decline of the ratio of P-mTOR / mTOR and P-p70S6K / p70S6K (P<0.05) induced by LPS challenge. These results indicated that dietary supplementation with 1% AKG can enhance insulin scretion and activate the mTOR signaling pathways in skeletal muscle of piglets.3. The mechanism by which AKG exerted its protective effects on intestinal structure and functionAll the piglets were sacrificed on d 17 to examine small intestinal mucosal morphology and mucosal DNA and protein contents. Expression of mTOR with phosphorylation, and heat shock protein 70 (HSP70) in intestinal mucosa were investigated by Western blot. The results showed that: (1) AKG supplementation significantly increased ratio of villus height to crypt depth in duodenum, jejunum and ileum, compared with the LPS group (P<0.05). (2) LPS challenge reduced the protein levels in duodenal, jejunal and ileal mucosa (P<0.05), AKG supplementation alleviated the decrease of protein content in duodenal (P<0.1), jejunal (P<0.05) and ileal mucosa (P<0.1) induced by LPS challenge. (3) HSP70 expression was higher in jejunal (P=0.044) and ileal mucosa (P=0.041) in the LPS group than in the AKG group. (4) Compared with the control group, phosphorylated mTOR to mTOR ratio (p-mTOR / mTOR) in duodenal, jejunal and ileal mucosa in LPS group decreased by 22.12% (P<0.1), 18.51% (P<0.05) and 23.06% (P<0.05) respectively, while significantly increased 47.15%, 46.52% and 26.10% (P<0.05) in the AKG group. These results indicated that dietary supplementation of 1% AKG alleviated the injury of intestinal morphology and inhibition of mTOR phosphorylation in intestinal mucosa in piglets caused by LPS challenge.In conclusion, dietary AKG supplementation may protect intestine structure and function by activating the mTOR signaling pathways in skeletal muscle and intestinal mucosa.