Gayle A. Brazeau

Protective effect of estrogens against oxidative damage to heart and skeletal muscle in vivo and in vitro.

Estrogen has been shown to protect skeletal muscle from damage and to exert antioxidant properties. The purpose of the present study was to investigate the antioxidant and protective properties of estrogens in rodent cardiac and skeletal muscle and H9c2 cells. Female Sprague-Dawley rats were separated into three groups, ovariectomized (OVX), ovariectomized with estrogen replacement (OVX + E2), and intact control (SHAM), and were assessed at two time periods, 4 and 8 weeks. Rodents hearts were analyzed for basal and iron-stimulated lipid peroxidation in the absence and presence of beta-estradiol (betaE2) by measuring thiobarbituric acid reactive species (TBARS). Isolated soleus (SOL) and extensor digitorum longus (EDL) were analyzed for creatine kinase (CK) efflux. Using H9c2 cells, the in vitro effects of betaE2 and its isomer alpha-estradiol were investigated under glucose-free/hypoxic conditions. TBARS assay was also performed on the H9c2 in the presence or absence of betaE2. The results indicate that OVX rodent hearts are more susceptible to lipid peroxidation than OVX + E2 hearts. OVX soleus showed higher cumulative efflux of CK than OVX + E2. Furthermore, H9c2 survival during oxidative stress was enhanced when estrogen was present, and both OVX hearts at 4 weeks and H9c2 cells particularly were protected from oxidative damage by estrogens. We conclude that estrogen protects both skeletal and cardiac muscle from damage, and its antioxidant activity can contribute to this protection.

In vitro myotoxicity of selected cationic macromolecules used in non-viral gene delivery.

AbstractPurpose. Cationic lipid/DNA complexes have been proposed as a method of in vivo gene delivery via intravenous or intramuscular injection. A concern with using these polycationic molecules is whether they are associated with tissue toxicity at the injection site. Therefore, the objective of these studies was to investigate the myotoxic potential of selected non-viral gene delivery macromolecules (e.g., cationic lipids and polymers) with and without plasmid DNA (pDNA) in vitro. Methods. Myotoxicity was assessed by the cumulative release of creatine kinase (CK) over 90 minutes from the isolated rodent extensor digitorum longus muscle into a carbogenated balanced salt solution (BBS, pH 7.4, 37°C) following a 15 μL injection of the test formulation. Phenytoin (Dilantin®) and normal saline served as positive and negative controls, respectively. Results. The myotoxicity of plasmid DNA (pDNA, ~5000bp, 1 mg/ ml) was not statistically different from normal saline. However, the myotoxicity of Dilantin® was 16-times higher than either normal saline or pDNA (p < 0.05). Cationic liposomes were found to be less myotoxic than polylysine and PAMAM dendrimers. Polylysines myotoxicity was found to be dependent upon concentration and molecular weight. The myotoxicity of formulations of cationic liposomes(s), lower molecular weight polylysine (25,000) and higher concentration of PAMAM dendrimers with pDNA were found to be statistically less significant than those formulations without pDNA. Conclusions. The cationic liposomes were less myotoxic compared to the dendrimers and polylysine. Myotoxicity was dependent upon the type of cationic lipid macromolecule, concentration, molecular weight and the presence of pDNA. A possible explanation for this reduced tissue damage in cationic lipids complexed with pDNA is that the formation of complex reduces the overall positive charge of the injectable system resulting in less damage.

Pharmacokinetics of the Dietary Supplement Creatine

Creatine is a nonessential dietary component that, when supplemented in the diet, has shown physiological benefits in athletes, in animal-based models of disease and in patients with various muscle, neurological and neuromuscular disease. The clinical relevance of creatine supplementation is based primarily on its role in ATP generation, and cells may be able to better handle rapidly changing energy demands with supplementation.Although the pharmacological outcome measures of creatine have been investigated, the behaviour of creatine in the blood and muscle is still not fully understood. Creatine is most probably actively absorbed from the gastrointestinal tract in a similar way to amino acids and peptides. The distribution of creatine throughout the body is largely determined by the presence of creatine transporters. These transporters not only serve to distribute creatine but serve as a clearance mechanism because of creatine ‘trapping’ by skeletal muscle. Besides the pseudo-irreversible uptake by skeletal muscle, creatine clearance also depends on renal elimination and degradation to creatinine.Evidence suggests that creatine pharmacokinetics are nonlinear with respect to dose size and frequency. Skeletal muscle, the largest depot of creatine, has a finite capacity to store creatine. As such, when these stores are saturated, both volume of distribution and clearance can decrease, thus leading to complex pharmacokinetic situations. Additionally, other dietary components such as caffeine and carbohydrate can potentially affect pharmacokinetics by their influence on the creatine transporter. Disease and age may also affect the pharmacokinetics, but more information is needed.Overall, there are very limited pharmacokinetic data available for creatine, and further studies are needed to define absorption characteristics, clearance kinetics and the effect of multiple doses. Additionally, the relationship between plasma creatine and muscle creatine needs to be elucidated to optimise administration regimens.

Effects of ovariectomy and estrogen on skeletal muscle function in growing rats

This study examined the effect of estrogen replacement on soleus muscle size and contractile function in ovariectomized rats during physiological growth. Seven week old female Sprague–Dawley rats were assigned to one of three treatment groups:(1) control animals (SHAM), (2) ovariectomized animals without estrogen replacement (OVX/CO), and (3) ovariectomized animals with 17β-estradiol replacement (OVX/E2). OVX/CO and OVX/E2 animals were pair-fed to SHAM animals to rule out the potentially confounding effect of differences in food intake. Rats were sacrificed 4 weeks after surgery and the soleus muscle was removed for analysis. Estrogen replacement reduced body weight, relative body weight gain, and soleus muscle fiber size despite all groups having a similar food intake. Ovariectomy alone had no effect on any of these parameters suggesting that estrogen may inhibit skeletal muscle growth when it is the only ovarian hormone present. Neither ovariectomy nor estrogen replacement affected maximal specific isometric force. Estrogen replacement increased half relaxation time. Ovariectomy resulted in a reduction in time to peak tension that was reversed with estrogen replacement. This reduction was not accompanied by a change in myosin heavy chain composition implying that calcium handling may have been altered. Results from this study suggest that estrogen affects skeletal muscle growth and twitch kinetics.

Myotoxicity studies of injectable biodegradable in-situ forming drug delivery systems

The objective of the study was to investigate the potential in-vitro and in-vivo myotoxicity of different in-situ forming biodegradable drug delivery systems, namely in-situ Microparticle (ISM) systems and polymer solutions (in-situ implant systems). The acute myotoxicity was evaluated in-vitro using the isolated rodent skeletal muscle model by measuring the cumulative creatine kinase (CK) efflux. For the in-vivo study, following intramuscular injection (i.m.) into male Sprague Dawley rats, the area under the plasma CK-curve was used to evaluate muscle damage. The formulations included ISM-systems [a poly (lactide)-solvent phase dispersed into an external oil phase] and poly (lactide) solutions (in-situ implant systems). Phenytoin and normal saline served as positive and negative controls, respectively. Poly (lactide) in different solvents (in-situ implant systems) resulted in 14.4-24.3 times higher CK-values compared to normal saline, indicating a high myotoxic potential. With the ISM-system, the CK-release was significantly lower, decreased with a lower polymer phase: oil phase ratio, and approached the values of normal saline at a ratio of 1:4. Bupivacaine HCl- and Buserelin acetate- containing ISM-systems resulted in significantly lower CK-levels when compared to the corresponding drug formulation in normal saline. The in-vivo studies confirmed the in-vitro data and showed good muscle compatibility of the ISM-systems.

Effects of Methylphenidate on Fatigue and Depression: A Randomized, Double-Blind, Placebo-Controlled Trial

CONTEXT Fatigue is highly prevalent in populations with advanced illness and is often associated with depressed mood. The role of psychostimulant therapy in the treatment of these conditions remains ill defined. OBJECTIVES To evaluate the response of fatigue and depression in patients with advanced illness to titrated doses of methylphenidate (MP) as compared with placebo. METHODS In a randomized, double-blind, placebo-controlled trial, 30 hospice patients, both inpatients and outpatients, who had fatigue scores of at least four on a scale of zero to 10 (0=no fatigue and 10=worst fatigue), were randomly assigned to receive either 5mg of MP at 8 am and 1 pm or placebo. Doses of MP were titrated every three days according to response and adverse effects. Home care patients were monitored daily by telephone and visited by a research nurse on Study Days 0 (baseline), 3, 7, and 14. Fatigue was assessed using the Piper Fatigue Scale as the primary outcome measure and validated by the Visual Analogue Scale for Fatigue and the Edmonton Symptom Assessment Scale (ESAS) fatigue score. Subjects in inpatient facilities were interviewed or assessed by staff on an identical schedule. Depressive symptoms were assessed by the Beck Depression Inventory-II, Center for Epidemiologic Studies Depression Scale, and the ESAS depression score. Primary statistical analysis was conducted using repeated-measures multivariate analysis of the variance. RESULTS Both MP- and placebo-treated groups had similar measures of fatigue at baseline. Patients taking MP were found to have significantly lower fatigue scores (Piper Fatigue Scale, Visual Analogue Scale for Fatigue, and ESAS) at Day 14 compared with baseline. The improvement in fatigue with MP treatment was dose-dependent; the mean average effective dose was 10mg on Day 3 and 20mg on Day 14 (dose range of 10-40 mg). Placebo-treated individuals showed no significant improvement in fatigue. For patients with clinically significant depression on Day 0, treatment with MP was associated with a significant reduction in all test indices for depressed mood. For the placebo group, the changes in measures of depression were less than observed in the treatment group but were inconsistent between assessment tools. No significant toxicities were observed. CONCLUSION MP reduced symptoms of fatigue and depression when compared with placebo. The effect of MP on fatigue was dose-dependent and sustained over the duration of the study.

In Vitro and In Vivo Drug Release from a Novel In Situ Forming Drug Delivery System

PurposeThe objective of this work was to investigate the influence of various preparation and formulation parameters on the in vitro and in vivo release of bupivacaine hydrochloride from an injectable in situ forming microparticle system (ISM).MethodsThe in vitro drug release of ISM was investigated as a function of various formulation and process parameters and was compared to the drug release from in situ forming implants and conventional microparticles. In vivo studies were carried out in male Sprague–Dawley rats.ResultsUpon contact with an aqueous medium, the internal polymer phase of the ISM system solidified and formed microparticles. The initial drug release from ISM systems was reduced with decreasing polymer phase/external oil phase ratio. An advantage of the ISM system compared to in situ implant systems was the significantly reduced burst effect, resulting in drug release profiles comparable to microparticles prepared by conventional methods. The in vivo drug release studies were in good agreement with the in vitro drug release. With the ISM system, the analgesic effect of the bupivacaine hydrochloride was prolonged when compared to the injection of a drug solution or drug-polymer solution.ConclusionsISM are an attractive alternative for parenteral drug delivery systems.

Use of an in Vitro Model for the Assessment of Muscle Damage from Intramuscular Injections: in Vitro-in Vivo Correlation and Predictability with Mixed Solvent Systems

The potential of binary mixtures of propylene glycol–water, ethanol–water, and polyethylene glycol 400–water to cause skeletal muscle damage (myotoxicity) following intramuscular injection was examined with an in vitro model using the isolated rat muscle. At moderate concentrations (20–40%, v/v) of the organic cosolvent, the order of myotoxicity was propylene glycol > ethanol ≫ polyethylene glycol 400. The in vitro results were then compared with in vivo toxicity in rabbits after injection of normal saline, 40% (v/v) polyethylene glycol 400, 40% (v/v) propylene glycol, indocyanine green in normal saline, and indocyanine green in 40% (v/v) propylene glycol. Employing the area under the creatine kinase activity curve from 0 to 72 hr as the index of skeletal muscle damage, an excellent in vitro–in vivo correlation was observed. The basic myotoxicity relationships obtained from the binary cosolvent systems were then used to examine the myotoxicity of ternary organic cosolvent mixtures. Several mixed solvent systems with the same theoretical molar solubilization power for a model compound, diazepam, were selected to determine (1) if myotoxicity can be reduced by changing the composition of the ternary mixtures and (2) if myotoxicity of the individual components is additive. For the solvent systems containing propylene glycol, ethanol, and water, the total myotoxicity equaled the sum of the individual myotoxicity of each component. In contrast, for the solvent systems containing polyethylene glycol 400, the total myotoxicity was only half of the sum of individual toxicities. These results suggest that polyethylene glycol 400 in mixed cosolvent systems might have a protective effect on the myotoxicity generated by intramuscular injections.

In Situ Gel Formulations for Gene Delivery: Release and Myotoxicity Studies

The in vitro release of plasmid DNA and salmon sperm DNA from in situ gel formulations was investigated. Two in situ gel systems were studied: (a) an interpolymeric complex (IPC) of water-soluble polymers polymethacrylic acid (PMA) and polyethylene glycol (PEG) and (b) a hydroxypropylmethylcellulose–carbopol system (H:C). Two-way analysis of variance with replication demonstrated that both gel composition and medium pH influenced significantly the release of plasmid DNA from in situ gel formulations. When the release of both types of DNA was compared, higher release was observed for plasmid DNA compared to genomic salmon sperm DNA. Conformational analysis of the released plasmid DNA showed that DNA was released without degradation, but with remarkable conversion from supercoiled (SC) to open circular (OC). In addition, the tested in situ gel systems demonstrated protection from DNAse I degradation. The myotoxicity of the injectable gelling solutions was assessed by the cumulative release of creatine kinase (CK) over 120 min from the isolated rodent extensor digitorum longus (EDL) muscle. A higher level of cumulative CK was observed for IPC when compared to H:C (2:1). These results demonstrate that the in situ gelling systems can be considered as a valuable injectable controlled-delivery system for pDNA in their role to provide protection from DNAse degradation.

Single‐ and Multiple‐Dose Pharmacokinetics of Oral Creatine

Supplementation with exogenous creatine (Cr) has shown physiological benefits in humans, but little is known about the pharmacokinetics of Cr in humans. Six healthy males completed an open‐label study consisting of a full pharmacokinetic analysis following a single oral dose of Cr monohydrate (71 mg kg−1) and at steady‐state after 6 days of Cr administration (71 mg kg−1 qid). After the single oral dose, the clearance (CL/F) was 0.20 ± 0.066 L h−1 kg−1, tmax was 1.9 ± 0.88 hours, and Cmax = 102.1 ± 11.2 mg h L−1. At steady‐state, CL/F decreased to 0.12 ± 0.016 L h−1 kg−1, tmax did not change, and Cmax increased to 162.2 ± 30.0 mg L−1. Penetration (AUCMUSCLE/AUCPLASMA) of Cr into the interstitial muscle space, as determined by microdialysis, was 0.47 ± 0.09 and 0.37 ± 0.27 for the single dose and at steady‐state, respectively. Plasma and muscle data were simultaneously fitted with a model incorporating a saturable absorption and first‐order elimination process. In conclusion, repeated dosing of Cr caused a reduction in clearance that could result from saturation of the skeletal muscle pool of Cr.