Magnolol attenuates sepsis-induced gastrointestinal dysmotility in rats by modulating inflammatory mediators

AIM： To investigate the protective effects of magnolol on sepsis-induced inflammation and intestinal dysmotility. METHODS： Sepsis was induced by a single intraperitoneal injection of lipopolysaccharide （LPS）. Male Wistar rats were randomly assigned to one of three treatment groups： magnolol prior to LPS injection （LPS/Mag group）; vehicle prior to LPS injection （LPS/Veh group）; vehicle prior to injection of saline （Control/Veh）. Intestinal transit and circular muscle mechanical activity were assessed 12 h after LPS injection. Tumor necrosis factor-α （TNF-α）, interleukin-10 （IL-10）, monocyte chemoattractant protein-1 （MCP-1） and inducible nitric oxide synthase （iNOS） mRNA in rat ileum were studied by RT-PCR 2 h after LPS injection. Nuclear factor-κB （NF-κB） activity in the intestine was also investigated at this time using electrophoretic mobility shift assay. In addition, antioxidant activity was determined by measuring malondialdehyde （MDA） concentration and superoxide dismutase （SOD） activity in the intestine 2 h after LPS iniection.RESULTS： Magnolol significantly increased intestinal transit and circular muscle mechanical activity in LPS- treated animals. TNF-α, MCP-1 and iNOS mRNA expression in the small intestine were significantly reduced after magnolol treatment in LPS-induced septic animals, compared with untreated septic animals. Additionally,magnolol significantly increased IL-10 mRNA expression in septic rat ileum. Magnolol also significantly suppressed NF-κB activity in septic rat intestine. In addition, magnolol significantly decreased MDA concentration and increased SOD activity in rat ileum. CONCLUSION： Magnolol prevents sepsis-induced suppression of intestinal motility in rats. The potential mechanism of this benefit of magnolol appears to be modulation of self-amplified inflammatory events and block of oxidative stress in the intestine.     

Effects ofSalmonella infection on hepatic damage following acute liver injury in rats

BACKGROUND: Acute liver injury is a common clinical disor-der associated with intestinal barrier injury and disturbance of intestinal microbiota. Probiotic supplementation has been reported to reduce liver injury; however, it is unclear whether enteropathogen infection exacerbates liver injury. The pur-pose of this study was to address this unanswered question using a rat model.
METHODS: Oral supplementation withSalmonella enterica serovar enteritidis (S. enteritidis) was given to rats for 7 days. Different degrees of acute liver injury were then induced by intraperitoneal injection of D-galactosamine. The presence and extent of liver injury was assayed by measuring the con-centrations of serum alanine aminotransferase, aspartate aminotransferase, and total bilirubin. Histology was used to observe liver tissue damage. Additionally, we measured the changes in plasma endotoxin, serum cytokines and bacterial translocation to clarify the mechanisms underlying intestinal microbiota associated liver injury.
RESULTS: The levels of liver damage and endotoxin were sig-niifcantly increased in theSalmonella infected rats with severe liver injury compared with the no infection rats with severe liver injury (P<0.01); The peyer’s patch CD3+ T cell counts were increased signiifcantly when theSalmonellainfection with severe injury group was compared with the normal group (P<0.05).S. enteritidis pretreatment enhanced intestinal bar-rier impairment and bacterial translocation.
CONCLUSIONS: OralS. enteritidis administration exacer-bates acute liver injury, especially when injury was severe. Major factors of the exacerbation include inlfammatory and oxidative stress injuries induced by the translocated bacteria and associated endotoxins, as well as over-activation of the immune system in the intestine and liver.     

Effect of prolonged omeprazole administration on segmental intestinal Mg~(2+) absorption in male Sprague-Dawley rats

BACKGROUND The exact mechanism of proton pump inhibitors(PPIs)-induced hypomagnesemia(PPIH) is largely unknown. Previous studies proposed that PPIH is a consequence of intestinal Mg~(2+) malabsorption. However, the mechanism of PPIs-suppressed intestinal Mg~(2+) absorption is under debate.AIM To investigate the effect of 12-wk and 24-wk omeprazole injection on the total,transcellular, and paracellular Mg~(2+) absorption in the duodenum, jejunum, ileum,and colon of male Sprague-Dawley rats.METHODS The rats received 20 mg/kg·d subcutaneous omeprazole injection for 12 or 24 wk.Plasma and urinary Mg~(2+), Ca~(2+), and PO_4~(3-)levels were measured. The plasma concentrations of 1α,25-dihydroxyvitamin D3(1α,25(OH)_2D_3), parathyroid hormone(PTH), fibroblast growth factor 23(FGF-23), epidermal growth factor(EGF), and insulin were also observed. The duodenum, jejunum, ileum, and colon of each rat were mounted onto individual modified Using chamber setups to study the rates of total, transcellular, and paracellular Mg~(2+) absorption simultaneously. The expression of transient receptor potential melastatin 6(TRPM6) and cyclin M4(CNNM4) in the entire intestinal tract was also measured.RESULTS Single-dose omeprazole injection significantly increased the intraluminal p H of the stomach, duodenum, and jejunum. Omeprazole injection for 12 and 24 wk induced hypomagnesemia with reduced urinary Mg~(2+) excretion. The plasma Ca~(2+) was normal but the urinary Ca~(2+) excretion was reduced in rats with PPIH. The plasma and urinary PO_4~(3-)levels increased in PPIH rats. The levels of1α,25(OH)_2D_3 and FGF-23 increased, whereas that of plasma EGF decreased in the omeprazole-treated rats. The rates of the total, transcellular, and paracellular Mg~(2+) absorption was significantly lower in the duodenum, jejunum, ileum, and colon of the rats with PPIH than in those of the control rats. The percent suppression of Mg~(2+) absorption in the duodenum, jejunum, ileum, and colon of the rats with PPIH compared with the control rats was 81.86%, 70.59%, 69.45%,and 39.25%, respectively. Compared with the control rats, the rats with PPIH had significantly higher TRPM6 and CNNM4 expression levels throughout the intestinal tract.CONCLUSION Intestinal Mg~(2+) malabsorption was observed throughout the intestinal tract of rats with PPIH. PPIs mainly suppressed small intestinal Mg~(2+) absorption. Omeprazole exerted no effect on the intraluminal acidic pH in the colon. Thus, the lowest percent suppression of total Mg~(2+) absorption was found in the colon. The expression levels of TRPM6 and CNNM4 increased, indicating the presence of a compensatory response to Mg~(2+) malabsorption in rats with PPIH. Therefore, the small intestine is an appropriate segment that should be modulated to counteract PPIH.     

Intestinal barrier damage caused by trauma and lipopolysaccharide

AIM:To investigate the intestinal barrier function damageinduced by trauma and infection in rats.METHODS:Experimental models of surgical trauma andinfection were established in rats.Adult Sprague-Dawleyrats were divided into 4 groups:control group (n=8),ENgroup (n=10),PN group (n=9) and Sep group (n=8).The rats in PN and Sep groups were made into PN modelsthat received isonitrogenous,isocaloric and isovolumic TPNsolution during the 7-d period.Rats in EN and Sep groupsreceived laparotomy and cervical catheterization on day1 and received lipopolysaccharide injection intraperitoneallyon d 7.On the 7~(th) day all the animals were garaged withlactulose and mannitol to test the intestinal permeability.Twenty-four hours later samples were collected and examined.RESULTS:The inflammatory responses became graduallyaggravated from EN group to Sep group.The mucosalstructure of small intestine was markedly impaired in PNand Sep groups.There was a low response in IgA level inSep group when compared with that of EN group.Lipopolysaccharide injection also increased the nitric oxidelevels in the plasma of the rats.The intestinal permeabilityand bacterial translocation increased significantly in Sepgroup compared with that of control group.CONCLUSION:One wk of parenteral nutrition causes anatrophy of the intestinal mucosa and results in a moderateinflammatory reaction in the rats.Endotoxemia aggravatsthe inflammatory responses that caused by laparotomyplus TPN,increases the production of nitric oxide in thebody,and damages the intestinal barrier function.     

Role of neuronal nitric oxide synthase and inducible nitric oxide synthase in intestinal injury in neonatal rats

AIM: To investigate the dynamic change and role of neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) in neonatal rat with intestinal injury and to define whether necrotizing enterocolitis (NEC) is associated with the levels of nitric oxide synthase (NOS) in the mucosa of the affected intestine tissue. METHODS: Wistar rats less than 24 h in age received an intraperitoneal injection with 5 mg/kg lipopolysaccharide (IPS). Ileum tissues were collected at 1, 3, 6, 12 and 24 h following LPS challenge for histological evaluation of NEC and for measurements of nNOS and iNOS. The correlation between the degree of intestinal injury and levels of NOS was determined. RESULTS: The LPS-injected pups showed a significant increase in injury scores versus the control. The expression of nNOS protein and mRNA was diminished after LPS injection. There was a negative significant correlation between the nNOS protein and the grade of median intestinal injury within 24 h. The expression of iNOS protein and mRNA was significantly increased in the peak of intestinal injury. CONCLUSION: nNOS and iNOS play different roles in LPS-induced intestinal injury. Caution should be exerted concerning potential therapeutic uses of NOS inhibitors in NEC.     

Antibody to eosinophil cationic protein suppresses dextran sulfate sodium-induced colitis in rats

AIM: To produce an antibody against rat eosinophil cationic protein (ECP) and to examine the effects of the antibody in rats with dextran sulfate sodium (DSS)-induced colitis. METHODS: An antibody was raised against rat ECP. Rats were treated with 3% DSS in drinking water for 7 d and received the antibody or normal serum. The colons were examined histologically and correlated with clinical symptoms. Immunohistochemistry and Western blot analysis were estimated as a grade of inflammation. RESULTS: The ECP antibody stained the activated eosinophils around the injured crypts in the colonic mucosa. Antibody treatment reduced the severity of colonic ulceration and acute clinical symptoms (diarrhea and/or bloodstained stool). Body weight gain was significantly greater and the colon length was significantly longer in anti-ECP-treated rats than in normal serum-treated rats. Expression of ECP in activated eosinophils was associated with the presence of erosions and inflammation. The number of Ki-67-positive cells in the regenerated surface epithelium increased in anti-ECP-treated rats compared with normal serum-treated rats. Western blot analysis revealed reduced expression of macrophage migration inhibitory factor (MIF) in anti-ECP-treated rats. CONCLUSION: Our results indicate that treatment with ECP antibody, improved DSS-induced colitis in rats, possibly by increasing the regenerative activity of the colonic epithelium and downregulation of the immune response, and suggest that anti-ECP may promote intestinal wound healing in patients with ulcerative colitis (UC).     

Glutamine synthetase activity and glutamate uptake in hippocampus and frontal cortex in portal hypertensive rats

AIM： To study glutamine synthetase （GS） activity and glutamate uptake in the hippocampus and frontal cortex （FC） from rats with prehepatic portal vein hypertension.
METHODS： Male Wistar rats were divided into shamoperated group and a portal hypertension （PH） group with a regulated stricture of the portal vein. Animals were sacrificed by decapitation 14 d after portal vein stricture. GS activity was determined in the hippocampus and FC. Specific uptake of radiolabeled L-glutamate was studied using synaptosome-enriched fractions that were freshly prepared from both brain areas.
RESULTS： We observed that the activity of GS increased in the hippocampus of PH rats, as compared to control animals, and decreased in the FC. A significant decrease in glutamate uptake was found in both brain areas, and was more marked in the hippocampus. The decrease in glutamate uptake might have been caused by a deficient transport function, significantly and persistent increase in this excitatory neurotransmitter activity.
CONCLUSION： The presence of moderate ammonia blood levels may add to the toxicity of excitotoxic glutamate in the brain, which causes alterations in brain function. Portal vein stricture that causes portal hypertension modifies the normal function in some brain regions.     

Intestinal permeability of metformin using single-pass intestinal perfusion in rats

AIM: To characterize the intestinal transport and mechanism of metformin in rats and to investigate whether or not metformin is a substrate for P-glycoprotein (P-gp). METHODS: The effective intestinal permeability of metformin was investigated using single-pass intestinal perfusion (SPIP) technique in male Waster rats. SPIP was performed in three isolated intestinal segments (duodenum, jejunum and ileum) at the same concentration of metformin (50μg/mL) to test if the intestinal transport of metformin exhibited site-dependent changes, and in a same isolated intestinal segment (duodenal segment) at three different concentrations of metformin (10, 50, 200μg/mL) to test if the intestinal transport of metformin exhibited concentration-dependent changes. Besides, P-gp inhibitor verapamil (400μg/mL) was co-perfused with metformin (50μg/mL) in the duodenum segment to find out if the intestinal absorption of metformin was affected by P-gp exiting along the gastrointestinal track. Stability studies were conducted to ensure that the loss of metformin could be attributed to intestinal absorption. RESULTS: The effective permeability values (Peff) of metformin in the jejunum and ileum at 50μg/mL were significantly lower than those in the duodenum at the same concentration. Besides, Peff values in the duodenum at high concentration (200μg/mL) were found to be significantly lower than those at low and medium concentrations (10 and 50μg/mL). Moreover the co-perfusion with verapamil did not increase the Pen value of metformin at 50μg/mL in the duodenum. CONCLUSION: Metformin could be absorbed from the whole intestine, with the main absorption site at duodenum. This concentration-dependent permeability behavior in the duodenum indicates that metformin is transported by both passive and active carrier-mediated satu-rable mechanism. The Peff value can not be increased by co-perfusion with verapamil, indicating that absorption of metformin is not efficiently transported by P-gp in the gut wall. Furthermore metformin is neither a substrate nor an inducer of P-gp. Based on the Peff values obtained in the present study and using established relationships, the human fraction dose absorbed for metformin is estimated to be 74%-90% along human intestine.     

Possible ameliorative effect of breastfeeding and the uptake of human colostrum against coeliac disease in autistic rats

AIM: To examine the possible ameliorative effect of breastfeeding and the uptake of human colostrum against coeliac disease in autistic rats. METHODS: Female rats were fed a standard diet and received a single intraperitoneal injection of 600 mg/kg sodium valproate on day 12.5 after conception. In study 1, neonatal rats were randomly subjected to blood tests to investigate autism. In study 2, the 1st group was fed by the mother after an injection of interferon-γ (IFN-γ) and administration of gliadin. The pups in the 2nd group were prevented from accessing maternal milk, injected IFN-γ, administered gliadin, and hand-fed human colostrum. The normal littermates fed by the table mothers were injected with physiological saline and served as normal controls in this study.RESULTS: The protein concentration was higher in group 2 than in group 1 in the duodenum (161.6 ± 9 and 135.4 ± 7 mg/g of tissue, respectively, P < 0.01). A significant increase (P < 0.001) in body weight was detected in human colostrum-treated pups on post natal day (PND) 7 and 21 vs suckling pups in group 1. A delay in eye opening was noticed in the treated rats in group 1 on PND 13 compared with the control group and group 2. Administration of a single intraperitoneal injection of 600 mg/kg sodium valproate on day 12.5 after conception resulted in significantly reduced calcium and vitamin D levels in study 1 compared with the control groups (P < 0.001). However, human colostrum uptake inhibited increases in the level of transglutaminase antibody in autistic pups with coeliac disease. CONCLUSION: The effects of early-life nutrition and human colostrum on the functional maturation of the duodenal villi in autistic rats with coeliac disease that might limit or prevent the coeliac risk with autism.     

Abdominal paracentesis drainage attenuates intestinal inflammation in rats with severe acute pancreatitis by inhibiting the HMGB1-mediated TLR4 signaling pathway

BACKGROUND Our previous studies confirmed that abdominal paracentesis drainage(APD)attenuates intestinal mucosal injury in rats with severe acute pancreatitis(SAP),and improves administration of enteral nutrition in patients with acute pancreatitis(AP).However,the underlying mechanisms of the beneficial effects of APD remain poorly understood.AIM To evaluate the effect of APD on intestinal inflammation and accompanying apoptosis induced by SAP in rats,and its potential mechanisms.METHODS SAP was induced in male adult Sprague-Dawley rats by 5%sodium taurocholate.Mild AP was induced by intraperitoneal injections of cerulein(20μg/kg body weight,six consecutive injections).Following SAP induction,a drainage tube connected to a vacuum ball was placed into the lower right abdomen of the rats to build APD.Morphological changes,serum inflammatory mediators,serum and ascites high mobility group box protein 1(HMGB1),intestinal barrier function indices,apoptosis and associated proteins,and toll-like receptor 4(TLR4)signaling molecules in intestinal tissue were assessed.RESULTS APD significantly alleviated intestinal mucosal injury induced by SAP,as demonstrated by decreased pathological scores,serum levels of D-lactate,diamine oxidase and endotoxin.APD reduced intestinal inflammation and accompanying apoptosis of mucosal cells,and normalized the expression of apoptosis-associated proteins in intestinal tissues.APD significantly suppressed activation of the intestinal TLR4 signaling pathway mediated by HMGB1,thus exerting protective effects against SAP-associated intestinal injury.CONCLUSION APD improved intestinal barrier function,intestinal inflammatory response and accompanying mucosal cell apoptosis in SAP rats.The beneficial effects are potentially due to inhibition of HMGB1-mediated TLR4 signaling.     

Hormonal regulation of dipeptide transporter （PepT1） in Caco-2 cells with normal and anoxia／reoxygenation management

AIM: To determine the regulation effects of recombinant human growth hormone (rhGH) on dipeptide transporter(PepT1) in Caco-2 cells with normal culture and anoxia/reoxygenation injury. METHODS: A human intestinal cell monolayer (Caco-2) was used as the in vitro model of human small intestine and cephalexin as the model substrate for dipeptide transporter (PepT1). Caco-2 cells grown on Transwell membrane filters were preincubated in the presence of rhGH in the culture medium for 4 d, serum was withdrawn from monolayers for 24 h before each experiment. The transport experiments of cephalexin across apical membromes were then conducted; Caco-2 cells grown on multiple well dishes (24 pore) with normal culture or anoxia/reoxygenation injury were preincubated with rhGH as above and uptake of cephalexin was then measured. RESULTS: The transport and uptake of cephelaxin across apical membranes of Caco-2 cells after preincubation with rhGH were significantly increased compared with controls (P=0.045, 0.0223). Also, addition of rhGH at physiological concentration (34 nM) to incubation medium greatly stimulates cephalexin uptake by anoxia/reoxygenation injuried Caco-2 cells (P=0.0116), while the biological functions of PepT1 in injured Caco-2 cells without rhGH were markedly downregulated. Northern blot analysis showed that the level of PepT1 mRNA of rhGH-treated injured Caco-2 cells was greatly increased compared to controls. CONCLUSION: The present results of rhGH stimulating the uptake and transport of cephalexin indicated that rhGH greatly upregulates the physiological effects of dipeptide transporters of Caco-2 cells. The alteration in the gene expression may be a mechanism of regulation of PepT1. In addition, Caco-2 cells take up cephalexin by the Proton-dependent dipeptide transporters that closely resembles the transporters present in the intestine. Caco-2 cells represent an ideal cellular model for future studies of the dipeptide transporter.     

生长激素对脑出血大鼠血清白蛋白含量和小肠黏膜形态学的影响

目的 评价重组人生长激素(recombinant human growth hormom,rhGH)对脑出血大鼠血清白蛋白水平和小肠黏膜形态学的影响.方法 采用自体血注射法制作大鼠脑出血模型.56只SD大鼠分为假手术组(n=8),rhGH组(n=24;腹腔注射rhGH,1 U/kg,1次/d)和生理盐水对照组(n=24;腹腔注射等量生理盐水,1次/d),后两组均分别再分为术后1、7和14 d组(每组n=8).检测各组大鼠不同时问点血清白蛋白浓度,HE染色和图像分析观察小肠黏膜形态学改变.结果 脑出血各时间点,生理盐水对照组血清白蛋白水平均较假手术组显著降低(P均<0.01);rhGH组血清白蛋白水平随治疗进程逐渐增高,但仅在14 d时显著高于生理盐水对照组[(39.93±1.98)g,L对(37.93±1.57)g,L,P<0.01].脑出血后1 d和7 d时,rhGH组小肠绒毛高度和黏膜厚度与生理盐水对照组无显著差异,但14 d时显著增高(P<0.01).脑出血后1、7和14 d小肠绒毛面积进行性缩小,且rhGH组较生理盐水对照组随治疗进程进行性增高(P<0.01).脑出血后1 d和7 d.rhGH组肠腺深度较生理盐水对照组增高(P<0.01),但14 d时无显著差异;脑出血1 d,rhGH组组肠腺密度较生理盐水对照组显著增高(P<0.01),7 d时增高不显著,14 d时不仅不增反而稍有降低.结论 脑出血大鼠血清白蛋白水平较假手术组显著下降;脑出血可引起小肠黏膜损害.rhGH可提高脑出血大鼠血清白蛋白水平,不论在脑出血早期还是后期均可不同程度减轻小肠黏膜损伤,后期改善更为显著.rhGH对小肠黏膜损伤的改善程度与血清白蛋白水平的升高程度呈正相关.     

重组生长激素与谷氨酰胺协同促进短肠大鼠小肠的代偿

目的　研究添加生长激素(rhGH)及谷氨酰胺(Gln)的肠外营养(PN)对短肠大鼠残存小肠代偿的作用及机制。方法　按2×2析因实验方案,将SD大鼠随机分成STD、Gln、rhGH及rhGH+Gln组,建立PN短肠动物模型。PN6d后行小肠黏膜形态学检查,并行细胞增殖核心抗原(PCNA)测定、原位末端标记(TUNEL)染色及胰岛素样生长因子-1(IGF-1)mRNA的Northernb1ot测定。结果　rhGH+Gln组残余小肠黏膜形态学上呈显著代偿表现。析因分析表明,rhGH与Gln间存在协同作用(P＜0.01)。其PCNA表达显著高于rhGH、Gln与STD组,分别为24.95±3.93、19.28±3.25、17.27±3.38与8.37±2.23(P＜0.01);凋亡指数显著降低,分别为5.68±2.07、8.06±2.33、10.00±2.24及22.32±3.84(P＜0.01);小肠IGF-1mRNA表达在rhGH+Gln组显著高于rhGH、Gln及STD组,分别为0.73±0.05、0.62±0.04、0.51±0.04及0.41±0.22(P＜0.05)。结论　rhGH与Gln通过促进肠黏膜上皮细胞增生与抑制其凋亡,协同促进短肠大鼠残存小肠代偿,小肠IGF-1在二者协同作用的发挥中起重要的介导作用。     

Clinical relevance of intestinal peptide uptake

AIM: To determine available information on an independent peptide transporter 1(Pep T1) and its potential relevance to treatment, this evaluation was completed.METHODS: Fully published English language literature articles sourced through Pub Med related to protein digestion and absorption, specifically human peptide and amino acid transport, were accessed and reviewed.Papers from 1970 to the present, with particular emphasis on the past decade, were examined. In addition,abstracted information translated to English in Pub Med was also included. Finally, studies and reviews relevant to nutrient or drug uptake, particularly in human intestine were included for evaluation. This work represents a summary of all of these studies with particular reference to peptide transporter mediated assimilation of nutrients and pharmacologically active medications.RESULTS: Assimilation of dietary protein in humans involves gastric and pancreatic enzyme hydrolysis to luminal oligopeptides and free amino acids. During the ensuing intestinal phase, these hydrolytic products are transported into the epithelial cell and, eventually, the portal vein. A critical component of this process is the uptake of intact di-peptides and tri-peptides by an independent Pep T1. A number of "peptide-mimetic" pharmaceutical agents may also be transported through this carrier, important for uptake of different antibiotics, antiviral agents and angiotensin-converting enzyme inhibitors. In addition, specific peptide products of intestinal bacteria may also be transported by Pep T1, with initiation and persistence of an immune response including increased cytokine production and associated intestinal inflammatory changes. Interestingly, these inflammatory changes may also be attenuated with orallyadministered anti-inflammatory tripeptides administered as site-specific nanoparticles and taken up by this Pep T1 transport protein. CONCLUSION: Further evaluation of the role of this transporter in treatment of intestinal disorders, including inflammatory bowel disease is needed.     

Functional and molecular expression of intestinal oligopeptide transporter (Pept-1) after a brief fast.

The intestinal oligopeptide transporter, cloned as Pept-1, has major roles in the assimilation of dietary proteins and absorption of peptidomimetic medications. The initial aim of the present experiment was to investigate whether the functional expression of this transporter is affected by dietary intake. Functional expression was determined as the rate of uptake of glycylglutamine (Gly-Gln) by brush-border membrane vesicles (BBMVs) prepared from the jejunum of fed and fasted rats. Surprisingly, the rate of dipeptide uptake was greatly increased after 1 day of fasting. The subsequent aim of the experiment became the investigation of the mechanism of this alteration in transport, which showed that 1 day of fasting increased (1) the maximal Gly-Gln uptake (Vmax) by twofold without changing the Km of Gly-Gln uptake by BBMVs, (2) the amount of intestinal oligopeptide transporter (Pept-1) protein by threefold in the brush-border membrane, and (3) the abundance of Pept-1 mRNA by threefold in the intestinal mucosa. We conclude that 1 day of fasting increases dipeptide transport in rat intestine by increasing the population of Pept-1 in the brush-border membrane. The mechanism appears to be an increase in Pept-1 gene expression.     

Recombinant human growth hormone and glutamine synergistically improve the adaptation of the remnant small intestine in rats with short bowel syndrome

OBJECTIVE : To study the effects and the underlying mechanism of recombinant human growth hormone (rhGH) and glutamine (Gln) on the adaptation of the remnant small intestine in parenterally nourished, short bowel syndrome (SBS) rats. METHOD : Four parenteral nutrition (PN) treatment groups of SBS rats were randomly arranged in a 2 × 2 factorial design as follows: (i) STD (standard PN) group (–rhGH, –Gln); (ii) Gln group (–rhGH, +Gln); (iii) rhGH group (+rhGH, –Gln); and (iv) rhGH + Gln group (+rhGH, +Gln). Morphological changes of the intestinal mucosa were investigated and the expression of proliferating cell nuclear antigen (PCNA) and the occurrence of apoptosis were observed by immunohistochemical staining and terminal deoxynucleotidyl transfer‐mediated dUTP‐biotin nick end‐labeling (TUNEL) methods. The level of intestinal insulin‐like growth factor‐1 (IGF‐1) mRNA was determined by northern blotting. RESULTS : The mucosal thickness, villous height, crypt depth and villous surface area of the remnant small intestine in the rhGH + Gln group were increased significantly as compared with the other three experimental groups, and there were synergistic effects between rhGH and Gln (P < 0.01). The expression of PCNA was higher in the rhGH + Gln group than in the rhGH, Gln and STD groups (24.95 ± 3.93 vs 19.28 ± 3.25, 17.27 ± 3.38, and 8.37 ± 2.23 positive cells per crypt of Lieberkuhn, respectively; P < 0.01) but the rate of apoptosis was lower in the rhGH + Gln group than in the rhGH, Gln and STD groups (5.68 ± 2.07 vs 8.06 ± 2.33, 10.00 ± 2.24 and 22.32 ± 3.84 positive cells per 100 cells, respectively; P < 0.01). The intestinal IGF‐1 mRNA was also expressed at a higher level in the rhGH + Gln group than in the rhGH, Gln and STD groups (0.73 ± 0.05 vs 0.62 ± 0.04 vs 0.51 ± 0.04 and 0.41 ± 0.22, respectively; P < 0.05). CONCLUSION : The synergistic combination of rhGH and Gln can significantly improve the adaptation of the remnant small intestine in parenterally fed SBS rats. An increase in cell proliferation and a decrease in cell apoptosis are both responsible for the intestinal adaptation. An increase in local IGF‐1 plays an important role in this process.     

Abnormal Expression of the Peptide Transporter PepT1 in the Colon of Massive Bowel Resection Rat: A Potential Route for Colonic Mucosa Damage by Transport of fMLP

The aim of this study was to investigate the effect of abnormal intestinal oligopeptide transporter (PepT1) on rat colon inflammation by transportion of N-formyl-methionyl-leucyl-phenylalanine (fMLP). We induced upregulation of PepT1 in the colon of rats by 80% small bowel resection and examined colonic PepT1 di-tripeptide transport activity. By Western blot analysis, PepT1 was clearly detected in the colon of bowel resection rats, while it was absent from the colon of bowel transection and reanastomosis rats. The experiment with cephalexin colon perfusion showed that the arterial cephalexin concentration in resection rats was five to nine times that in transection rats. Inhibition of PepT1 by Gly–Gly completely abolished cephalexin absorption from the colon of resection rats. We found that 10 μM fMLP perfusion in the colon of resection rats for 4 hr significantly increased myeloperoxidase (MPO) activity and caused colon wall damage. In contrast, 10 μM fMLP perfusion in the colon of transection rats did not induce any inflammation. A 5 mM Gly–Gly perfusion completely inhibited the MPO activity and colonic wall damage induced by 10 μM fMLP. We conclude that colonic PepT1 induced by bowel resection may provide a mechanism for oligopeptide transport and may serve as a potential cause of colonic mucosa damage by transport of the bacterial product fMLP in rat colon.     

The anabolic effects of recombinant human growth hormone and glutamine on parenterally fed,short bowel rats

AIM：To evaluate the metabolic effects associated with administration of rhGH and/or Gln in parenterally fed,short-bowel rats,Methods:Forty SD rats subjected to 75%intestinal resection and maintained with parenteral nutrition were randomly divided into 4groups as follows:-rhGH,-Gln;-rhGH,+Gln;+rhGH,-Gln:+rhGH,+Gln,Body weight and nitrogen balance were evaluated daily.After 6days of PN,rats were killed,various organs were dissected and weighted,the carcasses were used for analysis of body composition.Serum GH and IGF-1were determined by RIA method.RESULTS:Weight lossin rats with rhGH(17.4&#177;12.8g)and rhGH+Gln(23.8&#177;3.5g)was significantly less than rats with PNalone(29.6&#177;6.9g)and ats with Gln-supplemented PN(31.85&#177;12.8g),P&lt;0.05,The accumulated NBin rats with rhGH(1252。0132294.3mgN/d)and rhGH|Gln(1261.7&#177;85.5mgN/d)was significantly greater than those with PN alone(704.8&#177;379.0mgN/d)and with Gln-supplementedPN(856.7&#177;284.4mgN/d),P&lt;0.05.The absolute weight of gastrocnemius muscle in rats with rhGH(2683.9&#177;341.6mg)andrhGH+Gln(2579.1&#177;359.5mg)was greter than those withPNalone(2176.3&#177;167.1mg)and with Gln-supplementedPN(2141.9&#177;353.6mg).Although the absolute weight of remnant small intestine itself was not significantly different in 4experimental groups,the weight/length of the segments was greater in rats with rhGHand/or Gln(48.7&#177;5.5,52.7&#177;4.1and67.4&#177;5.3respectively)than those with PNalone(47.8&#177;5.0),there were synergistic effects between rhGHand Gln in improvement of the weight/hength of remnant small intestine,P&lt;0.05,Analyses of body carcass composition showed that a higher percentage of carcass weight as protein and a lower percentage of carcass weight as fat were occurred in ats with rhGH(20.8&#177;4.0,6.0&#177;2.6)andrhGH+Gln(21.3&#177;2.4,4.4&#177;1.5)than those with PNalone(16.4&#177;2.4,9.2&#177;3.7)and with Gln-supplemented PN(17.8&#177;3.0,6.3&#177;2.0),rhGH had significant effects on alteration of body composition,P&lt;0.05,Serum GH and IGF-1 concentration in rats with rhGH(5.221&#177;0.8and 425.1&#177;19.2ng/ml respectively)were greater than those with PN alone(3.327&#177;1.7and325.8&#177;29.6ng/ml respectively)and witGln-supplemented PN(3.433&#177;0.1and347.7&#177;55.7ng/ml respectively),P&lt;0.01.CONCLUSION:rhGH significantly improves the anabolism in parenterally fed.short obwel rats,anabolic effect with Gln is less dramatic,there is no synergistic effect between rhGH and Gln in improvement of whole body anabolism.IGF-1 plays an important part in growth-promoting effects of rhGH.     

Nutritional benefits of enteral alanyl-glutamine supplementation on rat small intestinal damage induced by cyclophosphamide

BACKGROUND: Glutamine is the principal fuel used by the small intestine. Although the parental administration of glutamine promotes intestinal mucosal growth, it is controversial whether enteral glutamine is effective against small intestinal damage caused by chemotherapy. To further evaluate the benefits of enteral supplementation, peptide and amino acid transporter functions must be considered. METHOD: Rats were given cyclophosphamide (CPM) intraperitoneally (300 mg/kg). Expression of the amino acid transporter, B0 and peptide transporter (PepT1) in the jejunal mucosa was initially examined by northern blot analysis. Rats received a bolus oral supplement of an alanine (1.22 g/kg/day) plus glutamine (2.0 g/kg/day) mixture, alanyl-glutamine (2.972 g/kg/day) or saline as a control, for 7 days after CPM administration. RESULTS: Levels of B0 mRNA remained unchanged at both 3 and 7 days after CPM administration. Conversely, PepT1 mRNA increased significantly after CPM administration, and reached 200% of the initial level 7 days later. In rats given alanyl-glutamine, the mucosal wet weight and protein content increased significantly with increasing villus height at 3 and 7 days, compared with the alanine plus glutamine mixture. The plasma glutamine concentration in the alanyl-glutamine group, but not the alanine plus glutamine mixture group, increased significantly compared with that in the saline group. CONCLUSION: Enteral supplementation with an alanyl-glutamine but not alanine plus glutamine mixture prevents intestinal damage, as demonstrated by increased peptide transport expression and an elevated plasma glutamine concentration after CPM administration.