Metabolites Associated with Early Cognitive Changes Implicated in Alzheimer's Disease

BACKGROUND

Understanding metabolic mechanisms associated with cognitive changes preceding an Alzheimer's disease (AD) diagnosis could advance our understanding of AD progression and inform preventive methods.

OBJECTIVE

We investigated the metabolomics of the early changes in executive function and delayed recall, the earliest aspects of cognitive function to change in the course of AD development, in order to better understand mechanisms that could contribute to early stages and progression of this disease.

METHODS

This investigation used longitudinal plasma samples from the Wisconsin Registry for Alzheimer's Prevention (WRAP), a cohort of participants who were dementia free at enrollment and enriched with a parental history of AD. Metabolomic profiles were quantified for 2,324 fasting plasma samples among 1,200 participants, each with up to three study visits, which occurred every two years. Metabolites were individually tested for association with executive function and delayed recall trajectories across age.

RESULTS

Of 1,097 metabolites tested, levels of seven were associated with executive function trajectories, including an amino acid cysteine S-sulfate and three fatty acids, including erucate (22 : 1n9), while none were associated with delayed recall trajectories. Replication was attempted for four of these metabolites that were present in the Vietnam Era Twin Study of Aging (VETSA). Although none reached statistical significance, three of these associations showed consistent effectdirections.

CONCLUSION

Our results suggest potential metabolomic mechanisms that could contribute to the earliest signs of cognitive decline. In particular, fatty acids may be associated with cognition in a manner that is more complex than previously suspected.

Ratiometric fluorescence assay for L-Cysteine based on Fe-doped carbon dot nanozymes

In this work, a ratiometric fluorescence method based on nanozyme was fabricated to determine L-Cysteine. Taking silkworm feces as a carbon source, together with Fe³⁺, Fe-doped carbon dots (Fe-CDs) were synthesized through a hydrothermal method. Fe-CDs were able to oxidize the enzyme substrate o-phenylenediamine (OPD) to produce oxidized OPD (Ox-OPD) when H₂O₂ coexisted with them. Based on the fluorescence property of Fe-CDs and Ox-OPD, a dual-emission system was built. Since L-Cysteine contains reductive thiols that can inhibit the production of Ox-OPD, the addition of L-Cysteine caused a decrease in the fluorescence intensity of Ox-OPD. The results showed that the ratio of fluorescence intensities at 450 and 560 nm (I₄₅₀/I₅₆₀) varied linearly with the concentration of L-Cysteine in the range of 0.25-90 μM and the limit of detection is as low as 0.047 μM. Furthermore, using this ratiometric fluorescence system to determine L-Cysteine in serum and tap-water samples, average recoveries were evaluated to reach 98.75%-103.27% with the relative standard deviation of no more than 4.5%. Based on the fluorescence property and nanozyme-like activity, this work provides an inspiration to open a new horizon in using natural carbon source to synthesize CDs and for the application of CDs as a nanozyme.

Association of Plasma Total Cysteine and Anthropometric Status in 6-30 Months Old Indian Children

High-quality protein has been associated with child growth; however, the role of the amino acid cysteine remains unclear. The aim was to measure the extent to which plasma total cysteine (tCys) concentration is associated with anthropometric status in children aged 6–30 months living in New Delhi, India. The study was a prospective cohort study including 2102 children. We calculated Z-scores for height-for-age (HAZ), weight-for-height (WHZ), or weight-for-age (WAZ) according to the WHO Child Growth Standards. We used multiple regression models to estimate the association between tCys and the anthropometric indices. A high proportion of the children were categorized as malnourished at enrolment; 41% were stunted (HAZ ≤ −2), 19% were wasted (WHZ ≤ −2) and 42% underweight (WAZ ≤ −2). Plasma total cysteine (tCys) was significantly associated with HAZ, WHZ and WAZ after adjusting for relevant confounders (p < 0.001). Low tCys (≤25th percentile) was associated with a decrease of 0.28 Z-scores for HAZ, 0.10 Z-scores for WHZ, and 0.21 Z-scores for WAZ compared to being >25th percentile. In young Indian children from low-to-middle socioeconomic neighborhoods, a low plasma total cysteine concentration was associated with an increased risk of poor anthropometric status.

Association of Maternal Plasma Total Cysteine and Growth among Infants in Nepal: A Cohort Study

Cysteine is a semi-essential amino acid that has been positively associated with growth in children. However, transgenerational effects remain unclear. The aim of this analysis was to assess whether maternal plasma total cysteine (tCys) concentration is associated with various growth indicators in infants living in peri-urban settings in Bhaktapur, Nepal. We used data from the 561 mothers enrolled in an ongoing randomized controlled trial. We built linear regression models to evaluate the associations between maternal tCys and birth weight, length-for-age Z-scores (LAZ) and weight-for-length Z-scores (WLZ) at birth and six months of age. Maternal tCys was inversely associated with birth weight among boys after adjusting for confounders (p < 0.05). In addition, there was a negative association between maternal tCys and LAZ at birth (p < 0.01). No associations between maternal tCys and the other anthropometric indicators were found significant, although there was a tendency for maternal tCys to be associated positively with WLZ at birth among girls (p < 0.10). This is a first study evaluating transgenerational relation of tCys on growth in infants. Further, larger and more comprehensive studies are needed to determine if and how maternal tCys alters child growth.

Cysteine is a better predictor of coronary artery disease than conventional homocysteine in high-risk subjects under preventive medication

BACKGROUND AND AIMS

In Portugal, The Azores Archipelago has the highest standardized mortality rate for CAD. Therefore, the aim of this study was to evaluate conventional risk factors, as well as plasma and erythrocyte aminothiol concentration in high-risk Azorean patients undergoing elective coronary angiography and to investigate whether any aminothiol was associated with CAD risk and severity.

METHODS AND RESULTS

174 subjects with symptomatic CAD (age 56±9y; 68% men) submitted to coronary angiography were split into 2 groups: one formed by CAD patients (≥50% stenosis in at least one major coronary vessel) and the other by non-CAD patients (<50% stenosis). Both groups were age-, sex- and BMI-matched. Plasma and erythrocyte aminothiol profiles were evaluated by RP-HPLC/FLD. CAD patients significantly exhibited both higher concentrations of plasma Cys and hypercysteinemia (Cys ≥ 300 μM) prevalence than those in the non-CAD group (261 ± 58 μM vs. 243 ± 56 μM; 22% vs. 10%, respectively). No differences were observed between groups regarding plasma Hcy levels or hyperhomocysteinemia prevalence. After adjustment for several confounders (including Hcy), subjects in the highest quartile of plasma Cys had a 3.31 (95% CI, 1.32-8.30, p = 0.011) fold risk for CAD, compared with those in the lowest quartiles. Furthermore, plasma Cys levels (but not Hcy) tended to increase with the number of stenotic vessels (1VD: 253 ± 64 μM; 2VD: 262 ± 52 μM; 3VD: 279 ± 57 μM, p = 0.129).

CONCLUSION

Hypercysteinemia revealed to be a better predictor of CAD than hyperhomocysteinemia. Moreover, plasma Cys showed to be a useful biomarker for CAD both in primary and secondary preventions, seeming to resist better than Hcy to oral medication therapy.

Influence of Dietary Supplementation for Hyperhomocysteinemia Treatments

Hyperhomocysteinemia is recognized as risk factor for cardiovascular and age-associated diseases. Folic acid supplementation efficiently lowers plasma homocysteine (Hcy) levels, but high intake may negatively affect health because of unnatural levels of unmetabolized folic acid in the systemic circulation. Oxoproline (Oxo) provides by glutamic acid production an increase of intracellular folic acid trapping. Aim of this study was to compare the efficacy of three supplementation protocols: (1) traditional therapy (5-methyl-tetrahydrofolate: 15 mg/day); (2) 5 mL/day of Oxo with 300 μg folic acid (oxifolic); (3) 5 mL/day of Oxo alone (magnesio+) in a 90 days randomized trial on thirty-two moderate hyperhomocysteinemic (18.6 ± 2.4 μmol.L-1) patients (age 48 ± 14 yrs). Thiols: cysteine (Cys), cysteinylglycine (Cys-Gly) and glutathione levels were assessed too. Every supplementation induced significant (p range <0.05-0.0001) reductions of Hcy level and Cys concentration after the three protocols adopted. Otherwise glutathione concentration significantly increased after oxifolic (p < 0.01) and traditional (p < 0.05) supplementation. The integration of Oxo resulted an interesting alternative to traditional therapy because absence or minimal number of folates in the integrator eliminates any chance of excess that can constitute a long-term risk.

Colorimetric determination of cysteine by a paper-based assay system using aspartic acid modified gold nanoparticles

A method is described for cysteine (Cys) determination on paper-based analytical devices using aspartic acid modified gold nanoparticles (Asp-AuNPs). The Asp-AuNPs were characterized by their size, zeta potential, and UV-visible absorption spectrum. After the addition of Cys, it will interact with Asp-AuNPs selectively and leads to the aggregation of Asp-AuNPs. A color change from red to blue can be observed on the paper-based analytical devices. The results were recorded using a cell phone and subsequently analyzed using the Photoshop software. The ratiometric color intensity at red channel and blue channel (Red/Blue) increased linearly in the range 99.9-998.7 μM for Cys (R = 0.9984), and the limit of detection was 1.0 μM. The effects of assay conditions have been investigated and are discussed. The Cys concentration was determined as (0.27 ± 0.02 mM) in human plasma, and the recovery was from 99.2 to 101.1%. Graphical abstract Schematic representation of the paper-based assay system using aspartic acid modified gold nanoparticles (Asp-AuNPs). The ratiometric color intensity method was used for the cysteine (Cys) determination.

Impact of sex, age and diet on the cysteine/cystine and glutathione/glutathione disulfide plasma redox couples in mice

Age, sex and diet are well-established risk factors for several diseases. In humans, each of these variables has been linked to differences in plasma redox potentials (E_h) of the glutathione/glutathione disulfide (GSH/GSSG) and cysteine/cystine (Cys/CySS) redox couples. Mice have been very useful for modeling human disease processes, but it is unknown if age, sex and diet affect redox couples in mice as they do in humans. The purpose of the present study was to examine the effects of these factors on plasma redox potentials in C57BL/6J mice. We found that age had no effect on either redox couple in either sex. Plasma E_h Cys/CySS and E_h GSH/GSSG were both more oxidized (more positive) in females than in males. A 24-hour fast negated the sex differences in both redox potentials by oxidizing both redox couples in male mice, while having no effect on E_h Cys/CySS and a smaller effect on E_h GSH/GSSG in female mice. A diet with excess sulfur amino acids reduced the plasma E_h Cys/CySS in females to a level comparable to that seen in male mice. Thus, sex-specific differences in plasma E_h Cys/CySS could be normalized by two different dietary interventions. Some of these findings are consistent with reported human studies, while others are not. Most strikingly, mice do not exhibit age-dependent oxidation of plasma redox potentials. Care must be taken when designing and interpreting mouse studies to investigate redox regulation in humans.

Synthesis and characterization of maltol capped silver nanoparticles and their potential application as an antimicrobial agent and colorimetric sensor for cysteine

Maltol capped silver nanoparticles (McAgNPs) were synthesized using maltol (3-hydroxy-2-methyl-4-pyrone) as reducing and capping agent. McAgNPs were characterized by Visible and FTIR (Fourier transform infrared) spectroscopy, dynamic light scattering (DLS), and atomic force microscopy (AFM). Bright yellow color McAgNPs showed surface plasmon resonance (SPR) band at 436 nm, spherical shape and the average size between 35 to 50 nm. McAgNPs revealed higher stability against varying storage time, temperature, pH and salt concentrations. McAgNPs were successfully utilized for the selective and highly sensitive colorimetric detection of cysteine (Cys). Addition of Cys in a solution of McAgNPs, resulted a rapid change in color from yellow to orange because of the formation of nanoaggregates as confirmed by Visible/FTIR spectroscopy, DLS, and AFM studies. The estimated limit of detection (0.043 μM) was found to be more sensitive than previously reported other optical methods. The practical applicability of probe was also established by spiking the known concentrations of Cys in biological (blood plasma and urine) and environmental (tap and lake water) samples with significant recovery rates (92-104.6%). Despite being nontoxic to various tested cell lines, McAgNPs demonstrated potent antimicrobial, antibiofilm, and biofilm eradicating activities, thus potentially valuable in diagnostics and/or the synthesis of other nanocomposite material for broader applications.

Carbon dots-based fluorescent turn off/on sensor for highly selective and sensitive detection of Hg2+ and biothiols

In this work, sodium salicylate and ethylenediamine (EDA) are used as the precursors to synthesize green fluorescent carbon dots (CDs). The CDs have some attractive properties, including better oxidation resistance, good water solubility, and excellent stability in high ionic strength solutions in a pH range of 6.0-10.0. Compared to other metal ions, only Hg²⁺ can quench the fluorescence of CDs, and with the introduction of biothiols, the fluorescence of the CDs/Hg²⁺ system can be recovered. Therefore, a turn off/on fluorescent sensor is constructed using CDs as a fluorescent probe, and the sensor is applied to the detection of Hg²⁺ and biothiols (glutathione, homocysteine and cysteine). In addition, the fluorescent sensor exhibits excellent selectivity and sensitivity. The linear range of Hg²⁺ is 0.05-10 μM with the detection limit of 44 nM. Glutathione, homocysteine, and cysteine have a linear response in the range of 0.5-10 μM with the limit of detection of 80, 76, and 69 nM, respectively. Furthermore, the fluorescence method is successfully used to detect Hg²⁺ in actual water samples and biothiols in human plasma.

Plasma cysteine/cystine and glutathione/glutathione disulfide redox potentials in HIV and COPD patients

Chronic obstructive pulmonary disease (COPD) is prevalent in patients infected with HIV. The purpose of this study was to test the hypothesis that systemic oxidation correlates with loss of lung function in subjects with COPD, and that HIV infection can contribute to creating such an environment. Subjects were recruited at the University of Louisville in the following groups: HIV-infected (n = 36), COPD (n = 32), HIV and COPD (n = 28), and uninfected controls with normal lung function (n = 34). HIV infection was assessed by viral load and CD4 cell counts. Pulmonary function was determined by spirometry, and plasma was collected for measurement of cysteine (Cys), cystine (CySS), glutathione (GSH) and GSH disulfide (GSSG) by HPLC followed by estimation of redox potentials (E_h) using the Nernst equation. Results showed that patients with COPD had more oxidized plasma E_h Cys/CySS than patients with normal lung function, but plasma E_h GSH/GSSG was unaltered. In addition, there was a correlation between the extent of plasma E_h Cys/CySS oxidation and loss of lung function, and this correlation remained even after correcting for age, sex, race and body mass index. HIV infection per se was not associated with increased oxidation of plasma E_h Cys/CySS, but plasma E_h Cys/CySS was more oxidized in patients with lower CD4-positve T cell counts. In patients with both HIV infection and COPD, there was a significant correlation between CD4 cell counts and lung function. Thus, systemic oxidation correlated with decreased lung function in subjects with COPD and decreased CD4 counts in subjects infected with HIV. Thus, factors contributing to plasma E_h Cys/CySS may represent novel mechanisms underlying the increased prevalence of COPD in people living with HIV.

Immune system stimulation increases the plasma cysteine flux and whole-body glutathione synthesis rate in starter pigs1

Glutathione (GSH) is the major intracellular thiol that plays a role in numerous detoxification, bio-reduction, and conjugation reactions. The availability of Cys is thought to be the rate-limiting factor for the synthesis of GSH. The effects of immune system stimulation (ISS) on GSH levels and the GSH synthesis rate in various tissues, as well as the plasma flux of Cys, were measured in starter pigs fed a sulfur AA (SAA; Met + Cys) limiting diet. Ten feed-restricted gilts with initial body weight (BW) of 7.0 ± 0.12 kg were injected i.m. twice at 48-h intervals with either sterile saline (n = 4; ISS-) or increasing amounts of Escherichia coli lipopolysaccharide (n = 6; ISS+). The day after the second injection, pigs received a primed constant infusion of 35S-Cys (9,300 kBq/pig/h) for 5 h via a jugular catheter. Blood and tissue free Cys and reduced GSH were isolated and quantified as the monobromobimane derivatives by HPLC. The rate of GSH synthesis was determined by measurement of the specific radioactivity of GSH and tissue free Cys at the end of the infusion period. Plasma Cys and total SAA levels were reduced (16% and 21%, respectively), but plasma Cys flux was increased (26%) by ISS (P < 0.05). Immune system stimulation increased GSH levels in the plasma (48%; P < 0.05), but had no effect on GSH levels in the liver, small and large intestines, heart, muscle, spleen, kidney, lung, and erythrocytes. The fractional synthesis rate (FSR) of GSH was higher (P < 0.05) in the liver (34%), small intestine (78%), large intestine (72%), heart (129%), muscle (37%), and erythrocytes (47%) of ISS+ pigs compared to ISS- pigs. The FSR of GSH tended (P = 0.08) to be higher in the lungs (45%) of ISS+ pigs than in ISS- pigs. The absolute rate of GSH synthesis was increased by ISS (mmol/kg wet tissue/d ± SE, ISS- vs. ISS+; P < 0.05) in the liver (5.22 ± 0.22 vs. 7.20 ± 0.59), small intestine (2.54 ± 0.25 vs. 4.52 ± 0.56), large intestine (0.61 ± 0.06 vs. 1.06 ± 0.16), heart (0.21 ± 0.03 vs. 0.48 ± 0.08), lungs (1.50 ± 0.10 vs. 2.90 ± 0.21), and muscle (0.21 ± 0.03 vs. 0.34 ± 0.04), but it remained unchanged in erythrocytes, the kidney, and the spleen (P > 0.80). The current findings suggest that GSH synthesis is increased during ISS, contributing to enhanced maintenance sulfur amino acid requirements in starter pigs during ISS.

Enhancing the peroxidase-like activity of ficin by rational blocking thiol groups for colorimetric detection of biothiols

The peroxidase-like activity of ficin is relatively low, which limits its application. It was found that thiol groups of ficin could inhibit its peroxidase-like activity. So, two procedures, i.e., direct blocking with N-ethylmaleimide (NEM), or using tris (2-carboxyethyl) phosphine hydrochloride (TCEP) to interrupt disulfide bonds then blocking thiol groups with NEM, were applied to block thiol groups of ficin, ficin-NEM (ficin-N) and ficin-TCEP-NEM (ficin-TN) were produced, respectively. The blocking of thiol groups accelerated the peroxidase activity dramatically. The peroxidase catalytic activity of ficin-N and ficin-TN toward the peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB) oxidation by H₂O₂ was about 2.5-fold and 5-fold increase compared with ficin, respectively, which accompanied a color change from colorless to blue and followed classic Michaelis-Menten model. The kinetic parameters indicated that higher affinity of ficin-N (K_m = 0.31) and ficin-TN (K_m = 0.39) to H₂O₂ compared with ficin (K_m = 0.58), and ficin-TN had the highest K_cat which increased by 6.5 times and 4.5 times for TMB and H₂O₂, respectively. According to these findings, a colorimetric method with high sensitivity for the detection of biothiols was developed due to sulfhydryl compounds inhibited the peroxidase activity of ficin. Comparing with ficin and ficin-N, ficin-TN had the widest detection range (0.01-16 μM) and the lowest detection limit (3 nM). The practical applications of ficin-TN for biothiol determination in human serum samples have been demonstrated with satisfactory results. Ficin-N and ficin-TN are promising to apply to the bioanalysis.

A novel and simple imidazo[1,2-a]pyridin fluorescent probe for the sensitive and selective imaging of cysteine in living cells and zebrafish

Cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) play many crucial physiological roles in organisms. Their abnormal levels can cause and indicate various diseases. In the present study, a small-molecule fluorescent probe 2-(imidazo[1,2-a]pyridin-2-yl)phenyl acrylate (IPPA) was designed, synthesized and characterized by NMR, FT-IR and HRMS. IPPA can selectively detect Cys over other analytes because of an approximately 76 times enhancement in fluorescence intensity. The limit of detection of IPPA for Cys was 0.33 μM. The pseudo-first-order rate constant of the reaction between IPPA and Cys was approximately 10 times that of the reaction between IPPA and Hcy (KCys 3.18 × 10-3 S-1vs KHcy 4.92 × 10-4 S-1), indicating that Cys can be distinguished from Hcy. In addition, IPPA exhibits strong anti-interference ability, small molecular weight, high efficiency, low toxicity and good cell permeability. It was successfully used in imaging HepG2 cells and zebrafish. The fluorescence response of IPPA for calf serum are powerful proofs for practical application. Therefore, IPPA has high potential for bioassay applications.

A far-red FRET fluorescent probe for ratiometric detection of l-cysteine based on carbon dots and N-acetyl-l-cysteine-capped gold nanoparticles

A novel far-red fluorescence resonance energy transfer (FRET) fluorescent probe for ratiometric detection of l-cysteine (l-Cys) has been designed. The system was established a FRET assembly by positively charged carbon dots (CDs) and negatively charged N-acetyl-l-cysteine capped gold nanoparticles (NAC-AuNPs). The fluorescence of CDs at 539 nm could be effectively quenched in the presence of NAC-AuNPs owing to FRET process, while the emission of NAC-AuNPs at 630 nm was appeared. Subsequently, the interactions between l-Cys and NAC-AuNPs resulted in the decreased emission intensity of NAC-AuNPs, but the emission intensity of CDs kept almost constant due to the continuous FRET efficiency. The ratio of emission intensities at 539 and 630 nm (I₅₃₉/I₆₃₀) exhibited a linear correlation to the l-Cys concentration in the range of 1.0-110 μM with the detection limit of 0.16 μM. Moreover, this far-red ratiometric sensor also revealed excellent selectivity toward l-Cys over other amino acids, which showed very high potential in the practical application for diagnosing of cysteine-related disease.

Comparison of the Plasma Metabolome Profiles Between the Internal Thoracic Artery and Ascending Aorta in Patients Undergoing Coronary Artery Bypass Graft Surgery Using Gas Chromatography Time-of-Flight Mass Spectrometry

BACKGROUND

The left internal thoracic artery (LITA) has been used as the first conduit of choice in coronary artery bypass grafting (CABG) because of excellent long-term patency and outcomes. However, no studies have examined substances other than nitric oxide that could be beneficial for the bypass conduit, native coronary artery or ischemic myocardium. This study was conducted to evaluate differences in metabolic profiles between the LITA and ascending aorta using gas chromatography-time of flight-mass spectrometry (GC-TOF-MS).

METHODS

Twenty patients who underwent CABG using the LITA were prospectively enrolled. Plasma samples were collected simultaneously from the LITA and ascending aorta. GC-TOF-MS based untargeted metabolomic analyses were performed and a 2-step volcano plot analysis was used to identify distinguishable markers from two plasma metabolome profiles. Semi-quantitative and quantitative analyses were performed using GC-TOF-MS and enzyme-linked immunosorbent assay, respectively, after selecting target metabolites based on the metabolite set enrichment analysis.

RESULTS

Initial volcano plot analysis demonstrated 5 possible markers among 851 peaks detected. The final analysis demonstrated that the L-cysteine peak was significantly higher in the LITA than in the ascending aorta (fold change = 1.86). The concentrations of intermediate metabolites such as L-cysteine, L-methionine and L-cystine in the 'cysteine and methionine metabolism pathway' were significantly higher in the LITA than in the ascending aorta (2.0-, 1.4- and 1.2-fold, respectively). Quantitative analysis showed that the concentration of hydrogen sulfide (H₂S) was significantly higher in the LITA.

CONCLUSION

The plasma metabolome profiles of the LITA and ascending aorta were different, particularly higher plasma concentrations of L-cysteine and H₂S in the LITA.

Fluorescence red-shift of gold-silver nanoclusters upon interaction with cysteine and its application

In this work, gold-silver alloy nanoclusters (AuAg NCs) were demonstrated as a novel probe for fluorescent detection of cysteine (Cys). The alloy nanoclusters were fabricated by bovine serum albumin as a template and NaBH₄ as a reducer. They showed a red emission at 650 nm. The interaction between AuAg NCs and Cys was investigated. The thiol group in Cys molecules has strong affinity on the surface of metals, which results in variation of fluorescence peak wavelength. It was further demonstrated that this red-shift of fluorescence had a good linear relationship with the concentration of Cys in the range of 2-100 μM. The method was successfully applied for human plasma analysis with satisfactory results. This novel strategy was expected to provide a potential opportunity for extending the application of novel metal nanoclusters in fluorescence.

Combining Dietary Sulfur Amino Acid Restriction with Polyunsaturated Fatty Acid Intake in Humans: A Randomized Controlled Pilot Trial

Dietary and plasma total cysteine (tCys) have been associated with adiposity, possibly through interaction with stearoyl–CoA desaturase (SCD), which is an enzyme that is involved in fatty acid and energy metabolism. We evaluated the effect of a dietary intervention with low cysteine and methionine and high polyunsaturated fatty acids (PUFAs) on plasma and urinary sulfur amino acids and SCD activity indices. Fourteen normal-weight healthy subjects were randomized to a seven-day diet low in cysteine and methionine and high in PUFAs (Cys/Met_low + PUFA), or high in saturated fatty acids (SFA), cysteine, and methionine (Cys/Met_high + SFA). Compared with the Cys/Met_high + SFA group, plasma methionine and cystathionine decreased (p-values < 0.05), whereas cystine tended to increase (p = 0.06) in the Cys/Met_low + PUFA group. Plasma total cysteine (tCys) was not significantly different between the groups. Urinary cysteine and taurine decreased in the Cys/Met_low + PUFA group compared with the Cys/Met_high + SFA group (p-values < 0.05). Plasma SCD-activity indices were not different between the groups, but the change in cystine correlated with the SCD-16 index in the Cys/Met_low + PUFA group. A diet low in methionine and cysteine decreased plasma methionine and urinary cysteine and taurine. Plasma tCys was unchanged, suggesting that compensatory mechanisms are activated during methionine and cysteine restriction to maintain plasma tCys.

Exploring a Novel Screening Method for Patients with Oral Squamous Cell Carcinoma: A plasma Metabolomics Analysis

AIM

This study aimed to explore novel metabolite biomarker candidates for screening oral squamous cell carcinoma (OSCC).

PATIENTS & METHODS

We collected plasma samples from 48 patients with OSCC and 29 with an oral disease and conducted a plasma metabolomics analysis of patients with OSCC using gas chromatography mass spectrometry. Then, we used the cross-validation procedure to ensure the accuracy of biomarker candidates.

RESULTS

We selected four biomarker candidates against OSCC. Their sensitivity was more than 90%, and the AUC was over 0.9 according to the receiver operating characteristic curve analysis.

CONCLUSIONS

The findings of this study suggest four potential metabolites as biomarkers for OSCC screening.

Functionalized gold and persistent luminescence nanoparticle-based ratiometric absorption and TR-FRET nanoplatform for high-throughput sequential detection of l-cysteine and insulin

In vitro diagnostic is a crucial component of healthcare systems for early diagnosis of diseases and follow-up therapy, which generally makes clinical diagnosis faster, easier, and painless for patients. Herein, we report a dual-signaling nanoplatform for ratiometric absorption and time-resolved fluorescence resonance energy transfer based on l-cysteine-mediated aggregated gold nanoparticles and long afterglow nature of persistent luminescence nanoparticles. With this nanoplatform, we have achieved high-throughput sequential detection of l-cysteine and insulin in human serum without matrix interference. The proposed nanoplatform shows excellent linearity and precision for the determination of l-cysteine in the range of 10 nM to 5.5 μM with the limit of detection (LOD) of 2.2 nM and for the detection of insulin in the range of 12 pM to 3.44 nM with LOD of 2.06 pM. The developed dual-signaling nanoplatform has been successfully applied for the sequential determination of l-cysteine and insulin in human serum.

Associations of Plasma Amino Acid and Acylcarnitine Profiles with Incident Reduced Glomerular Filtration Rate

BACKGROUND AND OBJECTIVES

Metabolomics is instrumental in identifying novel biomarkers of kidney function to aid in the prevention and management of CKD. However, data linking the metabolome to incident eGFR are sparse, particularly in Asian populations with different genetic backgrounds and environmental exposures. Therefore, we aimed to investigate the associations of amino acid and acylcarnitine profiles with change in eGFR in a Chinese cohort.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study included 1765 community-living Chinese adults aged 50-70 years with baseline eGFR≥60 ml/min per 1.73 m2. At baseline, 22 amino acids and 34 acylcarnitines in plasma were quantified by gas or liquid chromatography coupled with mass spectrometry. Annual rate of change in eGFR was calculated, and incident eGFR decline was defined as eGFR<60 ml/min per 1.73 m2 by the end of 6 years of follow-up.

RESULTS

The mean (SD) unadjusted annual change in eGFR was 2.2±2.0 ml/min per 1.73 m2 and the incidence of reduced eGFR was 16%. After Bonferroni correction, 13 of 56 metabolites were significantly associated with annual eGFR change. After multivariable adjustment of baseline covariates, including baseline eGFR, seven of the 13 metabolites, including cysteine, long-chain acylcarnitines (C14:1OH, C18, C18:2, and C20:4), and other acylcarnitines (C3DC and C10), were significantly associated with incident reduced eGFR (relative risks ranged from 1.16 to 1.25 per SD increment of metabolites; P<3.8E-03 after Bonferroni correction of multiple testing of the 13 metabolites). Moreover, principal component analysis identified two factors, consisting of cysteine and long-chain acylcarnitines, respectively, that were associated with incident reduced eGFR.

CONCLUSIONS

Elevated plasma levels of cysteine and a panel of acylcarnitines were associated with a higher incidence of reduced eGFR in Chinese adults, independent of baseline eGFR and other conventional risk factors.

Increased serum levels of cysteine in patients with schizophrenia: A potential marker of cognitive function preservation

BACKGROUND

Oxidative stress has been implicated in the psychopathology of schizophrenia. Cysteine, a semi-essential amino acid, is the precursor of the antioxidant glutathione. The aim of this study was to investigate the differences in serum levels of cysteine between patients with schizophrenia and healthy controls. The relationships between levels of cysteine, psychopathology and cognitive function were also explored.

METHODS

We recruited 65 patients with schizophrenia and 65 age- and gender-matched healthy controls. Blood samples were collected to determine the serum levels of cysteine and plasma levels of metabolic parameters. The cognitive function of participants was assessed using the Brief Assessment of Cognition in Schizophrenia (BACS). The psychopathology of schizophrenic patients was evaluated using the Positive and Negative Syndrome Scale.

RESULTS

Serum cysteine levels were significantly higher in schizophrenic patients than in controls (P<0.001). In patients with schizophrenia, serum levels of cysteine were positively correlated with cognitive function in terms of verbal memory (P=0.013), working memory (P=0.004), verbal fluency (P=0.027), attention and processing speed (P=0.025), executive function (P=0.024) and the composite score on the BACS (P=0.013). In healthy controls, no significant correlation was observed between cysteine level and cognitive function.

CONCLUSIONS

These findings suggest that oxidative stress may be involved in the pathogenesis of schizophrenia, and compensatory elevated levels of cysteine may serve as an indicator of cognition preservation. Further prospective studies are warranted to investigate the dynamic alterations in cysteine and the underlying pathophysiology of schizophrenia.

Vitamin D deficiency is associated with an oxidized plasma cysteine redox potential in critically Ill children

Critically ill populations incur high levels of oxidative stress and commonly present with vitamin D deficiency. This study aimed to investigate the relationship between vitamin D status and plasma markers of glutathione (GSH) and cysteine (Cys) redox and immunity in critically ill children. This was a cross-sectional study of n=50 PICU patients. Subjects were categorized according to their plasma 25-hydroxyvitamin D [25(OH)D] concentrations: (<20, 20-30, and ≥30ng/dL). Plasma GSH, glutathione disulfide (GSSG), Cys, and cystine (CySS) were measured with high-performance liquid chromatography, and their associated redox potentials determined (E_hGSSG and E_hCySS, respectively). Plasma LL-37, an indicator of innate immune function, was assayed with ELISA. Data were analyzed using general linear regression before and after adjustment for age, sex, and race. Results showed that E_hCySS was more reduced in subjects with plasma 25(OH)D concentrations ≥30ng/mL compared to those with 25(OH)D concentrations <20ng/mL (P=0.009). Plasma GSH, GSSG, and total GSH decreased with increasing 25(OH)D category (P=0.06, 0.03, and 0.01, respectively), and plasma glutamine levels were lowest in subjects with plasma 25(OH)D concentrations ≥30ng/mL (P=0.004). Plasma LL-37 concentrations did not significantly differ by vitamin D status (P=0.08). In conclusion, vitamin D sufficiency was associated with more reduced plasma E_hCySS, indicative of lower oxidative stress in critically ill children. Plasma GSH, GSSG, and glutamine, however, were lower in the vitamin D sufficient group. The role of vitamin D in maintaining redox status during pediatric critical illness requires further study.

[Investigation of serum cysteine concentration to monitor glomerular filtration rate for early diagnosis of acute kidney injury in patients with combined trauma]

AIM

/ To determine the early diagnostic criteria for acute kidney injury in patients with combined trauma using serum cystatin C as a biomarker in the diagnostic work-up of the affected patients.

MATERIALS AND METHODS

/ The study comprised 42 patients who suffered combined trauma from 2015 to 2016. Cystatin C level was measured in serum. Blood sampling was done on the 1st, 3rd, 7th, 14th day of the injury. The patients were predominantly men (80%). Renal function was tested by measuring the rate of filtration and reabsorption using the Reberg-Tareev test. All patients were tested for the following parameters: serum and urine creatinine, 1-minute, 1-hour and 24-hour urine output, the rate of glomerular filtration and tubular reabsorption.

RESULTS AND DISCUSSION

/ Forty (95.3%) patients had normal Reberg-Tareev test values. In 2 (4.7%) patients Reberg-Tareev test results were below normal values, which was associated with the development of acute renal failure on the sixth or seventh day after trauma. The overwhelming majority of patients with combined trauma had a normal serum creatinine level (n=38). In 33 (78.6%) patients serum cystatin C level was more than 30 percent above normal values. Moreover, an increase in the cystatin C level was observed in the first 3 days, with a gradual decrease thereafter. The glomerular filtration rate, according to the Reberg-Tareev test was reduced only in 4 patients, but when the Hawk formula was used to calculate GFR, it was reduced in 33 patients. On the 3rd day after trauma, based on the increase in the serum cystatin level, 12 patients were found to have subclinical acute renal damage. At the same time, this group of patients had normal azotemia parameters. These findings suggest that measuring glomerular filtration rate using serum cystatin C has a greater accuracy in detecting latent renal dysfunction.

Analysis of the safety and efficacy of combined extracorporeal shock wave lithotripsy and percutaneous nephrolithotomy for the treatment of complex renal calculus

OBJECTIVE

To investigate the safety and efficacy of extracorporeal shock wave lithotripsy (ESWL) combined with percutaneous nephrolithotomy (PCNL) for treatment of complex renal calculus.

PATIENTS AND METHODS

Seventy-eight patients diagnosed with complex renal calculus and who accepted treatment in our hospital were consecutively selected. Patients were divided randomly into the observation group (n=40) treated by combined ESWL and PCNL and the control group (n=38) treated by PCNL. The effect of treatment between the two groups was compared.

RESULTS

The stone-free rate at 3 months after surgery was higher in the observation group than in the control group. There were no differences in the rates of complications (including infection, hemorrhage, collection system perforation and laceration, peripheral organ impairment, and urination extravasation). There were gradual decreases of serum creatinine in the observation group at 4 weeks after extubation of the double J catheter and at 3 months after surgery, while there were no apparent decreases in the control group. The levels of cysteine protease inhibitor and neutrophil gelatinase-associated lipocalin in both groups increased at 4 weeks after extubation of the double J catheter, and decreased at 3 months after surgery. The decreases were more apparent in the observation group compared with the control group, and the differences were statistically significant (p<0.05).

CONCLUSIONS

Combined use of ESWL and PCNL to treat complex renal calculus can improve the stone-free rate and renal function, and does not increase the complication rate. It is, therefore, safe and effective.

Plasma-aminothiols status and inverse correlation of total homocysteine with B-vitamins in arsenic exposed population of West Bengal, India

Chronic arsenic toxicity is a serious environmental health problem across the world. Bangladesh and India (particularly the state of West Bengal) are the worst affected countries with such problem. The present study reports plasma-aminothiols (p-aminothiols) like L-cysteine (L-Cys), cysteinyl glycine (Cys-gly), total homocysteine (t-Hcy) and glutathione (GSH) status, and the inverse relationship of t-Hcy with B-vitamins (B1, B6, B9 and B12) in arsenic exposed population of West Bengal, India. Reverse phase HPLC was used to measure p-aminothiols and serum B-vitamins in different arsenic exposed population. Arsenic in drinking water and urine were measured by flow injection analysis system - Atomic Absorption Spectrometry (FIAS-AAS) and Transversely heated graphite atomizer (THGA-AAS) techniques, respectively. Water arsenic exposure was >50 µg/L in 50% population, of which majority (33.58%) belong to the range of >50-500 µg/L and more than 8% were even >1000 µg/L. Urine arsenic (µg/g creatinine) levels increased with arsenic exposure. The variability among p-aminothiols was also observed with higher exposure to arsenic in drinking water. A significant difference between exposed and control population was noticed for plasma L-Cys. The difference of B-vitamins between the population exposed to <50 and >50 µg/L arsenic in drinking water was also found to be significant. B9 and B12 deficiency with increased consumption of arsenic in water corroborates the anemic conditions commonly observed among arsenic exposed population. The aminothiol status indicated oxidative stress in exposed population. This study demonstrated progressive increase in plasma t-Hcy as well as inverse relationships of serum B-vitamins with increased water arsenic concentration.

Spectrophotometric determination of L-cysteine by using polyvinylpyrrolidone-stabilized silver nanoparticles in the presence of barium ions

In this article a simple and selective colorimetric probe for cysteine determination using silver nano particles (AgNPS) is described. The determination process was based upon the surface plasmon resonance properties of polyvinylpyrrolidone-stabilized AgNPS. Interaction of AgNPS with cysteine molecules in the presence of barium ions induced a red shift in the surface plasmon resonance (SPR) maximum of AgNPs, as a result of nanoparticle aggregation. Consequently, yellow color of AgNP solution was changed to pink. The linear range for the determination of cysteine was 3.2-8.2 μM (R=0.9965) with a limit of detection equal to 2.8 μM (3σ). The proposed method was successfully applied to the determination of cysteine in human plasma samples. Acceptable recovery results of the spiked samples confirmed the validity of the proposed method.

A novel pyrene based fluorescent probe for selective detection of cysteine in presence of other bio-thiols in living cells

This manuscript reports the synthesis of pyrene-based fluorescent probe (PA-1) containing α,β-unsaturated carbonyl moiety and its application towards the selective and sensitive detection of cysteine (Cys) over other bio-thiols. The probe, 3-(2-hydroxyphenyl)-1-pyrenyl-2-propenone (PA-1) was synthesized through Claisen-Schmidt condensation between acetyl pyrene and salicylaldehyde. The formed product was characterized by (1)H NMR, (13)C NMR and GC-MS techniques. The probe exhibited absorption maximum at 374nm and emission maximum at 467nm (λex=342nm). The emission intensity of PA-1 was greatly enhanced while adding 2.5nM Cys. This can be attributed to the nucleophilic attack of Cys to the α,β-unsaturated ketone resulting in switching off, intramolecular charge transfer (ICT) from pyrene moiety to the phenolic nucleus. This was confirmed by DFT measurements. The PA-1 exhibited an excellent selectivity towards the determination of 40nM cys in the presence of 250,000-fold higher concentration of common interferents. The emission intensity was linearly increased and the limit of detection was found to be 10pM/L (S/N=3). Interestingly, the response of the PA-1 towards Cys is less than 1min. The confocal laser scanning micrographs of HeLa cells confirmed the cell permeability of the PA-1 and its ability to selectively detect Cys in living cells. In addition, the proposed probe was successfully applied for the determination of Cys in blood serum samples.

Novel Biomarker of Oxidative Stress Is Associated With Risk of Death in Patients With Coronary Artery Disease

BACKGROUND

Free radical scavengers have failed to improve patient outcomes, promoting the concept that clinically important oxidative stress may be mediated by alternative mechanisms. We sought to examine the association of emerging aminothiol markers of nonfree radical mediated oxidative stress with clinical outcomes.

METHODS AND RESULTS

Plasma levels of reduced (cysteine and glutathione) and oxidized (cystine and glutathione disulphide) aminothiols were quantified by high performance liquid chromatography in 1411 patients undergoing coronary angiography (mean age 63 years, male 66%). All patients were followed for a mean of 4.7 ± 2.1 years for the primary outcome of all-cause death (n=247). Levels of cystine (oxidized) and glutathione (reduced) were associated with risk of death (P<0.001 both) before and after adjustment for covariates. High cystine and low glutathione levels (>+1 SD and <-1 SD, respectively) were associated with higher mortality (adjusted hazard ratio [HR], 1.63; 95% confidence interval [CI], 1.19-2.21; HR, 2.19; 95% CI, 1.50-3.19; respectively) compared with those outside these thresholds. Furthermore, the ratio of cystine/glutathione was also significantly associated with mortality (adjusted HR, 1.92; 95% CI, 1.39-2.64) and was independent of and additive to high-sensitivity C-reactive protein level. Similar associations were found for other outcomes of cardiovascular death and combined death and myocardial infarction.

CONCLUSIONS

A high burden of oxidative stress, quantified by the plasma aminothiols, cystine, glutathione, and their ratio, is associated with mortality in patients with coronary artery disease, a finding that is independent of and additive to the inflammatory burden. Importantly, these data support the emerging role of nonfree radical biology in driving clinically important oxidative stress.

Quantification of homocysteine and cysteine by derivatization with pyridoxal 5'-phosphate and hydrophilic interaction liquid chromatography

A simple and rapid assay using pyridoxal 5'-phosphate (PLP) as a derivatizing reagent was developed for the simultaneous determination of homocysteine (Hcy) and cysteine (Cys) in human plasma. Derivatization with PLP affords UV-absorbing tetrahydrothiazine and thiazolidine derivatives of Hcy and Cys, respectively. Separation of these derivatives was achieved in 5 min using a hydrophilic interaction liquid chromatography, followed by UV detection at 330 nm. Linearity in detector response was observed over the range of 0.25-20 μM for Hcy and 10-300 μM for Cys. The limit of quantification (LOQ) values for Hcy and Cys were 0.25 and 2.5 μM, respectively. The method was successfully applied to plasma samples donated by apparently healthy volunteers.

The association of single nucleotide polymorphisms of the maternal cystathionine-β-synthase gene with early-onset preeclampsia

OBJECTIVES

Preeclampsia (PE) is a pregnancy complication, characterized by hypertension and proteinuria. The transsulfuration pathway may be involved in its pathophysiology, since homocysteine, cystathionine and cysteine are increased in PE. Cystathionine-β-synthase (CBS) is a key-enzyme in the pathway, converting homocysteine into cysteine via cystathionine. Another product of CBS is hydrogen sulfide (H2S), a vasodilatory, proangiogenic and cytoprotective gas that is thought to play a role in placental and vascular function during pregnancy. Since single nucleotide polymorphisms (SNPs) can affect CBS expression and/or function, we studied tag-SNPs in the CBS gene in PE patients.

STUDY DESIGN

Controls (n=75), early-onset (n=45), and late-onset PE (n=52) cases were genotyped for six tag-SNPs in the CBS gene; rs12329764, rs2851391, rs234713, rs234706, rs1789953, and rs11203172. Plasma homocysteine, cysteine and cystathionine were determined during pregnancy.

MAIN OUTCOME MEASURES

Early-onset PE, late-onset PE.

RESULTS

Women with the minor allele of rs11203172 have a reduced risk for early-onset PE. Compared to women without the minor allele, normotensive pregnant women with the minor allele of rs11203172 and rs234713 have lower cysteine levels. Women with the minor allele of rs1789953 have increased levels of cysteine and cystathionine, compared to women without.

CONCLUSION

The CBS tag-SNP rs11203172 is associated with a decreased risk for early-onset PE. Decreased cysteine concentrations in normotensive pregnant women carrying the minor allele of rs11203172, may be due to increased cysteine conversion to H2S by CBS. Higher H2S levels may positively affect placentation and vascular function during pregnancy and decrease their risk for PE.

Two-dimensional high performance liquid chromatography for determination of homocysteine, methionine and cysteine enantiomers in human serum

A two-dimensional HPLC system with electrochemical detection was used for determination of homocysteine, methionine and cysteine enantiomers in biological samples. The amino acid separations were not possible only by using a chiral column. The compounds were separated from each other on an achiral column (Purospher RP-18 endcapped 250-4mm, 5μm) and their enantiomers were separated on Chirobiotic TAG (250-4.6mm, 5μm) column in an on-line system. The mobile phase composition and a choice of electrode potentials for detection were investigated. The l-enantiomers always eluted before the d-enantiomers. The proposed method was applied to the analysis of human serum of healthy volunteers and patients with multiple sclerosis. The limit of detection (LOD) and quantitation (LOQ) were defined as the concentration that produced a signal-to-noise ratio (S/N) of 3 and 10. The method LOD values were found to be between 0.05 and 0.50μgmL(-1). The range of LOQ values were between 0.17 and 1.67μgmL(-1), respectively.

A Protein Extract from Chicken Reduces Plasma Homocysteine in Rats

The present study aimed to evaluate effects of a water-soluble protein fraction of chicken (CP), with a low methionine/glycine ratio, on plasma homocysteine and metabolites related to homocysteine metabolism. Male Wistar rats were fed either a control diet with 20% w/w casein as the protein source, or an experimental diet where 6, 14 or 20% w/w of the casein was replaced with the same amount of CP for four weeks. Rats fed CP had reduced plasma total homocysteine level and markedly increased levels of the choline pathway metabolites betaine, dimethylglycine, sarcosine, glycine and serine, as well as the transsulfuration pathway metabolites cystathionine and cysteine. Hepatic mRNA level of enzymes involved in homocysteine remethylation, methionine synthase and betaine-homocysteine S-methyltransferase, were unchanged, whereas cystathionine gamma-lyase of the transsulfuration pathway was increased in the CP treated rats. Plasma concentrations of vitamin B2, folate, cobalamin, and the B-6 catabolite pyridoxic acid were increased in the 20% CP-treated rats. In conclusion, the CP diet was associated with lower plasma homocysteine concentration and higher levels of serine, choline oxidation and transsulfuration metabolites compared to a casein diet. The status of related B-vitamins was also affected by CP.

Biomarkers of oxidative stress study VI. Endogenous plasma antioxidants fail as useful biomarkers of endotoxin-induced oxidative stress

This is the newest report in a series of publications aiming to identify a blood-based antioxidant biomarker that could serve as an in vivo indicator of oxidative stress. The goal of the study was to test whether acutely exposing Göttingen mini pigs to the endotoxin lipopolysaccharide (LPS) results in a loss of antioxidants from plasma. We set as a criterion that a significant effect should be measured in plasma and seen at both doses and at more than one time point. Animals were injected with two doses of LPS at 2.5 and 5 µg/kg iv. Control plasma was collected from each animal before the LPS injection. After the LPS injection, plasma samples were collected at 2, 16, 48, and 72 h. Compared with the controls at the same time point, statistically significant losses were not found for either dose at multiple time points in any of the following potential markers: ascorbic acid, tocopherols (α, δ, γ), ratios of GSH/GSSG and cysteine/cystine, mixed disulfides, and total antioxidant capacity. However, uric acid, total GSH, and total Cys were significantly increased, probably because LPS had a harmful effect on the liver. The leakage of substances from damaged cells into the plasma may have increased plasma antioxidant concentrations, making changes difficult to interpret. Although this study used a mini-pig animal model of LPS-induced oxidative stress, it confirmed our previous findings in different rat models that measurement of antioxidants in plasma is not useful for the assessment of oxidative damage in vivo.

BODIPY-based fluorometric sensor for the simultaneous determination of Cys, Hcy, and GSH in human serum

Cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) are interconnected and play essential roles for regulating the redox balance of biological processes. However, finding a simple and effective method for the simultaneous determination for these three biothiols in biological systems is always a challenge. In this work, we report a method for the simultaneous quantitative determination of three biothiols in a mixture using a monochlorinated boron dipyrromethene (BODIPY)-based fluorometric sensor. At a specified period of time, after reacting with excess sensor, Hcy and GSH form predominantly sulfur-substituted BODIPY, while Cys generates sulfur-amino-diBODIPY due to a fast substitution-rearrangement-substitution reaction. A significant difference in polarities of these respective major products simplifies their separation by TLC, thus leading to the simultaneous determination of Cys, Hcy, and GSH readily. The sensor was successfully applied for the simultaneous quantitative detection of three biothiols in human serum, and the results were in good agreement with those obtained via high performance liquid chromatography (HPLC).

[Transport of dinitrosyl iron complexes into animal lungs]

Effective accumulation of binuclear dinitrosyl iron complexes with glutathione was shown after a subcutaneous para lymphatic injection of an aqueous solution of a dinitrosyl-iron complex into animal lung tissue at a single-dose of 2 micromoles per kilogram two times a day with a 2-h interval. Two hours later after the administration was repeated the concentration of these complexes was 16 micromoles per kilogram of tissue dropping down for the last two hours to 7 micromoles per kilogram of tissue. At one dose injection of binuclear dinitrosyl iron complexes with glutathione their concentration in 2 and 4 hours was two times lower than in the previous experiments. Presumably at the obtained concentration of dinitrosyl iron complexes a bactericidal effect in lungs can be observed against mycobacterium tuberculosis and rapidly proliferating lung tumors.

Comparative analysis of the relationship between trichloroethylene metabolism and tissue-specific toxicity among inbred mouse strains: liver effects

Trichloroethylene (TCE) is a widely used organic solvent. Although TCE is classified as carcinogenic to humans, substantial gaps remain in our understanding of interindividual variability in TCE metabolism and toxicity, especially in the liver. A hypothesis was tested that amounts of oxidative metabolites of TCE in mouse liver are associated with hepatic-specific toxicity. Oral dosing with TCE was conducted in subacute (600 mg/kg/d; 5 d; 7 inbred mouse strains) and subchronic (100 or 400 mg/kg/d; 1, 2, or 4 wk; 2 inbred mouse strains) designs. The quantitative relationship was evaluated between strain-, dose-, and time-dependent formation of TCE metabolites from cytochrome P-450-mediated oxidation (trichloroacetic acid [TCA], dichloroacetic acid [DCA], and trichloroethanol) and glutathione conjugation [S-(1,2-dichlorovinyl)-L-cysteine and S-(1,2-dichlorovinyl)glutathione] in serum and liver, and various hepatic toxicity phenotypes. In subacute study, interstrain variability in TCE metabolite amounts was observed in serum and liver. No marked induction of Cyp2e1 protein levels in liver was detected. Serum and hepatic levels of TCA and DCA were correlated with increased transcription of peroxisome proliferator-marker genes Cyp4a10 and Acox1 but not with degree of induction in hepatocellular proliferation. In subchronic study, serum and liver levels of oxidative metabolites gradually decreased over time despite continuous dosing. Hepatic protein levels of CYP2E1, ADH, and ALDH2 were unaffected by treatment with TCE. While the magnitude of induction of peroxisome proliferator-marker genes also declined, hepatocellular proliferation increased. This study offers a unique opportunity to provide a scientific data-driven rationale for some of the major assumptions in human health assessment of TCE.

Plasma levels of homocysteine and cysteine increased in pediatric NAFLD and strongly correlated with severity of liver damage

Non-alcoholic fatty liver disease (NAFLD) is a spectrum of metabolic abnormalities ranging from simple triglyceride accumulation in the hepatocytes to hepatic steatosis with inflammation, ballooning and fibrosis. It has been demonstrated that the pathogenesis of NAFLD involves increased oxidative stress, with consumption of the major cellular antioxidant, glutathione (GSH). Liver has a fundamental role in sulfur compound metabolism, although the data reported on plasma thiols status in NAFLD are conflicting. We recruited 63 NAFLD patients, and we analyzed all plasma thiols, such as homocysteine (Hcy), cysteine (Cys), cysteinylglycine (CysGly) and GSH, by high-performance liquid chromatography (HPLC) with fluorescence detection. Hcy, Cys and CysGly plasma levels increased in NAFLD patients (p < 0.0001); whereas GSH levels were decreased in NAFLD patients when compared to controls (p < 0.0001). On the contrary, patients with steatohepatitis exhibited lower levels of Hcy and Cys than subjects without. Furthermore, a positive correlation was found between Hcy and Cys and the presence of fibrosis in children with NAFLD. Taken together, these data demonstrated a defective hepatic sulfur metabolism in children with NAFLD, and that high levels of Hcy and Cys probably correlates with a pattern of more severe histological liver damage, due to mechanisms that require further studies.

Skeletal muscle wasting occurs in adult rats under chronic treatment with paracetamol when glutathione-dependent detoxification is highly activated

The use of glutathione (GSH) and sulfate for the detoxification of paracetamol (acetaminophen, APAP) could occur at the expense of the physiological uses of cysteine (Cys). Indeed GSH and sulfate both originate from Cys. Significant APAP-induced Cys loss could generate alterations in GSH and protein metabolisms leading to muscle wasting. The study aimed to investigate the effects of chronic treatment with APAP on whole-body and tissue homeostasis (mass, GSH, proteins, and nitrogen balance) in relation to sulfur losses through APAP-detoxification pathways. Adult male Wistar rats were fed 0% APAP, 0.5% APAP or 1% APAP diets for 17 days. APAP doses were respectively around and largely above the threshold of sulfation saturation for rats. During the last days, the rats were placed in metabolic cages in order to quantify N balance and urinary APAP metabolites. Gastrocnemius muscle mass, protein and GSH contents, N balance and plasma free cyst(e)ine were 8% (P=0.02), 7% (P=0.03), 26% (P=0.01), 37% (P=0.01), and 33% (P=0.003) lower in the 1% APAP group than in the 0% APAP group, respectively. There was no significant difference in these parameters between the 0.5% APAP group and the 0% APAP group. Muscle wasting occurred when the detoxification of APAP through the GSH-dependent pathway was highly activated. Muscle protein synthesis could have been reduced due to a shortage in Cys and/or an increase in protein degradation in response to intra-muscular oxidative stress. Hence, without dietary sulphur amino acid increase, peripheral bioavailability of Cys and muscle GSH are potential players in the control of muscle mass under chronic treatment with APAP, an analgesic medication of widespread use, especially in the elderly.

"Red-to-blue" colorimetric detection of cysteine via anti-etching of silver nanoprisms

The reported strategies for cysteine (Cys) colorimetric detection based on noble metal nanomaterials include triggering aggregation, etching or fluorescence quenching of nanomaterials by Cys. In this study, we propose a new strategy for Cys colorimetric detection, i.e. anti-etching of silver nanoprisms (AgNPRs). In the absence of Cys, iodide ions (I(-)) could etch the corners and edges of AgNPRs and induce the morphology transition from nanoprism to nanodisk, which results in color change of the AgNPR dispersion from blue to red. In its presence, however, Cys can prevent the AgNPRs from I(-) attack. In that case, the color of the AgNPR dispersion containing I(-) and Cys remains blue. The mechanism is confirmed by using UV-vis spectra, TEM, DLS, Raman spectra and XPS spectra. According to the sensing effect of the Cys detection system, the concentration of I(-) incubated with AgNPRs, incubation time of AgNPRs and I(-), and pH of AgNPR dispersions are optimized to 5.0 μM, 10 min, and pH 6.2, respectively. Under the optimized conditions, the proposed Cys detection system has excellent selectivity and high sensitivity. The limit of detection (LOD) of our Cys detection system is 25 nM by the naked eye, which is much better than the reported lowest LOD by eye-vision (100 nM), and 10 nM by UV-vis spectroscopy. The results of Cys detection in rabbit urine or plasma samples reinforce that our Cys detection system is applicable for rapid colorimetric detection of Cys in real body fluid samples.

Vitamin D status is independently associated with plasma glutathione and cysteine thiol/disulphide redox status in adults

OBJECTIVE

Redox status and inflammation are important in the pathophysiology of numerous chronic diseases. Epidemiological studies have linked vitamin D status to a number of chronic diseases. We aimed to examine the relationships between serum 25-hydroxyvitamin D [25(OH)D] and circulating thiol/disulphide redox status and biomarkers of inflammation.

DESIGN

This was a cross-sectional study of N = 693 adults (449 females, 244 males) in an apparently healthy, working cohort in Atlanta, GA. Plasma glutathione (GSH), cysteine (Cys) and their associated disulphides were determined with high-performance liquid chromatography, and their redox potentials (Eh GSSG and Eh CySS) were calculated using the Nernst equation. Serum inflammatory markers included interleukin-6 (IL-6), interleukin-8 (IL-8) and tumour necrosis factor-α, assayed on a multiplex platform, and C-reactive protein (CRP), assayed commercially. Relationships were assessed with multiple linear regression analyses.

RESULTS

Serum 25(OH)D was positively associated with plasma GSH (β ± SE: 0·002 ± 0·0004) and negatively associated with plasma Eh GSSG (β ± SE: -0·06 ± 0·01) and Cys (β ± SE: -0·01 ± 0·003) (P < 0·001 for all); statistical significance remained after adjusting for age, gender, race, percentage body fat and traditional cardiovascular risk factors (P = 0·01-0·02). The inverse relationship between serum 25(OH)D and CRP was confounded by percentage body fat, and full adjustment for covariates attenuated serum 25(OH)D relationships with other inflammatory markers to nonstatistical significance.

CONCLUSIONS

Serum 25(OH)D concentrations were independently associated with major plasma thiol/disulphide redox systems, suggesting that vitamin D status may be involved in redox-mediated pathophysiology.

Homocysteine, cysteine, folate and vitamin B₁₂ status in type 2 diabetic patients with chronic kidney disease

BACKGROUND

Hyperhomocysteinemia (hHcy) is a risk factor in the progression of chronic kidney disease (CKD). In type 2 diabetes (T2D), hHcy is strongly associated with increased risk of cardiovascular disease. Vitamin B12 and folic acid supplementation have been reported to lower homocysteine (tHcy) levels, but no data on plasma tHcy, cysteine (Cys), folate and vitamin B12 levels in T2D-CKD patients are reported.

PROCEDURES

tHcy and Cys levels were analyzed in 178 T2D-CKD patients by high performance liquid chromatography (HPLC) with fluorescence detection. In addition, we determined folate and vitamin B12 levels using a chemiluminescence method.

RESULTS

tHcy and Cys levels were increased in T2D patients, and this rise positively correlated with the CKD stage (P < 0.001). Folate levels were comparable to controls at various CKD stages, whereas vitamin B12 levels were lower, except at stage IV. We did not find any correlation between B-vitamins and levels of tHcy and Cys, regardless of the CKD stage.

CONCLUSIONS

This is the first study reporting tHcy, Cys and B-vitamins status in T2D-CKD patients. Although limited to our cohort of 178 patients, our findings could be helpful in clarifying the conflicting literature regarding B-vitamins supplementation. Further studies are necessary before any Hcy-lowering therapy can be safely established in T2D-CKD subjects.

Hydrogen sulfide and nitric oxide metabolites in the blood of free-ranging brown bears and their potential roles in hibernation

During winter hibernation, brown bears (Ursus arctos) lie in dens for half a year without eating while their basal metabolism is largely suppressed. To understand the underlying mechanisms of metabolic depression in hibernation, we measured type and content of blood metabolites of two ubiquitous inhibitors of mitochondrial respiration, hydrogen sulfide (H2S) and nitric oxide (NO), in winter-hibernating and summer-active free-ranging Scandinavian brown bears. We found that levels of sulfide metabolites were overall similar in summer-active and hibernating bears but their composition in the plasma differed significantly, with a decrease in bound sulfane sulfur in hibernation. High levels of unbound free sulfide correlated with high levels of cysteine (Cys) and with low levels of bound sulfane sulfur, indicating that during hibernation H2S, in addition to being formed enzymatically from the substrate Cys, may also be regenerated from its oxidation products, including thiosulfate and polysulfides. In the absence of any dietary intake, this shift in the mode of H2S synthesis would help preserve free Cys for synthesis of glutathione (GSH), a major antioxidant found at high levels in the red blood cells of hibernating bears. In contrast, circulating nitrite and erythrocytic S-nitrosation of glyceraldehyde-3-phosphate dehydrogenase, taken as markers of NO metabolism, did not change appreciably. Our findings reveal that remodeling of H2S metabolism and enhanced intracellular GSH levels are hallmarks of the aerobic metabolic suppression of hibernating bears.

Plasma homocysteine concentrations in novel microminipigs

A novel microminipig has been recently developed for use in biomedical research. In the present study, age- and sex-related differences, as well as 24-h fluctuations in plasma total homocysteine concentrations (tHcy), were investigated in these microminipigs. tHcy (mean±SD) was 10.2±3.4 μM and significantly correlated with age. By contrast, neither the differences in tHcy between sexes nor the 24-h fluctuations in tHcy after feeding were significant. The kinetics of plasma tHcy after intravenous injection of reduced Hcy showed that its levels peaked within 5 min post-injection, as did the levels of tHcy. These results suggested that reduced Hcy is rapidly oxidized or metabolized. The half-lives of reduced Hcy, tHcy, and reduced cysteine in the blood were 47, 71, and 141 min, respectively. In conclusion, there was a significantly positive correlation between age and plasma tHcy in microminipigs. After intravenous injection of reduced Hcy, plasma tHcy quickly returned to pre-injection levels.

Simultaneous determination of glutathione, cysteine, homocysteine, and cysteinylglycine in biological fluids by ion-pairing high-performance liquid chromatography coupled with precolumn derivatization

Biologically active low-molecular-mass thiols, mainly including glutathione (GSH), cysteine (Cys), homocysteine (Hcy), and cysteinylglycine (Cys-Gly), are important physiological components in biological fluids, and their analytical methods have gained continuous attention over recent years. We developed and validated a novel HPLC method for the quantification of GSH, Cys, Hcy, and Cys-Gly in human plasma, urine, and saliva using 4-chloro-3,5-dinitrobenzotrifluoride as the derivatization reagent. Analyses were linear from 0.15 to 500 μM with the coefficient regression range of 0.9987-0.9994. Detection limits ranged from 0.04 to 0.08 μM (S/N=3). The developed method was applied to quantification of four thiols in human biological fluids collected from five donors with the concentration range of 2.50-124.25 μM, 0-72.81 μM, and 0-4.25 μM for plasma, urine, and saliva, respectively. The present method seemed to be an attractive choice for the determination of thiols in plasma, urine, and saliva.

Assessment of plasma aminothiol levels and the association with recurrent atherothrombotic events in patients hospitalized for an acute coronary syndrome: a prospective study

BACKGROUND

The aminothiols homocysteine and, to a lesser extent, cysteine have been associated with adverse cardiovascular outcome, whereas glutathione, as an antioxidant, may protect against atherosclerosis and thrombosis. Potentially, the combined assessment of these aminothiols may provide a more accurate association with future cardiovascular outcome. We evaluated the association between recurrent atherothrombotic events and the concentration of total plasma cysteine, homocysteine, and glutathione and their combination.

METHODS

Respective aminothiols were measured by high-performance liquid chromatography in blood plasma of consecutive first-day survivors admitted for an acute coronary syndrome between April 2002 and January 2004. The combined score was calculated using the combination of the individual aminothiols. The end point was the composite of cardiovascular death, myocardial infarction, and/or stroke.

RESULTS

A cohort of 375 consecutive patients (median age 66 years, 66% male) were followed for a median duration of 2.7 years. The end point occurred in 82 patients (22%). In univariate analyses, all aminothiols were significantly associated with the composite end point. After correction for possible confounders, only cysteine and glutathione remained significantly associated. The strongest association with the end point was observed for the combined score (adjusted hazard ratio, 1.40 per standard deviation increase; p=0.005).

CONCLUSIONS

Although homocysteine is generally considered the aminothiol of interest with respect to cardiovascular disease, in our prospective study, only cysteine and glutathione appeared independently associated with recurrent atherothrombotic events. Moreover, we showed that an imbalance in the combination of aminothiols could be of more importance than investigating the individual metabolites.

Manganese-based superoxide dismutase mimics modify both acute and long-term outcome severity in a Drosophila melanogaster model of classic galactosemia

AIMS

The goal of this study was to use two manganese (Mn)-based superoxide dismutase (SOD) mimics to test the hypothesis that reactive oxygen species contribute to both acute and long-term outcomes in a galactose-1P uridylyltransferase (GALT)-null Drosophila melanogaster model of classic galactosemia.

RESULTS

We tested the impact of each of two Mn porphyrin SOD mimics, MnTnBuOE-2-PyP(5+), and MnTE-2-PyP(5+), (i) on survival of GALT-null Drosophila larvae reared in the presence versus absence of dietary galactose and (ii) on the severity of a long-term movement defect in GALT-null adult flies. Both SOD mimics conferred a significant survival benefit to GALT-null larvae exposed to galactose but not to controls or to GALT-null larvae reared in the absence of galactose. One mimic, MnTE-2-PyP(5+), also largely rescued a galactose-independent long-term movement defect otherwise seen in adult GALT-null flies. The survival benefit of both SOD mimics occurred despite continued accumulation of elevated galactose-1P in the treated animals, and studies of thiolated proteins demonstrated that in both the presence and absence of dietary galactose MnTE-2-PyP(5+) largely prevented the elevated protein oxidative damage otherwise seen in GALT-null animals relative to controls.

INNOVATION AND CONCLUSIONS

Our results confirm oxidative stress as a mediator of acute galactose sensitivity in GALT-null Drosophila larvae and demonstrate for the first time that oxidative stress may also contribute to galactose-independent adult outcomes in GALT deficiency. Finally, our results demonstrate for the first time that both MnTnBuOE-2-PyP(5+) and MnTE-2-PyP(5+) are bioavailable and effective when administered through an oral route in a D. melanogaster model of classic galactosemia.

Effects of randomized supplementation of methionine or alanine on cysteine and glutathione production during the early phase of treatment of children with edematous malnutrition

BACKGROUND

We have shown that a low glutathione concentration and synthesis rate in erythrocytes are associated with a shortage of protein-derived cysteine in children with edematous severe acute malnutrition (SAM).

OBJECTIVE

We tested the hypothesis that methionine supplementation may increase protein-derived cysteine and upregulate cysteine synthesis, thereby improving glutathione synthesis during the early treatment of edematous SAM.

DESIGN

The cysteine flux, its de novo synthesis and release from protein breakdown, and erythrocyte glutathione synthesis rate were measured in 12 children with edematous SAM in the fed state by using stable isotope tracers at 3 clinical phases as follows: 3 ± 1 d (±SE) [clinical phase 1 (CP1)], 8 ± 1 d [clinical phase 2 (CP2)], and 14 ± 2 d (clinical phase 3) after admission. Subjects were randomly assigned to receive equimolar supplements (0.5 mmol ⋅ kg(-1) ⋅ d(-1)) of methionine or alanine (control) immediately after CP1.

RESULTS

In the methionine compared with the alanine group, cysteine flux derived from protein breakdown was faster at CP2 than CP1 (P < 0.05), and the change in plasma cysteine concentration from CP1 to CP2 was greater (P < 0.05). However, there was no evidence of a difference in cysteine de novo synthesis and its total flux or erythrocyte glutathione synthesis rate and concentration between groups.

CONCLUSIONS

Methionine supplementation increased cysteine flux from body protein but had no significant effect on glutathione synthesis rates. Although cysteine is made from methionine, increased dietary cysteine may be necessary to partially fulfill its demand in edematous SAM because glutathione synthesis rates and concentrations were less than previous values shown at full recovery. This study was registered at clinicaltrials.gov as NCT00473031.

In vitro study of thimerosal reactions in human whole blood and plasma surrogate samples

Because of its bactericidal and fungicidal properties, thimerosal is used as a preservative in drugs and vaccines and is thus deliberately injected into the human body. In aqueous environment, it decomposes into thiosalicylic acid and the ethylmercury cation. This organomercury fragment is a potent neurotoxin and is suspected to have similar toxicity and bioavailability like the methylmercury cation. In this work, human whole blood and physiological simulation solutions were incubated with thimerosal to investigate its behaviour and binding partners in the blood stream. Inductively coupled plasma with optical emission spectrometry (ICP-OES) was used for total mercury determination in different blood fractions, while liquid chromatography (LC) coupled to electrospray ionisation time-of-flight (ESI-TOF) and inductively coupled plasma-mass spectrometry (ICP-MS) provided information on the individual mercury species in plasma surrogate samples. Analogous behaviour of methylmercury and ethylmercury species in human blood was shown and an ethylmercury-glutathione adduct was identified.

Determination of cysteine and glutathione based on the inhibition of the dinuclear Cu(II)-catalyzed luminol-H2O2 chemiluminescence reaction

The catalyzed luminol chemiluminescent reaction has received a great amount of attention because of its high sensitivity and low background signal which make the reaction an attractive analytical chemistry tool. The present study, introduces the beneficial catalytic effects of dinuclear Cu(II) complex [Cu2L2(TAE)]X2, where TAE=tetraacetylethane; L=N,N(')-dibenzylethylenediamine and X=ClO4 on the luminol chemiluminescent reaction as a novel probe for the determination of glutathione (GSH) and L-cysteine (CySH) in human serum and urine. The [Cu2L2(TAE)]X2 has exhibited highly efficient catalytic activity of luminol CL as an artificial peroxidase model at pH as low as 7.5 in water in the presence of H2O2⋅GSH and CySH can induce a sharp decrease in CL intensity from the [Cu2L2(TAE)]X2-catalyzed luminol system. Under the selected experimental conditions, a linear relationship was obtained between the CL intensity and the concentrations of GSH and CySH in the range of 1.0×10(-7)-1.0×10(-4) M, with detection limits (S/N=3) of 2.7×10(-8) and 6.8×10(-8) M and RSD<4.2% (n=7) for GSH and CySH, respectively.