The role of acid-base imbalance in statin-induced myotoxicity

Effect of statins on mitochondrial function and contractile force in human skeletal and cardiac muscle

OBJECTIVES AND BACKGROUND

The success of statin therapy in reducing cardiovascular morbidity and mortality is contrasted by the skeletal muscle complaints, which often leads to nonadherence. Previous studies have shown that inhibition of mitochondrial function plays a key role in statin intolerance. Recently, it was found that statins may also influence energy metabolism in cardiomyocytes. This study assessed the effects of statin use on cardiac muscle ex vivo from patients using atorvastatin, rosuvastatin, simvastatin or pravastatin and controls.

METHODS

Cardiac tissue and skeletal muscle tissue were harvested during open heart surgery after patients provided written informed consent. Patients included were undergoing cardiac surgery and either taking statins (atorvastatin, rosuvastatin, simvastatin or pravastatin) or without statin therapy (controls). Contractile behaviour of cardiac auricles was tested in an ex vivo set-up and cellular respiration of both cardiac and skeletal muscle tissue samples was measured using an Oxygraph-2k. Finally, statin acid and lactone concentrations were quantified in cardiac and skeletal homogenates by LC-MS/MS.

RESULTS

Fatty acid oxidation and mitochondrial complex I and II activity were reduced in cardiac muscle, while contractile function remained unaffected. Inhibition of mitochondrial complex III by statins, as previously described, was confirmed in skeletal muscle when compared to control samples, but not observed in cardiac tissue. Statin concentrations determined in skeletal muscle tissue and cardiac muscle tissue were comparable.

CONCLUSIONS

Statins reduce skeletal and cardiac muscle cell respiration without significantly affecting cardiac contractility.

Interindividual variability in statin pharmacokinetics and effects of drug transporters

INTRODUCTION

Statins are HMG-CoA reductase inhibitors that primarily lower plasma cholesterol levels. It has been suggested that the myotoxic response is a direct result of hydroxymethylglutaryl-CoA reductase inhibition and dose-dependent. Therefore, an accurate understanding of the combination of drugs that inhibit statin metabolism and factors that cause interindividual variability in the pharmacokinetics of statin is important to avoid serious side effects of statins. Relevant articles included in this review were identified through a PubMed search (through May 2023).

AREAS COVERED

This review provides an overview of hepatic and intestinal metabolism of statins, followed by a discussion of drug-drug interactions and interindividual variables that influence statin pharmacokinetics: gut bacteria, disease, and pharmacokinetics-related genetic polymorphisms.

EXPERT OPINION

Drug-drug interactions have a strong influence on statin pharmacokinetics, and gut microbiota, disease, and genetic polymorphisms all contribute significantly to interindividual variation in statin pharmacokinetics. Individual optimization of statin treatment requires studies that consider the progression of the disease and associated changes in concomitant medications.

One-Step Microwell Plate-Based Spectrofluorimetric Assay for Direct Determination of Statins in Bulk Forms and Pharmaceutical Formulations: A Green Eco-Friendly and High-Throughput Analytical Approach

This study describes the development of a one-step microwell spectrofluorimetric assay (MW-SFA) with high sensitivity and throughput for the determination of four statins in their pharmaceutical and formulations (tablets). These statins were pitavastatin (PIT), fluvastatin (FLU), rosuvastatin (ROS) and atorvastatin (ATO). The MW-SFA involves the measurement of the native fluorescence of the statin aqueous solutions. The assay was conducted in white opaque 96-microwell plates, and the fluorescence intensities of the solutions were measured by using a fluorescence microplate reader. The optimum conditions of the assay were established; under which, linear relationships with good correlation coefficients (0.9991-0.9996) were found between the fluorescence intensity and the concentration of the statin drug in a range of 0.2-200 µg mL^-1 with limits of detection in a range of 0.1-4.1 µg mL^-1. The proposed MW-SFA showed high precision, as the values of the relative standard deviations did not exceed 2.5%. The accuracy of the assay was proven by recovery studies, as the recovery values were 99.5-101.4% (±1.4-2.1%). The assay was applied to the determination of the investigated statins in their tablets. The results were statistically compared with those obtained by a reference method and the results proved to have comparable accuracy and precision of both methods, as evidenced by the t- and F-tests, respectively. The green and eco-friendly feature of the proposed assay was assessed by four different metric tools, and all the results proved that the assay meets the requirements of green and eco-friendly analytical approaches. In addition, ever-increasing miniaturization as handling of large numbers of micro-volume samples simultaneously in the proposed assay gave it a high-throughput feature. Therefore, the assay is a valuable tool for the rapid routine application in the pharmaceutical quality control units for the determination of statins.

Statin activation of skeletal ryanodine receptors (RyR1) is a class effect but separable from HMG-CoA reductase inhibition

BACKGROUND AND PURPOSE

Statins, inhibitors of HMG-CoA reductase, are mainstay treatment for hypercholesterolaemia. However, muscle pain and weakness prevent many patients from benefiting from their cardioprotective effects. We previously demonstrated that simvastatin activates skeletal ryanodine receptors (RyR1), an effect that could be important in initiating myopathy. Using a range of structurally diverse statin analogues, we examined structural features associated with RyR1 activation, aiming to identify statins lacking this property.

EXPERIMENTAL APPROACH

Compounds were screened for RyR1 activity utilising [3 H]ryanodine binding. Mechanistic insight into RyR1 activity was studied by incorporating RyR1 channels from sheep, mouse or rabbit skeletal muscle into bilayers.

KEY RESULTS

All UK-prescribed statins activated RyR1 at nanomolar concentrations. Cerivastatin, withdrawn from the market due to life-threatening muscle-related side effects, was more effective than currently-prescribed statins and possessed the unique ability to open RyR1 channels independently of cytosolic Ca2+ . We synthesised the one essential structural moiety that all statins must possess for HMG-CoA reductase inhibition, the R-3,5-dihydroxypentanoic acid unit, and it did not activate RyR1. We also identified five analogues retaining potent HMG-CoA reductase inhibition that inhibited RyR1 and four that lacked the ability to modulate RyR1.

CONCLUSION AND IMPLICATIONS

That cerivastatin activates RyR1 most strongly supports the hypothesis that RyR1 activation is implicated in statin-induced myopathy. Demonstrating that statin regulation of RyR1 and HMG-CoA reductase are separable effects will allow the role of RyR1 in statin-induced myopathy to be further elucidated by the tool compounds we have identified, allowing development of effective cardioprotective statins with improved patient tolerance.

Simvastatin Coadministration Modulates the Electrostatically Driven Incorporation of Doxorubicin into Model Lipid and Cell Membranes

Understanding the interactions between drugs and lipid membranes is a prerequisite for finding the optimal way to deliver drugs into cells. Coadministration of statins and anticancer agents has been reported to have a positive effect on anticancer therapy. In this study, we elucidate the mechanism by which simvastatin (SIM) improves the efficiency of biological membrane penetration by the chemotherapeutic agent doxorubicin (DOX) in neutral and slightly acidic solutions. The incorporation of DOX, SIM, or a combination of them (DOX:SIM) into selected single-component lipid membranes, zwitterionic unsaturated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), neutral cholesterol, and negatively charged 1,2-dimyristoyl-sn-glycero-3-phospho-l-serine (DMPS) was assessed using the Langmuir method. The penetration of neutral lipid monolayers by the codelivery of SIM and DOX was clearly facilitated at pH 5.5, which resembles the pH conditions of the environment of cancer cells. This effect was ascribed to partial neutralization of the DOX positive charge as the result of intermolecular interactions between DOX and SIM. On the other hand, the penetration of the negatively charged DMPS monolayer was most efficient in the case of the positively charged DOX. The efficiency of the drug delivery to the cell membranes was evaluated under in vitro conditions using a panel of cancer-derived cell lines (A172, T98G, and HeLa). MTS and trypan blue exclusion assays were performed, followed by confocal microscopy and spheroid culture tests. Cells were exposed to either free drugs or drugs encapsulated in lipid carriers termed cubosomes. We demonstrated that the viability of cancer cells exposed to DOX was significantly impaired in the presence of SIM, and this phenomenon was greatly magnified when DOX and SIM were coencapsulated in cubosomes. Overall, our results confirmed the utility of the DOX:SIM combination delivery, which enhances the interactions between neutral components of cell membranes and positively charged chemotherapeutic agents.

Hydrophilic Versus Lipophilic Statin Treatments in Patients With Renal Impairment After Acute Myocardial Infarction

Background Hydrophilic and lipophilic statins have similar efficacies in treating coronary artery disease. However, specific factors relevant to renal impairment and different arterial pathogeneses could modify the clinical effects of statin lipophilicity, and create differences in protective effects between statin types in patients with renal impairment. Methods and Results A total of 2062 patients with acute myocardial infarction with an estimated glomerular filtration rate <60 mL/min per 1.73 m² were enrolled from the Korea Acute Myocardial Infarction Registry between November 2011 and December 2015. The primary end point was a composite of 2-year major adverse cardiac and cerebrovascular events (MACEs) after acute myocardial infarction occurrence. MACEs were defined as all-cause death, recurrent myocardial infarction, revascularization, and stroke. Propensity-score matching and Cox proportional hazards regression were performed. A total of 529 patients treated with hydrophilic statins were matched to 529 patients treated with lipophilic statins. There was no difference in the statin equivalent dose between the 2 statin groups. The cumulative event rate of MACEs, all-cause mortality, and recurrent myocardial infarction were significantly lower in patients treated with hydrophilic statins in the propensity-score matched population (all P<0.05). In the multivariable Cox regression analysis, patients treated with hydrophilic statins had a lower risk for composite MACEs (hazard ratio [HR], 0.70 [95% CI, 0.55-0.90]), all-cause mortality (HR, 0.67 [95% CI, 0.49-0.93]), and recurrent myocardial infarction (HR, 0.40 [95% CI, 0.21-0.73]), but not for revascularization and ischemic stroke. Conclusions Hydrophilic statin treatment was associated with lower risk of MACEs and all-cause mortality than lipophilic statin in a propensity-score matched observational cohort of patients with renal impairment following acute myocardial infarction.

Role of Drug-Gene Interactions and Pharmacogenetics in Simvastatin-Associated Pulmonary Toxicity

Introduction

Simvastatin has previously been associated with drug-induced interstitial lung disease. In this retrospective observational study, cases with non-specific interstitial pneumonia (NSIP) or idiopathic pulmonary fibrosis (IPF) with simvastatin-associated pulmonary toxicity (n = 34) were evaluated.

Objective

To identify whether variations in genes encoding cytochrome P450 (CYP) enzymes or in the SLCO1B1 gene (Solute Carrier Organic anion transporting polypeptide 1B1 gene, encoding the organic anion transporting polypeptide 1B1 [OATP1B1] drug transporter enzyme), and/or characteristics of concomitantly used drugs, predispose patients to simvastatin-associated pulmonary toxicity.

Methods

Characteristics of concomitantly used drugs and/or variations in the CYP or SLCO1B1 genes and drug–gene interactions were assessed. The outcome after withdrawal of simvastatin and/or switch to another statin was assessed after 6 months.

Results

Multiple drug use involving either substrates and/or inhibitors of CYP3A4 and/or three or more drugs with the potential to cause acidosis explained the simvastatin-associated toxicity in 70.5% (n = 24) of cases. Cases did not differ significantly from controls regarding CYP3A4, CYP2C9, or OATP1B1 phenotypes, and genetic variation explained only 20.6% (n = 7) of cases. Withdrawal of simvastatin without switching to another statin or with a switch to a hydrophilic statin led to improvement or stabilization in all NSIP cases, whereas all cases who were switched to the lipophilic atorvastatin progressed.

Conclusion

Simvastatin-associated pulmonary toxicity is multifactorial. For patients with this drug-induced pulmonary toxicity who need to continue taking a statin, switching to a hydrophilic statin should be considered.

ClinicalTrials.gov identifier

NCT00267800, registered in 2005.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40264-021-01105-8.

Modulation of Phospholipid Bilayer Properties by Simvastatin

Simvastatin (Zocor) is one of the most prescribed drugs for reducing high cholesterol. Although simvastatin is ingested in its inactive lactone form, it is converted to its active dihydroxyheptanoate form by carboxylesterases in the liver. The dihydroxyheptanoate form can also be converted back to its original lactone form. Unfortunately, some of the side effects associated with the intake of simvastatin and other lipophilic statins at higher doses include statin-associated myopathy (SAM) and, in more severe cases, kidney failure. While the cause of SAM is unknown, it is hypothesized that these side effects are dependent on the localization of statins in lipid bilayers and their impact on bilayer properties. In this work, we carry out all-atom molecular dynamics simulations on both the lactone and dihydroxyheptanoate forms of simvastatin (termed "SN" and "SA", respectively) with a pure 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipid bilayer and a POPC/cholesterol (30 mol %) binary mixture as membrane models. Additional simulations were carried out with multiple simvastatin molecules to mimic in vitro conditions that produced pleiotropic effects. Both SN and SA spontaneously diffused into the lipid bilayer, and a longer simulation time of 4 μs was needed for the complete incorporation of multiple SAs into the bilayer. By constructing potential mean force and electron density profiles, we find that SN localizes deeper within the hydrophobic interior of the bilayer and that SA has a greater tendency to form hydrogen-bonding interactions with neighboring water molecules and lipid headgroups. For the pure POPC bilayer, both SN and SA increase membrane order, while membrane fluidity increases for the POPC/cholesterol bilayer.

Effects of statins on mitochondrial pathways

Statins are a family of drugs that are used for treating hyperlipidaemia with a recognized capacity to prevent cardiovascular disease events. They inhibit β-hydroxy β-methylglutaryl-coenzyme A reductase, i.e. the rate-limiting enzyme in mevalonate pathway, reduce endogenous cholesterol synthesis, and increase low-density lipoprotein clearance by promoting low-density lipoprotein receptor expression mainly in the hepatocytes. Statins have pleiotropic effects including stabilization of atherosclerotic plaques, immunomodulation, anti-inflammatory properties, improvement of endothelial function, antioxidant, and anti-thrombotic action. Despite all beneficial effects, statins may elicit adverse reactions such as myopathy. Studies have shown that mitochondria play an important role in statin-induced myopathies. In this review, we aim to report the mechanisms of action of statins on mitochondrial function. Results have shown that statins have several effects on mitochondria including reduction of coenzyme Q10 level, inhibition of respiratory chain complexes, induction of mitochondrial apoptosis, dysregulation of Ca2+ metabolism, and carnitine palmitoyltransferase-2 expression. The use of statins has been associated with the onset of additional pathological conditions like diabetes and dementia as a result of interference with mitochondrial pathways by various mechanisms, such as reduction in mitochondrial oxidative phosphorylation, increase in oxidative stress, decrease in uncoupling protein 3 concentration, and interference in amyloid-β metabolism. Overall, data reported in this review suggest that statins may have major effects on mitochondrial function, and some of their adverse effects might be mediated through mitochondrial pathways.

Simvastatin profoundly impairs energy metabolism in primary human muscle cells

OBJECTIVES

Simvastatin use is associated with muscular side effects, and increased risk for type 2 diabetes (T2D). In clinical use, simvastatin is administered in inactive lipophilic lactone-form, which is then converted to active acid-form in the body. Here, we have investigated if lactone- and acid-form simvastatin differentially affect glucose metabolism and mitochondrial respiration in primary human skeletal muscle cells.

METHODS

Muscle cells were exposed separately to lactone- and acid-form simvastatin for 48 h. After pre-exposure, glucose uptake and glycogen synthesis were measured using radioactive tracers; insulin signalling was detected with Western blotting; and glycolysis, mitochondrial oxygen consumption and ATP production were measured with Seahorse XFe96 analyzer.

RESULTS

Lactone-form simvastatin increased glucose uptake and glycogen synthesis, whereas acid-form simvastatin did not affect glucose uptake and decreased glycogen synthesis. Phosphorylation of insulin signalling targets Akt substrate 160 kDa (AS160) and glycogen synthase kinase 3β (GSK3β) was upregulated with lactone-, but not with acid-form simvastatin. Exposure to both forms of simvastatin led to a decrease in glycolysis and glycolytic capacity, as well as to a decrease in mitochondrial respiration and ATP production.

CONCLUSIONS

These data suggest that lactone- and acid-forms of simvastatin exhibit differential effects on non-oxidative glucose metabolism as lactone-form increases and acid-form impairs glucose storage into glycogen, suggesting impaired insulin sensitivity in response to acid-form simvastatin. Both forms profoundly impair oxidative glucose metabolism and energy production in human skeletal muscle cells. These effects may contribute to muscular side effects and risk for T2D observed with simvastatin use.

Pharmacogenetics of Statin-Induced Myotoxicity

Statins, a class of lipid-lowering medications, have been a keystone treatment in cardiovascular health. However, adverse effects associated with statin use impact patient adherence, leading to statin discontinuation. Statin-induced myotoxicity (SIM) is one of the most common adverse effects, prevalent across all ages, genders, and ethnicities. Although certain demographic cohorts carry a higher risk, the impaired quality of life attributed to SIM is significant. The pathogenesis of SIM remains to be fully elucidated, but it is clear that SIM is multifactorial. These factors include drug-drug interactions, renal or liver dysfunction, and genetics. Genetic-inferred risk for SIM was first reported by a landmark genome-wide association study, which reported a higher risk of SIM with a polymorphism in the SLCO1B1 gene. Since then, research associating genetic factors with SIM has expanded widely and has become one of the foci in the field of pharmacogenomics. This review provides an update on the genetic risk factors associated with SIM.

The PPAR Ω Pocket: Renewed Opportunities for Drug Development

The past decade of PPARγ research has dramatically improved our understanding of the structural and mechanistic bases for the diverging physiological effects of different classes of PPARγ ligands. The discoveries that lie at the heart of these developments have enabled the design of a new class of PPARγ ligands, capable of isolating central therapeutic effects of PPARγ modulation, while displaying markedly lower toxicities than previous generations of PPARγ ligands. This review examines the emerging framework around the design of these ligands and seeks to unite its principles with the development of new classes of ligands for PPARα and PPARβ/δ. The focus is on the relationships between the binding modes of ligands, their influence on PPAR posttranslational modifications, and gene expression patterns. Specifically, we encourage the design and study of ligands that primarily bind to the Ω pockets of PPARα and PPARβ/δ. In support of this development, we highlight already reported ligands that if studied in the context of this new framework may further our understanding of the gene programs regulated by PPARα and PPARβ/δ. Moreover, recently developed pharmacological tools that can be utilized in the search for ligands with new binding modes are also presented.

Simvastatin Evokes An Unpredicted Antagonism For Tamoxifen In MCF-7 Breast Cancer Cells

Purpose

Tamoxifen (TAM) is a non-steroidal antiestrogen drug, used in the prevention and treatment of all stages of hormone-responsive breast cancer. Simvastatin (SIM) is a lipid-lowering agent and has been shown to inhibit cancer cell growth. The study aimed to investigate the effect of the combination of TAM and SIM in the treatment of estrogen receptor positive (ER+) breast cancer cell line, MCF-7, and in mice-bearing Ehrlich solid tumors.

Methods

MCF-7 cells were treated with different concentrations of TAM or/and SIM for 72 hours and the effects of the combination treatment on cytotoxicity, oxidative stress markers, apoptosis, angiogenesis, and metastasis were investigated using different techniques. In addition, tumor volume, oxidative markers, and inflammatory markers of the combined therapy were explored in mice bearing solid EAC tumors.

Results

The results showed that treatment of MCF-7 cells with the combination of 10 µM TAM, and 2 µM SIM significantly inhibited the increase in oxidative stress markers, LDH, and NF-kB induced by TAM. In addition, there was a significant decrease in the total apoptotic ratio, caspase-3 activity, and glucose uptake, while there was a non-significant change in Bax/bcl-2 ratio compared to the TAM-treated group. Using the isobologram equation, the drug interaction was antagonistic with combination index, CI=1.18. On the other hand, the combination regimen decreased VEGF, and matrix metalloproteinases, MMP 2&9 compared to TAM-treated cells. Additionally, in vivo, the combination regimen resulted in a non-significant decrease in the tumor volume, decreased oxidative markers, and the protein expression of TNF-α, and NF-κB compared to the TAM treated group.

Conclusion

Although the combination regimen of TAM and SIM showed an antagonistic drug interaction in MCF-7 breast cancer, it displayed favorable antiangiogenic, anti-metastatic, and anti-inflammatory effects.

Statin Toxicity

There is now overwhelming evidence to support lowering LDL-c (low-density lipoprotein cholesterol) to reduce cardiovascular morbidity and mortality. Statins are a class of drugs frequently prescribed to lower cholesterol. However, in spite of their wide-spread use, discontinuation and nonadherence remains a major gap in both the primary and secondary prevention of atherosclerotic cardiovascular disease. The major reason for statin discontinuation is because of the development of statin-associated muscle symptoms, but a range of other statin-induced side effects also exist. Although the mechanisms behind these side effects have not been fully elucidated, there is an urgent need to identify those at increased risk of developing side effects as well as provide alternative treatment strategies. In this article, we review the mechanisms and clinical importance of statin toxicity and focus on the evaluation and management of statin-associated muscle symptoms.

A novel nucleoside rescue metabolic pathway may be responsible for therapeutic effect of orally administered cordycepin

Although adenosine and its analogues have been assessed in the past as potential drug candidates due to the important role of adenosine in physiology, only little is known about their absorption following oral administration. In this work, we have studied the oral absorption and disposition pathways of cordycepin, an adenosine analogue. In vitro biopharmaceutical properties and in vivo oral absorption and disposition of cordycepin were assessed in rats. Despite the fact that numerous studies showed efficacy following oral dosing of cordycepin, we found that intact cordycepin was not absorbed following oral administration to rats. However, 3′-deoxyinosine, a metabolite of cordycepin previously considered to be inactive, was absorbed into the systemic blood circulation. Further investigation was performed to study the conversion of 3′-deoxyinosine to cordycepin 5′-triphosphate in vitro using macrophage-like RAW264.7 cells. It demonstrated that cordycepin 5′-triphosphate, the active metabolite of cordycepin, can be formed not only from cordycepin, but also from 3′-deoxyinosine. The novel nucleoside rescue metabolic pathway proposed in this study could be responsible for therapeutic effects of adenosine and other analogues of adenosine following oral administration. These findings may have importance in understanding the physiology and pathophysiology associated with adenosine, as well as drug discovery and development utilising adenosine analogues.

Evaluation of tamoxifen and simvastatin as the combination therapy for the treatment of hormonal dependent breast cancer cells

Tamoxifen (TAM) is a nonsteroidal antiestrogen drug, used in the prevention and treatment of all stages of hormone-responsive breast cancer. Simvastatin (SIM), a lipid-lowering agent, has been shown to inhibit cancer cell growth. The study aimed at investigating the impact of using SIM with TAM in estrogen receptor-positive (ER+) breast cancer cell line, T47D, as well as in mice-bearing Ehrlich solid tumor. The cell line was treated with different concentrations of TAM or/and SIM for 72 h. The effects of treatment on cytotoxicity, oxidative stress markers, apoptosis, angiogenesis, and metastasis were investigated. Our results showed that the combination treatment decreased the oxidative stress markers, glucose uptake, VEGF, and MMP 2 &9 in the cell line compared to TAM- treated cells. Drug interaction of TAM and SIM was synergistic in T47D by increasing the apoptotic makers Bax/BCL-2 ratio and caspase 3 activity. Additionally, in vivo, the combination regimen resulted in a non-significant decrease in the tumor volume compared to TAM treated group. Moreover, the combined treatment decreased the protein expression of TNF-α, NF-kB compared to control. In conclusion, our results suggest that SIM may serve as a promising treatment with TAM for improving the efficacy against estrogen receptor-positive (ER+) breast cancer.

Diabetogenic effect of pravastatin is associated with insulin resistance and myotoxicity in hypercholesterolemic mice

Background

HMG-CoA reductase inhibitors (statins) are cholesterol-lowering drugs widely used to treat hypercholesterolemia and prevent cardiovascular disease. Statins are generally well tolerated, but adverse reactions may occur, particularly myopathy and new onset of diabetes. The exact mechanism of statin-induced myopathy and diabetes has not been fully elucidated. We have previously shown that treatment of hypercholesterolemic (LDLr^−/−) mice with pravastatin for 2 months decreased pancreatic islet insulin secretion and increased oxidative stress and cell death, but no glucose intolerance was observed. The purpose of the current work was to study long-term pravastatin effects on glucose homeostasis, insulin sensitivity, muscle protein turnover and cell viability.

Methods

LDLr^−/− mice were treated with pravastatin for 3, 6 and 10 months. Glucose tolerance, insulin resistance and glucose-stimulated insulin secretion were evaluated. The rates of protein synthesis and degradation were determined in gastrocnemius muscle after 10 months of treatment. Insulin signalling, oxidative stress and cell death were analysed in vitro using C2C12 myotubes.

Results

After 6 and 10 months of treatment, these mice became glucose intolerant, and after 10 months, they exhibited marked insulin resistance. Reduced islet glucose-stimulated insulin secretion was observed after the 3rd month of treatment. Mice treated for 10 months showed significantly decreased body weight and increased muscle protein degradation. In addition, muscle chymotrypsin-like proteasomal activity and lysosomal cathepsin were markedly elevated. C2C12 myotubes exposed to increasing concentrations of pravastatin presented dose-dependent impairment of insulin-induced Akt phosphorylation, increased apoptotic markers (Bax protein and cleaved caspase-3) and augmented superoxide anion production.

Conclusions

In addition to reduced insulin secretion, long-term pravastatin treatment induces insulin resistance and muscle wasting. These results suggest that the diabetogenic effect of statins is linked to the appearance of myotoxicity induced by oxidative stress, impaired insulin signalling, proteolysis and apoptosis.

UHPLC-MS/MS assay for simultaneous determination of amlodipine, metoprolol, pravastatin, rosuvastatin, atorvastatin with its active metabolites in human plasma, for population-scale drug-drug interactions studies in people living with HIV

Thanks to highly active antiretroviral treatments, HIV infection is now considered as a chronic condition. Consequently, people living with HIV (PLWH) live longer and encounter more age-related chronic co-morbidities, notably cardiovascular diseases, leading to polypharmacy. As the management of drug-drug interactions (DDIs) constitutes a key aspect of the care of PLWH, the magnitude of pharmacokinetic DDIs between cardiovascular and anti-HIV drugs needs to be more thoroughly characterized. To that endeavour, an UHPLC-MS/MS bioanalytical method has been developed for the simultaneous determination in human plasma of amlodipine, metoprolol, pravastatin, rosuvastatin, atorvastatin and its active metabolites. Plasma samples were subjected to protein precipitation with methanol, followed by evaporation at room temperature under nitrogen of the supernatant, allowing to attain measurable plasma concentrations down to sub-nanogram per milliliter levels. Stable isotope-labelled analytes were used as internal standards. The five drugs and two metabolites were analyzed using a 6-min liquid chromatographic run coupled to electrospray triple quadrupole mass spectrometry detection. The method was validated over the clinically relevant concentrations ranging from 0.3 to 480 ng/mL for amlodipine, atorvastatin and p-OH-atorvastatin, and 0.4 to 480 ng/mL for pravastatin, 0.5 to 480 ng/mL for rosuvastatin and o-OH-atorvastatin, and 3 to 4800 ng/mL for metoprolol. Validation performances such as trueness (95.4-110.8%), repeatability (1.5-13.4%) and intermediate precision (3.6-14.5%) were in agreement with current international recommendations. Accuracy profiles (total error approach) were lying within the limits of ±30% accepted in bioanalysis. This rapid and robust UHPLC-MS/MS assay allows the simultaneous quantification in plasma of the major currently used cardiovascular drugs and offers an efficient analytical tool for clinical pharmacokinetics as well as DDIs studies.

Quantitative Prediction of Oral Bioavailability of a Lipophilic Antineoplastic Drug Bexarotene Administered in Lipidic Formulation Using a Combined In Vitro Lipolysis/Microsomal Metabolism Approach

For performance assessment of the lipid-based drug delivery systems (LBDDSs), in vitro lipolysis is commonly applied because traditional dissolution tests do not reflect the complicated in vivo micellar formation and solubilization processes. Much of previous research on in vitro lipolysis has mostly focused on rank-ordering formulations for their predicted performances. In this study, we have incorporated in vitro lipolysis with microsomal stability to quantitatively predict the oral bioavailability of a lipophilic antineoplastic drug bexarotene (BEX) administered in LBDDS. Two types of LBDDS were applied: lipid solution and lipid suspension. The predicted oral bioavailability values of BEX from linking in vitro lipolysis with microsomal stability for lipid solution and lipid suspension were 34.2 ± 1.6% and 36.2 ± 2.6%, respectively, whereas the in vivo oral bioavailability of BEX was tested as 31.5 ± 13.4% and 31.4 ± 5.2%, respectively. The predicted oral bioavailability corresponded well with the oral bioavailability for both formulations, demonstrating that the combination of in vitro lipolysis and microsomal stability can quantitatively predict oral bioavailability of BEX. In vivo intestinal lymphatic uptake was also assessed for the formulations and resulted in <1% of the dose, which confirmed that liver microsomal stability was necessary for correct prediction of the bioavailability.

Lipophilic activated ester prodrug approach for drug delivery to the intestinal lymphatic system

The intestinal lymphatic system plays an important role in the pathophysiology of multiple diseases including lymphomas, cancer metastasis, autoimmune diseases, and human immunodeficiency virus (HIV) infection. It is thus an important compartment for delivery of drugs in order to treat diseases associated with the lymphatic system. Lipophilic prodrug approaches have been used in the past to take advantage of the intestinal lymphatic transport processes to deliver drugs to the intestinal lymphatics. Most of the approaches previously adopted were based on very bulky prodrug moieties such as those mimicking triglycerides (TG). We now report a study in which a lipophilic prodrug approach was used to efficiently deliver bexarotene (BEX) and retinoic acid (RA) to the intestinal lymphatic system using activated ester prodrugs. A range of carboxylic ester prodrugs of BEX were designed and synthesised and all of the esters showed improved association with chylomicrons, which indicated an improved potential for delivery to the intestinal lymphatic system. The conversion rate of the prodrugs to BEX was the main determinant in delivery of BEX to the intestinal lymphatics, and activated ester prodrugs were prepared to enhance the conversion rate. As a result, an 4-(hydroxymethyl)-1,3-dioxol-2-one ester prodrug of BEX was able to increase the exposure of the mesenteric lymph nodes (MLNs) to BEX 17-fold compared to when BEX itself was administered. The activated ester prodrug approach was also applied to another drug, RA, where the exposure of the MLNs was increased 2.4-fold through the application of a similar cyclic activated prodrug. Synergism between BEX and RA was also demonstrated in vitro by cell growth inhibition assays using lymphoma cell lines. In conclusion, the activated ester prodrug approach results in efficient delivery of drugs to the intestinal lymphatic system, which could benefit patients affected by a large number of pathological conditions.

Simvastatin activates single skeletal RyR1 channels but exerts more complex regulation of the cardiac RyR2 isoform

BACKGROUND AND PURPOSE

Statins are amongst the most widely prescribed drugs for those at risk of cardiovascular disease, lowering cholesterol levels by inhibiting 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase. Although effective at preventing cardiovascular disease, statin use is associated with muscle weakness, myopathies and, occasionally, fatal rhabdomyolysis. As simvastatin, a commonly prescribed statin, promotes Ca2+ release from sarcoplasmic reticulum (SR) vesicles, we investigated if simvastatin directly activates skeletal (RyR1) and cardiac (RyR2) ryanodine receptors.

EXPERIMENTAL APPROACH

RyR1 and RyR2 single-channel behaviour was investigated after incorporation of sheep cardiac or mouse skeletal SR into planar phospholipid bilayers under voltage-clamp conditions. LC-MS was used to monitor the kinetics of interconversion of simvastatin between hydroxy-acid and lactone forms during these experiments. Cardiac and skeletal myocytes were permeabilised to examine simvastatin modulation of SR Ca2+ release.

KEY RESULTS

Hydroxy acid simvastatin (active at HMG-CoA reductase) significantly and reversibly increased RyR1 open probability (Po) and shifted the distribution of Ca2+ spark frequency towards higher values in skeletal fibres. In contrast, simvastatin reduced RyR2 Po and shifted the distribution of spark frequency towards lower values in ventricular cardiomyocytes. The lactone pro-drug form of simvastatin (inactive at HMG-CoA reductase) also activated RyR1, suggesting that the HMG-CoA inhibitor pharmacophore was not responsible for RyR1 activation.

CONCLUSION AND IMPLICATIONS

Simvastatin interacts with RyR1 to increase SR Ca2+ release and thus may contribute to its reported adverse effects on skeletal muscle. The ability of low concentrations of simvastatin to reduce RyR2 Po may also protect against Ca2+ -dependent arrhythmias and sudden cardiac death.

Clinical Evaluation of a Polyherbal Nutritional Supplement in Dyslipidemic Volunteers

Ten important plant parts routinely used in South Indian ethnic food preparation as spices and condiments were investigated for their potential antidyslipidemic properties. The aim of the study was to characterize the biochemical properties of the polyherbal formulation (nutritional supplement) and evaluate its use to control dyslipidemia in patients. Phytochemical evaluation, in vitro α-amylase inhibitory assay, and high performance thin layer chromatography (HPTLC) fingerprinting were carried out with alcoholic extracts of all 10 individual plants and with the nutritional supplement. Investigation in human volunteers was conducted to evaluate the effect on dyslipidemia as measured by serum lipid biomarkers. Sixty-five volunteers were recruited for this study. Biomarker values at baseline and at 6th visit (end of review, 8/9 months) were compared to assess the usefulness of the nutritional supplement in the normalization of lipid biomarkers. In the qualitative analysis of metabolites, the results revealed the presence of various bioactive primary and secondary metabolites that might be responsible for their medicinal attributes. In human volunteers, after supplement intake along with standard therapy, we observed significant decrease in serum cholesterol, triglyceride, low-density lipoprotein (LDL), and very low-density lipoprotein (VLDL) levels. High-density lipoprotein (HDL) level did not change in test patient volunteers. Reductions in hemoglobin A1C (HBA1C) and postprandial blood sugar levels were observed; the difference was not statistically significant. We believe that the polyherbal formulation of 10 medicinal plants has potent antidyslipidemic activity. Our results contribute for the first time toward documentation of augmented dyslipidemia control by use of the formulation.

The influences of SLCO1B1 and ABCB1 genotypes on the pharmacokinetics of simvastatin, in relation to CYP3A4 inhibition

AIM

To investigate the combined effects of SLCO1B1 and ABCB1 genotypes on the pharmacokinetics of simvastatin and its active metabolite simvastatin acid, in relation to CYP3A4 inhibition.

METHODS

We conducted a single-dose pharmacokinetic study of simvastatin in 26 healthy volunteers screened for their SLCO1B1 c.521T>C and ABCB1 c.1236C>T-2677G>T-3435C>T genotypes, with and without amlodipine pretreatment. The genetic effects and drug-interaction effect on simvastatin pharmacokinetic parameters were analyzed using a linear-mixed model.

RESULTS

The SLCO1B1 c.521T>C variant significantly increased exposure to simvastatin acid by around 40% (p < 0.05), similar to that caused by the amlodipine pretreatment. The ABCB1 gene showed no influence on exposure to simvastatin or simvastatin acid.

CONCLUSION

Only SLCO1B1, not ABCB1 genotype, is likely to be associated with simvastatin-induced myopathy. SLCO1B1 genotyping may be particularly beneficial in simvastatin users who are co-administered CYP3A4 inhibitors.

Quantitative analysis of lab-to-lab variability in Caco-2 permeability assays

In this study, Caco-2 permeability results from different laboratories were compared. Six different sets of apparent permeability coefficient (P_app) values reported in the literature were compared to experimental P_app obtained in our laboratory. The differences were assessed by determining the root mean square error (RMSE) values between the datasets, which reached levels as high as 0.581 for the training set compounds, i.e. ten compounds with known effective human permeability (P_eff). The consequences of these differences in P_app for prediction of oral drug absorption were demonstrated by introducing the P_app into the absorption and pharmacokinetics simulation software application GastroPlus™ for prediction of the fraction absorbed (F_a) in humans using calibrated "user-defined permeability models". The RMSE were calculated to assess the differences between the simulated F_a and experimental values reported in the literature. The RMSE for F_a simulated with the permeability model calibrated using experimental P_app from our laboratory was 0.128. When the calibration was performed using P_app from literature datasets, the RMSE values for F_a were higher in all cases except one. This study shows quantitative lab-to-lab variability of Caco-2 permeability results and the potential consequences this can have in the use of these results for predicting intestinal absorption of drugs.