MG-HCr, the Methylglyoxal-Derived Hydroimidazolone of Creatine, a Biomarker for the Dietary Intake of Animal Source Food

In the course of the Maillard reaction in vivo or in food, creatine reacts with the 1,2-dicarbonyl compound methylglyoxal to N-(4-methyl-5-oxo-1-imidazolin-2-yl)sarcosine (MG-HCr). We studied whether the urinary excretion of MG-HCr is affected by its intake with meat or by the intake of creatine and subsequent in vivo formation of MG-HCr. Therefore, 24 h urine of 30 subjects with different dietary habits was analyzed with HPLC-MS/MS. The daily MG-HCr excretion via urine varied between omnivores (0.39-9.67 μmol/day, n = 24), vegetarians (0.18-0.97 μmol/day, n = 19), and vegans (0.10-0.27 μmol/day, n = 8). An intervention study with 18 subjects demonstrated the bioavailability of MG-HCr (ca. 54%) from 200 g of heated meat and its quick excretion with urine. A creatine intervention of 0.44 g did not increase MG-HCr excretion. Thus, the differences in MG-HCr excretion between different diets are mainly caused by the dietary uptake of MG-HCr. We additionally found MG-HCr in milk and egg products, where it is formed during heat treatment. This partly explains differences in MG-HCr excretion of vegetarians and vegans. Hence, MG-HCr in urine is a short-term marker for the intake of heat-processed animal source food.

Comparative study of six sequential spectrophotometric methods for quantification and separation of ribavirin, sofosbuvir and daclatasvir: An application on Laboratory prepared mixture, pharmaceutical preparations, spiked human urine, spiked human plasma, and dissolution test

In accordance with International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) guidelines, six novel, simple and precise sequential spectrophotometric methods were developed and validated for the simultaneous analysis of Ribavirin (RIB), Sofosbuvir (SOF), and Daclatasvir (DAC) in their mixture without prior separation steps. These drugs are described as co-administered for treatment of Hepatitis C virus (HCV). HCV is the cause of hepatitis C and some cancers such as liver cancer (hepatocellular carcinoma) and lymphomas in humans. These techniques consisted of several sequential steps using zero, ratio and/or derivative spectra. DAC was first determined through direct spectrophotometry at 313.7 nm without any interference of the other two drugs while RIB and SOF can be determined after ratio subtraction through five methods; Ratio difference spectrophotometric method, successive derivative ratio method, constant center, isoabsorptive method at 238.8 nm, and mean centering of the ratio spectra (MCR) at 224 nm and 258 nm for RIB and SOF, respectively. The calibration curve is linear over the concentration ranges of (6-42), (10-70) and (4-16) μg/mL for RIB, SOF, and DAC, respectively. This method was successfully applied to commercial pharmaceutical preparation of the drugs, spiked human urine, and spiked human plasma. The above methods are very simple methods that were developed for the simultaneous determination of binary and ternary mixtures and so enhance signal-to-noise ratio. The method has been successfully applied to the simultaneous analysis of RIB, SOF, and DAC in laboratory prepared mixtures. The obtained results are statistically compared with those obtained by the official or reported methods, showing no significant difference with respect to accuracy and precision at p = 0.05.

Concentrations of selected heterocyclic aromatic amines among US population aged ≥ 6 years: data from NHANES 2013-2014

Data from National Health and Nutrition Examination Survey for US population aged ≥ 6 years for 2013-2014 were used to analyze data for four heterocyclic aromatic amines (HCAA), namely 2-amino-9H-pyrido[2,3-b]indole (AαC), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhlP), harman, and norharman. Data were analyzed separately for children aged 6-11 years (N = 416), adolescents aged 12-19 years (N = 475), adults aged 20-64 years (N = 1913), and seniors aged ≥ 65 years (N = 458). Adult males had lower concentrations of AαC and harman than adult females (1.44 vs. 2.22 pg/mL for AαC, p < 0.01 and 136.8 vs. 163.2 pg/mL for harman, p = 0.04). Racial/ethnic differences were observed in the adjusted concentrations of HCAAs. For adults, adjusted concentrations of HCAAs were lower for non-Hispanic Asians and Hispanics as compared to non-Hispanic blacks and whites. For example for AαC, the adjusted concentrations for non-Hispanic Asians, Hispanics, non-Hispanic blacks and whites were 1.16, 2.00, 2.37, and 2.16 pg/mL respectively. Adjusted concentrations of AαC were found to be lower among nonsmokers as compared to smokers for adolescents (0.34 vs. 1.32 pg/mL, p < 0.01), adults (0.40 vs. 7.91 pg/mL, p < 0.01), and seniors (0.30 vs. 4.29 pg/mL, p < 0.01). For both harman and norharman, adult nonsmokers had lower adjusted concentrations than smokers (125.7 vs. 177.6 pg/mL, p < 0.01 for harman, 296.1 vs. 421.6 pg/mL, p < 001, for norharman). Exposure to environmental tobacco smoke was found to be associated with higher concentrations of AαC among adolescents (p = 0.01) and adults (p = 0.01) and for harman (p = 0.01) and norharman (p = 0.01) among seniors. In conclusion, concentrations of selected HCAAs can be several fold higher among smokers as compared to nonsmokers and gender as well as race/ethnicity also affect the observed concentrations of HCAA.

Biological Monitoring of Human Exposure to Neonicotinoids Using Urine Samples, and Neonicotinoid Excretion Kinetics

BACKGROUND

Neonicotinoids, which are novel pesticides, have entered into usage around the world because they are selectively toxic to arthropods and relatively non-toxic to vertebrates. It has been suggested that several neonicotinoids cause neurodevelopmental toxicity in mammals. The aim was to establish the relationship between oral intake and urinary excretion of neonicotinoids by humans to facilitate biological monitoring, and to estimate dietary neonicotinoid intakes by Japanese adults.

METHODOLOGY/PRINCIPAL FINDINGS

Deuterium-labeled neonicotinoid (acetamiprid, clothianidin, dinotefuran, and imidacloprid) microdoses were orally ingested by nine healthy adults, and 24 h pooled urine samples were collected for 4 consecutive days after dosing. The excretion kinetics were modeled using one- and two-compartment models, then validated in a non-deuterium-labeled neonicotinoid microdose study involving 12 healthy adults. Increased urinary concentrations of labeled neonicotinoids were observed after dosing. Clothianidin was recovered unchanged within 3 days, and most dinotefuran was recovered unchanged within 1 day. Around 10% of the imidacloprid dose was excreted unchanged. Most of the acetamiprid was metabolized to desmethyl-acetamiprid. Spot urine samples from 373 Japanese adults were analyzed for neonicotinoids, and daily intakes were estimated. The estimated average daily intake of these neonicotinoids was 0.53-3.66 μg/day. The highest intake of any of the neonicotinoids in the study population was 64.5 μg/day for dinotefuran, and this was <1% of the acceptable daily intake.

[Biomonitoring in workers exposed to pesticides: development and application of method detecting imidacloprid in urine]

Imidacloprid is a relatively new insecticide in neonicotinoids chemical class with neuroactivity in insects, being one of the most widely used insecticides in the world. For biomonitoring in workers exposed to pesticides, the authors designed a method detecting low levels of Imidacloprid in urine of operators, based on tandem liquid mass-spectrometry with ionization source--electrostatic dispersion (positive ionization) in multi-reaction monitoring regime with subsidiary ion (mass/charge) 209 for quantitative assessment and ion 175.1 for confirmation onion ratio. The study incorporated diurnal urine, about 100 ml of average sample was frozen and kept at temperature -20C for analysis. Before extraction, the sample was unfrozen, an aliquot of 5 ml was selected, diluted with 5 ml of 0.1% formic acid. The substance was concentrated out of the urine samples via solid-phase extraction with application of cartridges based on octadecylsilane, eluition--1 ml of methanol. Lower limit of Imidacloprid detection in urine is 0.02 ng/ml, of the quantitative assessment--0.1 ng/ ml, linear range of concentrations measured 0.1-10 ng/ml. The method was tested for monitoring in workers exposed to Imidacloprid preparations in natural conditions of pesticides application in agriculture, with various processing technologies. Imidacloprid was identified in urine of two professional operators after work in seed treatment and the subsequent seeding at lower limit of detection (0.02 ng/ml) and 0.34 ng/ml.

Histidine decarboxylase and urinary methylimidazoleacetic acid in gastric neuroendocrine cells and tumours

AIM: To study histidine decarboxylase (HDC) expression in normal and neoplastic gastric neuroendocrine cells in relationship to the main histamine metabolite.

METHODS: Control tissues from fundus (n = 3) and corpus (n = 3) mucosa of six patients undergoing operations for gastric adenocarcinoma, biopsy and/or gastric surgical specimens from 64 patients with primary gastric neuroendocrine tumours (GNETs), as well as metastases from 22 of these patients, were investigated using conventional immunohistochemistry and double immunofluorescence with commercial antibodies vs vesicular monoamine transporter 2 (VMAT-2), HDC and ghrelin. The urinary excretion of the main histamine metabolite methylimidazoleacetic acid (U-MeImAA) was determined using high-performance liquid chromatography in 27 of the 64 patients.

RESULTS: In the gastric mucosa of the control tissues, co-localization studies identified neuroendocrine cells that showed immunoreactivity only to VMAT-2 and others with reactivity only to HDC. A third cell population co-expressed both antigens. There was no co-expression of HDC and ghrelin. Similar results were obtained in the foci of neuroendocrine cell hyperplasia associated with chronic atrophic gastritis type A and also in the tumours. The relative incidence of the three aforementioned markers varied in the tumours that were examined using conventional immunohistochemistry. All of these GNETs revealed both VMAT-2 and HDC immunoreactivity, and their metastases showed an immunohistochemical pattern and frequency similar to that of their primary tumours. In four patients, increased U-MeImAA excretion was detected, but only two of the patients exhibited related endocrine symptoms.

CONCLUSION: Human enterochromaffin-like cells appear to partially co-express VMAT-2 and HDC. Co-expression of VMAT-2 and HDC might be required for increased histamine production in patients with GNETs.

Temporal Levels of Urinary Neonicotinoid and Dialkylphosphate Concentrations in Japanese Women Between 1994 and 2011

Over the last two decades, usage of neonicotinoid (NEO) insecticides has increased due to their high selectivity for insects versus mammals and their effectiveness for extermination of insects resistant to conventional pesticides such as pyrethroids and organophosphates (OPs). However, historical change of the NEO exposure level in humans is poorly understood. The aim of this study is to reveal changes in the levels of NEO and OP exposure in the human body over the last two decades using biomonitoring technique. We quantified urinary concentrations of 7 NEOs (acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, thiacloprid, and thiamethoxam) and 4 metabolites of OPs (dimethylphosphate, dimethylthiophosphate, diethylphosphate, and diethylthiophosphate) in 95 adult females aged 45-75 in 1994, 2000, 2003, 2009, and 2011 (n = 17-20 different individuals in each year). The results show that the detection rates of urinary NEOs in Japanese women increased significantly between 1994 and 2011, suggesting that intakes of NEOs into the human body rose during that period. In contrast, exposure to OPs having O,O-dimethyl moieties decreased steadily according to a finding that geometric means of urinary dimethylphosphate concentrations kept diminishing considerably. These changes may reflect the amounts of NEOs and OPs used as insecticides in Japan.

Occurrence and Profile Characteristics of the Pesticide Imidacloprid, Preservative Parabens, and Their Metabolites in Human Urine from Rural and Urban China

Knowledge of human exposure to imidacloprid, the most extensively used insecticide, and para-hydroxybenzoic acid esters (parabens), the most extensively used preservative, is insufficient. In this study, 295 urine samples collected from subjects in rural and urban areas in China were analyzed for imidacloprid and four parabens (namely, methyl paraben, ethyl paraben, propyl paraben, and butyl paraben) as well as their major metabolites (namely, 6-chloronicotinic acid (6-ClNA) and para-hydroxybenzoic acid (p-HB)). Imidacloprid was detected in 100% of the urine samples from rural Chinese subjects and 95% of the urine samples from urban Chinese subjects. Concentrations of urinary imidacloprid detected in rural Chinese subjects (geometric mean (GM) = 0.18 ng/mL) were slightly higher than those detected in urban Chinese subjects (GM = 0.15 ng/mL) when the effect of pesticide spraying was excluded. However, concentrations of urinary imidacloprid detected in rural adults increased significantly in the subsequent days of pesticide spraying (GM = 0.62 ng/mL), which could return to the normal levels within 3 days. In contrast, concentrations of urinary parabens detected in rural Chinese subjects (GM = 6.90 ng/mL) were lower than that in urban Chinese subjects (GM = 30.5 ng/mL). In addition, the metabolism characteristics of imidacloprid to 6-ClNA and parabens to p-HB were discussed preliminarily.

LC-MS-MS Analysis of Urinary Biomarkers of Imazalil Following Experimental Exposures

Imazalil (IMZ) is a fungicide used in the cultivation of vegetables, such as cucumbers, in green houses or post-harvest on fruit to avoid spoilage due to fungal growth. Agricultural workers can be occupationally exposed to IMZ and the general public indirectly by the diet. The purpose of this study was to develop and validate an LC-MS-MS method for the analysis of IMZ in human urine. The method used electrospray ionization and selected reaction monitoring in the positive mode. Excellent linearity was observed in the range 0.5-100 ng/mL. The limit of detection of the method was 0.2 ng/mL, and the limit of quantitation 0.8 ng/mL. The method showed good within-run, between-run and between-batch precision, with a coefficient of variation <15%. The method was applied to analyze urine samples obtained from two human volunteers following experimental oral and dermal exposure. The excretion of IMZ seemed to follow a two-compartment model and first-order kinetics. In the oral exposure, the elimination half-life of IMZ in the rapid excretion phase was 2.6 and 1.9 h for the female and the male volunteer, respectively. In the slower excretion phase, it was 7.6 and 13 h, respectively. In the dermal exposure, the excretion seemed to follow a single-compartment model and first-order kinetics. The elimination half-life was 10 and 6.6 h for the female and the male volunteer, respectively. Although the study is limited to two volunteers, some information on basic toxicokinetics and metabolism of IMZ in humans is presented.

A quantitative LC/MS method targeting urinary 1-methyl-4-imidazoleacetic acid for safety monitoring of the global histamine turnover in clinical studies

Anaphylaxis is a potentially life-threatening condition triggered mainly by the release of inflammatory mediators, notably histamine. In pharmaceutical research, drug discovery, and clinical evaluation, it may be necessary to accurately assess the potential of a compound, event, or disorder to promote the release of histamine. In contrast to the measurement of plasma histamine, determination of the stable metabolite 1-methyl-4-imidazoleacetic acid (tele-MIAA) in urine provides a noninvasive and more reliable methodology to monitor histamine release. This study presents a repeatable high-performance liquid chromatography coupled to electrospray mass spectrometry (LC-ESI-MS) method where tele-MIAA is baseline separated from its structural isomer 1-methyl-5-imidazoleacetic acid (pi-MIAA) and an unknown in human urine. The ion-pairing chromatography method, in reversed-phase mode, based on 0.5 mM tridecafluoroheptanoic acid demonstrated high repeatability and was applied in a clinical development program that comprised a large number of clinical samples from different cohorts. The inter- and intra-run precision of the method for tele-MIAA were 8.4 and 4.3%, respectively, at the mean urinary concentration level, while method accuracy was between -16.2 and 8.0% across the linear concentration range of 22-1,111 ng mL(-1). Overall, method precision was greater than that reported in previously published methods and enabled the identification of gender differences that were independent of age or demography. The median concentration measured in female subjects was 3.0 μmol mmol(-1) of creatinine, and for male subjects, it was 2.1 μmol mmol(-1) of creatinine. The results demonstrate that the method provides unprecedented accuracy, precision, and practicality for the measurement of tele-MIAA in large clinical settings.

Development and application of LC–APCI–MS method for biomonitoring of animal and human exposure to imidacloprid

Imidacloprid (IMI) is a relatively new neuro-active neonicotinoid insecticide and nowadays one of the largest selling insecticides worldwide. In the present study a LC–APCI–MS based method was developed and validated for the quantification of imidacloprid and its main metabolite 6-chloronicotinic acid (6- CINA) in urine and hair specimens. The method was tested in biomonitoring of intentionally exposed animals and subsequently applied for biomonitoring of Cretan urban and rural population. The developed analytical method comprises two main steps of analytes isolation from specimen (solid– liquid extraction with methanol for hair, liquid–liquid extraction with methanol for urine) and subsequent instrumental analysis by LC–APCI–MS. The developed method was applied for the monitoring of IMI and 6-ClNA in hair and urine of laboratory animals (rabbits) intentionally fed with insecticide at low or high doses (40 and 80 mg kg(-1) weight d(-1) respectively) for 24 weeks. The analytes were detected in the regularly acquired hair and urine specimens and their found levels were proportional to the feeding dose and time of exposure with the exception of slight decline of IMI levels in high dose fed rabbits after 24 weeks of feeding. This decline can be explained by the induction of IMI metabolizing enzymes by the substrate. After testing on animal models the method was applied for pilot biomonitoring of Crete urban (n = 26) and rural (n = 32) population. Rural but not urban population is exposed to IMI with 21 positive samples (65.6%) and found median concentration 0.03 ng mg(-1). Maximum concentration detected was 27 ng mg(-1)

Pharmacokinetics of CS-866, a New Angiotensin II Receptor Blocker, in Healthy Subjects

CS-866, a novel angiotensin II receptor blocker, is rapidly and completely metabolized to RNH-6270, its active metabolite. The pharmacokinetics of RNH-6270 following oral CS-866 or intravenous RNH-6270 administration was determined in 104 healthy male volunteers. The pharmacokinetics of RNH-6270 was linear over dose ranges of 1 to 32 mg (intravenous RNH-6270 administration) and 10 to 160 mg (oral CS-866 administration). The time to maximum plasma concentration of RNH-6270 after oral CS-866 administration ranged from 1.4 to 2.8 hours, and the terminal elimination half-life ranged from 12 to 18 hours. Absolute bioavailability of RNH-6270 after oral administration of CS-866 was 26%. Administration of CS-866 once daily for 10 days did not result in drug accumulation. When administered intravenously, RNH-6270 has a volume of distribution of 15 to 25 L. Approximately 35% to 50% of RNH-6270 is excreted unchanged in the urine. CS-866 was safe and well tolerated at doses of up to 160 mg/day.

[Relationship between warfarin dosing and activity of CYP2C9 assessed by the content of losartan and its metabolite E-3174 in the urine of patients with mechanical prosthetic heart valves]

We evaluated effect of activity of cytochrome P450 CYP2C9 on maintenance doses of warfarin in 33 patients with implanted artificial heart valves. Losartan test was used for measurement of concentration of active metabolite E-3174 in urine. Concentration of E-3174 below 2500 ng/ml in patients with genotype CYP2C981/*1 with sensitivity 87% and specificity 66% predicted requirement of low doses (< 5 mg/day) of warfarin in the late postoperative period (odds ratio 14, 95% confidence interval 1.135 to 172.75).

Impact of aqueous doash extract on urinary mutagenicity in rats exposed to heterocyclic amines

Doash (Origanum majorana) is an herbaceous plant found commonly in Saudi Arabia. It is used as a food flavor and a folk remedy to treat a number of diseases. The 2-amino-3-methylimidazo[4,5-f] quinoline (IQ) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) are the most abundant of the heterocyclic amine carcinogens present in cooked food. In the present study, the potential of doash tea to influence carcinogen metabolism was investigated indirectly using heterocyclic amines as model mutagens, IQ and PhIP. Results obtained showed that doash tea had no influence on body weight in both the studies. Rats were treated with different doses of IQ (1, 3, 5 and 10 mg/kg) or PhIP (1, 5, 10 and 20 mg/kg). The selected dosage was 5 mg/kg for both heterocyclic amines. Results obtained revealed that rats treated with doash tea and given a single dose of the heterocyclic amines, whether for 1 day (short-term) or for 1 month (long term), showed a statistically significant decrease in their excretion of indirect mutagens (IQ or PhIP). Following treatment of the rats with a single oral dose of IQ or PhIP, the highest mutagenic activity determined in the presence of an activation system was excreted in the urine after 24 h, with much lower levels of mutagencity being excreted during subsequent elimination from the body. No mutagenicity was observed in the absence of an activation system that is direct-acting mutagenicity using (IQ and PhIP). Statistical analysis revealed that, in comparison with the control group, the aqueous doash extract significantly reduced the mutagenic response after 24 h. It was concluded that doash extract significantly decreased the excretion of mutagens in comparison with the control group (water only).

A gas chromatography/mass spectrometry method for the determination of sildenafil, vardenafil and tadalafil and their metabolites in human urine

Sildenafil (SDF), vardenafil (VDF) and tadalafil (TDF) are phosphodiesterase type 5 enzyme inhibitors (PDE5Is), used in the treatment of erectile disorders and to improve breathing efficiency in pulmonary hypertension. The increasing incidence of their use among young athletes has drawn the attention of the anti-doping authorities to the possible abuse of PDE5Is by athletes due to their pharmacological activities. This paper describes a method for the determination in urine of PDE5Is and their metabolites by gas chromatography/mass spectrometry (GC/MS) after liquid/liquid extraction of the analytes from urine and derivatisation to obtain trimethylsilyl derivatives. The metabolic profile was studied on real samples collected from subjects taking PDE5Is (Viagra, Levitra or Cialis); the main urinary metabolites were identified and their MS fragmentation characterized. The sample pre-treatment and GC/MS conditions for the detection of the metabolites have been optimised. A method for their preliminary screening and subsequent confirmation is described that takes into account the general requirements of a routine doping analysis to be used for the screening of large numbers of samples. The main metabolites identified can be included in a general purpose screening method and all the metabolites in a more specific confirmation method. The method developed has been applied for the screening of PDE5Is in 5000 urine samples. Based on the obtained results, the proposed method appears to be of practical use in analytical and forensic toxicology, including doping analysis.

Tobacco smoking and urinary levels of 2-amino-9H-pyrido[2,3-b]indole in men of Shanghai, China

Carcinogenic heterocyclic aromatic amines (HAA) are formed in cooked meats, poultry, and fish and arise in tobacco smoke. We measured the concentrations of four prevalent HAAs in spot urine samples collected at baseline from 170 participants of the Shanghai Cohort study, a population-based cohort study of adult men recruited during 1986 to 1989 in Shanghai, China. Sixteen (18.6%) of 86 nonsmokers were positive for urinary 2-amino-9H-pyrido[2,3-b]indole (AalphaC) versus 41 (48.8%) of 84 cigarette smokers; the difference was statistically significant (P < 0.001). The number of cigarettes smoked per day was positively and significantly related to urinary levels of AalphaC in study subjects (P < 0.001); the mean level among nonsmokers was 2.54 ng/g creatinine, whereas the means for light (1-19 cigarettes per day) and heavy (20+ cigarettes per day) smokers were 7.50 and 11.92 ng/g creatinine, respectively. 2-Amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline was undetected in the urine of the 170 subjects. Only 5 (2.9%) and 6 (3.5%) subjects, respectively, showed detectable levels of urinary 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline, and smoking status was unrelated to levels of either HAA. Quantitative measurements of HAAs in commonly eaten pork and chicken dishes in Shanghai showed low concentrations of HAAs (<1 ng/g meat). Our data indicate that AalphaC represents a major HAA exposure in adult men of Shanghai, China, and that tobacco smoke is an important point source of their AalphaC exposure.

Pharmacokinetics and urinary excretion of eprosartan in Chinese healthy volunteers of different gender

The study aims to evaluate the pharmacokinetics and urinary excretion of eprosartan in Chinese healthy volunteers and to study the effect of gender on pharmacokinetics of eprosartan. Twenty healthy volunteers (ten men and ten women) were recruited for an open trial and received a single dose of 600 mg eprosartan. Using a validated LC/MS/MS method, plasma and urinary concentrations of eprosartan were determined. The following pharmacokinetic parameters were elucidated after administration: the area under the plasma concentration versus time curve from 0 to 32 h (AUC0-32h) 14818.75 +/- 7312.11 ng x h/mL, the area under the plasma concentration versus time curve from 0 to infinite (AUC(0-infinity)) 15081.62 +/- 7379.63 ng x h/mL, peak plasma concentration (Cmax) 3664.25 x 1653.94 ng x h/mL, time to Cmax (Tmax) 1.63 +/- 0.46 h, elimination half-life (t(1/2)) 8.03 +/- 4.04 h, apparent clearance (CL/F) 47.84 +/- 19.21 L/h, apparent volume of distribution of the central compartment (V/F) 537.21 +/- 287.91 L, renal clearance (CLr) 1.33 +/- 0.41 L/h, amount of unchanged eprosartan excreted into urine 18.44 +/- 6.43 mg and fraction of unchanged eprosartan excreted into urine 3.07 +/- 1.07%. Our results also indicated that no gender differences were observed in the pharmacokinetics of eprosartan in Chinese healthy volunteers.

Quantitative determination of olmesartan in human plasma and urine by liquid chromatography coupled to tandem mass spectrometry

A specific, sensitive and fast method based on high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) was developed for the determination of olmesartan in human plasma and urine. Solid-phase extraction (SPE) was used to isolate the compounds from biological matrix followed by injection of the extracts onto a C(18) column with isocratic elution. The method was validated over the concentration range of 0.2-1000 and 5-10,000 ng/mL for olmesartan in human plasma and urine, respectively. The method was applied to the pharmacokinetic study of olmesartan medoxomil in healthy Chinese male and female subjects.

Intestinal bacteria metabolize the dietary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine following consumption of a single cooked chicken meal in humans

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a carcinogenic heterocyclic amine formed in meats during cooking. Although the formation of PhIP metabolites by mammalian enzymes has been extensively reported, the involvement of the intestinal bacteria remains unclear. This study examined the urinary and fecal excretion of a newly identified microbial PhIP metabolite 7-hydroxy-5-methyl-3-phenyl-6,7,8,9-tetrahydropyrido[3',2':4,5]imidazo[1,2-a]pyrimidin-5-ium chloride (PhIP-M1) in humans. The subjects were fed 150 g of cooked chicken containing 0.88-4.7 microg PhIP, and urine and feces collections were obtained during 72 h after the meal. PhIP-M1 and its trideuterated derivate were synthesized and a LC/MS/MS method was developed for their quantification. The mutagenic activity of PhIP-M1, as analyzed using the Salmonella strains TA98, TA100 and TA102, yielded no significant response. Of the ingested PhIP dose, volunteers excreted 12-21% as PhIP and 1.2-15% as PhIP-M1 in urine, and 26-42% as PhIP and 0.9-11% as PhIP-M1 in feces. The rate of PhIP-M1 excretion varied among the subjects. Yet, an increase in urinary excretion was observed for successive time increments, whereas for PhIP the majority was excreted in the first 24h. These findings suggest that besides differences in digestion, metabolism and diet, the microbial composition of the gastrointestinal tract also strongly influences individual disposition and carcinogenic risk from PhIP.

Inhibitory Effect of Valproic Acid on Cytochrome P450 2C9 Activity in Epilepsy Patients

Drug interactions constitute a major problem in the treatment of epilepsy because drug combinations are so common. Valproic acid is a widely used anticonvulsant drug with a broad therapeutic spectrum. Case reports suggest interaction between valproic acid and other drugs metabolized mainly by cytochrome P450 isoforms. The aim of this study was to evaluate the inhibitory effect of valproic acid on cytochrome P450 2C9 (CYP2C9) activity by using losartan oxidation as a probe in epilepsy patients. Patients were prescribed sodium valproate (mean 200 mg/day for the first week and 400 mg/day in the following period) according to their clinical need. A single oral dose of 25 mg losartan was given to patients before and after the first dose, first week and 4 weeks of valproic acid treatment. Losartan and E3174, the CYP2C9-derived carboxylic acid metabolite of losartan in 8 hr urine were assayed by using high pressure liquid chromatography. Urinary losartan/E3174 ratio did not change significantly on the first day (0.9, 0.3-3.5; median, range), and first week (0.6, 0.2-3.8; median, range), while a significant increase was observed after 4 weeks of valproic acid treatment (1.1, 0.3-5.7; median, range) as compared to that of measured before valproic acid administration (0.6, 0.1-2.1; median, range) (P = 0.039). The degree of inhibition was correlated with the steady-state plasma concentrations of valproic acid (r(2) = 0.70, P = 0.04). The results suggest an inhibitory effect of valproic acid on CYP2C9 enzyme activity in epilepsy patients at steady state. The risk of pharmacokinetic drug-drug interactions should be taken into account during concomitant use of valproic acid and CYP2C9 substrates.

Determination of eprosartan in human plasma and urine by LC/MS/MS

A protein precipitation, liquid chromatography/tandem mass spectrometry (LC/MS/MS) method has been developed and validated for the determination of eprosartan in human plasma and urine. The solvent system also served as a protein precipitation reagent. The chromatographic separation was achieved on a CAPCELL PAK C18 column (50 mmx2.0 mm, 5 microm, Shiseido). A mobile phase was consisted of 0.5% formic acid in water and 0.5% formic acid in acetonitrile (72:28). Detection was by positive ion electrospray tandem mass spectrometry on a Sciex API3000. The standard curves, which ranged from 5 to 2000 ng/mL in human plasma and from 0.25 to 50 microg/mL in urine, were fitted to a 1/x weighted quadratic regression model. The method proved to be accurate, specific and sensitive enough to be successfully applied to a pharmacokinetic study.

Development and validation of bioanalytical methods for imidafenacin (KRP-197/ONO-8025) and its metabolites in human urine by using liquid chromatography-tandem mass spectrometry

New bioanalytical methods have been developed for the determination of imidafenacin (KRP-197/ONO-8025, IM), a novel antimuscarinic drug developed for the treatment of overactive bladder, and its metabolites, M-2, M-3, M-4, M-6 and M-8 (method 1), M-5 and M-9 (method 2) in human urine by using liquid chromatography-tandem mass spectrometry. In each method, the urine sample was extracted by solid-phase extraction, separated on a semi-micro high-performance liquid chromatography column using gradient elution and detected by tandem mass spectrometer with an atmospheric pressure chemical ionization or ionspray interface. Extraction recoveries of IM and metabolites were 81.4% or more. Calibration curves had good linearity in the concentration ranges 0.2-50 ng/mL for IM, M-2, M-3, M-4, M-6 and M-8 (method 1) and 1-250 ng/mL for M-5 and M-9 (method 2), respectively. The accuracy and precision in the intra-day and inter-day reproducibility tests were within +/-17.0 and 16.1% at the lowest concentrations, and within +/-12.8 and 11.1% at higher concentrations, respectively. Using these analytical methods, excretion profiles of IM and its metabolites in human urine were successfully determined after oral administration of IM at the therapeutic dosage of 0.1 mg.

Analysis of aminoimidazole ribosides by capillary electrophoresis--diagnosing defects in second part of purine biosynthetic pathway

BACKGROUND

Only three inherited metabolic defects have been identified in purine de novo synthesis (PDNS). We present here CE methods for diagnosing defects in the second half of PDNS (from sixth to tenth enzymatic conversion) based on analysis of aminoimidazole ribosides - dephosphorylated intermediates - in urine.

METHODS

Assays were performed in an uncoated fused-silica capillary using two electrophoretic separation systems: 60 mmol/l borate - 2-amino-2-methyl-1-propanol-80 mmol/l sodium dodecylsulfate (pH 9.6) and 200 mmol/l phosphate - sodium (pH 1.8).

RESULTS

The reported conditions allowed separation of all metabolites from major urinary constituents with analysis time less than 10 min and separation efficiency of 220 and 350 thousands theoretical plates per meter for borate and phosphate system, respectively. The intra- and interday imprecisions were less than 4.4% and 9.9% CV. Potential usefulness of the methods was demonstrated on samples from a patient with adenylosuccinate lyase deficiency and Chinese hamster ovary cell lines defective in PDNS.

CONCLUSIONS

CE is a useful and effective tool in the analysis of aminoimidazole ribosides which enables diagnosis of known as well as not so far identified inherited defects of PDNS pathway.

Identification of 4-methylspinaceamine, a pictet-spengler condensation reaction product of histamine with acetaldehyde, in fermented foods and its metabolite in human urine

Previous study demonstrated that 4-methylspinaceamine (4-methyl-4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine), a Pictet-Spengler condensation reaction product of histamine with acetaldehyde, is present in human urine. The current study sought to determine whether 4-methylspinaceamine is present in fermented foods; its presence might be expected since both histamine and acetaldehyde are often present in these foods. Soy sauce, fish sauce, cheese, and shao hsing wine (Chinese wine) were found to contain 4-methylspinaceamine. The concentration of 4-methylspinaceamine excreted in human urine was greatly elevated after ingestion of a meal containing soy sauce as a dietary source of 4-methylspinaceamine, demonstrating that the level of 4-methylspinaceamine in human urine was affected by dietary foods. In addition, a metabolite of 4-methylspinaceamine in human urine was investigated. An enhanced peak in the HPLC chromatogram of human urine samples after ingestion of 4-methylspinaceamine-containing foods was observed. A peak at the same retention time was also observed from a human urine sample after administration of 4-methylspinaceamine, suggesting that the peak was due to a metabolite. By comparison with the newly synthesized authentic compound, the metabolite was identified as 1,4-dimethylspinaceamine.

Inhibitory Effect of 5-Fluorouracil on Cytochrome P450 2C9 Activity in Cancer Patients

Drug interactions have been reported between 5-fluorouracil and cytochrome P450 2C9 (CYP2C9) substrates, S-warfarin and phenytoin. This study was performed to determine the influence of 5-fluorouracil on cytochrome P450 2C9 (CYP2C9) activity in colorectal cancer patients (n=17) receiving 5-fluorouracil. Losartan was used as a marker to assess CYP2C9 activity. Losartan and its CYP2C9 dependent metabolite, E-3174, were determined in urine. The ratios of urinary losartan/E-3174 before and after the 5-fluorouracil treatment were compared for each patient. Genotyping was performed to detect the CYP2C9*2 and CYP2C9*3. At the end of the first cycle of 5-fluorouracil, losartan/E-3174 ratio was increased by 28.0% compared to the pre-treatment values (P=0.15). In five patients recruited for phenotyping after three 5-fluorouracil cycles, the metabolic ratio was increased significantly by 5.3 times (P=0.03). The results suggest that in most patients 5-fluorouracil inhibited CYP2C9 activity. This inhibition was more pronounced when the total administered dose increased. This finding may help explain the mechanism of interaction between 5-fluorouracil and CYP2C9 substrates.

The impact of glucuronidation on the bioactivation and DNA adduction of the cooked-food carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine in vivo

UDP-glucuronosyltransferases (UGTs) catalyze the glucuronidation of many different chemicals. Glucuronidation is especially important for detoxifying reactive intermediates from metabolic reactions, which otherwise can be biotransformed into highly reactive cytotoxic or carcinogenic species. Detoxification of certain food-borne-carcinogenic heterocyclic amines (HAs) is highly dependent on UGT1A-mediated glucuronidation. 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), the most mass abundant carcinogenic HA found in well-done cooked meat, is extensively glucuronidated by UGT1A proteins. In humans, CYP1A2 catalyzed N-hydroxylation and subsequent UGT1A-mediated glucuronidation is a dominant pathway in the metabolism of PhIP. Therefore, changes in glucuronidation rates could significantly alter PhIP metabolism. To determine the importance of UGT1A-mediated glucuronidation in the biotransformation of PhIP, hepatic UGT1A deficient Gunn and UGT1A proficient Wistar rats were exposed to a 100 microg/kg oral dose of [(14)C]PhIP. Urine was collected over 24 h and the PhIP urinary metabolite profiles were compared between the two strains. After the 24 h exposure, livers and colons were removed and analyzed for DNA adduct formation by accelerator mass spectrometry. Wistar rats produced several PhIP and N-hydroxy-PhIP glucuronides that accounted for approximately 25% of the total amount of recovered urinary metabolites. In the Gunn rats, PhIP and N-hydroxy-PhIP glucuronides were reduced by 68-92%, compared with the Wistar rats. PhIP-DNA adduct analysis from the Gunn rats revealed a correlation between reduced urinary PhIP and N-hydroxy-PhIP glucuronide levels and increased hepatic DNA adducts, compared with the Wistar rats. In the colon, DNA adduct levels were lower in the Gunn rats compared with the Wistar rats, suggesting deficient hepatic UGT1A activity provides protection against DNA adduct formation in peripheral tissue. Due to differences in PhIP metabolism between humans and rodents, extrapolation of these results to the human situation must be done with caution. These results indicate that UGT1A-mediated glucuronidation of PhIP and N-hydroxy-PhIP is an important pathway for PhIP detoxification, and demonstrate the importance of tissue-specific metabolism. Tissues with reduced UGT1A activity can have a higher rate of PhIP activation and be more inclined to form DNA adducts compared with tissues with normal UGT1A activity.

Formation of a Mutagenic Heterocyclic Aromatic Amine from Creatinine in Urine of Meat Eaters and Vegetarians

Liquid chromatography electrospray ionization mass spectrometry (MS) with a triple quadrupole MS was used to identify known and novel heterocyclic aromatic amines (HAAs) in human urine. The identities of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (8-MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) were confirmed by their product ion spectra. The constant neutral loss scan mode was employed to probe for other analytes in urine that display the transition [M+H]+-->[M+H-CH3*]+*, which is common to HAAs containing an N-methylimidazo moiety, and led to the detection of a previously unreported isomer of 8-MeIQx [Holland, R., et al. (2004) Chem. Res. Toxicol. 17, 1121-1136]. We now report the identification of another novel HAA, 2-amino-1-methylimidazo[4,5-b]quinoline (IQ[4,5-b]), an isomer of the powerful animal carcinogen 2-amino-3-methylimidazo[4,5-f]quinoline (IQ). The amounts of IQ[4,5-b] measured in the urine of human volunteers who consumed grilled beef ranged from 15 to 135% of the ingested dose, while the amounts of 8-MeIQx and PhIP excreted in urine were on average <2% of the ingested dose. Base treatment of urine at 70 degrees C increased the concentrations of 8-MeIQx and PhIP by as much as 6-fold, indicating the presence of phase II conjugates; however, the amount of IQ[4,5-b] increased by more than 100-fold. IQ[4,5-b] was also detected in the urine of vegetarians following base hydrolysis. The formation of IQ[4,5-b], but not IQ, 8-MeIQx, or PhIP, also occurred in urine incubated at 37 degrees C. Creatinine and 2-aminobenzaldehyde are likely precursors of IQ[4,5-b]. The detection of IQ[4,5-b] in the urine of both meat eaters and vegetarians suggests that this HAA may be present in nonmeat staples or that IQ[4,5-b] formation may occur endogenously within the urinary bladder or other biological fluids.

Identification of 4-methylspinaceamine - a Pictet – Spengler condensation reaction product of histamine with acetaldehyde - in human urine

This study reports the first identification of 4-methylspinaceamine (4-MSPA)-a Pictet Spengler condensation reaction product of histamine with acetaldehyde-in human urine. 4-MSPA was identified and quantified as follows: the target compound was partially purified by solvent extraction from a urine sample spiked with N-methylpiperazine (N-MP) as an internal standard, then derivatized to a naphthylthiourea derivative with 1-naphthylisothiocyanate (NITC) and finally analyzed by HPLC. For verification, 4-MSPA was also analyzed by ion spray-mass spectrometry (IS-MS), using 4-MSPA-d4 as an internal standard. The amount of 4-MSPA in human urine varied between individuals and from day-to-day, ranging from undetectable to 0.80 nmol/mL.

CYP1A2 and NAT2 genotype/phenotype relations and urinary excretion of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in a human dietary intervention study

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a mutagenic and carcinogenic heterocyclic amine formed during ordinary cooking, and is subsequently metabolically activated by cytochrome P4501A2 (CYP1A2) and N-acetyltransferase 2 (NAT2). Respective genes encoding for these enzymes, display polymorphic distribution in the human population and are thus believed to cause interindividual differences in cancer risk susceptibility. The present study investigated the influence of dietary exposure and CYP1A2 and NAT2 genotypes and phenotypes on differential urinary PhIP excretion levels in 71 human volunteers after consumption of either a high (7.4 ng/g) or low (1.7 ng/g) dose of PhIP. Urinary PhIP excretion levels were found to reflect recent dietary exposure levels, with average levels of 174% (high dose group) and 127% (low dose group), as compared to pre-feed levels. Urinary caffeine metabolite ratios were significantly different between the two NAT2 genotypes, whereas for CYP1A2, the apparent difference in metabolic ratios between the genotypes was statistically non-significant. Significant correlations were firstly found between the CYP1A2-164A-->C (CYP1A2*1F) polymorphism and differential urinary PhIP excretion levels. Although the found correlations are driven primarily by a small number of subjects possessing the homozygous variant constellation, the strong influence of this genotype indicates that the CYP1A2*1F polymorphism could play an important role in human cancer risk susceptibility.

PhIP metabolites in human urine after consumption of well-cooked chicken

We devised an assay to quantify the metabolites of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) in human urine following a single exposure to well-cooked meat. Our method uses LC/MS/MS to detect four metabolites and four deuterated internal standard peaks in a single chromatographic run. N2-OH-PhIP-N2-glucuronide was the most abundant urinary metabolite excreted by the 12 individuals who participated in our study. N2-PhIP glucuronide was the second most abundant metabolite for 8 of the 12 volunteers. The stability of PhIP metabolism over time was studied in three of the volunteers who repeated the assay eight times over a 2.5 year-period. PhIP metabolite excretion varied in each subject over time, although the rate of excretion was more constant. Our results suggest that quantifying PhIP metabolites should make future studies of individual susceptibility and dietary interventions possible.

Urinary N2-(2'-deoxyguanosin-8-yl)PhIP as a biomarker for PhIP exposure

The food-derived, heterocyclic aromatic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is genotoxic and is carcinogenic in experimental animals. Studies on the role of PhIP in human diet-related cancer would be aided considerably by the availability of a readily applicable biomarker of the internal dose of the ultimate genotoxic species. PhIP has been shown to adduct primarily at C-8 of deoxyguanosine in DNA and so the DNA repair product N(2)-(2'-deoxyguanosin-8-yl)PhIP is a potential biomarker of DNA adduction and repair after exposure to PhIP. An assay for N(2)-(2'-deoxyguanosin-8-yl)PhIP in urine has been developed based on liquid chromatography mass spectrometry, using a deuterated analogue of the nucleoside as an internal standard and an antibody-mediated extraction procedure. Polyclonal antibodies were raised against the PhIP-nucleotide, PhIP-nucleoside and PhIP-guanine base adducts conjugated to keyhole limpet haemocyanin. Following their evaluation, the immobilized PhIP nucleotide antibody was used for the extraction of N(2)-(2'-deoxyguanosin-8-yl)PhIP from urine. The limit of detection of the assay was 125 pg and the limit of quantification 200 pg for a 50 ml human urine sample. Following oral administration of PhIP (20 mg/kg body wt/day) to rats for 6 days, N(2)-(2'-deoxyguanosin-8-yl) PhIP was readily detected in the urine, reaching steady state over 3 days. This is the first direct demonstration of the urinary elimination of this adduct following exposure to parent amine. The half-life of the adduct with DNA was estimated to be approximately 20 h. The total amount of PhIP recovered in the urine as adduct was <0.5 x 10(-3)% of the dose administered. Levels of the PhIP adduct in urine collections from human subjects ingesting the amine (4.9 micro g) in cooked meat were below the limits of detection, indicating that humans are exposed to a bioactive dose of <3 x 10(-4) of that associated with a non-carcinogenic level in rats.

Application of LC-NMR for Characterization of Rat Urinary Metabolites of Zonampanel Monohydrate (YM872)

Zonampanel monohydrate (YM872) has a potent and selective antagonistic effect on the glutamate receptor subtype, alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor. Metabolic fingerprinting in rat urine after a single intravenous administration of (14)C-labeled YM872 ((14)C-YM872) revealed the presence of two metabolites, R1 and R2. The two metabolites were semi-purified by preparative HPLC from rat urine after a single intravenous administration of non-labeled YM872, and their structures were elucidated by various instrumental analyses involving LC-NMR. The results showed that R1 and R2 have a hydroxyamino group and an amino group at the C-7 position of the quinoxalinedione skeleton, respectively. Therefore, the proposed metabolic pathway of YM872 in rats involves the reduction of the nitro group to a hydroxyamino group and then subsequent reduction to an amino group.

The breast cancer resistance protein (Bcrp1/Abcg2) restricts exposure to the dietary carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine

The food carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is the most abundant heterocyclic amine found in various protein containing foods. PhIP is mutagenic and carcinogenic in rodents, inducing lymphomas in mice and colon, mammary and prostate carcinomas in rats. It has also been implicated in human breast carcinogenesis. Humans on a normal Western diet are exposed to PhIP on a daily basis. The breast cancer resistance protein (BCRP/ABCG2) transports various anticancer drugs from cells, causing multidrug resistance. By its presence in the apical membrane of the intestine and bile canalicular membrane, it also protects the body from substrate drugs and toxins. We investigated whether Bcrp1 could affect PhIP exposure of the body because this could implicate BCRP activity in the cancer risk due to PhIP. Using polarized cell lines, we found that PhIP is efficiently transported by murine Bcrp1. In vivo pharmacokinetic studies showed that at a dose of 1 mg/kg [(14)C]PhIP the area under the curve for oral administration was 2.9-fold higher in Bcrp1(-/-) compared with wild-type mice (306 +/- 39 versus 107 +/- 15 h.ng/ml) and, for i.v. administration, 2.2 fold higher (386 +/- 36 versus 178 +/- 8.9 h.ng/ml). Wild-type mice cleared [(14)C]PhIP mainly by fecal excretion, but this shifted to primarily urinary excretion in Bcrp1(-/-) mice. In mice with a cannulated gall bladder, both hepatobiliary and direct intestinal excretion of [(14)C]PhIP were greatly impaired in Bcrp1(-/-) compared with wild-type mice (9.0 +/- 4.4 versus 36.5 +/- 9.4% and 1.5 +/- 0.8 versus 4.2 +/- 1.5%, respectively). We conclude that Bcrp1 effectively restricts the exposure of mice to ingested PhIP by decreasing its uptake from the gut lumen and by mediating hepatobiliary and intestinal elimination. Intra- or interindividual differences in BCRP activity in humans may thus also affect the exposure to PhIP and related food carcinogens, with possible implications for cancer susceptibility.

Simultaneous determination of losartan and EXP3174 in human plasma and urine utilizing liquid chromatography/tandem mass spectrometry

Losartan is an orally active angiotensin II receptor antagonist indicated for the treatment of hypertension. EXP3174 is an active metabolite, which contributes to the overall activity of losartan. Analytical methods for the simultaneous determination of losartan and its active metabolite EXP3174 in human plasma and urine with limited plasma sample size have been developed and validated to support a pediatric clinical program. In both methods, analytes are extracted from the matrixes by liquid-liquid extraction and separated using reverse phase high-performance liquid chromatography (HPLC). A tandem mass spectrometer (MS/MS) with a Turbo ionspray (TIS) interface in multiple-reaction-monitoring (MRM) mode is used for detection of the analytes in both methods. The plasma method has a lower limit of quantitation (LOQ) of 1 ng/ml with a linearity range of 1-500 ng/ml for losartan and EXP3174 using 100 microl of plasma. For the urine method, the LOQ for both losartan and EXP3174 is 2 ng/ml using 0.5 ml of urine, and the linearity range for both analytes is 2-1000 ng/ml. Validation procedures have proven that both methods are robust, accurate, and reproducible. Both methods have been used to assay clinical samples and provided satisfactory results.

Losartan and E3174 pharmacokinetics in cytochrome P450 2C9*1/*1, *1/*2, and *1/*3 individuals

STUDY OBJECTIVE

To determine if differences in the pharmacokinetics of losartan and its pharmacologically active E3174 metabolite exist among individuals expressing the cytochrome P450 (CYP) 2C9*1/*1, *1/*2, and *1/*3 genotypes.

DESIGN

Single-dose pharmacokinetic study.

SETTING

University general clinical research center.

SUBJECTS

Fifteen healthy volunteers, five from each genotype: CYP2C9*1/*1, *1/*2, and *1/*3.

INTERVENTION

A single oral dose of losartan 50 mg.

MEASUREMENTS AND MAIN RESULTS

Plasma and urine samples were collected for 24 hours, and losartan and E3174 pharmacokinetic data were compared across the three genotypes. Orthostatic blood pressure was measured over 12 hours after dosing. No significant differences were observed among the three groups in losartan or E3174 area under the plasma concentration-time curve, losartan or E3174 elimination half-life, or losartan oral clearance. A significant association between CYP2C9 genotype and losartan to E3174 formation clearance was observed, such that 50% of the variability was accounted for by the genotype. No significant relationship between that genotype and blood pressure was observed at any time.

CONCLUSION

Differences in the pharmacokinetics of losartan and its active E3174 metabolite were not observed in healthy subjects with the genotype of CYP2C9*1/*2 and *1/*3 compared with those expressing *1/*1. Alterations in losartan dosing in CYP2C9*1/*2 and *1/*3 individuals does not appear necessary.

Treatment of adult systemic mastocytosis with interferon-alpha: results of a multicentre phase II trial on 20 patients

Systemic mastocytosis (SM) is characterized by proliferation of mast cells in various organs, which may release a wide variety of mediators, thereby explaining the broad clinical spectrum of disease manifestations. The potentially life-threatening systemic symptoms and tumoral proliferation are poorly controlled despite the use of several cytotoxic chemotherapies and/or symptomatic treatments. Twenty consecutive adult SM patients with histologically confirmed bone marrow (BM) involvement received interferon-alpha subcutaneously (1-5 million units/m2/d, with progressive dose intensification over the first month of treatment) and were evaluated after 6 months of therapy. Seven of them had previously received symptomatic treatments, including steroids, which were ineffective. Among the 13 patients treated for at least 6 months, seven partial and six minor responses, mainly concerning vascular congestion and skin lesions, were obtained, while BM infiltration remained unchanged in 12 patients. The significant reduction of mast-cell mediator levels after 6 months of treatment was not predictive of clinical remission. The rate of depression was unexpectedly high (seven patients; 35%). Two patients died soon after starting therapy (one myocardial infarction, one septic shock). Six months of interferon-alpha may relieve vascular congestion in adults with SM, probably by inhibiting mast-cell degranulation.

Development and validation of a highly sensitive RIA for zoledronic acid, a new potent heterocyclic bisphosphonate, in human serum, plasma and urine

Zoledronic acid is a new, highly potent bisphosphonate drug under clinical evaluation. A radioimmunoassay has been developed to determine zoledronic acid concentration in human serum, plasma, and urine. The assay utilizes rabbit polyclonal antisera against a zoledronic acid-BSA conjugate and a [125I]zoledronic acid derivative as tracer in a competitive format adapted to microtiter plates. The assay shows a LLOQ 0.4 ng/ml in serum or plasma (interassay%CV=17%, accuracy 97%), 5 ng/ml in urine (21%, 98%). In 23 patients receiving 4, 8 or 16 mg of zoledronic acid, drug concentrations in plasma were dose proportional and showed a multiphasic profile, followed by a prolonged gradual decline to concentrations near the LLOQ. Zoledronic acid disposition in plasma and the recovery of only 40-50% of the dose in urine are consistent with the rapid and extensive uptake by and slow release from bone in parallel with renal clearance, typically shown by bisphosphonates.

Metabolites of 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP) in human urine after consumption of charbroiled or fried beef

Heterocyclic amines (HAs) are carcinogenic combustion products formed during the cooking of meat at moderate to high temperatures. PhIP is the most common HA formed in fried, grilled or broiled meat, and is a colon, breast, and prostate carcinogen in rodents. The major metabolites of PhIP detected in human urine are N(2)-OH-PhIP-N(2)-glucuronide, PhIP-N(2)-glucuronide, N(2)-OH-PhIP-N(3)-glucuronide, and 4'-PhIP-sulphate. We have measured the time course of PhIP in untreated and acid- or alkali-hydrolyzed urines from 10 healthy non-smoking subjects ingesting identical amounts of char-broiled beef (containing both HAs and PAHs) for 5 days. The morning after the first day of broiled beef consumption (containing 7.7 micro g PhIP), urinary concentration of PhIP increased 14- to 38-fold above mean prefeed concentration. Following cessation of broiled meat consumption, urinary PhIP declined to near prefeed levels within 48-72 h. The ratio of alkali-labile PhIP metabolites to unmetabolized PhIP varied by 2.7-fold among subjects, ranging from 18:1 to 48:1. In a subsequent study we measured PhIP in acid-hydrolyzed urine from 66 subjects ingesting beef pan-fried at high temperature. A significant correlation (r=0.61, P<0.0001) was observed between the amount of fried meat ingested and concentration of PhIP in urines collected between 0 and 12h after feeding. Other investigators have identified 2-OH-PhIP in acid-hydrolyzed urine from these subjects, and also observed a significant correlation (r=0.52, P<0.0001) with the amount of fried meat ingested. Additional studies have measured PhIP metabolites in subjects consuming their normal (unrestricted) diet. PhIP was detected in acid-hydrolyzed urine from 20 to 50% of these subjects, depending on ethnic group. Taken together, these studies indicate that significant amounts of PhIP are bioavailable from ingestion of fried or char-broiled meats, and that urinary PhIP metabolites reflect recent (12-24h) ingestion. Furthermore, significant interindividual differences in the amounts of urinary PhIP metabolite excreted are observed following ingestion of similar amounts of PhIP. These differences do not correlate with interindividual differences in excretion of urinary pyrene metabolites in the same individuals after ingestion of char-broiled beef, indicating that levels of PhIP and pyrene metabolites in human urine are mediated by compound-specific metabolic factors.

Factors affecting human heterocyclic amine intake and the metabolism of PhIP

We are working to understand possible human health effects from exposure to heterocyclic amines that are formed in meat during cooking. Laboratory-cooked beef, pork, and chicken are capable of producing tens of nanograms of MeIQx, IFP, and PhIP per gram of meat and smaller amounts of other heteroyclic amines. Well-done restaurant-cooked beef, pork, and chicken may contain PhIP and IFP at concentrations as high as tens of nanograms per gram and MeIQx at levels up to 3 ng/g. Although well-done chicken breast prepared in the laboratory may contain large amounts of PhIP, a survey of flame-grilled meat samples cooked in private homes showed PhIP levels in beef steak and chicken breast are not significantly different (P=0.36). The extremely high PhIP levels reported in some studies of grilled chicken are not seen in home-cooked samples.Many studies suggest individuals may have varying susceptibility to carcinogens and that diet may influence metabolism, thus affecting cancer susceptibility. To understand the human metabolism of PhIP, we examined urinary metabolites of PhIP in volunteers following a single well-done meat exposure. Using solid-phase extraction and LC/MS/MS, we quantified four major PhIP metabolites in human urine. In addition to investigating individual variation, we examined the interaction of PhIP with a potentially chemopreventive food. In a preliminary study of the effect of broccoli on PhIP metabolism, we fed chicken to six volunteers before and after eating steamed broccoli daily for 3 days. Preliminary results suggest that broccoli, which contains isothiocyanates shown to induce Phases I and II metabolism in vitro, may affect both the rate of metabolite excretion and the metabolic products of a dietary carcinogen. This newly developed methodology will allow us to assess prevention strategies that reduce the possible risks associated with PhIP exposure.

2-Amino-1-methyl-6-(5-hydroxy-)phenylimidazo[4,5-b]pyridine (5-OH-PhIP), a biomarker for the genotoxic dose of the heterocyclic amine, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP)

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a mutagenic and carcinogenic heterocyclic amine formed during ordinary cooking. PhIP is metabolically activated by CYP P450 mediated N-hydroxylation followed by phase II esterification. The ultimate mutagenic metabolite reacts with DNA resulting in formation of adducts, and with proteins and other cellular constituents resulting in unstable products which are degraded to 5-hydroxy-PhIP. Rats were dosed orally with PhIP and urine and faeces were collected to 24, 48 and 72 h. Urine and faeces samples were hydrolysed with glucuronidase/sulfatase in order to release conjugated metabolites, followed by purification on C18 columns. The rats excreted 0.88% of the dose as 5-hydroxy-PhIP with the urine to 24 h and 0.04 and 0.01% to 48 and 72 h, respectively. The amounts of 5-hydroxy-PhIP found in faeces were 0.03, 0.1 and 0% to 24, 48 and 72 h. Urinary excretion of 5-hydroxy-PhIP showed a linear dose-response relationship in rats dosed orally with PhIP. This shows that 5-hydroxy-PhIP is also formed in vivo and that 91% is excreted with the urine in 24 h, indicating the possible use of 5-hydroxy-PhIP as a urinary biomarker for the bioactive dose of PhIP. In a preliminary study, using molecular imprinted polymer a specific sorbent for purification, after enzymatic hydrolysis and purification on a C18 column, we have identified 5-OH-PhIP in a 24-h urine sample from a male volunteer who had ingested a fried beef. This indicates that urinary 5-OH-PhIP could be used as an easily obtainable marker for the genotoxic dose of PhIP in human biomonitoring studies.

Prospective study of the ability of histamine, serotonin or serum chromogranin A levels to identify gastric carcinoids in patients with gastrinomas

BACKGROUND

Chronic hypergastrinaemia causes gastric enterochromaffin cell proliferation and carcinoid tumours. The only reliable means to diagnose enterochromaffin cell changes/carcinoids is by biopsy.

AIM

To assess whether serum histamine, chromogranin A or serotonin and urinary N-methylimidazoleacetic acid or 5-hydroxyindoleacetic acid correlate with advanced enterochromaffin cell changes or gastric carcinoids in patients with gastrinomas.

METHODS

Consecutive patients (n=145) had the above assays and endoscopy with gastric biopsies.

RESULTS

Lower N-methylimidazoleacetic acid and chromogranin A levels (P < 0.0001) occurred in disease-free patients. In patients with active disease, the fasting serum gastrin levels correlated (P < 0.0001) with both chromogranin A and N-methylimidazoleacetic acid levels. Chromogranin A (P=0.005), but not N-methylimidazoleacetic acid, serotonin, 5-hydroxyindoleacetic acid or histamine levels, correlated with the enterochromaffin cell index. Carcinoids, but not advanced enterochromaffin cell changes only, were associated with higher chromogranin A and N-methylimidazoleacetic acid levels.

CONCLUSIONS

Serum chromogranin A levels and urinary N-methylimidazoleacetic acid levels, but not serum histamine or serotonin or urinary 5-hydroxyindoleacetic acid, correlate with the presence of gastric carcinoids. However, no assay identified patients with advanced enterochromaffin cell changes only with high sensitivity/specificity. Thus, N-methylimidazoleacetic acid and chromogranin A levels are unable to identify patients with advanced changes in enterochromaffin cells and therefore neither can replace routine gastric biopsies.

Paeoniae Radix, a traditional Chinese medicine, and CYP2C9 activity

Paeoniae Radix (PR) is a commonly used traditional Chinese medicine. A slight effect of PR on the pharmacokinetics of phenytoin that is mainly metabolised by CYP2C9 has been reported. The aim of this pilot study was to clarify if PR has an effect on losartan oxidation used as a measure of CYP2C9 activity. Three healthy volunteers received a single oral dose of losartan before and after PR treatment. Losartan and E-3174, an active metabolite of losartan, were analysed in 8 hour urine. PR did not seem to have an effect on CYP2C9 activity when the losartan/E-3174 ratios were compared before and after PR treatment (P = 0.56) although a larger study would need to be undertaken to confirm this finding.

Excretion of the N(2)-glucuronide conjugate of 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine in urine and its relationship to CYP1A2 and NAT2 activity levels in humans

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a mutagenic and carcinogenic heterocyclic aromatic amine formed in meat products during cooking. The genotoxity of PhIP requires an initial cytochrome P450-mediated N-oxidation followed by N-O-esterification catalyzed generally by N-acetyltransferases and sulfotransferases. This study examined the urinary excretion of N(2)-(beta-1-glucos-iduronyl)-2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine-the major human urinary N-oxidation metabolite of PhIP-and determined its relationship to individual activity levels of cytochrome P4501A2 (CYP1A2) and N-acetyltransferase (NAT2). The subjects (33 males and 33 females) in the dietary study were phenotyped for their CYP1A2 and NAT2 activity prior to consumption of meat-based diet, and urine collections were obtained 0-12 and 12-24 h after ingestion of the meal. Acidic hydrolysis of N(2)-(beta-1-glucosiduronyl)-2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine and its d(3)-analog to form their respective deaminated products 2-hydroxy-1-methyl-6-phenylimidazo[4,5-b]pyridine (2-OH-PhIP) was used in the assay. The products after derivatization were analyzed by capillary gas chromatography-negative ion chemical ionization mass spectrometry with selective ion monitoring. The amount of N(2)-(beta-1-glucosiduronyl)-2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine measured as the acid hydrolysis product 2-OH-PhIP in the 0-12 h urine was 20.2 +/- 8.0% (mean +/- SD) of the ingested dose; the median was 18.8% and the range varied from 5.4 to 39.6% within the group. In a subset (n = 18) of samples from individual urine collected from the 12-24 h period, an average value of 4.4 +/- 2.5% (+/- SD) of the dose was recovered. The excretion of N(2)-(beta-1-glucosiduronyl)-2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine in the 0-12 h urine was significantly related to the quantity of PhIP ingested for all subjects (r = 0.52, P <0.0001). Linear regression analysis of the relationship between the excretion level of N(2)-(beta-1-glucosiduronyl)-2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine, adjusted for meat intake and CYP1A2 activity in the combined group of males and females showed a low association (r = 0.25, P = 0.05). There was no association between the amount of N(2)-(beta-1-glucosiduronyl)-2-hydroxyamino-1-methyl-6-phenylimid-azo[4,5-b]pyridine in urine and NAT2 activity levels of the subjects nor with the age of the subjects. N(2)-(beta-1-glucosi-duronyl)-2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine comprised a significant proportion of the ingested dose in some individuals; however, considerable variation was found within the group. The results indicate that interindividual differences in the rates of N-oxidation of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, as well as phase II glucuronidation reactions regulate the formation of this metabolite in humans.

Neuronal storage of histamine in the brain and tele-methylimidazoleacetic acid excretion in portocaval shunted rats

Rats with portocaval anastomosis (PCA), an animal model of hepatic encephalopathy (HE), have very high brain histamine concentrations. Our previous studies based on a biochemical approach indicated histamine accumulation in the neuronal compartment. In this study, immunohistochemical evidence is presented which further supports the amine localization in histaminergic neurons. These neurons become pathological in appearance with cisternae frequently seen along histaminergic fibres in many brain areas, including the hypothalamus, amygdala, substantia nigra and cerebral cortex. Such formations were not observed in sham-operated animals. The neuronal deposition is predominant, and unique for histamine. It serves as a mechanism to counterbalance excessive brain neurotransmitter formation evoked by PCA. However, there are other mechanisms. The data provided here show that there is also a significant increase in histamine catabolism in the shunted rats, as reflected by both the higher brain N-tele-methylhistamine (t-MeHA) concentration and urinary excretion of N-tele-methylimidazoleacetic acid (t-MelmAA), a major brain histamine end product. The stomach, in addition to the brain, is a site of enhanced histamine synthesis in portocavally shunted subjects. After gastrectomy or food deprivation to eliminate the contribution of the stomach, shunted rats excrete significantly more t-MelmAA, implying the role of the CNS. This last finding suggests that under strictly defined conditions, namely in parenterally fed HE patients with abnormal plasma L-histidine, the measurement of urinary t-MelmAA might provide valuable information concerning putative brain histaminergic activity.

Concentration of 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP) in urine and alkali-hydrolyzed urine after consumption of charbroiled beef

Heterocyclic amines (HAs) and polycyclic aromatic hydrocarbons are carcinogenic products formed during the cooking of meat at moderate to high temperatures. We have previously shown that the urinary concentration of 1-hydroxypyrene-glucuronide, a metabolite of pyrene, increased significantly in ten subjects who had ingested charbroiled ground beef. We now report the time course and interindividual variation of 2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine (PhIP) concentration in the urine samples from these ten subjects. PhIP concentration was determined in both untreated and alkali-hydrolyzed urine to obtain estimates of the proportion of conjugated PhIP metabolites in each subject. PhIP was measured by gas chromatography-negative ion chemical ionization-mass spectrometry after derivatization with pentafluorobenzyl bromide. Ten healthy non-smoking males consumed identical amounts of broiled beef on five consecutive days. The morning after the first day of broiled beef consumption, urinary concentration of PhIP increased 14-38 fold above mean pre-feed concentration of PhIP in individual alkali-hydrolyzed urine samples. Following cessation of broiled beef consumption, urinary PhIP concentration declined to near pre-feed levels within 48-72 hrs. The ratio of total alkali-labile PhIP metabolites to unmetabolized PhIP varied by about 2.7-fold among subjects, ranging from 18:1 to 48:1, suggesting that interindividual differences in PhIP metabolism occur and can be detected by this method. This study of urinary PhIP following ingestion of meat cooked by charbroiling, that contains both HAs and polycyclic aromatic hydrocarbons, extends previous studies of ingestion of pan-fried meat that contains primarily HAs. The results indicate that significant amounts of PhIP are bioavailable from ingestion of charbroiled ground beef and that measurement of proportions of alkali-labile PhIP metabolites and parent PhIP in human urine may yield information on individual metabolism of ingested PhIP.

Mastocytosis: review of clinical and experimental aspects

Mastcytosis is a rare disease characterized by an abnormal increase of mast cells in tissues. The skin is the organ most frequently involved, but mast cells also accumulate in the bone marrow, gastrointestinal tract, lymph nodes, spleen, and liver. Recent studies suggest that activating mutations of c-kit, a protooncogene encoding for the receptor (kit) of stem cell factor, are a possible cause of some forms of mastocytosis. In addition, an increased rate of chromosomal aberrations has been found. Despite significant advances in research on mastocytosis, curative treatment is not yet available. Current management is based on avoidance of mediator-releasing triggers and symptomatic treatment.

Urinary histamine metabolite elevations during experimental influenza infection

BACKGROUND

Although histamine is hypothesized to mediate symptoms induced by viral upper respiratory infections, elevations of this mediator have not been observed in nasal lavage fluids recovered from patients with viral upper respiratory infections.

OBJECTIVE

The purpose of this study was to use a novel method to determine whether histamine is released during experimental influenza A infection.

METHODS

Healthy adults (n = 15) were cloistered and inoculated intranasally with influenza A virus, and monitored for infection and illness. Daily morning void urines were collected and assayed for histamine and its metabolites by gas chromatography-mass spectrometry. Total histamine was calculated for each urine specimen by summing the assayed values of histamine and its metabolites.

RESULTS

All subjects were infected and developed illness. ANOVA documented a significant effect of study day (viral infection) on urinary levels of total histamine (P < 0.02). Pairwise analysis showed a significant elevation 2 days after inoculation.

CONCLUSIONS

These results provide the first direct evidence that histamine is released in vivo during infection with a virus that causes cold/flu symptoms.