Browsing by Subject "enzymes"

Statins are a commonly used group of drugs that reduce the cholesterol levels in blood and have been shown to reduce cardiovascular morbidity and mortality. However, a considerable percentage of patients experience adverse effects during statin treatment. Statin adverse effects have been associated with genetic polymorphisms and drug-drug interactions that affect the elimination and active transport of these drugs. A more comprehensive knowledge of statin metabolism may be a step towards better management of statin treatments. Statin metabolism both in vivo and in vitro has been subject of study for years. In vitro incubation conditions may considerably affect the observed clearance, and results obtained with different methods or in different laboratories may not be directly comparable to each other. No single in vitro study on a wide panel of statins has previously been conducted. Six statins and some of their metabolites, fourteen compounds in total, were included in the study. The intrinsic clearance (CLint) of these molecules was investigated in vitro on human liver microsomes (HLM) and a panel of eleven cytochrome P450 (CYP) enzymes recombinantly expressed in E. coli. Observed CLint values for each compound in HLM and for each compound-CYP pair with observed depletion were calculated. The percentual contributions of each CYP enzyme to the metabolism of the compounds was calculated. The results obtained with recombinant CYP enzymes (rcCYP) were complemented with studies on HLM with specific chemical inhibitors of CYP enzymes. In this study the metabolism of statin lactones seemed to be faster than the metabolism of the corresponding statin acids. Atorvastatin lactone, 2-hydroxy atorvastatin lactone, 4-hydroxy atorvastatin lactone and simvastatin were extensively metabolized. Atorvastatin, 2-hydroxy atorvastatin, 3R,5S-fluvastatin, 3S,5R-fluvastatin, pitavastatin lactone and simvastatin acid showed intermediate metabolism. 4-hydroxy atorvastatin, pitavastatin, pravastatin and rosuvastatin rates of metabolism were below quantification limit. CYP3A4 had a major role in the metabolism of atorvastatin and its metabolites, simvastatin and simvastatin acid. CYP3A4 also had activity towards pitavastatin lactone. CYP2C9 had a high activity towards both 3R,5S-fluvastatin and 3S,5R-fluvastatin. CYP2D6 may play a part in the metabolism of pitavastatin lactone. CYP2C8 may have some activity towards simvastatin and simvastatin acid. The data is mostly in agreement with previous in vitro and in vivo studies regarding both the metabolism rate of statins and the contributions by different CYP enzymes to the metabolism of statins. Due to the screening nature of the study and some methodological constraints, these data should be considered as preliminary and require confirmation in further studies.