Plasma kynurenic acid concentration in patients undergoing cardiac surgery: effect of anaesthesia

NAD+ Biosynthesis Impairment and Acute Kidney Injury after Major Vascular Surgery

Acute kidney injury (AKI) is a serious complication after vascular surgery. Reduced synthesis of nicotinamide adenine dinucleotide (NAD+) from tryptophan is associated with an increased risk of AKI in critically ill patients, patients hospitalized with COVID-19, and cardiac surgery patients, and is marked by elevated urinary quinolinate and quinolinate to tryptophan ratios. We measured quinolinate concentrations in vascular surgery patients to determine if impaired NAD+ synthesis was associated with AKI in this patient population. Eight preoperative and eight postoperative vascular surgery patients who developed AKI were selected from a parent study to participate in this single-center case-control study. They were matched with controls who did not develop AKI based on age, sex, BMI, eGFR, hypertension, and diabetes. Urinary quinolinate and tryptophan concentrations were measured at anesthetic induction and on postoperative day one. Two-sided Mann-Whitney U tests were used to compare quinolinate and quinolinate to tryptophan ratios. Multivariate linear regression modeling was used to estimate the relationship between quinolinate and serum creatinine. There was no difference in preoperative or postoperative urine quinolinate concentrations or the preoperative quinolinate to tryptophan ratio between patients that did and did not develop AKI (p = 0.07, 0.50, and 0.32, respectively). However, postoperative quinolinate to tryptophan ratios were higher in AKI patients (p = 0.04). Further, after adjustment for AKI risk factors, higher preoperative quinolinate concentrations and higher postoperative quinolinate to tryptophan ratios were associated with greater postoperative creatinine increases (p = 0.04 and 0.04, respectively). These data suggest that impaired NAD+ synthesis may contribute to AKI development in vascular surgery patients.

Measuring the Systemic Inflammatory Response to On- and Off-Pump Coronary Artery Bypass Graft (CABG) Surgeries Using the Tryptophan/Kynurenine Pathway

Background: Cardiac surgeries induce many inflammatory responses with remarkable clinical implications. Tryptophan (Trp) is a precursor for serotonin, melatonin and kynurenine (Kyn). Plasma kynurenic acid (Kyna) and Kyn concentrations are thought to be related to the severity of inflammation. Plasma Trp/Kyn ratio is used to measure inflammatory cytokine activity.Methods: We performed the current longitudinal study in a tertiary care center and included 62 patients divided into two groups; group A (on-pump CABG patients) and group B (off-pump CABG patients). Plasma Trp and Kyn were measured using the high-performance liquid chromatography (HPLC) technique. Serum interlukin-6 (IL-6) and white blood cells (WBCs) were measured using ELISA and routine blood count, respectively.Results: The present study revealed that the intraoperative levels of plasma Kyn, IL-6 and WBCs were significantly increased while the plasma Trp/Kyn ratio was significantly decreased in both the groups; however, the changes were more significant in the on-pump CABG group. Moreover, the levels in both the groups returned to preoperative levels 72 h postoperative. Our study has shown that WBCs is positively correlated with IL-6, but has negative correlation with Trp/Kyn ratio.Conclusions: Kyn and Trp/Kyn ratio might be utilized as markers of the severity of inflammation in major surgery. In addition, off-pump CABG might be more preferable than on-pump CABG regarding stress and release of inflammatory markers.

Fast determination of 16 circulating neurotransmitters and their metabolites in plasma samples of spontaneously hypertensive rats intervened with five different Uncaria

This study aimed to establish a sensitive, reproducible, and rapid liquid chromatography method with tandem mass spectrometry detection to perform simultaneous quantitative analysis of 16 neurotransmitters and their metabolites in rat plasma, including levodopa, dopamine, norepinephrine, epinephrine, L-tryptophan, kynurenic acid, serotonin, melatonin, choline, acetylcholine, histamine, phenylethylamine, as well as excitatory (L-glutamic acid and L-aspartic acid) and inhibitory (γ-aminobutyric acid and L-glycine) neurotransmitters. These analytes were measured by ultra-high performance chromatography coupled with triple quadrupole mass spectrometry using a hydrophilic interaction chromatographic column (ethylene-bridged hybrid amide column). The internal standards of stable isotope labeling were used to improve the reliability of the results. Our method provided high linearity for all neurotransmitters (for all coefficients measured > 0.99), with inter- and intra-day accuracy from -14.82% to 17.49% and precision was between 0.89% and 17.70%. The method was subsequently verified in an animal study, where the intervention of five different Uncarias, the traditional Chinese medicine with hypotensive effects, was applied to the spontaneously hypertensive rats (SHRs). SHRs showed dysregulated plasma kynurenic acid, acetylcholine, and norepinephrine levels, and these neuroactive analytes were significantly restored by Uncaria treatment compared with the model group (SHR group). Compared with captopril, included as a positive control for its hypotensive effect, Uncaria had more effects on perturbing the levels of plasma neurotransmitters, which might indicate Uncaria's potential in treating symptoms related to the nervous system. These results suggested that the changes in the neurotransmitters and their metabolites in plasma may be related to the pathogenesis of hypertension. It also provided valuable information about the action mechanisms of Uncaria on its hypotensive effects.

Respiratory Syncytial Virus Infection Reduces Kynurenic Acid Production and Reverses Th17/Treg Balance by Modulating Indoleamine 2,3-Dioxygenase (IDO) Molecules in Plasmacytoid Dendritic Cells

Background

Respiratory syncytial virus (RSV) infection causes a world-wide medical and economic burden. This study analyzed the effects of RSV infection on plasmacytoid dendritic cells (pDCs) and evaluated the immunopathogenesis of RSV infection by measuring relative numbers of FoxP3+ Treg cells and Th17 cells.

Material/Methods

pDCs were isolated from human blood samples, purified using magnetic microbeads, and treated with RSV, IFN-γ, or vehicle. These cells were mixed with purified CD4+ T cells to yield preparations of pDCs+T cells+vehicle, pDCs+T cells+RSV, and pDCs+T cells+IFN-γ. Preparations of pDCs+T cells+RSV were also incubated with an inducer or an inhibitor of indoleamine 2,3-dioxygenase (IDO). Kynurenic acid concentration was measured by high-pressure liquid chromatography (HPLC). The differentiation of Foxp3+ Treg and Th17 cells from CD4+ T cells was determined by flow cytometry.

Results

pDCs were successfully isolated and purified using the magnetic microbeads. Compared with preparations of pDCs+T cells+vehicle, RSV infection (pDCs+T cells+RSV) significantly reduced and IFN-γ treatment (pDC+T cells+IFN-γ) increased kynurenic acid concentrations and the proportions of Foxp3⁺ Tregs (p<0.05 each). Conversely, RSV infection increased and IFN-γ treatment decreased the proportions of Th17 cells (p<0.05 each). RSV infection reduced kynurenic acid concentrations and inhibited the transformation from Th17 to Foxp3⁺ Tregs by modulating IDO molecules.

Conclusions

RSV infection reduced the production of kynurenic acid and inhibited transformation from Th17 to Foxp3⁺ Tregs (Th17/Treg balance) by modulating IDO molecules in pDCs.

Negative effects on newborn piglets caused by excess dietary tryptophan in the morning in sows

BACKGROUND

This study investigated the effect of dynamic feeding models of dietary tryptophan on sows' performance during late pregnancy.

RESULTS

The average piglet birth weight and live farrowing rate from sows consuming a high-low tryptophan diet (0.39% Trp in the morning and 0.13% Trp in the afternoon) were decreased compared with those fed a 2×tryptophan diet (0.26% Trp in the morning and afternoon). Compared with the 2×tryptophan group, sow serum kynurenic acid and the newborn liver n-6:n-3 polyunsaturated fatty acid ratio were significantly higher, and sow serum taurine and newborn serum taurine, phosphoserine, cysteine and proline were lower in the high-low tryptophan diet group. Eighty-eight genes were differentially expressed in newborn piglets' livers between the 2×tryptophan and high-low groups. Genes related to cytotoxic effector regulation (major histocompatibility complex class I proteins), NADH oxidation, reactive oxygen species (ROS) metabolism and tissue development were differentially expressed between these two groups.

CONCLUSION

Together, the results provide information on new biomarkers in serum or liver and provide novel insights into variations in the fetal liver during exogenous stimulus response and biological processes of ROS metabolism in fetuses during late pregnancy caused by a single excessive tryptophan ingestion daily in the morning. © 2018 Society of Chemical Industry.

Metabolomic Fingerprinting of Infants Undergoing Cardiopulmonary Bypass: Changes in Metabolic Pathways and Association With Mortality and Cardiac Intensive Care Unit Length of Stay

Background Mortality for infants undergoing complex cardiac surgery is >10% with a 30% to 40% risk of complications. Early identification and treatment of high-risk infants remains challenging. Metabolites are small molecules that determine the minute-to-minute cellular phenotype, making them ideal biomarkers for postsurgical monitoring and potential targets for intervention. Methods and Results We measured 165 serum metabolites by tandem mass spectroscopy in infants ≤120 days old undergoing cardiopulmonary bypass. Samples were collected prebypass, during rewarming, and 24 hours after surgery. Partial least squares-discriminant analysis, pathway analysis, and receiver operator characteristic curve analysis were used to evaluate changes in the metabolome, assess altered metabolic pathways, and discriminate between survivors/nonsurvivors as well as upper/lower 50% intensive care unit length of stay. Eighty-two infants had preoperative samples for analysis; 57 also had rewarming and 24-hour samples. Preoperation, the metabolic fingerprint of neonates differed from older infants ( R2=0.89, Q2=0.77; P<0.001). Cardiopulmonary bypass resulted in progressive, age-independent metabolic disturbance ( R2=0.92, Q2=0.83; P<0.001). Multiple pathways demonstrated changes, with arginine/proline ( P=1.2×10-35), glutathione ( P=3.3×10-39), and alanine/aspartate/glutamate ( P=1.4×10-26) metabolism most affected. Six subjects died. Nonsurvivors demonstrated altered aspartate ( P=0.007) and nicotinate/nicotinamide metabolism ( P=0.005). The combination of 24-hour aspartate and methylnicotinamide identified nonsurvivors versus survivors (area under the curve, 0.86; P<0.01), as well as upper/lower 50% intensive care unit length of stay (area under the curve, 0.89; P<0.01). Conclusions The preoperative metabolic fingerprint of neonates differed from older infants. Large metabolic shifts occurred after cardiopulmonary bypass, independent of age. Nonsurvivors and subjects requiring longer intensive care unit length of stay showed distinct changes in metabolism. Specific metabolites, including aspartate and methylnicotinamide, may differentiate sicker patients from those experiencing a more benign course.

Effects of Sevoflurane Inhalation During Cardiopulmonary Bypass on Pediatric Patients: A Randomized Controlled Clinical Trial

The effects of sevoflurane inhalation during cardiopulmonary bypass (CPB) on postoperative courses and serum cardiac troponin I (cTnI) concentrations in pediatric patients undergoing cardiac surgery have not been extensively investigated. In this single-center, prospective, randomized trial, an anesthetic regimen containing 2% sevoflurane used throughout the CPB process was compared with a total intravenous anesthesia (TIVA) regimen. One hundred and three patients undergoing congenital heart defect repair with CPB were included in this prospective randomized controlled study. They were randomized into two groups: the sevoflurane group, who received 2% sevoflurane during CPB via an oxygenator, and the control group, who received only an oxygen-air mixture. The pre- and intra-operative parameters were comparable between the two groups. There was a slight but significant increase of arterial diastolic pressure in the sevoflurane group immediately after CPB compared with control patients (46.9 ± 9.3 mm Hg vs. 43.6 ± 8.9 mm Hg; p = 0.033). There was no death in either group. The postoperative ventilation time (in mean [95% confidence interval]) was shorter in the sevoflurane group than that in the control group (26.1 [19.2, 33.0] h vs. 37.7 [24.4, 50.9] h; p = 0.014). The postoperative ICU time, hospital days, and serial serum cTnI concentrations were not significantly different between the two groups. Inhalation of 2% sevoflurane during CPB is beneficial to the recovery of pediatric patients undergoing cardiac surgery but has no significant effect on postoperative cTnI release.