Current Understanding of Methamphetamine-Associated Metabolic Changes Revealed by the Metabolomics Approach

Metabolomics is a powerful tool used in the description of metabolic system perturbations caused by diseases or abnormal conditions, and it usually involves qualitative and/or quantitative metabolome determination, accompanied by bioinformatics assessment. Methamphetamine is a psychostimulant with serious abuse potential and due to the absence of effective pharmacotherapy and a high recurrence potential, methamphetamine addiction is a grave issue. Moreover, its addiction mechanisms remain unclear, probably due to the lack of experimental models that reflect personal genetic variances and environmental factors determining drug addiction occurrence. The metabolic approach is only recently being used to study the metabolic effects induced by a variety of methamphetamine exposure statuses, in order to investigate metabolic disturbances related to the adverse effects and discover potential methamphetamine addiction biomarkers. To provide a critical overview of methamphetamine-associated metabolic changes revealed in recent years using the metabolomics approach, we discussed methamphetamine toxicity, applications of metabolomics in drug abuse and addiction studies, biological samples used in metabolomics, and previous studies on metabolic alterations in a variety of biological samples—including the brain, hair, serum, plasma, and urine—following methamphetamine exposure in animal studies. Metabolic alterations observed in animal brain and other biological samples after methamphetamine exposure were associated with neuronal and energy metabolism disruptions. This review highlights the significance of further metabolomics studies in the area of methamphetamine addiction research. These findings will contribute to a better understanding of metabolic changes induced by methamphetamine addiction progress and to the design of further studies targeting the discovery of methamphetamine addiction biomarkers and therapeutic targets.

Metabolomic study of polyamines in rat urine following intraperitoneal injection of γ-hydroxybutyric acid

INTRODUCTION

Recently, illegal abuse of γ-hydroxybutyric acid (GHB) has increased in drug-facilitated crimes, but the determination of GHB exposure and intoxication is difficult due to rapid metabolism of GHB. Its biochemical mechanism has not been completely investigated. And a metabolomic study by polyamine profile and pattern analyses was not performed in rat urine following intraperitoneal injection with GHB.

OBJECTIVES

Urinary polyamine (PA) profiling by gas chromatography-tandem mass spectrometry was performed to monitor an altered PA according to GHB administration.

METHODS

Polyamine profiling analysis by gas chromatography-mass spectrometry combined with star pattern recognition analysis was performed in this study. The multivariate statistical analysis was used to evaluate discrimination among control and GHB administration groups.

RESULTS

Six polyamines were determined in control, single and multiple GHB administration groups. Star pattern showed distorted hexagonal shapes with characteristic and readily distinguishable patterns for each group. N¹-Acetylspermine (p < 0.001), putrescine (p < 0.006), N¹-acetylspermidine (p < 0.009), and spermine (p < 0.027) were significantly increased in single administration group but were significantly lower in the multiple administration group than in the control group. N¹-Acetylspermine was the main polyamine for discrimination among control, single and multiple administration groups. Spermine showed similar levels in single and multiple administration groups.

CONCLUSIONS

The polyamine metabolic pattern was monitored in GHB administration groups. N¹-Acetylspermine and spermine were evaluated as potential biomarkers of GHB exposure and addiction.

Amalgam Strength Resistance to Various Contaminants

Purpose:

The purpose of this study was to quantify the relative strength tolerance of 1-day and 30-day amalgam following saturation contamination with water, saliva, blood, and handpiece lubricant oil during condensation.

Methods and Materials:

Valiant PhD XT amalgam was tested with 300 shear-strength (N=15) and 120 compressive-strength (N=6) specimens, divided into 1-day and 30-day groups, each with control, water, saliva, blood, and lubricant oil contamination samples. Shear specimens were condensed in 4 × 4-mm anchor wells inundated with contaminant fluids before adding a ring mold with 3.5-mm-diameter central hole adapted immediately to the top for continued condensation under contaminant-submerged conditions. Compressive specimen samples were condensed while completely inundated by each contaminant using the American Dental Association Specification No. 1 amalgam mold apparatus. All specimens were tested with the Instron E3000 and E10000 at 0.5 mm/min, with data statistically evaluated using the Kruskal-Wallis procedure with IBM SPSS v25 and Wilcoxon signed ranks test.

Results:

Shear test values (mean±SD) following intracapsular and extracapsular contamination after 30 days under 100% humidity at 37°C were as follows: control, 30.97±5.41 MPa; water, 30.63 ±4.41 MPa; saliva, 27.54 ±4.56 MPa; blood, 24.92 ±3.48 MPa; lubricant oil, 26.06 ±4.06 MPa. Compressive strengths (±SD) of similarly contaminated samples were as follows: control, 447.7 ±76.3 MPa; water, 343.6 ±70.1 MPa; saliva, 307.7 ±24.0 MPa; blood, 281.6 ±35.2 MPa; lubricant oil, 227.8 ±16.9 MPa.

Conclusions:

Saliva, blood, and handpiece oil diminish compressive strength significantly, but water shows no statistically significant effect (p&gt;0.05). Amalgam 30-day shear strength is significantly altered by contamination with water, blood, or handpiece lubricant oil (p&lt;0.05). Remaining amalgam strength after extensive contamination may still be clinically functional relative to a previous ADA recommendation and when compared with resin-based direct restorative materials.

Monitoring of altered amino acid metabolic pattern in rat urine following intraperitoneal injection with γ-hydroxybutyric acid

INTRODUCTION

γ-Hydroxybutyric acid is a well-known prescription medicine that is used for the clinical treatment of alcohol dependence and narcolepsy. However, the biochemical mechanism underlying γ-hydroxybutyric acid intoxication remains unclear, and metabolomic amino acid profiling and pattern analyses have not been attempted following treatment with γ-hydroxybutyric acid.

OBJECTIVES

We carried out urinary amino acid profiling and pattern analyses in rats to determine the biochemical events associated with altered amino acid metabolism and biomarker detection of intoxication following treatment with γ-hydroxybutyric acid.

METHODS

Metabolic profiling analysis of amino acids in rat urine samples was performed as ethoxycarbonyl/tert-butyldimethylsilyl derivatives by gas chromatography-mass spectrometry following intraperitoneal administration of γ-hydroxybutyric acid once per day for 1 and 10 consecutive days.

RESULTS

A total of 28 amino acids were positively identified in urine samples from the control, single and multiple groups treated with γ-hydroxybutyric acid. Their levels from the single and multiple treated groups were normalized to the corresponding mean control values. The star graphic pattern of the amino acids was characteristic and readily distinguishable for each group owing to its distorted nonacosagonal shape. In the principle component analysis, we monitored phenylalanine, glutamic acid, aspartic acid, asparagine, and methionine as contributing factors that discriminated the three groups.

CONCLUSION

The present metabolomic study may explain the altered metabolism of amino acids following administration, and intoxication with γ-hydroxybutyric acid.

Multi-omics analysis reveals that ornithine decarboxylase contributes to erlotinib resistance in pancreatic cancer cells

Molecular and metabolic alterations in cancer cells are one of the leading causes of acquired resistance to chemotherapeutics. In this study, we explored an experimental strategy to identify which of these alterations can induce erlotinib resistance in human pancreatic cancer. Using genetically matched erlotinib-sensitive (BxPC-3) and erlotinib-resistant (BxPC-3ER) pancreatic cancer cells, we conducted a multi-omics analysis of metabolomes and transcriptomes in these cells. Untargeted and targeted metabolomic analyses revealed significant changes in metabolic pathways involved in the regulation of polyamines, amino acids, and fatty acids. Further transcriptomic analysis identified that ornithine decarboxylase (ODC) and its major metabolite, putrescine, contribute to the acquisition of erlotinib resistance in BxPC-3ER cells. Notably, either pharmacological or genetic blockage of ODC was able to restore erlotinib sensitivity, and this could be rescued by treatment with exogenous putrescine in erlotinib-resistant BxPC-3ER cells. Moreover, using a panel of cancer cells we demonstrated that ODC expression levels in cancer cells are inversely correlated with sensitivity to chemotherapeutics. Taken together, our findings will begin to uncover mechanisms of acquired drug resistance and ultimately help to identify potential therapeutic markers in cancer.

Probabilistic dietary exposure to ethyl carbamate from fermented foods and alcoholic beverages in the Korean population

The occurrence of ethyl carbamate was investigated in fermented foods and alcoholic beverages of the Korean total diet study. The concentrations of ethyl carbamate ranged from not detected to 166.5 μg kg^-1. Dietary exposure to ethyl carbamate was estimated by the probabilistic method. Estimated intakes of ethyl carbamate from foods and alcoholic beverages were 4.12 ng kg^-1 body weight (bw) per day for average consumers and 12.37 ng kg^-1 bw/day for 95th percentile high consumers. The major foods contributing to ethyl carbamate exposure were soy sauce (63%), followed by maesilju (plum liqueur, 30%), whisky (5%), and bokbunjaju (black raspberry wine, 2%). On the basis of the benchmark dose lower confidence limit 10% (BMDL₁₀) of 0.3 mg kg^-1 bw/day, margins of exposure were 128,000 for mean exposure and 40,000 for 95th percentile exposure. This indicates that the exposure of the Korean general population for ethyl carbamate is of low concern. However, careful vigilance should be continued for high consumers of fermented foods and alcoholic beverages.

Major Histocompatibilty Complex-Restricted Adaptive Immune Responses to CT26 Colon Cancer Cell Line in Mixed Allogeneic Chimera

BACKGROUND

Although the induction of mixed allogeneic chimera shows promising clinical tolerance results in organ transplantation, its clinical relevance as an anti-cancer therapy is yet unknown. We introduced a mixed allogenic chimera setting with the use of a murine colon cancer cell line, CT26, by performing double bone marrow transplantation.

METHODS

We analyzed donor- and recipient-restricted anti-cancer T-cell responses, and phenotypes of subpopulations of T cells. The protocol involves challenging 1 × 10⁵ cells of CT26 cells intra-hepatically on day 50 after bone marrow transplantation, and, by use of CT26 lysates and an H-2L^d-restricted AH1 pentamer, flow cytometric analysis was performed to detect the generation of cancer-specific CD4⁺ and CD8⁺ T cells at various time points.

RESULTS

We found that immunocompetence against tumors depends heavily on cancer-specific CD8⁺ T-cell responses in a major histocompatibility complex-restricted manner; the evidence was further supported by the increase of interferon-γ-secreting CD4⁺ T cells. Moreover, we demonstrated that during the effector immune response to CT26 cancer challenge, there was a presence of central memory cells (CD62L^hiCCR7⁺) as well as effector memory cells (CD62L^loCCR7^-). Moreover, mixed allogeneic chimeras (BALB/c to C56BL/6 or vice versa) showed similar or heightened immune responses to CT26 cells compared with that of wild-type mice.

CONCLUSIONS

Our results suggest that the responses of primary immunocompetency and of pre-existing memory T cells against allogeneic cancer are sustained and preserved long-term in a mixed allogeneic chimeric environment.

Comparative metabolomic analysis of HPAC cells following the acquisition of erlotinib resistance

Pancreatic cancer is one of the most lethal types of cancer, due to difficulty in early detection and the limited efficacy of available treatments. Erlotinib is used to inhibit the epidermal growth factor receptor for the treatment of pancreatic cancer; however, erlotinib resistance is a major issue and the mechanisms underlying the development of erlotinib resistance remain unclear. To better understand the alterations in tumor metabolism by acquired resistance to erlotinib, an erlotinib-resistant pancreatic cancer cell line (HPAC-ER) was established, followed by a comparison of the metabolic characteristics between these cells and their erlotinib-sensitive parental cells (HPAC). This comparison was accomplished through mass spectrometry-based targeted metabolic profiling. Five metabolite groups (acylcarnitines, amino acids and biogenic amines, glycerophospholipids, sphingolipids and monosaccharides) were semi-quantified and compared statistically. These results revealed significant differences between the two groups of cells. A significant increase in the level of short-chain acylcarnitines and selected lysophosphatidylcholines, and a significant decrease in the level of acyl-alkyl-phosphatidylcholines and one sphingolipid, were observed in the HPAC-ER cells compared with the HPAC cells. The metabolic changes observed in the present study support the theory that there are increased metabolic demands in erlotinib-resistant cancer, reflecting the changes in acetyl-CoA-associated and choline phospholipid metabolism. These findings will aid in elucidating the changes that occur in pancreatic cancer metabolism through the acquired resistance to erlotinib, and in the identification of biomarkers for the early detection of pancreatic cancer.

Positive correlation of serum HDL cholesterol with blood mercury concentration in metabolic syndrome Korean men (analysis of KNANES 2008-2010, 2013)

PURPOSE

High-density lipoprotein cholesterol (HDLC) is anti-inflammatory in the basal state and pro-inflammatory during the acute-phase response. Blood mercury also has an inflammatory property. Therefore, the aim of this study was to investigate the relationship between serum HDLC and blood mercury concentration in relation with metabolic syndrome (MS).

METHODS

The data of 7616 subjects (3713 men and 3903 women), over 20 years of age, from 2008 to 2013, Korea National Health and Nutrition Examination Survey were selected for cross-sectional analyses. Correlation and regression of serum HDLC and blood mercury were initially done. We compared serum HDLC concentration according to blood mercury quartile after adjustment for relevant variables in subjects with MS.

RESULTS

Mean blood mercury concentrations is 5.6 and 3.9 μg/dL in men and women, respectively. Blood mercury concentration in MS subjects was positively correlated with serum HDLC concentration, especially in men. In addition, HDLC concentration was significantly higher according to the higher blood mercury quartile.

CONCLUSION

Serum HDLC was positively associated with blood mercury concentration in MS Korean men. Therefore, elevated blood mercury may be a factor to increase serum HDLC concentration in MS men.

Evaluation of interface trap densities and quantum capacitance in carbon nanotube network thin-film transistors

The interface trap density in single-walled carbon nanotube (SWNT) network thin-film transistors (TFTs) is a fundamental and important parameter for assessing the electronic performance of TFTs. However, the number of studies on the extraction of interface trap densities, particularly in SWNT TFTs, has been insufficient. In this work, we propose an efficient technique for extracting the energy-dependent interface traps in SWNT TFTs. From the measured dispersive, frequency-dependent capacitance-voltage (C-V) characteristics, the dispersive-free, frequency-independent C-V curve was obtained, thus enabling the extraction and analysis of the interface trap density, which was found to be approximately 8.2 × 10(11) eV(-1) cm(-2) at the valence band edge. The frequency-independent C-V curve also allows further extraction of the quantum capacitance in the SWNT network without introducing any additional fitting process or parameters. We found that the extracted value of the quantum capacitance in SWNT networks is lower than the theoretical value in aligned SWNTs due to the cross point of SWNTs on the SWNT network. Therefore, the method proposed in this work indicates that the C-V measurement is a powerful tool for obtaining deep physical insights regarding the electrical performance of SWNT TFTs.

Human periodontal ligament stem cells suppress T-cell proliferation via down-regulation of non-classical major histocompatibility complex-like glycoprotein CD1b on dendritic cells

BACKGROUND AND OBJECTIVE

Periodontal ligament stem cells (PDLSCs) from the periodontal ligament tissue were recently identified as mesenchymal stem cells (MSCs). The capabilities of PDLSCs in periodontal tissue or bone regeneration have been reported, but their immunomodulatory role in T-cell immune responses via dendritic cells (DCs), known as the most potent antigen-presenting cell, has not been studied. The aim of this study is to understand the immunological function of homogeneous human STRO-1⁺ CD146⁺ PDLSCs in DC-mediated T-cell immune responses to modulate the periodontal disease process.

MATERIAL AND METHODS

We utilized highly purified (> 95%) human STRO-1⁺ CD146⁺ PDLSCs and human bone marrow mesenchymal stem cells (BMSCs). Each stem cell was co-cultured with human monocyte-derived DCs in the presence of lipopolysaccharide isolated from Porphyromonas gingivalis, a major pathogenic bacterium responsible for periodontal disease, in vitro to examine the immunological effect of each stem cell on DCs and DC-mediated T-cell proliferation.

RESULTS

We discovered that STRO-1⁺ CD146⁺ PDLSCs, as well as BMSCs, significantly decreased the level of non-classical major histocompatibility complex glycoprotein CD1b on DCs, resulting in defective T-cell proliferation, whereas most human leukocyte antigens and the co-stimulatory molecules CD80 and CD86 in/on DCs were not significantly affected by the presence of BMSCs or STRO-1⁺ CD146⁺ PDLSCs.

CONCLUSIONS

This study unveiled an immunomodulatory role of STRO-1⁺ CD146⁺ PDLSCs in negatively regulating DC-mediated T-cell immune responses, demonstrating their potential to be utilized in promising new stem cell therapies.

An LC-MS/MS method for the determination of five erectile dysfunction drugs and their selected metabolites in hair

The abuse of sildenafil and its analogous, accelerated by their inappropriate or illegal distribution, is a serious social issue globally. However, no studies have been conducted to monitor these drugs simultaneously in hair, which can provide valuable information on chronic drug use. In the present study, an LC-MS/MS method was developed for the simultaneous determination in hair of five erectile dysfunction drugs having a high risk for abuse (mirodenafil, sildenafil, tadalafil, udenafil and vardenafil) and their selected metabolites (SK3541, desmethylsildenafil, DA8164 and desethylvardenafil). The novel method was fully validated after optimizing matrix effects and extraction efficiency. The optimized sample preparation included acidic methanol extraction followed by solid phase extraction using C18 mixed mode strong cation exchange polymeric cartridges. The prepared samples were analyzed by LC-MS/MS with electrospray ion source in the positive ionization mode. The validation results proved the method to be selective, sensitive, accurate and precise, with acceptable linearity within calibration ranges. LODs ranged from 0.05 (DA8164) to 1 ng/10 mg hair (tadalafil). LOQs were 1 ng/10 mg hair except for DA8164 and vardenafil, of which they were 2.5 ng/10 mg hair. No significant variations were observed by different sources of matrices in both human and rat hair, except for tadalafil, for which a stable isotope-labeled internal standard was effective. The animal study suggested hair pigmentation was a major factor for the incorporation of the drugs and metabolites into hair. However, a wide variation of the sildenafil-to-desmethylsildenafil ratios was observed in human hair samples. The developed method will be very useful for monitoring the abuse of erectile dysfunction drugs for both legal and public health aspects.