Metabolic myopathies discovered during investigations of statin myopathy

Statins as anti-tumor agents: A paradigm for repurposed drugs

BACKGROUND

Statins, frequently prescribed medications, work by inhibiting the rate-limiting enzyme HMG-CoA reductase (HMGCR) in the mevalonate pathway to reduce cholesterol levels. Due to their multifaceted benefits, statins are being adapted for use as cost-efficient, safe and effective anti-cancer treatments. Several studies have shown that specific types of cancer are responsive to statin medications since they rely on the mevalonate pathway for their growth and survival.

RECENT FINDINGS

Statin are a class of drugs known for their potent inhibition of cholesterol production and are typically prescribed to treat high cholesterol levels. Nevertheless, there is growing interest in repurposing statins for the treatment of malignant neoplastic diseases, often in conjunction with chemotherapy and radiotherapy. The mechanism behind statin treatment includes targeting apoptosis through the BCL2 signaling pathway, regulating the cell cycle via the p53-YAP axis, and imparting epigenetic modulations by altering methylation patterns on CpG islands and histone acetylation by downregulating DNMTs and HDACs respectively. Notably, some studies have suggested a potential chemo-preventive effect, as decreased occurrence of tumor relapse and enhanced survival rate were reported in patients undergoing long-term statin therapy. However, the definitive endorsement of statin usage in cancer therapy hinges on population based clinical studies with larger patient cohorts and extended follow-up periods.

CONCLUSIONS

The potential of anti-cancer properties of statins seems to reach beyond their influence on cholesterol production. Further investigations are necessary to uncover their effects on cancer promoting signaling pathways. Given their distinct attributes, statins might emerge as promising contenders in the fight against tumorigenesis, as they appear to enhance the efficacy and address the limitations of conventional cancer treatments.

Association of SLCO1B1 and ABCB1 Genetic Variants with Atorvastatin-induced Myopathy in Patients with Acute Ischemic Stroke

BACKGROUND

Certain patients experience muscle-related adverse effects after taking atorvastatin. Genetic factors play an important role in the occurrence of statin-induced myopathy.

AIM

We aimed to identify genetic variants associated with statin-induced myotoxicity.

METHODS

We prospectively enrolled 1,102 acute ischemic stroke patients who underwent atorvastatin treatment for the first time after admission. Patients were separated into case and control groups after a follow-up of 3 months. We used a biochemical definition of myopathy consisting of serum creatine kinase values more than ten times the upper limit of normal for the reference laboratory (150 U/L). Fifty single nucleotide polymorphisms (SNPs) from seven genes of ABCB1, CoQ2, HTR3B, RYR2, CYP3A5, HTR7 and SLCO1B1 were selected and genotyped. The effects of genetic polymorphisms on myopathy were observed.

RESULTS

61 cases and 110 controls were recruited in the study. Compared with the controls, the cases had a significant higher mutant frequency of the allele A (ABCB1, rs2373588) (OR = 2.01, 95%CI = 1.10-3.67, P = 0.001) and a significant lower mutant frequency of the allele A (SLCO1B1, rs976754) (OR = 1.85, 95%CI = 1.12-3.03, P = 0.042). Genotypes or alleles of the other SNPs had no significant difference between the two groups (P > 0.05).

CONCLUSION

Our findings reveal that SLCO1B1 and ABCB1 genetic variants are associated with statin-induced myopathy. These are valuable biomarkers for the evaluation of atorvastatin safety.

Atherosclerosis and Coenzyme Q10

Atherosclerosis is the most common cause of cardiac deaths worldwide. Classically, atherosclerosis has been explained as a simple arterial lipid deposition with concomitant loss of vascular elasticity. Eventually, this condition can lead to consequent blood flow reduction through the affected vessel. However, numerous studies have demonstrated that more factors than lipid accumulation are involved in arterial damage at the cellular level, such as inflammation, autophagy impairment, mitochondrial dysfunction, and/or free-radical overproduction. In order to consider the correction of all of these pathological changes, new approaches in atherosclerosis treatment are necessary. Ubiquinone or coenzyme Q₁₀ is a multifunctional molecule that could theoretically revert most of the cellular alterations found in atherosclerosis, such as cholesterol biosynthesis dysregulation, impaired autophagy flux and mitochondrial dysfunction thanks to its redox and signaling properties. In this review, we will show the latest advances in the knowledge of the relationships between coenzyme Q₁₀ and atherosclerosis. In addition, as atherosclerosis phenotype is closely related to aging, it is reasonable to believe that coenzyme Q₁₀ supplementation could be beneficial for both conditions.

Novel Phenotypes and Cardiac Involvement Associated With DNA2 Genetic Variants

Objectives: To report two novel DNA2 gene mutations causing early onset myopathy with cardiac involvement and late onset mitochondriopathy with rhabdomyolysis.

Methods: We performed detailed clinical, muscle histopathology and molecular studies including mitochondrial gene NGS analysis in two patients (Patient 1 and 2), a mother and her son, belonging to a Mexican family, and a third sporadic French patient.

Results: Patient 1 and 2 presented with an early onset myopathy associated with ptosis, velopharyngeal weakness, and cardiac involvement. Patient 3 presented rhabdomyolysis unmasking a mitochondrial disease characterized by a sensorineural hearing loss, ptosis, and lipomas. Muscle biopsies performed in all patients showed variable mitochondrial alterations. Patient 3 had multiple mtDNA deletion in his muscle. Genetic studies revealed a novel heterozygous frameshift mutation in DNA2 gene (c.2346delT p.Phe782Leufs^*3) in P1 and P2, and a novel heterozygous missense mutation in DNA2 gene (c.578T>C p.Leu193Ser) in the P3.

Conclusions: To date only few AD cases presenting either missense or truncating DNA2 variants have been reported. None of them presented with a cardiac involvement or rhabdomyolysis. Here we enlarge the genetic and phenotypic spectrum of DNA2-related mitochondrial disorders.

Treatment Options for Statin-Associated Muscle Symptoms

BACKGROUND

About 4.6 million persons in Germany are now taking statins, i.e., drugs that inhibit the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A (HMGCoA) reductase. Statins lower the concentration of low-density lipoproteins (LDL) and thereby lessen the rate of cardiovascular events; the size of this effect depends on the extent of lowering of the LDL cholesterol concentration. Muscle symptoms are a clinically relevant side effect of statin treatment.

METHODS

This review is based on pertinent publications retrieved by a selective literature search, and on the current recommendations of the European Atherosclerosis Society.

RESULTS

At least 5% of patients taking statins have statin-associated muscle symptoms (SAMS). The etiology of SAMS is heterogeneous. SAMS may seriously impair quality of life and cause complications of variable severity, up to and including rhabdomyolysis (in about 1 in 100,000 cases). SAMS often lead to a reduction in the prescribed dose of the statin, while also negatively affecting drug adherence. More than 90% of patients with SAMS can keep on taking statins over the long term and gain the full clinical benefit of statin treatment after a switch to another type of statin or a readjustment of the dose or frequency of administration. If the LDL cholesterol concentration is not adequately lowered while the patient is taking a statin in the highest tolerable dose, combination therapy is indicated.

CONCLUSION

SAMS are important adverse effects of statin treatment because they lessen drug adherence. Patients with SAMS should undergo a thorough diagnostic evaluation followed by appropriate counseling. In most cases, statins can be continued, with appropriate adjustments, even in the aftermath of SAMS.

Management of asymptomatic carotid stenosis

With modern intensive medical therapy, the risk of ipsilateral stroke in patients with asymptomatic carotid stenosis (ACS) is below the risk of either carotid stenting or endarterectomy. Routine intervention for ACS is therefore not justified; approximately 90% of patients with ACS would be better off with intensive medical therapy. The few who could benefit can be identified by transcranial Doppler embolus detection or features of vulnerable plaque that can be imaged by 3-dimensional ultrasound, MRI or positron emission tomography/computed tomography; some of these methods are still in development.

Statin intolerance

PURPOSE OF REVIEW

Adherence to hydroxymethylglutaryl-CoA reductase reductase inhibitor (statin) therapy correlates with cardiovascular mortality. Muscle symptoms are the most significant side-effects of statin therapy. This review article summarizes the current concepts of the diagnosis and clinical work-up of patients with statin-associated muscle symptoms (SAMS).

RECENT FINDINGS

SAMS represent a major barrier to maintain long-term persistence to statin treatment. SAMS reduce the quality of life and rare complications may extend to rhabdomyolysis. The molecular pathology of SAMS is heterogeneous. After exclusion of other causes of muscle symptoms the main principle of treatment is re-exposure to very low dose of statin and slow uptitration until the maximally tolerated dose is established. Using this approach the vast majority of patients can be treated with statins long term. For patients with SAMS that are not at low-density lipoproteins (LDL) goal with their maximally tolerated dose of statin combination therapy with ezetimibe and proprotein convertase subtilisin/kexin-9 inhibitors are available.

SUMMARY

Time and care is needed to address SAMS because they impair drug adherence. For most patients it is possible to continue the statin therapy. However, combination therapy is wanted if the maximally tolerated statin dose is not sufficient to reach LDL targets.

Statin-associated muscle symptoms: impact on statin therapy-European Atherosclerosis Society Consensus Panel Statement on Assessment, Aetiology and Management

Statin-associated muscle symptoms (SAMS) are one of the principal reasons for statin non-adherence and/or discontinuation, contributing to adverse cardiovascular outcomes. This European Atherosclerosis Society (EAS) Consensus Panel overviews current understanding of the pathophysiology of statin-associated myopathy, and provides guidance for diagnosis and management of SAMS. Statin-associated myopathy, with significant elevation of serum creatine kinase (CK), is a rare but serious side effect of statins, affecting 1 per 1000 to 1 per 10 000 people on standard statin doses. Statin-associated muscle symptoms cover a broader range of clinical presentations, usually with normal or minimally elevated CK levels, with a prevalence of 7-29% in registries and observational studies. Preclinical studies show that statins decrease mitochondrial function, attenuate energy production, and alter muscle protein degradation, thereby providing a potential link between statins and muscle symptoms; controlled mechanistic and genetic studies in humans are necessary to further understanding. The Panel proposes to identify SAMS by symptoms typical of statin myalgia (i.e. muscle pain or aching) and their temporal association with discontinuation and response to repetitive statin re-challenge. In people with SAMS, the Panel recommends the use of a maximally tolerated statin dose combined with non-statin lipid-lowering therapies to attain recommended low-density lipoprotein cholesterol targets. The Panel recommends a structured work-up to identify individuals with clinically relevant SAMS generally to at least three different statins, so that they can be offered therapeutic regimens to satisfactorily address their cardiovascular risk. Further research into the underlying pathophysiological mechanisms may offer future therapeutic potential.

An assessment by the Statin Muscle Safety Task Force: 2014 update

The National Lipid Association's Muscle Safety Expert Panel was charged with the duty of examining the definitions for statin-associated muscle adverse events, development of a clinical index to assess myalgia, and the use of diagnostic neuromuscular studies to investigate muscle adverse events. We provide guidance as to when a patient should be considered for referral to neuromuscular specialists and indications for the performance of a skeletal muscle biopsy. Based on this review of evidence, we developed an algorithm for the evaluation and treatment of patients who may be intolerant to statins as the result of adverse muscle events. The panel was composed of clinical cardiologists, clinical lipidologists, an exercise physiologist, and a neuromuscular specialist.

Pharmacogenomics, lipid disorders, and treatment options

Statins form the backbone of lipid-lowering therapy in the prevention of cardiovascular disease. Numerous studies have evaluated the effect of genomics on the clinical efficacy and adverse effects of statins. Several gene variants that can be linked to either the pharmacokinetics or pharmacodynamics of statins have been identified as potentially important, although there are some discrepant findings among studies. Effect sizes are modest for lipid-lowering efficacy and perhaps somewhat larger for risk of myopathy, although results are inconsistent. Pharmacogenomics of nonstatin lipid-lowering agents have not been evaluated to the same extent, given their relatively limited use, although there are some promising candidate genes for further study. Finally, with several new classes of lipid-lowering therapies soon becoming available, there may be a potential application for pharmacogenomics to identify patients ideally suited to receive-or those who should avoid-specific medications.

Diagnosis and treatment of mitochondrial myopathies

Mitochondrial disorders are a heterogeneous group of disorders resulting from primary dysfunction of the respiratory chain. Muscle tissue is highly metabolically active, and therefore myopathy is a common element of the clinical presentation of these disorders, although this may be overshadowed by central neurological features. This review is aimed at a general medical and neurologist readership and provides a clinical approach to the recognition, investigation, and treatment of mitochondrial myopathies. Emphasis is placed on practical management considerations while including some recent updates in the field.

Diagnosis, prevention, and management of statin adverse effects and intolerance: proceedings of a Canadian Working Group Consensus Conference

While the proportion of patients with significant statin-associated adverse effects or intolerance is very low, the increasing use and broadening indications have led to a significant absolute number of such patients commonly referred to tertiary care facilities and specialists. This report provides a comprehensive overview of the evidence pertaining to a broad variety of statin-associated adverse effects followed by a consensus approach for the prevention, assessment, diagnosis, and management. The overview is intended both to provide clarification of the untoward effects of statins and to impart confidence in managing the most common issues in a fashion that avoids excessive ancillary testing and/or subspecialty referral except when truly necessary. The ultimate goal is to ensure that patients who warrant cardiovascular risk reduction can be treated optimally, safely, and confidently with statin medications or alternatives when warranted.

Stepwise approach to myopathy in systemic disease

Muscle diseases can constitute a large variety of both acquired and hereditary disorders. Myopathies in systemic disease results from several different disease processes including endocrine, inflammatory, paraneoplastic, infectious, drug- and toxin-induced, critical illness myopathy, metabolic, and myopathies with other systemic disorders. Patients with systemic myopathies often present acutely or sub acutely. On the other hand, familial myopathies or dystrophies generally present in a chronic fashion with exceptions of metabolic myopathies where symptoms on occasion can be precipitated acutely. Most of the inflammatory myopathies can have a chance association with malignant lesions; the incidence appears to be specifically increased only in patients with dermatomyositis. In dealing with myopathies associated with systemic illnesses, the focus will be on the acquired causes. Management is beyond the scope of this chapter. Prognosis is based upon the underlying cause and, most of the time, carries a good prognosis. In order to approach a patient with suspected myopathy from systemic disease, a stepwise approach is utilized.

Metabolic myopathies: update 2009

Metabolic myopathies are inborn errors of metabolism that result in impaired energy production due to defects in glycogen, lipid, mitochondrial, and possibly adenine nucleotide metabolism. Fatty acid oxidation defects (FAOD), glycogen storage disease, and mitochondrial myopathies represent the 3 main groups of disorders, and some consider myoadenylate deaminase (AMPD1 deficiency) to be a metabolic myopathy. Clinically, a variety of neuromuscular presentations are seen at different ages of life. Newborns and infants commonly present with hypotonia and multisystem involvement (liver and brain), whereas onset later in life usually presents with exercise intolerance with or without progressive muscle weakness and myoglobinuria. In general, the glycogen storage diseases result in high-intensity exercise intolerance, whereas the FAODs and the mitochondrial myopathies manifest predominately during endurance-type activity or under fasted or other metabolically stressful conditions. The clinical examination is often normal, and testing requires various combinations of exercise stress testing, serum creatine kinase activity and lactate concentration determination, urine organic acids, muscle biopsy, neuroimaging, and specific genetic testing for the diagnosis of a specific metabolic myopathy. Prenatal screening is available in many countries for several of the FAODs through liquid chromatography-tandem mass spectrometry. Early identification of these conditions with lifestyle measures, nutritional intervention, and cofactor treatment is important to prevent or delay the onset of muscle weakness and to avoid potential life-threatening complications such as rhabdomyolysis with resultant renal failure or hepatic failure. This article will review the key clinical features, diagnostic tests, and treatment recommendations for the more common metabolic myopathies, with an emphasis on mitochondrial myopathies.