Fluid shear stress-induced mechanotransduction in myoblasts: Does it depend on the glycocalyx?

Muscle stem cells (MuSCs) are involved in muscle maintenance and regeneration. Mechanically loaded MuSCs within their native niche undergo tensile and shear deformations, but how MuSCs sense mechanical stimuli and translate these into biochemical signals regulating function and fate is still poorly understood. We aimed to investigate whether the glycocalyx is involved in the MuSC mechanoresponse, and whether MuSC morphology affects mechanical loading-induced pressure, shear stress, and fluid velocity distribution. FSS-induced deformation of active proliferating MuSCs (myoblasts) with intact or degraded glycocalyx was assessed by live-cell imaging. Glycocalyx-degradation did not significantly affect nitric oxide production, but reduced FSS-induced myoblast deformation and modulated gene expression. Finite-element analysis revealed that the distribution of FSS-induced pressure, shear stress, and fluid velocity on myoblasts was non-uniform, and the magnitude depended on myoblast morphology and apex-height. In conclusion, our results suggest that the glycocalyx does not play a role in NO production in myoblasts but might impact mechanotransduction and gene expression, which needs further investigation. Future studies will unravel the underlying mechanism by which the glycocalyx affects FSS-induced myoblast deformation, which might be related to increased drag forces. Moreover, MuSCs with varying apex-height experience different levels of FSS-induced pressure, shear stress, and fluid velocity, suggesting differential responsiveness to fluid shear forces.

Mechanosensors control skeletal muscle mass, molecular clocks, and metabolism.

BACKGROUND: Skeletal muscles (SkM) are mechanosensitive, with mechanical unloading resulting in muscle-devastating conditions and altered metabolic properties. However, it remains unexplored whether these atrophic conditions affect SkM mechanosensors and molecular clocks, both crucial for their homeostasis and consequent physiological metabolism. METHODS: We induced SkM atrophy through 14 days of hindlimb suspension (HS) in 10 male C57BL/6J mice and 10 controls (CTR). SkM histology, gene expressions and protein levels of mechanosensors, molecular clocks and metabolism-related players were examined in the m. Gastrocnemius and m. Soleus. Furthermore, we genetically reduced the expression of mechanosensors integrin-linked kinase (Ilk1) and kindlin-2 (Fermt2) in myogenic C2C12 cells and analyzed the gene expression of mechanosensors, clock components and metabolism-controlling genes. RESULTS: Upon hindlimb suspension, gene expression levels of both core molecular clocks and mechanosensors were moderately upregulated in m. Gastrocnemius but strongly downregulated in m. Soleus. Upon unloading, metabolism- and protein biosynthesis-related genes were moderately upregulated in m. Gastrocnemius but downregulated in m. Soleus. Furthermore, we identified very strong correlations between mechanosensors, metabolism- and circadian clock-regulating genes. Finally, genetically induced downregulations of mechanosensors Ilk1 and Fermt2 caused a downregulated mechanosensor, molecular clock and metabolism-related gene expression in the C2C12 model. CONCLUSIONS: Collectively, these data shed new lights on mechanisms that control muscle loss. Mechanosensors are identified to crucially control these processes, specifically through commanding molecular clock components and metabolism.

Are dietary intake and nutritional status of specific polyunsaturated fatty acids correlated with sarcopenia outcomes in community-dwelling older adults with sarcopenia? - Exploratory results from ENHANce.

AIMS: To explore the relationship between dietary polyunsaturated fatty acids (PUFAs) intake, nutritional PUFAs status and sarcopenia outcomes in sarcopenic older adults. METHODS: The Exercise and Nutrition for Healthy AgeiNg (ENHANce) is an ongoing 5-armed triple blinded randomized controlled trial, in sarcopenic older adults (> 65y) aiming to assess the effect of combined anabolic interventions (protein, omega-3 supplement and exercise) on physical performance in these adults, compared to single/placebo interventions. Baseline data were used for a secondary, exploratory, cross-sectional analysis. Dietary PUFAs intake was assessed with 4-day food records, status with RBC membrane fatty acids profiles. Spearman's rho(ρ) correlation coefficients were calculated to explore associations of PUFAs intake and status with sarcopenia-defining parameters (muscle strength, mass and physical performance), physical activity (step count) and quality of life (SF-36, SarQoL). RESULTS: In total, 29 subjects (9♂/20♀, mean age 76.3 ± 5.4y) were included. Total omega-3 intake of participants (1.99 ± 0.99 g/d) was below the recommended intake (♂:2.8-5.6 g/d; ♀:2.2-4.4 g/d). Intake and status of PUFAs were not correlated. Regarding correlations with outcomes, α-linolenic acid status was inversely associated with appendicular lean mass (aLM) (ρ:-0.439; p = 0.017), whereas docosahexaenoic acid status was positively associated with aLM (ρ:0.388; p = 0.038). Some omega-3 PUFAs intake and status markers were positively associated with step count, SF-36 and SarQoL scores, whereas gamma-linolenic acid status was inversely associated with SF-36 physical component summary score (ρ = -0.426; p = 0.024). CONCLUSIONS: Although intake of omega-3 and omega-6 was low, the present exploratory study generated new hypotheses for potential correlations of PUFAs intake and status with sarcopenia outcomes in older adults with sarcopenia.

Recreational Football Training Increases Leg-Extensor Velocity Production in 55- To 70-Year Old Adults: A Randomized Controlled Trial.

This study investigated the effects of 10 weeks of recreational football training on the leg-extensor force-velocity (F-V) profile in 55- to 70-year-old adults. Simultaneous effects on functional capacity, body composition and endurance exercise capacity were examined. Forty participants (age 63.5 ± 3.9 years; 36♂ 4♀) were randomized in a football training (FOOT, n = 20) and a control (CON, n = 20) group. FOOT performed 45-min to 1-h of football training sessions with small-sided games twice a week. Pre- and post-intervention assessments were performed. The results revealed a greater increase in maximal velocity (d = 0.62, pint = 0.043) in FOOT compared to CON. No interaction effects were found for maximal power and force (pint > 0.05). 10-m fast walk improved more (d = 1.39, pint < 0.001), 3-step stair ascent power (d = 0.73, pint = 0.053) and body fat percentage (d = 0.61, pint = 0.083) tended to improve more in FOOT than in CON. RPE and HR values at the highest speed level during a submaximal graded treadmill test decreased more in FOOT compared to CON (RPE: d = 0.96, pint = 0.005; HR: d = 1.07, pint = 0.004). Both the number of accelerations and decelerations as well as the distance spent in moderate- and high-speed zones increased markedly throughout the 10-week period (p < 0.05). Participants perceived the sessions as very enjoyable and feasible. In conclusion, recreational football training resulted in improved leg-extensor velocity production, which translated to a better performance on functional capacity tests that rely on a high execution velocity. Simultaneously, exercise tolerance was improved and body fat percentage tended to reduce. It appears that short-term recreational football training can induce broad-spectrum health benefits in 55- to 70-year-old adults with only 2 hours of training per week.

Molecular networks underlying cannabinoid signaling in skeletal muscle plasticity.

The cannabinoid system is ubiquitously present and is classically considered to engage in neural and immunity processes. Yet, the role of the cannabinoid system in the whole body and tissue metabolism via central and peripheral mechanisms is increasingly recognized. The present review provides insights in (i) how cannabinoid signaling is regulated via receptor-independent and -dependent mechanisms and (ii) how these signaling cascades (might) affect skeletal muscle plasticity and physiology. Receptor-independent mechanisms include endocannabinoid metabolism to eicosanoids and the regulation of ion channels. Alternatively, endocannabinoids can act as ligands for different classic (cannabinoid receptor 1 [CB1 ], CB2 ) and/or alternative (e.g., TRPV1, GPR55) cannabinoid receptors with a unique affinity, specificity, and intracellular signaling cascade (often tissue-specific). Antagonism of CB1 might hold clues to improve oxidative (mitochondrial) metabolism, insulin sensitivity, satellite cell growth, and muscle anabolism, whereas CB2 agonism might be a promising way to stimulate muscle metabolism and muscle cell growth. Besides, CB2 ameliorates muscle regeneration via macrophage polarization toward an anti-inflammatory phenotype, induction of MyoD and myogenin expression and antifibrotic mechanisms. Also TRPV1 and GPR55 contribute to the regulation of muscle growth and metabolism. Future studies should reveal how the cannabinoid system can be targeted to improve muscle quantity and/or quality in conditions such as ageing, disease, disuse, and metabolic dysregulation, taking into account challenges that are inherent to modulation of the cannabinoid system, such as central and peripheral side effects.

Voluntary exercise does not improve muscular properties or functional capacity during C26-induced cancer cachexia in mice.

Exercise training is considered as a potential intervention to counteract muscle degeneration in cancer cachexia. However, evidence to support such intervention is equivocal. Therefore, we investigated the effect of exercise training, i.e. voluntary wheel running, on muscle wasting, functional capacity, fiber type composition and vascularization during experimental cancer cachexia in mice. Balb/c mice were injected with PBS (CON) or C26 colon carcinoma cells to induce cancer cachexia (C26). Mice had free access to a running wheel in their home cage (CONEX and C26EX, n = 8-9) or were sedentary (CONS and C26S, n = 8-9). Mice were sacrificed 18 days upon tumor cell injection. Immunohistochemical analyes were performed on m. gastrocnemius and quadriceps, and ex vivo contractile properties were assessed in m. soleus and extensor digitorum longus (EDL). Compared with CON, C26 mice exhibited body weight loss (~ 20 %), muscle atrophy (~ 25 %), reduced grip strength (~ 25 %), and lower twitch and tetanic force (~ 20 %) production in EDL but not in m. soleus. Furthermore, muscle of C26 mice were characterizd by a slow-to-fast fiber type shift (type IIx fibers: +57 %) and increased capillary density (~ 30 %). In C26 mice, wheel running affect neither body weight loss, nor muscle atrophy or functional capacity, nor inhibited tumor growth. However, wheel running induced a type IIb to type IIa fiber shift in m. quadriceps from both CON and C26, but not in m. gastrocnemius. Wheel running does not exacerbate muscular degeneration in cachexic mice, but, when voluntary, is insufficient to improve the muscle phenotype.

Cardiotoxin-induced skeletal muscle injury elicits profound changes in anabolic and stress signaling, and muscle fiber type composition.

To improve muscle healing upon injury, it is of importance to understand the interplay of key signaling pathways during muscle regeneration. To study this, mice were injected with cardiotoxin (CTX) or PBS in the Tibialis Anterior muscle and were sacrificed 2, 5 and 12 days upon injection. The time points represent different phases of the regeneration process, i.e. destruction, repair and remodeling, respectively. Two days upon CTX-injection, p-mTORC1 signaling and stress markers such as BiP and p-ERK1/2 were upregulated. Phospho-ERK1/2 and p-mTORC1 peaked at d5, while BiP expression decreased towards PBS levels. Phospho-FOXO decreased 2 and 5 days following CTX-injection, indicative of an increase in catabolic signaling. Furthermore, CTX-injection induced a shift in the fiber type composition, characterized by an initial loss in type IIa fibers at d2 and at d5. At d5, new type IIb fibers appeared, whereas type IIa fibers were recovered at d12. To conclude, CTX-injection severely affected key modulators of muscle metabolism and histology. These data provide useful information for the development of strategies that aim to improve muscle molecular signaling and thereby recovery.

Exercise and Nutrition for Healthy AgeiNg (ENHANce) project - effects and mechanisms of action of combined anabolic interventions to improve physical functioning in sarcopenic older adults: study protocol of a triple blinded, randomized controlled trial.

BACKGROUND: The Exercise and Nutrition for Healthy AgeiNg (ENHANce) project aims to assess the combined effects of exercise and nutritional interventions to prevent loss of skeletal muscle mass and function with ageing, and to determine the underlying mechanisms of action. METHODS: One hundred eightycommunity-dwelling sarcopenic individuals (≥ 65 years) are allocated in a randomized controlled trial (RCT) in a 1:1 ratio into five groups for a 12-week intervention period, followed by a 12-week follow-up period: 1) exercise intervention +protein placebo +omega-3 fatty acids placebo; 2) protein +omega-3 fatty acids placebo; 3) exercise intervention +protein +omega-3 fatty acids placebo; 4) exercise intervention +protein +omega-3 fatty acids; 5) protein placebo +omega-3 fatty acids placebo. All interventions are in line with recommendations of expert groups such as the American College of Sports Medicine and the PROT-AGE study group and individualized to the physical capabilities and nutritional intake of each participant. Sarcopenia is diagnosed by the assessment of gait speed, handgrip strength (Jamar handheld dynamometer), chair stand test and muscle mass (DXA) according to the European Working Group on Sarcopenia in Older People (EWGSOP2) criteria. Participants, researchers and statisticians are blinded to omega-3 fatty acids and protein treatment. Compliance to the exercise program, protein and omega-3 fatty acids interventions is objectively measured, by monitoring movement by an activity monitor, determining nitrogen content in urine and analyzing the fatty acid composition of the red blood cell membrane. The primary outcome of the RCT is the change in Short Physical Performance Battery (SPPB) score. Secondary endpoints are, among others, changes in muscle mass, strength and function, objective compliance to interventions, changes in muscle and blood biomarkers related to sarcopenia, cognition, quality of life and falls. DISCUSSION: This RCT in well-defined sarcopenic older adults assesses the effects of combined anabolic interventions, including the additive effects of omega-3 fatty acids supplements, compared to single or placebo interventions. Compliance with the exercise intervention and with the intake of nutritional supplements is measured objectively. Also, blood and muscle samples will be used to explore the underlying determinants that contribute to the mechanism of action of anabolic interventions. TRIAL REGISTRATION: Clinicaltrials.gov: NCT03649698 , retrospectively registered at 28 August 2018, first participant was randomized 16 February 2018.

The effect of minimally invasive surgical aortic valve replacement on postoperative pulmonary and skeletal muscle function.

NEW FINDINGS: What is the central question of this study? How does surgical aortic valve replacement affect cardiopulmonary and muscle function during exercise? What is the main finding and its importance? Early after the surgical replacement of the aortic valve a significant decline in pulmonary function was observed, which was followed by a decline in skeletal muscle function in the subsequent weeks of recovery. These date reiterate, despite restoration of aortic valve function, the need for a tailored rehabilitation programme for the respiratory and peripheral muscular system. ABSTRACT: Suboptimal post-operative improvements in functional capacity are often observed after minimally invasive aortic valve replacement (mini-AVR). It remains to be studied how AVR affects the cardiopulmonary and skeletal muscle function during exercise to explain these clinical observations and to provide a basis for improved/tailored post-operative rehabilitation. Twenty-two patients with severe aortic stenosis (AS) (aortic valve area (AVA) <1.0 cm²) were pre-operatively compared to 22 healthy controls during submaximal constant-workload endurance-type exercise for oxygen uptake ( V̇O2 ), carbon dioxide output ( V̇CO2 ), respiratory gas exchange ratio, expiratory volume ( V̇E ), ventilatory equivalents for O2 ( V̇E / V̇O2 ) and CO2 ( V̇E / V̇CO2 ), respiratory rate (RR), tidal volume (Vt ), heart rate (HR), oxygen pulse ( V̇O2 /HR), blood lactate, Borg ratings of perceived exertion (RPE) and exercise-onset V̇O2 kinetics. These exercise tests were repeated at 5 and 21 days after AVR surgery (n = 14), along with echocardiographic examinations. Respiratory exchange ratio and ventilatory equivalents ( V̇E / V̇O2 and V̇E / V̇CO2 ) were significantly elevated, V̇O2 and V̇O2 /HR were significantly lowered, and exercise-onset V̇O2 kinetics were significantly slower in AS patients vs. healthy controls (P < 0.05). Although the AVA was restored by mini-AVR in AS patients, V̇E / V̇O2 and V̇E / V̇CO2 further worsened significantly within 5 days after surgery, accompanied by elevations in Borg RPE, V̇E and RR, and lowered Vt . At 21 days after mini-AVR, exercise-onset V̇O2 kinetics further slowed significantly (P < 0.05). A decline in pulmonary function was observed early after mini-AVR surgery, which was followed by a decline in skeletal muscle function in the subsequent weeks of recovery. Therefore, a tailored rehabilitation programme should include training modalities for the respiratory and peripheral muscular system.

The role of omega-3 in the prevention and treatment of sarcopenia.

Sarcopenia is a geriatric syndrome with increasing importance due to the aging of the population. It is known to impose a major burden in terms of morbidity, mortality and socio-economic costs. Therefore, adequate preventive and treatment strategies are required. Progressive resistance training and protein supplementation are currently recommended for the prevention and treatment of sarcopenia. Omega-3 polyunsaturated fatty acids (PUFAs) might be an alternative therapeutic agent for sarcopenia due to their anti-inflammatory properties, which target the 'inflammaging', the age-related chronic low-grade inflammation which is assumed to contribute to the development of sarcopenia. In addition, omega-3 PUFAs may also have an anabolic effect on muscle through activation of the mTOR signaling and reduction of insulin resistance. This narrative review provides an overview of the current knowledge about omega-3 PUFAs and their role in the prevention and treatment of sarcopenia. We conclude that there is growing evidence for a beneficial effect of omega-3 PUFAs supplementation in sarcopenic older persons, which may add to the effect of exercise and/or protein supplementation. However, the exact dosage, frequency and use (alone or combined) in the treatment and prevention of sarcopenia still need further exploration.

Effect of Stacked Sodium Bicarbonate Loading on Repeated All-out Exercise.

The purpose of this study was to evaluate whether NaHCO3, administered via a 9-h stacked loading protocol (i.e. repeated supplementation with small doses in order to obtain a gradual increase in blood [HCO3 -]), has an ergogenic effect on repeated all-out exercise. Twelve physically active males were randomly assigned to receive either NaHCO3 (BIC) or placebo (PL) in a double-blind cross-over design. NaHCO3 supplementation was divided in three identical 3-h cycles: a 6.3 g bolus at the start, followed by 2.1 g doses at +1-h and +2-h, yielding a total NaHCO3 intake of 0.4 g·kg-1 BM over 9-h. At the end of each cycle, participants performed 2-min all-out cycling. Capillary blood samples were analyzed for [HCO3 -], pH and [La-]. Pre-exercise blood [HCO3 -] in PL decreased from 25.6±0.2 mmol·L-1 in bout 1 to 23.6±0.2 mmol·L-1 in bout 4, while increasing from 25.5±0.2 to 31.2±0.4 mmol·L-1 in BIC (P<0.05). Concomitantly, pre-exercise pH values gradually decreased in PL (from 7.41±0.00 to 7.39±0.01) and increased in BIC (from 7.41±0.01 to 7.47±0.01; P<0.05). Mean power output of the four bouts was higher in BIC (428±20 W) than in PL (420±20 W; P<0.05). The ergogenic effect on repeated all-out exercise occurred in the absence of gastrointestinal distress.

Endocannabinoid remodeling in murine cachexic muscle associates with catabolic and metabolic regulation.

Muscle degeneration is a common feature in cancer cachexia that cannot be reversed. Recent advances show that the endocannabinoid system, and more particularly cannabinoid receptor 1 (CB1), regulates muscle processes, including metabolism, anabolism and regenerative capacity. However, it is unclear whether muscle endocannabinoids, their receptors and enzymes are responsive to cachexia and exercise. Therefore, this study investigated whether cachexia and exercise affected muscle endocannabinoid signaling, and whether CB1 expression correlated with markers of muscle anabolism, catabolism and metabolism. Male BALB/c mice were injected with PBS (CON) or C26 colon carcinoma cells (C26) and had access to wheel running (VWR) or remained sedentary (n = 5-6/group). Mice were sacrificed 18 days upon PBS/tumor cell injection. Cachexic mice exhibited a lower muscle CB1 expression (-43 %; p < 0.001) and lower levels of the endocannabinoid anandamide (AEA; -22 %; p = 0.044), as well as a lower expression of the AEA-synthesizing enzyme NAPE-PLD (-37 %; p < 0.001), whereas the expression of the AEA degrading enzyme FAAH was higher (+160 %; p < 0.001). The 2-AG-degrading enzyme MAGL, was lower in cachexic muscle (-34 %; p = 0.007), but 2-AG and its synthetizing enzyme DAGLß were not different between CON and C26. VWR increased muscle CB1 (+25 %; p = 0.005) and increased MAGL expression (+30 %; p = 0.035). CB1 expression correlated with muscle mass, markers of metabolism (e.g. p-AMPK, PGC1α) and of catabolism (e.g. p-FOXO, LC3b, Atg5). Our findings depict an emerging role of the endocannabinoid system in muscle physiology. Future studies should elaborate how this translates into potential therapies to combat cancer cachexia, and other degenerative conditions.

Palmitoylethanolamide Does Not Affect Recovery from Exercise-Induced Muscle Damage in Healthy Males.

INTRODUCTION: Strenuous eccentric exercise (EE) induces microstructural muscle damage, which decreases muscle performance. Palmitoylethanolamide (PEA) exerts analgesic and anti-inflammatory effects in clinical pain conditions and preclinical models of experimentally induced-inflammation. This might hold clues for improved recovery from EE. Therefore, the current study evaluates the effect of PEA supplementation on functional and molecular responses to a single EE bout. METHODS: Eleven healthy male participants were included in a double-blind crossover study in which they received PEA (350 mg Levagen+) or placebo (maltodextrin) supplements, in a randomized order. In each experimental condition participants performed an acute bout of EE (24x10 eccentric contractions of the knee extensors on an isokinetic dynamometer). At baseline, 24 (D1), 48 (D2), 72 (D3) and 120 h (D5) following EE, maximal voluntary contraction and jump height were measured. Blood samples were collected at baseline and on D1-D5, and muscle biopsies were collected at baseline and on D2. Perceived muscle soreness, sleep quality and food intake were recorded daily. RESULTS: Muscle strength and jump height decreased following EE (up to ~40 and ~ 17% respectively; Ptime < 0.05) in both conditions. This drop was accompanied by an increase in plasma creatine kinase and perceived muscle soreness (Ptime < 0.05). Furthermore, EE, but not PEA, increased the expression of the myogenic marker Pax7 and of the catabolic markers p-FoxO1-3a, p62 and LC3BII/I (Ptime < 0.05). CONCLUSIONS: PEA supplementation does not improve muscle soreness, muscle strength and jump performance following a single EE bout. Additionally, PEA supplementation had no effect on local or systemic markers of muscle damage, catabolism or regeneration.

The cannabinoid receptor 1 antagonist AM6545 stimulates the Akt-mTOR axis and in vivo muscle protein synthesis in a dexamethasone-induced muscle atrophy model.

Cannabinoid receptor 1 (CB1) antagonists were shown to stimulate in vitro muscle protein synthesis, but this has never been confirmed in vivo. Therefore, this study investigated whether treatment with the CB1 antagonist AM6545 upregulates in vivo muscle anabolism. Chronic AM6545 treatment stimulated the Akt-mTOR axis and protein synthesis (+22%; p = 0.002) in the Tibialis Anterior, which protected mice from dexamethasone-induced muscle loss (-1% vs. -6% compared to healthy controls; p = 0.02). Accordingly, acute AM6545 treatment stimulated protein synthesis (+44%; p = 0.04) in the Tibialis Anterior but not Soleus. The anabolic upregulation was accompanied by ERK1/2 activation, whereas protein kinase A signaling remained unaffected, suggesting a CB1-independent mechanism. The present study for the first time shows that the CB1 antagonist AM6545 can upregulate the Akt-mTOR axis and in vivo muscle protein synthesis. However, future work applying genetic approaches should further uncover the signaling pathways via which AM6545 enhances muscle anabolism.

Cannabidiol and brain function: current knowledge and future perspectives.

Cannabidiol (CBD) is a naturally occurring non-psychoactive cannabinoid found in Cannabis sativa, commonly known as cannabis or hemp. Although currently available CBD products do not meet the safety standards of most food safety authorities to be approved as a dietary supplement or food additive, CBD has been gaining widespread attention in recent years due to its various potential health benefits. While primarily known for its therapeutic effects in managing epileptic seizures, psychosis, anxiety, (neuropathic) pain, and inflammation, CBD's influence on brain function has also piqued the interest of researchers and individuals seeking to enhance cognitive performance. The primary objective of this review is to gather, synthesize, and consolidate scientifically proven evidence on the impact of CBD on brain function and its therapeutic significance in treating neurological and mental disorders. First, basic background information on CBD, including its biomolecular properties and mechanisms of action is presented. Next, evidence for CBD effects in the human brain is provided followed by a discussion on the potential implications of CBD as a neurotherapeutic agent. The potential effectiveness of CBD in reducing chronic pain is considered but also in reducing the symptoms of various brain disorders such as epilepsy, Alzheimer's, Huntington's and Parkinson's disease. Additionally, the implications of using CBD to manage psychiatric conditions such as psychosis, anxiety and fear, depression, and substance use disorders are explored. An overview of the beneficial effects of CBD on aspects of human behavior, such as sleep, motor control, cognition and memory, is then provided. As CBD products remain largely unregulated, it is crucial to address the ethical concerns associated with their use, including product quality, consistency, and safety. Therefore, this review discusses the need for responsible research and regulation of CBD to ensure its safety and efficacy as a therapeutic agent for brain disorders or to stimulate behavioral and cognitive abilities of healthy individuals.

Prolonged mechanical muscle loading increases mechanosensor gene and protein levels and causes a moderate fast-to-slow fiber type switch in mice.

Mechanosensing and subsequent mechanotransduction are indispensable for muscle plasticity. Nevertheless, a scarcity of literature exists regarding an all-encompassing understanding of the muscle mechanosensing machinery's response to prolonged loading, especially in conditions that resemble a natural physiological state of skeletal muscle. This study aimed to comprehensively explore the effects of prolonged mechanical loading on mechanosensitive components, skeletal muscle characteristics, and metabolism-related gene clusters. Twenty male C57BL/6J mice were randomly divided into two groups: control and prolonged mechanical loading. To induce prolonged mechanical loading on the triceps brachii (TRI) and biceps brachii (BIC) muscles, a 14-day period of tail suspension was implemented. In TRI only, prolonged mechanical loading caused a mild fast-to-slow fiber type shift together with increased mechanosensor gene and protein levels. It also increased transcription factors associated with slow muscle fibers while decreasing those related to fast-type muscle gene expression. Succinate dehydrogenase activity, a marker of muscle oxidative capacity, and genes involved in oxidative and mitochondrial turnover increased, whereas glycolytic-related genes decreased. Moreover, prolonged mechanical loading stimulated markers of muscle protein synthesis. Taken together, our data show a collective muscle-specific increase in mechanosensor gene and protein levels upon a period of prolonged mechanical loading in conditions that reflect a more natural physiological state of skeletal muscle in mice. We provide additional proof-of-concept that prolonged tail suspension-induced loading of the forelimbs triggers a muscle-specific fast-to-slow fiber type switch, and this coincides with increased protein synthesis-related signaling.NEW & NOTEWORTHY This study provides a comprehensive overview of the effects of prolonged loading on mechanosensitive components in conditions that better reflect the natural physiological state of skeletal muscle. Although the muscle mechanosensing machinery has been widely acknowledged for its responsiveness to altered loading, an inclusive understanding of its response to prolonged loading remains scarce. Our results show a fast-to-slow fiber type shift and an upregulation of mechanosensor gene and protein levels following prolonged loading.

Regulation of the endocannabinoid system by endurance and resistance exercise in hypoxia in human skeletal muscle.

Exercise modulates the circulating levels of the endocannabinoids ligands N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG) and possibly the levels of their receptors and downstream signaling in skeletal muscle. The aim of the present study was to investigate the regulation of the endocannabinoid system by several exercise paradigms in human skeletal muscle. A second aim was to compare endocannabinoid regulation in healthy and prediabetic people in response to an acute endurance exercise. Blood and muscle samples were taken before and after resistance and endurance exercise in normoxia and hypoxia to measure plasma endocannabinoid levels as well as muscle protein expression of CB1, CB2, and downstream signaling. We found that: 1) an acute resistance exercise session decreased plasma 2-AG and N-palmitoylethanolamine (PEA) levels in normoxia; 2) 4 wk resistance training decreased plasma AEA, PEA, and N-oleoylethanolamine (OEA) levels in both normoxia and hypoxia; 3) an acute moderate-intensity endurance exercise increased plasma OEA levels in the healthy and prediabetic groups in normoxia and hypoxia, whereas plasma 2-AG levels increased in the healthy group and AEA in the prediabetic group only in normoxia. The expression of the cannabinoid receptors was only marginally regulated by acute exercise, hypoxia, and prediabetes and downstream signaling did not follow the changes detected in the endocannabinoid ligands. Altogether, our results suggest that resistance and endurance exercise regulate the levels of the endocannabinoid ligands and CB1 expression in opposite ways. The physiological impact of the changes observed in the endocannabinoid ligands in human skeletal muscle after exercise needs further investigation.NEW & NOTEWORTHY We are the first to analyze both endocannabinoids ligands and receptors in response to endurance and resistance exercise. In addition, no study before has compared both exercise paradigms regarding endocannabinoid tone, which is of interest as endocannabinoids regulate energy metabolism, and these are different between endurance and resistance exercise. Furthermore, we investigated whether the endocannabinoid tone was differently regulated in response to acute endurance exercise in prediabetic people. Linking exercise, endocannabinoids and (pre)diabetic people has never been done before.