| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(Circulation. 2002;106:1943.)
© 2002 American Heart Association, Inc.
Clinical Investigation and Reports |
From the Department of Clinical Pharmacology (T.S., D.L., A.K., M.I., K.v.B.), University of Bonn, Germany; and Clinical Research (D.L.T., S.S., I.P.), Merck Research Laboratories, Rahway, NJ.
Correspondence to Prof Klaus von Bergmann, MD, Dept of Clinical Pharmacology, University of Bonn, Sigmund-Freud-Str. 25, 53105 Bonn/Germany. E-mail vonbergmann{at}uni-bonn.de
| Abstract |
|---|
|
|
|---|
Methods and Results The effect of ezetimibe (10 mg/d) on cholesterol absorption and synthesis, sterol excretion, and plasma concentrations of cholesterol and noncholesterol sterols was investigated in a randomized, double-blind, placebo-controlled, crossover study in 18 patients with mild to moderate hypercholesterolemia. Treatment periods lasted 2 weeks with an intervening 2-week washout period. Fractional cholesterol absorption rates averaged 49.8±13.8% on placebo and 22.7±25.8% on ezetimibe, indicating a reduction of 54% (geometric mean ratio; P< 0.001). Cholesterol synthesis increased by 89% from 931±1027 mg/d on placebo to 1763±1098 mg/d on ezetimibe (P<0.001), while the ratio of lathosterol-to-cholesterol, an indirect marker of cholesterol synthesis, was increased by 72% (P<0.001). Bile acid synthesis was insignificantly increased (placebo: 264±209 mg/d, ezetimibe: 308±184 mg/d; P=0.068). Mean percent changes from baseline for LDL and total cholesterol after ezetimibe treatment were -20.4% and -15.1%, respectively (P<0.001 for both), whereas campesterol and sitosterol were decreased by -48% and - 41%, respectively.
Conclusion In humans, ezetimibe inhibits cholesterol absorption and promotes a compensatory increase of cholesterol synthesis, followed by clinically relevant reductions in LDL and total cholesterol concentrations. Ezetimibe also reduces plasma concentrations of the noncholesterol sterols sitosterol and campesterol, suggesting an effect on the absorption of these compounds as well.
Key Words: ezetimibe cholesterol absorption cholesterol synthesis lathosterol plant sterols
| Introduction |
|---|
|
|
|---|
| Methods |
|---|
|
|
|---|
|
Patients
Eighteen patients from the outpatient clinic of the Department of Clinical Pharmacology, University of Bonn, participated in the study. Inclusion criteria for randomization were age between 18 and 55 years, body mass index [BMI=weight (kg)/height (m)2] between 19 and 30 kg/m2, plasma LDL cholesterol concentrations
130 mg/dL but
180 mg/dL, triglyceride concentrations below 250 mg/dL, and dietary cholesterol intake in the range of 200 to 500 mg/d based on a 7-day food record analysis during the run-in period. Patients receiving lipid-lowering drugs within 6 weeks of study entry, and those with a history of excessive alcoholic intake, diabetes or other endocrine disorders, diseases of the liver or gastrointestinal tract, or renal dysfunction were excluded by protocol. All patients were advised to avoid excess cholesterol intake and to keep their usual dietary habits throughout the trial and were provided instruction in recording their nutritional intake by an experienced nutritional scientist.
Cholesterol Absorption Measurements
Fractional cholesterol absorption was evaluated during the second week of each treatment period using the continuous feeding dual-isotope method using deuterated markers.11 For this purpose, patients received tracer capsules containing 3 mg [2H6] cholesterol and 3 mg [2H4] sitostanol (Medical Isotopes Inc) 3 times per day for 7 days during the second week of each treatment period (days 8 to 14 and days 36 to 42). Daily stool samples were collected over the final 4 days of each treatment period for measurement of fecal isotopic ratios by gas chromatography/mass spectrometry (GC-MS). Fractional cholesterol absorption was calculated from the fecal ratio of deuterium-labeled cholesterol and its bacterial degradation products coprostanol and coprostanone and deuterium-labeled sitostanol and from the ratio of deuterium-labeled cholesterol and sitostanol in the tracer capsules. Because coprostanone was not detectable in the fecal samples, only coprostanol was included into the calculation. The percentage absorption of cholesterol was calculated from the disappearance of cholesterol during the passage through the small intestine compared with sitostanol, which served as nonabsorbable flow marker by the following formula:
|
|
The cholesterol absorption rates were derived from the median of the 4 measurements during each treatment period.
Cholesterol and Bile Acid Synthesis
Fecal excretion of neutral and acidic sterols was measured from the same fecal samples (days 4 to 7) collected for cholesterol absorption using [2H4] sitostanol as nonabsorbable marker. Measurements were performed by gas-liquid chromatography in a modified form as described previously.12 Daily fecal excretion rates were calculated as ratios of neutral and acidic sterols to the [2H4] sitostanol in fecal samples multiplied by the daily intake of deuterated sitostanol. Net cholesterol synthesis was calculated as the sum of daily excretion of total fecal sterols minus the mean of dietary cholesterol intake. Dietary cholesterol intake was calculated from the last 7 days of the placebo run-in period and each of the treatment periods based on 7-day food diaries. Mean daily intake was computed using a nutrition database program (Prodi 4.5, WVG, Germany). Values for neutral and acidic sterol excretion as well as cholesterol synthesis were derived from the median of the 4 measurements during each period.
Plasma Lipids and Noncholesterol Sterols
Blood was drawn for plasma lipid and lipoprotein analysis in the morning after an overnight fast at the beginning and the end of each of the treatment periods. Baseline lipoprotein profiles were recorded after the placebo run-in period. Total cholesterol and triglycerides in serum were measured by enzymatic methods. High-density lipoprotein (HDL) cholesterol was determined in the supernatant after precipitation of apolipoprotein Bcontaining lipoproteins. Low-density lipoprotein (LDL) cholesterol was calculated by the method of Friedewald et al.13 Lathosterol, campesterol, and sitosterol were also determined from these blood samples using GC/MS as described previously using epicoprostanol as internal standard.14
Statistical Analysis
All data were analyzed in an intention-to-treat approach. An analysis of variance (ANOVA) model appropriate for a 2-period, 2-arm crossover design with terms for treatment, sequence, patient within sequence, and period was used to calculate differences between placebo and ezetimibe treatment using SAS statistic package (SAS Institute Inc). All parameters except plasma lipids and lipoproteins were log transformed to fit the model assumptions. If not otherwise stated, means were expressed as retransformed geometric means. Standard deviations were estimated from the ANOVA model. Percent differences between placebo and ezetimibe treatment were expressed as geometric mean ratios. Lipid parameters (total, LDL, and HDL cholesterol) were expressed as percent change from baseline to endpoint estimated from the LS means of the ANOVA model.
| Results |
|---|
|
|
|---|
Cholesterol Absorption and Synthesis
The results for dietary cholesterol intake, fractional cholesterol absorption rates, fecal excretion of neutral and acidic sterols, and total cholesterol synthesis are summarized in Table 1. Dietary cholesterol intake of all patients was in the range of 200 to 500 mg/d and remained constant in every subject throughout the study. Cholesterol absorption rates ranged from 24.9% to 74.7% on placebo and from 2.3% to 48.7% on ezetimibe. After 2 weeks of treatment, fractional cholesterol absorption was 22.7% on ezetimibe and 49.8% on placebo (P<0.001). Based on the geometric mean ratio, ezetimibe reduced fractional cholesterol absorption by 54% compared with placebo. No significant sequence or period effect was detected. Individual fractional cholesterol absorption rates are shown in Figure 2. In all but one patient, cholesterol absorption was lower during ezetimibe than placebo treatment, and in one subject the reduction was marginal (-2%). The fecal excretion of total neutral sterols increased by 72% during treatment with ezetimibe (P<0.001; Table 1). A small, but not significant, increase in acidic sterol excretion also was observed (P=0.068). Thus, total cholesterol synthesis was increased by 89% on ezetimibe relative to placebo (P<0.001).
|
|
Plasma Lipoproteins
Baseline mean LDL cholesterol was 142 mg/dL. After 2 weeks of treatment, the mean percent changes from baseline to endpoint were -20.4% (P<0.001) on ezetimibe and +1.9% (P=0.640) on placebo resulting in a -22.3% treatment difference (Table 2). Similar results were observed for total cholesterol with a baseline value of 220 mg/dL for both groups. The mean percent changes from baseline to endpoint were -15.1% (P<0.001) on ezetimibe and -1.9% (P=0.498) on placebo for a total treatment difference of -13.2% (P<0.001). Changes in HDL cholesterol and triglycerides were not significantly different for ezetimibe versus placebo (Table 2). There was a weak but not significant correlation between percent reduction in total cholesterol and percent change in cholesterol absorption (r=0.45; P=0.061).
|
Plasma Noncholesterol Sterols
Plasma lathosterol concentrations increased by 53% and the ratio of lathosterol-to-cholesterol (a marker of hepatic HMG-CoA reductase activity and total cholesterol synthesis) increased by 72% on ezetimibe (Table 3; P< 0.001 for both). Significant correlations between the lathosterol-to-cholesterol ratio and cholesterol synthesis rates were observed during both treatment periods (data not shown).
|
Treatment with ezetimibe lowered plasma concentrations of the noncholesterol plant sterols campesterol and sitosterol in every subject (Figures 3A and 3B). The mean reduction was -48% for campesterol and -41% for sitosterol (Table 3; P<0.001 for both). Similar results could also be observed for their ratios to cholesterol. The mean decreases were -41% for the campesterol-to-cholesterol ratio and -34% for the sitosterol-to-cholesterol ratio (Table 3; P<0.001 for both).
|
Safety
The tolerability of ezetimibe was excellent and there were no serious clinical adverse events or critical laboratory elevations (including aspartate or alanine aminotransferase elevations 3-fold greater than the upper limit of normal or creatinine phosphokinase elevations 10-fold greater than the upper limit of normal) during either placebo or ezetimibe treatment.
| Discussion |
|---|
|
|
|---|
Compared with animal experiments, the present study revealed a less extensive effect of ezetimibe on inhibition of cholesterol absorption in humans. Studies in cholesterol fed hamsters and rodents showed an inhibition of cholesterol absorption by 92% to 96% in a dose range of 1 to 10 mg/kg.5,15 Although these data are not comparable with the present study due to species differences, the dosage in the present study was 10 to 100 times lower. In comparison to other compounds, intestinal cholesterol absorption by ezetimibe was more pronounced than that observed for other known inhibitors of cholesterol absorption including neomycin and plant sterol and stanol esters in humans. Neomycin has been shown to reduce intestinal cholesterol absorption in a dose-dependent manner by 26% to 49%.1620 Treatment with high-dose plant sterols and stanols has been shown to lower cholesterol absorption by up to 45%,2123 but the maximal effects are observed under circumstances in which the active agents are delivered in fat carriers in conjunction with cholesterol meals.
In addition to effects on plasma cholesterol concentrations, ezetimibe produced a marked reduction in circulating levels of noncholesterol plant sterols. In fact, effects on plasma concentrations of campesterol and sitosterol were more pronounced than those on cholesterol. This difference may reflect different absorption rates for campesterol and sitosterol versus cholesterol23 and/or the fact that, unlike cholesterol, plant sterols cannot be synthesized endogenously.24 Indeed, the reduced cholesterol absorption was compensated by an increase in cholesterol synthesis as indicated by an increase in the fecal excretion of neutral sterols and the ratio of lathosterol-to-cholesterol in plasma. Because the ratio of lathosterol-to-cholesterol is an indicator for the hepatic HMG-CoA reductase activity25 and total cholesterol synthesis,26 it can be speculated that the increase in cholesterol synthesis is mainly due to de novo hepatic cholesterol synthesis. Although the observed increase in the acidic sterol excretion was small and marginal, we cannot exclude the possibility that during long-term treatment, ezetimibe might lead to a slight increase in bile-acid synthesis.
The observed increase in hepatic cholesterol synthesis might explain the favorable effects of coadministering ezetimibe and statins.27 Several recent trials (currently either published in abstract form or unpublished) have shown that coadministration of ezetimibe with statins produces an incremental reduction of LDL cholesterol in the range of 12% to 15% independent of kind and dose of the coadministered statin.2834 When ezetimibe was added to on-going statin therapy, LDL cholesterol was incrementally reduced by 21.5% (relative to on-statin baseline values) compared with placebo.35 Thus, because statins can reduce the compensatory increase in the hepatic cholesterol synthesis induced by ezetimibe, the combination of ezetimibe and statins results in an incremental lowering of LDL cholesterol concentrations.
The inhibitory effects of ezetimibe were characterized by considerable interindividual variation. The basis of these variations cannot be determined from the present study but potentially could involve intrinsic differences in responsiveness to ezetimibe. Importantly, variations in cholesterol absorption did not correlate significantly with changes in total cholesterol and did not correlate with variations in LDL cholesterol reductions after ezetimibe treatment, likely due to the influence of other factors, including compensatory changes in cholesterol synthesis.
In conclusion, 2 weeks of treatment with ezetimibe at 10 mg/d produced a 54% inhibition of cholesterol absorption in mildly to moderately hypercholesterolemic subjects. This was associated with reductions in LDL and total cholesterol and plant sterol concentrations and a increase in endogenous cholesterol synthesis.
| Acknowledgments |
|---|
| Footnotes |
|---|
Received June 10, 2002; revision received July 30, 2002; accepted July 30, 2002.
| References |
|---|
|
|
|---|
This article has been cited by other articles:
![]() |
S. Helske, T. Miettinen, H. Gylling, M. Mayranpaa, J. Lommi, H. Turto, K. Werkkala, M. Kupari, and P. T. Kovanen Accumulation of cholesterol precursors and plant sterols in human stenotic aortic valves J. Lipid Res., July 1, 2008; 49(7): 1511 - 1518. [Abstract] [Full Text] [PDF] |
||||
![]() |
O. Weingartner, D. Lutjohann, S. Ji, N. Weisshoff, F. List, T. Sudhop, K. von Bergmann, K. Gertz, J. Konig, H.-J. Schafers, et al. Vascular effects of diet supplementation with plant sterols. J. Am. Coll. Cardiol., April 22, 2008; 51(16): 1553 - 1561. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. Tavridou, L. Kaklamanis, A. Papalois, A. P. Kourounakis, E. A. Rekka, P. N. Kourounakis, A. Charalambous, and V. G. Manolopoulos EP2306 [2-(4-Biphenyl)-4-methyl-octahydro-1,4-benzoxazin-2-ol, hydrobromide], A Novel Squalene Synthase Inhibitor, Reduces Atherosclerosis in the Cholesterol-Fed Rabbit J. Pharmacol. Exp. Ther., December 1, 2007; 323(3): 794 - 804. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. S Sampalis, S. Bissonnette, R. Habib, S. Boukas, and for the Ezetrol Add-On Investigators Reduction in Estimated Risk for Coronary Artery Disease After Use of Ezetimibe with a Statin Ann. Pharmacother., September 1, 2007; 41(9): 1345 - 1351. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Piorkowski, S. Fischer, C. Stellbaum, M. Jaster, P. Martus, A. J. Morguet, H.-P. Schultheiss, and U. Rauch Treatment With Ezetimibe Plus Low-Dose Atorvastatin Compared With Higher-Dose Atorvastatin Alone: Is Sufficient Cholesterol-Lowering Enough to Inhibit Platelets? J. Am. Coll. Cardiol., March 13, 2007; 49(10): 1035 - 1042. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. J. Clarenbach, M. Reber, D. Lutjohann, K. von Bergmann, and T. Sudhop The lipid-lowering effect of ezetimibe in pure vegetarians J. Lipid Res., December 1, 2006; 47(12): 2820 - 2824. [Abstract] [Full Text] [PDF] |
||||
![]() |
E. J. Westover, X. Lin, T. E. Riehl, L. Ma, W. F. Stenson, D. F. Covey, and R. E. Ostlund Jr. Rapid transient absorption and biliary secretion of enantiomeric cholesterol in hamsters J. Lipid Res., November 1, 2006; 47(11): 2374 - 2381. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. K Nies, A. A Cymbala, S. L Kasten, D. G Lamprecht, and K. L Olson Complementary and Alternative Therapies for the Management of Dyslipidemia Ann. Pharmacother., November 1, 2006; 40(11): 1984 - 1992. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. J. Tremblay, B. Lamarche, J. S. Cohn, J.-C. Hogue, and P. Couture Effect of Ezetimibe on the In Vivo Kinetics of ApoB-48 and ApoB-100 in Men With Primary Hypercholesterolemia Arterioscler. Thromb. Vasc. Biol., May 1, 2006; 26(5): 1101 - 1106. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. P. Radermecker and A. J. Scheen Serum Plant Sterols and Atherosclerosis: Is There a Place for Statin-Ezetimibe Combination? J. Am. Coll. Cardiol., April 4, 2006; 47(7): 1496 - 1497. [Full Text] [PDF] |
||||
![]() |
L. Yu, S. Bharadwaj, J. M. Brown, Y. Ma, W. Du, M. A. Davis, P. Michaely, P. Liu, M. C. Willingham, and L. L. Rudel Cholesterol-regulated Translocation of NPC1L1 to the Cell Surface Facilitates Free Cholesterol Uptake J. Biol. Chem., March 10, 2006; 281(10): 6616 - 6624. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. Jakulj, M. D. Trip, T. Sudhop, K. von Bergmann, J. J. P. Kastelein, and M. N. Vissers Inhibition of cholesterol absorption by the combination of dietary plant sterols and ezetimibe: effects on plasma lipid levels J. Lipid Res., December 1, 2005; 46(12): 2692 - 2698. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. During, H. D. Dawson, and E. H. Harrison Carotenoid Transport Is Decreased and Expression of the Lipid Transporters SR-BI, NPC1L1, and ABCA1 Is Downregulated in Caco-2 Cells Treated with Ezetimibe J. Nutr., October 1, 2005; 135(10): 2305 - 2312. [Abstract] [Full Text] [PDF] |
||||
![]() |
G D Kolovou, K K Anagnostopoulou, and D V Cokkinos Pathophysiology of dyslipidaemia in the metabolic syndrome Postgrad. Med. J., June 1, 2005; 81(956): 358 - 366. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. F.H. Stalenhoef Management of mixed hyperlipidaemia Eur. Heart J., May 1, 2005; 26(9): 856 - 857. [Full Text] [PDF] |
||||
![]() |
J. J. Repa, S. D. Turley, G. Quan, and J. M. Dietschy Delineation of molecular changes in intrahepatic cholesterol metabolism resulting from diminished cholesterol absorption J. Lipid Res., April 1, 2005; 46(4): 779 - 789. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. A. Spratt and M. A. Denke Utility of Currently Available Modes of Therapy in Reaching Lipid Goals J Am Osteopath Assoc, September 1, 2004; 104(9_suppl): 14S - 16S. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. J. Vaughan and A. M. Gotto Jr Update on Statins: 2003 Circulation, August 17, 2004; 110(7): 886 - 892. [Full Text] [PDF] |
||||
![]() |
H. R. Davis Jr., L.-j. Zhu, L. M. Hoos, G. Tetzloff, M. Maguire, J. Liu, X. Yao, S. P. N. Iyer, M.-H. Lam, E. G. Lund, et al. Niemann-Pick C1 Like 1 (NPC1L1) Is the Intestinal Phytosterol and Cholesterol Transporter and a Key Modulator of Whole-body Cholesterol Homeostasis J. Biol. Chem., August 6, 2004; 279(32): 33586 - 33592. [Abstract] [Full Text] [PDF] |
||||
![]() |
G. Salen, K. von Bergmann, D. Lutjohann, P. Kwiterovich, J. Kane, S.B. Patel, T. Musliner, P. Stein, B. Musser, and the Multicenter Sitosterolemia Study Group Ezetimibe Effectively Reduces Plasma Plant Sterols in Patients With Sitosterolemia Circulation, March 2, 2004; 109(8): 966 - 971. [Abstract] [Full Text] [PDF] |
||||
![]() |
E. Sehayek Genetic regulation of cholesterol absorption and plasma plant sterol levels: commonalities and differences J. Lipid Res., November 1, 2003; 44(11): 2030 - 2038. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. Berglund and D. Hyson Cholesterol Absorption and the Metabolic Syndrome: A New Look at an Old Area Arterioscler. Thromb. Vasc. Biol., August 1, 2003; 23(8): 1314 - 1316. [Full Text] [PDF] |
||||
![]() |
P. O. Kwiterovich Jr., S. C. Chen, D. G. Virgil, A. Schweitzer, D. R. Arnold, and L. E. Kratz Response of obligate heterozygotes for phytosterolemia to a low-fat diet and to a plant sterol ester dietary challenge J. Lipid Res., June 1, 2003; 44(6): 1143 - 1155. [Abstract] [Full Text] [PDF] |
||||
![]() |
V. F Mauro and C. E Tuckerman Ezetimibe for Management of Hypercholesterolemia Ann. Pharmacother., June 1, 2003; 37(6): 839 - 848. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. van Heek and H. Davis Pharmacology of ezetimibe Eur. Heart J. Suppl., December 1, 2002; 4(suppl_J): J5 - J8. [Abstract] [PDF] |
||||
![]() |
C.M. Ballantyne Ezetimibe: efficacy and safety in clinical trials Eur. Heart J. Suppl., December 1, 2002; 4(suppl_J): J9 - J18. [Abstract] [PDF] |
||||
| ||||||||