谷氨酰胺对创伤后肠粘膜通透性的影响

在创伤的情况下,肠道通透性将发生改变,继而引起细菌移位和内毒素血症。谷氨酰胺可以通过降低肠粘膜通透性来减少细菌移位、减轻内毒素血症。     

Current smoking at menopause rather than duration determines the onset of natural menopause

BACKGROUND: Smoking has frequently been associated with early menopause. However, studies of this association have been inconclusive with regard to duration and intensity of smoking. A major problem in analyzing the effect of smoking duration on menopausal age is that both exposure and outcome are age-dependent. METHODS: We calculated age-specific rates for categories of smoking duration and subsequently computed the rate ratios for occurrence of menopause. We were thus able to model the effect of smoking duration on 2 time scales without assumptions of linearity. We used data from a Dutch population-based cohort comprising 5544 women age 49-70 years who had experienced natural menopause. RESULTS: The rate ratio (RR) for occurrence of menopause was increased in women who smoked in the year of menopause (RR = 1.41; 95% confidence interval = 1.32-1.50). The rate ratio of former smokers was similar to women who never smoked (0.95; 0.89-1.02). Prolonged exposure of smoking did not materially affect the risk of menopause, although the daily number of cigarettes currently smoked could increase the risk. CONCLUSION: Perimenopausal smoking is apparently more important than smoking history in explaining an earlier age of onset of menopause among women who smoke.     

腹部手术后患者血浆谷氨酰胺的变化及对肠道通透性的影响

目的：观察腹部手术后血浆Ｇｌｎ浓度变化及对肠道通透性的影响。     

谷氨酰胺对缺血-再灌注损伤大鼠肠黏膜炎性反应和通透性的影响

目的 研究谷氨酰胺（Gln）对缺血-再灌注损伤大鼠肠黏膜炎性反应和通透性的影响.方法 将48只SD大鼠肠系膜上动脉夹闭造成缺血后恢复血流,建立肠缺血-再灌注损伤模型,将造模后的SD大鼠按随机数字表分为对照组（n=24）和模型＋Gln组（n=24）,两组大鼠肠内营养供给量为热量125.4 kJ/ （kg·d）,氮量0.2g/ （kg·d）,模型＋Gln组喂饲肠内营养加3％ Gln,对照组大鼠喂饲肠内营养加3％大豆蛋白,造模后实验持续8d.检测造模前、造模后、实验第3天和第8天大鼠肠黏膜和血浆核因子-κB （NF-κB）、肿瘤坏死因子-α（TNF-α）、白细胞介素-6（IL-6）、Gln、D-乳酸（D-LAC）和二胺氧化酶（DAO）的变化.观察小肠黏膜形态学变化.结果 造模后对照组和模型＋ Gln组大鼠肠黏膜NF-κB表达明显高于造模前（75.0％比0.0％,P=0.013; 70.8％比0.0％,P=0.019）;肠黏膜IL-6明显高于造模前[（313.27±75.28） pg/g比（227.52 ±58.13） pg/g,P=0.023; （321.75±74.46） pg/g比（227.52±58.13） pg/g,P=0.043];肠黏膜TNF-α[（241.28±65.29） pg/g、（240.35 ±64.86） pg/g]明显高于造模前[（172.45±33.76） pg/g,P=0.036,P=0.011];血浆IL-6[（150.32±18.74） ng/L、（148.21 ±20.19） ng/L]明显高于造模前[（116.37±14.59） ng/L,P=0.032,P=0.025];血浆TNF-α[（127.62±14.24） ng/L、（123.86±13.75） ng/L]明显高于造模前[（85.18±8.84） ng/L,P=0.018,P=0.035]; D-LAC[（0.46±0.03） mmol/L、（0.51 ±0.04） mmol/L]明显高于造模前[（0.27±0.02） mmol/L,P=0.041,P=0.018]; DAO[（2.76±0.57） U/ml、（2.58±0.51） U/ml]明显高于造模前[（1.52±0.24） U/ml,P=0.015,P =0.037];而血浆Gln[（0.18±0.01） g/L、（0.21±0.01） g/L]明显低于造模前[（0.39±0.03） g/L,P =0.026,P=0.031].实验第3天和实验第8天,对照组大鼠肠黏膜NF-κB[16例（66.7％）、15例（62.5％）]显著高于造模前[0例（0.0％）,P=0.027,P=0.002];肠黏膜TNF-α[（226.23±55.35） pg/g、（214.76 ±54.82） pg/g]显著高于造模前[（172.45±33.76） pg/g,P=0.042,P=0.038];肠黏膜IL-6[（297.56±71.39） pg/g、（291.49±68.46） pg/g]显著高于造模前[（227.52±58.13） pg/g,P=0.031,P=0.012];血浆IL-6 [（147.38±17.25） ng/L、（144.65±15.32） ng/L]显著高于造模前[（116.37±14.59） ng/L,P=0.016,P=0.034];血浆TNF-α[（121.75±13.72）ng/L、（113.83±11.69） ng/L]显著高于造模前[（85.18±8.84） ng/L,P=0.025,P=0.041];D-LAC[（0.41 ±0.03） mmol/L、（0.53±0.05） mmol/L]显著高于造模前[（0.27±0.02） mmol/L,P=0.029,P=0.030]; DAO [（2.51±0.52） U/ml、（1.76±0.34） U/ml]显著高于造模前[（1.52±0.24） U/ml,P=0.034,P=0.016];但血浆Gln[（0.22±0.01） g/L、（0.21±0.03） g/L]显著低于造模前[（0.39±0.03） g/L,P=0.042,P=0.035].实验第3天模型＋Gln组肠黏膜NF-κB、TNF-α、IL-6 [14例（58.3％）、（213.78±43.76） pg/g、（293.72±69.86） pg/g]明显高于造模前（P=0.038、0.026、0.013）;血浆IL-6、TNF-α、D-LAC、DAO [（135.61 ±14.25） ng/L、（117.35±11.29）ng/L、（0.45 ±0.03） mmol/L、（2.26 ±0.43） U/ml]明显高于造模前（P=0.021、0.032、0.032、0.025）.实验第8天模型＋ Gln组肠黏膜NF-κB、TNF-α、IL-6[9例（37.5％）、（184.53 ±42.16） pg/g、（236.83 ±66.52） pg/g]明显低于造模后和对照组（P=0.024,P=0.027; P=0.026,P=0.039;P =0.013,P=0.028）;血浆IL-6、TNF-α、D-LAC、DAO[（126.35 ±12.74）ng/L、（92.76±9.42）ng/L、（0.31 ±0.02） mmol/L、（1.76 ±0.34） U/ml]明显低于造模后和对照组（P=0.021,P=0.030;P=0.032,P=0.025;P=0.024,P=0.037;P=0.022,P=0.036）,而血浆Gln水平[（0.40±0.03） g/L]明显高于造模后和对照组（P =0.028、0.032）.电镜下可见造模后绒毛、隐窝结构一定程度损害,绒毛稀疏且变短,固有膜内大量炎性细胞浸润,淋巴管扩张、水肿.实验第8天,模型＋Gln组与造模后和对照组比较小肠绒毛、隐窝结构显著恢复;对照组与造模后比较肠黏膜绒毛、隐窝结构恢复不明显,固有膜内仍有炎性细胞浸润.结论 Gln通过调节肠黏膜炎性因子的释放,抑制炎症反应,降低肠黏膜的通透性,修复缺血-再灌注后损伤的肠黏膜.     

Enzyme-induced asparagine and glutamine depletion and immune system function

Depletion of nonessential amino acids and its effect on the immune system can be studied by the administration of bacterial enzymes. Escherichia coli asparaginase hydrolyzes both asparagine and glutamine: administration of this enzyme to mice is rapidly immunosuppressive. Vibrio succinogenes asparaginase hydrolyzes only asparagine and has no apparent effect on immune system function. When the enzymes are rendered nonantigenic and nonimmunogenic by covalent attachment of polyethylene glycol, the effects on immune system function remain the same as described above with the native (nonmodified) enzymes. We believe the data reviewed justify the conclusion that glutamine deficiency is specifically immunosuppressive whereas asparagine deficiency is not. We further believe that enzymatic depletion of nonessential amino acids can be a useful tool for nutritional investigations.     

The effect of oral glutamine on 5-fluorouracil/leucovorin-induced mucositis/stomatitis assessed by intestinal permeability test

BACKGROUND & AIMS: Systemic chemotherapy may damage gastrointestinal epithelium. Mucositis is associated with increased intestinal permeability (IP). It is known that IP test with chromium 51-ethylene diaminetetra-acetate (51Cr-EDTA) is a useful tool to assess the mucositis. Oral glutamine supplements (OGS) may have a role in the prevention of chemotherapy-induced mucositis/stomatitis. The aim of this study was to characterize the relationship between the urinary excretion of 51Cr-EDTA and the severity of mucositis, and the effect of OGS on 5-fluorouracil/leucovorin (FU/LV)-induced mucositis/stomatitis. METHODS: Fifty-one patients with advanced or metastatic cancer received FU/LV chemotherapy. The control group included 18 healthy volunteers. IP was assessed via the measurement of 51Cr-EDTA urinary excretion after oral challenge, on days 7 after the discontinuation of chemotherapy. Of the 51 patients, 22 patients received OGS (30 g/day) and 29 received only best supportive care (BSC). Glutamine supplementation continued for 15 days. It was initiated at least 3 days before the beginning of chemotherapy. Mucositis/stomatitis was graded according to version 3.0 of the Common Terminology Criteria for Adverse Events. RESULTS: In the chemotherapy group, the median (25 percentile, 75 percentile) IP test score was significantly higher than those of the control group [6.78% (4.63, 10.66) vs. 2.17% (1.38, 2.40), P<0.001]. The severity of stomatitis was significantly correlated with IP test scores (r=0.898, P<0.001). In the OGS group, the median IP test score was significantly lower than that of the BSC group [4.69% (3.10, 6.48) vs. 8.54% (6.48, 15.31), P<0.001]. A mucositis/stomatitis of grade 2-4 was observed in two patients of the OGS group (9%), and in 11 patients (38%) in the BSC group (P<0.001). CONCLUSIONS: The IP test may be a useful tool in the evaluation of mucositis/stomatitis. OGS may exert a protective effect on FU/LV-induced mucositis/stomatitis. Further studies, however, will be necessary to define the role of glutamine supplementation in FU/LV-induced mucositis/stomatitis.     

Endogenous corticosterone rather than dietary sucrose as a modulator for intestinal sucrase activity in artificially reared rat pups

The effects of sucrose and corticosterone on the expression of intestinal sucrase activity in preweanling rat pups were studied using an artificial rearing (AR) technique. When AR rat pups were isocalorically fed diets containing lactose or sucrose, or a carbohydrate-free diet from d 12-16, jejunal and ileal sucrase and maltase activities were induced to similar levels in all AR rats, whereas ileal lactase activity was precociously decreased. In separate experiments, enzyme activities were measured in ileal isografts subcutaneously implanted in littermates at birth. In AR rats fed the lactose diet, these isografts showed sucrase and maltase activities comparable with those of host ileum and also to isografts from AR rats fed the sucrose diet. In contrast, lactase activity was significantly higher in isografts than host ileum in all AR rats. Serum corticosterone levels were significantly elevated in AR rats for 24 h after intragastric cannular implantation. Precocious expression of ileal sucrase activity occurred in corticosterone treated, but not in untreated, adrenalectomized AR rats. In conclusion, dietary sucrose has no specific role in enhancing intestinal sucrase activity, and endogenous corticosterone is responsible for the induction of sucrase activity in AR rats.     

Arginine-enriched diet limits plasma and muscle glutamine depletion in head-injured rats

OBJECTIVE: Injury is associated with a depletion in glutamine (GLN) pools, which may contribute to impairment of immune and nutritional statuses. Total parenteral nutrition enriched with arginine (ARG) is able to generate GLN in surgical patients. We hypothesized that this same concept may be applicable to enteral administration and could be extended to muscle GLN reserves. This study investigated the ability of an enteral formula enriched with ARG to restore the GLN pools in an experimental model of head injury. METHODS: Twenty-five male Sprague-Dawley rats were randomized into 4 groups: ad libitum access to food, head injury plus free access to nutrition, head injury plus standard enteral nutrition (Sondalis), and an immune-enhancing diet (IED). The two enteral diets were adjusted to be isocaloric (290 kcal.kg(-1).d(-1)) and isonitrogenous (3.29 g.kg(-1).d(-1)) and were delivered for 4 d (24 h/24 h). After sacrifice, plasma and muscle amino acids were determined. RESULTS: Head injury was associated with a large depletion of muscle and plasma GLN pools that were restored by IED administration but not by the standard diet. Moreover, the IED but not the standard diet improved or normalized ornithine and glutamate pools, suggesting that the modification of GLN pools is related to ARG administration. CONCLUSION: In our model of head injury, our IED, a diet without free GLN, is efficient in restoring the plasma and muscle pools of GLN, probably due to its high ARG content.     

Ornithine alpha-ketoglutarate counteracts thymus involution and glutamine depletion in endotoxemic rats

This work studied the action of ornithine a-ketoglutarate (OKG) supplementation in an experimental model of endotoxemia in the rat. Male Wistar rats were injected intraperitoneally with lipopolysaccharide (LPS) from Escherichia coli (0127:B8). They were fasted for 24 h, then refed for 48 h with an enteral diet supplemented with either OKG (66 mg N x kg(-1) x d(-1)) or glycine, isonitrogenous to the OKG group. A control (sham) group was also studied. LPS treatment induced a decrease in thymus and muscle weights compared to controls, and a decrease in glutamine and arginine concentrations in the anterior tibialis muscle. Supplementation with OKG restored thymus weight and muscle arginine level and increased muscle glutamine concentration, when compared to controls. We conclude that OKG counteracts the thymic involution that occurs with endotoxemia, and restores the muscular content of glutamine and arginine, both of which are involved in the regulation of immune function.     

全胃肠外营养和肠道通透性

自20世纪60年代以来，全胃肠外营养已得到了极大的发展。然而长期全胃肠外营养所致并发症亦越来越受到人们的关注。本文就其所致肠道通透性的改变及其可能的发病机制和当前的一些研究进展作一综述。     

The surface area rather than the surface coating determines the acute inflammatory response after instillation of fine and ultrafine TiO2 in the rat

Alterations in the hydrophobic status of particle surfaces have been suggested to modify the toxic properties of ultrafine TiO2. We investigated the acute inflammatory responses and cell damage after intratracheal instillation of surface modified (hydrophilic and hydrophobic) fine (180 nm) and ultrafine (20-30 nm) TiO2 particles 16 h at equivalent mass (1 or 6 mg) and surface doses (100, 500, 600 and 3000 cm2) in rats. Inflammatory response and most enzyme levels were significantly related to the administered surface dose. The hydrophobic surface of the TiO2 particles, achieved by methylation, induced a lower total cell number and influx of neutrophils (PMN) compared to rats instilled with the 1 mg of the untreated, fine or ultrafine TiO2 but the outcomes were not statistically significant. No differences were observed between fine/ultrafine and hydophilic/hydrophobic TiO2 at the high dose (6 mg) or surface dose over 600 cm2. The differences in BAL cellularity at the low dose were reflected in changes in the chemokine MIP-2, but no differences were seen in levels of macrophage cytokines. Considering the large influx of PMN little cell damage was seen when studying enzyme leakage in lavage fluid, although PMNs appeared to be activated as suggested by increased myeloperoxidase (MPO) activity in the lavage fluid. We conclude that the surface area rather than the hydrophobic surface determines the acute, pulmonary inflammation induced by both fine and ultrafine TiO2.     

Intravenous free and dipeptide-bound glutamine maintains intestinal microcirculation in experimental endotoxemia

ObjectiveThe administration of glutamine (Gln), which is depleted in critical illness, is associated with an improvement of gut metabolism, structure, and function. The aim of the present study was to evaluate the effects of intravenous Gln and its galenic formulation, l-alanyl-l-glutamine dipeptide (AlaGln), on the intestinal microcirculation during experimental endotoxemia using intravital fluorescence microscopy. Gln or AlaGln administration was performed as pretreatment or post-treatment, respectively. To identify further the underlying mechanisms, amino acid levels were studied.MethodsSixty male Lewis rats were randomly divided into six groups (n = 10/group): control, LPS (lipopolysaccharide 5 mg/kg intravenously), Gln/LPS (LPS animals pretreated with Gln 0.75 g/kg Gln intravenously), AlaGln/LPS (LPS animals pretreated with AlaGln intravenously, 0.75 g/kg Gln content), LPS/Gln (LPS animals post-treated with Gln 0.75 g/kg intravenously), and LPS/AlaGln (LPS animals post-treated with AlaGln intravenously, 0.75 g/kg Gln content). Two hours after the endotoxin challenge, the microcirculation of the terminal ileum was studied using intravital fluorescence microscopy. Blood samples were drawn at the beginning, during, and the end of the experiment to determine the amino acid levels.ResultsThe Gln and AlaGln pre- and post-treatment, respectively, prevented the LPS-induced decrease in the functional capillary density of the intestinal muscular and mucosal layers (P < 0.05). The number of adherent leukocytes in the submucosal venules was significantly attenuated after the Gln and AlaGln pre- and post-treatment (P < 0.05).ConclusionThe Gln and AlaGln administrations improved the intestinal microcirculation by increasing the functional capillary density of the intestinal wall and decreasing the submucosal leukocyte activation.     

Growth hormone, glutamine, and modified diet for intestinal adaptation

Many patients who undergo extensive resection of the gastrointestinal tract develop intestinal failure from short-bowel syndrome that results in significant malabsorption of fluid, electrolytes, and other nutrients. This may result in dependence on long-term parenteral nutrition. It has been almost a decade since Byrne and colleagues published their research demonstrating enhanced absorption of nutrients, improved weight gain, and reduction in parenteral nutrition requirements with the administration of a combination of growth hormone, glutamine, and a modified diet. Other researchers have conducted similar studies with inconsistent results. A systematic search on electronic databases and the Internet for the purpose of identifying the evidence published to date on this subject was performed. The analysis suggests administering recombinant human growth hormone alone or together with glutamine with or without a modified diet may be of benefit when the appropriate patients are selected for treatment.