Decreased ubiquinone availability and impaired mitochondrial cytochrome oxidase activity associated with statin treatment

The Role of Mitochondria in Statin-Induced Myopathy

Statins represent the primary therapy for combatting hypercholesterolemia and reducing mortality from cardiovascular events. Despite their pleiotropic effects in lowering cholesterol synthesis, circulating cholesterol, as well as reducing the risk of other systemic diseases, statins have adverse events in a small, but significant, population of treated patients. The most prominent of these adverse effects is statin-induced myopathy, which lacks precise definition but is characterised by elevations in the muscle enzyme creatine kinase alongside musculoskeletal complaints, including pain, weakness and fatigue. The exact aetiology of statin-induced myopathy remains to be elucidated, although impaired mitochondrial function is thought to be an important underlying cause. This may result from or be the consequence of several factors including statin-induced inhibition of coenzyme Q10 (CoQ10) biosynthesis, impaired Ca2+ signalling and modified reactive oxygen species (ROS) generation. The purpose of this review article is to provide an update on the information available linking statin therapy with mitochondrial dysfunction and to outline any mechanistic insights, which may be beneficial in the future treatment of myopathic adverse events.

Odd- and even-numbered medium-chained fatty acids protect against glutathione depletion in very long-chain acyl-CoA dehydrogenase deficiency

Recent trials have reported the ability of triheptanoin to improve clinical outcomes for the severe symptoms associated with long-chain fatty acid oxidation disorders, including very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency. However, the milder myopathic symptoms are still challenging to treat satisfactorily. Myopathic pathogenesis is multifactorial, but oxidative stress is an important component. We have previously shown that metabolic stress increases the oxidative burden in VLCAD-deficient cell lines and can deplete the antioxidant glutathione (GSH). We investigated whether medium-chain fatty acids provide protection against GSH depletion during metabolic stress in VLCAD-deficient fibroblasts. To investigate the effect of differences in anaplerotic capacity, we included both even-(octanoate) and odd-numbered (heptanoate) medium-chain fatty acids. Overall, we show that modulation of the concentration of medium-chain fatty acids in culture media affects levels of GSH retained during metabolic stress in VLCAD-deficient cell lines but not in controls. Lowered glutamine concentration in the culture media during metabolic stress led to GSH depletion and decreased viability in VLCAD deficient cells, which could be rescued by both heptanoate and octanoate in a dose-dependent manner. Unlike GSH levels, the levels of total thiols increased after metabolic stress exposure, the size of this increase was not affected by differences in cell culture medium concentrations of glutamine, heptanoate or octanoate. Addition of a PPAR agonist further exacerbated stress-related GSH-depletion and viability loss, requiring higher concentrations of fatty acids to restore GSH levels and cell viability. Both odd- and even-numbered medium-chain fatty acids efficiently protect VLCADdeficient cells against metabolic stress-induced antioxidant depletion.

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.

Improvement of Platelet Respiration by Cell-Permeable Succinate in Diabetic Patients Treated with Statins

Diabetes mellitus (DM) is the most severe metabolic disease that reached the level of a global pandemic and is associated with high cardiovascular morbidity. Statins are the first-line lipid-lowering therapy in diabetic patients with or without a history of atherosclerotic disease. Although well tolerated, chronic treatment may result in side effects that lead to treatment interruption. Mitochondrial dysfunction has emerged as a central pathomechanism in DM- and statin-induced side effects. Assessment of mitochondrial respiration in peripheral platelets has been increasingly used as a mirror of organ mitochondrial dysfunction. The present study aimed to assess the: (i) changes in mitochondrial respiration elicited by statins in patients with type 2 DM and (ii) the effects of cell-permeable succinate (NV118) on respiratory parameters in platelets harvested from these patients. No significant changes were found in global mitochondrial respiration of intact platelets isolated from diabetic patients treated with either atorvastatin or rosuvastatin. Similarly, no significant changes in mitochondrial respiration of permeabilized platelets were found between diabetic patients treated with atorvastatin and healthy controls. Acute ex vivo administration of NV118 significantly improved respiration in isolated platelets. These results prompt further research on the role of permeable succinate as a therapeutic alternative for improving mitochondrial function in metabolic pathologies and point to the role of peripheral platelets as a potential biomarker of treatment response.

Bezafibrate activation of PPAR drives disturbances in mitochondrial redox bioenergetics and decreases the viability of cells from patients with VLCAD deficiency

Very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency is the most common inborn long-chain fatty acid oxidation (FAO) disorder. VLCAD deficiency is characterized by distinct phenotypes. The severe phenotypes are potentially life-threatening and affect the heart or liver, with a comparatively milder phenotype characterized by myopathic symptoms. There is an unmet clinical need for effective treatment options for the myopathic phenotype. The molecular mechanisms driving the gradual decrease in mitochondrial function and associated alterations of muscle fibers are unclear. The peroxisome proliferator-activated receptor (PPAR) pan-agonist bezafibrate is a potent modulator of FAO and multiple other mitochondrial functions and has been proposed as a potential medication for myopathic cases of long-chain FAO disorders. In vitro experiments have demonstrated the ability of bezafibrate to increase VLCAD expression and activity. However, the outcome of small-scale clinical trials has been controversial. We found VLCAD deficient patient fibroblasts to have an increased oxidative stress burden and deranged mitochondrial bioenergetic capacity, compared to controls. Applying heat stress under fasting conditions to bezafibrate pretreated patient cells, caused a marked further increase of mitochondrial superoxide levels. Patient cells failed to maintain levels of the essential thiol peptide antioxidant glutathione and experienced a decrease in cellular viability. Our findings indicate that chronic PPAR activation is a plausible initiator of long-term pathogenesis in VLCAD deficiency. Our findings further implicate disruption of redox homeostasis as a key pathogenic mechanism in VLCAD deficiency and support the notion that a deranged thiol metabolism might be an important pathogenic factor in VLCAD deficiency.

Cell-Permeable Succinate Rescues Mitochondrial Respiration in Cellular Models of Statin Toxicity

Statins are the cornerstone of lipid-lowering therapy. Although generally well tolerated, statin-associated muscle symptoms (SAMS) represent the main reason for treatment discontinuation. Mitochondrial dysfunction of complex I has been implicated in the pathophysiology of SAMS. The present study proposed to assess the concentration-dependent ex vivo effects of three statins on mitochondrial respiration in viable human platelets and to investigate whether a cell-permeable prodrug of succinate (complex II substrate) can compensate for statin-induced mitochondrial dysfunction. Mitochondrial respiration was assessed by high-resolution respirometry in human platelets, acutely exposed to statins in the presence/absence of the prodrug NV118. Statins concentration-dependently inhibited mitochondrial respiration in both intact and permeabilized cells. Further, statins caused an increase in non-ATP generating oxygen consumption (uncoupling), severely limiting the OXPHOS coupling efficiency, a measure of the ATP generating capacity. Cerivastatin (commercially withdrawn due to muscle toxicity) displayed a similar inhibitory capacity compared with the widely prescribed and tolerable atorvastatin, but did not elicit direct complex I inhibition. NV118 increased succinate-supported mitochondrial oxygen consumption in atorvastatin/cerivastatin-exposed platelets leading to normalization of coupled (ATP generating) respiration. The results acquired in isolated human platelets were validated in a limited set of experiments using atorvastatin in HepG2 cells, reinforcing the generalizability of the findings.

Effect of Statin Therapy on the Plasma Concentrations of Retinol, Alpha-Tocopherol and Coenzyme Q10 in Children with Familial Hypercholesterolemia

Purpose

Familial hypercholesterolemia (FH) requires early treatment. However, statins, which are regarded the first-line therapy, have an influence on redox balance. Antioxidant vitamins are important for many metabolic processes in the developing body. There are few data available on the long-term safety of statin use in children. The aim of this study was to evaluate the influence of statin treatment in children with FH on plasma concentrations of antioxidant vitamins: retinol, alpha-tocopherol and coenzyme Q10.

Methods

The first study group consisted of 13 children aged 10–18 years treated with simvastatin for at least 6 months, and the second group comprised 13 age- and sex-matched children with hypercholesterolemia, in whom pharmacological treatment had not been applied yet. Analyses were performed using a high-performance liquid chromatograph coupled with a MS detector.

Results

The analysis did not reveal significant differences in the concentration of retinol, alpha-tocopherol or coenzyme Q10 between the studied groups. The adjustment of the concentrations of the vitamins to the cholesterol level also indicated no significant differences. We found no deficits in antioxidant vitamins in patients treated with statins, or any risk of adverse effects associated with an increase in their concentration.

Conclusion

There is no rationale for additional supplementation using antioxidant vitamins or modification of low-fat and low-cholesterol diet in pediatric patients treated with statins.

Electronic supplementary material

The online version of this article (10.1007/s10557-020-07091-w) contains supplementary material, which is available to authorized users.

Coenzyme Q10 Assessment and the Establishment of a Neuronal Cell Model of CoQ10 Deficiency

Coenzyme Q₁₀ (CoQ₁₀) plays a key role as an electron carrier in the mitochondrial respiratory chain and as a cellular antioxidant molecule. A deficit in CoQ₁₀ status may contribute to disease pathophysiology by causing a failure mitochondrial energy metabolism as well as compromising cellular antioxidant capacity. This chapter outlines the analytical methods used for determining cellular CoQ₁₀ status using high-pressure liquid chromatography with ultraviolet (HPLC-UV) detection. In addition, we present a pharmacological procedure for establishing a human neuronal cell model of CoQ₁₀ deficiency, for use in research studies.

Chronic exposure to environmentally relevant levels of simvastatin disrupts zebrafish brain gene signaling involved in energy metabolism

Simvastatin (SIM), a hypocholesterolaemic drug belonging to the statins group, is a widely prescribed pharmaceutical for prevention of cardiovascular diseases. Several studies showed that lipophilic statins, as SIM, cross the blood-brain barrier and interfere with the energy metabolism of the central nervous system in humans and mammalian models. In fish and other aquatic organisms, the effects of SIM on the brain energy metabolism are unknown, particularly following exposure to low environmentally relevant concentrations. Therefore, the present study aimed at investigating the influence of SIM on gene signaling pathways involved in brain energy metabolism of adult zebrafish (Danio rerio) following chronic exposure (90 days) to environmentally relevant SIM concentrations ranging from 8 ng/L to 1000 ng/L. Real-time PCR was used to determine the transcript levels of several genes involved in different pathways of the brain energy metabolism (glut1b, gapdh, acadm, accα, fasn, idh3a, cox4i1, and cox5aa). The findings here reported integrated well with ecological and biochemical responses obtained in a parallel study. Data demonstrated that SIM modulates transcription of key genes involved in the mitochondrial electron transport chain, in glucose transport and metabolism, in fatty acid synthesis and β-oxidation. Further, SIM exposure led to a sex-dependent transcription profile for some of the studied genes. Overall, the present study demonstrated, for the first time, that SIM modulates gene regulation of key pathways involved in the energy metabolism in fish brain at environmentally relevant concentrations.

Evaluating Risk of Incident Diabetes Between Patients Who Used Lovastatin and Red Yeast Rice Prescriptions (LipoCol Forte): A Retrospective Cohort Study Based on a Real-World Database

OBJECTIVE

This study aimed to evaluate the risk of incident diabetes between people who used lovastatin and red yeast rice (RYR) prescriptions.

METHODS

A retrospective cohort study was performed to analyze the real-world database of Taiwan's National Health Insurance. We identified the RYR cohort, which included 34,504 persons age 20 years or older who began their use of a RYR prescription in 2010-2014. A comparison cohort of 34,504 adults beginning the use of lovastatin was selected from the same dataset, which was matched by age and sex. Both cohorts had no diabetes before the use of the medications. Events of incident diabetes in 2000-2015 were ascertained from medical claims. Adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) of incident diabetes associated with the use of RYR prescriptions were calculated.

RESULTS

The incidences of diabetes for the RYR cohort and the lovastatin cohort were 1.01 and 2.59 per 100 person-years, respectively (P < 0.0001). Compared with the lovastatin cohort, the adjusted HR of incident diabetes was 0.46 (95% CI 0.43-0.50) for people who used RYR prescriptions. The association between reduced incident diabetes and use of RYR prescriptions was significant in various subgroups. There was a dose-response relationship between RYR prescriptions and the reduced risk of incident diabetes.

CONCLUSION

We raised the possibility that people who used RYR prescriptions may have a lower risk of incident diabetes compared with the lovastatin cohort.

Mechanisms of statin-associated skeletal muscle-associated symptoms

Statins lower the serum low-density lipoprotein cholesterol and prevent cardiovascular events by inhibiting 3-hydroxy-3-methyl-glutaryl-CoA reductase. Although the safety of statins is documented, many patients ingesting statins may suffer from skeletal muscle-associated symptoms (SAMS). Importantly, SAMS are a common reason for stopping the treatment with statins. Statin-associated muscular symptoms include fatigue, weakness and pain, possibly accompanied by elevated serum creatine kinase activity. The most severe muscular adverse reaction is the potentially fatal rhabdomyolysis. The frequency of SAMS is variable but in up to 30% of the patients ingesting statins, depending on the population treated and the statin used. The mechanisms leading to SAMS are currently not completely clarified. Over the last 15 years, several research articles focused on statin-induced mitochondrial dysfunction as a reason for SAMS. Statins can impair the function of the mitochondrial respiratory chain, thereby reducing ATP and increasing ROS production. This can induce mitochondrial membrane permeability transition, release of cytochrome c into the cytosol and induce apoptosis. In parallel, statins inhibit activation of Akt, mainly due to reduced function of mTORC2, which may be related to mitochondrial dysfunction. Mitochondrial dysfunction by statins is also responsible for activation of AMPK, which is associated with impaired activation of mTORC1. Reduced activation of mTORC1 leads to increased skeletal muscle protein degradation, impaired protein synthesis and stimulation of apoptosis. In this paper, we discuss some of the different hypotheses how statins affect skeletal muscle in more detail, focusing particularly on those related to mitochondrial dysfunction and the impairment of the Akt/mTOR pathway.

Statins, Muscle Disease and Mitochondria

Cardiovascular disease (CVD) accounts for >17 million deaths globally every year, and this figure is predicted to rise to >23 million by 2030. Numerous studies have explored the relationship between cholesterol and CVD and there is now consensus that dyslipidaemia is a causal factor in the pathogenesis of atherosclerosis. Statins have become the cornerstone of the management of dyslipidaemia. Statins have proved to have a very good safety profile. The risk of adverse events is small compared to the benefits. Nevertheless, the potential risk of an adverse event occurring must be considered when prescribing and monitoring statin therapy to individual patients. Statin-associated muscle disease (SAMS) is by far the most studied and the most common reason for discontinuation of therapy. The reported incidence varies greatly, ranging between 5% and 29%. Milder disease is common and the more serious form, rhabdomyolysis is far rarer with an incidence of approximately 1 in 10,000. The pathophysiology of, and mechanisms leading to SAMS, are yet to be fully understood. Literature points towards statin-induced mitochondrial dysfunction as the most likely cause of SAMS. However, the exact processes leading to mitochondrial dysfunction are not yet fully understood. This paper details some of the different aetiological hypotheses put forward, focussing particularly on those related to mitochondrial dysfunction.

Novel recessive mutations in COQ4 cause severe infantile cardiomyopathy and encephalopathy associated with CoQ10 deficiency

Coenzyme Q₁₀ (CoQ₁₀) or ubiquinone is one of the two electron carriers in the mitochondrial respiratory chain which has an essential role in the process of oxidative phosphorylation. Defects in CoQ₁₀ synthesis are usually associated with the impaired function of CoQ₁₀-dependent complexes I, II and III. The recessively transmitted CoQ₁₀ deficiency has been associated with a number of phenotypically and genetically heterogeneous groups of disorders manifesting at variable age of onset. The infantile, multisystemic presentation is usually caused by mutations in genes directly involved in CoQ₁₀ biosynthesis. To date, mutations in COQ1 (PDSS1 and PDSS2), COQ2, COQ4, COQ6, COQ7, COQ8A/ADCK3, COQ8B/ADCK4, and COQ9 genes have been identified in patients with primary form of CoQ₁₀ deficiency. Here we report novel mutations in the COQ4 gene, which were identified in an infant with profound mitochondrial disease presenting with perinatal seizures, hypertrophic cardiomyopathy and severe muscle CoQ₁₀ deficiency.

The effects of 2 weeks of statin treatment on mitochondrial respiratory capacity in middle-aged males: the LIFESTAT study

BACKGROUND

Statins are used to lower cholesterol in plasma and are one of the most used drugs in the world. Many statin users experience muscle pain, but the mechanisms are unknown at the moment. Many studies have hypothesized that mitochondrial function could be involved in these side effects.

AIM

The aim of the study was to investigate mitochondrial function after 2 weeks of treatment with simvastatin (S; n = 10) or pravastatin (P; n = 10) in healthy middle-aged participants.

METHODS

Mitochondrial respiratory capacity and substrate sensitivity were measured in permeabilized muscle fibers by high-resolution respirometry. Mitochondrial content (citrate synthase (CS) activity), antioxidant content, as well as coenzyme Q₁₀ concentration (Q₁₀) were determined. Fasting plasma glucose and insulin concentrations were measured, and whole body maximal oxygen uptake (VO_2max) was determined.

RESULTS

No differences were seen in mitochondrial respiratory capacity although a tendency was observed for a reduction when complex IV respiration was analyzed in both S (229 (169; 289 (95% confidence interval)) vs. 179 (146; 211) pmol/s/mg, respectively; P = 0.062) and P (214 (143; 285) vs. 162 (104; 220) pmol/s/mg, respectively; P = 0.053) after treatment. A tendency (1.64 (1.28; 2.00) vs. 1.28 (0.99; 1.58) mM, respectively; P = 0.092) for an increased mitochondrial substrate sensitivity (complex I-linked substrate; glutamate) was seen only in S after treatment. No differences were seen in Q₁₀, CS activity, or antioxidant content after treatment. Fasting glucose and insulin as well as VO_2max were not changed after treatment.

CONCLUSION

Two weeks of statin (S or P) treatment have no major effect on mitochondrial function. The tendency for an increased mitochondrial substrate sensitivity after simvastatin treatment could be an early indication of the negative effects linked to statin treatment.

National trends in acute kidney injury requiring dialysis in England between 1998 and 2013

Acute kidney injury (AKI) severe enough to require dialysis is increasing and associated with high mortality, yet robust information about temporal epidemiology of AKI requiring dialysis in England is lacking. In this retrospective observational study of the Hospital Episode Statistics (HES) data set covering the entire English National Health Service, we identified all patients with a diagnosis of AKI requiring dialysis between 1998 and 2013. This incidence increased from 774 cases (15.9 per million people) in 1998-1999 to 11,164 cases (208.7 per million people) in 2012-2013. The unadjusted in-hospital case-fatality was 30.3% in 1998-2003 and 30.2% in 2003-2008, but significantly increased to 41.1% in 2008-2013. Compared with 2003-2008, the multivariable adjusted odds ratio for death was higher in 1998-2003 at 1.20 (95% CI: 1.10-1.30) and in 2008-2013 at 1.13 (1.07-1.18). Charlson comorbidity scores of more than five (odds ratio 2.35; 95% CI: 2.20-2.51) and emergency admissions (2.46 (2.32-2.61) had higher odds for death. The odds for death decreased in patients over 85 years from 4.83 (3.04-7.67) in 1998-2003 to 2.19 (1.99-2.41) in 2008-2013. AKI in secondary diagnosis and in other diagnoses codes had higher odds for death compared with AKI in primary diagnosis code in all three periods. Thus, the incidence of AKI requiring dialysis has increased progressively over 15 years in England. Improvement in case-fatality in 2003-2008 has not been sustained in the last 5 years.

Modulation of h(2)s metabolism by statins: a new aspect of cardiovascular pharmacology

SIGNIFICANCE

Statins (3-hydroxy-3-methylglutarylcoenzyme A reductase inhibitors) are commonly used in the treatment of cardiovascular diseases. Statins reduce plasma low-density lipoproteins, inhibit inflammatory reaction, improve endothelial function, ameliorate oxidative stress, and reduce platelet activity. Consequently, statins markedly decrease the risk of acute cardiovascular events. H(2)S is synthesized in all layers of the vascular wall, including the endothelium, smooth muscle cells, and perivascular adipose tissue (PVAT).

RECENT ADVANCES

Recent studies demonstrate that PVAT-derived H(2)S decreases vascular tone by activating K(ATP) and/or KCNQ potassium channels in smooth muscle cells. Lipophilic atorvastatin, but not hydrophilic pravastatin, increases net H(2)S production in PVAT by inhibiting its mitochondrial oxidation, and augments the anticontractile effect of PVAT. Inhibition of H(2)S metabolism results from atorvastatin-induced decrease in coenzyme Q, which is a cofactor of H(2)S oxidation by sulfide:quinone oxidoreductase. In contrast to H(2)S, statins do not impair mitochondrial oxidation of organic substrates.

CRITICAL ISSUES

Taking into account antiatherosclerotic and anti-inflammatory effect of H(2)S, the gas may mediate some of the beneficial effects of statins on the cardiovascular system. In addition, specific statins differ in their ability to enhance H(2)S signaling.

FUTURE DIRECTIONS

Since both statins and H(2)S reduce ischemia-reperfusion injury, the possible effect of statins on H(2)S oxidation in other tissues such as the heart and the kidney needs to be examined. Inhibition of H(2)S metabolism may be a new therapeutic strategy to improve H(2)S signaling, especially in the mitochondrial compartment.

Rosuvastatin lowers coenzyme Q10 levels, but not mitochondrial adenosine triphosphate synthesis, in children with familial hypercholesterolemia

OBJECTIVE

To investigate whether statin therapy affects coenzyme Q10 (CoQ10) status in children with heterozygous familial hypercholesterolemia (FH).

STUDY DESIGN

Samples were obtained at baseline (treatment naïve) and after dose titration with rosuvastatin, aiming for a low-density lipoprotein cholesterol level of 110 mg/dL. Twenty-nine patients were treated with 5, 10, or 20 mg of rosuvastatin for a mean period of 29 weeks.

RESULTS

We found a significant (32%) decrease in peripheral blood mononuclear cell (PBMC) CoQ10 level (P = .02), but no change in PBMC adenosine triphosphate synthesis (P = .60). Uncorrected plasma CoQ10 values were decreased significantly, by 45% (P < .01). In contrast, ratios of plasma CoQ10/total cholesterol and CoQ10/low-density lipoprotein cholesterol remained equal during treatment.

CONCLUSIONS

In children with FH, rosuvastatin causes a significant decrease in cellular PBMC CoQ10 status but does not affect mitochondrial adenosine triphosphate synthesis in children with FH. Further studies should address whether (rare) side effects of statin therapy could be explained by a deterioration in CoQ10 status.