Altered neopterin and IDO in kynurenine metabolism based on LC-MS/MS metabolomics study: Novel therapeutic checkpoints for type 2 diabetes mellitus.

This study assessed the alternations of kynurenine pathway (KP) and neopterin in type 2 diabetes mellitus (T2DM) and explored possible differential metabolites. A fresh residual sera panel was collected from 80 healthy control (HC) individuals and 72 T2DM patients. Metabolites/ratios of interest including tryptophan (TRP), kynurenine (KYN), 5-hydroxytryptamine (5HT), kynurenic acid (KA), xanthurenic acid (XA), neopterin (NEO), KA/KYN ratio and KYN/TRP ratio were determined using a targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) metabolomics approach, and the difference between groups was assessed. Supervised orthogonal partial least squares-discriminant analysis and differential metabolite screening with fold change (FC) were performed to identify distinct biomarkers. The diagnostic performance of KP metabolites in T2DM was evaluated. Significant decreases of TRP, 5HT, KA, XA, and KA/KYN and increases of KYN/TRP and NEO in T2DM compared to HC group were observed (P < 0.05). The KP metabolites panel significantly changed between T2DM and HC groups (Q2: 0.925, P < 0.005). 5HT (FC: 0.63, P < 0.01) and NEO (FC: 3.27, P < 0.01) were proven to be distinct differential metabolites. A combined testing of fasting plasma glucose and KYN/TRP showed good value in the prediction of T2DM (AUC: 0.904, 95% CI 0.843-0.947). The targeted LC-MS/MS metabolomics study is a powerful tool for evaluating the status of T2DM. This study facilitated the application of KP metabolomics into future clinical practice. 5HT and NEO are promising biomarkers in T2DM. KYN/TRP was highly associated with the development of T2DM and may serve as a potential treatment target.

Liu Z ，Ma Z ，Jin L ，Nizhamuding X ，Zeng J ，Zhang T ，Zhang J ，Wang J ，Zhao H ，Zhou W ，Zhang C ... -  《-》

Abnormal kynurenine-pathway metabolites in gout: Biomarkers exploration based on orthogonal partial least squares-discriminant analysis.

This study aims to investigate serological characteristics of kynurenine pathway (KP) metabolites in healthy controls (HC) and gout patients and explore possible differential metabolites. A total of 191 individual fresh residual sera was collected from 129 HC and 62 gout patients. A liquid chromatography-tandem mass spectrometry method was fully validated to measure 6 metabolites, including tryptophan (TRP), kynurenine (KYN), 5-hydroxytryptamine (5HT), kynurenic acid (KA), xanthurenic acid (XA), and neopterin (NEO). Supervised orthogonal partial least squares-discriminant analysis (OPLS-DA) and differential metabolite screening with fold change (FC) were performed to identify intrinsic variations and differential levels of KP metabolites between the HC and gout groups. Logistic regression was used to assess the contributions of KP metabolites to gout. There were significant decreases of TRP, 5HT, XA, and NEO and increases of KYN, KA, KA/KYN, and KYN/TRP in gout patients compared to the HC group (all p < 0.05). KP metabolites of the gout group showed good discrimination from those of the HC group (Q2: 0.892). Two distinct different metabolites were identified in gout, i.e., XA (FC: 0.56, p < 0.01) and NEO (FC: 0.34, p < 0.01). Of the KP metabolites, KYN was strongly associated with gout (OR: 7.91, p < 0.01). Abnormal levels of serum KP metabolites were observed in gout. XA and NEO are promising biomarkers that were relevant to the status of gout. The level of KYN could be an attractive checkpoint for the management of gout. Continuous monitoring of KP metabolism in gout provides new opportunities to predict therapeutic efficacy and prognosis.

Liu Z ，Jin L ，Ma Z ，Nizhamuding X ，Zeng J ，Zhang T ，Zhang J ，Zhou W ，Zhang C ... -  《-》

Simultaneous determination of tryptophan, kynurenine, kynurenic acid, xanthurenic acid and 5-hydroxytryptamine in human plasma by LC-MS/MS and its application to acute myocardial infarction monitoring.

Reliable methods for the determination of tryptophan and its metabolites are vital to the monitoring of biochemical states during the initiation and progression of cardiovascular disease. In the present study, a single-run liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the simultaneous determination of tryptophan (Trp) and its metabolites, including kynurenine (Kyn), kynurenic acid (KA), xanthurenic acid (XA) and 5-hydroxytryptamine (5-HT), in human plasma. The plasma samples were prepared using a protein precipitation approach, and the chromatographic separation was performed by gradient elution on a C18 column within a total analysis time of 3.5 min. The calibration ranges were 40-20,000 ng/mL for Trp, 4-2000 ng/mL for Kyn, 0.2-100 ng/mL for KA, 0.4-200 ng/mL for XA and 1-500 ng/mL for 5-HT, and the precision and accuracy were acceptable. The evaluation of recovery and internal standard-normalized matrix effect proved that the sample preparation approach was effective and the matrix effect could be negligible. The newly developed method was successfully applied to the analysis of plasma samples from healthy individuals and myocardial infarction patients. The findings suggested that the plasma concentrations of Trp, Kyn, 5-HT as well as the concentration ratios of Kyn/Trp and Trp/5-HT might serve as biomarkers for the monitoring of acute myocardial infarction.

Tong Q ，Song J ，Yang G ，Fan L ，Xiong W ，Fang J ... -  《-》

[Quantitative analysis of tryptophan and its metabolites in urine by ultra performance liquid chromatography-tandem mass spectrometry].

Li H ，Cui L ，Zhang G ，Zhang M ，Jiao L ，Wu W ... -  《-》

A sensitive UPLC-MS/MS method for the simultaneous determination of the metabolites in the tryptophan pathway in rat plasma.

Tryptophan (TRP) metabolism plays a crucial role in pathology and physiology. An imbalance in TRP metabolism has been implicated in the pathology of renal failure. To explore the changes in the TRP profile that occurred in renal failure, we induced experimental models of renal ischemia-reperfusion injury (RIRI) and chronic renal failure (CRF) in rats. A simple, rapid and sensitive method coupling ultra-high-performance liquid chromatography to triple quadrupole mass spectrometry (UPLC-MS/MS) was developed for the simultaneous determination of TRP and its seven major metabolites in plasma. The method was validated base on linearity, accuracy, precision, stability, recovery and the matrix effect. In the RIRI group, the levels of kynurenine (KYN), 5-hydroxyindoleacetic acid (5-HIAA), tryptamine (Trpm) and kynurenic acid (KA) were increased, and the level of TRP was decreased significantly compared with those of sham group. Moreover, the levels of most of the metabolites measured using the proposed method changed significantly with CRF progression. In the CRF group, the levels of KYN, 5-HIAA, Trpm, KA, 3-hydroxyanthranilic acid (3-HAA) and 3-hydroxykynurenine (3-HK) were dramatically elevated, and the level of TRP was markedly reduced compared with those of the CON group. Plasma precursor metabolite/product metabolite ratios were calculated to characterize enzyme activity. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) of the metabolites were performed for both groups. A Spearman correlation coefficient analysis between the metabolite concentrations and renal injury indicators was performed. We identified KYN, TRP, and 5-HIAA as potential metabolite biomarkers for AKI, and 5-HIAA, TRP, 3-HAA, KA, KYN and 3-HK as potential metabolite biomarkers for CRF (VIP>1 and p < 0.05). These results showed significant changes in the tryptophan metabolism profile under the two types of renal failure. In summary, the results of our study depict the changes in the TRP pathway, reveal the role of the TRP pathway in AKI and CRF, and provide insight into finding potential peripheral biomarkers of renal failure and elucidating the mechanism of diseases related to TRP metabolism disorders.

Dai M ，Wang Q ，Kou S ，Li X ，Jiang Z ，Sun L ，Huang X ... -  《-》