Adult Rat Muscle Research Articles

Repeated unilateral injections of botulinum toxin in masticatory muscles in adult rats do not amplify condylar and alveolar bone loss nor modify the volume of the hypertrophic bone proliferation at enthesis

ObjectivesBotulinum toxin is used in human in repeatedly masticatory muscles injections. A single BTX injection in animal induces mandibular bone loss with a muscle enthesis hypertrophic metaplasia. Our aim was to evaluate mandibular bone changes after unilateral repeated injections of BTX in adult rats. Study designMature male rats were randomized into 3 groups: one, two or three injections. Each rat received injections in right masseter and temporalis muscles. The left side was the control side. Microcomputed tomography was used to perform 2D and 3D analyses. ResultsBone loss was evidenced on the right sides of alveolar and condylar bone. Alveolar bone volume increased in both control left side and injected right side whereas condylar bone volume remained constant in all groups, for both sides. Enthesis bone hypertrophic metaplasias were evidenced on the BTX injected sides without any modification with the number of injections. ConclusionBTX repeated injections in masticatory muscles lead to major mandibular condylar and alveolar bone loss that does not worsen. They lead to the occurrence of an enthesis bone proliferation that is not dependent on the number of injections. These results are an argument for the safety of BTX injections in masticatory muscles in human.

Combined regenerative rehabilitation improves recovery following volumetric muscle loss injury in a rat model.

Volumetric muscle loss (VML) injury causes irreversible deficits in muscle mass and function, often resulting in permanent disability. The current standard of care is physical therapy, but it is limited in mitigating functional deficits. We have previously optimized a rehabilitation technique using electrically stimulated eccentric contraction training (EST) that improved muscle mass, strength, and size in VML-injured rats. A biosponge scaffold composed of extracellular matrix proteins has previously enhanced muscle function postVML. This study aimed to determine whether combining a regenerative therapy (i.e., biosponge) with a novel rehabilitation technique (i.e., EST) could enhance recovery in a rat model of VML. A VML defect was created by removing ~20% of muscle mass from the tibialis anterior muscle in adult male Lewis rats. Experimental groups included VML-injured rats treated with biosponge with EST or biosponge alone (n = 6/group). EST was implemented 2 weeks postinjury at 150 Hz and was continued for 4 weeks. A linear increase in eccentric torque over 4 weeks showed the adaptability of the VML-injured muscle to EST. Combining biosponge with EST improved peak isometric torque by ~52% compared with biosponge treatment alone at 6 weeks postinjury. Application of EST increased MyoD gene expression and the percentage of large (>2000 μm2) type 2B myofibers but reduced fibrotic tissue deposition in VML-injured muscles. Together, these changes may provide the basis for improved torque production. This study demonstrates the potential for combined regenerative and rehabilitative therapy to improve muscle recovery following VML.

Effects of age and diet consistency on the expression of myosin heavy-chain isoforms on jaw-closing and jaw-opening muscles in a rat model.

Skeletal craniofacial morphology can be influenced by changes in masticatory muscle function, which may also change the functional profile of the muscles. To investigate the effects of age and functional demands on the expression of Myosin Heavy-Chain (MyHC) isoforms in representative jaw-closing and jaw-opening muscles, namely the masseter and digastric muscles respectively. Eighty-four male Wistar rats were divided into four age groups, namely an immature (n = 12; 4-week-old), early adult (n = 24; 16-week-old), adult (n = 24; 26-week-old) and mature adult (n = 24; 38-week-old) group. The three adult groups were divided into two subgroups each based on diet consistency; a control group fed a standard (hard) diet, and an experimental group fed a soft diet. Rats were sacrificed, and masseter and digastric muscles dissected. Real-time quantitative polymerase chain reaction was used to compare the mRNA transcripts of the MyHC isoforms-Myh7 (MyHC-I), Myh2 (MyHC-IIa), Myh4 (MyHC-IIb) and Myh1 (MyHC-IIx)-of deep masseter and digastric muscles. In the masseter muscle, hypofunction increases Myh1 (26, 38 weeks; p < .0001) but decreases Myh4 (26 weeks; p = .046) and Myh2 (26 weeks; p < .0001) expression in adult rats. In the digastric muscle, hypofunction increases Myh1 expression in the mature adult rats (38 weeks; p < .0001), while Myh2 expression decreases in adult rats (26 weeks; p = .021) as does Myh4 (26 weeks; p = .001). Myh7 expression is increased in the digastric muscle of mature adult rats subjected to hypofunction (38 weeks; p = <.0001), while it is very weakly expressed in the masseter. In jaw-opening and jaw-closing muscles, differences in myosin expression between hard- and soft-diet-fed rats become evident in adulthood, suggesting that long-term alteration of jaw function is associated with changes in the expression of MyHC isoforms and potential fibre remodelling. This may give insight into the role of function on masticatory muscles and the resultant craniofacial morphology.

Ladder-based resistance training with the progression of training load altered the tibial nerve ultrastructure and muscle fiber area without altering the morphology of the postsynaptic compartment.

Scientific evidence regarding the effect of different ladder-based resistance training (LRT) protocols on the morphology of the neuromuscular system is scarce. Therefore, the present study aimed to compare the morphological response induced by different LRT protocols in the ultrastructure of the tibial nerve and morphology of the motor endplate and muscle fibers of the soleus and plantaris muscles of young adult Wistar rats. Rats were divided into groups: sedentary control (control, n = 9), a predetermined number of climbs and progressive submaximal intensity (fixed, n = 9), high-intensity and high-volume pyramidal system with a predetermined number of climbs (Pyramid, n = 9) and lrt with a high-intensity pyramidal system to exhaustion (failure, n = 9). myelinated fibers and myelin sheath thickness were statistically larger in pyramid, fixed, and failure. myelinated axons were statistically larger in pyramid than in control. schwann cell nuclei were statistically larger in pyramid, fixed, and failure. microtubules and neurofilaments were greater in pyramid than in control. morphological analysis of the postsynaptic component of the plantar and soleus muscles did not indicate any significant difference. for plantaris, the type i myofibers were statistically larger in the pyramid and fixed compared to control. the pyramid, fixed, and failure groups for type ii myofibers had larger csa than control. for soleus, the type i myofibers were statistically larger in the pyramid than in control. pyramid and fixed had larger csa for type ii myofibers than control and failure. the pyramid and fixed groups showed greater mass progression delta than the failure. We concluded that the LRT protocols with greater volume and progression of accumulated mass elicit more significant changes in the ultrastructure of the tibial nerve and muscle hypertrophy without endplate changes.

Maternal Protein Restriction Inhibits Insulin Signaling and Insulin Resistance in the Skeletal Muscle of Young Adult Rats.

Infants with fetal growth restriction (FGR) are at a risk of developing metabolic syndromes in adulthood. We hypothesized that skeletal muscle degeneration by nutrition-restricted FGR results in abnormal insulin signaling and epigenetic changes. To develop a protein-restricted FGR model, rats were fed a low-protein diet (7% protein) during the gestational period; rats fed a normal diet (20% protein) were used as controls. At 8 and 12 weeks of age, the pups were subjected to oral glucose tolerance test (OGTT) and insulin tolerance test (ITT) to evaluate insulin resistance. At 12 weeks, the mRNA and protein levels of insulin signaling pathway molecules in the skeletal muscles were examined. DNA methylation of promoters was detected. DNA extracted from skeletal muscles was used as a template for methylation-specific PCR analysis of GLUT4. The body weight of FGR rats from birth to 8 weeks was significantly lower than that of the controls; no significant difference was observed between the groups at 12 weeks. In the OGTT and ITT, the incremental area under the curve (iAUC) was significantly higher in FGR rats than in the controls at 12 weeks. The mRNA and protein levels of Akt2 and GLUT4 in the plantar muscles were significantly lower in FGR rats than in the controls. GLUT4 methylation was comparable between the groups. Protein-restricted FGR rats showed insulin resistance and altered insulin signaling in skeletal muscles after 12 weeks. However, we could not demonstrate the involvement of DNA methylation in this model.

Abstract 213: High-Throughput Analysis of Mitochondrial Morphology in Neurons Post-Mitochondrial Transplantation

Background: Mitochondrial transplantation (MTx) improves neurological and survival outcomes in rats after cardiac arrest. However, the impact of transferred mitochondria on native mitochondrial features in neurons remains poorly assessed. Evaluating mitochondrial morphology provides insights into post-MTx mitochondrial dynamics in recipient neurons, aiding the understanding of cellular processes and targeted therapy development. Aim: To investigate whether increased uptake of donor mitochondria influences the morphology of native mitochondrial networks in neurons. Methods: We conducted in vitro MTx using the HT-22 neuron cell line. Native mitochondria in neurons were pre-labeled with MitoTracker Green. Extracellular mitochondria were isolated from healthy adult rat muscle tissue, labeled with MitoTracker Deep Red, and co-cultured with neurons. Confocal microscopy captured 2D fluorescence images. MitoHacker, a computational program, facilitated high-throughput analysis of 27 mitochondrial morphometric markers. Results: We analyzed 62 images of cells ( Figure ). MitoHacker successfully identified features of native and transferred donor mitochondria. Linear regression analysis revealed that total donor mitochondrial area had positive correlations with native mitochondrial counts, total area, minor axis length of mitochondrion, mitochondrial averaged density, and mitochondrial branch length, and a negative correlation with distance between mitochondrial location and nucleus (all P&lt;0.05). These findings suggest that increased amounts of transferred mitochondria can positively influence native mitochondrial biogenesis, proliferation, accumulation, and activated mitochondrial dynamics and networking in recipient neurons. Conclusion: Using the deep learning-based mitochondrial morphology analysis, our study provides evidence that MTx significantly impacts mitochondrial morphology and dynamics in recipient cells.

Retracted: Beta-Sitosterol Facilitates GLUT4 Vesicle Fusion on the Plasma Membrane via the Activation of Rab/IRAP/Munc 18 Signaling Pathways in Diabetic Gastrocnemius Muscle of Adult Male Rats.

[This retracts the article DOI: 10.1155/2022/7772305.].

Maternal Di-(2-Ethylhexyl) Phthalate (DEHP) Exposure Impairs Insulin Signal in the Liver and Gastrocnemius Muscles of Female Offspring Rats

Di-(2-Ethylhexyl) Phthalate (DEHP) is a potent endocrine disruptor that is commonly present in consumer products and cosmetics. Exposure to DEHP during gestational and lactational periods can adversely affect glucoregulation and lead to the onset of diabetes in progeny. The liver and gastrocnemius muscles play an important role in regulating glucose metabolism and insulin action. This study was designed to investigate the effect of maternal DEHP exposure on insulin signaling molecules in the liver and gastrocnemius muscles of adult female offspring rats. Rat dams were given DEHP (10 and 100 mg/kg b.wt./day) by oral gavage from gestation day 9 (GD 9) to the end of the lactation period Postnatal Day (PND) 21. On PND 80, female offspring rats in diestrus were euthanized and found reduced body weight, organ (liver and gastrocnemius) weight, and hyperglycemia in DEHP-exposed rats. Western blots revealed a dose-dependent reduction in the expression of Insulin Receptor - (IR), IRS, Akt, and GSK-3β proteins as well as their phosphorylated forms in the liver and gastrocnemius muscles of DEHP-exposed offspring rats. Maternal DEHP exposure reduced the levels of GLUT2 and GLUT4 level in the liver and gastrocnemius muscles, respectively. Liver and renal function markers were dose-dependently increased in the serum of offspring female rats born to DEHP exposed mother during gestation and lactation. Thus, the study revealed that maternal DEHP exposure impaired the expression of insulin signaling molecules in the two important tissues involved in glucose metabolism, the liver and gastrocnemius muscles, suggesting that phthalates exposure during development may contribute to the onset of diabetes in female offspring.

Granulocyte-colony stimulating factor ameliorates di-ethylhexyl phthalate-induced cardiac muscle injury via stem cells recruitment, Desmin protein regulation, antifibrotic and antiapoptotic mechanisms.

Phthalates are common plasticizers present in medical-grade plastics and other everyday products. Di-ethylhexyl phthalate (DEHP) has been noted as a causative risk factor for the initiation and augmentation of cardiovascular functional disorders. G-CSF is a glycoprotein found in numerous tissues throughout the body and is currently applied in clinical practice and has been tested in congestive heart failure. We aimed to examine in depth the effect of DEHP on the histological and biochemical structure of the cardiac muscle in adult male albino rats and the mechanisms underlying the possible ameliorative effect of G-CSF. Forty-eight adult male albino rats were divided into control group, DEHP group, DEHP+ G-CSF group and DEHP-recovery group. We measured serum levels of aspartate aminotransferase (AST), creatine kinase MB isoenzyme (CK-MB) and lactate dehydrogenase (LDH). Left ventricular sections were processed for light and electron microscope examination, and immunohistochemical staining of Desmin, activated Caspase-3 and CD34. DEHP significantly increased enzyme levels, markedly distorted the normal architecture of cardiac muscle fibers, downregulated Desmin protein levels and enhanced fibrosis, and apoptosis. G-CSF treatment significantly decreased the enzyme levels compared to DEHP group. It enhanced CD34 positive stem cells recruitment to injured cardiac muscle, therefore improved the ultrastructural features of most cardiac muscle fibers via anti-fibrotic and anti-apoptotic effects in addition to increased Desmin protein expression levels. The recovery group showed partial improvement due to persistent DEHP effect. In conclusion, administration of G-CSF effectively corrected the histopathological, immunohistochemical and biochemical alterations in the cardiac muscle after DEHP administration by stem cells recruitment, Desmin protein regulation, antifibrotic and antiapoptotic mechanisms.

Effect of Different Doses of Silver Nanoparticles on Lung and Cardiac Muscle of Adult Female Albino Rat (A Histological and Immunohistochemical Study)

Effect of Different Doses of Silver Nanoparticles on Lung and Cardiac Muscle of Adult Female Albino Rat (A Histological and Immunohistochemical Study)

Myosin Heavy-Chain Messenger Ribonucleic Acid (mRNA) Expression and Fibre Cross-Sectional Area in Masseter, Digastric, Gastrocnemius and Soleus Muscles of Young and Adult Rats.

Different demands on the muscles of mastication may influence their functional profile (size and distribution of muscle fibre types), which may change during growth and maturation, potentially influencing craniofacial growth. The aim of this study was to evaluate mRNA expression and cross-sectional area of masticatory muscle fibres compared with limb muscles in young and adult rats. Twenty-four rats were sacrificed at two different ages, namely 12 at 4 weeks (young) and 12 at 26 weeks (adult). The masseter, digastric, gastrocnemius and soleus muscles were dissected. Gene expression of myosin heavy-chain isoforms Myh7 (MyHC-I), Myh2 (MyHC-IIa), Myh4 (MyHC-IIb) and Myh1 (MyHC-IIx) in the muscles was measured using qRT-PCR RNA analysis, and immunofluorescence staining was performed to measure the cross-sectional area of different muscle fibre types. Different muscle types and ages were compared. Significant differences were found in the functional profile between masticatory and limb muscles. For the masticatory muscles, there was an increase in Myh4 expression with age, and this change was more intense for the masseter muscles, which also presented an increase in Myh1 expression, similarly to limb muscles. The fibre cross-sectional area of the masticatory muscles was generally smaller in young rats; however, this difference was less pronounced than in limb muscles.

Effect of β-Caryophyllene on oxidative stress, glucose metabolism in the skeletal muscle of high fat diet and fructose-induced type-2 diabetic adult male rats.

Skeletal muscle is where the majority of insulin-stimulated whole-body glucose elimination takes place under normal circumstances. A significant risk factor for metabolic diseases is high dietary fat consumption, which also increases stored fat mass. Natural solutions with anti-diabetic effectiveness and fewer side effects are becoming more popular as a result of the conventional pharmacological treatments' numerous negative side effects and high rates of secondary failure. Cannabis and a variety of culinary herbs and spices may include the naturally occurring sequiterpene β-caryophyllene. Among other things, it has antioxidant, anti-inflammatory, and anti-lipidemic properties. However, it is not yet known how β-caryophyllene affects the uptake and oxidation of glucose. Determining if β -caryophyllene has anti-diabetic properties in type-2 diabetes brought on by a high-fat diet was the objective of the current investigation. A sufficient dose of β-caryophyllene (200 mg/kg b.w.t., orally for 30 days) was given to type-2 diabetic rats fed a high-fat diet and given fructose as an inducer of diabetes to assess its anti-diabetic activity. The treatment of diabetes-induced rats with β -Caryophyllene restored the altered levels of blood glucose, serum insulin as well as the lipid parameters, oxidative stress markers, antioxidant enzymes. Our findings show that β-caryophyllene improves glycemia control by enhancing glucose absorption and oxidation in the skeletal muscle of type-2 diabetic rats. From the present findings, it is evident that β -caryophyllene can be used as an anti-diabetic drug.

Local analgesia of electroacupuncture is mediated by the recruitment of neutrophils and released β-endorphins.

The efficacy of acupuncture in treating pain diseases has been recognized in clinical practice, and its mechanism of action has been a hot topic in academic acupuncture research. Previous basic research on acupuncture analgesia has focused mostly on the nervous system, with few studies addressing the immune system as a potential pathway of acupuncture analgesia. In this study, we investigated the effect of electroacupuncture (EA) on the β-endorphins (β-END) content, END-containing leukocyte type and number, sympathetic neurotransmitter norepinephrine (NE), and chemokine gene expression in inflamed tissues. To induce inflammatory pain, about 200 µL of complete Frester adjuvant (CFA) was injected into the unilateral medial femoral muscle of adult Wistar rats. Electroacupuncture treatment was performed for 3 days beginning on day 4 after CFA injection, with parameters of 2/100 Hz, 2 mA, and 30 minutes per treatment. The weight-bearing experiment and enzyme-linked immunosorbent assay showed that EA treatment significantly relieved spontaneous pain-like behaviors and increased the level of β-END in inflamed tissue. Injection of anti-END antibody in inflamed tissue blocked this analgesic effect. Flow cytometry and immunofluorescence staining revealed that the EA-induced increase in β-END was derived from opioid-containing ICAM-1 + /CD11b + immune cells in inflamed tissue. In addition, EA treatment increased the NE content and expression of β2 adrenergic receptor (ADR-β2) in inflammatory tissues and upregulated Cxcl1 and Cxcl6 gene expression levels. These findings provide new evidence for the peripheral analgesic effect of acupuncture treatment by recruiting β-END-containing ICAM-1 + /CD11b + immune cells and increasing the β-END content at the site of inflammation.

Short-term fructose feeding alters tissue metabolic pathways by modulating microRNAs expression both in young and adult rats.

Dietary high fructose (HFrD) is known as a metabolic disruptor contributing to the development of obesity, diabetes, and dyslipidemia. Children are more sensitive to sugar than adults due to the distinct metabolic profile, therefore it is especially relevant to study the metabolic alterations induced by HFrD and the mechanisms underlying such changes in animal models of different ages. Emerging research suggests the fundamental role of epigenetic factors such as microRNAs (miRNAs) in metabolic tissue injury. In this perspective, the aim of the present study was to investigate the involvement of miR-122-5p, miR-34a-5p, and miR-125b-5p examining the effects induced by fructose overconsumption and to evaluate whether a differential miRNA regulation exists between young and adult animals. We used young rats (30days) and adult rats (90days) fed on HFrD for a short period (2weeks) as animal models. The results indicate that both young and adult rats fed on HFrD exhibit an increase in systemic oxidative stress, the establishment of an inflammatory state, and metabolic perturbations involving the relevant miRNAs and their axes. In the skeletal muscle of adult rats, HFrD impair insulin sensitivity and triglyceride accumulation affecting the miR-122-5p/PTP1B/P-IRS-1(Tyr612) axis. In liver and skeletal muscle, HFrD acts on miR-34a-5p/SIRT-1: AMPK pathway resulting in a decrease of fat oxidation and an increase in fat synthesis. In addition, liver and skeletal muscle of young and adult rats exhibit an imbalance in antioxidant enzyme. Finally, HFrD modulates miR-125b-5p expression levels in liver and white adipose tissue determining modifications in de novo lipogenesis. Therefore, miRNA modulation displays a specific tissue trend indicative of a regulatory network that contributes in targeting genes of various pathways, subsequently yielding extensive effects on cell metabolism.

VP.37 Sleep deprivation induces aging like changes in antigravity muscles of young adult male wistar rats

Sleep is essential for the cellular, organic and systemic functions of an organism. Sleep deprivation is associated with metabolic dysfunction and ageing is so. Muscle health at elderly age is one of the major risk factor. Poor muscle health is associated with a series of chronic and metabolic conditions that are prevalent in individuals who chronically experience poor-quality sleep. But there is no study deciphering the role of sleep deprivation on muscle ageing. Therefore, in the present study we have measured the ultrastructure, histopathology, and oxidative stressors in soleus muscle of wistar rat after sleep deprivation and recovery sleep. The experiments were conducted in18 rats of three groups. Group I rats had normal sleep wake cycle, Group II rats were subjected to 24 h sleep deprivation (SD) by gentle handling method1 and Group III rats had recovery sleep after 24 h SD. At the end of the sleep, sleep deprivation and recovery period, soleus muscle tissue was collected for ultrastructural, histological and oxidative stress markers. Oxidative damage was assessed by lipid peroxidation, catalase activity, reduced glutathione and nuclear labelling of 8-OHdG. The study was conducted as per the guidelines of the Institutional Animal Ethics Committee (960/IAEC/16). The data demonstrated that SD leads to ultrastructural changes in soleus muscle which includes sarcolemmal and mitochondrial alterations. In case of histopathological and histomorphological changes there was signs of tissue degeneration, inflammatory infiltrate in type I fibers and muscle atrophy was observed in soleus muscles. There was significant increase in level of 8-OHdG (p=0.02) and malondialdehyde in 24h SD (p=0.02) than control and recovery sleep groups. Moreover, the catalase activity and reduced glutathione level was significantly decreased in 24h SD group (p≤0.02) than control and recovery sleep. Therefore, we conclude that 24hr sleep deprivation leads to an ageing like state in the skeletal muscle, which was recovered after sleep rebound.

The impact of different exercise protocols on rat soleus muscle reinnervation and recovery following peripheral nerve lesion and regeneration.

Background: Incomplete functional recovery following traumatic peripheral nerve injury is common, mainly because not all axons successfully regenerate and reinnervate target muscles. Exercise can improve functional outcomes increasing the terminal sprouting during the muscle reinnervation. However, exercise is not a panacea per se. Indeed, the type of exercise adopted dramatically impacts the outcomes of rehabilitation therapy. To gain insight into the therapeutic effects of different exercise regimens on reinnervation following traumatic nerve lesion, we evaluated the impact of different clinically transferable exercise protocols (EPs) on metabolic and functional muscle recovery following nerve crush. Methods: The reinnervation of soleus muscle in adult nerve-crushed rats was studied following 6 days of different patterns (continuous or intermittent) and intensities (slow, mid, and fast) of treadmill running EPs. The effects of EPs on muscle fiber multiple innervation, contractile properties, metabolic adaptations, atrophy, and autophagy were assessed using functional and biochemical approaches. Results: Results showed that an intermittent mid-intensity treadmill EP improves soleus muscle reinnervation, whereas a slow continuous running EP worsens the functional outcome. However, the mid-intensity intermittent EP neither enhanced the critical mediators of exercise-induced metabolic adaptations, namely, PGC-1α, nor improved muscle atrophy. Conversely, the autophagy-related marker LC3 increased exclusively in the mid-intensity intermittent EP group. Conclusion: Our results demonstrated that an EP characterized by a mid-intensity intermittent activity enhances the functional muscle recovery upon a nerve crush, thus representing a promising clinically transferable exercise paradigm to improve recovery in humans following peripheral nerve injuries.

Maternal high-fat diet alters thermogenic markers but not muscle or brown adipose cannabinoid receptors in adult rats

AimsThe endocannabinoid system (ECS) increases food intake, appetite for fat and lipogenesis, while decreases energy expenditure (thermogenesis), contributing to metabolic dysfunctions. We demonstrated that maternal high-fat diet (HFD) alters cannabinoid signaling in brown adipose tissue (BAT) of neonate and weanling male rat offspring, which have increased adiposity but also higher energy expenditure in adulthood. In this study, the main objective was to investigate the ECS expression in thermogenic tissues as BAT and skeletal muscle of adult rats programmed by maternal HFD. We hypothesized that maternal HFD would modulate ECS and energy metabolism markers in BAT and skeletal muscle of adult male offspring. Materials and methodsFemale rats received standard diet (9.4 % of calories as fat) or isocaloric HFD (28.9 % of calories as fat) for 8 weeks premating and throughout gestation and lactation. Male offspring were weaned on standard diet and euthanatized in adulthood. Key findingsMaternal HFD increased body weight, adiposity, glycemia, leptinemia while decreased testosterone levels in adult offspring. Maternal HFD did not change cannabinoid receptors in BAT or skeletal muscle as hypothesized but increased the content of uncoupling protein and tyrosine hydroxylase (thermogenic markers) in parallel to changes in mitochondrial morphology in skeletal muscle of adult offspring. SignificanceIn metabolic programming models, the ECS modulation in the BAT and skeletal muscle may be more important early in life to adapt energy metabolism during maternal dietary insult, and other mechanisms are possibly involved in muscle metabolism long-term regulation.

Cannabidiol (CBD) Dosing: Plasma Pharmacokinetics and Effects on Accumulation in Skeletal Muscle, Liver and Adipose Tissue.

Oral cannabidiol (CBD) consumption is widespread in North America and Europe, as it has analgesic, neuroprotective and antitumor effects. Although oral CBD consumption in humans affords beneficial effects in epileptic and inflammatory states, its pharmacokinetics and subsequent uptake into tissue are largely unknown. This study investigated plasma pharmacokinetics and accumulation of CBD in gastrocnemius muscle, liver and adipose tissue in adult rats following oral gavage. CBD was fed relative to body mass at 0 (control), 30, 115, or 230 mg/Kg/day for 28 days; with 6 males and 6 females per dosing group. Pharmacokinetics were assessed on day 1 and day 28 in the group receiving CBD at 115 mg/Kg/day. The rise in tissue CBD was closely related to specific pharmacokinetic parameters, and adipose tissue levels were ~10 to ~100 fold greater than liver or muscle. Tissue CBD levels were moderately correlated between adipose and muscle, and adipose and liver, but were highly correlated for liver and muscle. CBD feeding resulted in several gender-specific effects, including changes in pharmacokinetics, relationships between pharmacokinetic parameters and tissue CBD and differences in tissue CBD levels. CBD accumulation in mammalian tissues has the potential to influence receptor binding and metabolism; therefore, the present findings may have relevance for developing oral dosing regimens.

MOTS‐c protein expression increases following aerobic exercise training and remains elevated during detraining

Mitochondrial open reading frame of the 12S rRNA‐c (MOTS‐c) is a mitochondrial‐derived peptide that is released into the circulation following intense physical activity and, purportedly, has systemic impacts on energy metabolism and insulin sensitivity. Exogenous administration of MOTS‐c in rodent models enhances physical activity / endurance and reduces fat mass in aged mice through the regulation of, in part, the glycolysis / pentose phosphate pathway and amino acid metabolism. Considering that mitochondrial volume and mitochondrial DNA copy number increase following chronic aerobic exercise training, we hypothesized that MOTS‐c expression also would be elevated in exercise‐trained skeletal muscle. MOTS‐c protein expression from phenotypically mixed plantaris muscles of adult female Sprague Dawley rats were compared from six conditions: sedentary (SED; n=11), voluntary exercise training for four (EX4; n=9), six (EX6; n=6), or eight weeks (EX8; n=8), and detraining after four (DETR4) or six (DETR6) weeks, which followed four or six weeks of exercise training, respectively. Total running distances were ~551±61, 371±94, 560±71, 321±44, and 519±27 km for EX4, EX6, EX8, DETR4 and DETR6, respectively. DETR4 rat running distance was significantly lower than EX4, EX8, and DETR6 rats (p&lt;0.01). Total muscle protein homogenate was isolated from mid‐belly muscle chunks and separated using 15% SDS‐PAGE gels (10 μg/sample). Following transfer, membranes were incubated with a custom rabbit anti‐rat MOTS‐c polyclonal antibody, developed, scanned, stripped and re‐probed for GAPDH as a loading control. MOTS‐c protein was significantly elevated from SED (set at 100%) to 188±61, 158±37, 212±27, 168±29, 223±36% in EX4, EX6, EX8, DETR4 and DETR6, respectively (p&lt;0.05). Furthermore, preliminary findings indicate that MOTS‐c is present exclusively within the cytoplasm of skeletal muscle and not compartmentalized within the nuclei or mitochondria. Given that long‐term aerobic exercise augments mitochondrial volume within skeletal muscle, our data suggest that the observed increase in MOTS‐c protein in the present study parallels this mitochondrial adaptation to aerobic physical activity. Taken together, these findings indicate that a more aerobically‐trained individual would have an enhanced MOTS‐c presence within skeletal muscle and, therefore, a greater potential to regulate energy and insulin sensitivity when MOTS‐c is released systemically; additionally, the potential benefits of MOTS‐c are sustained during a period of physical inactivity (e.g., detraining) following exercise training.

Mechanotherapy does not Enhance Recovery Following Muscle Disuse Atrophy in Female Rats

BackgroundRecovery from skeletal muscle atrophy is important for regaining function. We previously showed that mechanotherapy enhances regrowth of muscle in adult male rats by elevating protein synthesis.ObjectiveThe purpose of this study was to determine if female rats also respond to mechanotherapy during regrowth after disuse‐induced atrophy.HypothesisMechanotherapy in female rats augments muscle regrowth after atrophy by enhancing protein synthesis.MethodsAdult (10 month) F344/BN female rats were randomly assigned to one of four groups: weight‐bearing (WB; N=6), hindlimb suspension (HS; N=9), reambulation after HS without mechanotherapy (RA; N=9), or RA with mechanotherapy (RAM; N=10). HS lasted for 14 and RA for 7 days. Starting the day of RA, mechanotherapy was applied to the right gastrocnemius muscle at a load of 4.5N for 30 minutes every other day (4 bouts total). Rats received deuterium oxide (D2O) for determination of myofibrillar protein and RNA synthesis (Ksyn) and degradation (Kdeg). We analyzed gastrocnemius muscles for myonuclear number (dystrophin‐DAPI), satellite cell (SC) number (Pax7), and fiber type and cross‐sectional area (CSA; laminin‐myosin heavy chain). We used a one‐way ANOVA to determine statistical significance at p&lt;0.05. Values are mean ± SD.ResultsMuscle wet weight (g) was lower with HS (933 ± 56) compared to WB (1140 ± 86) and greater in RA (1012 ± 64) and RAM (1030 ± 41) compared to HS. However, no difference was observed between RA and RAM. Mean fiber CSA (µm2) was significantly lower in HS (1877 ± 244) compared to WB (2395 ± 248), while RA (2124 ± 287) was not different from WB or HS. RAM CSA (2013 ± 182) was lower than WB and not different from HS or RA. Myofibrillar Ksyn (mg/day) was lower in HS (13 ± 2.1) compared to WB (22 ± 2.2). RA (32 ± 3.2) and RAM (30 ± 4.3) were higher than HS and WB, but no difference was observed between RA and RAM. Myofibrillar Kdeg (1/t) was greater in HS (0.03 ± 0.004) compared to WB (0.02 ± 0.005), and RA (0.04 ± 0.007) and RAM (0.04 ± 0.005) were higher than HS and WB, but not different from each other. RNA Ksyn (%/day) was not different between WB (2 ± 0.2) and HS (2 ± 0.3), whereas RE (3 ± 0.4) and REM (4 ± 0.6) were both higher that WB and HS, but not different from each other. There were no differences in fiber type distribution between the groups. CSA of all fiber types was lower with HS, whereas no differences were observed between RA, RAM and HS. We did not find a significant difference in myonuclear number or centrally located nuclei between the groups. The number of SCs (per/fiber) was lower in HS (0.03 ± 0.01) and RA (0.04 ± 0.01) compared to WB (0.05 ± 0.008) and was higher in RAM (0.05 ± 0.02) compared to HS.ConclusionMuscle recovery from atrophy in female rats occurs with reambulation and elevated protein turnover is the underlying anabolic mechanism. We therefore conclude that the additional load using mechanotherapy does not enhance muscle recovery in females, which is different than the response previously published for males.