Permanent URL to this publication: http://dx.doi.org/10.5167/uzh-25549
Muschler, E; Lal, J; Jetter, A; Rattay, A; Zanger, U; Zadoyan, G; Fuhr, U; Kirchheiner, J (2009). The role of human CYP2C8 and CYP2C9 variants in pioglitazone metabolism in vitro. Basic & Clinical Pharmacology & Toxicology, 105(6):374-379.
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The cytochrome P450 enzyme CYP2C8 appears to have a major role in pioglitazone metabolism. The present study was conducted to further clarify the role of individual CYPs and of the CYP2C8/9 polymorphisms in the primary metabolism of pioglitazone in vitro. Pioglitazone (2-400 microM) was incubated with isolated cytochrome P450 enzymes or human liver microsomes, some of them carrying either the CYP2C8*3/*3 genotype (and also the CYP2C9*2/*2 genotype) or the CYP2C8*1/*1 genotype (five samples each). The formation of the primary pioglitazone metabolite M-IV was monitored by HPLC. Enzyme kinetics were estimated assuming a single binding site. Mean intrinsic clearance of pioglitazone to the metabolite M-IV was highest for CYP2C8 and CYP1A2 with 58 pmol M-IV/min/nmol CYP P450/microM pioglitazone each, 53 for CYP2D6*1, 40 for CYP2C19*1, and 34 for CYP2C9*2, respectively. CYP2A6, CYP2B6, CYP2C9*1, CYP2C9*3, CYP2E1, CYP3A4 and CYP3A5 did not form quantifiable amounts of M-IV. CYP2C8*1/*1 microsomes (25 +/- 4 pmol M-IV/min/mg protein/muM pioglitazone) showed lower intrinsic clearance of pioglitazone than CYP2C8*3/*3 microsomes (35 +/- 9, p = 0.04). In all samples, metabolite formation showed substrate inhibition, while pioglitazone did not inhibit CYP2C8-mediated paclitaxel metabolism. CYP2C8, CYP1A2 and CYP2D6 are major CYPs forming M-IV in vitro. The higher activity of CYP2C8*3/CYP2C9*2 microsomes may result from a contribution of CYP2C9*2, or from differences in CYP2C8 expression. The evidence for substrate-specific inhibitory effects of pioglitazone on CYP2C-mediated metabolism needs to be tested in further studies.
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|Item Type:||Journal Article, refereed, original work|
|Communities & Collections:||04 Faculty of Medicine > University Hospital Zurich > Clinic for Clinical Pharmacology and Toxicology|
|Dewey Decimal Classification:||610 Medicine & health|
|Deposited On:||10 Dec 2009 12:34|
|Last Modified:||28 Nov 2013 01:13|
|Additional Information:||The definitive version is available at www.blackwell-synergy.com|
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