Effects of HMG-CoA reductase inhibitors on skeletal muscles of rabbits

Understanding coenzyme Q

Coenzyme Q (CoQ), also known as ubiquinone, comprises a benzoquinone head group and a long isoprenoid side chain. It is thus extremely hydrophobic and resides in membranes. It is best known for its complex function as an electron transporter in the mitochondrial electron transport chain (ETC) but is also required for several other crucial cellular processes. In fact, CoQ appears to be central to the entire redox balance of the cell. Remarkably, its structure and therefore its properties have not changed from bacteria to vertebrates. In metazoans, it is synthesized in all cells and is found in most, and maybe all, biological membranes. CoQ is also known as a nutritional supplement, mostly because of its involvement with antioxidant defenses. However, whether there is any health benefit from oral consumption of CoQ is not well established. Here we review the function of CoQ as a redox-active molecule in the ETC and other enzymatic systems, its role as a prooxidant in reactive oxygen species generation, and its separate involvement in antioxidant mechanisms. We also review CoQ biosynthesis, which is particularly complex because of its extreme hydrophobicity, as well as the biological consequences of primary and secondary CoQ deficiency, including in human patients. Primary CoQ deficiency is a rare inborn condition due to mutation in CoQ biosynthetic genes. Secondary CoQ deficiency is much more common, as it accompanies a variety of pathological conditions, including mitochondrial disorders as well as aging. In this context, we discuss the importance, but also the great difficulty, of alleviating CoQ deficiency by CoQ supplementation.

Statin treatment reduces leucine turnover, but does not affect endogenous production of beta-hydroxy-beta-methylbutyrate (HMB)

BACKGROUND

Statins, or hydroxy-methyl-glutaryl coenzyme A (HMG-CoA) reductase inhibitors, are one of the most commonly prescribed medications for lowering cholesterol. Myopathic side-effects ranging from pain and soreness to critical rhabdomyolysis are commonly reported and often lead to discontinuation. The pathophysiological mechanism is, in general, ascribed to a downstream reduction of Coenzyme Q10 synthesis. HMG-CoA is a metabolite of leucine and its corresponding keto acid α-ketoisocaproic acid (KIC) and β-hydroxy-β-methylbutyrate (HMB), however, little is known about the changes in the metabolism of leucine and its metabolites in response to statins.

OBJECTIVE

We aimed to investigate if statin treatment has implications on the upstream metabolism of leucine to KIC and HMB, as well as on other branched chain amino acids (BCAA).

DESIGN

12 hyperlipidemic older adults under statin treatment were recruited. The study was conducted as a paired prospective study. Included participants discontinued their statin treatment for 4 weeks before they returned for baseline measurements (before). Statin treatment was then reintroduced, and the participants returned for a second study day 7 days after reintroduction (after statin). On study days, participants were injected with stable isotope pulses for measurement of the whole-body production (WBP) of all BCAA (leucine, isoleucine and valine), along with their respective keto acids and HMB.

RESULTS

We found a reduced leucine WBP (22 %, p = 0.0033), along with a reduction in valine WBP (13 %, p = 0.0224). All other WBP of BCAA and keto acids were unchanged. There were no changes in the WBP of HMB.

CONCLUSIONS

Our study shows that statin inhibition of HMG-CoA reductase has an upstream impact on the turnover of leucine and valine. Whether this impairment in WBP of leucine may contribute to the known pathophysiological side effects of statins on muscle remains to be further investigated.

Zebrafish as a Model for the Study of Lipid-Lowering Drug-Induced Myopathies

Drug-induced myopathies are classified as acquired myopathies caused by exogenous factors. These pathological conditions develop in patients without muscle disease and are triggered by a variety of medicaments, including lipid-lowering drugs (LLDs) such as statins, fibrates, and ezetimibe. Here we summarise the current knowledge gained via studies conducted using various models, such as cell lines and mammalian models, and compare them with the results obtained in zebrafish (Danio rerio) studies. Zebrafish have proven to be an excellent research tool for studying dyslipidaemias as a model of these pathological conditions. This system enables in-vivo characterization of drug and gene candidates to further the understanding of disease aetiology and develop new therapeutic strategies. Our review also considers important environmental issues arising from the indiscriminate use of LLDs worldwide. The widespread use and importance of drugs such as statins and fibrates justify the need for the meticulous study of their mechanism of action and the side effects they cause.

Alleviation of Simvastatin-Induced Myopathy in Rats by the Standardized Extract of Ginkgo Biloba (EGb761): Insights into the Mechanisms of Action

Statins are the most widely prescribed cholesterol-lowering drugs to reduce the risk of cardiovascular diseases. Statin-induced myopathy is the major side effect of this class of drugs. Here, we studied whether standardized leaf extracts of ginkgo biloba (EGb761) would improve simvastatin (SIM)-induced muscle changes. Sixty Wistar rats were allotted into six groups: control group, vehicle group receiving 0.5% carboxymethyl cellulose (CMC) for 30 days, SIM group receiving 80 mg/kg/day SIM in 0.5% CMC orally for 30 days, SIM withdrawal group treated with SIM for 16 days and sacrificed 14 days later, and EGb761-100 and EGb761-200 groups posttreated with either 100 or 200 mg/kg/day EGb761 orally. Muscle performance on the rotarod, serum creatine kinase (CK), coenzyme Q10 (CoQ10), serum and muscle nitrite, muscle malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) activities were estimated. Additionally, muscle samples were processed for histopathological evaluation. We found that SIM decreased muscle performance on the rotarod, serum CoQ10, as well as muscle SOD and CAT activities while it increased serum CK, serum and muscle nitrite, as well as muscle MDA levels. SIM also induced sarcoplasmic vacuolation, splitting of myofibers, disorganization of sarcomeres, and disintegration of myofilaments. In contrast, posttreatment with EGb761 increased muscle performance, serum CoQ10, as well as muscle SOD and CAT activities while it reduced serum CK as well as serum and muscle nitrite levels in a dose-dependent manner. Additionally, EGb761 reversed SIM-induced histopathological changes with better results obtained by its higher dose. Interestingly, SIM withdrawal increased muscle performance on the rotarod, reduce serum CK and CoQ10, and reduced serum and muscle nitrite while it reversed SIM-induced histopathological changes. However, SIM withdrawal was not effective enough to restore their normal values. Additionally, SIM withdrawal did not improve SIM-induce muscle MDA, SOD, or CAT activities during the period studied. Our results suggest that EGb761 posttreatment reversed SIM-induces muscle changes possibly through its antioxidant effects, elevation of CoQ10 levels, and antagonizing mitochondrial damage.

Statins with different lipophilic indices exert distinct effects on skeletal, cardiac and vascular smooth muscle

AIMS

Data concerning the influence of statin lipophilicity on the myotoxic and pleiotropic effects of statins is conflicting, and mechanistic head-to-head comparison studies evaluating this parameter are limited. In order to address the disparity, this mechanistic investigation aimed to assess the effects of two short-acting statins with different lipophilic indices on skeletal, cardiac and vascular smooth muscle physiology.

MATERIALS AND METHODS

Young female Wistar rats were randomised to simvastatin (80 mg kg^-1 day^-1), pravastatin (160 mg kg^-1 day^-1) or control treatment groups. Changes in functional muscle performance were assessed, as well as mRNA levels of genes relating to atrophy, hypertrophy, mitochondrial function and/or oxidative stress.

KEY FINDINGS

There were no significant differences in the mRNA profiles of isolated skeletal muscles amongst the treatment groups. In terms of skeleletal muscle performance, simvastatin reduced functionality but treatment with pravastatin significantly improved force production. Rodents given simvastatin demonstrated comparable myocardial integrity to the control group. Conversely, pravastatin reduced left ventricular action potential duration, diastolic stiffness and Mhc-β expression. Pravastatin improved endothelium-dependent relaxation, particularly in muscular arteries, but this effect was absent in the simvastatin-treated rats. The responsiveness of isolated blood vessels to noradrenaline also differed between the statin groups. The findings of this study support that the effects of statins on skeletal, cardiac and vascular smooth muscle vary with their lipophilic indices.

SIGNIFICANCE

The results of this work have important implications for elucidating the mechanisms responsible for the myotoxic and pleiotropic effects of statins.

Statin-Associated Cardiomyopathy Responds to Statin Withdrawal and Administration of Coenzyme Q10

CONTEXT

Heart failure (HF) is rapidly increasing in incidence and is often present in patients receiving long-term statin therapy.

OBJECTIVE

To test whether or not patients with HF on long-term statin therapy respond to discontinuation of statin therapy and initiation of coenzyme Q10 (CoQ10) supplementation.

DESIGN

We prospectively identified patients receiving long-term statin therapy in whom HF developed in the absence of any identifiable cause. Treatment consisted of simultaneous statin therapy discontinuation and CoQ10 supplementation (average dosage = 300 mg/d).

MAIN OUTCOME MEASURES

Baseline and follow-up physical examination findings, symptom scores, echocardiograms, and plasma CoQ10 and cholesterol levels.

RESULTS

Of 142 identified patients with HF, 94% presented with preserved ejection fraction (EF) and 6% presented with reduced EF (< 50%). After a mean follow-up of 2.8 years, New York Heart Association class 1 increased from 8% to 79% (p < 0.0001). In patients with preserved EF, 34% had normalization of diastolic function and 25% showed improvement (p < 0.0001). In patients with reduced EF at baseline, the EF improved from a mean of 35% to 47% (p = 0.02). Statin-attributable symptoms including fatigue, muscle weakness, myalgias, memory loss, and peripheral neuropathy improved (p < 0.01). The 1-year mortality was 0%, and the 3-year mortality was 3%.

CONCLUSION

In patients receiving long-term statin therapy, statin-associated cardiomyopathy may develop that responds safely to statin treatment discontinuation and CoQ10 supplementation. Statin-associated cardiomyopathy may be a contributing factor to the current increasing prevalence of HF with preserved EF.

Local Application of Statins Significantly Reduced Hypertrophic Scarring in a Rabbit Ear Model

BACKGROUND

We previously showed that intradermal injection of statins is a successful treatment for hypertrophic scarring. Topical application has many advantages over intradermal injection. In this study, we demonstrate the efficacy of topical statin treatment in reducing scar in our validated rabbit ear scar model.

METHODS

Twenty New Zealand White rabbits were divided into 2 study groups, with 6 rabbits receiving 10 μm pravastatin intradermally at postoperative days 15, 18, and 21, and 14 rabbits receiving 0.4%, 2%, and 10% simvastatin topical application at postoperative days 14-25. Four or 6 full-thickness circular dermal punches 7 mm in diameter were made on the ventral surface of the ear down to but not including the perichondrium. Specimens were collected at 28 days to evaluate the effects of statins on hypertrophic scarring.

RESULTS

Treatment with pravastatin intradermal administration significantly reduced scarring in terms of scar elevation index. Topical treatment with both medium- and high-dose simvastatin also significantly reduced scarring. High-dose simvastatin topical treatment showed a major effect in scar reduction but induced side effects of scaling, erythema, and epidermal hyperplasia, which were improved with coapplication of cholesterol. There is a dose response in scar reduction with low-, medium- and high-dose simvastatin topical treatment. High-dose simvastatin treatment significantly reduced the messenger ribonucleic acid (mRNA) expression of connective tissue growth factor, consistent with our previously published work on intradermally injected statins. More directly, high-dose simvastatin treatment also significantly reduced the mRNA expression of collagen 1A1.

CONCLUSIONS

Topical simvastatin significantly reduces scar formation. The mechanism of efficacy for statin treatment through interference with connective tissue growth factor mRNA expression was confirmed.

Elucidation of the mechanism of atorvastatin-induced myopathy in a rat model

Myopathy is among the well documented and the most disturbing adverse effects of statins. The underlying mechanism is still unknown. Mitochondrial dysfunction related to coenzyme Q10 decline is one of the proposed theories. The present study aimed to investigate the mechanism of atorvastatin-induced myopathy in rats. In addition, the mechanism of the coenzyme Q10 protection was investigated with special focus of mitochondrial alterations. Sprague-Dawely rats were treated orally either with atorvastatin (100mg/kg) or atorvastatin and coenzyme Q10 (100mg/kg). Myopathy was assessed by measuring serum creatine kinase (CK) and myoglobin levels together with examination of necrosis in type IIB fiber muscles. Mitochondrial dysfunction was evaluated by measuring muscle lactate/pyruvate ratio, ATP level, pAkt as well as mitochondrial ultrastructure examination. Atorvastatin treatment resulted in a rise in both CK (2X) and myoglobin (6X) level with graded degrees of muscle necrosis. Biochemical determinations showed prominent increase in lactate/pyruvate ratio and a decline in both ATP (>80%) and pAkt (>50%) levels. Ultrastructure examination showed mitochondrial swelling with disrupted organelle membrane. Co-treatment with coenzyme Q10 induced reduction in muscle necrosis as well as in CK and myoglobin levels. In addition, coenzyme Q10 improved all mitochondrial dysfunction parameters including mitochondrial swelling and disruption. These results presented a model for atorvastatin-induced myopathy in rats and proved that mitochondrial dysfunction is the main contributor in statin-myopathy pathophysiology.

Resection of hepatocellular carcinoma in elderly patients and the role of energy balance

INTRODUCTION

Progressive functional impairment with age has a significant impact on perioperative risk management. Chronic liver diseases induce a strong oxidative stress; in the elderly, in particular, impaired elimination of free radicals leads to insufficient DNA repair. The events associated with a weak response to growth factors after hepatectomy leads to a decline in liver regeneration. Hypercholesterolemia is highly prevalent in the elderly, which may alter the coenzyme Q10 (CoQ) levels and in turn the cellular energy balance. This condition is commonly treated with statins. The aim of this study is to investigate the role of preoperative cellular energy balance in predicting hepatocellular carcinoma (HCC) postresection outcomes.

MATERIALS AND METHODS

In a 5-year period (2009-2013), elderly patients with hypercholesterolemia, cardiovascular disease, and diabetes mellitus, undergoing HCC resection, were recruited and grouped by age (<75 and ≥ 75 years old). All patients were previously treated with statins. The risk factors associated with hospital morbidity/mortality and prolonged length of stay (LOS) were evaluated.

RESULTS

Forty-five elderly patients were recruited and grouped according to their treatment: Group 1 (n = 23) was treated with statins alone (control group), whereas Group 2 (n = 22) was treated with statins and a CoQ analogue, 3 weeks from the surgery and at least a month later (experimental group). The majority of our patients were treated with atorvastatin [n = 28 (53.84%)] and the minority with simvastatin [n = 17 (32.69%)], 20 mg/day, for at least 3 years before the surgery. Perioperative mortality was observed in one patient of Group 1 (4.3%). Morbidities were noted in 13 patients of Group 1 (56.5%) and four patients of Group 2 (18.2%). The control group showed delayed functional recovery, muscle weakness, increased infection rate, and pleural effusion due to prolonged bed rest (hospital stay 13 days (7-19) vs. 8.5 days (5-12)), compared with the experimental group. The overall survival at 5 years was similar for both groups (n = 10 patients (43%) in Group 1 vs. n = 10 patients (45%) in Group 2).

CONCLUSION

In the elderly population, survival is closely linked to postoperative morbidity and mortality. In our study, prolonged LOS was found to be related to delayed bioenergetic recovery. When limited, risk factors such as infections, neutropenia, and red blood cell transfusions could lower LOS and mortality of elderly patients with HCC. Higher age was associated with greater postoperative morbidity and successful hospital stay.

Molecular mechanisms of statin intolerance

Statins reduce cardiovascular morbidity and mortality in primary and secondary prevention. Despite their efficacy, many persons are unable to tolerate statins due to adverse events such as hepatotoxicity and myalgia/myopathy. In the case of most patients, it seems that mild-to-moderate abnormalities in liver and muscle enzymes are not serious adverse effects and do not outweigh the benefits of coronary heart disease risk reduction. The risk for mortality or permanent organ damage ascribed to statin use is very small and limited to cases of myopathy and rhabdomyolysis. Statin-induced muscle-related adverse events comprise a highly heterogeneous clinical disorder with numerous, complex etiologies and a variety of genetic backgrounds. Every patient who presents with statin-related side effects cannot undergo the type of exhaustive molecular characterization that would include all of these mechanisms. Frequently the only solution is to either discontinue statin therapy/reduce the dose or attempt intermittent dosing strategies at a low dose.

Programmed Cell Death Genes Are Linked to Elevated Creatine Kinase Levels in Unhealthy Male Nonagenarians

Declining health in the oldest-old takes an energy toll for the simple maintenance of body functions. The underlying mechanisms, however, differ in males and females. In females, the declines are explained by loss of muscle mass; but this is not the case in males, in whom they are associated with increased levels of circulating creatine kinase. This relationship raises the possibility that muscle damage rather than muscle loss is the cause of the increased energy demands of unhealthy aging in males. We have now examined factors that contribute to the increase in creatine kinase. Much of it (60%) can be explained by a history of cardiac problems and lower kidney function, while being mitigated by moderate physical activity, reinforcing the notion that tissue damage is a likely source. In a search for genetic risk factors associated with elevated creatine kinase, the Ku70 gene XRCC6 and the ceramide synthase gene LASS1 were investigated because of their roles in telomere length and longevity and healthy aging, respectively. Single nucleotide polymorphisms in these two genes were independently associated with creatine kinase levels. The XRCC6 variant was epistatic to one of the LASS1 variants but not to the other. These gene variants have potential regulatory activity. Ku70 is an inhibitor of the proapoptotic Bax, while the product of Lass1, ceramide, operates in both caspase-dependent and -independent pathways of programmed cell death, providing a potential cellular mechanism for the effects of these genes on tissue damage and circulating creatine kinase.

Statin therapy and plasma coenzyme Q10 concentrations--A systematic review and meta-analysis of placebo-controlled trials

Statin therapy may lower plasma coenzyme Q10 (CoQ10) concentrations, but the evidence as to the significance of this effect is unclear. We assessed the impact of statin therapy on plasma CoQ10 concentrations through the meta-analysis of available RCTs. The literature search included selected databases up to April 30, 2015. The meta-analysis was performed using either a fixed-effects or random-effect model according to I(2) statistic. Effect sizes were expressed as weighted mean difference (WMD) and 95% confidence interval (CI). The data from 8 placebo-controlled treatment arms suggested a significant reduction in plasma CoQ10 concentrations following treatment with statins (WMD: -0.44 μmol/L, 95%CI: -0.52, -0.37, p<0.001). The pooled effect size was robust and remained significant in the leave-one-out sensitivity analysis. Subgroup analysis suggested that the impact of statins on plasma CoQ10 concentrations is significant for all 4 types of statins studied i.e. atorvastatin (WMD: -0.41 μmol/L, 95%CI: -0.53, -0.29, p<0.001), simvastatin (WMD: -0.47 μmol/L, 95% CI: -0.61, -0.33, p<0.001), rosuvastatin (WMD: -0.49 μmol/L, 95%CI: -0.67, -0.31, p<0.001) and pravastatin (WMD: -0.43 μmol/L, 95%CI: -0.69, -0.16, p=0.001). Likewise, there was no differential effect of lipophilic (WMD: -0.43 μmol/L, 95%CI: -0.53, -0.34, p<0.001) and hydrophilic statins (WMD: -0.47 μmol/L, 95%CI: -0.62, -0.32, p<0.001). With respect to treatment duration, a significant effect was observed in both subsets of trials lasting <12 weeks (WMD: -0.51 μmol/L, 95%CI: -0.64, -0.39, p<0.001) and ≥12 weeks (WMD: -0.40 μmol/L, 95%CI: -0.50, -0.30, p<0.001). The meta-analysis showed a significant reduction in plasma CoQ10 concentrations following treatment with statins. Further well-designed trials are required to confirm our findings and elucidate their clinical relevance.

Translational insight into statin-induced muscle toxicity: from cell culture to clinical studies

Statins are lipid-lowering drugs used widely to prevent and treat cardiovascular and coronary heart diseases. These drugs are among the most commonly prescribed medicines intended for long-term use. In general, statins are well tolerated. However, muscular adverse effects appear to be the most common obstacle that limits their use, resulting in poor patient compliance or even drug discontinuation. In addition, rare but potentially fatal cases of rhabdomyolysis have been reported with the use of these drugs, especially in the presence of certain risk factors. Previous reports have investigated statin-induced myotoxicity in vivo and in vitro using a number of cell lines, muscle tissues, and laboratory animals, in addition to randomized clinical trials, observational studies, and case reports. None of them have compared directly results from laboratory investigations with clinical observations of statin-related muscular adverse effects. To the best of our knowledge this is the first review article that combines laboratory investigation with clinical aspects of statin-induced myotoxicity. By reviewing published literature of in vivo, in vitro, and clinically relevant studies of statin myotoxicity, we aim to translate this important drug-related problem to establish a clear picture of proposed mechanisms that explain the risk factors and describe the diagnostic approaches currently used for evaluating the degree of muscle damage induced by these agents. This review provides baseline novel translational insight that can be used to enhance the safety profile, to minimize the chance of progression of these adverse effects to more severe and potentially fatal rhabdomyolysis, and to improve the overall patient compliance and adherence to long-term statin therapy.

Red yeast rice and coenzyme Q10 as safe alternatives to surmount atorvastatin-induced myopathy in hyperlipidemic rats

Statins are the first line treatment for the management of hyperlipidemia. However, the primary adverse effect limiting their use is myopathy. This study examines the efficacy and safety of red yeast rice (RYR), a source of natural statins, as compared with atorvastatin, which is the most widely used synthetic statin. Statin interference with the endogenous synthesis of coenzyme Q10 (CoQ10) prompted the hypothesis that its deficiency may be implicated in the pathogenesis of statin-associated myopathy. Hence, the effects of combination of CoQ10 with either statin have been evaluated. Rats were rendered hyperlipidemic through feeding them a high-fat diet for 90 days, during the last 30 days of the diet they were treated daily with either atorvastatin, RYR, CoQ10, or combined regimens. Lipid profile, liver function tests, and creatine kinase were monitored after 15 and 30 days of drug treatments. Heart contents of CoQ9 and CoQ10 were assessed and histopathological examination of the liver and aortic wall was performed. RYR and CoQ10 had the advantage over atorvastatin in that they lower cholesterol without elevating creatine kinase, a hallmark of myopathy. RYR maintained normal levels of heart ubiquinones, which are essential components for energy production in muscles. In conclusion, RYR and CoQ10 may offer alternatives to overcome atorvastatin-associated myopathy.

Effects of Curcuma comosa on the expression of atherosclerosis-related cytokine genes in rabbits fed a high-cholesterol diet

AIM OF THE STUDY

Curcuma comosa has been known to have potential use in cardiovascular diseases, but its immunoregulatory role in atherosclerosis development and liver toxicity has not been well studied. We therefore investigated the effects of Curcuma comosa on the expression of atherosclerosis-related cytokine genes in rabbits fed a high-cholesterol diet.

MATERIALS AND METHODS

Twelve male New Zealand White rabbits were treated with 1.0% cholesterol for one month and were subsequently treated with 0.5% cholesterol either alone, or in combination with 5mg/kg/day of simvastatin or with 400mg/kg/day of Curcuma comosa powder for three months. The expression of IL-1, MCP-1, TNF-α, IL-10, and TGF-β in the isolated abdominal aorta and liver were determined by real-time RT-PCR. Liver toxicity was determined by hepatic enzyme activity.

RESULTS

Curcuma comosa significantly decreased the expression of pro-inflammatory cytokines, leading to a stronger reduction in IL-1, MCP-1, and TNF-α expression compared to that was suppressed by simvastatin treatment. However, neither Curcuma comosa nor simvastatin affected the expression of anti-inflammation cytokines. In the liver, Curcuma comosa insignificantly decreased the expression of pro-inflammatory cytokines and significantly increased the expression of the anti-inflammatory cytokine IL-10 without altering the activity of hepatic enzymes. In contrast, simvastatin significantly increased the MCP-1 and TNF-α expressions and serum ALT level, without affecting the expression of anti-inflammatory cytokines.

CONCLUSIONS

In this study, we demonstrated that Curcuma comosa exerts anti-inflammatory activity in the aorta and liver without causing liver toxicity, indicating that Curcuma comosa is a potential candidate as an alternative agent in cardiovascular disease therapy.

Coenzyme Q(10) and statin myalgia: what is the evidence?

Statins lower cholesterol by inhibiting 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme in the biosynthesis of cholesterol. However, severe adverse events, including myalgias and rhabdomyolysis, have been reported with statin treatment. Different mechanisms have been proposed to explain statin-induced myopathy, including reduction of mevalonate pathway products, induction of apoptosis, mitochondrial dysfunction, and genetic predisposition. A decrease in coenzyme Q(10) (CoQ), a product of the mevalonate pathway, could contribute to statin induced myopathy. This article reviews the clinical and biochemical features of statin-induced myopathy, the inter-relationship between statins and the concentration of CoQ in plasma and tissues, and whether there is a role for supplementation with CoQ to attenuate statin-induced myopathy.

Statin-induced myopathy in the rat: relationship between systemic exposure, muscle exposure and myopathy

Rare instances of myopathy are associated with all statins, but cerivastatin was withdrawn from clinical use due to a greater incidence of myopathy. The mechanism of statin-induced myopathy with respect to tissue disposition was investigated by measuring the systemic, hepatic, and skeletal muscle exposure of cerivastatin, rosuvastatin, and simvastatin in rats before and after muscle damage. The development of myopathy was not associated with the accumulation of statins in skeletal muscle. For each statin exposure was equivalent in muscles irrespective of their fibre-type sensitivity to myopathy. The low amount of each statin in skeletal muscle relative to the liver does not support a significant role for transporters in the disposition of statins in skeletal muscle. Finally, the concentration of cerivastatin necessary to cause necrosis in skeletal muscle was considerably lower than rosuvastatin or simvastatin, supporting the concept cerivastatin is intrinsically more myotoxic than other statins.

Hydrophobic but not hydrophilic statins enhance phagocytosis and decrease apoptosis of human peripheral blood cells in vitro

The engulfing ability of phagocyting cells is related to the fluidity of the cell membrane that in turn depends on its chemical composition. Changes in membranal lipid content may increase or decrease membranal fluidity with a subsequent enhanced or impaired phagocytosis, respectively. Statins are recognized as potent inhibitors of cholesterol synthesis and therefore, are successfully administered to patients with hypercholesterolemia. Since it is considered that cholesterol affects cell function via changes in membrane composition, the present study was designed to examine the in vitro effect of three hydrophobic statins--atorvastatin, lovastatin and simvastatin, and a hydrophilic one--pravastatin, on the engulfing capacity, phagocytic index and apoptosis of peripheral blood phagocytes from healthy volunteers. Peripheral white blood cells obtained from 20 healthy normocholesterolemic individuals were incubated for 2h with 10 and 50 microM of the four statins and phagocytosis of fluorescent latex particles was detected by flow cytometry. Apoptosis was examined using annexin V and propidium iodide staining. An increase in the percentage of phagocyting cells was observed after incubation with 50 microM of lovastatin and simvastatin. On the other hand, all three hydrophobic statins induced a dose-dependent increase in the phagocytic index. The hydrophilic pravastatin did not affect phagocytosis, phagocytic index and apoptosis. All three hydrophobic statins at 50 microM exerted a slight, but significant decrease of apoptosis. The results suggest that the effect of hydrophobic statins on the engulfing capacity of human peripheral blood phagocytes and apoptosis is dependent on their dosage and physiochemical properties. This observation is an additional contribution to the statins' pleiotropic effect.

The role of coenzyme Q10 in statin-associated myopathy: a systematic review

Statins (3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors) are currently the most effective medications for reducing low-density lipoprotein cholesterol concentrations. Although generally safe, they have been associated with a variety of myopathic complaints. Statins block production of farnesyl pyrophosphate, an intermediate in the synthesis of ubiquinone or coenzyme Q10 (CoQ10). This fact, plus the role of CoQ10 in mitochondrial energy production, has prompted the hypothesis that statin-induced CoQ10 deficiency is involved in the pathogenesis of statin myopathy. We identified English language articles relating statin treatment and CoQ10 levels via a PubMed search through August 2006. Abstracts were reviewed and articles addressing the relationship between statin treatment and CoQ10 levels were examined in detail. Statin treatment reduces circulating levels of CoQ10. The effect of statin therapy on intramuscular levels of CoQ10 is not clear, and data on intramuscular CoQ10 levels in symptomatic patients with statin-associated myopathy are scarce. Mitochondrial function may be impaired by statin therapy, and this effect may be exacerbated by exercise. Supplementation can raise the circulating levels of CoQ10, but data on the effect of CoQ10 supplementation on myopathic symptoms are scarce and contradictory. We conclude that there is insufficient evidence to prove the etiologic role of CoQ10 deficiency in statin-associated myopathy and that large, well-designed clinical trials are required to address this issue. The routine use of CoQ10 cannot be recommended in statin-treated patients. Nevertheless, there are no known risks to this supplement and there is some anecdotal and preliminary trial evidence of its effectiveness. Consequently, CoQ10 can be tested in patients requiring statin treatment, who develop statin myalgia, and who cannot be satisfactorily treated with other agents. Some patients may respond, if only via a placebo effect.

Coenzyme Q10 and statins: biochemical and clinical implications

Statins are drugs of known and undisputed efficacy in the treatment of hypercholesterolemia, usually well tolerated by most patients. In some cases treatment with statins produces skeletal muscle complaints, and/or mild serum CK elevation; the incidence of rhabdomyolysis is very low. As a result of the common biosynthetic pathway Coenzyme Q (ubiquinone) and dolichol levels are also affected, to a certain degree, by the treatment with these HMG-CoA reductase inhibitors. Plasma levels of CoQ10 are lowered in the course of statin treatment. This could be related to the fact that statins lower plasma LDL levels, and CoQ10 is mainly transported by LDL, but a decrease is also found in platelets and in lymphocytes of statin treated patients, therefore it could truly depend on inhibition of CoQ10 synthesis. There are also some indications that statin treatment affects muscle ubiquinone levels, although it is not yet clear to which extent this depends on some effect on mitochondrial biogenesis. Some papers indicate that CoQ10 depletion during statin therapy might be associated with subclinical cardiomyopathy and this situation is reversed upon CoQ10 treatment. We can reasonably hypothesize that in some conditions where other CoQ10 depleting situations exist treatment with statins may seriously impair plasma and possible tissue levels of coenzyme Q10. While waiting for a large scale clinical trial where patients treated with statins are also monitored for their CoQ10 status, with a group also being given CoQ10, physicians should be aware of this drug-nutrient interaction and be vigilant to the possibility that statin drugs may, in some cases, impair skeletal muscle and myocardial bioenergetics.

The use of simvastatin in rabbit posterolateral lumbar intertransverse process spine fusion

BACKGROUND CONTEXT

There has been recent enthusiasm regarding the potential positive effects of statins on bone. Statins vary in their ability to influence bone activity. Simvastatin has been shown in experimental models to stimulate bone acting growth factors and enhance bone formation.

PURPOSE

The potential efficacy of Simvastatin in enhancing spinal fusion was evaluated in a rabbit posterolateral intertransverse process fusion model.

STUDY DESIGN/SETTING

Posterior lumbar intertransverse process spinal fusion performed on New Zealand White rabbits. PATIENT/STUDY SAMPLE: 44 New Zealand White rabbits.

OUTCOME MEASURES

Spinal fusion as determined by manual palpation testing and fine detail radiography. Bone fusion mass volume and density as determined by CT scan imaging.

METHODS

Forty-four New Zealand White rabbits underwent posterolateral intertransverse process spine fusion using autogenous iliac crest bone graft. Simvastatin was administered orally in 20 animals and the serum lipid profile quantified in test and control animals. The animals were euthanized 9 weeks following index surgery and the lumbar spine was harvested. Spinal fusion was determined by manual palpation testing and fine detail radiography. The volume and density of the bone fusion mass was quantified by computed tomography.

RESULTS

Drug treatment for 9 weeks caused a reduction in serum lipid biochemical markers when compared with controls. The spinal fusion rate, as judged by manual palpation testing (13.0% control group, 16.6% Simvastatin group) and fine detail radiography, was not significantly different comparing treatment with control animals. Accordant with the assessment of spinal fusion, there was no statistically significant effect on the volume of the fusion mass (1,224.7+/-98.7 mm(3) in the control group and 1,075.9+/-66.3 mm(3) in the Simvastatin group), the density of bone in the lumbar spine or that in the formed fusion mass.

CONCLUSIONS

Systemic use of Simvastatin caused a reduction in lipid biochemical parameters in treated animals. Successful spinal fusion as judged by manual palpation testing and fine detail radiography was not significantly different in treated versus untreated animals. The bone volume density of the formed fusion mass was not significantly different in treated versus untreated animals. There did not appear to be a significant advantage or disadvantage to the use of Simvastatin rabbit posterolateral spinal fusion. The potential positive effects of statins on bone require further study.

Effect of pravastatin, simvastatin and atorvastatin on the phagocytic activity of mouse peritoneal macrophages

Since cholesterol and lipid content may affect cell membrane fluidity, we assumed that treatment of mice with lipid lowering statins would enhance the engulfing capacity of their macrophages. Four groups of animals were examined. Group I-treated with pravastatin, group II--with simvastatin--both drugs in a dosage of 40 mg/kg daily, 5 days/week for a total of 3 weeks. Mice in group III received atorvastatin 5 mg/kg for the same time period. Group IV--untreated animals serving as controls. The phagocytic capacity of the peritoneal macrophages was evaluated by their ability to engulf latex particles. In addition, the mitogen response of the peripheral blood mononuclear cells (PBMC) and splenocytes to Con A and PHA was examined. Compared to the controls, the percentage of phagocyting cells in pravastatin-treated mice was enhanced by 18%, with simvastatin--by 24% and in atorvastatin-treated animals by 8%. The three statins increased the phagocytic index by 79.5%, 88.8% and 62%, respectively. The mitogen response of splenocytes from mice treated with the three statins to Con A increased by 68%, 48% and by 40%, respectively. Compared with the controls the response to PHA was higher in animals treated with pravastatin (84%), simvastatin (73%) and atorvastatin (57%). The response of PBMC from statin-treated animals to both mitogens did not differ from that of the controls. The results suggest that statins, at least those hereby investigated, may exert a beneficial effect on the immune function of the macrophages.

Pharmacodynamic effects of high dose lovastatin in subjects with advanced malignancies

Lovastatin, an inhibitor of the rate-limiting enzyme in the cholesterol biosynthetic pathway, hydroxymethylglutaryl coenzyme A reductase, has shown interesting antiproliferative activities in cell culture and in animal models of cancer. The goal of the current study is to determine whether lovastatin bioactivity levels, in a range equivalent to those used in in vitro and preclinical studies, can be safely achieved in human subjects. Here we present the findings from a dose-escalating trial of lovastatin in subjects with advanced malignancies. Lovastatin was administered every 6 h for 96 h in 4-week cycles in doses ranging from 10 mg/m2 to 415 mg/m2. Peak plasma lovastatin bioactivity levels of 0.06-12.3 microM were achieved in a dose-independent manner. Cholesterol levels decreased during treatment and normalized during the rest period. A dose-limiting toxicity was not reached and there were no clinically significant increases in creatine phosphokinase or serum hepatic aminotransferases levels. No antitumor responses were observed. These results demonstrate that high doses of lovastatin, given every 4 h for 96 h, are well-tolerated and in select cases, bioactivity levels in the range necessary for antiproliferative activity were achieved.

The Effect of HMG-CoA Reductase Inhibitors on Coenzyme Q10

The HMG-CoA reductase inhibitors, also known as statins, have an enviable safety profile; however, myotoxicity and to a lesser extent hepatotoxicity have been noted in some patients following treatment. Statins target several tissues, depending upon their lipophilicity, where they competitively inhibit HMG-CoA reductase, the rate-limiting enzyme for mevalonic acid synthesis and subsequently cholesterol biosynthesis. HMG-CoA reductase is also the first committed rate-limiting step for the synthesis of a range of other compounds including steroid hormones and ubidecarenone (ubiquinone), otherwise known as coenzyme Q(10) (CoQ(10)). Recent interest has focused on the possible role CoQ(10) deficiency may have in the pathophysiology of the rare adverse effects of statin treatment. Currently, there is insufficient evidence from human studies to link statin therapy unequivocally to pathologically significantly decreased tissue CoQ(10) levels. Although statin treatment has been reported to lower plasma/serum CoQ(10) status, few human studies have assessed tissue CoQ(10) status. The plasma/serum CoQ(10) level is influenced by a number of physiological factors and, therefore, has limited value as a means of assessing intracellular CoQ(10) status. In those limited studies that have assessed the effect of statin treatment upon tissue CoQ(10) levels, none have shown evidence of a fall in CoQ(10) levels. This may reflect the doses of statins used, since many appear to have been used at doses below those recommended for their maximum therapeutic effects. Moreover, the poor bioavailability in those peripheral tissues tested may not reflect the effects the agents are having in liver and muscle, the tissues commonly affected in those patients who do not tolerate statins. This article reviews the biochemistry of CoQ(10), its role in cellular metabolism and the available evidence linking possible CoQ(10) deficiency to statin therapy.

Ultrastructure of mouse striated muscle fibers following pravastatin administration

To examine the effect of pravastatin administration on striated muscle ultrastructure, 10 BalbC mice were given pravastatin 40 mg/kg/day for 3 weeks. At the end of the study, blood was withdrawn for evaluation of the serum creatine phospho-kinase (CPK) level and the muscles of the hind legs, as well as the heart and liver of the animals were examined with a light and transmission electron microscope. After treatment with pravastatin the results showed a 101% increase in serum CPK level in comparison to untreated controls. Hematoxillin-eosin stained tissues of pravastatin treated mice did not show any abnormal findings. While the ultrastructure of the heart and liver of the treated animals appeared normal, the muscle fibers showed a marked alterations of the mitochondria, which were increased in size compared to those of the controls. The cristae were heavily damaged and even completely destructed, giving the mitochondria appearance of empty vacuoles. The findings are in favor of a specificity of pravastatin for striated muscles.

Statins lower plasma and lymphocyte ubiquinol/ubiquinone without affecting other antioxidants and PUFA

It has been shown that treating hypercholesterolemic patients (HPC) with statins leads to a decrease, at least in plasma, not only in cholesterol, but also in important non-sterol compounds such as ubiquinone (CoQ10), and possibly dolichols, that derive from the same biosynthetic pathway. Plasma CoQ10 decrease might result in impaired antioxidant protection, therefore leading to oxidative stress. In the present paper we investigated the levels in plasma, lymphocytes and erythrocytes, of ubiquinol and ubiquinone, other enzymatic and non-enzymatic lipophilic and hydrophilic antioxidants, polyunsaturated fatty acids of phosfolipids and cholesterol ester fractions, as well as unsaturated lipid and protein oxidation in 42 hypercholesterolemic patients treated for 3 months. The patients were treated with different doses of 3 different statins, i.e. atorvastatin 10 mg (n = 10) and 20 mg (n = 7), simvastatin, 10 mg (n = 5) and 20 mg (n = 10), and pravastatin, 20 mg (n = 5) and 40 mg (n = 5). Simvastatin, atorvastatin and pravastatin produced a dose dependent plasma depletion of total cholesterol (t-CH), LDL-C, CoQ10H2, and CoQ10, without affecting the CoQ10H2/CoQ10 ratio. The other lipophilic antioxidants (d-RRR-alpha-tocopherol-vit E-, gamma-tocopherol, vit A, lycopene, and beta-carotene), hydrophilic antioxidants (vit C and uric acid), as well as, TBA-RS and protein carbonyls were also unaffected. Similarly the erythrocyte concentrations of GSH and PUFA, and the activities of enzymatic antioxidants (Cu,Zn-SOD, GPx, and CAT) were not significantly different from those of the patients before therapy. In lymphocytes the reduction concerned CoQ10H2, CoQ10, and vit E; other parameters were not investigated. The observed decline of the levels of CoQ10H2 and CoQ10 in plasma and of CoQ10H2, CoQ10 and vit E in lymphocytes following a 3 month statin therapy might lead to a reduced antioxidant capacity of LDL and lymphocytes, and probably of tissues such as liver, that have an elevated HMG-CoA reductase enzymatic activity. However, this reduction did not appear to induce a significant oxidative stress in blood, since the levels of the other antioxidants, the pattern of PUFA as well as the oxidative damage to PUFA and proteins resulted unchanged. The concomitant administration of ubiquinone with statins, leading to its increase in plasma, lymphocytes and liver may cooperate in counteracting the adverse effects of statins, as already pointed out by various authors on the basis of human and animal studies.

The clinical use of HMG CoA-reductase inhibitors and the associated depletion of coenzyme Q10. A review of animal and human publications

The depletion of the essential nutrient CoQ10 by the increasingly popular cholesterol lowering drugs, HMG CoA reductase inhibitors (statins), has grown from a level of concern to one of alarm. With ever higher statin potencies and dosages, and with a steadily shrinking target LDL cholesterol, the prevalence and severity of CoQ10 deficiency is increasing noticeably. An estimated 36 million Americans are now candidates for statin drug therapy. Statin-induced CoQ10 depletion is well documented in animal and human studies with detrimental cardiac consequences in both animal models and human trials. This drug-induced nutrient deficiency is dose related and more notable in settings of pre-existing CoQ10 deficiency such as in the elderly and in heart failure. Statin-induced CoQ10 deficiency is completely preventable with supplemental CoQ10 with no adverse impact on the cholesterol lowering or anti-inflammatory properties of the statin drugs. We are currently in the midst of a congestive heart failure epidemic in the United States, the cause or causes of which are unclear. As physicians, it is our duty to be absolutely certain that we are not inadvertently doing harm to our patients by creating a wide-spread deficiency of a nutrient critically important for normal heart function.

Muscular side effects of statins

Lipid lowering has been shown to be effective in preventing primary and recurrent cardiovascular events and to save life. Statins almost exclusively used for this purpose meanwhile became one of the most widely prescribed families of drugs world-wide. Myopathies--mainly not well characterized--are the major group of side effects. We here review different types of clinical appearances, localizations, symptoms and the biochemical background. The data indicate that severe muscular side effects are rare. Patients and their doctors, however, easily overlook mild ones. Myopathic symptoms without any known biochemical correlate are not rare. No general guideline exists about exact diagnosis and differential diagnosis. Strict adherence to the measures of life-style change and performance of regular exercise can even further enhance significantly these side effects. Much more research should be directed onto the pathophysiological (genetic?) background to finally evaluate possible therapeutic consequences rather than simply to withdraw or change the respective statin.

The effect of pravastatin and atorvastatin on coenzyme Q10

BACKGROUND

Coenzyme Q10 (CoQ10) is an antioxidant and plays an important role in the synthesis of adenosine triphosphate. Studies suggest that 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors reduce CoQ10 levels; however, no studies have directly compared HMG-CoA reductase inhibitors in a randomized crossover fashion.

METHODS

Twelve healthy volunteers received either 20 mg pravastatin (P) or 10 mg atorvastatin (A) for 4 weeks in a randomized crossover fashion. There was a 4- to 8-week washout period between the 2 phases. CoQ10 levels and a lipid profile were obtained.

RESULTS

There was no difference in CoQ10 levels from baseline to post-drug therapy for either P or A (0.61 +/- 0.14 vs 0.62 +/- 0.2 microg/mL and 0.65 +/- 0.22 vs 0.6 +/- 0.12 microg/mL, respectively; P >.05). There was a significant difference in low-density lipoprotein (LDL) levels from baseline to post-drug therapy for both P and A (97 +/- 21 vs 66 +/- 19 mg/dL and 102 +/- 21 vs 52 +/- 14 mg/dL, respectively; P <.01). There was no significant correlation between LDL and CoQ10.

CONCLUSIONS

P and A did not decrease CoQ10 despite a significant decrease in LDL levels. These findings suggest that HMG-CoA reductase inhibitors do not significantly decrease the synthesis of circulating CoQ10 in healthy subjects. Routine supplementation of CoQ10 may not be necessary when HMG-CoA reductase inhibitor therapy is administered.

HMG-CoA reductase inhibitors and myotoxicity

The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors specifically inhibit HMG-CoA reductase in the liver, thereby inhibiting the biosynthesis of cholesterol. These drugs significantly reduce plasma cholesterol level and long term treatment reduces morbidity and mortality associated with coronary heart disease. The tolerability of these drugs during long term administration is an important issue. Adverse reactions involving skeletal muscle are not uncommon, and sometimes serious adverse reactions involving skeletal muscle such as myopathy and rhabdomyolysis may occur, requiring discontinuation of the drug. Occasionally, arthralgia, alone or in association with myalgia, has been reported. In this article we review scientific data provided via Medline, adverse drug reaction case reports from the Swedish Drug Information System (SWEDIS) and the World Health Organization's International Drug Information System (INTDIS) database, focusing on HMG-CoA reductase inhibitor-related musculoskeletal system events. Cytochrome P450 (CYP) 3A4 is the main isoenzyme involved in the metabolic transformation of HMG-CoA reductase inhibitors. Individuals with both low hepatic and low gastrointestinal tract levels of CYP3A4 expression may be at in increased risk of myotoxicity due to potentially higher HMG-CoA reductase inhibitor plasma concentrations. The reported incidence of myotoxic reactions in patients treated with this drug class varies from 1 to 7% and varies between different agents. The risk of these serious adverse reactions is dose-dependent and may increase when HMG-CoA reductase inhibitors are prescribed concomitantly with drugs that inhibit their metabolism, such as itraconazole, cyclosporin, erythromycin and nefazodone. Electrolyte disturbances, infections, major trauma, hypoxia as well as drugs of abuse may increase the risk of myotoxicity. It is important that the potentially serious adverse reactions are recognised and correctly diagnosed so that the HMG-CoA reductase inhibitor may at once be withdrawn to prevent further muscular damage.

Pravastatin restored the infarct size-limiting effect of ischemic preconditioning blunted by hypercholesterolemia in the rabbit model of myocardial infarction

OBJECTIVES

We tested to find out whether pravastatin restores the infarct size (IS)-limiting effect of ischemic preconditioning (IP) and if it has any effect on the IP-induced activation of adenosine producing enzyme ecto-5'-nucleotidase which plays a key role in the IP-induced cardioprotection.

BACKGROUND

The IS-limiting effect of IP is blunted by hypercholesterolemia. Recently, HMG-CoA reductase inhibitors are shown to have direct cytoprotective effects.

METHODS

Rabbits were fed with a normal or cholesterol (1%) added diet with or without pravastatin (5 mg/kg/day) treatment. Infarct size was measured after 30 min occlusion and 3 h reperfusion of circumflex coronary artery with or without the IP procedure (5 min occlusion and 10 min reperfusion). Additionally, ecto-5'-nucleotidase activities of ischemic and nonischemic myocardium were measured immediately after IP procedure.

RESULTS

This dose of pravastatin did not normalize the increased level of serum cholesterol. The IS-limiting effect of preceding IP (IS reduced from 36.7% to 9.6%, p < 0.001) was abolished by hypercholesterolemia (from 46.1% to 31.3%, p = NS) and restored by pravastatin treatment (from 35.2% to 9.4%, p < 0.001). Pravastatin treatment did not affect IS or the effect of IP under normocholesterolemia. The activation of ecto-5'-nucleotidase presented as the activity ratio of ischemic to nonischemic myocardium (3.1-fold in normocholesterolemia) was blunted by hypercholesterolemia (1.8-fold, p < 0.05) and restored by pravastatin treatment (2.9-fold).

CONCLUSIONS

Pravastatin, at the dose serum cholesterol was not normalized, restored the IS-limiting effect of IP and IP-induced ecto-5'-nucleotidase activation, which were both blunted by hypercholesterolemia. The activation of ecto-5'-nucleotidase may be worth further investigation as a possible mechanism for the hypercholesterolemia-induced retardation and pravastatin-mediated restoration of the cardioprotective effect of IP.

Comparative toxicity of high doses of vastatins currently used by clinicians, in CD-1 male mice fed with a hypercholesterolemic diet

The CD-1 male-mouse model was employed to evaluate comparatively the toxicity of four vastatins (VTS) currently used in clinical medicine: lovastatin (LVT), simvastatin (SVT), pravastatin (PVT) and fluvastatin (FVT). Each vastatin was used orally in doses of 500 mg/Kg body weight/day, in animals with a hypercholesterolemic diet (HD) 5 days, or with a control diet (CD) 30 days. The association of high doses of VTS + HD produced a significant increase in liver weight and liver weight to body weight ratio in animals with SVT and FVT. Cholesterol (Chol) and triacylglycerols (TAG) in the liver increased significantly with FVT but not with the other VTS; Chol increased and TAG decreased in serum very significantly with FVT and SVT. The serum aminotransferases increased quite significantly with FVT but not with other VTS. In the experiment with high doses of VTS + CD, the animals receiving SVT or FVT showed a moderate loss of body weight. Liver weight and liver weight to body weight ratios were similar among all groups. Liver Chol showed a significant decrease with all VTS. Serum Chol decreased moderately with LVT and FVT. TAG in serum and liver showed a moderate decrease with all VTS. The serum aminotransferases were not modified by any vastatin. Our results indicate that high doses of VTS in male mice with a hypercholesterolemic diet result in a decreasing toxicity as follows: FVT>SVT>LVT>PVT.

Muscle damage induced by experimental hypoglycemia

To determine organ damage due to hypoglycemia, we studied the effects of insulin dose and hypoglycemia duration on serum enzyme activity in rabbits. Thirty rabbits were randomly divided into five groups according to hypoglycemia duration and insulin dose: A2, hypoglycemia for 30 minutes with 2 U/kg insulin; A10, hypoglycemia for 30 minutes with 10 U/kg insulin; B2, hypoglycemia for 60 minutes with 2 U/kg insulin; B10, hypoglycemia for 60 minutes with 10 U/kg insulin; and C, no hypoglycemia with 10 U/kg insulin and 50% glucose. Insulin-induced hypoglycemia was reversed by intravenous injection of glucose. Alterations in serum enzyme activity and creatine kinase (CK) isoenzyme distribution were determined before and after insulin injection. Serum CK activity increased significantly in all hypoglycemic groups compared with preinjection values, and tended to remain high for 24 hours in both groups A10 and B10. Serum activity of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH) increased only in group B10. In addition, the level of band 4 of serum CK isoenzymes, which exists predominantly in skeletal muscle and myocardium, increased significantly in group B10. These results suggest that the increase in both serum enzyme and CK band 4 isoenzyme activities during hypoglycemia is primarily due to damage in muscle rather than liver, and that the hypoglycemia duration and insulin dosage may influence the extent of organ damage.

Metabolism and drug interactions of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors in transplant patients: are the statins mechanistically similar?

3-Hydroxy-3-methylglutaryl coenzyme A reductase (EC 1.1.1.88) inhibitors are the most effective drugs to lower cholesterol in transplant patients. However, immunosuppressants and several other drugs used after organ transplantation are cytochrome P4503A (CYP3A, EC 1.14.14.1) substrates. Pharmacokinetic interaction with some of the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, specifically lovastatin and simvastatin, leads to an increased incidence of muscle skeletal toxicity in transplant patients. It is our objective to review the role of drug metabolism and drug interactions of lovastatin, simvastatin, pravastatin, fluvastatin, atorvastatin, and cerivastatin. In the treatment of transplant patients, from a drug interaction perspective, pravastatin, which is not significantly metabolized by CYP enzymes, and fluvastatin, presumably a CYP2C9 substrate, compare favorably with the other statins for which the major metabolic pathways are catalyzed by CYP3A.

Myopathy induced by HMG-CoA reductase inhibitors in rabbits: a pathological, electrophysiological, and biochemical study

A combination of electrophysiological, pathological, and biochemical studies were performed in myopathy induced by 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors. Simvastatin (a lipophilic inhibitor) or pravastatin (a hydrophilic inhibitor) were administered by gavage to rabbits. In Group I (simvastatin-treated group, 50 mg/kg/day for 4 weeks), four rabbits showed muscle necrosis and high serum creatine kinase (CK) levels, and all six rabbits showed electrical myotonia. In Group II (pravastatin-treated group, 100 mg/kg/day for 4 weeks), no rabbit showed either condition. In Group III (pravastatin-treated group, 200 mg/kg/day for 3 weeks plus 300 mg/kg/day for 3 weeks), one rabbit showed muscle necrosis and high serum CK level and two rabbits showed electrical myotonia. The pathological findings were muscle fiber necrosis and degeneration with increased acid phosphatase activity by light microscopy, autophagic vacuoles and mitochondrial swelling, and disruption and hypercontraction of myofibrils by electron microscopy. Ubiquinone content decreased in skeletal muscle by 22 to 36% in Group I, by 18 to 52% in Group II, and by 49 to 72% in Group III. However, mitochondrial enzyme activities of respiratory chain were normal in all groups. These results indicate that myopathy was not induced by a secondary dysfunction of mitochondrial respiration due to low ubiquinone levels.

Pravastatin. A reappraisal of its pharmacological properties and clinical effectiveness in the management of coronary heart disease

Pravastatin is an HMG-CoA reductase inhibitor which lowers plasma cholesterol levels by inhibiting de novo cholesterol synthesis. Pravastatin produces consistent dose-dependent reductions in both total and low density lipoprotein (LDL)-cholesterol levels in patients with primary hypercholesterolaemia. Favourable changes in other parameters such as total triglyceride and high density lipoprotein (HDL)-cholesterol levels are generally modest. Combination therapy with other antihyperlipidaemic agents such as cholestyramine further enhances the efficacy of pravastatin in patients with severe dyslipidaemias. Available data suggest that pravastatin is effective in elderly patients and in patients with hypercholesterolaemia secondary to diabetes mellitus or renal disease. The benefit of cholesterol-lowering in terms of patient outcomes is currently an area of considerable interest. Recently completed regression studies (PLAC I, PLAC II, KAPS and REGRESS) show that pravastatin slows progression of atherosclerosis and lowers the incidence of coronary events in patients with mild to moderately severe hypercholesterolaemia and known coronary heart disease. Large scale primary (WOSCOPS) and secondary (CARE) prevention studies, moreover, demonstrate that pravastatin has beneficial effects on coronary morbidity and mortality. In WOSCOPS, all-cause mortality was reduced by 22%. Pravastatin is generally well tolerated by most patients (including the elderly), as evidenced by data from studies of up to 5 years in duration. As with other HMG-CoA reductase inhibitors, myopathy occurs rarely (< 0.1% of patients treated with pravastatin): approximately 1 to 2% of patients may present with raised serum levels of hepatic transaminases. Thus, with its favourable effects on cardiovascular morbidity/mortality and total mortality, pravastatin should be considered a first-line agent in patients with elevated cholesterol levels, multiple risk factors or coronary heart disease who are at high risk of cardiovascular morbidity.

Subchronic toxicity of atorvastatin, a hydroxymethylglutaryl-coenzyme A reductase inhibitor, in beagle dogs

The toxicity of atorvastatin (AT), an inhibitor of hydroxymethylglutaryl-coenzyme A reductase (HMG), was evaluated in beagle dogs. In 4 studies [2-wk rising dose (daily increasing doses for 1 wk; maintenance for 1 wk), 12-wk rising dose (daily dosing with weekly increases in dose), 2-wk toxicity (daily dosing for 2 wk; 3 dose levels), 13-wk toxicity (daily dosing for 13 wk; 3 dose levels)], dogs received up to 400 mg/kg orally. Doses of 180 mg/kg induced moribundity, necessitating euthanasia. Weight losses up to 26% were seen at doses > or = 150 mg/kg. Decreases in cholesterol levels were dose-related. Alanine and/or aspartate aminotransferase were increased at doses > or = 80 mg/kg; alkaline phosphatase was increased at doses > or = 150 mg/kg. Histopathologic findings were seen at > or = 150 mg/kg and included hepatocellular eosinophilia related to increased smooth endoplasmic reticulum and cholangiohepatitis and cholecystitis at 150 mg/kg in the 2-wk toxicity study; hepatocellular degeneration, centrilobular bridging, cholecystitis, hemorrhage in gallbladder and brain, demyelination of optic nerve, and skeletal muscle necrosis at > or = 280 mg/kg in the 12-wk rising dose study; and erosion and hemorrhage in large intestine, hepatocellular degeneration and necrosis, and inflammation and necrosis of gallbladder epithelium at 320 mg/kg in the 2-wk rising dose study. Doses up to 80 mg/kg for 13 wk did not induce histopathologic lesions in examined organs. AT effectively lowered serum cholesterol in normal lipidemic dogs. Toxicity at AT in dogs was similar to that with other inhibitors of HMG except that lenticular changes were not seen, significant hepatic, testicular, or neurological toxicity was associated only with high doses at AT, and skeletal muscle changes similar to those described in rats and rabbits were identified.

Plasma enzymic changes in insulin-induced hypoglycemia in experimental rabbits

In order to elucidate the effects of hypoglycemia on cardiac and skeletal muscle, plasma activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and creatine kinase (CK) were assessed in rabbits with hypoglycemia induced by i.v. injection of insulin. After hypoglycemia lasting for more than 30 min, the plasma levels of ALT, AST and LDH rose significantly in 4 out of 5 rabbits reaching a peak at 24 hr. The plasma activity of CK rose remarkably and reached a peak at 6 hr after insulin injection in all rabbits. These results suggest prolonged hypoglycemia may cause myocardial and/or skeletal muscle damage, which can be ascertained by measuring plasma activities of the related enzymes.