HMG-CoA Reductase Inhibitor Pravastatin Research Articles

Chronic use of pravastatin reduces insulin exocytosis and increases β-cell death in hypercholesterolemic mice.

We have previously demonstrated that hypercholesterolemic LDL receptor knockout (LDLr(-/-)) mice secrete less insulin than wild-type mice. Removing cholesterol from isolated islets using methyl-beta-cyclodextrin reversed this defect. In this study, we hypothesized that in vivo treatment of LDLr(-/-) mice with the HMGCoA reductase inhibitor pravastatin would improve glucose-stimulated insulin secretion. Female LDLr(-/-) mice were treated with pravastatin (400mg/L) for 1-3 months. Isolated pancreatic islets were assayed for insulin secretion rates, intracellular calcium oscillations, cholesterol levels, NAD(P)H and SNARE protein levels, apoptosis indicators and lipidomic profile. Two months pravastatin treatment reduced cholesterol levels in plasma, liver and islets by 35%, 25% and 50%, respectively. Contrary to our hypothesis, pravastatin treatment increased fasting and fed plasma levels of glucose and decreased markedly (40%) fed plasma levels of insulin. In addition, ex vivo glucose stimulated insulin secretion was significantly reduced after two and three months (36-48%, p<0.05) of pravastatin treatment. Although reducing insulin secretion and insulinemia, two months pravastatin treatment did not affect glucose tolerance because it improved global insulin sensitivity. Pravastatin induced islet dysfunction was associated with marked reductions of exocytosis-related SNARE proteins (SNAP25, Syntaxin 1A, VAMP2) and increased apoptosis markers (Bax/Bcl2 protein ratio, cleaved caspase-3 and lower NAD(P)H production rates) observed in pancreatic islets from treated mice. In addition, several oxidized phospholipids, tri- and diacylglycerols and the proapoptotic lipid molecule ceramide were identified as markers of pravastatin-treated islets. Cell death and oxidative stress (H2O2 production) were confirmed in insulin secreting INS-1E cells treated with pravastatin. These results indicate that chronic treatment with pravastatin impairs the insulin exocytosis machinery and increases β-cell death. These findings suggest that prolonged use of statins may have a diabetogenic effect.

Idarubicin, Cytarabine and Pravastatin As Induction Therapy for Untreated Acute Myeloid Leukemia and High-Risk Myelodysplastic Syndrome

Background: AML patients who achieve a “good CR” meaning CR with count recovery (ANC > 1000/ μL, platelets > 100,000/ μL) by day 35 of induction therapy without evidence of minimal residual disease (MRD) on flow cytometry or cytogenetics are less likely to relapse than patients who enter CR with MRD or have slower count recovery. At our institution approximately 75% of CRs are “good CRs” and the good CR rate has been 50%. To improve the latter we combined idarubicin + Cytarabine with the HMG-CoA reductase inhibitor pravastatin (IAP) in newly-diagnosed AML because (a) high intracellular cholesterol levels in AML cells may be an adaptive mechanism of chemoresistance and (b) IAP resulted in higher than expected CR rates in relapsed/refractory AML (Advani et al, ASCO, 2013).Methods: Patients age 18 to 74 with untreated AML (except APL) or MDS/MPN with ≥10% blasts and an anticipated <10% treatment-related mortality rate (Walter et al. 2001) were eligible. Patients received pravastatin (1,280 mg po daily days 1-8), cytarabine (1.5 g/m(2) IV daily, days 4-7) and idarubicin (12 mg/m(2) IV daily, days 4-6). Patients were taken off study if the bone marrow examination between days 17-20 revealed more than 60% myeloid blasts, or if MRD were present between days 31-38. Up to 3 cycles of consolidation with a shortened course of the same regimen was permitted (2 days of IA). Maximum sample size was 50 pts. The study was to stop early if after evaluation of each cohort of 5 patients either (a) the Bayesian posterior probability was < 5% that the true good CR rate was ≥ 70% or (b) the posterior probability was >25% that the TRM rate by day 28 was≥ the historical 5%. Thus parameterized the probability that early stopping would occur if the true good CR rate was 70% and the true TRM rate 5% was 17% after entry of 25 patients, 23% after entry of 30 patients, and 30% after entry of 40 patients.Results: Between May 2013 and April 2014, 24 patients [AML=21 (87%), MDS=2 (9%), CMML=1 (4%)] were treated per protocol. Median age was 57 (range, 35-72) and per ELN classification, 4 (19%), 4 (19%), 6 (29%) and 7 (33%) AML patients had favorable, intermediate-1, intermediate-2 and adverse risk cytogenetics, respectively. Twenty-three (96%) patients completed induction and 9 (37.5%) received consolidation per protocol. Conventional CR was achieved in 17 (71%) patients but only 12 (50%) achieved “good CR”. Two (8.3%) patients died within 28 days after induction (from typhlitis and septic shock (day and five (21%) patients had persistent disease. Given the above noted stopping rules accrual ceased after entry of these 24 patients. 6 patients relapsed after initial CR (3 before HCT and 3 after HCT). Median time to relapse was 112 days (range, 49-164). and 3 patients died between days 175 and 285 after induction therapy from multi-organ system failure and sepsis. The most common grade 3-4 adverse effects were infections (including febrile episodes), gastrointestinal and dermatologic and were observed in 100%, 80% and 50% of patients, respectively. Nineteen (79%) patients were alive after median follow-up of 7.2 months (range, 0.4-11.9).Conclusion: IAP did not meet the pre-defined criteria for success: good CR rate ≥ 70%, TRM rate < 5% leading to early stopping with only a 17% chance that such stopping would have occurred if these were the true rates with this therapy. While it remains possible that our 24 patients were “more unfavorable” than the historical population, stressing the need for development of observed/expected ratios applicable to individual patients in a trial, the demographics of the IAP population suggest this was not the case. DisclosuresOff Label Use: Pravastatin is not FDA approved for treatment of AML.

Intestinal Absorption of HMG-CoA Reductase Inhibitor Pravastatin Mediated by Organic Anion Transporting Polypeptide

The purpose of this study is to clarify the impact of organic anion transporting polypeptide (Oatp) on intestinal absorption of the HMG-CoA reductase inhibitor, pravastatin. OATP/Oatp-mediated pravastatin uptake was evaluated with Xenopus oocytes systems. Intestinal permeability was measured by an in situ closed loop method in rats. In vivo pravastatin absorption was kinetically assessed by measuring plasma concentration after oral administration in rats. Uptake of pravastatin by Oatp1a5, Oatp2b1, OATP1A2, and OATP2B1 cRNA-injected Xenopus oocytes was significantly increased compared with that by water-injected oocytes. Naringin, a potent inhibitor of Oatps and Mdr1, decreased the Oatp1a5-mediated uptake of pravastatin with IC (50) value of 30.4μM. Rat intestinal permeability of pravastatin was significantly reduced in the presence of 1,000μM naringin. Similar results were obtained in in vivo absorption studies in rats. Furthermore, no significant change in the permeability was observed in the presence of elacridar, a potent inhibitor of both Mdr1 and Bcrp, though the permeability was significantly decreased in the presence of both elacridar and naringin, suggesting that Mdr1 and Bcrp are not involved in intestinal absorption of pravastatin. Oatp, but not by Mdr1 or Bcrp, contributes to the intestinal absorption of pravastatin in rats.

Endothelial function in subjects with isolated low HDL cholesterol: role of nitric oxide and circulating progenitor cells

Epidemiologic studies have shown that a low level of high-density lipoprotein (HDL) cholesterol is a risk factor for cardiovascular diseases. The purpose of this study was to determine the contribution of isolated low HDL cholesterol to endothelial function. Thirty-nine subjects with low HDL cholesterol who had no other cardiovascular risk factors were selected from the 5,417 participants from our population. We evaluated flow-mediated vasodilation (FMD) before and after 4 wk of treatment with the HMG-CoA reductase inhibitor pravastatin in 29 of the 39 subjects with isolated low HDL cholesterol. FMD was lower in the low-HDL-cholesterol group (n = 29) than in the control group (n = 29), whereas NTG-induced vasodilation was similar in the two groups. Pravastatin increased HDL cholesterol, urinary excretion of nitrite/nitrate, circulating levels of progenitor cells, and cell migration response to vascular endothelial growth factor in 15 subjects with low HDL cholesterol but not in 14 placebo control subjects. FMD increased in the pravastatin treatment group but not in the control group. NTG-induced vasodilation was similar before and after 4 wk of treatment in the two groups. Multiple regression analysis revealed that changes in HDL cholesterol, the number of progenitor cells, and migration of progenitor cells were independent predictors of augmentation of FMD with pravastatin. These findings suggest that low HDL cholesterol is an independent risk factor for endothelial dysfunction and that pravastatin improves endothelial function in individuals with isolated low HDL cholesterol through, at least in part, an increase in circulating progenitor cells.

Investigation of the Rate-Determining Process in the Hepatic Elimination of HMG-CoA Reductase Inhibitors in Rats and Humans

Elucidation of the rate-determining process in the overall hepatic elimination of drugs is critical for predicting their intrinsic hepatic clearance and the impact of variation of sequestration clearance on their systemic concentration. The present study investigated the rate-determining process in the overall hepatic elimination of the HMG-CoA reductase inhibitors pravastatin, pitavastatin, atorvastatin, and fluvastatin both in rats and humans. The uptake of these statins was saturable in both rat and human hepatocytes. Intrinsic hepatic clearance obtained by in vivo pharmacokinetic analysis in rats was close to the uptake clearance determined by the multiple indicator dilution method but much greater than the intrinsic metabolic clearance extrapolated from an in vitro model using liver microsomes. In vivo uptake clearance of the statins in humans (pravastatin, 1.44; pitavastatin, 30.6; atorvastatin, 12.7; and fluvastatin, 62.9 ml/min/g liver), which was obtained by multiplying in vitro uptake clearance determined in cryopreserved human hepatocytes by rat scaling factors, was within the range of overall in vivo intrinsic hepatic clearance (pravastatin, 0.84-1.2; pitavastatin, 14-35; atorvastatin, 11-19; and fluvastatin, 123-185 ml/min/g liver), whereas the intrinsic metabolic clearance of atorvastatin and fluvastatin was considerably low compared with their intrinsic hepatic clearance. Their uptake is the rate-determining process in the overall hepatic elimination of the statins in rats, and this activity likely holds true for humans. In vitro-in vivo extrapolation of the uptake clearance using a cryopreserved human hepatocytes model and rat scaling factors will be effective for predicting in vivo intrinsic hepatic clearance involving active uptake.

The Influence of Macrolide Antibiotics on the Uptake of Organic Anions and Drugs Mediated by OATP1B1 and OATP1B3

Macrolides may cause severe drug interactions due to the inhibition of metabolizing enzymes. Transporter-mediated uptake of drugs into cells [e.g., by members of the human organic anion transporting polypeptide (OATP) family] is a determinant of drug disposition and a prerequisite for subsequent metabolism. However whether macrolides are also inhibitors of uptake transporters, thereby providing an additional mechanism of drug interactions, has not been systematically studied. The human OATP family members OATP1B1 and OATP1B3 mediate the uptake of endogenous substances and drugs such as antibiotics and HMG-CoA reductase inhibitors (statins) into hepatocytes. In this study we investigated the potential role of these uptake transporters on macrolide-induced drug interactions. By using sulfobromophthalein (BSP) and the HMG-CoA reductase inhibitor pravastatin as substrates, the effects of the macrolides azithromycin, clarithromycin, erythromycin, and roxithromycin and of the ketolide telithromycin on the OATP1B1- and OATP1B3-mediated uptake were analyzed. These experiments demonstrated that the OATP1B1- and OATP1B3-mediated uptake of BSP and pravastatin can be inhibited by increasing concentrations of all macrolides except azithromycin. The IC50 values for the inhibition of OATP1B3-mediated BSP uptake were 11 microM for telithromycin, 32 microM for clarithromycin, 34 microM for erythromycin, and 37 microM for roxithromycin. These IC50 values were lower than the IC50 values for inhibition of OATP1B1-mediated BSP uptake (96-217 microM). These macrolides also inhibited in a concentration-dependent manner the OATP1B1- and OATP1B3-mediated uptake of pravastatin. In summary, these results indicate that alterations of uptake transporter function by certain macrolides/ketolides have to be considered as a potential additional mechanism underlying drug-drug interactions.

Additive effects of combined blockade of AT1receptor and HMG-CoA reductase on left ventricular remodeling in infarcted rats

Both angiotensin receptor antagonists and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors have been shown to attenuate cardiomyocyte hypertrophy after myocardial infarction. Whether combination treatment may be superior to either drug alone on cardiomyocyte hypertrophy remains unclear. After ligation of the left anterior descending artery, rats were randomized to both, one, or neither of the angiotensin receptor antagonists olmesartan (0.01, 0.1, 1, and 2 mg.kg-1.day-1) and HMG-CoA reductase inhibitor pravastatin (5 mg.kg-1.day-1) for 4 wk. Each drug, when given alone, decreased cardiomyocyte sizes isolated by enzymatic dissociation at the border zone when compared with vehicles. However, compared with either drug alone, combined olmesartan and pravastatin prevent cardiomyocyte hypertrophy to a larger extent, which was further confirmed by downregulation of the left ventricular atrial natriuretic peptide mRNA. The myocardial endothelin-1 levels at the border zone were 6.5-fold higher (P<0.0001) in the vehicle group compared with the sham group, which can be inhibited after pravastatin administration. Combination treatment significantly attenuated cardiomyocyte hypertrophy in a dose-dependent manner, although tissue endothelin-1 levels remained stable in combination groups of different olmesartan doses. Measurements of the arrhythmic score mirrored those of cardiomyocyte hypertrophy. Dual therapy with pravastatin and olmesartan, which produced an additive reduction in cardiomyocyte hypertrophy and cardiac fibrosis after myocardial infarction through different mechanisms, decreases the propensity of the heart to arrhythmogenesis. Pravastatin administration provided favorable ventricular remodeling, probably through decreased tissue endothelin-1 level. In contrast, olmesartan-related attenuated cardiomyocyte hypertrophy is independent of endothelin-1 pathway.

Influence of the SLCO1B1*1b and *5 haplotypes on pravastatin’s cholesterol lowering capabilities and basal sterol serum levels

We previously showed that variant SLCO1B1 haplotype *1b (A388G) accelerates and that *5 (T521C) delays hepatocellular uptake of the HMG-CoA reductase inhibitor pravastatin [Mwinyi et al. (2004): Clin Pharmacol Ther 75:415-421]. In the present study we checked for differential effects of variant SLCO1B1 haplotypes on hepatocellular cholesterol synthesis. We analyzed the serum levels of cholesterol, lathosterol, and campesterol in healthy white males which had been grouped on the basis of their SLCO1B1 haplotype: *1a (n=10), *1b (n=10), and *5 (n=8). The subjects received a single oral dose of 40 mg pravastatin. Cholesterol and lathosterol levels were lower in all subjects following pravastatin intake for up to 24. Median levels 6 h post-dosing of lathosterol decreased in each SLCO1B1 haplotype group in the rank order of *1b (-0.11 mg dl(-1); min-max: -0.20 to -0.04; p=0.005) > *1a (-0.09 mg dl(-1); min-max: -0.22 to -0.05; p=0.005) > *5 (-0.07 mg dl(-1); min-max: -0.17 to -0.05; p=0.012). Lathosterol median-change values were significantly greater in haplotype *1b than in haplotype *5 individuals (p=0.041, non-adjusted), which was congruent with the extent of mean changes in lathosterol-to-cholesterol ratios, although the latter did not reach statistical significance. Post-treatment serum levels of campesterol were not affected by SLCO1B1 haplotype. Interestingly, sterol basal serum levels tended to be highest in *1b carriers, followed by those in *1a and *5 individuals, with significant differences in lathosterol concentrations between the *1b and *5 (p=0.041, non-adjusted) haplotype group. Our findings suggest an association of SLCO1B1*1b and *5 haplotypes to pravastatin's inhibition of the hepatocellular HMG-CoA reductase. Furthermore, SLCO1B1 haplotypes seem to play a role in basal cholesterol homeostasis.

Pravastatin and Clopidogrel Combined Inhibit Intimal Hyperplasia in a Rat Carotid Endarterectomy Model

Intimal hyperplasia, resulting from a complex cascade of events involving platelets, leukocytes, and smooth muscle cells, may be inhibited by the HMG-CoA reductase inhibitor pravastatin, which demonstrates inhibition of platelet activity and leukocyte adhesion and may be associated with inhibition of vascular smooth muscle cell proliferation and migration. Clopidogrel, an adenosine diphosphate (ADP) receptor inhibitor, was shown to decrease platelet activity and aggregation but not intimal hyperplasia (IH). We postulated that the combination of both pravastatin and clopidogrel would significantly decrease IH in a rat carotid endarterectomy model. Male Sprague-Dawley rats (n = 18) divided by treatment regimen underwent treatment for 2 weeks both before and after an open carotid endarterectomy. Serum collected at the time of harvest was measured for C-reactive protein (CRP), platelet activity, and total serum cholesterol; carotid arteries were removed and processed for IH determination. Control rats (n = 7) received oral vehicle daily before and following endarterectomy. Pravastatin-alone rats (n = 6) received oral pravastatin (10 mg/kg/day) before and after endarterectomy. Pravastatin plus clopidogrel rats (n = 5) received oral pravastatin (10 mg/kg/day) plus a preendarterectomy bolus of oral clopidogrel (4.3 mg/kg) before endarterectomy and resumed pravastatin (10 mg/kg/day) plus oral clopidogrel (1 mg/kg/day) postendarterectomy. Pravastatin alone and pravastatin plus clopidogrel significantly decreased CRP compared to controls (120.2 +/-11.2 and 134.1 +/- 9.9 vs 191.1 +/- 9.2 microg/mL, respectively p = 0.003 and p =0.0024). CRP levels were not different between pravastatin alone and pravastatin plus clopidogrel (p = 0.35). Platelet activity was significantly decreased by pravastatin alone and pravastatin plus clopidogrel in comparison to controls (7.3 +/- 2.2 and 6.6 +/- 2.8 vs 19.2 +/- 6.1 platelet reactive units (PRU), respectively p = 0.048 and p = 0.045). No significant difference was noted in platelet activity between pravastatin alone and pravastatin plus clopidogrel (p = 0.89). Pravastatin plus clopidogrel significantly reduced serum cholesterol compared to control and pravastatin alone (84.0 +/- 6.6 vs 110.4 +/- 7.4 and 117.0 +/- 8.8 mg/dL, respectively p = 0.03 and p = 0.01). Pravastatin alone did not decrease serum cholesterol compared to controls (p = 0.54). IH was not reduced by pravastatin alone compared to controls (p = 0.61) but was significantly decreased by pravastatin plus clopidogrel in comparison to control and pravastatin alone (3.0 +/- 1.1 vs 46.3 +/- 13.7 and 37.4 +/- 14.6% luminal stenosis, respectively p = 0.01 and p = 0.05). Pravastatin plus clopidogrel significantly decreased CRP, platelet activity, total serum cholesterol, and IH while pravastatin alone decreased only CRP and platelet activity. Intimal hyperplasia reduction may therefore be dependent on other contributors, possibly growth factors, cytokines, and oxidative stress. The combination of pravastatin plus clopidogrel may have synergistic or even additional inhibitory effects on IH. Pravastatin plus clopidogrel was effective in decreasing IH in a rat carotid endarterectomy model and may prove a useful therapy for IH reduction in the clinical setting.

Systemic inflammatory markers in acute coronary syndrome: association with cardiovascular risk factors and effect of early lipid lowering

Evidence for statin therapy in prevention of coronary artery disease is overwhelming. In spite of theoretical benefits, any additional advantage of its early introduction in the management of acute coronary syndrome is, however, uncertain. We therefore investigated differences between plasma levels of the systemic inflammatory markers intercellular adhesion molecule-1, vascular cell adhesion molecule-1, E-selectin, C-reactive protein and interleukin-6 in patients presenting with unstable angina or acute myocardial infarction, and assessed whether the 30-day levels of these markers are influenced by early instigation of the HMG-CoA reductase inhibitor pravastatin. 170 (134 male) patients presenting with acute coronary syndrome, but without previous statin therapy, participated. Blood was taken within 24 h of onset of ischaemic pain and again at 30 days. In all, 87 (71 male) participants were treated with pravastatin (20-40 mg daily) and 83 (63 male) with a matched placebo. At presentation, interleukin-6 was higher in males than in females (P=0.008) and lower in those with a pre-existing history of myocardial infarction (P=0.038). C-reactive protein and interleukin-6 were greater in myocardial infarction, but this difference was lost at 30 days. Thirty-day changes in all parameters were inversely related to level at presentation but not to treatment with pravastatin. Hypertension (P=0.011) and smoking (P=0.042) were associated with elevation of C-reactive protein with no difference between unstable angina or acute myocardial infarction. The effect of these individual factors was cumulative. Interleukin-6 was greater in acute myocardial infarction than in unstable angina; E-selectin was positively associated with a previous myocardial infarction and inversely related to age. We found no effect of early introduction of pravastatin on systemic inflammatory markers 30 days after acute coronary syndrome.

Effects of pravastatin on the expression of ATP-binding cassette transporter A1.

In vitro inhibition of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase causes the suppression of liver X receptor (LXR) activity. Because LXR regulates the expression of ATP-binding cassette transporter (ABC) A1, which is involved in the high-density lipoprotein-related reverse cholesterol transport pathway, we examined the effects of an HMG-CoA reductase inhibitor pravastatin on ABCA1 expression in vitro and in vivo. Pravastatin (10 microM) significantly reduced the transcript levels of murine ABCA1 gene by 35% in RAW264.7 macrophages under a lipoprotein-deficient condition. The inhibition was due to the decreased mevalonic acid production because addition of exogenous mevalonic acid restored ABCA1 mRNA levels. In addition, cholesterol and 22(R)-hydroxycholesterol thoroughly blunted the inhibition. Furthermore, pravastatin did not decrease ABCA1 mRNA and protein levels in HepG2 hepatocytes even in the absence of exogenous LXR agonists. Oral dosing of pravastatin (0.1% concentration in drinking water) for 24 h or 2 weeks to mice did not decrease ABCA1 mRNA and protein levels in the liver and leukocytes. Interestingly, pravastatin significantly increased both hepatic and leukocyte LXRalpha mRNA levels. Thus, although HMG-CoA reductase inhibitors suppress ABCA1 mRNA expression in the absence of LXR agonists, in vivo inhibition of HMG-CoA reductase is unlikely to cause such suppression.

Randomized, controlled trial of secondary prevention of coronary sclerosis in normocholesterolemic patients using pravastatin: two-year follow-up of the prevention of coronary sclerosis study

Background: Reducing serum total cholesterol (TC) levels using 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors in hypercholesterolemic patients has been shown to reduce the incidence of complications of coronary heart disease (CHD). However, few data are available on the potential benefit of reductions in serum cholesterol levels in normocholesterolemic patients with coronary atherosclerosis. Objective: The Prevention of Coronary Sclerosis Study is a single-center study designed to assess the effect of treatment with the HMG-CoA reductase inhibitor pravastatin on progression and regression of angiographically documented coronary atherosclerosis in normocholesterolemic patients with CHD. Methods: A total of 329 patients aged <70 years with CHD were enrolled and classified into 1 of 3 groups based on serum TC level: group 1, TC ≥220 mg/dL; group 2, TC 180–219 mg/dL; and group 3, TC <180 mg/dL. Patients in group 2 were randomized to 1 of 2 subgroups, 2a or 2b. Patients in groups 1 and 2a were given pravastatin 10 mg/d; patients in groups 2b and 3 did not receive cholesterol-lowering drugs. The subsequent coronary events of patients were followed for 2 years and reexamined by coronary angiography (CAG). Both baseline and follow-up CAGs were analyzed by quantitative coronary arteriography at a central laboratory. Results: Decreases in both mean segment diameter (MSD) and minimum obstruction diameter (MOD) in group 2a were significantly less than those in the control group 2b ( P = 0.015 and P = 0.023, respectively). The effects on MSD and MOD in group 2a and the low-cholesterol reference group 3 were similar. The incidence of clinical events was 8.9%, 3.7%, 12.1%, and 10.0% in groups 1, 2a, 2b, and 3, respectively, with no significant differences in rates between groups 2a and 2b. Conclusion: The results of this study suggest that cholesterol-lowering therapy with pravastatin may prevent progression of coronary atherosclerosis in normocholesterolemic patients with CHD.

Effects of lipid-lowering drugs on intermediate-density lipoprotein in uremic patients

Patients with chronic renal failure often have alterations in lipoprotein profile including elevated very-low density lipoprotein (VLDL) and intermediate density lipoprotein (IDL), and reduced high density lipoprotein (HDL) levels. Among these changes, raised IDL has been shown as an independent risk factor for atherosclerosis in hemodialysis patients. There are a limited number of studies reporting pharmacological approaches to IDL reduction in a uremic population. We therefore summarize the effects of lipid-lowering drugs on IDL levels in patients with chronic renal failure treated by hemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD). First, a nicotinic acid analog niceritrol was given to hemodialysis patients. The drug increased HDL-cholesterol by 11%, but the reductions in VLDL-, IDL- and LDL-cholesterol were not significant. Second, CAPD patients were treated with a fibric acid derivative clinofibrate, which was excreted mainly into bile unlike other drugs in this class. The fibrate resulted in a remarkable reduction in VLDL-triglycerides, although it did not reduce IDL-cholesterol. Finally, an HMG-CoA reductase inhibitor (statin) pravastatin was used in HD and CAPD patients. Pravastatin reduced IDL- and LDL-cholesterol to the same extent (by 31%). None of these treatments caused serious adverse effects. We propose that IDL is an important target in the management of uremic dyslipidemia. To date, statins have been shown to be suitable for this purpose, although it remains to be clarified whether such an intervention reduces the risk for atherosclerotic vascular events in the uremic population.

Combination of fosinopril and pravastatin decreases platelet response to thrombin receptor agonist in monkeys.

Both angiotensin-converting enzyme (ACE) inhibitors and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors have been shown to decrease cardiovascular morbidity and mortality. Results from clinical trials have suggested that HMG-CoA reductase inhibition might exert a beneficial effect independent of its lipid-lowering effect, and ACE inhibition may exert a benefit independent of blood-pressure lowering. To test the hypothesis that such an effect might be mediated by alteration in platelet reactivity, we studied 55 monkeys receiving both, 1, or neither of the ACE inhibitor fosinopril and the HMG-CoA reductase inhibitor pravastatin. Platelet responsiveness to collagen and to the thrombin receptor agonist (TRA) SFLRRN-NH2 was determined by aggregometry. For each agonist, the maximum rate and extent of aggregation were measured for each dose, and the concentration required for half-maximal response (C50) was determined. Each drug, when given alone, slightly decreased the dose of agonist required to produce 50% response in the rate and extent of platelet aggregation relative to control. The combination of the 2 drugs, however, produced a significant increase in the dose of TRA required to produce 50% response in the rate and extent of aggregation relative to either drug alone or the control group. This was not true for collagen. The magnitude of the change relative to the control group, 47% for rate and 30% for extent of aggregation, could confer considerable protection by changing the threshold for thrombin-induced platelet aggregation and, thus, decrease thrombosis.

HMG-CoA Reductase Inhibitors Pravastatin and Simvastatin Inhibit Human B-Lymphocyte Activation

HMG-CoA Reductase Inhibitors Pravastatin and Simvastatin Inhibit Human B-Lymphocyte Activation

Determination of pravastatin in human plasma by high-performance liquid chromatography with ultraviolet detection

A sensitive high-performance liquid chromatographic (HPLC) method for the quantitation of the HMG-CoA reductase inhibitor pravastatin in human plasma is described. Sample preparation based on reversed-phase solid-phase extraction using triamcinolone acetonide as internal standard (I.S.). The compounds were separated on C 18 reversed-phase analytical column and then determined by ultraviolet detection. The recovery of pravastatin from plasma was 69.2±6.7% (mean±S.D.). The limit of detection for pravastatin in aqueous solution was 0.4 ng, the limit of quantitation in plasma was 2 ng/ml. In a preliminary pharmacokinetic study with two healthy volunteers the t 1/2 of pravastatin in plasma was found to be 0.8 and 2.3 h.

Hemodynamic changes associated with reduction in total cholesterol by treatment with the HMG-CoA reductase inhibitor pravastatin

Hemodynamic changes associated with the lowering of total cholesterol (TC) by the water-soluble HMG-COA reductase inhibitor pravastatin were investigated in 59 patients with hypercholesterolemia (TC level at least 220 mg/dl) who received pravastatin therapy for 6 months. The patients were divided into two groups according to the reduction in TC: a ⩾15% reduction group and a <15% reduction group. The changes in hemodynamics were compared before and after pravastatin treatment. No changes in blood pressure, heart rate or aortic damping factor were found in either group. However, significant decreases in pulse wave velocity and total peripheral resistance, and increase in cardiac output were seen in the ⩾15% reduction group. All these hemodynamic parameters remained unchanged in the <15% reduction group. The 12 patients with a clear pravastatin-induced reduction in TC maintained over a 5-year period showed no changes in blood pressure, heart rate or aortic damping factor, but the reductions in pulse wave velocity and total peripheral resistance, and increase in cardiac output were maintained. These changes in hemodynamics were not dependent on aortic elasticity, and appeared to result from improved peripheral hemodynamics. Lowering of TC levels by pravastatin results in improvement in the peripheral endothelium-dependent vasodilation disorder associated with hypercholesterolemia.

Effects of low-dose pravastatin sodium on plasma cholesterol levels and aortic atherosclerosis of heterozygous WHHL rabbits fed a low cholesterol (0.03%) enriched diet for one year

The aim of this study was to evaluate the cholesterol-lowering and antiatherosclerotic effect of the HMG-CoA reductase inhibitor pravastatin sodium at a dosage comparable to human therapy. Twelve heterozygous WHHL rabbits (13 months old) were fed 100 g per day of a low cholesterol (0.03%) enriched diet for 12 months. Six of these animals also received pravastatin sodium at a daily dose of 1 mg/kg body weight (verum group). In the verum group, total plasma cholesterol levels were lower by 47% ( P<0.05) and relative aortic plaque volume (% ratio of total plaque volume to the aortic lumen) was reduced by 78% ( P<0.05), when compared to the control group. Plaque composition was analysed at 30 cross-sectional levels of the entire aortic wall using a grid window. Compared to the control group, the plaque type, in terms of architecture and composition, was altered as follows: lesions in the verum group had no confluent atheromatous cores and showed a pattern of a diffuse mixture of the main plaque components with a decreased relative content of necrosis (−44%) and an increased relative content of smooth muscle cells (+19%), whereas the relative content of macrophage-derived foam cells and collagen were nearly unaffected. Furthermore, a similar plaque volume and type was observed in animals with comparable cholesterol profiles. There was no histologic evidence for structurally damaging effects of pravastatin sodium on the arterial wall. We conclude that pravastatin sodium reduces total plasma cholesterol levels in this animal model, thereby leading to smaller plaques and a different plaque type.

Does the HMG-CoA reductase inhibitor pravastatin influence nucleation of cholesterol crystals in supersaturated model bile?

To assess whether the presence in bile of HMG-CoA reductase inhibitors, which are secreted predominantly into the bile, influences biliary lithogenicity. Physiologic biliary concentrations of the hydrophilic HMG-CoA reductase inhibitor pravastatin were added to supersaturated model bile (cholesterol saturation index 1.4) and vesicles, the latter with and without the concomitant addition of the nucleation-promoting bile salt taurodeoxycholate. Nucleation time, defined as the number of days after which cholesterol monohydrate crystals are visible by phase contrast microscopy in filtered samples of model bile and vesicles, was assessed. The addition of pravastatin 0.01-1 mg/ml did not influence the nucleation time of supersaturated model bile (mean nucleation time without pravastatin: 8.3 +/- 2.2 days (SD), with pravastatin 1 mg/ml 9.3 +/- 0.4 days and pravastatin 0.01 mg/ml 7.6 +/- 2.3 days). The addition of similar concentrations of pravastatin to vesicle fractions alone did not influence nucleation time (> 20 days), nor could it prevent the nucleation-promoting effect of taurodeoxycholate (nucleation time with or without pravastatin 1 day). The results from this in-vitro study indicate that the presence of pravastatin in bile may not influence gallbladder bile lithogenicity. It can be hypothesized that this also applies to other HMG-CoA reductase inhibitors.

The transporter for the HMG-CoA reductase inhibitor pravastatin is not present in Hep G2 cells. Evidence for the nonidentity of the carrier for pravastatin and certain transport systems for BSP

The hydrophilic HMG-CoA reductase inhibitor pravastatin is not taken up via a carrier-mediated system into Hep G2 cells. Therefore, Hep G2 cells are not a good model for human hepatocytes with respect to elucidation of the effect of hydrophilic HMG-CoA reductase inhibitors. Sulfobromophthalein (BSP), on the other hand, is taken up into Hep G2 cells by carrier systems with K m and V max values almost identical to freshly isolated hepatocytes. These results indicate that the hepatocellular BSP transporting proteins expressed in Hep G2 cells (bilitranslocase and BSP/bilirubin binding protein) are not involved in the hepatocellular uptake of pravastatin. In contrast to the hepatocellular sodium-taurocholate cotransporter, which is not functioning in Hep G2 cells, we found a saturable transport of cholate with K m and V max values identical to those in cultured rat hepatocytes in the presence of sodium.