Partial Enteral Nutrition Mitigated Ischemia/Reperfusion-Induced Damage Of Rat Small Intestinal Barrier By Inhibiting NF-κB/HIF-1α SignalingPathway

I/R of the small intestine is a common event in abdominal surgery, trauma and major burn after fluid resuscitation. For patients undergoing intestinal IRI,total parenteral nutrition (TPN) is preferred commonly own to intolerance of full dose oral or enteral nutrition (EN). However, a lack of enteral nourishing may lead to reduced growth and functional development of the intestinal epithelium, which potentially results in hazard intraluminal content translocating to blood and lymph. The protective effect of enteral feeding in gut has been investigated in human and animal models of hemorrhage or viscera I/R in numerous studies. Especially under an IRI condition, loss of EN may aggravate intestinal epithelial barrier dysfunction. It has been postulated that the beneficial effects of minimal enteral feeding may result from the intestinal trophic effect of enteral nutrients. Indeed, it is confirmed that luminal nutrients stimulate intestinal growth and maintain mucosal integrity in adult and neonatal animals. Grossie et al demonstrated that a total EN infusion will prevent the delayed transit induced by non-lethal ischemia in a rat model. Ralls et al reported a loss of intestinal epithelial barrier function in enteral nutrient deprivation pediatric patients. In a TPN-mouse model, Yang et al found that TPN results in a loss of villus height, loss of epithelial cell proliferation, rise in cell apoptosis, and a marked decline in epithelial barrier function. In these studies, the doses of EN are either full or null. This may be insufficient to support the fact that a number of patients can tolerate low-dose EN, due to a partially digestive/absorptive function of gastrointestinal tract in the course of the disease. A previous large sample randomized controlled study indicate that a 6-days strategy of initial trophic EN compared with full EN was associated with less gastrointestinal intolerance for critical illness patients23. It is a consensus that EN should be used for patients as soon as it can be administrated safely. For intestinal I/R patients, however, the minimal dose of EN for effectively sustaining intestinal barrier function and the "trophic mechanism" was still controversial.In this stud, we perform different proportion of partial EN combined with supplementary PN in a rat model of preconditioned intestinal IRI. First, since PN without enteral feeding is associated with a greater risk of infection and impaired gut-derived immune responses compared with TEN, we hypothesize that the deficiency of enteral feeding causes the activation of NF-KB/HIF-1α signaling pathway in spite of completed reperfusion, in turn, leads to a disruption of intestinal mucosa barrier. Second, since TEN may hardly tolerated by quite a part of patients, we aim to investigate the relatively optimized dose of EN for maintaining the intestinal mucosa integrity. Furthermore, we hypothesize that EN may have a protective effect for intestinal barrier function/histological disruptions, at least in part, through the inhibition of the intestinal NF-KB/HIF-la signaling pathway in a rat model of intestinal I/R.PARTIEstablishing and observation in rats model of enteral nutrition for intestinal ischemia/reperfusionObjective:Established a stable and repeatable rats model of enteral nutrition (EN) for intestinal ischemia/reperfusion (I/R).Method:6-weeks old male SD rats were occluded the superior mesenteric artery for 30 minutes and then restore reperfusion. The stomach and jugular vein tubes for nutrition access were placed respectively. Rats were randomly divided into 6 groups (n=10) in each group after 12 h. and given different access of isocaloric nutrition treatments (chow, EN and PN). All the rats were sacrificed after 7 days, and the intestinal mucosa and liver morphology, serum biochemical index were analyzed.Results:EN can effectively improve proximal jejunum epithelial damage and liver histology, reduce the expression of NF-κB-p65 protein in ileum after intestinal I/R.Conclusion:EN is an ideal way for maintaining the integrity of the intestinal morphology, and promotes the restoration of intestinal epithelium after I/R injury.PART IIPartial Enteral Nutrition Improve I/R-Induced Damage of Rat Intestinal BarrierObjective:To investigate the protective effect of the optimum dose of EN in intestinal barrier funtion after I/R injury.Method:On the basis of rat model of intestinal I/R, Rats were randomly divided into 6 groups (n=15) in each group after 12 h. and given different proportion of enteral combined with parenteral nutrition (0%+100%、10%+90%、20%+80%、40%+60%、 60%+40%、100%+0%). The serum, mesenteric lymph nodes and intestinal mucosa samples were collected after 7 daysResults:Loss of EN after I/R disrupted the structure of intestinal epithelial cell and tight junctions (TJs). The intestinal NF-κB and HIF-1α were upregulated in TPN group.20%EN had a protective effect in intestinal barrier structure and function, and reduced the NF-κB/HIF-11α expression induced by I/R plus deficiency of EN.40%EN had a significantly improved effect in goblet cell function after I/R.Conclusion:20%EN protect the intestinal barrier by ameliorating intestinal permeability and TJ protein disruption, and 40%EN had an improved effect for goblet cell function after intestinal I/R in rats.PART III20%EN Improves the Intestinal Barrier Function by Inhibiting NF-κB/HIF-laPathway After I/RObjective:This study was designed to investigate the 20%EN attenuating I/R combined with loss of enteral feeding induced intestinal barrier dysfunction by inhibiting nuclear factor NF-κB/HIF-1 a pathway.Methods:50 male rats were preconditioned intestinal I/R and randomly divided into 5 groups:TEN group,20%EN+80%PN group, TPN group, TPN plus pretreated with NF-κB antagonist, TPN plus pretreated with HIF-1α antagonist.The NF-KB/HIF-laand claudin-1 protein, caspase-3 were tested. And the differences of barrier function, inflammatory cytokine levels and antioxidant capacity between groups were analyzed.Results:Compared with TPN, and TPN plus antagonist,20%EN had an irreplaceably protective effect in intestinal barrier function, and reduced the NF-κB/HIF-1α expression induced by deficiency of EN. In addition,20%EN may have a potential anti-apoptosis effect for intestinal epithelial cell after I/R. No statistical difference is found between 20%EN and TEN in all the tested parameter.Conclusion:We found that 20%EN conserved intestinal barrier function in terms of ameliorating intestinal permeability, increasing TJ protein expression and improving antioxidant ability after I/R. And this effect, at least partly, induced by inhibition of NF-κB/HIF-1 aPathway.