Methyl-hydroxylation and subsequent oxidation to produce carboxylic acid is the major metabolic pathway of tolbutamide in chimeric TK-NOG mice transplanted with human hepatocytes

Tolbutamide is an oral anti-hyperglycaemic agent used to treat non-insulin-dependent diabetes mellitus with species-dependent metabolic profiles. In this study, we investigated tolbutamide metabolism in chimeric TK-NOG mice transplanted with human hepatocytes (humanised-liver mice).Substantial 4-hydroxytolbutamide and 4-carboxytolbutamide production was observed in hepatocytes from humanised-liver mice (Hu-Liver cells) and humans, whereas 4-carboxytolbutamide production was not detected in mouse hepatocytes. In Hu-Liver cells, 4-hydroxytolbutamide formation was inhibited by sulfaphenazole (CYP2C9 inhibitor), whereas 4-carboxytolbutamide formation was inhibited by raloxifene/ethinyloestradiol (aldehyde oxidase inhibitor) and disulfiram (aldehyde dehydrogenase inhibitor).After a single oral dose of tolbutamide (10 mg/kg), the plasma levels of 4-carboxytolbutamide and