| Through setting up a stress model by repeatedly challenged with lipop- olysaccharide (LPS) in piglets, the experiment studied the effectsα-keto- glutaric acid (AKG) on growth performance and intestinal structure and function with reference to related mechanism, anticipated elucidate whe- ther AKG could alleviate growth inhibition and intestinal injury induced by LPS challenge in piglets.Twenty four healthy crossbred Duroc×(Landrace×Largewhite) weanling piglets (24±1 days-old, 7.25±0.23 kg BW) were randomly allocated to 3 treatments (control group, LPS group and AKG group). Each treatment 8 replicates, 1 piglet per replicate. The control and LPS group were fed the basal diet supplemented with 1% starch, while the AKG group was fed the basal diet supplemented with 1% AKG. Piglets in the LPS and AKG group were injected intraperitoneally with 80μg/kg·BW LPS on d 10, 12, 14 and 16, whereas piglets in the control group were injected with normal saline at the same dose. Blood samples were collected from precava vein at 3 h post-injection on d 10 and 16. On d 17, all piglets were injected with 50mg/kg·BW pentobarbital sodium, then killed under anesthesia.The samples of intestinal mucosa were collected, snap frozen in liquid nitrogen, then stored at -80℃until analysis.The measurements and results were as follows:(1) Effects of dietary supplementation of AKG on growth performance in piglets after LPS challengeAccording to the records of daily feed intake and the body weights on d 0, d 10 and d 17, average daily gain (ADG), average daily feed intake (ADFI) and the ratio of feed to gain (F/G) were calculated. Levels of cortisol, somatotrophin, insulin-like growth factor-1(IGF-1) and insulin in blood samples were assayed with radioimmunoassay.The results indicated that dietary supplementation with 1% AKG impr- oved ADG and F/G significantly (P<0.05), AKG relieved the negative effects on growth performance caused by LPS challenge. AKG could improve the levels of IGF-1 and insulin in blood post-injection on d 16, while AKG had no effects on the levels of cortisol and levels of insulin after the first injection of LPS.(2) Effects of AKG on intestinal structure and function in piglets after LPS challengeTo study effects of dietary supplementation of AKG on intestinal struc- ture and function in piglets after LPS challenge, DNA, RNA and protein i- n jejunal mucosa, the concentration of D-xylose in blood and the diamine- oxidase activity of Jejunal mucosa were measured.The results showed that the intestinal structure and function were dam- aged by LPS challenge, AKG could increase the protein, RNA/DNA, and protein/DNA (P<0.05) in jejunal mucosa, increase the concentration of D-xylose in blood (P<0.05) and DAO activity in jejunal mucosa (P< 0.05), decrease DAO activity in blood to some extent. These results indic- ate that AKG can alleviate intestinal injury caused by LPS challenge.(3) The mechanism of protective effects of AKG on intestinal structure and function after LPS challengeIn order to elucidate the mechanisms by which AKG exerted its protect- ive effects on intestinal structure and function, the experiment was cond- ucted to investigate the effects of AKG on the level of adenylate in intes- tinal mucosa,antioxidative ability and NO/NOS of jejunal mucosa.The energy metabolic function in intestinal mucosa was harmed by LPS challenge, dietary supplementation of 1%AKG could increase significant- ly the levels of ATP and total adenine nucleotide (TAN) in duodenal muc- osa and jejunal mucosa well as the level of energy charge (EC) in jejunal mucosa and ileal mucosa. AKG enhanced the intestinal antioxidative abil- ity by increasing the SOD activity and decreasing MDA content in jejunal mucosa. AKG maintained the balance of NO-NOS system in jejunal muco- sa, whereas NO content decreased (P <0.05) and NOS activity (P<0.05) increased in LPS group.In conclusion, through affecting the energy metabolism, antioxidative ability and NO/NOS system, AKG exert protective effects on intestinal mucosal structure and function after LPS challenge.
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