Protein malnutrition alone and in combination with endotoxin impairs systemic and gut-associated immunity.

Because protein-malnourished or endotoxemic patients are at an increased risk of developing nosocomial infections, this study was performed to investigate the effects of protein malnutrition and endotoxemia, alone and in combination, on systemic and intestinal immunity. Protein malnutrition was created by feeding the animals a solid diet containing 0.03% protein. Subgroups of these protein-malnourished mice were killed after being challenged with saline or endotoxin on days 0, 7, 14, or 21. At death, the animals were weighed, tissues were harvested for histologic analysis (ileum, mesenteric lymph node [MLN], liver, and spleen), mitogen responsiveness (MLN, Peyer's patches, and spleen), and xanthine oxidase measurements (ileum and cecum). Separate groups were evaluated for survival. Both the saline and endotoxin-challenged mice had lost about 30% of their body weight after 21 days on the low-protein diet. The protein-malnourished mice were more susceptible to endotoxin-induced mortality (70% at 21 days) than the normally nourished mice (0%) (p less than .001). The mitogen responsiveness of the protein-malnourished mice to the T-cell mitogens (PHA and Con-A) progressively decreased the longer the mice were protein malnourished, and this decreased in blastogenic responsiveness was associated with histologic evidence of lymphoid atrophy. In contrast, the blastogenic response to the primarily B-cell mitogen, PWM, was largely preserved. The endotoxin challenge further depressed the immune state of mice tested after 0, 7, or 14 (but not 21) days of protein malnutrition. Thus, both protein malnutrition and endotoxin impaired systemic and gut-associated immune responsiveness to mitogens. However, in the protein-malnourished mice, the degree of immune suppression did not correlate with endotoxin-induced mortality.     

肠内营养在维护门静脉高压症术后患者肠道黏膜屏障功能中的作用

目的了解肠内营养在维护门静脉高压症术后患者肠道黏膜屏障功能中的作用和地位。方法40例门静脉高压症手术患者随机进入肠内(EN)或肠外营养(PN)组,术后分别接受肠内外营养,观察两种营养方式对患者内脏蛋白合成能力、肝功能及其储备、胃肠功能、内毒素水平、肠道细菌移位和乳果糖/甘露醇比值等方面的影响。结果两种营养方式均能改善患者的营养状况。EN术后并发症少,在刺激肠道蠕动,减轻内毒素水平,防止肠道菌群移位,维护肠黏膜屏障方面优于PN,且差异显著(P<0.05)。结论EN是维护此部分患者肠道黏膜免疫屏障功能稳定的有效方式。     

益生菌在肠内营养中的应用及研究进展

防治肠源性感染的关键在于防止肠内细菌和(或)内毒素的移位,纠正肠内菌群平衡的紊乱和失调,改善肠黏膜屏障功能以及提高肠道局部的免疫功能。而益生菌是具有维持肠内菌群平衡、防止肠黏膜屏障的破坏、增强局部免疫功能、促进和改善消化道蠕动以及吸收等作用的非致病性微生物,可治疗和预防肠源性感染。以下综述益生菌在肠内营养的作用及研究进展。     

Bulk prevents bacterial translocation induced by the oral administration of total parenteral nutrition solution

The effects of a fat and glutamine-free orally administered total parenteral nutrition (TPN) solution on intestinal mucosal mass, morphology, barrier function, and cecal bacterial population levels were measured in CD-1 mice. Ileal mucosal protein content decreased by 63% (p less than 0.01) in the oral TPN-fed mice, although they gained weight on this diet. These TPN-fed mice also exhibited changes in mucosal structure and the normal ecology of their cecal microflora was disrupted leading to overgrowth with Gram-negative enteric bacilli. These changes in intestinal mucosal mass, morphology, and gut bacterial ecology were associated with an increased incidence of bacterial translocation (BT) (TPN group 70% BT vs control group 15% BT: p less than 0.01). The administration of cellulose fiber or kaolin (bulk-forming agents), but not of citrus-pectin (a fully-fermentable, nonresidue fiber) reduced the incidence of BT in the TPN-fed mice to control levels. The beneficial effects of these bulk-forming agents appeared to be due to their ability to prevent TPN-induced disruption of the intestinal microflora and alterations in intestinal morphology, even though they did not prevent ileal mucosal protein levels from decreasing. These results suggest that the administration of bulk forming agents will prevent the loss of intestinal barrier function against luminal bacteria that occurs in mice fed an oral TPN solution.     

Plasmodium chabaudi Infection Alters Intestinal Morphology and Mucosal Innate Immunity in Moderately Malnourished Mice

Plasmodium falciparum is a protozoan parasite which causes malarial disease in humans. Infections commonly occur in sub-Saharan Africa, a region with high rates of inadequate nutrient consumption resulting in malnutrition. The complex relationship between malaria and malnutrition and their effects on gut immunity and physiology are poorly understood. Here, we investigated the effect of malaria infection in the guts of moderately malnourished mice. We utilized a well-established low protein diet that is deficient in zinc and iron to induce moderate malnutrition and investigated mucosal tissue phenotype, permeability, and innate immune response in the gut. We observed that the infected moderately malnourished mice had lower parasite burden at the peak of infection, but damaged mucosal epithelial cells and high levels of FITC-Dextran concentration in the blood serum, indicating increased intestinal permeability. The small intestine in the moderately malnourished mice were also shorter after infection with malaria. This was accompanied with lower numbers of CD11b⁺ macrophages, CD11b⁺CD11c⁺ myeloid cells, and CD11c⁺ dendritic cells in large intestine. Despite the lower number of innate immune cells, macrophages in the moderately malnourished mice were highly activated as determined by MHCII expression and increased IFNγ production in the small intestine. Thus, our data suggest that malaria infection may exacerbate some of the abnormalities in the gut induced by moderate malnutrition.     

Prenatal protein malnutrition alters the proportion but not numbers of parvalbumin-immunoreactive interneurons in the hippocampus of the adult Sprague-Dawley rat

Prenatal protein malnutrition alters the structure and function of the adult rat hippocampal formation. The current study examines the effect of prenatal protein malnutrition on numbers of parvalbumin-immunoreactive (PV-IR) GABAergic interneurons, which are important for perisomatic inhibition of hippocampal pyramidal neurons. Brain sections from prenatally protein malnourished and normally nourished rats were stained for parvalbumin and PV-IR neurons were quantified using stereology in the dentate gyrus, CA3/2 and CA1 subfields, and the subiculum for both cerebral hemispheres. Results demonstrated that prenatal malnutrition did not affect the number of PV-IR interneurons in the hippocampus. Since prenatal protein malnutrition reduces total neuron numbers in the CA1 subfield (1), this results in an altered ratio of PV-IR interneurons to total neuronal numbers (from 1:22.9 in controls to 1:20.5 in malnourished rats). Additionally, there was no hemispheric asymmetry of either PV-IR neuron numbers or ratio of PV-IR:total neuron numbers.     

Malnutrition and diarrhea. A longitudinal study among urban Mexican children

To address the hypothesis that malnutrition is associated with an increased risk of diarrhea, the authors identified a cohort of 284 Mexican children less than two years of age in order to equally represent different degrees of nutritional status. Nutritional status, defined anthropometrically, was measured at baseline and every three months for a total follow-up period of one year. The occurrence of diarrhea was assessed by weekly home visits. Among the combinations of weight and length examined, weight for age was the strongest predictor of subsequent diarrhea during a three-month interval. Among normally nourished children, the incidence of diarrhea was 3.3 episodes per year; among those mildly malnourished, 3.7 episodes per year (relative risk (RR) = 1.1); and among the moderately malnourished, 6.0 episodes per year (RR = 1.8). Adjustment for demographic, seasonal, and socioeconomic variables only slightly reduced this association. Nutritional status was most strongly related to the occurrence of two or more episodes during a three-month follow-up interval, and this effect was most clearly seen among children with diarrhea in the preceding interval. In a multiple logistic analysis that included potentially confounding variables as well as an autoregressive term to account for the nonindependence of repeated observations, the relative risk of two or more episodes of diarrhea during an interval was 1.8 (95% confidence interval 1.1-2.9) for moderately malnourished children compared with those who were normally nourished or mildly malnourished. These data lend support to the hypothesis that malnutrition predisposes to the occurrence of diarrhea among young children.     

乳杆菌对致病性大肠杆菌感染小鼠肠黏膜屏障功能的影响

目的:研究乳杆菌对致病性大肠杆菌感染小鼠肠黏膜屏障的保护作用.方法:将BALB/c小鼠随机分为对照组、致病性大肠杆菌感染组、乳杆菌JCM1081灌胃组、乳杆菌治疗组等,实验进行14 d.观察各组小鼠肠黏膜形态变化、肠道菌群变化、细菌移位以及肠黏膜钙黏蛋白表达的差异.结果:致病性大肠杆菌感染组小鼠与对照组相比,肠黏膜形态有明显改变,肠道内厌氧菌数量显著下降,肠杆菌和肠球菌数量明显增加,在肝、脾、肾以及肠系膜淋巴结中有细菌存在,但肠黏膜钙黏蛋白无明显变化.乳杆菌灌胃组小鼠各项指标无显著变化.乳杆菌治疗组小鼠各项指标变化程度较致病性大肠杆菌感染组显著减轻.结论:乳杆菌能黏附定植于肠黏膜并形成生物屏障,起着保护肠黏膜免受损伤的作用.     

Effect of malnutrition on extraintestinal spread of rotavirus and development of hepatitis in mice

The effects of malnutrition on the extramucosal spread and severity of the clinical disease were examined in suckling BALB/c mice infected with heterologous rhesus rotavirus (RRV). Control animals were inoculated with homologous murine rotavirus (MRV). Following oral infection with RRV, 100% of malnourished and 90% of normally nourished mice exhibited watery diarrhea within 48 hours. The clinical symptoms appeared more severe and of longer duration in the malnourished group. At 7 to 14 days post-inoculation, 30 of 79 (38%) malnourished and 19 of 92 (21%) well nourished mice developed icterus, clay-colored feces and dark yellow urine. The mortality rates were 9% and 0%, respectively. Light microscopy revealed an acute hepatitis with foci of necrosis. Rotavirus was detected in liver tissue by cell culture infectivity, immunofluorescence assay and electron microscopy. Homologous MRV infection resulted in diarrhea in all animals and with increased severity in the malnourished group. Significantly, however, none of the control animals developed hepatitis and no virus could be detected in the liver. These results suggest that malnutrition may exert significant influence on the severity of rotavirus infection and on the extent of extramucosal spread of RRV. Since several heterologous rotavirus strains are currently being tested in human vaccine trials, the implications of our observations suggest that special attention should be paid to malnourished infants and that screening of hepatic function should be included in vaccine protocols.     

早期肠内营养支持对犬重症急性胰腺炎肠道屏障功能的影响

目的：观察早期肠内营养（EEN）对犬重症急性胰腺炎（SAP）肠道粘膜结构、功能及细菌、内毒素移位的影响。方法：在麻醉状态下，进腹向胰管内注入5％牛磺胆酸钠混合液1ml/kg诱导SAP。15只杂种犬SAP分为肠外营养（PN）组和EEN组。EEN组在诱导SAP后24h采用EN，维持5天。在实验前、后1、4、7天测定外周血内毒素（ET）。实验结束，取门静脉血测定ET；取肠系膜淋巴结、肺门以及肺组织、胰腺和门静脉血作细菌培养。测定小肠、结肠蛋白质和DNA含量，并作粘膜形态学观察。结果：EEN组外周血及门静脉血ET和各脏器中细菌含量均低于PN组，P＜0．05；小肠和结肠肠壁蛋白质、DNA含量、绒毛高度、粘膜及全层厚度均明显高于PN组，P＜0．05。结论：EEN有助于防止犬SAP肠粘膜萎缩及细菌移位。     

重症急性胰腺炎时细胞因子与肠源性细菌和内毒素移位的实验研究

目的 探讨重症急性胰腺炎(SAP)时血浆细胞因子与肠道屏障损害后肠源性细笛和内毒素移位的关系。方法 将SD大鼠(清洁级)72只随机分为假手术组(n=36)和SAP组(n=36)。采用胰管内逆行注射4％牛磺胆酸钠溶液的方法制作SAP模型。观察胰腺和回肠的病理改变，动态测定血浆TNF-a、IL-6、IL-10和DAO活性、LPS水平以及腹腔脏器细菌移位率。结果 制模后血浆TNF-a、IL-6水平明显升高，48h达到高峰，IL-106h后才明显升高；血浆DAO活性早期升高，24h后明显降低；LPS水平早期即有明显升高，48h达到高峰；SAP24h脏器细笛移位率明显升高，72h达到58．3％。结论 SAP早期即有细胞因子水平的升高和肠道屏障的损害，细胞因子通过损害肠遗屏障，引起肠源性细菌和内毒素移位；同时，肠源性细菌和内毒素移位又促进细胞因子的大量释放。加重肠黏膜屏障本身的损害，遣成恶性循环，引起SIPS和MODS的发生，两者关系密切。     

Impaired wound healing in surgical patients with varying degrees of malnutrition

The relationship between nutritional state and wound healing was examined in 66 adult surgical patients. Wound-healing response was assessed by measuring the collagen content (hydroxyproline) of fine tubes of Gore-tex inserted subcutaneously along standardized needle track arm wounds. After a period of 7 days, the tubes were removed and it was found that there was a higher hydroxyproline content in the tubing of 36 normally nourished patients than there was in the tubing of 21 patients with mild protein energy malnutrition (p less than 0.01) and 9 patients with moderate to severe protein energy malnutrition (p less than 0.01). There was no difference in the wound-healing response between the two latter groups of patients who had significantly different degrees of malnutrition. The results suggest that a definite abnormality in the wound-healing response exists in malnourished surgical patients, but it occurs earlier in the course of the illness than previously supposed.     

An evaluation of insulin-like growth factor-1 as an indicator of nutritional status

This study evaluated the usefulness of insulin-like growth factor-1 (IGF-1) as a marker of nutritional status in 185 hospitalised patients compared with conventional biochemical (albumin) and anthropometric parameters. C-reactive protein (CRP) was used as a biochemical marker of underlying illness. 77 (42%) patients were normally nourished or overweight and 108 (58%) were nutritionally depleted. IGF-1 and albumin were significantly lower in the malnourished patients as a group. However, in the malnourished patients with normal CRP, there was no correlation between albumin or anthropometric measurements and IFG-1. In malnourished patients with a raised CRP, there was no relationship between malnutrition determined by body mass index and anthropometry and either albumin of IGF-1 concentrations. In normally nourished patients with a raised CRP, there was a relationship between albumin and CRP; and IGF-1 and CRP and between albumin and IGF-1. IGF-1 was related to age in all groups of patients. We conclude that neither albumin nor IGF-1 can be reliably used to assess nutritional status.     

利用生物发光活体成像技术观察肠黏膜损伤状态下细菌易位的初步研究

[目的]临床上各种疾病会导致肠黏膜屏障损伤并伴随大量的细菌易位发生。本实验拟使用发光细菌的小鼠活体成像技术,观察肠黏膜损伤状态下易位细菌的动态移位过程。[方法]构建重组荧光脂酶基因(Lux)的质粒pXen-1、pXen-18,转化大肠杆菌DH5a,筛选阳性细菌克隆,扩增培养后,定量(107)注射到肠黏膜屏障损伤模型小鼠肠腔不同部位内,利用生物发光活体成像技术进行细菌易位的病理生理观察研究。实验分为四组:小肠注射菌实验组和对照组、盲肠注射菌实验组和对照组。其中实验组为肠道缺血再灌注损伤,对照组无任何干预措施。[结果]发光细菌小鼠活体成像观察到,存在肠黏膜损伤的小鼠肠腔内的细菌数量及分布发生明显的改变,提示细菌易位在肠黏膜损伤时起着重要的病理生理作用。注入小肠内的发光细菌数量在试验过程中明显下降,提示小肠肠腔环境可以杀灭一定的细菌。[结论]生物发光活体成像技术,可以直观、可靠、敏感地观察肠道内细菌的存活状态,并可观察肠黏膜损伤状态下细菌易位的动态过程。该技术为肠黏膜屏障损伤细菌易位机制的研究提供了一个有力的工具。     

大鼠肠缺血-再灌注后营养对肠黏膜屏障功能的影响

目的:研究不同营养物质及营养支持途径对大鼠肠道缺血-再灌注时肠黏膜屏障功能的影响. 方法:将大鼠随机分为缺血-再灌注组、对照组及缺血-再灌注后各营养支持组.实验结束行肠黏膜屏障功能指标的检测. 结果:缺血-再灌注后肠黏膜发生明显损伤,普通肠外营养(PN)组D-乳酸、血浆内毒素水平、细菌移位率均显著高于其他各组(P<0.05);普通肠内营养(EN)组血浆内毒素水平明显低于谷氨酰胺肠外营养(G-PN)组(P<0.05),EN和免疫肠内营养(IEN)组细菌移位率无显著差异(P>0.05). 结论:①肠内营养在维护肠黏膜屏障功能方面优于肠外营养.②谷氨酰胺对改善肠黏膜屏障功能有显著作用,但无法取代肠内营养的作用.③免疫增强型营养与普通肠内营养相比,对细菌移位的防治效果并不大.     

Effect of oral genistein and isoflavone-free diet on cecal flora and bacterial translocation in antibiotic-treated mice

BACKGROUND: There are several reports indicating that the isoflavone genistein may augment the integrity of the intestinal epithelial barrier as well inhibit bacterial internalization by cultured enterocytes. We speculated that oral genistein might enhance the integrity of the intestinal epithelial barrier as monitored by the extraintestinal dissemination of intestinal bacteria. METHODS: Mice were treated with oral antibiotics to induce cecal bacterial overgrowth accompanied by bacterial translocation of antibiotic-resistant enterobacteria, especially Escherichia coli. These mice were divided into separate groups that included chow-fed mice orally inoculated either with saline, vehicle, or genistein, and mice fed isoflavone-free diet and orally inoculated with either saline, vehicle, or genistein. Intestinal bacterial overgrowth was monitored by quantitative culture of excised ceca and bacterial translocation was monitored by quantitative culture of draining mesenteric lymph nodes. RESULTS: Mice fed the isoflavone-free diet had decreased populations of cecal bacteria compared with chow-fed mice, and bacterial translocation was reduced in chow-fed mice compared with mice fed isoflavone-free diet. However, bacterial translocation was similar in mice given oral genistein compared with appropriate control mice. CONCLUSIONS: Oral genistein had no noticeable effect on bacterial translocation in this model. However, the isoflavone-free diet had an antibacterial effect on cecal flora, and the isoflavone-free diet was associated with decreased numbers of cecal bacteria and decreased incidence of bacterial translocation.     

Intestinal disaccharidases in malnourished infant rats

In infants suffering from protein-calorie malnutrition, the decreased intestinal mucosal lactase specific activity could be due either to the protein-calorie malnutrition or to the commonly associated enteritis (viral or bacterial) and intestinal parasites. We studied intestinal mucosal disaccharidase (lactase, sucrase, and maltase) specific activity in suckling (1 and 2 wk old), weanling (3 wk old), and postweaning (4 and 6 wk old) control and growth-retarded (malnourished) rats. Growth retardation was induced by feeding mother rats and postweaning rats a diet deficient in protein. In the malnourished rats, with few exceptions, specific activity of the disaccharidases in the intestinal mucosa were similar to those in the corresponding control groups of rats. However, because of marked mucosal atrophy total intestinal mucosal disaccharidase activities were more than 50% lower in the malnourished rats. These findings suggest that the specific activity of the intestinal mucosal disaccharidases is not affected by malnutrition per se.     

Jamaican studies in nutrition and child development, and their implications for national development.

In a hospital in Jamaica, a study compared the developmental levels of 18 children suffering from severe protein energy malnutrition (PEM) with those of 15 sufficiently nourished children. Even though both groups had low scores on the Griffiths' test, the malnourished children had a significantly lower score than the controls. Upon recovery, both groups improved at the same speed, resulting in a continual deficit of the malnourished group. Another study in Jamaica involved longterm psychosocial stimulation at the hospital and then at home with children with severe PEM. They were compared with another severely malnourished group who received no intervention and with an adequately nourished group. The case group caught up with the adequately nourished group within 2 years. 6 years after intervention, their school grades in spelling and reading were significantly higher than those of the non- intervention malnourished group. Another study in Jamaica showed that factors associated with stunting, and not an acute episode of malnutrition, accounted for poor developmental levels in severely malnourished children. Studies with children suffering from mild to moderate undernutrition suggested that food supplementation improves stunted children's development and that a link exists between their underlying nutritional status and short-term food deprivation. None of the aforementioned studies confirmed a causal association between reduced activity and poor development. Since these studies indicated that nutritional status is linked to educational success or failure and other studies have demonstrated a link between education and individual or national development, Jamaica should promote nutritional interventions to increase equity and improve life chances, thereby benefiting national development.     

OK-432 reduces mortality and bacterial translocation in irradiated and granulocyte-colony stimulating factor (G-CSF)-treated mice

Bacterial translocation/Acute radiation syndrome/Endotoxin/G-CSF/OK-432 Acute radiation induces bacterial translocation from the gut, followed by systemic infection and sepsis. In order to reduce the mortality after acute whole body irradiation, it is essential to control bacterial translocation. In this study, we established a bacterial translocation assay as a sensitive method to detect minor mucosal injury by radiation. By utilizing this assay, we evaluated the adverse effects, if any, of hematopoietic reagents on the mucosal integrity in the respiratory and gastro-intestinal tracts. Bacterial translocation to the liver and spleen occurred after whole-body irradiation if the dose exceeded 6 Gy. The administration of G-CSF unexpectedly increased the bacterial translocation in 8 Gy-irradiated mice. The pharmaceutical preparation of low-virulent Streptococcus pyogenes, OK-432, significantly reduced the endotoxin levels in peripheral blood without any reduction of bacterial translocation. A combined treatment with G-CSF and OK-432 decreased bacterial translocation and prevented death. This result indicates that the early administration of G-CSF has an adverse effect on bacterial translocation, and that a combined treatment of G-CSF and OK-432 attenuates the adverse effect of G-CSF and improves the survival rate after acute irradiation.     

多黏菌素E诱导肠道菌群失调对肠屏障功能和细菌易位的影响

目的:应用多黏菌素E给小鼠灌胃诱导建立肠道菌群失调动物模型,研究肠道菌群失调对肠黏膜屏障和细菌易位的影响。方法:将20只小鼠随机分为两组,每组10只。实验组采用多黏菌素E按0.2 g/kg加入0.2 ml等渗盐水灌胃,1次/d,连续7 d。对照组用等剂量等渗盐水灌胃,1次/d,连续7 d。实验结束次日观察两组小鼠回肠黏膜病理形态、肠道菌群、回肠黏膜组织紧密连接(TJ)蛋白表达和器官(肝、脾、肾、淋巴结)细菌易位率等。结果:实验组小鼠盲肠黏膜和盲肠内容物的肠杆菌数量显著减少。常规病理检查发现,实验组小鼠回肠黏膜充血明显,绒毛稀疏,尖端有少量上皮坏死脱落,与对照组比损伤明显。透射电镜显示,实验组小鼠回肠上皮TJ的电子致密物质明显减少,TJ破坏。回肠黏膜组织中TJ蛋白Claudin-1、Occludin和ZO-1的表达显著下降,器官细菌易位率显著高于对照组。结论:多黏菌素E灌胃能够诱导肠道菌群失调,且导致肠屏障功能损伤和细菌易位。