Microdose pharmacogenetic study of ¹4C-tolbutamide in healthy subjects with accelerator mass spectrometry to examine the effects of CYP2C9∗3 on its pharmacokinetics and metabolism.

Microdose study enables us to understand the pharmacokinetic profiles of drugs in humans prior to the conventional clinical trials. The advantage of microdose study is that the unexpected pharmacological/toxicological effects of drugs caused by drug interactions or genetic polymorphisms of metabolic enzymes/transporters can be avoided due to the limited dose. With a combination use of accelerator mass spectrometry (AMS) and (14)C-labaled compounds, the pharmacokinetics of both parent drug and its metabolites can be sensitively monitored. Thus, to demonstrate the usability of microdose study with AMS for the prediction of the impact of genetic polymorphisms of CYP enzyme on the pharmacokinetics of unchanged drugs and metabolites, we performed microdose pharmacogenetic study using tolbutamide as a CYP2C9 probe drug. A microdose of (14)C-tolbutamide (100 µg) was administered orally to healthy volunteers with the CYP2C9(∗)1/(∗)1 or CYP2C9(∗)1/(∗)3 diplotype. Area under the plasma concentration-time curve for the (14)C-radioactivity, determined by AMS, or that for the parent drug, determined by liquid chromatography/mass spectrometry, was about 1.6 times or 1.7 times greater in the CYP2C9(∗)1/(∗)3 than in the CYP2C9(∗)1/(∗)1 group, which was comparable to the previous reports at therapeutic dose. In the plasma and urine, tolbutamide, carboxytolbutamide, and 4-hydroxytolbutamide were detected and practically no other metabolites could be found in both diplotype groups. The fraction of metabolites in plasma radioactivity was slightly lower in the CYP2C9(∗)1/(∗)3 group. Microdose study can be used for the prediction of the effects of genetic polymorphisms of enzymes on the pharmacokinetics and metabolic profiles of drugs with minimal care of their pharmacological/toxicological effects.

A dried tofu-supplemented diet affects mRNA expression of inflammatory cytokines in human blood.

In order to develop a new model of diet research, blood was drawn from 12 adult volunteers for 3 wk on regular diets as controls, and for a subsequent 3 wk supplemented with 18.5 g of freeze-dried tofu (Koya tofu) every day. Triplicate aliquots of 0.06 mL each of whole blood were stimulated ex vivo with phytohemagglutinin (PHA)-P, heat aggregated human IgG (HAG), lipopolysaccharide (LPS), zymosan A, and anti-T cell receptor (TCR) monoclonal antibody to activate specific subsets of leukocytes, then the levels of various inflammatory cytokine mRNA were quantified by real time PCR. Koya tofu significantly (p<0.05) augmented the fold increase of PHA-induced tumor necrosis factor superfamily (TNFSF) 15, IL6, and IL8, HAG-induced TNFSF15 and IL8, LPS-induced IL6 and IL8, zymosan-induced TNFSF15, IL6 and IL8, and TCR-induced TNFSF2 in comparison to the regular diet. Such increase was due to the reduction of baseline mRNA expression, not the enhancement of mRNA induction after specific stimulations. Six (TNFSF15), 4 (IL6), and 3 (IL10) subjects showed significant reduction of baseline mRNA during the Koya tofu diet compared to that of the control diet. Despite large individual-to-individual and day-to-day variation of mRNA, the method employed in this study was sensitive enough to identify statistically significant results as a group as well as on an individual basis, which will be a foundation for tailored diet in the future. The results also indicated that Koya tofu had a power to alter mRNA expression in leukocytes, and TNFSF15, IL6, and IL10 would be biomarkers for soy.