Alterations of Ceramides, Acylcarnitines, GlyceroLPLs, and Amines in NSCLC Tissues.

Abnormal lipid metabolism plays an important role in cancer development. In this study, nontargeted lipidomic study on 230 tissue specimens from 79 nonsmall cell lung cancer (NSCLC) patients was conducted using ultraperformance liquid chromatography-high-resolution mass spectrometry (UPLC-HRMS). Downregulation of sphingosine and medium-long-chain ceramides and short-medium-chain acylcarnitine, upregulation of long-chain acylcarnitine C20:0, and enhanced histamine methylation were revealed in NSCLC tissues. Compared with paired noncancerous tissues, adenocarcinoma (AC) tissues had significantly decreased levels of sphingosine, medium-long-chain ceramides (Cer d18:1/12:0 and Cer d16:1/14:0, Cer d18:0/16:0, Cer d18:1/16:0, Cer d18:2/16:0, Cer d18:2/18:0), short-medium-chain (C2-C16) acylcarnitines, LPC 20:0 and LPC 22:1, and significantly increased levels of the long-chain acylcarnitine C20:0, LPC 16:0, LPC P-16:0, LPC 20:1, LPC 20:2, glyceroPC, LPE 16:0, and LPE 18:2. In squamous cell carcinoma (SCC) tissues, sphingosine, Cer d18:2/16:0 and Cer d18:2/18:0, and short-medium-chain acylcarnitines had significantly lower levels, while long-chain acylcarnitines (C20:0, and C22:0 or C22:0 M), LPC 20:1, LPC 20:2, and N1,N12-diacetylspermine had significantly higher levels compared to controls. In AC and SCC tissues, the levels of LPG 18:0, LPG 18:1, and LPS 18:1 were significantly decreased, while the levels of ceramide-1-phosphate (C1P) d18:0/3:0 or LPE P-16:0, N1-acetylspermidine, and 1-methylhistamine were significantly increased than controls. Furthermore, an orthogonal partial least-squares-discriminant analysis (OPLS-DA) model based on a 4-lipid panel was established, showing good discrimination ability between cancerous and noncancerous tissues.

Efficacy of polysaccharide iron complex in IDA rats: A comparative study with iron protein succinylate and ferrous succinate.

Iron deficiency anemia (IDA) is the most common nutrient-related health problem in the world. There is still a lack of comprehensive comparative study on the efficacies of commonly used iron supplements such as polysaccharide iron complex (PIC), iron protein succinylate (IPS) and ferrous succinate (FS) for IDA. In this study, we compared the PIC, IPS and FS efficacies in IDA rats via intragastric administration. The results showed that the three iron supplements had similar efficacies. PIC/IPS/FS at a dose of 15 mg Fe/kg/d for 10 d increased the hematological and serum biochemical parameters to 2.15/2.12/2.18 (Hb), 1.71/1.67/1.69 (RBC), 2.10/2.11/2.12 (HCT), 1.26/1.22/1.22 (MCV), all 1.34 (MCH), 1.15/1.15/1.14 (MCHC), 1.94/1.82/1.91 (SF), 9.75/9.67/9.53 (SI), and 23.30/22.68/21.64 (TS) times, and reduced TIBC to 0.42/0.43/0.44 times, compared to untreated IDA rats. PIC performed slightly better than IPS and FS in restoring MCV level. Meanwhile, the heart, spleen and kidney coefficients reduced to 67%/74%/65% (heart), all 59% (spleen) and 87%/88%/88% (kidney), and the liver coefficient increased to 116%/115%/116%, compared to untreated IDA rats. The liver iron content was found to be more affected by IDA than the spleen iron content. PIC/IPS/FS at 15 mg Fe/kg/d increased organ iron contents to 4.20/3.97/4.03 times (liver) and 1.36/1.24/1.41 times (spleen) within 10 d compared to untreated IDA rats, and PIC-H and FS were slightly better than IPS in restoring spleen iron content. The results of this study can provide useful data information for the comparison of three iron supplements, PIC, IPS and FS.

Ultrahigh-performance liquid chromatography-high-resolution mass spectrometry-based plasma metabolomics study of thymoma and thymic hyperplasia.

RATIONALE: Thymoma is a rare malignant tumor but it is the most common primary tumor of the anterior mediastinum. The current imaging methods for thymoma screening suffer from false positive rate problems, and thymoma pathogenesis remains elusive. Study of thymoma metabolic characteristics could provide clues for improving the diagnosis and understanding the pathogenesis of thymoma. METHODS: Metabolic profiling of plasma from thymoma and thymic hyperplasia patients was performed using ultrahigh-performance liquid chromatography combined with high-resolution mass spectrometry in both positive and negative ionization modes. After pre- and post-processing, the dataset was divided into three age groups and statistical analysis was performed to select differential metabolites of thymoma. For feature identification, experimental tandem mass spectra were matched to those of databases and available chemical standards, and also manually annotated with plausible chemical structures to ensure high identification confidence. RESULTS: A total of 47 differential metabolites were identified in thymoma. Significantly higher levels of histidine, sphinganine 1-phosphate, lactic acid dimer, phenylacetylglutamine, LPC (18:3) and LPC (16:1), and significantly lower levels of phenylalanine, indole-3-propionic acid (IPA), hippuric acid and mesobilirubinogen were associated with thymoma. Tryptophan level in thymoma-associated myasthenia gravis (TAMG) was significantly lower than that of the MG(-) group. IPA and hippuric acid abundances exhibited increasing trends from indolent to aggressive thymoma. CONCLUSIONS: Our study revealed aberrant aromatic amino acid metabolism and fatty acid oxidation might be associated with thymoma. The identified unique metabolic characteristics of thymoma may provide valuable information for study of the molecular mechanism of thymoma pathogenesis, and improvement of diagnosis and discovery of new therapeutic strategies for thymoma.

Fluorescence tracing the degradation process of biodegradable PBAT: Visualization and high sensitivity.

Biodegradable plastics have emerged as a potential solution to the mounting plastic pollution crisis. However, current methods for evaluating the degradation of these plastics are limited in detecting structural changes rapidly and accurately, particularly for PBAT, which contains worrying benzene rings. Inspired by the fact that the aggregation of conjugated groups can endow polymers with intrinsic fluorescence, this work found that PBAT emits a bright blue-green fluoresces under UV irradiation. More importantly, we pioneered a degradation evaluation approach to track the degradation process of PBAT via fluorescence. A blue shift of fluorescence wavelength as the thickness and molecular weight of PBAT film decreased during degradation in an alkali solution was observed. Additionally, the fluorescence intensity of the degradation solution increased gradually as the degradation progressed, and was found to be exponentially correlated with the concentration of benzene ring-containing degradation products following filtration with the correlation coefficient is up to 0.999. This study proposes a promising new strategy for monitoring the degradation process with visualization and high sensitivity.

Changes in Lipidomics, Metabolomics, and the Gut Microbiota in CDAA-Induced NAFLD Mice after Polyene Phosphatidylcholine Treatment.

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in most parts of the world. Although there is no first-line drug approved for the treatment of NAFLD, polyene phosphatidylcholine (PPC) is used by clinicians to treat NAFLD patients. This study aimed to evaluate the efficacy of PPC on a mice model of NAFLD, and to study the PPC's mechanism of action. The mice were fed a choline-deficient, L-amino acid-defined (CDAA) diet to induce NAFLD and were subsequently treated with PPC. The treatment effects were evaluated by the liver index, histopathological examination, and routine blood chemistry analyses. Lipidomics and metabolomics analyses of 54 samples were carried out using ultraperformance liquid chromatography (UPLC) coupled to a mass spectrometer to select for changes in metabolites associated with CDAA diet-induced NAFLD and the effects of PPC treatment. The intestinal flora of mice were extracted for gene sequencing to find differences before and after the induction of NAFLD and PPC treatment. PPC significantly improved the CDAA diet-induced NAFLD condition in mice. A total of 19 metabolites including 5 polar metabolites and 14 lipids showed marked changes. In addition, significant differences in the abundance of Lactobacillus were associated with NAFLD. We inferred that the protective therapeutic effect of PPC on the liver was related to the supplement of phosphatidylcholine, lysophosphatidylcholine, and sphingomyelin (PC, LPC, and SM, resectively) and acylcarnitine metabolism. This study developed a methodology for exploring the pathogenesis of NAFLD and can be extended to other therapeutic agents for treating NAFLD.

Study on endogenous inhibitors against PD-L1: cAMP as a potential candidate.

The discovery of new anti-cancer drugs targeting the PD-1/PD-L1 pathway has been a research hotspot in recent years. In this study, biological affinity ultrafiltration (BAU), UPLC-HRMS, molecular dynamic (MD) simulations and molecular docking methods were applied to search for endogenous active compounds that can inhibit the binding of PD-L1 to PD-1. We screened dozens of potential cancer related endogenous compounds. Surprisingly, cyclic adenosine monophosphate (cAMP) was found to have a direct inhibitory effect on the PD-1/PD-L1 binding with an in vitro IC50 value of about 36.4 ± 9.3 µM determined by homogeneous time-resolved fluorescence (HTRF) assay. cAMP could recover the proliferation of Jurkat T cells co-cultured with DU-145 cells and may suppress PD-L1 expression of DU-145 cells. cAMP was demonstrated to bind and induce PD-L1 dimerization by FRET assay, and also predicted by MD simulations and molecular docking. The finding of cAMP as a potential inhibitor directly targeting the PD-1/PD-L1 interaction could advance our understanding of the activity of endogenous compounds regulating PD-L1.

Dual Effect of Tryptamine on Prostate Cancer Cell Growth Regulation: A Pilot Study.

Abnormal tryptophan metabolism is linked to cancer and neurodegenerative diseases, and tryptophan metabolites have been reported as potential prostate cancer (PCa) biomarkers. However, little is known about the bioactivities of tryptophan metabolites on PCa cell growth. In this study, MTT and transwell assays were used to study the cytotoxicities of 13 major tryptophan metabolites on PCa and normal prostate epithelial cell lines. Ultraperformance liquid chromatography-high resolution mass spectrometry (UPLC-HRMS) was used to analyze metabolic changes in cells treated with tryptamine. Flow cytometry, confocal imaging, and Western blot were used to test the apoptosis induced by tryptamine. It was shown that tryptamine had obvious inhibitory effects on PCa cell lines PC-3 and LNCaP, stronger than those on the normal prostate cell line RWPE-1. Tryptamine was further shown to induce apoptosis and inhibit PC-3 cell migration. Metabolic changes including amino acid metabolism related to cell proliferation and metastasis were found in PC-3 cells treated with tryptamine. Furthermore, a PC-3 xenograft mouse model was used to study the effect of tryptamine in vivo. The intratumoral injection of tryptamine was demonstrated to significantly reduce the tumor growth and tumor sizes in vivo; however, intraperitoneal treatment resulted in increased tumor growth. Such dual effects in vivo advanced our understanding of the bioactivity of tryptamine in regulating prostate tumor development, in addition to its major role as a neuromodulator.

Integrated Polypyrrole-Based Smart Clothing with Photothermal Conversion and Thermosensing Functions for Wearable Applications.

Integrated smart clothing with photothermal conversion and thermosensing functions is highly desired for next-generation smart wearable applications. Conducting polymer is a promising material that possesses efficient photothermal conversion performance, great sensitivity to temperature change, and excellent processing properties. In this study, we report a new wearable material using the conducting polymer polypyrrole (PPy) as a photothermal and thermosensing layer and nonwoven fabric as flexible textiles to fabricate integrated PPy-based smart clothing (IPSC). The surface temperature of the prepared IPSC can be as high as 68.4 °C with 808 nm near-infrared (NIR) irradiation at a power destiny of 1 kW/m2. Meanwhile, a temperature resolution of 1 °C can be achieved for IPSC. These superiorities are in favor of fabricating multifunctional smart wearables to satisfy the needs in future life.

Non-Small Cell Lung Cancer Detection and Subtyping by UPLC-HRMS-Based Tissue Metabolomics.

Non-small cell lung cancer (NSCLC) is the prevalent histological subtype of lung cancer. In this study, we performed ultraperformance liquid chromatography-high-resolution mass spectrometry (UPLC-HRMS)-based metabolic profiling of 227 tissue samples from 79 lung cancer patients with adenocarcinoma (AC) or squamous cell carcinoma (SCC). Orthogonal partial least squares-discriminant analysis (oPLS-DA) analyses showed that AC, SCC, and NSCLC tumors were discriminated from adjacent noncancerous tissue (ANT) and distant noncancerous tissue (DNT) samples with good accuracies (91.3, 100, and 88.3%), sensitivities (85.7, 100, and 83.9%), and specificities (94.3, 100, and 90.7%), using 12, 4, and 7 discriminant metabolites, respectively. The discriminant panel for AC detection included valine, sphingosine, glutamic acid γ-methyl ester, and lysophosphatidylcholine (LPC) (16:0), levels of which in tumor tissues were significantly altered. Valine, sphingosine, LPC (18:1), and leucine derivatives were used for SCC detection. The discrimination between AC and SCC had 96.8% accuracy, 98.2% sensitivity, and 85.7% specificity using a five-metabolite panel, of which valine and creatine had significant differences. The classification models were further verified with external validation sets, showing a promising prospect for NSCLC tissue detection and subtyping.

H2S probe CPC inhibits autophagy and promotes apoptosis by inhibiting glutathionylation of Keap1 at Cys434.

H2S is actual an endogenous signaling gas molecule and involved in a range of cell physiological processes. However, the mechanism of endogenous H2S regulating autophagy and apoptosis has not been thoroughly investigated. Here, we try to address this issue by using a H2S probe, (E)-2-(4-(4-(7-(diethylamino)-2-oxo-2H-chromene-3-carbonyl)-piperazin-1-yl)-styryl)-1, 3, 3-trimethyl-3H-indol-1-ium iodide (CPC), which could react with endogenous H2S. Herein, we reported that CPC inhibited autophagy and decreased the expression and activity of NF-E2-related factor 2 (Nrf2), then induced cell apoptosis. CPC inhibited autophagy and promoted apoptosis by inhibiting Nrf2 activation, which was H2S dependent. Furthermore, we found that CPC inhibited Nrf2 nucleus translocation by inhibiting glutathionylation of Kelch-like ECH-associated protein 1 (Keap1) at the Cys434 residue. CPC also inhibited various cancer cell growth, but had no effect on normal cell growth in vitro, and inhibited A549 cancer growth, but did not affect normal angiogenesis in vivo. Therefore, we not only found a new inhibitor of autophagy and Nrf2, but also suggested a novel mechanism that endogenous H2S could regulate autophagy, apoptosis and Nrf2 activity through regulating glutathionylation of Keap1 at the Cys434 residue.

Autophagy, Hyperlipidemia, and Atherosclerosis.

Autophagy is an evolutionarily conserved process in eukaryotes that processes the turnover of intracellular substances. Atherosclerosis is a disease caused by multiple factors, it mainly occurs on the walls of large and medium blood vessels and atherosclerotic plaques form in the intima of the blood vessels. Hyperlipidemia is considered to be a very dangerous factor leading to cardiovascular and cerebrovascular diseases, especially atherosclerosis. This chapter mainly introduces the key role of autophagy in hyperlipidemia and atherosclerosis, that is, impaired lipophagy affects the degradation of triacylglycerol, cholesterol, etc., leading to hyperlipidemia in atherosclerosis. In patients, excessive levels of autophagy accelerate the rupture of atherosclerotic plaque. This chapter also describes the advances in the treatment of atherosclerosis and hyperlipidemia by targeted autophagy.

Enhanced Ion Conduction via Epitaxially Polymerized Two-Dimensional Conducting Polymer for High-Performance Cathode in Zinc-Ion Batteries.

Aqueous zinc-ion batteries (AZIBs) are one of the promising choices for the future large-scale grid energy storage, in which Mn-based cathode materials have the advantages of low cost and environmental friendliness. However, their capacity delivery and cycling stability are limited by the large bulk-induced incomplete zincation and structure pulverization. Here, we develop a strategy of epitaxial polymerization in the liquid phase to fabricate two-dimensional (2D) MnOx/polypyrrole nanosheets to enhance the zinc-ion storage by realizing the efficient utilization of active materials and improving the structural stability via a polymerized framework. An ultrahigh capacity of 408 mAh g-1 is demonstrated at 1C rate, and an excellent capacity retention of 78% is realized after 2800 cycles at 5C rate for the AZIB. Electrochemical and morphological characterizations reveal that the unique 2D structure contributes to both the electron/ion conductivity and structural stability. The epitaxial polymerization of the conducting polymer in the liquid phase provides a new perspective to the synthesis of high-performance electrode materials and 2D conducting polymers.

Early Detection of Cystic Fibrosis Acute Pulmonary Exacerbations by Exhaled Breath Condensate Metabolomics.

The most common cause of death in cystic fibrosis (CF) patients is progressive lung function decline, which is punctuated by acute pulmonary exacerbations (APEs). A major challenge is to discover biomarkers for detecting an oncoming APE and allow for pre-emptive clinical interventions. Metabolic profiling of exhaled breath condensate (EBC) samples collected from CF patients before, during, and after APEs and under stable conditions (n = 210) was performed using ultraperformance liquid chromatography (UPLC) coupled to Orbitrap mass spectrometry (MS). Negative ion mode MS data showed that classification between metabolic profiles from "pre-APE" (pending APE before the CF patient had any signs of illness) and stable CF samples was possible with good sensitivities (85.7 and 89.5%), specificities (88.4 and 84.1%), and accuracies (87.7 and 85.7%) for pediatric and adult patients, respectively. Improved classification performance was achieved by combining positive with negative ion mode data. Discriminant metabolites included two potential biomarkers identified in a previous pilot study: lactic acid and 4-hydroxycyclohexylcarboxylic acid. Some of the discriminant metabolites had microbial origins, indicating a possible role of bacterial metabolism in APE progression. The results show promise for detecting an oncoming APE using EBC metabolites, thus permitting early intervention to abort such an event.

A graphene-based smart thermal conductive system regulated by a reversible pressure-induced mechanism.

Thermal dissipation and thermal insulation are important for maintaining the normal operation of devices, extending the service life of instruments, ensuring efficient energy utilization, and improving temperature-related human comfort. Yet it is difficult to achieve both the functions of thermal dissipation and thermal insulation in a single material with a specific thermal conductivity under specific conditions. In this work, based on the huge difference in thermal conductivity between air and reduced graphene oxide (rGO), a pressure-induced mechanism is used to regulate the amount of air inside an rGO foam, so that a periodic reversible change of thermal conductivity can be realized, achieving the dual functions of thermal dissipation and thermal insulation to meet the requirements of different application scenarios. Further fitting calculations suggest that the thermal conductivity of rGO foam is positively and negatively associated with the applied pressure and temperature, respectively, and it can be calculated for given pressure and temperature conditions. The pressure-induced reversible regulation of thermal conductivity in rGO foam provides a new design construct for smart thermal-management devices, and a new direction of application for 2D materials.

Mass Spectrometry-Based Non-targeted Metabolic Profiling for Disease Detection: Recent Developments.

Mass spectrometry (MS) plays an important role in seeking biomarkers for disease detection. High-quality quantitative data is needed for accurate analysis of metabolic perturbations in patients. This article describes recent developments in MS-based non-targeted metabolomics research with applications to the detection of several major common human diseases, focusing on study cohorts, MS platforms utilized, statistical analyses and discriminant metabolite identification. Potential disease biomarkers recently discovered for type 2 diabetes, cardiovascular disease, hepatocellular carcinoma, breast cancer and prostate cancer through metabolomics are summarized, and limitations are discussed.

Flow Injection-Traveling-Wave Ion Mobility-Mass Spectrometry for Prostate-Cancer Metabolomics.

Flow injection-traveling-wave ion mobility-mass spectrometry (FI-TWIM-MS) was applied to the nontargeted metabolic profiling of serum extracts from 61 prostate-cancer (PCa) patients and 42 controls with an analysis speed of 6 min per sample, including a 3 min wash run. Comprehensive data mining of the mobility-mass domain was used to discriminate species with various charge states and filter matrix salt-cluster ions. Specific criteria were developed to ensure correct grouping of adducts, in-source fragments, and impurities in the data set. Endogenous metabolites were identified with high confidence using FI-TWIM-MS/MS and collision-cross-section (CCS) matching with chemical standards or CCS databases. PCa patient samples were distinguished from control samples with good accuracies (88.3-89.3%), sensitivities (88.5-90.2%), and specificity (88.1%) using supervised multivariate classification methods. Although largely underutilized in metabolomics studies, FI-TWIM-MS proved advantageous in terms of analysis speed, separation of ions in complex mixtures, improved signal-to-noise ratio, and reduction of spectral congestion. Results from this study showcase the potential of FI-TWIM-MS as a high-throughput metabolic-profiling tool for large-scale metabolomics studies.

Higher risk of myocardial injury in chest pain patients with elevated red blood cell distribution width.

BACKGROUND: High level of red blood cell distribution width (RDW) has been associated with adverse outcomes in coronary artery disease patients. We aimed to investigate the relationship between RDW and the risk of myocardial injury in chest pain patients. METHODS AND RESULTS: We retrospectively reviewed 2078 chest pain patients with suspected acute myocardial infarction. Myocardial injury was defined as high-sensitivity cardiac troponin T (hs-cTnT) >14 ng/L. RDW was associated with hs-cTnT (r = 0.607) and the risk of myocardial injury stepwise increased across increasing RDW quartiles in all subgroups based on age and sex. The receiver operating characteristic curve analysis was calculated to assess the elevated RDW to predict myocardial injury, with the cutoff value of 13.25%. RDW had a high sensitivity (78.10%), specificity (87.44%), as well as positive predictive value (77.48%). The area under the curve (AUC) for all patients was 0.88 (95%CI 0.87, 0.90) and there is no statistical significant in AUCs for all subgroups. CONCLUSIONS: Elevated RDW was significantly associated with a higher risk of myocardial injury in chest pain patients with potential acute myocardial infarction. The RDW may be helpful to identify myocardial injury in such patients.

An open holey structure enhanced rate capability in a NaTi2(PO4)3/C nanocomposite and provided ultralong-life sodium-ion storage.

Sodium-ion battery (SIB) technology is competitive in the fields of transportation and grid storage, which require electrode materials showing rapid energy conversion (high rate capability) and long cycle life. In this work, a NaTi2(PO4)3/C (NTP/C) nanocomposite with an open holey-structured framework was successfully prepared for the first time using a solvothermal reaction followed by pyrolysis. The nanocomposite realized fast sodium-ion transport and thus preferable battery performances. Within the wide rate range of 0.5-50C, only a very small decrease in capacity from 124 to 120 mA h g-1 was observed. A high discharge capacity of 103 mA h g-1 (88.3% retention of the 1st cycle) was delivered even after 10 000 cycles at an ultrahigh rate of 50C without any obvious morphological change and without structural pulverization. Forming open channels for ion transport proved to contribute to such performance enhancement and therefore has the potential to become a universal model for the development of sustainable electrode materials in SIBs and other battery systems.

Unprecedented sensitivity towards pressure enabled by graphene foam.

Reduced graphene oxide foam (RGOF)-based pressure sensors have been fabricated through the combination of ultrasonic dispersion and freeze-drying methods. Due to the maintenance of the highly disordered structure of the ultrasonic dispersed graphene oxides before the freezing process, the RGOF sensors demonstrated an ultra-high sensitivity of 22.8 kPa-1, an ultra-low detection limit of around 0.1 Pa, and a superior separation of 0.2-Pascal-scale difference.

Age-sex distribution of patients with high-sensitivity troponin T levels below the 99th percentile.

BACKGROUND: Recently, very low concentrations of high-sensitivity cardiac troponin T (hs-cTnT), below the 99th percentile, have been used to immediately exclude acute myocardial infarction in certain patients without taking their age and sex into consideration. RESULTS: The hs-cTnT values below the 99th percentile (≤ 14 ng/L) were higher in men (p = 0.000) and significantly increased with age (p = 0.000) among both men and women. In addition, hs-cTnT was positively associated with age (r = 0.459, p = 0.000), myoglobin (r = 0.392, p = 0.000), and creatine kinase-MB (r = 0.133, p = 0.000). Moreover, males were younger (p = 0.001) and had higher myoglobin (p = 0.000) and creatine kinase-MB (p = 0.000) concentrations than females. MATERIALS AND METHODS: A total of 5585 consecutive subjects who presented with non-traumatic chest pain/discomfort to the inpatient, outpatient, or emergency department and who underwent high-sensitivity troponin T, myoglobin and creatine kinase-MB testing at presentation, with hs-cTnT below the 99thpercentile (≤ 14 ng/L), were eligible for enrollment. CONCLUSIONS: We suggest that patients' age, sex and levels of myocardial injury biomarkers should be taken into consideration when ruling out acute myocardial infarction and/or adverse prognostic implications in patients who have very low hs-cTnT concentrations.