Urinary metabolomics of HCV patients with severe liver fibrosis before and during the sustained virologic response achieved by direct acting antiviral treatment.

Hepatitis C virus (HCV) infection induces a long-term inflammatory response and oxidative-stress in the liver microenvironment, leading to hepatic fibrosis and metabolic alterations. Direct-acting-antiviral-agents (DAAs) induce HCV-clearance, even though liver damage is only partially restored. In this context, understanding the impact of viral-eradication on liver metabolic activities could allow optimizing the metabolic care of the patient. The present prospective longitudinal study aims at characterizing the urinary metabolic profile of HCV-induced severe liver fibrosis and the metabolic changes induced by DAAs and HCV-clearance by nuclear magnetic resonance-based metabolomics. The urinary metabolic profile of 23 HCV males with severe liver fibrosis and 20 age-matched healthy-controls was analyzed by NMR-based-metabolomics before starting DAAs, at the end-of-therapy, after one and three months of follow-up. The urinary metabolic profile of patients with severe liver fibrosis was associated to pseudouridine, hypoxanthine, methylguanidine and dimethylamine, highlighting a profile related to oxidative damage, and to tyrosine and glutamine, related to a decreased breakdown of aromatic aminoacids and ammonia detoxification, respectively. 1-methylnicotinamide, a catabolic intermediate of nicotinamide-adenine-dinucleotide, was significantly increased in HCV-patients and restored after HCV-clearance, probably due to the reduced hepatic inflammation. 3-hydroxy-3-methylbutyrate, an intermediate of leucine-catabolism which was permanently restored after HCV-clearance, suggested an improvement of skeletal muscle protein synthesis. Finally, 3-hydroxyisobutyrate and 2,3-dihydroxy-2-methylbutyrate, intermediates of valine-catabolism, glycine and choline increased temporarily during therapy, resulting as potential biomarkers of DAAs systemic effects.

High detection rate in [18F]PSMA-1007 PET: interim results focusing on biochemical recurrence in prostate cancer patients.

OBJECTIVE: 18F-labeled prostate-specific membrane antigen (PSMA) ligand, [18F]PSMA-1007, has the benefit of a higher synthetic yield and minimal excretion in the urine. High detection efficacy was reported in biochemical recurrence (BCR) of prostate cancer after radical prostatectomy. Thus, we evaluated the preliminary diagnostic utility of [18F]PSMA-1007 PET in patients with prostate cancer, focusing on the BCR which is not detected on conventional imaging. METHODS: We enrolled a total of 28 patients (age 51-79 years) with BCR of prostate cancer. BCR was defined as a continuous increase in PSA after radical prostatectomy or radiation therapy without any apparent recurrent lesions on conventional diagnostic imaging (CT and bone scintigraphy). PSMA-PET scanning was performed approximately 60 min after intravenous injection of [18F]PSMA-1007 (259 ± 37 MBq). PSMA-PET images were evaluated for lesion detection as well as its relation to PSA values and location. RESULTS: Abnormal uptake, which was suspected to be recurrence or metastasis, was detected in 92.9% (26/28) of patients with BCR. The SUVmax was 8.4 ± 6.4 in local recurrence, 11.5 ± 11.8 in pelvic lymph nodes (LN), and 4.1 ± 1.6 in bone metastasis. The detection rates were 66.7% in the PSA group-1 (0.1-0.5 ng/mL), 85.7% in the PSA group-2 (0.5-1.0 ng/mL), and 100% in the PSA group-3 (above 1.0 ng/mL). Among the PET-positive BCR patients (n = 26), local recurrence was detected in 57.7% (15/26), pelvic LN in 42.3% (11/26), and bone metastasis in 15.4% (4/26). In 53% (8/15) of BCR patients who were suspected of local recurrence, focal uptake was detected adjacent to the bladder on [18F]PSMA-1007 PET. This suggested the significant advantage of having minimal physiological urine excretion. CONCLUSIONS: [18F]PSMA-1007 PET showed a high detection rate in recurrent and metastatic lesions. In patients with BCR, its high detection led to suitable treatment strategies, such as salvage radiation therapy or surgical removal of recurrent lymph nodes. TRIAL REGISTRATION: (UMIN Clinical Trials Registry) UMIN000037697.

Absorption, Pharmacokinetics, and Urinary Excretion of Pyridines After Consumption of Coffee and Cocoa-Based Products Containing Coffee in a Repeated Dose, Crossover Human Intervention Study.

SCOPE: The present study assesses the absorption, pharmacokinetics, and urinary excretion of coffee pyridines and their metabolites after daily regular exposure to specific dosages of coffee or cocoa-based products containing coffee (CBPCC), considering different patterns of consumption. METHODS AND RESULTS: In a three-arm, crossover, randomized trial, 21 volunteers are requested to randomly consume for 1 month: one cup of espresso coffee per day, three cups of espresso coffee per day, or one cup of espresso coffee plus two CBPCC twice per day. The last day of the one-month treatment, blood and urine samples are collected for 24 h. Trigonelline, N-methylpyridinium, N-methylnicotinamide, and N-methyl-4-pyridone-5-carboxamide are quantified. Trigonelline and N-methylpyridinium absorption curves and 24-h urinary excretion reflect the daily consumption of different servings of coffee or CBPCC, showing also significant differences in main pharmacokinetic parameters. Moreover, inter-subject variability due to sex and smoking is assessed, showing sex-related differences in the metabolism of trigonelline and smoking-related ones for N-methylpyridinium. CONCLUSION: The daily exposure to coffee pyridines after consumption of different coffee dosages in a real-life setting is established. This data will be useful for future studies aiming at evaluating the bioactivity of coffee-derived circulating metabolites in cell experiments, mimicking more realistic experimental conditions.

Urinary Excretion of N1-Methylnicotinamide and N1-Methyl-2-Pyridone-5-Carboxamide and Mortality in Kidney Transplant Recipients.

It is unclear whether niacin nutritional status is a target for improvement of long-term outcome after renal transplantation. The 24-h urinary excretion of N1-methylnicotinamide (N1-MN), as a biomarker of niacin status, has previously been shown to be negatively associated with premature mortality in kidney transplant recipients (KTR). However, recent evidence implies higher enzymatic conversion of N1-MN to N1-methyl-2-pyridone-5-carboxamide (2Py) in KTR, therefore the need exists for interpretation of both N1-MN and 2Py excretion for niacin status assessment. We assessed niacin status by means of the 24-h urinary excretion of the sum of N1-MN and 2Py (N1-MN + 2Py), and its associations with risk of premature mortality in KTR. N1-MN + 2Py excretion was measured in a longitudinal cohort of 660 KTR with LS-MS/MS. Prospective associations of N1-MN + 2Py excretion were investigated with Cox regression analyses. Median N1-MN + 2Py excretion was 198.3 (155.9-269.4) µmol/day. During follow-up of 5.4 (4.7-6.1) years, 143 KTR died, of whom 40 due to an infectious disease. N1-MN + 2Py excretion was negatively associated with risk of all-cause mortality (HR 0.61; 95% CI 0.47-0.79; p < 0.001), and infectious mortality specifically (HR 0.47; 95% CI 0.29-0.75; p = 0.002), independent of potential confounders. Secondary analyses showed effect modification of hs-CRP on the negative prospective association of N1-MN + 2Py excretion, and sensitivity analyses showed negative and independent associations of N1-MN and 2Py excretion with risk of all-cause mortality separately. These findings add further evidence to niacin status as a target for nutritional strategies for improvement of long-term outcome in KTR.

A Noninvasive Urine Metabolome Panel as Potential Biomarkers for Diagnosis of T Cell-Mediated Renal Transplant Rejection.

Acute T cell-mediated rejection (TCMR) is a major complication after renal transplantation. TCMR diagnosis is very challenging and currently depends on invasive renal biopsy and nonspecific markers such as serum creatinine. A noninvasive metabolomics panel could allow early diagnosis and improved accuracy and specificity. We report, in this study, on urine metabolome changes in renal transplant recipients diagnosed with TCMR, with a view to future metabolomics-based diagnostics in transplant medicine. We performed urine metabolomic analyses in three study groups: (1) 7 kidney transplant recipients with acute TCMR, (2) 15 kidney transplant recipients without rejection but with impaired kidney function, and (3) 6 kidney transplant recipients with stable renal function, using 1H-nuclear magnetic resonance. Multivariate modeling of metabolites suggested a diagnostic panel where the diagnostic accuracy of each metabolite was calculated by receiver operating characteristic curve analysis. The impaired metabolic pathways associated with TCMR were identified by pathway analysis. In all, a panel of nine differential metabolites encompassing nicotinamide adenine dinucleotide, 1-methylnicotinamide, cholesterol sulfate, gamma-aminobutyric acid (GABA), nicotinic acid, nicotinamide adenine dinucleotide phosphate, proline, spermidine, and alpha-hydroxyhippuric acid were identified as novel potential metabolite biomarkers of TCMR. Proline, spermidine, and GABA had the highest area under the curve (>0.7) and were overrepresented in the TCMR group. Nicotinate and nicotinamide metabolism was the most important pathway in TCMR. These findings call for clinical validation in larger study samples and suggest that urinary metabolomics warrants future consideration as a noninvasive research tool for TCMR diagnostic innovation.

Urinary biomarker panel for diagnosing patients with depression and anxiety disorders.

Available data indicate that patients with depression and anxiety disorders are likely to be at greater risk for suicide. Therefore, it is important to correctly diagnose patients with depression and anxiety disorders. However, there are still no empirical laboratory methods to objectively diagnose these patients. In this study, the multiple metabolomics platforms were used to profile the urine samples from 32 healthy controls and 32 patients with depression and anxiety disorders for identifying differential metabolites and potential biomarkers. Then, 16 healthy controls and 16 patients with depression and anxiety disorders were used to independently validate the diagnostic performance of the identified biomarkers. Finally, a panel consisting of four biomarkers-N-methylnicotinamide, aminomalonic acid, azelaic acid and hippuric acid-was identified. This panel was capable of distinguishing patients with depression and anxiety disorders from healthy controls with an area under the receiver operating characteristic curve of 0.977 in the training set and 0.934 in the testing set. Meanwhile, we found that these identified differential metabolites were mainly involved in three metabolic pathways and five molecular and cellular functions. Our results could lay the groundwork for future developing a urine-based diagnostic method for patients with depression and anxiety disorders.

LC-MS/MS assay for N1-methylnicotinamide in humans, an endogenous probe for renal transporters.

BACKGROUND: N1-methylnicotinamide (1-NMN) has been proposed as a potential clinical biomarker to assess drug-drug interactions involving organic cation transporters (OCT2) and multidrug and toxin extrusion protein transporters. RESULTS: A hydrophilic interaction liquid chromatography-MS/MS assay, to quantify 1-NMN, in human plasma and urine is reported. MATERIALS & METHODS: A hydrophilic interaction chromatography (HILIC)-tandem mass spectrometry (MS/MS) assay to quantify 1-NMN in human plasma and urine is reported. The basal 1-NMN levels in plasma and urine were 4-120 and 2000-15,000 ng/ml, respectively. CONCLUSION: 1-NMN plasma AUCs increased two- to fourfold versus placebo following the administration of a clinical candidate that in vitro experiments indicated was an OCT2 inhibitor. The described hydrophilic interaction liquid chromatography-MS/MS assay can be used to assess a clinical compound candidate for the inhibition of OCT2 and multidrug and toxin extrusion protein transporter in first-in-human studies.

Simultaneous determination of nine neonicotinoids in human urine using isotope-dilution ultra-performance liquid chromatography-tandem mass spectrometry.

Neonicotinoids (neonics), a class of systemic insecticides, have been frequently detected in pollen, vegetables, and fruits. Recently, an increasing concern has been aroused for human exposure to neonics. However, biological monitoring for quantifying body burden of neonics has rarely been reported. In this study, we developed an isotope-dilution ultra-high performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) method to simultaneously quantify nine neonics, including acetamiprid (ACE), thiamethoxam (THIAM), imidacloprid (IMIP), clothianidin (CLO), flonicamid (FLO), thiacloprid (THIAC), dinotefuran (DIN), nitenpyram (NIT), and imidaclothiz (IMIT) in urine. The limits of quantification were 0.1 µg/L for ACE, FLO, DIN, NIT and IMIT, and 0.2 µg/L for THIAM, IMIP, CLO, and THIAC. The overall recoveries were 80.8-103%, 81.5-91.7% and 83.0-92.3% for QA/QC samples fortifying at 1, 25, and 100 µg/L levels, respectively. UPLC/MS/MS method was used to analyze urine samples obtained from 10 children in Hangzhou, China. The detection frequencies were 80% for ACE and IMIP, 70% for THIAM and CLO, 20% for DIN and IMIT and 10% for THIAC. FLO and NIT were not detected in those urine samples. The data provided here will be helpful for conducting biological monitoring of neonics exposure in the future.

Oral Glucose Tolerance and Tryptophan Metabolism in Non-Obese and Non-Insulin-Dependent Diabetic Goto-Kakizaki Rats Fed High-Tryptophan Diets.

We investigated oral glucose tolerance and tryptophan (Trp) metabolism in non-obese and non-insulin-dependent diabetic Goto-Kakizaki (GK) rats fed high-Trp diets. Five-week-old male Wistar and GK rats were fed a 20% casein diet (control diet) or the same diet supplemented with 1%, 2%, 3%, or 5% Trp for 58 d. Oral glucose tolerance tests were performed on Days 14 and 28 of the experimental period. Urine as well as livers and blood were collected on the last day of the experiment. The glucose concentration and the amount of Trp metabolites were measured. On Day 14 of the experiment, the incremental blood glucose concentrations integrated over a period of 2 h (ΔAUC0-2h) of blood glucose in rats fed the 3% and 5% Trp diets had decreased by 13% and 18%, respectively, compared with that of the control-GK rats. However, no significant differences were found in the rats fed +1% or +2% Trp diets compared with control-GK rats. On Day 28, there were no significant differences found in the ΔAUC0-2h of blood glucose levels in any group including the control-GK group. On the last day, the concentrations of plasma glucose, total cholesterol, and triglyceride did not show differences in any group. There were no specific phenomena observed in the metabolism of Trp in GK rats even when fed an excess of Trp, compared with that of Wistar rats. Oral Trp administration and its continuous use may not improve blood glucose levels in type 2 diabetic rats.

Urinary Excretion of Niacin Metabolites in Humans After Coffee Consumption.

SCOPE: Coffee is a major natural source of niacin in the human diet, as it is formed during coffee roasting from the alkaloid trigonelline. The intention of our study was to monitor the urinary excretion of niacin metabolites after coffee consumption under controlled diet. METHODS AND RESULTS: We performed a 4-day human intervention study on the excretion of major niacin metabolites in the urine of volunteers after ingestion of 500 mL regular coffee containing 34.8 µmol nicotinic acid (NA) and 0.58 µmol nicotinamide (NAM). In addition to NA and NAM, the metabolites N1 -methylnicotinamide (NMNAM), N1 -methyl-2-pyridone-5-carboxamide (2-Py), and nicotinuric acid (NUA) were identified and quantified in the collected urine samples by stable isotope dilution analysis (SIVA) using HPLC-ESI-MS/MS. Rapid urinary excretion was observed for the main metabolites (NA, NAM, NMNAM, and 2-Py), with tmax values within the first hour after ingestion. NUA appeared in traces even more rapidly. In sum, 972 nmol h-1 of NA, NAM, NMNAM, and 2-Py were excreted within 12 h after coffee consumption, corresponding to 6% of the ingested NA and NAM. CONCLUSION: The results indicate regular coffee consumption to be a source of niacin in human diet.

Urine Metabonomics Reveals Early Biomarkers in Diabetic Cognitive Dysfunction.

Recently, increasing attention has been paid to diabetic encephalopathy, which is a frequent diabetic complication and affects nearly 30% of diabetics. Because cognitive dysfunction from diabetic encephalopathy might develop into irreversible dementia, early diagnosis and detection of this disease is of great significance for its prevention and treatment. This study is to investigate the early specific metabolites biomarkers in urine prior to the onset of diabetic cognitive dysfunction (DCD) by using metabolomics technology. An ultra-high performance liquid-chromatography-quadrupole time-of-flight-mass spectrometry (UPLC-Q/TOF-MS) platform was used to analyze the urine samples from diabetic mice that were associated with mild cognitive impairment (MCI) and nonassociated with MCI in the stage of diabetes (prior to the onset of DCD). We then screened and validated the early biomarkers using OPLS-DA model and support vector machine (SVM) method. Following multivariate statistical and integration analysis, we found that seven metabolites could be accepted as early biomarkers of DCD, and the SVM results showed that the prediction accuracy is as high as 91.66%. The identities of four biomarkers were determined by mass spectrometry. The identified biomarkers were largely involved in nicotinate and nicotinamide metabolism, glutathione metabolism, tryptophan metabolism, and sphingolipid metabolism. The present study first revealed reliable biomarkers for early diagnosis of DCD. It provides new insight and strategy for the early diagnosis and treatment of DCD.

Pregnancy Increases the Renal Secretion of N1-methylnicotinamide, an Endogenous Probe for Renal Cation Transporters, in Patients Prescribed Metformin.

N1-methylnicotinamide (1-NMN) has been investigated as an endogenous probe for the renal transporter activity of organic cation transporter 2 (OCT2) and multidrug and toxin extrusion proteins 1 and 2-K (MATE1 and MATE2-K). As pregnancy increased the renal secretion of metformin, a substrate for OCT2, MATE1, and MATE2-K, we hypothesized that the renal secretion of 1-NMN would be similarly affected. Blood and urine samples collected from women prescribed metformin for type 2 diabetes, gestational diabetes, and polycystic ovarian syndrome during early, mid, and late pregnancy (n = 34 visits) and postpartum (n = 14 visits) were analyzed for 1-NMN using liquid chromatography-mass spectrometry. The renal clearance and secretion clearance, using creatinine clearance to correct for glomerular filtration, were estimated for 1-NMN and correlated with metformin renal clearance. 1-NMN renal clearance was higher in both mid (504 ± 293 ml/min, P < 0.01) and late pregnancy (557 ± 305 ml/min, P < 0.01) compared with postpartum (240 ± 106 ml/min). The renal secretion of 1-NMN was 3.5-fold higher in mid pregnancy (269± 267, P < 0.05) and 4.5-fold higher in late pregnancy compared with postpartum (342 ± 283 versus 76 ± 92 ml/min, P < 0.01). Because creatinine is also a substrate of OCT2, MATE1, and MATE2-K, creatinine clearance likely overestimates filtration clearance, whereas the calculated 1-NMN secretion clearance is likely underestimated. Metformin renal clearance and 1-NMN renal clearance were positively correlated (rs = 0.68, P < 0.0001). 1-NMN renal clearance increases during pregnancy due to increased glomerular filtration and net secretion by renal transporters.

Ultrasound assisted combined molecularly imprinted polymer for selective extraction of nicotinamide in human urine and milk samples: Spectrophotometric determination and optimization study.

Ultrasound-assisted dispersive solid phase microextraction followed by UV-vis spectrophotometer (UA-DSPME-UV-vis) was designed for extraction and preconcentration of nicotinamide (vitamin B3) by HKUST-1 metal organic framework (MOF) based molecularly imprinted polymer (MIP). This new material was characterized by FTIR and FE-SEM techniques. The preliminary Plackett-Burman design was used for screening and subsequently the central composite design justifies significant terms and possible construction of mathematical equation which give the individual and cooperative contribution of variables like HKUST-1-MOF-NA-MIP mass, sonication time, temperature, eluent volume, pH and vortex time. Accordingly the optimum condition was set as: 2.0mg HKUST-1-MOF-NA-MIP, 200µL eluent and 5.0min sonication time in center points other variables were determined as the best conditions to reach the maximum recovery of the analyte. The UA-DSPME-UV-vis method performances like excellent linearity (LR), limits of detection (LOD), limits of quantification of 10-5000µgL-1 with R2 of 0.99, LOD (1.96ngmL-1), LOQ (6.53µgL-1), respectively show successful and accurate applicability of the present method for monitoring analytes with within- and between-day precision of 0.96-3.38%. The average absolute recoveries of the nicotinamide extracted from the urine, milk and water samples were 95.85-101.27%.

Pimasertib, a selective oral MEK1/2 inhibitor: absolute bioavailability, mass balance, elimination route, and metabolite profile in cancer patients.

AIM: This trial (NCT: 01713036) investigated the absolute bioavailability, mass balance and metabolite profile of pimasertib in a new design combining these investigations in a single group of patients. METHODS: Six male patients with pathologically confirmed, locally advanced or metastatic solid tumours were enrolled. Exclusion criteria included Eastern Cooperative Oncology Group performance status >1. In Part A of the trial, patients received a 60 mg oral dose of unlabelled pimasertib followed by an intravenous (i.v.) tracer dose of [14 C]pimasertib 2 µg (equalling 9 kBq) as a bolus injection, one hour after the oral dose, on Day 1. On Day 8, all patients received 60 mg pimasertib capsules spiked with 2.6 MBq of [14 C]pimasertib. Patients received 60 mg oral unlabelled pimasertib twice daily from Day 3 to Day 21 of Part A and in subsequent 21-day cycles in Part B. RESULTS: Following i.v. administration, [14 C]pimasertib exhibited a geometric mean total body clearance of 45.7 l h-1 (geometric coefficient of variation [geometric CV]: 47.2%) and a volume of distribution of 229 l (geometric CV: 42.0%). Absolute bioavailability was 73%. The majority of the oral [14 C] dose (85.1%) was recovered in excreta. Total radioactivity was mainly excreted into urine (52.8%) and faeces (30.7%) with 78.9% of the [14 C] dose recovered as metabolites. Two major circulating metabolites were identified in plasma: a carboxylic acid (M445) and a phosphoethanolamine conjugate (M554). The safety profile was in line with the published pimasertib trials. CONCLUSION: Pimasertib showed a favourable pharmacokinetic profile with high absolute bioavailability and a unique metabolic pathway (conjugation with phosphoethanolamine).

Urinary N-methylnicotinamide and ß-aminoisobutyric acid predict catch-up growth in undernourished Brazilian children.

Enteric infections, enteropathy and undernutrition in early childhood are preventable risk factors for child deaths, impaired neurodevelopment, and later life metabolic diseases. However, the mechanisms linking these exposures and outcomes remain to be elucidated, as do biomarkers for identifying children at risk. By examining the urinary metabolic phenotypes of nourished and undernourished children participating in a case-control study in Semi-Arid Brazil, we identified key differences with potential relevance to mechanisms, biomarkers and outcomes. Undernutrition was found to perturb several biochemical pathways, including choline and tryptophan metabolism, while also increasing the proteolytic activity of the gut microbiome. Furthermore, a metabolic adaptation was observed in the undernourished children to reduce energy expenditure, reflected by increased N-methylnicotinamide and reduced ß-aminoisobutyric acid excretion. Interestingly, accelerated catch-up growth was observed in those undernourished children displaying a more robust metabolic adaptation several months earlier. Hence, urinary N-methylnicotinamide and ß-aminoisobutyric acid represent promising biomarkers for predicting short-term growth outcomes in undernourished children and for identifying children destined for further growth shortfalls. These findings have important implications for understanding contributors to long-term sequelae of early undernutrition, including cognitive, growth, and metabolic functions.

Niacin (Vitamin B3) Supplementation in Patients with Serotonin-Producing Neuroendocrine Tumor.

BACKGROUND/AIMS: Tryptophan is the precursor of serotonin and niacin (vitamin B3). The latter is critical for normal cellular metabolism. Tryptophan and niacin can be deficient in patients with serotonin-producing neuroendocrine tumors (NETs). Niacin deficiency may lead to severe symptoms including pellagra. In patients with serotonin-producing NET, data on niacin status are scarce and niacin supplementation hardly receives attention. We aimed to assess the niacin status before and after supplementation in these patients. METHODS: We identified serotonin-producing NET patients who had received oral niacin supplementation (mean dose 144 mg daily) for tryptophan deficiency and/or pellagra-associated symptoms. Presupplementation plasma tryptophan levels and niacin status based on the urinary niacin metabolite N1-methylnicotinamide (N1-MN) before (n = 42) and after the start of the supplementation (in 34 paired samples) were assessed. Reference values for urinary N1-MN levels were established in 133 healthy individuals. RESULTS: The mean presupplementation plasma tryptophan level was 31.8 ± 9.7 µmol/l (reference value 40.0-70.0). Presupplementation urinary N1-MN levels were lower in patients (median 17.9 µmol/24 h, range 2.6-70.3) compared to healthy controls (median 43.7 µmol/24 h, range 9.5-169.3, p < 0.0001) and below normal in 45% of the patients. Niacin supplementation increased urinary N1-MN levels to high normal levels (median 55.5 µmol/24 h, range 7.4-489.0) in 86% of the niacin-deficient patients. CONCLUSION: In serotonin-producing NET patients, niacin deficiency is prevalent. Therefore, urinary N1-MN deserves to be included in their standard biochemical evaluation. Niacin supplementation normalizes the niacin status in most niacin-deficient serotonin-producing NET patients. A prospective study is warranted.

Validation of a multi-analyte HPLC-DAD method for determination of uric acid, creatinine, homovanillic acid, niacinamide, hippuric acid, indole-3-acetic acid and 2-methylhippuric acid in human urine.

During the last decades exposure sciences and epidemiological studies attracts more attention to unravel the mechanisms for the development of chronic diseases. According to this an existing HPLC-DAD method for determination of creatinine in urine samples was expended for seven analytes and validated. Creatinine, uric acid, homovanillic acid, niacinamide, hippuric acid, indole-3-acetic acid, and 2-methylhippuric acid were separated by gradient elution (formate buffer/methanol) using an Eclipse Plus C18 Rapid Resolution column (4.6mm×100mm). No interfering signals were detected in mobile phase. After injection of blank urine samples signals for the endogenous compounds but no interferences were detected. All analytes were linear in the selected calibration range and a non weighted calibration model was chosen. Bias, intra-day and inter-day precision for all analytes were below 20% for quality control (QC) low and below 10% for QC medium and high. The limits of quantification in mobile phase were in line with reported reference values but had to be adjusted in urine for homovanillic acid (45mg/L), niacinamide 58.5(mg/L), and indole-3-acetic acid (63mg/L). Comparison of creatinine data obtained by the existing method with those of the developed method showing differences from -120mg/L to +110mg/L with a mean of differences of 29.0mg/L for 50 authentic urine samples. Analyzing 50 authentic urine samples, uric acid, creatinine, hippuric acid, and 2-methylhippuric acid were detected in (nearly) all samples. However, homovanillic acid was detected in 40%, niacinamide in 4% and indole-3-acetic acid was never detected within the selected samples.

Niacin metabolism and indoleamine 2,3-dioxygenase activation in malnourished patients with flaky paint dermatosis.

Flaky paint dermatosis, characterized by extensive, often bilateral areas of flaking and pigmentation, mostly in sun unexposed areas is considered a feature of kwashiorkor in both children and adults, and must be differentiated from other dermatosis, including chapped and xerotica skin, and pellagra. In this case series we provide evidence that malnourished patients with flaky paint dermatosis and infection/inflammation shown laboratory data suggestive of indoleamine 2,3-dioxygenase (IDO) activation, besides decreased urinary excretion of N1-methylnicotinamide (N1 MN), a marker of pellagra. We study nine adult patients showing flaky paint dermatosis and clinical features of infection or inflammation, and increased serum C-reactive protein, characteristic of the presence of acute phase response syndrome. As a group, they had low or deficient urinary N1 MN excretion (0.52 ± 0.39 mg/g creatinine) compatible with pellagra. They also showed low serum tryptophan levels (<29 µmol/L) and a serum kynurenine/tryptophan ratio higher than 0.04, suggesting increased IDO expression and increase in the tryptophan oxidation. Findings suggest that some patients with flaky paint dermatosis showed laboratory data suggestive of IDO activation, besides decreased N1 MN urinary excretion. Taken together, the data support the idea that flaky paint dermatosis could be a skin manifestation of niacin deficiency.

N(1)-methylnicotinamide as an endogenous probe for drug interactions by renal cation transporters: studies on the metformin-trimethoprim interaction.

PURPOSE: N(1)-methylnicotinamide (NMN) was proposed as an in vivo probe for drug interactions involving renal cation transporters, which, for example, transport the oral antidiabetic drug metformin, based on a study with the inhibitor pyrimethamine. The role of NMN for predicting other interactions with involvement of renal cation transporters (organic cation transporter 2, OCT2; multidrug and toxin extrusion proteins 1 and 2-K, MATE1 and MATE2-K) is unclear. METHODS: We determined inhibition of metformin or NMN transport by trimethoprim using cell lines expressing OCT2, MATE1, or MATE2-K. Moreover, a randomized, open-label, two-phase crossover study was performed in 12 healthy volunteers. In each phase, 850 mg metformin hydrochloride was administered p.o. in the evening of day 4 and in the morning of day 5. In phase B, 200 mg trimethoprim was administered additionally p.o. twice daily for 5 days. Metformin pharmacokinetics and effects (measured by OGTT) and NMN pharmacokinetics were determined. RESULTS: Trimethoprim inhibited metformin transport with K i values of 27.2, 6.3, and 28.9 µM and NMN transport with IC50 values of 133.9, 29.1, and 0.61 µM for OCT2, MATE1, and MATE2-K, respectively. In the clinical study, trimethoprim increased metformin area under the plasma concentration-time curve (AUC) by 29.5 % and decreased metformin and NMN renal clearances by 26.4 and 19.9 %, respectively (p ≤ 0.01). Moreover, decreases of NMN and metformin renal clearances due to trimethoprim correlated significantly (r S=0.727, p=0.010). CONCLUSIONS: These data on the metformin-trimethoprim interaction support the potential utility of N(1)-methylnicotinamide as an endogenous probe for renal drug-drug interactions with involvement of renal cation transporters.

Sex-specific urinary biomarkers for diagnosing bipolar disorder.

Sex-based differences are prominent in affective disorders, but there are no biomarkers available to support sex-specific, laboratory-based diagnostics for male and female bipolar disorder (BD) patients. Here, a NMR-based metabonomic approach was used to preliminarily identify sex-specific urinary metabolite biomarkers for diagnosing male and female BD patients. A male-specific biomarker panel consisting of four metabolites (α-hydroxybutyrate, choline, formate, and N-methylnicotinamide) effectively discriminated between male BD and healthy controls (HC) subjects, achieving an area under the receiver operating characteristic curve (AUC) of 0.942. A female-specific biomarkers panel consisting of four metabolites (α-hydroxybutyrate, oxalacetate, acetone, and N-methylnicotinamide) effectively discriminated between female BD and HC subjects, achieving an AUC of 0.909. The male-specific biomarker panel displayed low discriminatory power in the female group, and the female-specific biomarker panel displayed low discriminatory power in the male group. Moreover, several other metabolites showed different trends between male and female BD subjects. These findings suggest that male and female BD patients have distinct biomarker fingerprints and that these two sex-specific biomarker panels may serve as effective diagnostic tools in distinguishing male and female BD patients from their healthy counterparts. Our work may provide a window into the mechanisms underlying the pathoetiology of BD in both men and women.