Abstract
Disposition of the lipid-lowering agent ezetimibe (EZ) and its glucuronide (GLUC), which is mainly formed by UDP-glucuronosyltransferase (UGT) 1A1, is influenced by the intestinal efflux transporters P-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP) 2. To evaluate the role of Mrp2 in overall disposition and pharmacodynamic effects of EZ, wild-type and Mrp2-deficient (TR-negative) Lewis.1W rats (eight males each) fed with a cholesterol-enriched diet were orally treated with 5 mg/kg EZ for 14 days. EZ and GLUC in serum, urine, and feces, and cholesterol, campesterol, and sitosterol in serum, were assayed using liquid chromatography (LC)-tandem mass spectrometry and LC-mass spectrometry methods, respectively. Gene expression of Bsep (bile salt exporting pump), multidrug resistance (Mdr) 1a, Mdr1b, Mrp2, Mrp3, Ntcp (sodium taurocholate co-transporting polypeptide), organic anion transporting polypeptides (Oatp) 1, 2, 4, and Ugt1a1 was quantified in several tissues using real-time reverse transcription-polymerase chain reaction. Mrp2 deficiency resulted in lower serum levels and fecal excretion of EZ (1.4 ± 0.4 versus 3.1 ± 1.1 ng/ml; 115 ± 48 versus 361 ± 102 μg/day, both p < 0.01), whereas serum concentrations of GLUC were manyfold increased compared with wild type (196 ± 76 versus 23 ± 25 ng/ml; p < 0.01), associated with elevated renal excretion and decreased intestinal clearance (7.8 ± 3.1 versus 0.4 ± 0.4 μg/day, p < 0.01; 0.3 ± 0.3 versus 15 ± 17 ml/min; p < 0.05). The sterol-lowering effect of EZ was reduced in correlation to EZ serum levels (cholesterol: r = 0.449, p = 0.093; campesterol: r = 0.717, p = 0.003; sitosterol: r = 0.507, p = 0.054), whereas GLUC was inversely correlated (r = -0.743, p = 0.002; r =-0.768, p = 0.001; r =-0.634, p = 0.011). Disposition of EZ may have been additionally influenced by hepatic P-gp, Mrp3, and Ugt1a1, which were expressed significantly higher in Mrp2-deficient rats. Mrp2 deficiency in rats is associated with decreased sterol-lowering effect of ezetimibe, obviously caused by lower intestinal clearance of the glucuronide and decreased enterosystemic and enterohepatic recycling of the parent ezetimibe to the intestinal Niemann-Pick C 1-like 1 sterol-uptake compartment.
Footnotes
-
The work was supported by the German Federal Ministry for Education and Research Grant 01ZZ0403 and an institutional research grant of MSD Sharp and Dohme.
-
doi:10.1124/jpet.106.104018.
-
ABBREVIATIONS: NPC1L1, Niemann-Pick C 1-like 1; UGT, UDP-glucuronosyltransferase; MRP/Mrp, multidrug resistance-associated protein; P-gp, P-glycoprotein; PXR, pregnane X receptor; CAR, constitutive androstane receptor; Mdr, multidrug resistance; TR-, Mrp2-deficient; Bsep, bile salt exporting pump; Ntcp, sodium taurocholate transporting polypeptide; OATP/Oatp, organic anion transporting polypeptide; TBST, Tris-buffered saline containing 0.05% Tween 20; LC-MS, liquid chromatography-mass spectrometry; CL, clearance; Lew.1w, Lewis.1w.
- Received March 3, 2006.
- Accepted June 8, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|