Lack of Effects of Creatine on the Regeneration of Soleus Muscle after Injury in Rats

Beta-hydroxy-beta-methylbutyrate associated with low-intensity exercise training improves skeletal muscle regeneration through the IGF-Akt pathway

The effect of beta-hydroxy-beta-methylbutyrate (HMB) supplementation associated with exercise training at different intensities and frequencies on skeletal muscle regeneration of muscle-injured rats was investigated. Male Wistar rats were divided into sedentary and trained groups. The sedentary groups were subdivided into non-injured (SED-Ct), non-injured supplemented with HMB (SED-Ct-HMB), injured (SED), and injured with HMB (SED-HMB), and the trained groups were injured, supplemented with HMB, and then divided into training three times a week without load (HT3) or with load (HT3L) and training five times a week without load (HT5) and with load (HT5L). The rats received a daily dose of HMB associated with 60 min of swimming with or without 5% body mass load for 14 days. On the 15th day, cryoinjury was performed in the right tibialis anterior muscle (TA), and 48 h later, supplementation and training continued for 15 days. After the last session, the TA was dissected and a cross-sectional area (CSA) of muscle fibers was used to determine the percentage of CSA fibers and connective tissue (%CT), as well as the total and phosphorylated protein contents. SED-HMB showed increased CSA and decreased %CT and TGF-β when compared to SED. HT3 showed increased CSA and reduced %CT accompanied by increased IGF-1/Akt, myogenin, and MuRF1, and decreased TGF-β. The CSA of HT5L also increased, but at the cost of a higher %CT compared to the other groups. Our results demonstrated that HMB associated with training without load and with lower frequency per week may be a valuable strategy for skeletal muscle regeneration.

The Application of Creatine Supplementation in Medical Rehabilitation

Numerous health conditions affecting the musculoskeletal, cardiopulmonary, and nervous systems can result in physical dysfunction, impaired performance, muscle weakness, and disuse-induced atrophy. Due to its well-documented anabolic potential, creatine monohydrate has been investigated as a supplemental agent to mitigate the loss of muscle mass and function in a variety of acute and chronic conditions. A review of the literature was conducted to assess the current state of knowledge regarding the effects of creatine supplementation on rehabilitation from immobilization and injury, neurodegenerative diseases, cardiopulmonary disease, and other muscular disorders. Several of the findings are encouraging, showcasing creatine's potential efficacy as a supplemental agent via preservation of muscle mass, strength, and physical function; however, the results are not consistent. For multiple diseases, only a few creatine studies with small sample sizes have been published, making it difficult to draw definitive conclusions. Rationale for discordant findings is further complicated by differences in disease pathologies, intervention protocols, creatine dosing and duration, and patient population. While creatine supplementation demonstrates promise as a therapeutic aid, more research is needed to fill gaps in knowledge within medical rehabilitation.

Needling on trigger point promotes muscle regeneration after bupivacaine injection induced injury

Dry needling treatment has a promising relieving effect on Myofascial Pain Syndrome (MPS). In China, acupuncture practitioners use acupuncture needle instead to insert the "A-Shi" acupoint to treat MPS which is defined as the same as the trigger point of dry needling. This method has been applied for thousands of years in China. In this study, bupivacaine injection induced gastrocnemius muscle injury in mice. We applied the clinical improved needling method on animal model by making the angle between the skin and needle less than 30 degree. Animals got needling treatment 24 h later at the point where the bupivacaine was injected. Results of muscle H.E. staining showed that, compared to bupivacaine injection group without needling, acupuncture treatment group showed more intact muscle fibers, less inflammatory cell infiltration and fractured muscle fibers. By RNA sequencing analysis, our work firstly demonstrated that the physical stimulation of needling changed the gene expression of muscle tissue to accelerate the muscular regeneration process. Therefore, our study proved that simple needling at "A-Shi" acupoint promoted muscle regeneration and revealed underlying mechanisms of the beneficial effects of acupuncture and dry needle treatments.

Recovery of muscle mass and muscle oxidative phenotype following disuse does not require GSK-3 inactivation

BACKGROUND

Physical inactivity contributes to muscle wasting and reductions in mitochondrial oxidative phenotype (OXPHEN), reducing physical performance and quality of life during aging and in chronic disease. Previously, it was shown that inactivation of glycogen synthase kinase (GSK)-3β stimulates muscle protein accretion, myogenesis, and mitochondrial biogenesis. Additionally, GSK-3β is inactivated during recovery of disuse-induced muscle atrophy.

AIM

Therefore, we hypothesize that GSK-3 inhibition is required for reloading-induced recovery of skeletal muscle mass and OXPHEN.

METHODS

Wild-type (WT) and whole-body constitutively active (C.A.) Ser^21/9 GSK-3α/β knock-in mice were subjected to a 14-day hind-limb suspension/14-day reloading protocol. Soleus muscle mass, fiber cross-sectional area (CSA), OXPHEN (abundance of sub-units of oxidative phosphorylation (OXPHOS) complexes and fiber-type composition), as well as expression levels of their main regulators (respectively protein synthesis/degradation, myogenesis and peroxisome proliferator-activated receptor-γ co-activator-1α (PGC-1α) signaling) were monitored.

RESULTS

Subtle but consistent differences suggesting suppression of protein turnover signaling and decreased expression of several OXPHOS sub-units and PGC-1α signaling constituents were observed at baseline in C.A. GSK-3 versus WT mice. Although soleus mass recovery during reloading occurred more rapidly in C.A. GSK-3 mice, this was not accompanied by a parallel increased CSA. The OXPHEN response to reloading was not distinct between C.A. GSK-3 and WT mice. No consistent or significant differences in reloading-induced changes in the regulatory steps of protein turnover, myogenesis or muscle OXPHEN were observed in C.A. GSK-3 compared to WT muscle.

CONCLUSION

This study indicates that GSK-3 inactivation is dispensable for reloading-induced recovery of muscle mass and OXPHEN.

Short-term creatine supplementation changes protein metabolism signaling in hindlimb suspension

The effect of a short-term creatine supplementation on hindlimb suspension (HS)-induced muscle atrophy was investigated. Creatine monohydrate (5 g/kg b.w. per day) or placebo, divided in 2 daily doses, was given by oral gavage for 5 days. Rats were maintained in HS with dietary supplementation concomitantly for 5 days. Body weight, soleus and EDL muscle masses, and cross-sectional areas (CSA) of the muscle fibers were measured. Signaling pathways associated with skeletal muscle mass regulation (FST, MSTN, FAK, IGF-1, MGF, Akt, mTOR, atrogin-1, and MuRF1 expressions, and Akt, S6, GSK3B, and 4EBP1 proteins) were evaluated in the muscles. Soleus muscle exhibited more atrophy than the EDL muscle due to HS. Creatine supplementation attenuated the decrease of wet weight and increased p-4EBP1 protein in the EDL muscle of HS rats. Also, creatine increased mTOR and atrogin-1 expressions in the same muscle and condition. In the absence of HS, creatine supplementation increased FAK and decreased MGF expressions in the EDL muscle. Creatine attenuated the increase in FST expression due to HS in the soleus muscle. MuRF1 expression increased in the soleus muscle due to creatine supplementation in HS animals whereas atrogin-1 expression increased still further in this group compared with untreated HS rats. In conclusion, short-term creatine supplementation changed protein metabolism signaling in soleus and EDL muscles. However, creatine supplementation only slightly attenuated the mass loss of both muscles and did not prevent the CSA reduction and muscle strength decrease induced by HS for 5 days.

Myoprotective Potential of Creatine Is Greater than Whey Protein after Chemically-Induced Damage in Rat Skeletal Muscle

The myoprotective effects of creatine monohydrate (CR) and whey protein (WP) are equivocal, with the use of proxy measures of muscle damage making interpretation of their effectiveness limited. The purpose of the study was to determine the effects of CR and WP supplementation on muscle damage and recovery following controlled, chemically-induced muscle damage. Degeneration of the extensor digitorum longus (EDL) muscle was induced by bupivacaine in rats supplemented with either CR, WP, or standard rat chow (CON). At day 7 and 14 post-myotoxic injury, injured EDL muscles were surgically removed and tested for isometric contractile properties, followed by the contralateral, non-injured EDL muscle. At the completion of testing, muscles were snap-frozen in liquid nitrogen and stored for later analysis. Data were analyzed using analysis of variance. Creatine-supplemented muscles displayed a greater proportion of non-damaged (intact) fibers (p = 0.002) and larger cross-sectional areas of regenerating and non-damaged fibers (p = 0.024) compared to CON muscles at day 7 post-injury. At day 14 post-injury, CR-supplemented muscles generated higher absolute forces concomitant with greater contractile protein levels compared to CON (p = 0.001, p = 0.008) and WP-supplemented muscles (p = 0.003, p = 0.006). Creatine supplementation appears to offer an element of myoprotection which was not observed following whey protein supplementation.

Severe Hyperhomocysteinemia Decreases Respiratory Enzyme and Na(+)-K(+) ATPase Activities, and Leads to Mitochondrial Alterations in Rat Amygdala

Severe hyperhomocysteinemia is caused by increased plasma levels of homocysteine (Hcy), a methionine derivative, and is associated with cerebral disorders. Creatine supplementation has emerged as an adjuvant to protect against neurodegenerative diseases, due to its potential antioxidant role. Here, we examined the effects of severe hyperhomocysteinemia on brain metabolism, and evaluated a possible neuroprotective role of creatine in hyperhomocysteinemia, by concomitant treatment with Hcy and creatine (50 mg/Kg body weight). Hyperhomocysteinemia was induced in young rats (6-day-old) by treatment with homocysteine (0.3-0.6 µmol/g body weight) for 23 days, and then the following parameters of rat amygdala were evaluated: (1) the activity of the respiratory chain complexes succinate dehydrogenase, complex II and cytochrome c oxidase; (2) mitochondrial mass and membrane potential; (3) the levels of necrosis and apoptosis; and (4) the activity and immunocontent of Na(+),K(+)-ATPase. Hcy treatment decreased the activities of succinate dehydrogenase and cytochrome c oxidase, but did not alter complex II activity. Hcy treatment also increased the number of cells with high mitochondrial mass, high mitochondrial membrane potential, and in late apoptosis. Importantly, creatine administration prevented some of the key effects of Hcy administration on the amygdala. We also observed a decrease in the activity and immunocontent of the α1 subunit of the Na(+),K(+)-ATPase in amygdala after Hcy- treatment. Our findings support the notion that Hcy modulates mitochondrial function and bioenergetics in the brain, as well as Na(+),K(+)-ATPase activity, and suggest that creatine might represent an effective adjuvant to protect against the effects of high Hcy plasma levels.

Role of creatine supplementation in exercise-induced muscle damage: A mini review

Muscle damage is induced by both high-intensity resistance and endurance exercise. Creatine is a widely used dietary supplement to improve exercise performance by reducing exercise-induced muscle damage. Many researchers have suggested that taking creatine reduces muscle damage by decreasing the inflammatory response and oxidative stress, regulating calcium homeostasis, and activating satellite cells. However, the underlying mechanisms of creatine and muscle damage have not been clarified. Therefore, this review discusses the regulatory effects of creatine on muscle damage by compiling the information collected from basic science and sports science research.

An experimental study of muscular injury repair in a mouse model of notexin-induced lesion with EPI® technique

BACKGROUND

The mechanisms of muscle injury repair after EPI® technique, a treatment based on electrical stimulation, have not been described. This study determines whether EPI® therapy could improve muscle damage.

METHODS

Twenty-four rats were divided into a control group, Notexin group (7 and 14 days) and a Notexin + EPI group. To induce muscle injury, Notexin was injected in the quadriceps of the left extremity of rats. Pro-inflammatory interleukin 1-beta (IL-1beta) and tumoral necrosis factor-alpha (TNF-alpha) were determined by ELISA. The expression of receptor peroxisome gamma proliferator activator (PPAR-gamma), vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor-1 (VEGF-R1) were determined by western-blot.

RESULTS

The plasma levels of TNF-alpha and IL-1beta in Notexin-injured rats showed a significant increase compared with the control group. EPI® produced a return of TNF-alpha and IL-1beta values to control levels. PPAR-gamma expression diminished injured quadriceps muscle in rats. EPI® increased PPAR-gamma, VEGF and VEGF-R1 expressions. EPI® decreased plasma levels of pro-inflammatory TNF-alpha and IL-1beta and increased anti-inflammatory PPAR-gamma and proangiogenic factors as well as VEGF and VEGF-R1 expressions.

CONCLUSION

The EPI® technique may affect inflammatory mediators in damaged muscle tissue and influences the new vascularization of the injured area. These results suggest that EPI® might represent a useful new therapy for the treatment of muscle injuries. Although our study in rats may represent a valid approach to evaluate EPI® treatment, studies designed to determine how the EPI® treatment may affect recovery of injury in humans are needed.

Muscle-specific GSK-3β ablation accelerates regeneration of disuse-atrophied skeletal muscle

Muscle wasting impairs physical performance, increases mortality and reduces medical intervention efficacy in chronic diseases and cancer. Developing proficient intervention strategies requires improved understanding of the molecular mechanisms governing muscle mass wasting and recovery. Involvement of muscle protein- and myonuclear turnover during recovery from muscle atrophy has received limited attention. The insulin-like growth factor (IGF)-I signaling pathway has been implicated in muscle mass regulation. As glycogen synthase kinase 3 (GSK-3) is inhibited by IGF-I signaling, we hypothesized that muscle-specific GSK-3β deletion facilitates the recovery of disuse-atrophied skeletal muscle. Wild-type mice and mice lacking muscle GSK-3β (MGSK-3β KO) were subjected to a hindlimb suspension model of reversible disuse-induced muscle atrophy and followed during recovery. Indices of muscle mass, protein synthesis and proteolysis, and post-natal myogenesis which contribute to myonuclear accretion, were monitored during the reloading of atrophied muscle. Early muscle mass recovery occurred more rapidly in MGSK-3β KO muscle. Reloading-associated changes in muscle protein turnover were not affected by GSK-3β ablation. However, coherent effects were observed in the extent and kinetics of satellite cell activation, proliferation and myogenic differentiation observed during reloading, suggestive of increased myonuclear accretion in regenerating skeletal muscle lacking GSK-3β. This study demonstrates that muscle mass recovery and post-natal myogenesis from disuse-atrophy are accelerated in the absence of GSK-3β.

Investigation of Sudden Death in Athletes: The Fittest Bodies in the Morgue

Sporting events are generally viewed as regulated activities with fit and healthy participants; therefore, when deaths occur, they draw considerable public interest. Athletic participants can be considered a vulnerable population based on inherent risks within certain sports and the associated physiologic stresses, which may complicate underlying medical conditions. Sudden deaths in young athletes participating in high school and collegiate organized sports occur at an average of four to six deaths per year; however, sudden deaths related to exercise outside of an organized sport setting remain unaccounted for in the overall prevalence of these deaths. A typical forensic pathology practice will see not only these higher-profile deaths occurring during an organized sporting event, but also lower-profile occurrences of individuals dying during more recreational or unstructured exercise. Sport-related deaths can essentially be categorized as those that occur due to dangers inherent in the sport itself, such as forms of heat-related illnesses, blunt force trauma, and water-related deaths, and those that occur due to susceptibilities of a given predisposed participant, including sickle cell trait, hypertrophic cardiomyopathy, and other cardiovascular diseases. This article will address both types of vulnerabilities and provide guidance for appropriate and specific medicolegal death investigation and autopsy procedures in these deaths.

Effect of hypoxia exposure on the recovery of skeletal muscle phenotype during regeneration

Hypoxia impairs the muscle fibre-type shift from fast-to-slow during post-natal development; however, this adaptation could be a consequence of the reduced voluntary physical activity associated with hypoxia exposure rather than the result of hypoxia per se. Moreover, muscle oxidative capacity could be reduced in hypoxia, particularly when hypoxia is combined with additional stress. Here, we used a model of muscle regeneration to mimic the fast-to-slow fibre-type conversion observed during post-natal development. We hypothesised that hypoxia would impair the recovery of the myosin heavy chain (MHC) profile and oxidative capacity during muscle regeneration. To test this hypothesis, the soleus muscle of female rats was injured by notexin and allowed to recover for 3, 7, 14 and 28 days under normoxia or hypobaric hypoxia (5,500 m altitude) conditions. Ambient hypoxia did not impair the recovery of the slow MHC profile during muscle regeneration. However, hypoxia moderately decreased the oxidative capacity (assessed from the activity of citrate synthase) of intact muscle and delayed its recovery in regenerated muscle. Hypoxia transiently increased in both regenerated and intact muscles the content of phosphorylated AMPK and Pgc-1α mRNA, two regulators involved in mitochondrial biogenesis, while it transiently increased in intact muscle the mRNA level of the mitophagic factor BNIP3. In conclusion, hypoxia does not act to impair the fast-to-slow MHC isoform transition during regeneration. Hypoxia alters the oxidative capacity of intact muscle and delays its recovery in regenerated muscle; however, this adaptation to hypoxia was independent of the studied regulators of mitochondrial turn-over.

Monocarboxylate transporter expression at the onset of skeletal muscle regeneration

The onset of skeletal muscle regeneration is characterized by proliferating myoblasts. Proliferating myoblasts have an increased energy demand and lactate exchange across the sarcolemma can be used to address this increased demand. Monocarboxylate transporters (MCTs) are involved in lactate transport across the sarcolemma and are known to be affected by various physiological stimuli. However, MCT expression at the onset of skeletal muscle regeneration has not been determined. The purpose of this study was to determine if skeletal muscle regeneration altered MCT expression in regenerating tibialis anterior (TA) muscle. Male C57/BL6 mice were randomly assigned to either a control (uninjured) or bupivacaine (injured) group. Three days post injection, the TA was extracted for determination of protein and gene expression. A 21% decrease in muscle mass to tibia length (2.4 ± 0.1 mg/mm vs. 1.9 ± 0.2 mg/mm, P < 0.02) was observed. IGF-1 and MyoD gene expression increased 5.0-fold (P < 0.05) and 3.5-fold (P < 0.05), respectively, 3 days post bupivacaine injection. MCT-1 protein was decreased 32% (P < 0.03); however, MCT-1 gene expression was not altered. There was no difference in MCT4 protein or gene expression. Lactate dehydrogenase (LDH)-A protein expression increased 71% (P < 0.0004). Protein levels of LDH-B and mitochondrial enzyme cytochrome C oxidase subunit decreased 3 days post bupivacaine injection. CD147 and PKC-θ protein increased 64% (P < 0.03) and 79% (P < 0.02), respectively. MCT1 but not MCT4 expression is altered at the onset of skeletal muscle regeneration possibly in an attempt to regulate lactate uptake and use by skeletal muscle cells.