Bidirectional effects of the tryptophan metabolite indole-3-acetaldehyde on colorectal cancer

BACKGROUND Colorectal cancer(CRC)has a high incidence and mortality.Recent studies have shown that indole derivatives involved in gut microbiota metabolism can impact the tumorigenesis,progression,and metastasis of CRC.AIM To investigate the effect of indole-3-acetaldehyde(IAAD)on CRC.METHODS The effect of IAAD was evaluated in a syngeneic mouse model of CRC and CRC cell lines(HCT116 and DLD-1).Cell proliferation was assessed by Ki-67 fluorescence staining and cytotoxicity tests.Cell apoptosis was analysed by flow cytometry after staining with Annexin V-fluorescein isothiocyanate and propidium iodide.Invasiveness was investigated using the transwell assay.Western blotting and real-time fluorescence quantitative polymerase chain reaction were performed to evaluate the expression of epithelial-mesenchymal transition related genes and aryl hydrocarbon receptor(AhR)downstream genes.The PharmMapper,SEA,and SWISS databases were used to screen for potential target proteins of IAAD,and the core proteins were identified through the String database.RESULTS IAAD reduced tumorigenesis in a syngeneic mouse model.In CRC cell lines HCT116 and DLD1,IAAD exhibited cytotoxicity starting at 24 h of treatment,while it reduced Ki67 expression in the nucleus.The results of flow cytometry showed that IAAD induced apoptosis in HCT116 cells but had no effect on DLD1 cells,which may be related to the activation of AhR.IAAD can also increase the invasiveness and epithelial-mesenchymal transition of HCT116 and DLD1 cells.At low concentrations(<12.5μmol/L),IAAD only exhibited cytotoxic effects without promoting cell invasion.In addition,predictions based on online databases,protein-protein interaction analysis,and molecular docking showed that IAAD can bind to matrix metalloproteinase-9(MMP9),angiotensin converting enzyme(ACE),poly(ADP-ribose)polymerase-1(PARP1),matrix metalloproteinase-2(MMP2),and myeloperoxidase(MPO).CONCLUSION Indole-3-aldehyde can induce cell apoptosis and inhibit cell proliferation to prevent the occurrence of CRC;however,at high concentrations(≥25μmol/L),it can also promote epithelial-mesenchymal transition and invasion in CRC cells.IAAD activates AhR and directly binds MMP9,ACE,PARP1,MMP2,and MPO,which partly reveals why it has a bidirectional effect.

Expression of Recombinant Tryptophan Decarboxylase in Different Subcellular Compartments in Tobacco Plant

The gene encoded for tryptophan decarboxylase (TDC), which is the key enzyme in terpenoil indole alkaloids pathway, was targeted to different subcellular compartments and stably expressed in transgenic tobacco (Nicotiana tabacum L.) plants at the levels detected by Western blot and tryptamine accumulation analysis. It was shown that the TDC was located in subcellular compartments, the chloroplasts and cytosol. The recombinant TDC targeted to chloroplasts and cytosol in tobacco plants was effectively expressed as soluble protein by Western blot analysis and enzymatic assay. The level of tryptamine accumulation in chloroplast was higher than that in cytosol and very low in vacuole and endoplasmic reticulum (ER) to be hardly detected by Western blot analysis. It was indicated that the highest amount of tryptamine was in chloroplasts, lower in endoplasmic reticula and the lowest in vacuoles as compared to those in wild type plants. The TDC targeted to different subcellular compartments of tobacco plants and its expression level were studied by different nucleotide sequences coding signal peptides at 5'-end of tdc gene in order to know the effects of the TDC in compartmentation on its functionality.

The Dependence of <i>N</i>-Malonyltryptophan Formation in Plants on Water Deficit (Review)

Drought stress in plants is accompanied by several metabolic changes. One of them is the appearance of N-malonyltryptophan (MT) during leaf wilting of many species, but there is a significant number of plant species in which the appearance of MT did not occur. Plants of some species were able to synthesize also N-acetyltryptophan (AT). Excised tomato leaves incubated with D-amino acids (including D-Trp) transform them into malonyl- and acetyl-derivatives even without water deficit. However, MT which appeared during water deficit has been shown to contain L-Trp. Amino acid—1-amino-cyclopropane-1-carboxylic acid (ACC) is also malonylated during water deficit, but other L-amino acids were not malonylated. N-malonyl transferases specific for Trp and ACC have been found in several plants. The existence of N-malonyltransferase specific to L-Trp and appeared during water deficit in plants forming MT is supposed, but clear experimental proof has not been obtained yet. Plants can transform MT applied exogenously into Trp and further to indole-3-acetic acid (IAA). But no evidence has been appeared up to now that endogenous MT may be a source of IAA. It is unknown till now why it is necessary for plants of many species to malonylate only Trp during water deficit. How MT metabolized in animals and if it affects them is also unknown. The necessity to use molecular-genetic approaches for the elucidation of the physiological significance of MT formation during water deficit is underlined.

Helicobacter pylori and serum kynurenine-tryptophan ratio in patients with colorectal cancer

AIM: To evaluate how Helicobacter pylori(H. pylori) is able to evade the immune response and whether it enhances systemic immune tolerance against colorectal cancer.METHODS: This prospective randomized study involved 97 consecutive colorectal cancer patients and 108 cancer-free patients with extra-digestive diseases. Colorectal cancer and cancer-free patients were assigned into subgroups according to H. pylori Ig G seropositivity. Exposure to H. pylori was determined by Ig G seropositivity which was detected by enzyme linked immunoassay(ELISA). Serum neopterin levels were measured by ELISA. Serum tryptophan, kynurenine, and urinary biopterin concentrations were measured by high performance liquid chromatography. Serum nitrite levels were detected spectrophotometrically. Serum indoleamine 2,3-dioxygenase activity was estimated by the kynurenine to tryptophan ratio and by assessing the correlation between serum neopterin concentrations and the kynurenine to tryptophan ratio. The frequencies of increased serum kynurenine to tryptophan ratio of H. pylori seronegative and seropositive colorectal cancer subgroups were estimated by comparing them with the average kynurenine to tryptophan ratio of H. pylori seronegative tumor-free patients.RESULTS: Compared with respective controls, in both H. pylori seronegative and seropositive colorectal cancer patients, while serum tryptophan levels were decreased(controls vs patients; seronegative: 20.37 ± 0.89 μmol/L vs 15.71 ± 1.16 μmol/L, P < 0.05; seropositive: 20.71 ± 0.81 μmol/L vs 14.97 ± 0.79 μmol/L, P < 0.01) the kynurenine to tryptophan ratio was significantly increased(controls vs patients; seronegative: 52.85± 11.85 μmol/mmol vs 78.91 ± 8.68 μmol/mmol, P < 0.01, seropositive: 47.31 ± 5.93 μmol/mmol vs 109.65 ± 11.50 μmol/mmol, P < 0.01). Neopterin concentrations in cancer patients were significantly elevated compared with controls(P < 0.05). There was a significant correlation between serum neopterin levels and kynurenine/tryptophan in control and colorectal cancer patients groups(r s = 0.494, P = 0.0001 and r s= 0.293, P = 0.004, respectively). Serum nitrite levels of H. pylori seropositive cancer cases were significantly decreased compared with seropositive controls(controls vs patients; 26.04 ± 2.39 μmol/L vs 20.41 ± 1.48 μmol/L, P < 0.05) The decrease in the nitrite levels of H. pylori seropositive cancer patients may be attributed to excessive formation of peroxynitrite and other reactive nitrogen species.CONCLUSION: A significantly high kynurenine/tryptophan suggested that H. pylori may support the immune tolerance leading to cancer development, even without an apparent upper gastrointestinal tract disease.

The effect of dietary tryptophan levels on oxidative stress of liver induced by diquat in weaned piglets

Oxidative stress can induce abnormal tryptophan metabolism. The present study was mainly conducted to determine the effect of dietary tryptophan levels on oxidative stress in the liver of weaned pigs challenged by diquat. A total of 36 PIC piglets weaned at 21 days of age were randomly allotted to 1 of 3 diets containing dietary tryptophan levels of 0.18, 0.30, and 0A5% for 14 d. On day 8, the piglets were injected intraperitoneally with sterile 0.9% NaCI solution or diquat （10 mg/kg body weight）. During the first 7 d of trial, increasing dietary tryptophan levels enhanced average daily gain （P = 0.09） and average daily feed intake （P = 0.08）, and decreased the feed efficiency （P 〈 0.05） of piglets. The growth performance was decreased by diquat injection （P 〈 0.05）. Diquat injection also decreased the activities of the superoxide dismutase （SOD） and glutathione peroxidase （GPx） in the plasma and liver （P 〈 0.05）, increased plasma malondialdehyde （MDA） （P 〈 0.05） and urea nitrogen （P 〈 0.05） concentrations, and enhanced MDA concentration （P = 0.09） and tryptophan 2,3-dioxygenase （TDO） activity （P = 0.07） in liver of piglets. Increasing dietary tryptophan levels could attenuate the effects of diquat injection on the MDA （P = 0.06） concentration and the activities of SOD （P = 0.09） and GPx （P = 0.05） of the liver, and plasma urea nitrogen （P = 0.06） concentration in the piglet. There was a synergistic role for increasing TDO activity in the liver between dietary tryptophan levels and diquat injection （P 〈 0.05）. These results suggest that increasing dietary tryptophan levels could attenuate the oxidative stress of the liver in weaned piglets intraperitoneally injected with diquat via enhancing the antioxidant capacity.

Effects of dietary tryptophan and stocking density on the performance,meat quality,and metabolic status of broilers

Background： Highly automated cage-rearing systems are becoming increasingly popular in China. However, a high stocking density can cause oxidative stress and decrease broiler performance. The tryptophan （TRP） derivative 5-hydroxytryptophan （5-HT） has been shown to preserve membrane fluidity in birds suffering from oxidative stress Therefore, this experiment was conducted to determine the effects of dietan/TRP supplementation on performance, breast meat quality and oxidative stress in broilers reared in cages with a high or low stocking density. Methods： Female Arbor Acres broilers （25-d-old, n = 144） were randomly allocated to 1 of 4 treatments. The birds were fed a diet based on corn, soybean meal, cottonseed meal and corn gluten meal containing either 0.18 or 0.27% TRP and were housed with stocking densities of 11 or 15.4 birds/m2 in a 2 x 2 factorial experiment. Broiler performance was evaluated from d 25 to 42. Eight birds from each treatment were slaughtered on d 42 and plasma and breast muscle samples were collected to measure biochemical indices. Results： A higher stocking density tended to be associated with reduced weight gain （P 〈 0.10）, and significantly increased plasma glutamic-pyruvic transaminase （GPT） activity （P 〈 0.001）. Increased dietary TRP significantly reduced the activities of lactic dehydrogenase and GPT while increasing total cholesterol in the plasma （P 〈 0.01）, reducing drip loss of breast muscle （P 〈 0.10） and improving feed efficiency （P 〈 0.10）. Conclusions： An increase in dietary TRP, ].S-fold higher than the standard supplementation level, can alleviate oxidative stress as well as improve welfare and feed efficiency in broilers reared in cages with a high stocking density.

Changes of 5-hydroxytryptamine and tryptophan hydroxylase expression in the ventral horn of spinal cord

Objective To investigate changes of 5-hydroxytryptamine （5-HT） and its synthesis rate-limiting enzyme tryp-tophan hydroxylase （TPH） in the ventral horn of spinal cord after exercise-induced fatigue, and to further discuss the mecha- nism of exercise-induced central fatigue at spinal level. Methods Sixteen healthy adult Wistar rats were randomly divided into 2 groups： exercise-induced fatigue group and control group. Immunohistochemical staining for 5-HT and TPH in the ventral horn were performed and analysized quantitatively. The mean optic densities of 5-HT and TPH positive fibers or terminals were measured by computerized image analyzer. Results Both 5-HT and TPH positive fibers/terminals decreased in the exercise-induced fatigue group. The immunohistochemical staining was weaker and the mean optic densities decreased obviously in the fatigue group compared with those in the control group （P 〈 0.05）. Conclusion 5-HT and TPH in the ventral horn of spinal cord might be involved in exercise-induced fatigue.

Generation of tryptophan hydroxylase 2 gene knockout pigs by CRISPR/Cas9-mediated gene targeting

Unbalanced brain serotonin(5-HT) levels have implications in various behavioral abnormalities and neuropsychiatric disorders. The biosynthesis of neuronal 5-HT is regulated by the rate-limiting enzyme, tryptophan hydroxylase-2(TPH2). In the present study, the clustered regularly interspaced short palindromic repeat(CRISPR)/CRISPR-associated(Cas) system was used to target the Tph2 gene in Bama mini pig fetal fibroblasts. It was found that CRISPR/Cas9 targeting efficiency could be as high as 61.5%, and the biallelic mutation efficiency reached at38.5%. The biallelic modified colonies were used as donors for somatic cell nuclear transfer(SCNT) and 10 Tph2 targeted piglets were successfully generated. These Tph2 KO piglets were viable and appeared normal at the birth.However, their central 5-HT levels were dramatically reduced, and their survival and growth rates were impaired before weaning. These Tph2 KO pigs are valuable large-animal models for studies of 5-HT deficiency induced behavior abnomality.

Lysine, Methionine and Tryptophan Requirements of Beijing Ducklings of 0-2 Weeks of Age

A feed trial was conducted with a total of 1 134 Beijing ducklings to study the optimum level of dietary lysine （Lys） （0.95, 1.10, 1.25%）, methionine （Met） （0.26, 0.46, 0.66%） and tryptophan （Trp） （0.20, 0.30, 0.40%） for those ducklings during a phase of 0-2 weeks. Ducklings were randomly allotted to 27 groups according to a 3 × 3× 3 factorial arrangement and fed a basal corn-soybean-peanut meal diet containing 20.26% CP, 12.45 MJ kg^-1 ME. The results from this study indicate that Lys affected body weight （P〈0.01）, feed intake （0-14 d） （P〈0.01）, but had no effect on feed/gain （0-14 d） （P〉0.05）, uric acid concentration （P 〉 0.05）. Methionine influenced body weight （P 〈 0.01）, feed/gain （P 〈 0.05）, and feed intake （P 〈 0.01）. Tryphtophan had no effect on indices measured. The requirement of the Lys and Met for Beijing ducklings of 0-2 weeks of age were 1.10 and 0.46%. The requirement of Trp for Beijing ducklings of 0-2 weeks of age was not more than 0.20%.

Tryptophan:A gut microbiota-derived metabolites regulating inflammation

Inflammatory bowel diseases(IBD), which comprise Crohn's disease and ulcerative colitis, are chronic intestinal disorders with an increased prevalence and incidence over the last decade in many different regions over the world. The etiology of IBD is still not well defined, but evidence suggest that it results from per-turbation of the homeostasis between the intestinal microbiota and the mucosal immune system, with the involvement of both genetic and environmental factors. Genome wide association studies, which involve large-scale genome-wide screening of potential polymorphism, have identified several mutations associated with IBD. Among them, Card9, a gene encoding an adapter molecule involved in innate immune response to fungi(via type C-lectin sensing) through the activation of IL-22 signaling pathway, has been identified as one IBD susceptible genes. Dietary compounds, which represent a source of energy and metabolites for gut bacteria, are also appreciated to be important actors in the etiology of IBD, for example by altering gut microbiota composition and by regulating the generation of short chain fatty acids. A noteworthy study published in the June 2016 issue of Nature Medicine by Lamas and colleagues investigates the interaction between Card9 and the gut microbiota in the generation of the microbiota-derived tryptophan metabolite. This study highlights the role of tryptophan in dampening intestinal inflammation in susceptible hosts.

Chemical Modification and Fluorescence Spectrum of Tryptophan Residues in Pullulanase

Tryptophan（Trp） residues in a pullulanase were modified by N-bromosuccinimide（NBS）. The results of the Spande method indicate that there are 18 Trp residues in the pullulanase and nine of them are located on the surface af the enzyme. Three of these Trp residues are nonessential residues which show the fastest reaction rate according to the Zou＇s plot. Two of the seven relative faster reacting residues are essential for the activity of the enzyme. The other eight are the slowest in the reaction rate or non-reactive residues for the reaction. The fluorescence and circular dichroism（CD） spectra of the pullulanase have been changed after the reaction with NBS. Potassium iodide（KI） and acrylamide also have remarkable influences on the fluorescence spectra of the pullulanase.

Compared efficacy of University of Wisconsin and histidine-tryptophan-ketoglutarate solutions in ex-situ liver resection and autotransplantation for end-stage hepatic alveolar echinococcosis patients

Background: The University of Wisconsin (UW) and histidine-tryptophan-ketoglutarate (HTK) solutions are the two most frequently used liver graft preservation fluids. The present study aimed to compare their efficacy in end-stage hepatic alveolar echinococcosis patients who underwent ex-situ liver resection and autotransplantation (ELRA). Methods: A total of 81 patients received ELRA from August 2010 to March 2018. They were allocated into UW ( n = 48) and HTK groups ( n = 33) based on the type of solutions used. Demographic and operational data were retrospectively analyzed. Primary outcomes included 90-day mortality, incidence of early graft loss, primary dysfunction, and postoperative complications. Results: Demographic and operational characteristics were similarly distributed in the two groups. No statistically significant differences were observed with regard to 90-day mortality (12.77% vs. 12.12%) and early graft loss rate (8.51% vs. 9.09%) between the two groups. Patients in the UW and HTK groups showed a primary dysfunction rate of 27.66% and 27.27%, respectively. The UW group exhibited a higher incidence tendency of biliary complications, albeit with no statistical significance. Conclusions: This is the largest cohort study comparing the efficacy of the UW and HTK organ-preserving solutions in end-stage hepatic alveolar echinococcosis patients in ELRA settings. UW and HTK solutions presented similar efficacy and safety. A randomized clinical trial with larger scale is needed for further investigation in future clinical applications.

Pectin modulates intestinal immunity in a pig model via regulating the gut microbiota-derived tryptophan metabolite-AhR-IL22 pathway

Background Pectin is a heteropolysaccharide that acts as an intestinal immunomodulator,promoting intestinal development and regulating intestinal flora in the gut.However,the relevant mechanisms remain obscure.In this study,pigs were fed a corn-soybean meal-based diet supplemented with either 5%microcrystalline cellulose(MCC)or 5%pectin for 3 weeks,to investigate the metabolites and anti-inflammatory properties of the jejunum.Result The results showed that dietary pectin supplementation improved intestinal integrity(Claudin-1,Occludin)and inflammatory response[interleukin(IL)-10],and the expression of proinflammatory cytokines(IL-1β,IL-6,IL-8,TNF-α)was down-regulated in the jejunum.Moreover,pectin supplementation altered the jejunal microbiome and tryptophan-related metabolites in piglets.Pectin specifically increased the abundance of Lactococcus,Enterococcus,and the microbiota-derived metabolites(skatole(ST),3-indoleacetic acid(IAA),3-indolepropionic acid(IPA),5-hydroxyindole-3-acetic acid(HIAA),and tryptamine(Tpm)),which activated the aryl hydrocarbon receptor(AhR)pathway.AhR activation modulates IL-22 and its downstream pathways.Correlation analysis revealed the potential relationship between metabolites and intestinal morphology,intestinal gene expression,and cytokine levels.Conclusion In conclusion,these results indicated that pectin inhibits the inflammatory response by enhancing the AhR-IL22-signal transducer and activator of transcription 3 signaling pathway,which is activated through tryptophan metabolites.

Flow-injection chemiluminescence determination of tryptophan using galangin-potassium permanganate-polyphosphoric acid system

A high sensitive flow-injection chemiluminescence （FI-CL） method for the determination of tryptophan has been developed. The method is based on the chemiluminescence reaction of galangin-potassium permanganate-tryptophan in polyphosphoric acid （PPA） media. Under the optimized conditions, tryptophan was determined in the range 0.05-10 μg/mL with the detection limit （3tr） of 5.0 × 10^-3 μg/mL. The relative standard deviation （RSD） was 1.0% for 11 replicate determinations of 1.0 μg/mL tryptophan. Three synthetic samples were determined selectively with recoveries in the range from 99.6% to 102.0% in the presence of other amino acids.

Alteration of fecal tryptophan metabolism correlates with shifted microbiota and may be involved in pathogenesis of colorectal cancer

BACKGROUND Gut tryptophan(Trp)metabolites are produced by microbiota and/or host metabolism.Some of them have been proven to promote or inhibit colorectal cancer(CRC)in vitro and animal models.We hypothesized that there is an alteration of gut Trp metabolism mediated by microbiota and that it might be involved in the pathogenesis of cancer in patients with CRC.AIM To investigate the features of Trp metabolism in CRC and the correlation between fecal Trp metabolites and gut microbiota.METHODS Seventy-nine patients with colorectal neoplastic lesions(33 with colon adenoma and 46 with sporadic CRC)and 38 healthy controls(HCs)meeting the inclusion and exclusion criteria were included in the study.Their demographic and clinical features were collected.Fecal Trp,kynurenine(KYN),and indoles(metabolites of Trp metabolized by gut microbiota)were examined by ultraperformance liquid chromatography coupled to tandem mass spectrometry.Gut barrier marker and indoleamine 2,3-dioxygenase 1(IDO1)mRNA were analyzed by quantitative realtime polymerase chain reaction.Zonula occludens-1(ZO-1)protein expression was analyzed by immunohistochemistry.The gut microbiota was detected by 16S ribosomal RNA gene sequencing.Correlations between fecal metabolites and other parameters were examined in all patients.RESULTS The absolute concentration of KYN[1.51(0.70,3.46)nmol/g vs 0.81(0.64,1.57)nmol/g,P=0.036]and the ratio of KYN to Trp[7.39(4.12,11.72)×10^-3 vs 5.23(1.86,7.99)×10^-3,P=0.032]were increased in the feces of patients with CRC compared to HCs,while the indoles to Trp ratio was decreased[1.34(0.70,2.63)vs 2.46(1.25,4.10),P=0.029].The relative ZO-1 mRNA levels in patients with CRC(0.27±0.24)were significantly lower than those in HCs(1.00±0.31)(P<0.001),and the relative IDO1 mRNA levels in patients with CRC[1.65(0.47-2.46)]were increased(P=0.035).IDO1 mRNA levels were positively associated with the KYN/Trp ratio(r=0.327,P=0.003).ZO-1 mRNA and protein levels were positively correlated with the indoles/Trp ratio(P=0.035 and P=0.009,respectively).In addition,the genera Asaccharobacter(Actinobacteria)and Parabacteroides(Bacteroidetes),and members of the phylum Firmicutes(Clostridium XlVb,Fusicatenibacter,Anaerofilum,and Anaerostipes)decreased in CRC and exhibited a positive correlation with indoles in all subjects.CONCLUSION Alteration of fecal Trp metabolism mediated by microbiota is associated with intestinal barrier function and tissue Trp metabolism,and may be involved in the pathogenesis of CRC.

Determination of Enantiomeric Compositions of Tryptophan by Chemometric Analysis of the Fluorescence Spectra of Bovine Serum Albumin Receptor-ligand Mixtures

In this work, a novel method was constructed to determine the enantiomeric composition of tryptophan （Trp） by bovine serum albumin （BSA） based on the fluorescence spectra of the receptor-ligand mixtures coupled with partial least squares （PLS-1） analysis. As a result the enantiomeric composition of Trp was accurately determined.

Cycloaddition of CO_2 with epoxides by using an amino-acid-based Cu(Ⅱ)–tryptophan MOF catalyst

Metal organic frameworks(MOFs)constructed from natural/biological units(amino acids)are prospective candidates as catalysts in CO2chemistry owing to their natural origin and high abundance of Lewis acid/base sites and functional groups.Herein,we report the catalytic efficiency of an amino‐acid‐based Cu‐containing MOF,denoted as CuTrp(Trp=L‐tryptophan).The CuTrp catalyst was synthesized by direct mixing at room temperature using methanol as a solvent-a synthetic route with notable energy efficiency.The catalyst was characterized using various physicochemical techniques,including XRD,FT‐IR,TGA,XPS,ICP‐OES,FE‐SEM,and BET analysis.The catalytic activity of CuTrp was assessed in the synthesis of cyclic carbonates from epoxides and CO2.The CuTrp operated in synergy with the co‐catalyst tetrabutylammonium bromide under solvent‐free conditions.Several reaction parameters were studied to identify the optimal reaction conditions and a reaction mechanism was proposed based on experimental evidence and previous density functional theory studies.The CuTrp also exhibited satisfactory stability in water and could be reused more than three times without any significant loss of activity.?2018,Dalian Institute of Chemical Physics,Chinese Academy of Sciences.Published by Elsevier B.V.All rights reserved.

Preparation and evaluation of mixed-mode resins with tryptophan analogues as functional ligands for human serum albumin separation

Five tryptophan analogues with a hydrophobic indole ring and an amino group on each molecule were used as functional ligands of mixed-mode resins for human serum albumin(HSA) purification. Their adsorption performance was evaluated and the effects of p H and salt addition on HSA adsorption were studied. The resins prepared showed typical p H-dependent adsorption and the highest adsorption capacity and affinity were found at pH 5.0for all the resins tested. The saturated adsorption capacity was 138.02 mg·g^(-1)with the tryptaminefunctionalized resin, which significantly decreased at p H below 4.0 due to electrostatic repulsion between ligands and HSA. Moreover, the addition of Na Cl or(NH_4)_2SO_4in media reduced HSA adsorption capacity, although the two salts showed different affecting profiles. The tryptamine-functionalized resin showed the best salt-tolerant performance, and its high adsorption capacity was maintained under high salt concentrations. In addition, the five resins prepared showed good adsorption selectivity for recombinant HSA from Pichia pastoris broth. Molecular docking results between tryptamine and HSA indicated that tryptamine was favorable to bind on Site II(indole-binding site) of HSA.

Chiral ionic liquids as chiral selectors for separation of tryptophan enantiomers by ligand exchange chromatography

Chiral ionic liquids (CILs) containing imidazolium cations and L-Proline (L-Pro) anions were applied as chiral selector to separate tryptophan (Trp) enantiomers on a C18 column by ligand exchange chromatography. Several factors influencing Trp enantiomers separation, such as alkyl chain length of CILs, concentrations of Cu2+ and CILs, pH of the mobile phase, flow rate, organic solvent and temperature, were studied. Under the optimal conditions, the Trp enantiomers could be successfully separated within 21 min with the resolution of 2.30. At the same time, some thermodynamical parameters were obtained. The experimental results show that the enthalpy values of the Trp enantiomers are negative, indicating that the separation process is exothermic. And the enthalpy values of D-Trp are larger than those of L-Trp, which indicates that L-Trp could form more stable ternary complexes with tryptophan enantiomers.

Measurement of Tryptophan Metabolites in Healthy Old Men and Patients of Type 2 Diabetes Mellitus (T2DM)

Background: Plasma levels of tryptophan (TRP) metabolites have not been measured extensively in patients of type 2 diabetes mellitus (T2DM). Methods: Metabolites analysis was performed by a liquid chromatograph tandem mass spectrometer, the LCMS-8060 quadrupole mass spectrometer combined with Nexera X2 liquid chromatograph system (Shimadzu Corporation, Kyoto, Japan). Body mass index (BMI) and TRP metabolites have been measured in healthy old men (n = 20) and patients of T2DM (n = 20). TRP metabolites were measured by using the ultrahigh speed liquid chromatography-mass spectros-copy (Shimadzu Corporation). Results: The plasma levels of 5-hydroxytryptophan (5-HTRP), 5-hydroxyindoleacetic acid (5-HIAA), kynurenic acid (KNA), 3-hydroxykynurenine (3-HKN), and 3-hydroxyanthranilic acid (3-HAA) were higher in patients of T2DM than healthy old men. Since 5HTRP and 5-HIAA belong to the serotonin pathway, and KNA, 3-HKN, and 3-HAA belong to the KN pathway of TRP metabolism, these pathways were activated more in the patients of T2DM. Since plasma levels of Indole-3-acetic acid were not elevated in T2DM, that pathway was not activated more in T2DM. Serotonin levels were not increased but 5-HIAA levels were increased in the plasma of T2DM patients, which may mean that serotonin was quickly metabolized to 5-HIAA in the patients of T2DM. Conclusion: Plasma levels of tryptophan metabolites in serotonin and kynurenine pathways increased in T2DM patients. Obesity expressed by BMI may not influence tryptophan metabolism in healthy old men and T2DM patients. These results indicate that our new method of the simultaneous measurements of all the tryptophan metabolites is the powerful measure to identify factor related to endogenous stresses seen in DM.