Incubating isolated mouse EDL muscles with creatine improves force production and twitch kinetics in fatigue due to reduction in ionic strength

High-fat diet affects measures of skeletal muscle contractile performance in a temperature specific manner but does not influence regional thermal sensitivity

The present study examined if 20-weeks high-fat diet (HFD) consumption had a temperature specific effect on the contractile performance and regional thermal sensitivity of isolated mouse soleus (SOL) and diaphragm (DIA) muscle. Four-week-old female CD-1 mice were randomly selected to consume either a standard laboratory diet or a standard laboratory diet in conjunction with a HFD for 20-weeks. Peripheral SOL and core DIA were isolated from each animal and maximal isometric force and work loop power were assessed at 20⁰C, 28⁰C, 35⁰C and 40⁰C. Increasing temperature to 35⁰C resulted in greater isometric stress, lower activation and relaxation time and higher work loop power in both muscles. A further increase in temperature to 40⁰C did not affect isometric force but increased work loop power output of the SOL. Conversely, isometric force of the DIA was reduced and work loop power maintained when temperature was increased to 40⁰C. HFD consumption resulted in greater isometric force and absolute work loop power of the SOL and reduced isometric stress of the DIA, effects that were less apparent at lower temperatures. When the relationship between temperature and each measure of contractile function was examined by linear regression, there was no difference in slope between the control or HFD groups for either SOL or DIA. These results indicate that whilst contractile function initially increases with temperature, the temperature to elicit maximal performance is muscle and contractile mode-specific. Furthermore, HFD effects on contractile function are temperature specific, but HFD does not influence the relationship between temperature and performance.

Protective Effect of Angiotensin 1-7 on Sarcopenia Induced by Chronic Liver Disease in Mice

Sarcopenia associated with chronic liver disease (CLD) is one of the more common extrahepatic features in patients with these pathologies. Among the cellular alterations observed in the muscle tissue under CLD is the decline in the muscle strength and function, as well as the increased fatigue. Morphological changes, such as a decrease in the fiber diameter and transition in the fiber type, are also reported. At the molecular level, sarcopenia for CLD is characterized by: (i) a decrease in the sarcomeric protein, such as myosin heavy chain (MHC); (ii) an increase in the ubiquitin–proteasome system markers, such as atrogin-1/MAFbx1 and MuRF-1/TRIM63; (iii) an increase in autophagy markers, such as LC3II/LC3I ratio. Among the regulators of muscle mass is the renin-angiotensin system (RAS). The non-classical axis of RAS includes the Angiotensin 1–7 [Ang-(1-7)] peptide and its receptor Mas, which in skeletal muscle has anti-atrophic effect in models of muscle wasting induced by immobilization, lipopolysaccharide, myostatin or angiotensin II. In this paper, we evaluated the effect of Ang-(1-7) on the sarcopenia by CLD in a murine model induced by the 5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) hepatotoxin administered through diet. Our results show that Ang-(1-7) administration prevented the decline of the function and strength of muscle and increased the fatigue detected in the DDC-fed mice. Besides, we observed that the decreased fiber diameter and MHC levels, as well as the transition of fiber types, were all abolished by Ang-(1-7) in mice fed with DDC. Finally, Ang-(1-7) can decrease the atrogin-1 and MuRF-1 expression as well as the autophagy marker in mice treated with DDC. Together, our data support the protective role of Ang-(1-7) on the sarcopenia by CLD in mice.

Enhanced mitochondrial biogenesis is associated with the ameliorative action of creatine supplementation in rat soleus and cardiac muscles

The current study focused on the effect of creatine supplementation with/without exercise on the expression of genes controlling mitochondrial biogenesis in skeletal and cardiac muscles, as well as its safety profile on the liver and kidney. A total of 40 male Wister rats were included in the present study. Two unexercised groups: The control sedentary group and the sedentary creatine-treated group (n=10) were treated daily with oral creatine (0.5 g/kg per day). Two exercised groups performed swimming exercise training 5 days/week for a period of 5 weeks; The Exercise training group, and exercise training and creatine (0.5 g/kg per day) treated group. After sacrifice, blood samples, cardiac and soleus muscles were collected for assessment of mtDNA copy number, gene expression analysis and nuclear extraction for the assay of PGC-1α. The results of the current study demonstrated that, physical activity with short-term creatine supplementation increased all factors of mitochondrial biogenesis, an effect that is devoid of any kidney or liver adverse effects. Further studies are still required to explore the potential of creatine supplementation in ameliorating mitochondrial diseases, including epilepsy, skeletal and cardiac myopathies, hepatopathies and nephropathies.

The combined effect of creatine and resistance training on doxorubicin-induced muscle dysfunction

Background: Doxorubicin (DOX) is associated with profound skeletal muscle dysfunction. Resistance training (RT) and creatine (Cr) monohydrate have been independently shown to protect against DOX-induced muscle dysfunction. However, no investigation has examined their combined effects on DOX-induced muscle dysfunction. Methods: Male Sprague-Dawley rats were randomly assigned to a RT or sedentary group. After 6 wk of training, the soleus (SOL) and extensor digitorum longus (EDL) were excised and placed in a tissue bath containing Krebs buffer (K) or a K containing Cr (25 mM) for 30 min. The buffers were refreshed with new K or K containing DOX (24 μM) and incubated for 30 min. Muscles were then subjected to maximal twitch and fatigue testing.Results: DOX-induced fatigue occurred at 40 s in the SOL and EDL. RT delayed DOX-induced fatigue by 20 s in the SOL and 10 s in the EDL. Cr treatment delayed the onset of DOX-induced fatigue by 10 s in the EDL. The combination of RT and Cr delayed DOX-induced fatigue by 50 s in the SOL and 20 s in the EDL.Conclusion: This study showed that a combined treatment with RT and Cr minimized DOX-induced fatigue in the SOL and EDL.

Creatine Supplementation and Doxorubicin-Induced Skeletal Muscle Dysfunction: An Ex Vivo Investigation

Supplementing the diet with creatine (Cr) to manage chemotherapy-induced skeletal muscle weakness and fatigue has potential, but little has been done exploring it as an intervention. This study examined the effects of Cr on skeletal muscle dysfunction induced by the chemotherapy drug doxorubicin (Dox). Soleus and extensor digitorum longus (EDL) from male Sprague-Dawley rats maintained in an organ bath were incubated in Krebs-Henseleit (KH) buffer with or without creatine monohydrate (25 mM) for 30 min. Skeletal muscle was then incubated in KH buffer with or without Dox (24 μM) for an additional 30 min. Baths were then refreshed with KH buffer, and a 100-s fatigue protocol was administered. At baseline (0 s time point), no significant differences in force production were observed in the slow, type I soleus, but the Dox-treated soleus fatigued quicker than the non-Dox-treated soleus; however, pretreatment with Cr extended the time to fatigue in the Dox-treated soleus. In the fast, type II EDL, Dox treatment decreased force production at baseline and increased fatigue, and Cr treatment prior to Dox attenuated this dysfunction. Creatine pretreatment mitigated Dox-induced skeletal muscle dysfunction ex vivo suggesting that Cr may play a role in managing Dox-induced skeletal muscle side effects.

Potential involvement of dietary advanced glycation end products in impairment of skeletal muscle growth and muscle contractile function in mice

Diets enriched with advanced glycation end products (AGE) have recently been related to muscle dysfunction processes. However, it remains unclear whether long-term exposure to an AGE-enriched diet impacts physiological characteristics of skeletal muscles. Therefore, we explored the differences in skeletal muscle mass, contractile function and molecular responses between mice receiving a diet high in AGE (H-AGE) and low in AGE (L-AGE) for 16 weeks. There were no significant differences between L-AGE and H-AGE mice with regard to body weight, food intake or epididymal fat pad weight. However, extensor digitorum longus (EDL) and plantaris (PLA) muscle weights in H-AGE mice were lower compared with L-AGE mice. Higher levels of N ε -(carboxymethyl)-l-lysine, a marker for AGE, in EDL muscles of H-AGE mice were observed compared with L-AGE mice. H-AGE mice showed lower muscle strength and endurance in vivo and lower muscle force production of PLA muscle in vitro. mRNA expression levels of myogenic factors including myogenic factor 5 and myogenic differentiation in EDL muscle were lower in H-AGE mice compared with L-AGE mice. The phosphorylation status of 70-kDa ribosomal protein S6 kinase Thr389, an indicator of protein synthesis signalling, was lower in EDL muscle of H-AGE mice than that of L-AGE mice. These findings suggest that long-term exposure to an AGE-enriched diet impairs skeletal muscle growth and muscle contractile function, and that these muscle dysfunctions may be attributed to the inhibition of myogenic potential and protein synthesis.

Predicting muscle fatigue: a response surface approximation based on proper generalized decomposition technique

A novel technique is proposed to predict force reduction in skeletal muscle due to fatigue under the influence of electrical stimulus parameters and muscle physiological characteristics. Twelve New Zealand white rabbits were divided in four groups ([Formula: see text]) to obtain the active force evolution of in vitro Extensor Digitorum Longus muscles for an hour of repeated contractions under different electrical stimulation patterns. Left and right muscles were tested, and a total of 24 samples were used to construct a response surface based in the proper generalized decomposition. After the response surface development, one additional rabbit was used to check the predictive potential of the technique. This multidimensional surface takes into account not only the decay of the maximum repeated peak force, but also the shape evolution of each contraction, muscle weight, electrical input signal and stimulation protocol. This new approach of the fatigue simulation challenge allows to predict, inside the multispace surface generated, the muscle response considering other stimulation patterns, different tissue weight, etc.

Creatine supplementation does not alter neuromuscular recovery after eccentric exercise

INTRODUCTION

The purpose of this study was to investigate the effects of creatine (CR) supplementation on recovery after eccentric exercise (ECC).

METHODS

Fourteen men were assigned randomly to ingest 0.3 g/kg of CR or placebo (PL) before and during recovery (48 hours) from 6 sets of 8 repetitions of ECC. Maximal voluntary contraction (MVC), voluntary activation (VA), muscle thickness (MT), electromyography (EMG), contractile properties, and soreness were assessed.

RESULTS

MVC, evoked twitch torque, and rate of torque development decreased for both groups immediately after ECC and recovered at 48 hours. MT increased and remained elevated at 48 hours for both groups. Soreness increased similarly for both groups. EMG activation was higher for CR versus PL only at 48 hours. There were no group differences for torque, total work, or fatigue index during ECC.

CONCLUSIONS

CR supplementation before and during recovery from ECC had no effect on strength, voluntary activation, or indicators of muscle damage. Muscle Nerve 54: 487-495, 2016.

Creatine supplementation prevents acute strength loss induced by concurrent exercise

PURPOSE

To investigate the effect of creatine (CR) supplementation on the acute interference induced by aerobic exercise on subsequent maximum dynamic strength (1RM) and strength endurance (SE, total number of repetitions) performance.

METHODS

Thirty-two recreationally strength-trained men were submitted to a graded exercise test to determine maximal oxygen consumption (VO2max: 41.56 ± 5.24 ml kg(-1) min(-1)), anaerobic threshold velocity (ATv: 8.3 ± 1.18 km h(-1)), and baseline performance (control) on the 1RM and SE (4 × 80 % 1RM to failure) tests. After the control tests, participants were randomly assigned to either a CR (20 g day(-1) for 7 days followed by 5 g day(-1) throughout the study) or a placebo (PL-dextrose) group, and then completed 4 experimental sessions, consisting of a 5-km run on a treadmill either continuously (90 % ATv) or intermittently (1:1 min at vVO2max) followed by either a leg- or bench-press SE/1RM test.

RESULTS

CR was able to maintain the leg-press SE performance after the intermittent aerobic exercise when compared with C (p > 0.05). On the other hand, the PL group showed a significant decrease in leg-press SE (p ≤ 0.05). CR supplementation significantly increased bench-press SE after both aerobic exercise modes, while the bench-press SE was not affected by either mode of aerobic exercise in the PL group. Although small increases in 1RM were observed after either continuous (bench press and leg press) or intermittent (bench press) aerobic exercise in the CR group, they were within the range of variability of the measurement. The PL group only maintained their 1RM.

CONCLUSIONS

In conclusion, the acute interference effect on strength performance observed in concurrent exercise may be counteracted by CR supplementation.

Hypohomocysteinemia: a potentially treatable cause of peripheral neuropathology?

Perturbations of homocysteine metabolism are associated with increased risk for cardiovascular disease, stroke, dementia, and depression, among other major diseases. To assess the relationship between hypohomocysteinemia (HH) and idiopathic peripheral neuropathy (IPN), a retrospective review of 37,442 patients from a tertiary medical clinic was performed. Of patients with HH, 5.9% had IPN versus 0.6% of patients without IPN. Overall, 41% of patients with HH had IPN. These observations indicate that although HH is uncommon in the general population, there is a striking relationship between HH and the incidence of IPN. This article discusses the clinical ramifications of these findings.