Transformation of Trichothecenes in Ileal Digesta and Faeces from Pigs

The capacity of pig gastrointestinal microflora to metabolise the trichothecenes 3-acetyl-deoxynivalenol (3-acDON) and nivalenol (NIV) was investigated. 3-acDON was deacetylated to DON in anaerobic incubations with pig faeces collected at different pig farms. Furthermore, both 3-acDON and NIV were metabolised to the corresponding de-epoxy metabolite in these incubates. Five pigs, in which the gastrointestinal microflora lacked the ability to transform 3-acDON and NIV to their corresponding de-epoxidated metabolites, were given low levels of DON in the feed for seven weeks. The gastrointestinal micro-organisms did not acquire the de-epoxidation ability during the seven week long exposure period. At the end of the exposure period, faeces from pigs with a known de-epoxidation ability was spread out in the pens and left for 24 hours. One week after the faeces had been spread out in the pens, the de-epoxidation ability was found in faecal incubations from four out of five experimental pigs. This change in metabolic ability of the intestinal de-epoxidation ability was not accompanied by any detectable changes in the DNA-profiles of the bacterial community composition. The results show that the intestinal de-epoxidation ability is common at pig farms in the Uppsala area, and that the ability may be transferred between pigs in a stock.     

Gastrointestinal absorption and metabolism of apple polyphenols ex vivo by the pig intestinal mucosa in the Ussing chamber

Polyphenols contained in food have various positive effects on human health. The absorption and metabolism of polyphenols in the intestinal tract needs to be studied to estimate these effects. The Ussing chamber technique was used to investigate the transport behavior of apple polyphenols through pig small intestinal mucosa, which served as a model for human gastrointestinal mucosa. The identities and concentrations of polyphenols and their metabolites in the half-chambers (luminal and basolateral) within an incubation period of 4 h were determined by HPLC–MS/MS and HPLC–DAD (DAD = diode-array detection). Flux values were also measured. It was found that 5-caffeoylquinic acid and caffeic acid were absorbed and translocated to the basolateral side (1.9 and 3.7%, respectively), but other compounds, including glycosides of phloretin and quercetin, were observed without translocation. A Ussing chamber utilizing pig small intestinal mucosa is a suitable model for assessing the effect of apple polyphenols on mucosal integrity and nutrition absorption across porcine mucosa.     

Human Core Temperature Responses during Exercise and Subsequent Recovery: An Important Interaction between Diurnal Variation and Measurement Site

Chronobiological investigations into core temperature during and after exercise can involve ambulatory measurements of intestinal temperature during actual competitions, esophageal temperature measurements in laboratory simulations, or rectal temperature, which can be measured in both the field and laboratory. These sites have yet to be compared during both morning and afternoon exercise and subsequent recovery. At 08∶00 and 17∶00 h, seven recreationally active males exercised at 70% peak oxygen uptake for 30 min and then recovered passively for 30 min. During the experiment, esophageal, rectal, intestinal, and skin temperatures, plus sweat loss, heart rate, and ratings of perceived exertion (RPE), were monitored. We found that the diurnal variation in intestinal temperature responses (0.45±0.32°C; mean±SD) was significantly larger compared with rectal (0.33±0.24°C) and, particularly, esophageal temperature responses (0.21±0.20°C; p= 0.019). This reflected a greater difference of 0.25–0.40°C between the esophagus and the other two sites in the afternoon, compared to inter‐site differences of only 0.13–0.16°C in the morning. Diurnal variation was small for skin temperature, heart rate, sweat loss, and RPE responses during exercise (p>0.05). Our data suggest that the relative differences between intestinal, rectal, and esophageal temperature during exercise and subsequent recovery depend on time of day to the extent that inferences from studies on experimental and applied chronobiology will be affected.     

Circadian Variations in Exsorptive Transport: In Situ Intestinal Perfusion Data and In Vivo Relevance

The circadian timing system (CTS) governs the 24-h rhythm of the organism and, hence, also main pathways responsible for drug pharmacokinetics. P-glycoprotein (P-gp) is a drug transporter that plays a pivotal role in drug absorption, distribution, and elimination, and temporal changes in its activity may affect input, output, activity, and toxicity profile of drugs. In the current study, the influence of different circadian stages on the overall intestinal permeability (P_eff) of the P-gp substrates talinolol and losartan was evaluated in in situ intestinal perfusion studies in rats. Additionally, in vivo studies in rats were performed by employing the P-gp probe talinolol during the day (nonactive) and night (active) period in rats. Effective intestinal permeabilities of talinolol and losartan were smaller in studies performed during the night (p?<?.05), indicating that P-gp–dependent intestinal secretion is greater during the nighttime activity span than daytime rest span of the animals. P-gp modulators vinblastine and PSC833 led to a significant decrease of talinolol and losartan exsorption in the intestinal segments as compared with control groups. Strikingly, the permeability-enhancing effect of vinblastine and PSC833 was higher with night perfusions, for both talinolol and losartan. In vivo studies performed with talinolol revealed—consistent with the in situ studies (P_eff day?>?night)—a day vs. night difference in the oral availability of talinolol in the group of male rats in terms of the area under the curve (AUC) data (AUC_day?>?AUC_night). The P-gp modulator vinblastine significantly increased talinolol AUC_day (p?<?.05), whereas only a weak vinblastine effect was seen in night. According to the in situ data, the functional activity of P-gp was regulated by the CTS in jejunum and ileum, which are major intestinal segments for energy-dependent efflux. In conclusion, circadian rhythms may affect carrier-mediated active efflux and play a role in the absorption process. In addition to daily rhythms in P-gp activity in rat intestine, the in vivo studies indicate that absorption-, distribution-, metabolism-, and elimination-relevant rhythms may be involved in the circadian kinetics of the drug, besides transporter-dependent efflux, such well-known aspects as metabolic or renal clearance or motility. Since this also holds true for a potentially interacting second compound (modulator), modulator effects should be evaluated carefully in transporter related drug-drug interactions. (Author correspondence: aokyar@istanbul.edu.tr)     

A Quantitative Cell Migration Assay for Murine Enteric Neural Progenitors

Neural crest cells (NCC) are a transient and multipotent cell population that originates from the dorsal neural tube and migrates extensively throughout the developing vertebrate embryo. In addition to providing peripheral glia and neurons, NCC generate melanocytes as well as most of the cranio-facial skeleton. NCC migration and differentiation is controlled by a combination of their axial origin along the neural tube and their exposure to regionally distinct extracellular cues. Such contribution of extracellular ligands is especially evident during the formation of the enteric nervous system (ENS), a complex interconnected network of neural ganglia that locally controls (among other things) gut muscle movement and intestinal motility. Most of the ENS is derived from a small initial pool of NCC that undertake a long journey in order to colonize - in a rostral to caudal fashion - the entire length of the prospective gut. Among several signaling pathways known to influence enteric NCC colonization, GDNF/RET signaling is recognized as the most important. Indeed, spatiotemporally controlled secretion of the RET ligand GDNF by the gut mesenchyme is chiefly responsible for the attraction and guidance of RET-expressing enteric NCC to and within the embryonic gut. Here, we describe an ex vivo cell migration assay, making use of a transgenic mouse line possessing fluorescently labeled NCC, which allows precise quantification of enteric NCC migration potential in the presence of various growth factors, including GDNF.     

儿童肠道双歧杆菌和乳杆菌种群结构分析

以21例2～5岁中国儿童的肠道菌群为研究对象,利用传统培养计数法和分子生物学技术,对此年龄段健康儿童的肠道菌群分布及其中关键益生菌的种群结构进行了定量研究。实验表明,儿童肠道厌氧菌的数量高达109CFUg(湿重),其肠道菌群的定植抗力(平均BE=2.38)较强;不同的个体之间所能检测到的关键益生菌的种类有所不同,一般能检测到其中的1～4种双歧杆菌和1～5种乳杆菌;长双歧杆菌和假小链双歧杆菌的平均数量多达107CFUg(湿重),检出率分别为90.48%和85.71%,为儿童肠道内双歧杆菌的优势菌种;L.mucosae和发酵乳杆菌的数量较多,平均为3.68log10CFUg(湿重)和3.97log10CFUg(湿重),检出率分别为71.43%和52.38%,为稳定定植于儿童肠道内的优势乳杆菌;不同种类的益生菌在不同样本之间的数量组成均存在有很大差异,双歧杆菌的样本差异为1.86～3.85,乳杆菌的为2.43～4.07。     

Role of Glycoside Phosphorylases in Mannose Foraging by Human Gut Bacteria

To metabolize both dietary fiber constituent carbohydrates and host glycans lining the intestinal epithelium, gut bacteria produce a wide range of carbohydrate-active enzymes, of which glycoside hydrolases are the main components. In this study, we describe the ability of phosphorylases to participate in the breakdown of human N-glycans, from an analysis of the substrate specificity of UhgbMP, a mannoside phosphorylase of the GH130 protein family discovered by functional metagenomics. UhgbMP is found to phosphorolyze β-d-Manp-1,4-β-d-GlcpNAc-1,4-d-GlcpNAc and is also a highly efficient enzyme to catalyze the synthesis of this precious N-glycan core oligosaccharide by reverse phosphorolysis. Analysis of sequence conservation within family GH130, mapped on a three-dimensional model of UhgbMP and supported by site-directed mutagenesis results, revealed two GH130 subfamilies and allowed the identification of key residues responsible for catalysis and substrate specificity. The analysis of the genomic context of 65 known GH130 sequences belonging to human gut bacteria indicates that the enzymes of the GH130_1 subfamily would be involved in mannan catabolism, whereas the enzymes belonging to the GH130_2 subfamily would rather work in synergy with glycoside hydrolases of the GH92 and GH18 families in the breakdown of N-glycans. The use of GH130 inhibitors as therapeutic agents or functional foods could thus be considered as an innovative strategy to inhibit N-glycan degradation, with the ultimate goal of protecting, or restoring, the epithelial barrier.     

The protective effect of trefoil factor 3 on the intestinal tight junction barrier is mediated by toll-like receptor 2 via a PI3K/Akt dependent mechanism

Trefoil factor peptides are highly conserved secreted molecules characterized by heat and enzymatic digestion resistance. Intestinal trefoil factor 3 (TFF3) protects and repairs the gastrointestinal mucosa and restores normal intestinal permeability, which is dependent on the integrity of the tight junction (TJ) barrier and the TJ associated proteins claudin-1, zona occludens-1 (ZO-1) and occludin. Despite the important role of intestinal barrier dysfunction in the pathogenesis of inflammatory bowel diseases, the underlying mechanisms and associated molecules remain unclear. In the present study, we show that TFF3 and toll-like receptor 2 (TLR2) are functionally linked and modulate intestinal epithelial permeability via a mechanism that involves the PI3K/Akt pathway. We used the Caco-2 cell model to show that TLR2 and TFF3 inhibit the IL-1β induced increase in permeability and release of proinflammatory cytokines, and that this effect is mediated by activation of PI3K/Akt signaling. TLR2 silencing downregulated the expression of TFF3 and overexpression of TLR2 and TFF3 increased the levels of phospho-Akt. TFF3 overexpression significantly upregulated the expression of ZO-1, occludin and claudin-1 and this effect was abrogated by inhibition of the PI3K/Akt pathway. Taken together, our results indicate that TLR2 signaling selectively enhances intestinal TJ barrier integrity through a mechanism involving TFF3 and the activation of the PI3K/Akt pathway.     

中药甘草对大鼠肠平滑肌运动的影响

目的观察甘草对大鼠肠道平滑肌运动的影响,了解甘草与胃肠运动之间的关系。方法实验分成正常组、甘草制成煎剂4．8、16、32、64g／kg剂量组,每日1次灌胃给药。末次给药1h后观察大鼠胃半排时间;采用灌胃给予炭末,测定胃推进率。结果甘草煎剂剂量大小对大鼠小肠蠕动有直接的影响,较小剂量对大鼠小肠的推进功能有抑制作用,较大剂量对大鼠的肠推进有促进作用。     

抗性淀粉对HFA小鼠肠道菌群的影响

目的 以人源菌群(HFA)小鼠为研究模型,观察抗性淀粉(RS)对高脂饮食诱导的肥胖小鼠肠道菌群的多样性的影响.方法 将30只无菌小鼠接种健康人志愿者的粪便悬液构建HFA小鼠模型后,随机分成3组,一组喂养含20％的抗性淀粉的高脂饲料(RS组),一组喂养纯高脂饲料(CK组),一组喂养普通饲料(CONV组),取第0周和第8周的小鼠新鲜粪便,用PCR-DGGE分析3组小鼠的肠道菌群的相似性和多样性.结果 3组小鼠在第0周时肠道菌群多样性的相似度达到79％～87％,与人的肠道菌群相似性达到39％,说明构建HFA小鼠模型成功,第8周时,3组之间的均匀度(E)和Shannon指数差异无统计学意义(P＞0.05),而丰富度(S)在高脂组(CK)与普通饲料组(CONV)和抗性淀粉组(RS)之间差异都有统计学意义(P＜0.05),说明高脂饮食引起肠道菌群多样性增加,而抗性淀粉则能降低这种多样性.结论 抗性淀粉可以显著影响HFA小鼠的肠道菌群多样性.