Cholesterol absorption and synthesis markers in individuals with and without a CHD event during pravastatin therapy: insights from the PROSPER trial

Abstract

Cholesterol homeostasis, defined as the balance between absorption and synthesis, influences circulating cholesterol concentrations and subsequent coronary heart disease (CHD) risk. Statin therapy targets the rate-limiting enzyme in cholesterol biosynthesis and is efficacious in lowering CHD events and mortality. Nonetheless, CHD events still occur in some treated patients. To address differences in outcome during pravastatin therapy (40 mg/day), plasma markers of cholesterol synthesis (desmosterol, lathosterol) and fractional cholesterol absorption (campesterol, sitosterol) were measured, baseline and on treatment, in the Prospective Study of Pravastatin in the Elderly at Risk trial participants with (cases, n = 223) and without (controls, n = 257) a CHD event. Pravastatin therapy decreased plasma LDL-cholesterol and triglycerides and increased HDL-cholesterol concentrations to a similar extent in cases and controls. Decreased concentrations of the cholesterol synthesis markers desmosterol (−12% and −11%) and lathosterol (−50% and −56%) and increased concentrations of the cholesterol absorption markers campesterol (48% and 51%) and sitosterol (25% and 26%) were observed on treatment, but the magnitude of change was similar between cases and controls. These data suggest that decreases in cholesterol synthesis in response to pravastatin treatment were accompanied by modest compensatory increases in fractional cholesterol absorption. The magnitude of these alterations were similar between cases and controls and do not explain differences in outcomes with pravastatin treatment. Cholesterol homeostasis, defined as the balance between absorption and synthesis, influences circulating cholesterol concentrations and subsequent coronary heart disease (CHD) risk. Statin therapy targets the rate-limiting enzyme in cholesterol biosynthesis and is efficacious in lowering CHD events and mortality. Nonetheless, CHD events still occur in some treated patients. To address differences in outcome during pravastatin therapy (40 mg/day), plasma markers of cholesterol synthesis (desmosterol, lathosterol) and fractional cholesterol absorption (campesterol, sitosterol) were measured, baseline and on treatment, in the Prospective Study of Pravastatin in the Elderly at Risk trial participants with (cases, n = 223) and without (controls, n = 257) a CHD event. Pravastatin therapy decreased plasma LDL-cholesterol and triglycerides and increased HDL-cholesterol concentrations to a similar extent in cases and controls. Decreased concentrations of the cholesterol synthesis markers desmosterol (−12% and −11%) and lathosterol (−50% and −56%) and increased concentrations of the cholesterol absorption markers campesterol (48% and 51%) and sitosterol (25% and 26%) were observed on treatment, but the magnitude of change was similar between cases and controls. These data suggest that decreases in cholesterol synthesis in response to pravastatin treatment were accompanied by modest compensatory increases in fractional cholesterol absorption. The magnitude of these alterations were similar between cases and controls and do not explain differences in outcomes with pravastatin treatment. Elevated plasma LDL-cholesterol and triglyceride concentrations and low HDL-cholesterol concentrations are well-established risk factors for coronary heart disease (CHD) (1AHA. 2007. Heart disease and stroke statistics–2007 update. Accessed January 2009, at http://www.americanheart.org/presenter.jhtml?identifier=1928Google Scholar, 2National Cholesterol Education Program (NCEP) Expert Panel on Detection Evaluation and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). 2002. Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) final report. Circulation. 106: 3143–3421.Google Scholar). Several primary and secondary prevention trials have documented that statin therapy is efficacious in lowering these lipid risk factors and subsequent CHD events and mortality (3Baigent C. Keech A. Kearney P.M. Blackwell L. Buck G. Pollicino C. Kirby A. Sourjina T. Peto R. Collins R. et al.Efficacy and safety of cholesterol-lowering treatment: prospective meta-analysis of data from 90,056 participants in 14 randomised trials of statins.Lancet. 2005; 366 (for the Cholesterol Treatment Trialists’ (CTT) Collaborators): 1267-1278Abstract Full Text Full Text PDF PubMed Scopus (5635) Google Scholar, 4Heart Protection Study Collaborative Group MRC/BHF Heart Protection Study of antioxidant vitamin supplementation in 20,536 high-risk individuals: a randomised placebo-controlled trial.Lancet. 2002; 360: 23-33Abstract Full Text Full Text PDF PubMed Scopus (1351) Google Scholar, 5Long-term Intervention with Pravastatin in Ischaemic Disease (LIPID) Study Group Prevention of cardiovascular events and death with pravastatin in patients with coronary heart disease and a broad range of initial cholesterol levels.N. Engl. J. Med. 1998; 339: 1349-1357Crossref PubMed Scopus (5533) Google Scholar, 6Nakamura H. 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A systematic review and economic evaluation of statins for the prevention of coronary events.Health Technol. Assess. 2007; 11: 1-160Crossref Scopus (292) Google Scholar, 10West of Scotland Coronary Prevention Study Group Prevention of coronary heart disease with pravastatin in men with hypercholesterolemia.N. Engl. J. Med. 1995; 333: 1301-1307Crossref PubMed Scopus (7430) Google Scholar). Nonetheless, CHD events still occur in some treated patients. For instance, in the Scandinavian Simvastatin Survival Study, which evaluated the effect of simvastatin on mortality and morbidity in 4444 CHD patients, simvastatin (20–40 mg/day) lowered LDL-cholesterol concentrations by 35% and raised HDL- cholesterol concentrations by 8% relative to placebo (8The Scandinavian Simvastatin Survival Study Randomized trial of cholesterol lowering in 4444 patients with coronary heart disease: the Scandinavian Simvastatin Survival Study (4S).Lancet. 1994; 344: 1386-1389Google Scholar). These changes were associated with a 42% reduction in the risk of coronary deaths over a 5.4 year median follow-up period. However, there were 431 coronary events and 111 CHD-related deaths in the simvastatin-treated group. Likewise, the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER) Trial examined the effects of pravastatin therapy (40 mg/day) in an elderly cohort of men and women with a history of or risk factors for vascular disease (11Shepherd J. Blauw G.J. Murphy M.B. Bollen E.L. Buckley B.M. Cobbe S.M. Ford I. Gaw A. Hyland M. Jukema J.W. on behalf of the PROSPER study group et al.Pravastatin in elderly individuals at risk of vascular disease (PROSPER): a randomised controlled trial.Lancet. 2002; 360: 1623-1630Abstract Full Text Full Text PDF PubMed Scopus (2933) Google Scholar). The primary endpoint was a composite of CHD death, nonfatal myocardial infarct (MI), and fatal or nonfatal stroke over an average treatment period of 3.2 years. In this trial, at 3 months, pravastatin significantly lowered LDL-cholesterol concentrations by 32%, increased HDL-cholesterol concentrations by 5%, and lowered triglyceride concentrations by 12% compared with the placebo group. These changes were associated with a 15% reduction in incidence of primary endpoints and a 19% reduction in the secondary endpoint of CHD death or nonfatal MI. There were 408 events in the pravastatin group compared with 473 events in the placebo group. These results as well as those from the other statin trials suggest that there is a subgroup of individuals in whom coronary events are not reduced by statin treatment (12Knopp R.H. Paramsothy P. Atkinson B. Dowdy A. Comprehensive lipid management versus aggressive low-density lipoprotein lowering to reduce cardiovascular risk.Am. J. Cardiol. 2008; 101: 48B-75BAbstract Full Text Full Text PDF PubMed Scopus (24) Google Scholar). The reason for this difference in clinical outcomes has yet to be elucidated. Statins are inhibitors of 3-hydroxy-3-methylglutaryl CoA reductase, the rate limiting enzyme in the cholesterol biosynthetic pathway. Because circulating cholesterol concentrations are dependent, in part, on changes in cholesterol synthesis and absorption rates, which are key components of cholesterol homeostasis, it has been suggested that the effectiveness of statins depends on an individual’s baseline cholesterol metabolism (13Miettinen T.A. Gylling H. Ineffective decrease of serum cholesterol by simvastatin in a subgroup of hypercholesterolemic coronary patients.Atherosclerosis. 2002; 164: 147-152Abstract Full Text Full Text PDF PubMed Scopus (50) Google Scholar). Additionally, because statin therapy has been shown to increase cholesterol absorption marker concentrations (14van Himbergen T.M. Matthan N.R. Resteghini N.A. Otokozawa S. Ai M. Stein E.A. Jones P.H. Schaefer E.J. Comparison of the effects of maximal dose atorvastatin and rosuvastatin therapy on cholesterol synthesis and absorption markers.J. Lipid Res. 2009; 50: 730-739Abstract Full Text Full Text PDF PubMed Scopus (84) Google Scholar), it has also been hypothesized that the beneficial effect on LDL-cholesterol-lowering and subsequent CVD risk reduction in response to statin inhibition of cholesterol synthesis would be attenuated in individuals who demonstrated a greater rebound increase in cholesterol absorption. To address these issues, the objective of the present analysis was to quantify the plasma concentrations of selected noncholesterol sterols, reflecting fractional cholesterol absorption efficiency and synthesis rates, in a subset of PROSPER trial participants randomized to pravastatin treatment, with and without a CHD event, baseline and on treatment, and to relate these data to changes in lipoprotein profiles. Details relating to the PROSPER trial have been published previously (11Shepherd J. Blauw G.J. Murphy M.B. Bollen E.L. Buckley B.M. Cobbe S.M. Ford I. Gaw A. Hyland M. Jukema J.W. on behalf of the PROSPER study group et al.Pravastatin in elderly individuals at risk of vascular disease (PROSPER): a randomised controlled trial.Lancet. 2002; 360: 1623-1630Abstract Full Text Full Text PDF PubMed Scopus (2933) Google Scholar). Briefly, PROSPER was a randomized controlled trial of 2,804 men and 3,000 women aged 70–82 years. All subjects had vascular disease or a CHD risk factor at the time of enrollment: smoking, hypertension, diabetes, or elevated total cholesterol (4.0–9.0 mmol/L). Subjects were randomized to receive either 40 mg/day pravastatin or placebo and were followed for an average of 3.2 years. The present study population included 584 subjects all randomized to pravastatin, 292 cases who experienced an event defined as CHD death or nonfatal MI during the study, and 292 controls who did not have an event during the study. Cases and controls were matched on the basis of age, gender, history of vascular disease, smoking status, antihypertensive treatment, diabetes, and country. Baseline and 6 month (on treatment) plasma samples were available for only 223 cases and 257 controls. All subjects included in the present study were still taking pravastatin medication at 6 months. The institutional ethics review boards of all centers approved the protocol, and all participants gave written informed consent. The protocol was consistent with the Declaration of Helsinki. Fasting plasma total cholesterol, triglycerides, and HDL-cholesterol concentrations were measured using standard enzymatic methods, as previously described (11Shepherd J. Blauw G.J. Murphy M.B. Bollen E.L. Buckley B.M. Cobbe S.M. Ford I. Gaw A. Hyland M. Jukema J.W. on behalf of the PROSPER study group et al.Pravastatin in elderly individuals at risk of vascular disease (PROSPER): a randomised controlled trial.Lancet. 2002; 360: 1623-1630Abstract Full Text Full Text PDF PubMed Scopus (2933) Google Scholar). LDL-cholesterol concentrations were calculated according to the Friedewald formula (15Friedewald W.T. Levy R.I. Fredrickson D.S. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge.Clin. Chem. 1972; 18: 499-502Crossref PubMed Scopus (62) Google Scholar). Plasma concentrations of cholesterol homeostasis markers in baseline and on treatment samples were measured using a GC method similar to that previously described (16Matthan N.R. Giovanni A. Schaefer E.J. Brown B.G. Lichtenstein A.H. Impact of simvastatin, niacin, and/or antioxidants on cholesterol metabolism in CAD patients with low HDL.J. Lipid Res. 2003; 44: 800-806Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar, 17Matthan N.R. LaRocque J.M. Pencina M. D’Agostino R.B. Schaefer E.J. Lichtenstein A.H. Alterations in cholesterol absorption and synthesis characterize Framingham Offspring Study participants with coronary heart disease.J. Lipid Res. 2009; 50: 1927-1935Abstract Full Text Full Text PDF PubMed Scopus (137) Google Scholar). Peaks of interest were identified by comparison with authentic standards (Supelco, Bellefonte, PA) and expressed relative to the internal standard. The investigators and laboratory personnel were blinded as to case-control status of the plasma samples. Each case-control set was analyzed in the same run by the same technician in a random sequence under identical conditions. High and low external quality control samples were routinely interspersed and analyzed with study samples. The noncholesterol sterols reported include desmosterol and lathosterol as markers of cholesterol synthesis rates and campesterol and sitosterol as markers of fractional cholesterol absorption efficiency. Baseline characteristics were compared between cases and controls using the two-sample t-test for continuous variables and the chi-square test for categorical variables. The lipid and cholesterol homeostasis marker concentrations at baseline, on treatment and difference (on treatment-baseline) were compared between cases and controls using the two-sample t-test. For lipids the percentage change was analyzed, while for the cholesterol homeostasis markers the absolute change was analyzed. The distribution of triglycerides and the cholesterol homeostasis markers were positively skewed; therefore, a logarithmic transformation was used. The absolute difference in raw values of cholesterol homeostasis markers and percentage difference in triglycerides was analyzed, as these differences were normally between the percentage difference in lipids and absolute difference in cholesterol markers were the use of the Because the noncholesterol sterols are in plasma by it is to concentration relative to the concentration of plasma total cholesterol of in absolute was using the as well as The results of the analysis were In the present study, the cholesterol absorption and synthesis marker concentrations have been expressed as a to the age, and distribution were similar among cases and controls Likewise, the percentage of cases and controls who were and who had vascular disease, hypertension, and was also There were differences between cases and of gender, in baseline and on treatment plasma lipid and lipoprotein in total and LDL-cholesterol and triglyceride concentrations and increases in HDL-cholesterol concentrations with pravastatin treatment were observed in cases and but there were differences between = 223 = 257 from two-sample t-test or chi-square are are disease are from two-sample t-test or chi-square in a baseline, cases and controls had similar concentrations of the cholesterol synthesis and absorption markers 6 on pravastatin treatment, there was a reduction in plasma concentrations of the cholesterol synthesis markers desmosterol (−12% and and lathosterol (−50% and −56%) in the cases and compared with baseline values In plasma concentrations of the cholesterol absorption markers campesterol (48% and 51%) and sitosterol (25% and 26%) significantly increased with pravastatin treatment in cases and controls. However, there was difference in the magnitude of the change between the cases and controls. and followed similar with to cholesterol homeostasis marker cholesterol homeostasis marker = = = = from two-sample synthesis markers of are calculated from the are calculated from the absorption markers of are calculated from the are calculated from the are calculated from the are calculated from the from two-sample are calculated from the in a The between change in the cholesterol synthesis and absorption markers with pravastatin treatment and the change in plasma lipid and lipoprotein are in In cases and were observed between the cholesterol synthesis markers and total and and the cholesterol absorption markers and HDL-cholesterol In the controls the cholesterol synthesis markers were positively associated with change in In the cases the cholesterol synthesis markers were positively associated with change in HDL-cholesterol and the cholesterol absorption markers were associated with change in LDL-cholesterol between cholesterol homeostasis markers and lipid risk were between the percentage difference in lipids and absolute difference in The data are in range of to and the cholesterol were between the percentage difference in lipids and absolute difference in The data are in range of to and the in a To this the change in cholesterol homeostasis markers by pravastatin treatment was and the decrease in plasma LDL-cholesterol and triglyceride and the increase in HDL-cholesterol concentrations were for the cases and controls 3 and Cases and controls who had the decrease in cholesterol synthesis, as by lathosterol concentrations also had the decrease in plasma LDL-cholesterol concentrations 3 results were also observed for desmosterol concentrations not of change (on treatment-baseline) in cholesterol as by plasma campesterol concentrations a to and change in plasma LDL-cholesterol lowering and triglyceride lowering and and HDL-cholesterol and in cases and is Cases and controls of response with to the between cholesterol synthesis and triglyceride and HDL-cholesterol concentrations who had the reduction in lathosterol demonstrated greater decreases in triglycerides = and a greater increases in HDL-cholesterol concentrations = However, in the greater decreases in lathosterol were associated with increases in HDL-cholesterol was observed between cholesterol synthesis and change in triglyceride concentrations in response to pravastatin therapy in the cases = to the cholesterol absorption markers and plasma and triglyceride cases and controls a similar of response data not shown for sitosterol but was these results suggest that the decrease in cholesterol synthesis in response to pravastatin is to the magnitude of plasma LDL-cholesterol lowering in cases and controls. The that the decrease in cholesterol synthesis to be associated with plasma response in control subjects and response in cases the decrease in cholesterol synthesis is but the and are modest and the clinical is of a clinical trial that examined the effects of pravastatin on CVD outcomes in an elderly risk plasma concentrations of noncholesterol sterols fractional cholesterol absorption and were measured at baseline and after 6 on treatment in a subset of individuals who experienced a clinical event and matched controls who did not have an event. The was to changes in cholesterol homeostasis marker concentrations by statin treatment plasma lipoprotein response and CVD of this that pravastatin treatment decreased cholesterol synthesis and increased fractional cholesterol absorption and these changes were associated with the magnitude of LDL-cholesterol However, the of response was similar between cases and controls and not explain the difference in The decrease in plasma total and LDL-cholesterol concentrations observed in patients treated with a statin is to the inhibition in 3-hydroxy-3-methylglutaryl CoA the rate limiting enzyme in cholesterol reduction in cholesterol synthesis of in the increased of circulating cholesterol M. L. S. I. B. of pravastatin, a of reductase, on metabolism of Engl. J. Med. PubMed Scopus Google Scholar). The are also consistent with and those of other that statin treatment increases the rate of cholesterol absorption (16Matthan N.R. Giovanni A. Schaefer E.J. Brown B.G. Lichtenstein A.H. Impact of simvastatin, niacin, and/or antioxidants on cholesterol metabolism in CAD patients with low HDL.J. Lipid Res. 2003; 44: 800-806Abstract Full Text Full Text PDF PubMed Scopus (68) Google Scholar, T.A. Gylling H. T. S. Baseline serum as of coronary events in subgroup of Scandinavian simvastatin study. 1998; PubMed Scopus Google Scholar, T.A. Gylling H. sterols and cholesterol lowering by simvastatin treatment in coronary to serum PubMed Scopus Google Scholar). response a compensatory increase in absorption efficiency to cholesterol homeostasis by the of cholesterol hypothesized that the beneficial effect on LDL-cholesterol lowering and subsequent CVD risk reduction by statin inhibition of cholesterol synthesis would be attenuated in individuals who demonstrated a greater rebound increase in cholesterol absorption. However, differences were observed between cases and controls in the magnitude of decrease in cholesterol synthesis or increase in fractional cholesterol absorption in response to pravastatin treatment and the subsequent of LDL-cholesterol it has been suggested that the in cholesterol lowering response among individuals treated with statins is to differences in baseline cholesterol metabolism H. T.A. Baseline absorption and synthesis of cholesterol response to in coronary patients.Atherosclerosis. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). Gylling and H. T.A. Baseline absorption and synthesis of cholesterol response to in coronary patients.Atherosclerosis. 2002; Full Text Full Text PDF PubMed Scopus Google reported in a subgroup analysis of coronary patients who did not to simvastatin treatment that patients who were as cholesterol low by plasma concentrations of the cholesterol homeostasis were to statins patients as low In the present study, there were differences in the cholesterol homeostasis marker concentrations at baseline between cases and controls. Additionally, a similar of response was observed between cases and controls in the magnitude of decrease in cholesterol synthesis or increase in fractional cholesterol absorption efficiency in response to pravastatin treatment and the subsequent of LDL-cholesterol alterations in cholesterol homeostasis and LDL-cholesterol do not explain the difference in clinical outcomes in study The difference between cases and controls was in the response of triglycerides and HDL-cholesterol to the alterations in cholesterol the decrease in cholesterol synthesis in response to pravastatin treatment was associated with greater decreases in triglyceride concentrations and a greater increases in HDL-cholesterol concentrations in the controls. However, in the greater decreases in cholesterol synthesis in response to treatment were associated with increases in HDL-cholesterol and there was difference in triglyceride The reason for the difference in response to treatment between the is is well that HDL-cholesterol concentrations are associated with triglyceride concentrations to In to the of in cholesterol and are also as for this M. R. N. W. N. A. N. et antioxidant and 2007; PubMed Scopus Google Scholar). In study, patients with CHD or CHD risk factors had relative to matched controls at baseline, and to have after statin therapy a decrease in plasma has been shown to have to cholesterol M. S. N. G. S. R. R. et of lipoprotein patients from cholesterol subjects lipoprotein cholesterol and are by simvastatin 2003; PubMed Scopus Google Scholar). These data suggest that statin therapy have in some but not all of and this have for differences in clinical outcome similar plasma lipoprotein profiles. In to the statins have also been shown to have beneficial effects on CVD risk factors as and in and have been documented that response to statin treatment. Pravastatin has been shown to be in lowering cholesterol synthesis in of the compared with M. M. M. effects of pravastatin on cholesterol synthesis are associated with 2005; PubMed Scopus Google Scholar). at the as well as the and have also been shown to response to pravastatin and CVD T. A. The of and cholesterol 2005; PubMed Google Scholar, H. N. I. M. Ford I. C. J. Jukema J.W. on behalf of the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER) et at the and lipid statin and cardiovascular disease incidence in 2008; Full Text Full Text PDF PubMed Scopus Google Scholar). plasma concentrations were similar between cases and and controls and and the that the magnitude of other effects of statin therapy as well as of to cholesterol homeostasis between cases and controls and to the reduction in coronary In results suggest that in an elderly population with a CVD the decrease in cholesterol synthesis in response to pravastatin therapy is accompanied by a modest compensatory increase in markers of fractional cholesterol absorption. The magnitude of these alterations was similar between cases and controls and not explain differences in outcomes with pravastatin treatment. J. of and S. M. of and of I. for of A. of P. W. of and of C. J. of J. of and of G. J. of and The L. M. of The A. M. of and The R. G. J. of and The M. B. of and B. M. of and M. and of I. J. of and S. M. Cobbe J. W. of The A. of The B. J. of C. and of The the of the study without whom this would not be coronary heart disease myocardial infarct Prospective Study of Pravastatin in the Elderly at Risk