Measurement of N-methyl-2-pyridone-5-carboxamide in urine by high performance liquid chromatography

Nicotinamide metabolism alterations in bladder cancer: Preliminary studies

OBJECTIVES

Cancer is one of the main cause of death in Western countries. Inflammation plays an important role in the pathogenesis of cancer. Nicotinamide (NA) - known for its anti-inflammatory properties - participates in the processes related to the cell cycle regulation and DNA repair, which are relevant in cancer development. This study aimed to investigate the nicotinamide metabolism alterations in bladder cancer.

METHODS

Blood and plasma samples of patients with bladder cancer were collected. Blood pyridine and adenine nucleotides concentration were measured using high performance liquid chromatography (HPLC). Plasma nicotinamide metabolites concentration were determined using high performance liquid chromatography - mass spectrometry (LC/MS).

RESULTS

Our results indicated that the development of bladder cancer caused significant decrease in the concentration of N-methylnicotinamide (MetNA) (0.07 ± 0.02 vs 0.1 ± 0.03 µmol/l) and an increase in the concentration of N-methyl-2-pyridone-5-carboxamide (Met2PY) - one of the final nicotinamide metabolites: (1.1 ± 0.15 vs 0.7 ± 0.07 µmol/l) in comparison to the control. The association between the stage of cancer and the increase in both, Met2PY and Met4PY levels was observed. Blood ATP and NAD levels were significantly decreased in bladder cancer patients as compared to the control (970.8 ± 77.84 vs 1165.00 ± 57.76 µmol/l; 45.86 ± 2.98 vs 53.06 ± 2.28 µmol/l respectively).

CONCLUSIONS

Bladder cancer development caused substantial changes in nicotinamide metabolism, such as decreased plasma MetNA and increased Met2PY concentration. Analysis of the nicotinamide and its metabolites concentrations - as new biomarkers - may allow to track the course of pathological processes in cancer.

Intervening before the onset of Type 1 diabetes: baseline data from the European Nicotinamide Diabetes Intervention Trial (ENDIT)

AIMS/HYPOTHESIS

To set up a clinical trial to establish whether nicotinamide can prevent or delay clinical onset of Type 1 diabetes.

METHOD

The European Nicotinamide Diabetes Intervention Trial is a randomised, double-blind, placebo-controlled intervention trial undertaken in 18 European countries, Canada and the USA. Entry criteria were a first-degree family history of Type 1 diabetes, age 3-40 years, confirmed islet cell antibody (ICA) levels greater than or equal to 20 JDF units, and a non-diabetic OGTT; the study group was further characterised by intravenous glucose tolerance testing, measurement of antibodies to GAD, IA-2 and insulin and HLA class II genotyping.

RESULTS

ICA screening was carried out in approximately 30,000 first-degree relatives. A total of 1004 individuals fulfilled ICA criteria for eligibility, and 552 (288 male) were randomised to treatment. Of these, 331 were aged less than 20 years (87% siblings and 13% offspring of the proband with diabetes) and 221 were 20 years of age or more (76% parents, 21% siblings and 3% offspring). Oral glucose tolerance was normal in 500 and impaired in 52 (9.4%), and first phase insulin response in the IVGTT was below the 10(th) centile in 34%. Additional islet autoantibodies were identified in 354 trial entrants. Diabetes-associated HLA class II haplotypes were found in 84% of the younger age group and 80% of the older group. The protective haplotype HLA-DQA1*0102-DQB1*0602 was found in 10% overall.

CONCLUSIONS/INTERPRETATION

ENDIT has shown that a trial of an intervention designed to halt or delay progression to Type 1 diabetes can be carried out on a multinational collaborative basis, as and when potentially safe and effective forms of intervention become available. Primary screening with biochemically defined autoantibodies will substantially reduce the number of lower risk individuals to be included in future intervention trials

Identification of N1-methyl-2-pyridone-5-carboxamide and N1-methyl-4-pyridone-5-carboxamide as components in urine extracts of individuals consuming coffee

Caffeine metabolites were extracted from urine samples collected 4 h after consumption of a cup of coffee and were separated by high-performance liquid chromatography (HPLC) on a C18 (5 microm) reverse-phase column using an acetonitrile (5%), acetic acid (0.05%) solution as the mobile phase. The elution profiles indicated the constant presence of a major and a minor components eluting between the caffeine metabolites 5-acetamido-6-formyl-3-methyluracil (AFMU) and 7-methylxanthine (7X) in an approximate nine. A procedure was developed for the isolation of the major component in an apparent pure form, and the yield was 10-20 mg from 400 ml of urine. The minor component was isolated in an apparent pure form by this procedure as well, and the yield was 0.5 mg from 200 ml of urine. The average ratio of the two components in urine, UV absorption and 1H-NMR spectra of the two components, and 13C-NMR spectrum, mass spectrum and elemental analysis of the major component identified the major and minor components as N(1)-methyl-2-pyridone-5-carboxamide and N(1)-methyl-4-pyridone-5-carboxamide, respectively, two major metabolites of the vitamin niacin present in a significant amount in coffee beans. The two metabolites were present in the same average amount in urine extracts of individuals irregardless of coffee consumption. The findings are briefly discussed in relation to the nutritional sources of niacin and to current procedures for measuring amounts of the two metabolites in urine samples.

Direct determination of benzodiazepines in biological fluids by restricted-access solid-phase microextraction

A biocompatible solid-phase microextraction (SPME) fiber was prepared using an alkyl-diol-silica (ADS) restricted-access material as the SPME coating. The ADS-SPME fiber was able to simultaneously fractionate the protein component from a biological sample, while directly extracting several benzodiazepines, overcoming the present disadvantages of direct sampling in biological matrixes by SPME. The fiber was interfaced with an HPLC-UV system, and an isocratic mobile phase was used to desorb, separate, and quantify the extracted compounds. The calculated clonazepam, oxazepam, temazepam, nordazepam, and diazepam detection limits were 600, 750, 333, 100, and 46 ng/mL in urine, respectively. The method was confirmed to be linear over the range of 500-50000 ng/mL with an average linear coefficient (R2) value of 0.9918. The injection repeatability and intraassay precision of the method were evaluated over 10 injections, resulting in a RSD of approximately 6%. The ADS-SPME fiber was robust and simple to use, providing many direct extractions and subsequent determination of benzodiazepines in biological fluids.

Determination of amobarbital and secobarbital in plasma samples using micellar liquid chromatography

A new liquid chromatographic procedure for the determination of amobarbital and secobarbital in plasma samples is proposed. The method uses a Spherisorb octadecylsilane ODS-2 C(18) analytical column, a guard column of similar characteristics and 0.04 M CTAB solution buffered at pH 7.5 containing 3% 1-propanol as micellar mobile phase. The UV detection was carried out at 250 nm. Butabarbital was used as internal standard. Plasma samples preparation only required adequate dilution with the mobile phase before injection into the chromatographic system. The limits of detection were 0.2 and 0.4 mg/L for amobarbital and secobarbital, respectively. The proposed method allows the determination of amobarbital and secobarbital in plasma at therapeutic levels.