Assessment of the Preventive Effect of L-carnitine on Post-statin Muscle Damage in a Zebrafish Model.

Statins, such as lovastatin, are lipid-lowering drugs (LLDs) that have been used to treat hypercholesterolaemia, defined as abnormally elevated cholesterol levels in the patient's blood. Although statins are considered relatively safe and well tolerated, recipients may suffer from adverse effects, including post-statin myopathies. Many studies have shown that supplementation with various compounds may be beneficial for the prevention or treatment of side effects in patients undergoing statin therapy. In our study, we investigated whether L-carnitine administered to zebrafish larvae treated with lovastatin alleviates post-statin muscle damage. We found that exposure of zebrafish larvae to lovastatin caused skeletal muscle disruption observed as a reduction of birefringence, changes in muscle ultrastructure, and an increase in atrogin-1. Lovastatin also affected heart performance and swimming behaviour of larvae. Our data indicated that the muscle-protective effect of L-carnitine is partial. Some observed myotoxic effects, such as disruption of skeletal muscle and increase in atrogin-1 expression, heart contraction could be rescued by the addition of L-carnitine. Others, such as slowed heart rate and reduced locomotion, could not be mitigated by L-carnitine supplementation.

A preclinical assessment to repurpose drugs to target type 1 diabetes-associated type B coxsackieviruses.

AIM: To screen several antiviral drugs systematically for their efficacy against type B coxsackieviruses. METHODS: Ten drugs with different antiviral mechanisms were analysed for their efficacy against prototype strains of type B coxsackieviruses in A549 cells. Cell viability was quantified in fixed cells using a colorimetric assay. Median effective dose was interpolated from the triplicated experiments and the dose-response curves were generated for each drug-virus combination. Drug cytotoxicity was similarly quantified and selectivity indices calculated. RESULTS: Hizentra, pleconaril, fluoxetine, norfluoxetine, ribavirin, favipiravir, and guanidine hydrochloride were able to abrogate infection by all tested viruses, with the exception of complete inefficacy of pleconaril against coxsackievirus B3 and favipiravir against coxsackievirus B2. The effective doses for Hizentra, enviroxime, ribavirin, favipiravir, and pleconaril were clearly below their therapeutic serum concentrations, while the effective concentrations of fluoxetin, norfluoxetine and itraconazole exceeded their therapeutic serum concentrations. Lovastatin and azithromycin did not efficiently block type B coxsackieviruses. CONCLUSION: Hizentra, enviroxime, pleconaril, ribavirin, and favipiravir are effective against type B coxsackieviruses in vitro in their therapeutic serum concentrations. These antiviral drugs are therefore attractive candidates for type 1 diabetes prevention/treatment trials. They can also be used in other clinical conditions caused by type B coxsackieviruses.

In Vitro Assessment of CYP-Mediated Drug Interactions for Kinsenoside, an Antihyperlipidemic Candidate.

Kinsenoside, the herb-derived medicine isolated from the plant Anoect chilus, has diverse pharmacological actions, and it is considered to be a promising antihyperlipidemic drug candidate. This study evaluates the effects of kinsenoside on CYP enzyme-mediated drug metabolism in order to predict the potential for kinsenoside-drug interactions. Kinsenoside was tested at different concentrations of 0.1, 0.3, 1, 3, 10, 30, and 100 µM in human liver microsomes. The c Cktail probe assay based on liquid chromatography-tandem mass spectrometry was conducted to measure the CYP inhibitory effect of kinsenoside. Subsequently, the metabolism profiles of amlodipine and lovastatin in human liver microsomes were analyzed following co-incubation with kinsenoside. The concentration levels of the parent drug and the major metabolites were compared with the kinsenoside-cotreated samples. The effect of kinsenoside was negligible on the enzyme activity of all the CYP isozymes tested even though CYP2A6 was slightly inhibited at higher concentrations. The drug-drug interaction assay also showed that the concomitant use of kinsenoside has a non-significant effect on the concentration of lovastatin or amlodipine, and their major metabolites. So, it was concluded that there is almost no risk of drug interaction between kinsenoside and CYP drug substrates via CYP inhibition.

Assessment of cholesterol homeostasis in astrocytes and neurons.

Cholesterol homeostasis is highly regulated in the nervous system; dysregulation in cholesterol trafficking and content have been involved in the pathogenesis of neurodegenerative diseases (such as Parkinson's and Alzheimer's diseases). Furthermore, low cholesterol levels during brain development are associated with neurodevelopmental deficits and mental retardation. The methods described in this chapter can be used to investigate the effect of neurotoxicants on cholesterol homeostasis. Astrocytes and neurons are two major cell types in the brain in which cholesterol synthesis and efflux are highly regulated to keep a proper cellular cholesterol level. Disruption in cholesterol synthesis and/or cholesterol efflux may result in cholesterol deficiency or accumulation in these cells leading to brain dysfunctions.

A simultaneous assessment of CYP3A4 metabolism and induction in the DPX-2 cell line.

The DPX-2 cell line, a derivative of HepG2 cells, harbors human PXR and a luciferase-linked CYP3A4 promoter. These cells were used in a panel of cell-based assays for a parallel assessment of CYP3A4 induction, metabolism, and inhibition at the cellular level. CYP3A4 induction in the DPX-2 cell line by various agents was monitored in 96-well plates by a luciferase-based transcriptional activation assay. Of the prototypical CYP3A4 inducers examined, all exhibited elevated luciferase activity in DPX-2 cells. CYP3A4 enzyme activity in noninduced and rifampicin-induced DPX-2 cells was also assessed using Vivid fluorogenic substrates. Significantly elevated CYP3A4 activity levels (2.8-fold +/- 0.2-fold above DMSO-treated cells) were found in DPX-2 cells after 48 hours of exposure to rifampicin, but were undetectable in parental HepG2 cells. Rifampicin-induced activity levels were found to be suitable for assessing the inhibitory potential of new chemical entities in downstream CYP3A4 inhibition assays. The elevated CYP3A4 activity was inhibited 85% by 10 microM ketoconazole. In addition, a cytotoxicity assay to correct for possible toxic effects of compounds at the cellular level was applied. The comparative data obtained with a combination of the above assays suggests that the application of several independent in vitro technologies used in DPX-2 cells is the best possible strategy for the assessment of the complex phenomena of CYP3A4 induction and inhibition.

The 4S study. Implications for prescribing.

This article discusses various aspects of cholesterol-lowering therapy using the HMG-CoA reductase inhibitor simvastatin in the light of the large Scandinavian Simvastatin Survival Study (4S). In 4S, patients with proven coronary heart disease (CHD) and plasma total cholesterol > 5.5 mmol/L (212 mg/dl) despite dietary measures received statin therapy or placebo for > or = 5 years. A significant mortality reduction was accomplished in those receiving the statin. Moreover, a significant decrease of nonfatal myocardial infarction and requirement for coronary bypass surgery or angioplasty was demonstrated, which will contribute to the cost-effectiveness of this well tolerated therapy. Plaque stabilisation and improvement of endothelial function are thought to be mediators of this therapeutic success. Responsible drug prescription in the post-4S era may result in the recognition and treatment of more patients with CHD. This is likely to be more beneficial than exhaustive efforts to completely achieve the goals of the most strict guidelines in the individual patient. In patients who carry the highest absolute risk for a recurrent event, aggressive drug therapy may be most justified. Reluctance to initiate lipid lowering drug therapy in patients with proven CHD should now be disputed.

Simvastatin. A reappraisal of its pharmacology and therapeutic efficacy in hypercholesterolaemia.

Simvastatin is an HMG-CoA reductase inhibitor used in the treatment of patients with hypercholesterolaemia. Since the time simvastatin was previously reviewed in Drugs, a number of large clinical trials have confirmed its clinical efficacy. Thus, reductions from baseline were approximately 20 to 40% for serum levels of total cholesterol, 35 to 45% for low density lipoprotein (LDL)-cholesterol and 10 to 20% for triglycerides in patients with primary hypercholesterolaemia receiving simvastatin 10 to 40 mg/day. High density lipoprotein (HDL)-cholesterol levels were increased modestly by about 5 to 15%. Recent data from long term studies indicate that little or no attenuation of these changes in serum lipid and lipoprotein levels occurred with administration of simvastatin for 3 to 5.4 years. Comparative studies with other HMG-CoA reductase inhibitors (lovastatin, pravastatin and fluvastatin), which were lacking at the time of the previous review of simvastatin, demonstrated greater reductions in serum levels of total cholesterol and LDL-cholesterol with simvastatin than equal dosages of lovastatin or pravastatin. Reductions in serum levels of total cholesterol and LDL-cholesterol were similar between agents only when lovastatin or pravastatin were administered at a total daily dosage twice that of simvastatin and when fluvastatin was administered at a total daily dosage approximately 8 times that of simvastatin. In general, simvastatin 10 to 40 mg/day was also more effective than standard dosages of bile acid sequestrants, fibrates or probucol in lowering serum levels of total cholesterol and LDL-cholesterol; however, fibrates usually produced greater reductions in serum triglycerides and greater elevations in HDL-cholesterol levels. The Scandinavian Simvastatin Survival Study (4S), a large secondary prevention study in patients with coronary heart disease and concomitant hypercholesterolaemia, demonstrated that simvastatin 20 to 40 mg/day for a median of 5.4 years significantly reduced overall mortality (the primary end-point of the study) by 30% compared with placebo, which was attributed to a 42% relative reduction in coronary mortality. Coronary morbidity was also significantly reduced by simvastatin in the 4S trial. The tolerability profile of simvastatin appears to be comparable to that of other HMG-CoA reductase inhibitors. The most frequently reported adverse events are gastrointestinal disturbances, which are generally mild and tend to occur less frequently than with cholestyramine. In conclusion, simvastatin is among the most effective agents available for treating patients with hypercholesterolaemia.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparative evaluation of the safety and efficacy of HMG-CoA reductase inhibitor monotherapy in the treatment of primary hypercholesterolemia.

OBJECTIVE: To evaluate the comparative efficacy and safety of the 4 currently available hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors, fluvastatin, lovastatin, pravastatin, and simvastatin, in the treatment of primary hypercholesterolemia. DATA SOURCES: English-language clinical studies, abstracts, and review articles identified from MEDLINE searches and bibliographies of identified articles. Unpublished data were obtained from the Food and Drug Administration in accordance with the Freedom of Information Act. STUDY SELECTION: Placebo-controlled and comparative studies of HMG-CoA reductase inhibitor monotherapy in the treatment of primary hypercholesterolemia. DATA EXTRACTION: Pertinent studies were selected and the data were synthesized into a review format. DATA SYNTHESIS: The chemistry, pharmacology, and pharmacokinetics of the 4 HMG-CoA reductase inhibitors are reviewed. Clinical trials evaluating the hypocholesterolemic efficacy of the HMG-CoA reductase inhibitors are examined, and results on the comparative efficacy and safety of these agents are summarized. On a milligram-per-milligram basis, simvastatin is twice as potent as lovastatin and pravastatin. The hypocholesterolemic effects of fluvastatin appear to be approximately 30% less than that of lovastatin. In posttransplant patients receiving cyclosporine, safety has been documented for low doses of lovastatin and simvastatin, but when a higher dosage of an HMG-CoA reductase inhibitor is warranted, pravastatin should be considered the drug of choice because of a lower incidence of myopathy. Relevant data on the incidence of adverse effects are presented. Pertinent outcomes data from clinical trials evaluating the effect of HMG-CoA reductase inhibitors on atherosclerosis regression and coronary mortality, as well as published economic analyses of cholesterol-lowering agents, are summarized. Recommendations on the selection of an HMG-CoA reductase inhibitor in various clinical situations are provided. CONCLUSIONS: The literature supports the comparable safety and tolerability of all 4 currently available HMG-CoA reductase inhibitors. Therefore, the choice of an HMG-CoA reductase inhibitor should depend on the extent of cholesterol lowering needed to meet the recommended treatment goal established by the National Cholesterol Education Program. Direct comparative studies are needed to confirm the relative, long-term cost-effectiveness of the various HMG-CoA reductase inhibitors in the treatment of primary hypercholesterolemia.

Replacing lovastatin with pravastatin: effect on serum lipids and costs.

The effects on costs and lipid levels of replacing lovastatin therapy with pravastatin were studied. Beginning in April 1992, outpatients receiving lovastatin were switched to pravastatin. Physicians were asked but not required to initiate the pravastatin sodium treatment at half the daily lovastatin dose in milligrams. In October 1993, the dosages of lovastatin and pravastatin and the corresponding lipid-profile results were recorded for each patient for whom lovastatin had been replaced by pravastatin. The drug acquisition cost per year of therapy was calculated for each patient's most recent dosage of lovastatin and pravastatin as of April 1993. The costs used in the analysis were the most recent available (March 1995). Lovastatin therapy was changed to pravastatin in a total of 168 patients. Of the 168 patients, 145 (86%) were prescribed an initial daily pravastatin sodium dose that was at least 50% lower in milligrams than that of lovastatin. All of the 168 patients who received pravastatin had two usable total-cholesterol measurements during lovastatin therapy, and 148 (88%) had at least one such measurement during pravastatin therapy. Among patients with usable serum-lipid data, there was no significant difference between any of the mean serum lipid concentration (total cholesterol, low-density-lipoprotein cholesterol, or high-density-lipoprotein cholesterol) before and after the conversion. The annual cost of lovastatin for the 148 patients would be $71,693 for the most recent dosages; the corresponding cost for pravastatin would be $56,875 (21% lower). The replacement of lovastatin with pravastatin sodium was associated with a 21% cost reduction but no significant change in mean serum lipid concentrations.

Measurement of bile acid synthesis in man by release of 14CO2 from [26-14C]cholesterol: comparison to isotope dilution and assessment of optimum cholesterol specific activity.

Bile acid synthesis can be measured as release of 14CO2 from [26-14C]cholesterol divided by cholesterol specific activity, but this method has not been validated in human subjects. We made twelve comparisons of this CO2 method to standard isotope dilution in six normal subjects and found a mean discrepancy of 6%. Linear regression analysis of one value with respect to the other revealed a correlation coefficient of 0.83 (P less than 0.01), a Y-intercept close to zero (-4.98) and a slope close to 1 (1.06), suggesting good correspondence between the two methods. To assess the potential for error arising from use of serum cholesterol to estimate specific activity of cholesterol used for bile acid synthesis, we compared synthesis measured using serum free cholesterol specific activity to that measured using bile cholesterol specific activity, which is known to be near isotopic equilibrium with the precursor pool used for bile acid synthesis. Synthesis calculated in these two ways differed by less than 10%. The data indicate that the CO2 method using either serum or bile cholesterol specific activity provides a valid estimate of bile acid synthesis in man.

Assessment of functional low-density lipoprotein receptor activity on lymphocytes of normal subjects and patients with familial hypercholesterolemia.

In FH, abnormalities of the gene encoding the receptor for LDL lead to hypercholesterolemia and premature atherosclerosis. A method to identify LDL receptor defects using peripheral blood lymphocytes has been developed. When endogenous synthesis of cholesterol was blocked, proliferation of mitogen-stimulated normal human lymphocytes was markedly inhibited unless an exogenous source of sterol was supplied. When exogenous sterol was provided as a plasma lipoprotein, LDL receptor-mediated interaction with apolipoprotein-B or -E was essential for the provision of cholesterol to normal human lymphocytes. Thus, functional LDL receptors were necessary to permit proliferation of normal lymphocytes in these cultures. Lymphocytes from patients heterozygous for abnormalities in the LDL receptor gene can be distinguished from normal lymphocytes by their diminished functional LDL receptor activity. Of interest, following treatment with plasma cholesterol-lowering agents, functional lymphocyte LDL receptor activity normalized in some but not all patients with heterozygous FH, whereas plasma LDL cholesterol levels decreased in all patients. These results suggest that therapy with plasma cholesterol-lowering agents can lead to increased expression of LDL receptors by lymphocytes in the majority of patients with heterozygous FH. The failure of some heterozygous FH patients to increase functional LDL receptor activity after prolonged therapy indicates that there is heterogeneity in these patients despite a similar capacity of the therapy to decrease plasma LDL cholesterol. Variability in the expression of the normal LDL receptor gene in individual T lymphocytes may account for some of these findings.