Assessment of Human Mycotoxin Exposure in Hungary by Urinary Biomarker Determination and the Uncertainties of the Exposure Calculation: A Case Study

Urinary biomarkers of mycotoxin exposure were evaluated in the case of healthy people (n = 41) and coeliac patients (n = 19) by using a multi-biomarker LC-MS/MS immunoaffinity based method capable to analyse biomarkers of nine mycotoxins, i.e., fumonisin B1 (FB1), fumonisin B2 (FB2), deoxynivalenol (DON), zearalenone (ZEN), ochratoxin A (OTA), Aflatoxin B1 (AFB1), T-2 toxin, HT-2 toxin and Nivalenol (NIV). Urinary biomarker concentrations were used to calculate the probable daily intake (PDI) of fumonisin B1, deoxynivalenol, zearalenone and ochratoxin A and compared with their tolerable daily intake (TDI). The human urinary excretion rate values reported in the literature and the 24 h excretion rate measured in piglets were used to estimate and compare the PDI values of the four mycotoxins. The highest mean biomarker concentrations were found for DON (2.30 ng/mL for healthy people and 2.68 ng/mL for coeliac patients). Mean OTA concentration was significantly higher (p < 0.001) in healthy people compared to coeliac patients. PDI calculated with piglets excretion data exceeded the TDI values by a much smaller percentage than when they were calculated from human data, especially for FB1. The uncertainties arising from the different calculations can be well perceived on the basis of these data.

GC-MS Studies on Derivatization of Creatinine and Creatine by BSTFA and Their Measurement in Human Urine

In consideration of its relatively constant urinary excretion rate, creatinine (2-amino-1-methyl-5H-imidazol-4-one, MW 113.1) in urine is a useful endogenous biochemical parameter to correct the urinary excretion rate of numerous endogenous and exogenous substances. Reliable measurement of creatinine by gas chromatography (GC)-based methods requires derivatization of its amine and keto groups. Creatinine exists in equilibrium with its open form creatine (methylguanidoacetic acid, MW 131.1), which has a guanidine and a carboxylic group. Trimethylsilylation and trifluoroacetylation of creatinine and creatine are the oldest reported derivatization methods for their GC-mass spectrometry (MS) analysis in human serum using flame- or electron-ionization. We performed GC-MS studies on the derivatization of creatinine (d0-creatinine), [methylo-2H3]creatinine (d3-creatinine, internal standard) and creatine (d0-creatine) with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) using standard derivatization conditions (60 min, 60 °C), yet in the absence of any base. Reaction products were characterized both in the negative-ion chemical ionization (NICI) and in the positive-ion chemical ionization (PICI) mode. Creatinine and creatine reacted with BSTFA to form several derivatives. Their early eluting N,N,O-tris(trimethylsilyl) derivatives (8.9 min) were found to be useful for the precise and accurate measurement of the sum of creatinine and creatine in human urine (10 µL, up to 20 mM) by selected-ion monitoring (SIM) of m/z 271 (d0-creatinine/d0-creatine) and m/z 274 (d3-creatinine) in the NICI mode. In the PICI mode, SIM of m/z 256, m/z 259, m/z 272 and m/z 275 was performed. BSTFA derivatization of d0-creatine from a freshly prepared solution in distilled water resulted in formation of two lMate-eluting derivatives (14.08 min, 14.72 min), presumably creatinyl-creatinine, with the creatininyl residue existing in its enol form (14.08 min) and keto form (14.72 min). Our results suggest that BSTFA derivatization does not allow specific analysis of creatine and creatinine by GC-MS. Preliminary analyses suggest that pentafluoropropionic anhydride (PFPA) is also not useful for the measurement of creatinine in the presence of creatine. Both BSTFA and PFPA facilitate the conversion of creatine to creatinine. Specific measurement of creatinine in urine is possible by using pentafluorobenzyl bromide in aqueous acetone.

High urinary excretion rate of glucose attenuates serum uric acid level in type 2 diabetes with normal renal function

Aims/Introduction The relationship between urinary excretion rate of glucose (UEGL) and uric acid (UA) metabolism in adults with type 2 diabetes (T2D) remains unclear to date. This study aimed to investigate the relationships of UEGL with serum UA (SUA), urinary excretion rate of uric acid (UEUA), and renal clearance of uric acid (CLUA) in adults with T2D. We hypothesised that high UEGL increases UA excretion, which in turn leads to lower SUA. Materials and methods This was a cross-sectional study of 635 inpatients with T2D recruited between 2018 and 2019. The relationships of UEGL with UEUA, CLUA, and hyperuricaemia were assessed using analysis of covariance and multivariate regression analysis. Results Patients in the higher quartile of UEGL tended to have lower SUA levels than those in the lower quartile. In contrast, patients in the higher quartile of UEGL tended to have higher CLUA (p for trend < 0.0001), and a similar trend was observed for UEUA. In adjusted multivariable linear regression model, UEGL was negatively correlated with SUA (β = − 0.023, 95% CI − 0.034 to − 0.013, p < 0.0001). However, positive correlations of UEGL with UEUA (β = 0.046, 95% CI 0.018–0.074, p = 0.001) and CLUA (β = 0.063, 95% CI 0.042–0.085, p < 0.0001) were found. Furthermore, consistent significant inverse associations were observed between quartiles of UEGL and hyperuricaemia in the adjusted multivariate logistic regression model. Conclusions A high UEGL level was positively correlated with UEUA and CLUA. Moreover, it was inversely associated with SUA level, and a consistently increased UEGL level reduced the risk of hyperuricaemia in patients with T2D.

1287. Pharmacokinetics, Safety, and Tolerability of Nacubactam after Single Coadministration with β-Lactams in Japanese Healthy Subjects

Background A single administration of nacubactam (NAC) with concomitant β-lactams in Japanese healthy subjects was conducted to assess pharmacokinetics (PK), safety, and tolerability of NAC in coadministration with cefepime (FEP), aztreonam (ATM), meropenem (MEM), or piperacillin (PIP). Methods The administration period included Period I, Period II, and Period III where NAC alone, concomitant drug alone, NAC and concomitant drug were administered by 1hour-IV infusion in each period. The dose of each drug tested was 2 g of NAC, FEP, ATM, MEM and 4 g of PIP and 8 subjects were administered in each cohort (32 subjects in total). Results Plasma NAC concentrations and NAC urinary excretion rate after coadministration with each concomitant drug were similar to those of administration of NAC alone. The PK parameter of NAC showed the similar value both after administration of NAC alone and after concomitant administration with each concomitant drug. Based on these findings, it was confirmed that coadministration of NAC with FEP, ATM, MEM or PIP did not affect the PK of NAC. Plasma concentrations and urinary excretion rate of FEP, ATM, MEM or PIP after coadministration of each concomitant drug with NAC were similar to those of administration of each concomitant drug alone. The PK parameter of each β-lactam tested showed the similar value both after administration of β-lactam alone and after concomitant administration with NAC. Based on these finding, it was confirmed that coadministration of each concomitant drug with NAC did not affect the PK of FEP, ATM, MEM and PIP. As for the safety, there was no serious adverse event, all of TEAEs reported were mild in severity and judged to be “not related”. Conclusion It was confirmed that single coadministration of NAC with FEP, ATM, MEM, or PIP did not affect the both PKs of NAC and β-lactams, and was safe and well-tolerated in Japanese healthy subjects. Disclosures Masayo Asano, BS, Meiji Seika Pharma Co., Ltd. (Employee) Hiroki Sato, BS, Meiji Seika Pharma Co., Ltd. (Employee) Jun Morita, PhD, Meiji Seika Pharma Co., Ltd. (Employee) Kazuya Ishiwata, MS, Meiji Seika Pharma Co., Ltd. (Employee) Kenichiro Kondo, PhD, Meiji Seika Pharma Co., Ltd. (Employee)