Effects of Statin and Ezetimibe Association on Kinetics of Artificial Chilomicrons
Condition: Coronary Heart Disease
MeSH terms: Heart Diseases; Coronary Disease; Coronary Artery Disease; Myocardial Ischemia
Study type: Interventional
Phase: Phase 4

Summary: 
      Effects of statin and ezetimibe association on kinetics of artificial chylomicrons in men
      with stable coronary heart disease (CHD).

      Background:

      The rate (kinetics) of chylomicrons removal from circulation have been correlated with the
      incidence and severity of atherosclerotic lesions; a number of studies demonstrated lower
      plasmatic clearance of chylomicrons in patients with CHD compared to patients without this
      condition. It was also demonstrated a correlation among LDL-C levels and removal of
      chylomicrons remnants by a technique employing artificial chylomicrons.

      The investigators also know that higher doses of more potent statins are more effective in
      chylomicrons removal than lower doses or less potent statins; nevertheless, the effect of the
      isolated use of statin has not been completely studied up to now.

      Study design:

      The investigators propose to study 26 outpatients volunteers with chronic CHD, followed at
      the Heart Institute - INCOR - of the School of Medicine, University of São Paulo.

      Following a period of six weeks of washout from any cholesterol reducer, the kinetics of
      chylomicrons removal by a technique of emulsion of radiolabeled artificial chylomicrons will
      be evaluated. Lipid fractions, hepatic enzymes and CK will be measured. Initially patients
      will be randomly allocated to receive simvastatin 20 mg /day (n= 13) or ezetimibe 10 mg/day
      (n=13) for six weeks. At the end of this period, kinetics of chylomicrons removal and
      laboratorial measurements will be repeated (Period 1).

      In the next period (Period 2) patients will receive simvastatin 20 mg/ ezetimibe 10 mg (n=13)
      or simvastatin 80 mg (n=13) for additional six weeks; at the end of this period, the
      evaluations will be repeated (third and last evaluation).

      The aim of this study is to further understand chylomicrons metabolism in patients with
      chronic coronary disease receiving cholesterol reducers at different dosage regimes.
    

Detailed description: 
      1-INTRODUCTION:

      1.1.Chylomicron metabolism: Chylomicrons are particles formed in the postprandial period and
      are responsible for transporting blood lipids originating in the diet. These lipoproteins are
      formed mostly by a core of triglycerides (about 90% of its weight) and small amounts of
      vitamins and cholesterol esters, surrounded by a phospholipid monolayer. Its protein portion,
      ie apolipoproteins (apo) remain adhered to the surface of chylomicrons and do not exceed 2%
      of their total weight, the most common Apo E, CII and CIII, which modulate the activity of
      lipolytic enzymes or act as ligands for cell receptors.

      In the circulation, chylomicrons bind to the endothelial surface of capillaries and
      triglyceride hydrolysis occurs by the action of lipoprotein lipase (LPL), thereby releasing
      fatty acids and glycerol to the surrounding cells, thus facilitating their absorption and
      accumulation in various tissues, especially adipose and muscle. The action of lipase is
      facilitated by apo CII on the particle surface . This mechanism is extremely important for
      the transit of energy in the body After this initial phase, the chylomicron remnants, smaller
      and depleted of triglycerides, are kidnapped in the Disse space and bind to receptors via the
      hepatic apolipoprotein E. Among these the investigators may mention the very LDL receptors
      (receptor B / E) and receiver RLP (receptor related protein in LDL). Importantly, apo B48,
      the main component of chylomicrons and remnants apoprotéico, has only a structural function.
      Chylomicrons and VLDL share common catabolic pathways regarding LPL and at least in part on
      the mechanisms of cellular uptake.

      Within the classes of lipoproteins, chylomicrons to more rapid removal of plasma, and its
      half life of about 15 minutes in healthy men. The speed (kinetic) removal of chylomicrons
      from the circulation has been correlated with the incidence and severity of atherosclerotic
      injury. Several studies showed lower plasma clearance of chylomicrons in patients with
      coronary artery disease compared to individuals without atherosclerosis. These findings are
      found even in normolipemic subjects. Chylomicrons participate in the atherosclerotic process
      by the generation of foam cells by direct deposition of those remaining in the subendothelial
      space of arterial wall, and also interference with the reverse transport of colestero. Thus
      treatments that reduce the plasma concentration of chylomicrons by accelerating its
      catabolism plasma could be used to prevent atherosclerosis.

      Among the methods used to evaluate the plasma kinetics of chylomicron, the investigators
      bring the lipid emulsion similar to chylomicrons labeled with radioisotopes. They offer an
      integrated vision and clear steps of the catabolism of chylomicrons in plasma. Several
      studies have shown that the kinetics of chylomicron is altered in patients with dyslipidemia
      and / or coronary artery disease (CAD). Defects were found both in lipolysis and the removal
      of chylomicron remnants, and in CAD patients these process were slowed5. Other studies have
      also shown that altered kinetics of chylomicrons is a marker of angiographic progression and
      a more severe course of CAD.

      Among the lipid-lowering drugs, statins are the more potent and safe drugs in reducing plasma
      levels of LDL, leading to decreased LDL cholesterol by 18-55%. They inhibit the
      hydroxy-methyl-glutaryl coenzyme A reductase (HMGCoA-A reductase), which acts on the
      synthesis of cholesterol. The enzyme inhibition results in decreased intracellular production
      of cholesterol by the liver, which leads to increased expression of LDL hepatic receptor,
      which increases the removal of LDL from the circulation.

      The effects of statins on clinical events were studied in several placebo controlled trials
      randomizing more than 90,000 patients for statin therapy or placebo for 3-5 years time. These
      studies showed consistently clinical benefit of statins, including reduction of
      cardiovascular morbidity and mortality, overall mortality, coronary revascularization
      procedures, and stroke, as demonstrated in a recent meta-analysis. In this group of drugs the
      investigators find Simvastatin, drug of low cost and high efficacy in reducing cardiovascular
      events as demonstrated in the study 4S.

      Studies have shown that increased expression of LDL receptors in the liver caused by statins
      leads to increased hepatic uptake of chylomicron artificial emulsions. In this context, it
      has been demonstrated previously increased plasma removal of chylomicron remnants in patients
      with coronary disease treated with pravastatin. Likewise, different doses of atorvastatin
      (10mg and 40mg) were evaluated in relation to intra-vascular metabolism and plasma kinetics
      of chylomicron emulsion in subjects with dyslipidemia. It was demonstrated that atorvastatin
      significantly accelerates the removal of chylomicron slowed characteristic of these patients,
      a dose-dependent, reducing the atherogenic potential of these triglyceride-rich particles in
      circulation.

      Ezetimibe, a new cholesterol absorption inhibitor, emerges as a tool for controlling
      cholesterol. The drug acts by inhibiting the absorption of dietary cholesterol and bile in
      the brush border of intestinal epithelium without affecting the absorption of triglycerides
      and vitamins. Moreover, the glucuronidated ezetimibe undergoes enterohepatic recirculation,
      repeatedly returning the drug to its site of action. Recent studies suggest that NPC1L1
      (Nieman-Pick C1 Like 1 protein) has a critical role in intestinal cholesterol absorption,
      being established as a direct target for the action ezetimibe18.

      Results of several studies in various models have demonstrated the lipid-lowering properties
      of ezetimibe as monotherapy or in combination with statins. In humans, ezetimibe at a dose of
      10mg per day reduces the level of LDL by 12-14%. However, when combined with ezetimibe
      statins show its therapeutic potential, because its association with low doses of the latter
      presents lowering effects similar to the use of maximal doses of those statins. Thus the
      association of low doses of statins with ezetimibe may be an alternative to progressive
      titration of statin therapy. This would be due to the fact that the association by reducing
      the concentration of an intense intra-hepatic cholesterol, increase the expression of LDL
      receptors on the cell membrane of hepatocytes. This fact leads to a higher removal of plasma
      lipoproteins that bind to these receptors. Recently it was shown that the isolated use of
      ezetimibe increases the plasma clearance of lipoproteins containing apo B100 (and VLDL
      remnants and LDL), without however affecting the removal of containing apo B48 (chylomicron
      remnants). To date, no published study that evaluated the association ezetimibe statin on the
      kinetics of plasma chylomicrons in research done in medline.

      2.RATIONALE: In literature there are already several studies that show that the plasma
      removal of chylomicron is reduced in subjects with coronary atherosclerosis and that these
      changes are correlated with greater clinical and angiographic progression of disease.

      Therapy with statins in several different schemes proved effective in increasing the kinetics
      of chylomicron removal in subjects with coronary artery disease, and this effect is
      dose-dependent. This fact can be explained by the finding that there was an inverse
      correlation between the plasma clearance of chylomicron remnants and plasma concentrations of
      LDL-cholesterol. However, to date there is still not clear what the effects of ezetimibe,
      used alone or in combination with statins, on the chylomicrons. Another aspect to be
      evaluated is the comparison of titration of statin versus the effects of ezetimibe and
      statins in their initial doses of chylomicrons, also not previously evaluated

      3.METHODS: The study included 30 patients previously diagnosed with stable chronic coronary
      ischemia in clinical follow-up at the outpatient clinic of the Unit for Chronic Coronary
      Disease, Heart Institute / INCOR-FMUSP.

      After the initial suspension of statin therapy for 6 weeks (washout), patients were
      randomized into three groups: 12 patients (group 1) treatment with simvastatin 20mg/day, 13
      patients (group 2) to therapy with ezetimibe 10mg / day and 5 patients for use of simvastatin
      20 mg / day (group 3). In this phase, patients were treated with the drug of choice for 06
      weeks and assessed for chylomicron kinetics before and after treatment.

      In a second phase, patients received lipid-lowering therapy for optimization of treatment
      with simvastatin 80 mg / day (group 1) or simvastatin 20 mg / day and ezetimibe 10 mg / day
      (group 2 and 3) for 6 weeks. Reassessment of the kinetics of chylomicron was held at the end
      of the second phase.

      Data were analyzed kinetics of chylomicrons baseline (without lipid-lowering therapy for a
      minimum of 6 weeks) after standard-dose monotherapy (first phase) and optimized combination
      therapy with statins in maximum therapeutic dose or combination of statin and ezetimibe
      (second phase) in patients with established coronary disease.

      Biochemical analysis as well as evaluations of the kinetics of chylomicron were funded by
      FAPESP No. 0408048-3 entitled "Out of free cholesterol from lipoprotein particles and
      deposition of cholesterol in the arterial wall: a new mechanism of atherogenesis. The
      lipid-lowering drugs were supplied by Merck, Sharp & Dohme (simvastatin and ezetimibe).

      Regarding the suspension of lipid-lowering drug in patients with stable coronary artery
      disease (wash-out) for a period of six weeks, there is evidence of no increased risk of acute
      coronary syndrome in the suspension of statin for up to 6 weeks 24.

      The kinetics study of chylomicrons will be carried out as previously published in the
      literature. The lipid emulsion after preparation shows the following percentage composition:
      Triolein 76.5 ± 4.1%, free cholesterol 1.9 ± 0.3%, cholesterol ester 11.2 ± 3.0%
      phospholipids and 10.4 ± 1 3% and sizes ranging from 80 to 100 nm, are made of lipid mixtures
      emulsified by ultrasonic irradiation and purified by ultracentrifugation in density
      gradients.

      C-cholesteryl oleate and H-Triolina are added (TG, Amershan, UK) mixture for determination of
      plasma kinetics. The emulsion is then sterilized through a 2μm filter.

      Patients are instructed to attend to the laboratory at 8:00 am after fasting for 12 hours to
      collect blood sample for lipid analysis. The radioactively labeled lipid emulsion is injected
      as a bolus (volume 200-300μl) containing 74KBp (2μCi) 14C and 148KBp (4μCi) of 3H by
      antecubital vein catheterization. These concentrations are equivalent to respectively 0.02
      and 0.0012 mSv SV radioactive cholesterol and triglycerides. The contralateral antecubital
      vein is cannulated to obtain blood samples for measurement of radioactivity, saline infusion
      without heparin infusion was administered slowly to ensure patency of the vein. A saline
      infusion does not exceed 100ml.

      Thereafter, blood samples are collected at predetermined intervals as follows: 2, 4, 6, 10,
      15, 20, 30, 45 and 60 minutes after injection of the emulsion.

      After collection, blood plasma is separated by centrifugation in 1 ml aliquots, and then
      transferred to counters containing 7ml of scintillation solution PPO: DM-POPOP: Triton
      X-100/toluen (5g: 0,5:333 ml/667ml ). The radioactivity in the samples is determined using a
      Packard 160 TR spectrometer (Packard Meridien, USA).

      The estimated time of the metabolism of lipid emulsion is evaluated by compartmental analysis
      according to the modification of the model proposed by Redgrave and Zench. The delipidation
      index is then calculated as proposed by Redgrave and Zench, which represents the depletion of
      the triglyceride content of lipid emulsion before the capture of chylomicrons from the
      circulation.

      The dose of radioactivity even after the three kinetic studies is much lower (0.0636 mSv)
      maximum annual dose allowed by the International Committee for the Protection of
      radioactivity 50mSv.
    

Intervention name(s): Simvastatin 20mg plus ezetimibe 10mg; ezetimibe; simvastatin 20mg; Simvastatin 80mg
Intervention type(s): Drug; Drug; Drug; Drug
Intervention description(s): simvastatin 20mg plus ezetimibe 10mg once a day for 6 week.; ezetimiba 10mg once a day; simvastatin 20mg once a day; simvastatin 20mg for 6week and then simvastatin 80mg for the next 6week.
Intervention MeSH terms: Simvastatin; Ezetimibe
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: artificial chilomicrons kinetics; ezetimibe plus statin; lipid lowering therapy