Identification of Novel Metabolic Pathways of Pioglitazone in Hepatocytes: <i>N</i>-Glucuronidation of Thiazolidinedione Ring and Sequential Ring-Opening Pathway
作者:Minoru Uchiyama、Thomas Fischer、Juergen Mueller、Minoru Oguchi、Naotoshi Yamamura、Hiroko Koda、Haruo Iwabuchi、Takashi Izumi
DOI:10.1124/dmd.109.031583
日期:2010.6
The metabolism of [14C]pioglitazone was studied in vitro in incubations with freshly isolated human, rat, and monkey hepatocytes. Radioactivity detection high-performance liquid chromatography analysis of incubation extracts showed the detection of 13 metabolites (M1–M13) formed in incubations with human hepatocytes. An identical set of metabolites (M1–M13) was also detected in monkey hepatocytes. However, in rat hepatocytes, M1 through M3, M5 through M7, M9 through M11, and M13 were also detected, but M4, M8, and M12 were not detected. The structures of the metabolites were elucidated by liquid chromatography/tandem mass spectrometry using electrospray ionization. Novel metabolites of pioglitazone detected using these methods included thiazolidinedione ring-opened methyl sulfoxide amide (M1), thiazolidinedione ring-opened N -glucuronide (M2), thiazolidinedione ring-opened methyl sulfone amide (M3), thiazolidinedione ring N -glucuronide (M7), thiazolidinedione ring-opened methylmercapto amide (M8), and thiazolidinedione ring-opened methylmercapto carboxylic acid (M11). In summary, based on the results from these studies, two novel metabolic pathways for pioglitazone in hepatocytes are proposed to be as follows: 1) N -glucuronidation of the thiazolidinedione ring of pioglitazone to form M7 followed by hydrolysis to M2, and methylation of the mercapto group of the thiazolidinedione ring-opened mercapto carboxylic acid to form M11; and 2) methylation of the mercapto group of the thiazolidinedione ring-opened mercapto amide to form M8, oxidation of M8 to form M1, and oxidation of M1 to form M3.
研究了[14C]吡格列酮在体外与新鲜分离的人类、大鼠和猴子肝细胞孵育过程中的代谢情况。对孵育提取物的放射性检测高效液相色谱分析显示,在与人类肝细胞的孵育过程中检测到了 13 种代谢物(M1-M13)。在猴子肝细胞中也检测到了一组相同的代谢物(M1-M13)。不过,在大鼠肝细胞中也检测到了 M1 至 M3、M5 至 M7、M9 至 M11 和 M13,但没有检测到 M4、M8 和 M12。这些代谢物的结构是通过电喷雾离子化液相色谱/串联质谱法阐明的。噻唑烷二酮环开甲基砜酰胺(M3)、噻唑烷二酮环开 N-葡萄糖醛酸(M7)、噻唑烷二酮环开甲基巯基酰胺(M8)和噻唑烷二酮环开甲基巯基羧酸(M11)。总之,根据这些研究结果,提出了吡格列酮在肝细胞中的两种新的代谢途径如下:1) 吡格列酮的噻唑烷二酮环的 N-葡萄糖醛酸化形成 M7,然后水解形成 M2,噻唑烷二酮环开巯基羧酸的巯基甲基化形成 M11;以及 2) 噻唑烷二酮环开巯基酰胺的巯基甲基化形成 M8,M8 氧化形成 M1,M1 氧化形成 M3。