Intramuscular Signaling Research Articles

Effects of preconditioning with heat stress on acute exercise-induced intracellular signaling in male rat gastrocnemius muscle.

Heat stress (HS) induces Akt/mTOR phosphorylation and FoxO3a signaling; however, whether a prior increase in heat shock protein 72 (HSP72) expression affects intracellular signaling following eccentric exercise remains unclear. We analyzed the effects of HS pretreatment on intramuscular signaling in response to acute exercise in 10-week-old male Wistar rats (n = 24). One leg of each rat was exposed to HS and the other served as an internal control (CT). Post-HS, rats were either rested or subjected to downhill treadmill running. Intramuscular signaling responses in the red and white regions of the gastrocnemius muscle were analyzed before, immediately after, or 1 h after exercise (n = 8/group). HS significantly increased HSP72 levels in both deep red and superficial white regions. Although HS did not affect exercise-induced mTOR signaling (S6K1/ERK) responses in the red region, mTOR phosphorylation in the white region was significantly higher in CT legs than in HS legs after exercise. Thr308 phosphorylation of Akt showed region-specific alteration with a decrease in the red region and an increase in the white region immediately after downhill running. Overall, a prior increase in HSP72 expression elicits fiber type-specific changes in exercise-induced Akt and mTOR phosphorylation in rat gastrocnemius muscle.

Pre-heating stress associated with acute oral leucine supplementation effects in rat gastrocnemius muscle: Implications for protein synthesis signaling pathways

Skeletal muscle is a highly plastic tissue. The role of heat shock protein 72 (Hsp72) in heat stress-induced skeletal muscle hypertrophy has been well demonstrated; however, the precise mechanisms remain unclear. Essential amino acids, such as leucine, mainly mediate muscle protein synthesis. We investigated the effects of pre-heating and increased Hsp72 expression on the mechanistic target of rapamycin (mTOR) signaling and protein synthesis following leucine administration in rat gastrocnemius muscle. To ensure increased Hsp72 expression in both the red and white portions of the muscle, one leg of male Wistar rats (10-week-old, n = 23) was heat-stressed in 43 °C water for 30 min twice at a 48-h-interval (heat-stressed leg, HS leg). The contralateral leg served as a non-heated internal control (CT leg). After the recovery period (48 h), rats were divided into the pre-administration or oral leucine administration groups. We harvested the gastrocnemius muscle (red and white parts) prior to administration and 30 and 90 min after leucine treatment (n = 7–8 per group) and intramuscular signaling responses to leucine ingestion were determined using western blotting. Heat stress significantly upregulated the expression of Hsp72 and was not altered by leucine administration. Although the phosphorylation levels of mTOR/S6K1 and ERK were similar regardless of heating, 4E-BP1 was less phosphorylated in the HS legs than the CT legs after leucine administration in the red portion of the muscles (P < 0.05). Moreover, c-Myc expression differed significantly after leucine administration in both the red and white portions of the muscles. Our findings indicate that following oral leucine administration, pre-heating partially blunted the muscle protein synthesis signaling response in the rat gastrocnemius muscle.

Effects of Low-Load, High-Repetition Resistance Training on Maximum Muscle Strength and Muscle Damage in Elite Weightlifters: A Preliminary Study

This study aimed to assess the impact of different resistance training (RT) loads and repetition on muscle damage, intramuscular anabolic signaling, and maximal muscle strength (MMS) in weightlifters. Eighteen male weightlifters were randomly assigned to 8 weeks of supervised RT regimes: high-load, low-repetition (HL), low-load, high-repetition (LH), and combination of HL and LH (COMBI). All groups exhibited a significant increase in skeletal muscle mass (SMM) and growth hormone levels, which ultimately contributed to improvement in MMS as indicated by 1-repetition maximum in the back squat and back muscle strength. Notably, while there were no significant changes in the mTOR protein, the phosphorylation of phosphorylation of p70 ribosomal protein S6 kinase 1 (p70S6K1), eukaryotic initiation factor 4E-binding protein 1 (4E-BP1), and eukaryotic elongation factor 2 (eEF2), which are involved in muscle cell growth, was significantly affected by the different training regimens. More importantly, LH-RT led to a significant reduction in muscle damage markers, creatine kinase (CK) and lactate dehydrogenase (LDH), suggesting reduced recovery time and fatigue. Our results demonstrated that the LH-RT paradigm could be a viable alternative for weightlifters to enhance MMS and muscle hypertrophy similar to HL-RT, while reducing RT-induced muscle damage, ultimately contributing to the enhancement of exercise performance.

Role of prior feeding status in mediating the effects of exercise on blood glucose kinetics.

Changes in blood glucose concentrations are underpinned by blood glucose kinetics (endogenous and exogenous glucose appearance rates and glucose disappearance rates). Exercise potently alters blood glucose kinetics and can thereby be used as a tool to control blood glucose concentration. However, most studies of exercise-induced changes in glucose kinetics are conducted in a fasted state, and therefore less is known about the effects of exercise on glucose kinetics when exercise is conducted in a postprandial state. Emerging evidence suggests that food intake prior to exercise can increase postprandial blood glucose flux compared with when meals are consumed after exercise, whereby both glucose appearance rates and disappearance rates are increased. The mechanisms underlying the mediating effect of exercise conducted in the fed versus the fasted state are yet to be fully elucidated. Current evidence demonstrates that exercise in the postprandial state increased glucose appearance rates due to both increased exogenous and endogenous appearance and may be due to changes in splanchnic blood flow, intestinal permeability, and/or hepatic glucose extraction. On the other hand, increased glucose disappearance rates after exercise in the fed state have been shown to be associated with increased intramuscular AMPK signaling via a mismatch between carbohydrate utilization and delivery. Due to differences in blood glucose kinetics and other physiological differences, studies conducted in the fasted state cannot be immediately translated to the fed state. Therefore, conducting studies in the fed state could improve the external validity of data pertaining to glucose kinetics and intramuscular signaling in response to nutrition and exercise.

ATIVAÇÃO DE CÉLULAS SATÉLITES E RESPOSTA NA VIA DE SINALIZAÇÃO NOS EXERCÍCIOS ARTICULARES DOS ATLETAS

ABSTRACT Introduction: Skeletal muscle satellite cells are considered the unique source of stem cells for myogenic differentiation of adult skeletal muscle cells. Upon stimulation, the skeletal muscle satellite cell can be activated through specific signaling pathways, proliferate and differentiate into a muscle cell. An analysis of the effects of key signaling pathways could provide the basis for an in-depth study of skeletal muscle formation in athletes and muscle development. Objective: This paper analyzes the effects of key signaling pathways on skeletal muscle satellite cell proliferation and differentiation. Methods: We divided 32 athletes into four groups: control, stretching, experimental, and mixed groups. The control group received no training at all, the stretching group and the experimental group received stretching training on the right gastrocnemius. The mixed group also got weight climbing training in the stretching training, initial load 30% of the athlete's weight, increasing 25% each week until 100% of body weight, at the frequency of 3 times a week. After training, gene expression of live satellite cells was measured by intramuscular signaling. Results: The FGM level of the antagonistic group (3.56±0.21) was higher than in the control group (3.25±0.18). The gene expression of HGF mRNA was higher in the mixed group (2.16±0.24) followed by the antagonistic group (2.02±0.15), the stretching group (1.81±0.25), and the control group (1.03±0.06). Conclusion: Both stretching and antagonistic training can increase gene expression in signaling pathways. Antagonistic training significantly increased the expression of HGF, MGF, and mRNA. This activity can promote muscle bulking and skeletal muscle enlargements. Evidence Level II; Therapeutic Studies - Investigating the result.

Insulin-like growth factor-I biocompartmentalization across blood, interstitial fluid and muscle, before and after 3 months of chronic resistance exercise.

This investigation examined the influence of 12-week ballistic resistance training programs on the IGF-I system in circulation, interstitial fluid, and skeletal muscle, at rest and in response to acute exercise. Seventeen college-aged subjects (11 women/6 men; 21.7 ± 3.7 yr) completed an acute ballistic exercise bout before and after the training program. Blood samples were collected pre-, mid-, and postexercise and analyzed for serum total IGF-I, free IGF-I, and IGF binding proteins (IGFBPs) 1-4. Dialysate and interstitial free IGF-I were analyzed in vastus lateralis (VL) interstitial fluid collected pre- and postexercise via microdialysis. Pre- and postexercise VL muscle biopsies were analyzed for IGF-I protein expression, IGF-I receptor phosphorylation (p-IGF-IR), and AKT phosphorylation (p-AKT). Following training, basal serum IGF-I, free IGF-I, IGFBP-2, and IGFBP-3 decreased whereas IGFBP-1 and IGFBP-4 increased. Training reduced basal dialysate and interstitial free IGF-I but had no effect on basal skeletal muscle IGF-I, p-IGF-IR, or p-AKT. Acute exercise elicited transient changes in IGF-I system concentrations and downstream anabolic signaling both pre- and posttraining; training did not affect this acute exercise response. Posttraining, acute exercise-induced changes in dialysate/interstitial free IGF-I were strongly correlated with the changes in intramuscular IGF-I expression, p-IGF-IR, and p-AKT. The divergent influence of resistance training on circulating/interstitial and skeletal muscle IGF-I demonstrates the importance of concurrent, multiple biocompartment analysis when examining the IGF-I system. As training elicited muscle hypertrophy, these findings indicate that IGF-I's anabolic effects on skeletal muscle are mediated by local, rather than systemic mechanisms.NEW & NOTEWORTHY In the first investigation to assess resistance training's effects on the IGF-I system in serum, interstitial fluid, and skeletal muscle, training decreased basal circulating and interstitial IGF-I but did not alter basal intramuscular IGF-I protein activity. Posttraining, acute exercise-induced interstitial IGF-I increases were strongly correlated with intramuscular IGF-I expression and signaling. These findings highlight the importance of multibiocompartment measurement when analyzing IGF-I and suggest that IGF-I's role in hypertrophic adaptations is locally mediated.

Glutamate metabolism directs energetic trade-offs to shape host-pathogen susceptibility in Drosophila

Individual hosts within populations often show inter-individual variation in their susceptibility to bacterial pathogen-related diseases. Utilizing Drosophila, we highlight that phenotypic variation in host-pathogen susceptibility within populations is driven by energetic trade-offs, facilitated by infection-mediated changes in glutamate metabolism. Furthermore, host-pathogen susceptibility is conditioned by life history, which adjusts immunometabolic sensing in muscles to direct vitamin-dependent reallocation of host energy substrates from the adipose tissue (i.e., a muscle-adipose tissue axis). Life history conditions inter-individual variation in the activation strength of intra-muscular NF-κB signaling. Limited intra-muscular NF-κB signaling activity allows for enhanced infection-mediated mitochondrial biogenesis and function, which stimulates glutamate dehydrogenase-dependent synthesis of glutamate. Muscle-derived glutamate acts as a systemic metabolite to promote lipid mobilization through modulating vitamin B enzymatic cofactor transport and function in the adipose tissue. This energy substrate reallocation improves pathogen clearance and boosts host survival. Finally, life history events that adjust energetic trade-offs can shape inter-individual variation in host-pathogen susceptibility after infection.

D-Allulose Ameliorates Skeletal Muscle Insulin Resistance in High-Fat Diet-Fed Rats.

Background: d-Allulose is a rare sugar with antiobesity and antidiabetic activities. However, its direct effect on insulin sensitivity and the underlying mechanism involved are unknown. Objective: This study aimed to investigate the effect of d-allulose on high-fat diet (HFD)-induced insulin resistance using the hyperinsulinemic–euglycemic (HE)-clamp method and intramuscular signaling analysis. Methods: Wistar rats were randomly divided into three dietary groups: chow diet, HFD with 5% cellulose (HFC), and HFD with 5% d-allulose (HFA). After four weeks of feeding, the insulin tolerance test (ITT), intraperitoneal glucose tolerance test (IPGTT), and HE-clamp study were performed. The levels of plasma leptin, adiponectin, and tumor necrosis factor (TNF)-α were measured using the enzyme-linked immunosorbent assay. We analyzed the levels of cell signaling pathway components in the skeletal muscle using Western blotting. Results: d-allulose alleviated the increase in HFD-induced body weight and visceral fat and reduced the area under the curve as per ITT and IPGTT. d-Allulose increased the glucose infusion rate in the two-step HE-clamp test. Consistently, the insulin-induced phosphorylation of serine 307 in the insulin receptor substrate-1 and Akt and expression of glucose transporter 4 (Glut-4) in the muscle were higher in the HFA group than HFC group. Furthermore, d-allulose decreased plasma TNF-α concentration and insulin-induced phosphorylation of stress-activated protein kinase/Jun N-terminal kinase in the muscle and inhibited adiponectin secretion in HFD-fed rats. Conclusions: d-allulose improved HFD-induced insulin resistance in Wistar rats. The reduction of the proinflammatory cytokine production, amelioration of adiponectin secretion, and increase in insulin signaling and Glut-4 expression in the muscle contributed to this effect.

Understanding the effects of nutrition and post-exercise nutrition on skeletal muscle protein turnover: Insights from stable isotope studies

Understanding the effects of nutrition and post-exercise nutrition on skeletal muscle protein turnover: Insights from stable isotope studies

Evidence for the Contribution of Gut Microbiota to Age-Related Anabolic Resistance.

Globally, people 65 years of age and older are the fastest growing segment of the population. Physiological manifestations of the aging process include undesirable changes in body composition, declines in cardiorespiratory fitness, and reductions in skeletal muscle size and function (i.e., sarcopenia) that are independently associated with mortality. Decrements in muscle protein synthetic responses to anabolic stimuli (i.e., anabolic resistance), such as protein feeding or physical activity, are highly characteristic of the aging skeletal muscle phenotype and play a fundamental role in the development of sarcopenia. A more definitive understanding of the mechanisms underlying this age-associated reduction in anabolic responsiveness will help to guide promyogenic and function promoting therapies. Recent studies have provided evidence in support of a bidirectional gut-muscle axis with implications for aging muscle health. This review will examine how age-related changes in gut microbiota composition may impact anabolic response to protein feeding through adverse changes in protein digestion and amino acid absorption, circulating amino acid availability, anabolic hormone production and responsiveness, and intramuscular anabolic signaling. We conclude by reviewing literature describing lifestyle habits suspected to contribute to age-related changes in the microbiome with the goal of identifying evidence-informed strategies to preserve microbial homeostasis, anabolic sensitivity, and skeletal muscle with advancing age.

Does the Nutritional Composition of Dairy Milk Based Recovery Beverages Influence Post-exercise Gastrointestinal and Immune Status, and Subsequent Markers of Recovery Optimisation in Response to High Intensity Interval Exercise?

This study aimed to determine the effects of flavored dairy milk based recovery beverages of different nutrition compositions on markers of gastrointestinal and immune status, and subsequent recovery optimisation markers. After completing 2 h high intensity interval running, participants (n = 9) consumed a whole food dairy milk recovery beverage (CM, 1.2 g/kg body mass (BM) carbohydrate and 0.4 g/kg BM protein) or a dairy milk based supplement beverage (MBSB, 2.2 g/kg BM carbohydrate and 0.8 g/kg BM protein) in a randomized crossover design. Venous blood samples, body mass, body water, and breath samples were collected, and gastrointestinal symptoms (GIS) were measured, pre- and post-exercise, and during recovery. Muscle biopsies were performed at 0 and 2 h of recovery. The following morning, participants returned to the laboratory to assess performance outcomes. In the recovery period, carbohydrate malabsorption (breath H2 peak: 49 vs. 24 ppm) occurred on MBSB compared to CM, with a trend toward greater gut discomfort. No difference in gastrointestinal integrity (i.e., I-FABP and sCD14) or immune response (i.e., circulating leukocyte trafficking, bacterially-stimulated neutrophil degranulation, and systemic inflammatory profile) markers were observed between CM and MBSB. Neither trial achieved a positive rate of muscle glycogen resynthesis [−25.8 (35.5) mmol/kg dw/h]. Both trials increased phosphorylation of intramuscular signaling proteins. Greater fluid retention (total body water: 86.9 vs. 81.9%) occurred on MBSB compared to CM. Performance outcomes did not differ between trials. The greater nutrient composition of MBSB induced greater gastrointestinal functional disturbance, did not prevent the post-exercise reduction in neutrophil function, and did not support greater overall acute recovery.

The effects of dietary heat-killed probiotics bacteria additives in low-fishmeal feed on growth performance, immune responses, and intestinal morphology in juvenile olive flounder Paralichthys olivaceus

Fishmeal is an important source of protein in the fish diet, but its supply is unstable due to environmental pollution and overfishing of anchovy and herring. In addition, the disease outbreak of fish has been increased, and the abuse of antibiotics and vaccines has been becoming a problem for residual substances. Therefore, studies that address diets with reduced fishmeal content and additives that can increase efficiency and replace antibiotics are needed. Hence, in this study, the probiotics bacteria Bacillus sp. SJ-10 (BSJ-10) and Lactobacillus plantarum (LP) were heat-killed (HK) used as additives in a low-fishmeal diet. The two bacteria with a 45 % fishmeal diet were added at a concentration of 3.34 × 108 CFU/mL, and both of probiotics bacteria were mixed and added to the same concentration in order to produce the diet for HK BSJ-10 (HKBSJ-10), HK LP (HK-LP), and MIX (HKBSJ-10 + HK-LP) groups. We raised four replicates of juvenile olive flounder for 8 weeks. In the HKBSJ-10 group, the plasma insulin, GH, and IGF-I level were higher than the other groups (P < 0.05). Similarly, intramuscular IGF-I activity and signaling pathway were higher in HKBSJ-10 (P < 0.05). The innate immunity lysosome activity was higher in the HKBSJ-10 and MIX groups (P < 0.05), even cholecystokinin manifestation, intestinal wall thickness, and the density of the intestinal folds more evolved in the HKBSJ-10 group. Therefore, the HKBSJ-10 additive could be advanced in growth-related endocrine, innate immunity, and intestinal morphology, positively affecting a low-fishmeal diet for juvenile olive flounder.

The Effects of a Protease Enzyme Blend on Post-Resistance Exercise Intramuscular Anabolic Signaling

Abstract Objectives Protease supplementation has been reported to decrease inflammation and indices of muscle damage while increasing functional recovery following strenuous resistance exercise compared to a placebo. While various mechanisms have been proposed, the effects of protease supplementation on the resistance exercise induced anabolic signaling response has not been reported in the literature. To examine the effects of a protease enzyme blend added to whey protein on post-resistance exercise intramuscular anabolic signaling. Methods Ten resistance-trained males (24.4 ± 4.1yrs, 1.79 ± 0.86 m, 92.6 ± 10.4 kg) were enrolled in this double-blind, cross-over, placebo controlled study and engaged in three separate bouts of resistance exercise. Each participant completed 4 sets of leg presses and leg extensions for 8–10 repetitions at 75% of their 1-repetition maximum with 90 seconds of rest between each set. Immediately following the resistance exercise protocol, participants consumed either 250 mg of a protease enzyme blend + 26 g of whey protein (PW), 26 g whey alone (W), or non-caloric control (CON) in a counterbalanced fashion. Skeletal muscle microbiopsies were obtained from the vastus lateralis pre-exercise (PRE), 1-hour (1H), and 3-hours (3H) post-exercise. Multiplex signaling assay kits were used to quantify the phosphorylation status of proteins specific to the mTOR (AKT, mTOR, p70S6K) and MAPK (ERK1/2, JNK, p38) signaling pathways using the MAGPIX® (Luminex, Austin, TX, USA). A 2-way repeated measures analysis of variance (ANOVA) was used to identify differences between treatments over time. Results A main effect for time (p &amp;lt; 0.05) revealed phosphorylation of AKT was decreased at 1H (p &amp;lt; 0.001), mTOR was increased at 1H (P = 0.025) and 3H (P = 0.009) post-exercise, while p70S6K remained unchanged (P &amp;gt; 0.05) from PRE. A main effect for time (p &amp;lt; 0.05) was found with increased phosphorylation at 1H for JNK (P = 0.001), and decreased phosphorylation at 3H for ERK 1/2 (P = 0.022) with respect to baseline. Additionally, there were no differences in any mTOR nor MAPK signaling proteins observed between treatments. Conclusions These data suggest that acute protease supplementation may not alter mTOR or MAPK signaling in skeletal muscle following acute resistance exercise. Funding Sources Deerland Enzymes, Kennesaw, GA.

Redox Signaling in Widespread Health Benefits of Exercise.

Significance: Exercise-induced reactive oxygen species (ROS) production activates multiple intracellular signaling pathways through genomic and nongenomic mechanisms that are responsible for the beneficial effects of exercise in muscle. Beyond the positive effect of exercise on skeletal muscle cells, other tissues such as white and brown adipose, liver, central nervous system, endothelial, heart, and endocrine organ tissues are also responsive to exercise. Recent Advances: Crosstalk between different cells is essential to achieve homeostasis and to promote the benefits of exercise through paracrine or endocrine signaling. This crosstalk can be mediated by different effectors that include the secretion of metabolites of muscle contraction, myokines, and exosomes. During the past 20 years, it has been demonstrated that contracting muscle cells produce and secrete different classes of myokines, which functionally link muscle with nearly all other cell types. Critical Issues: The redox signaling behind this exercise-induced crosstalk is now being decoded. Many of these widespread beneficial effects of exercise require not only a complex ROS-dependent intramuscular signaling cascade but simultaneously, an integrated network with many remote tissues. Future Directions: Strong evidence suggests that the powerful beneficial effect of regular physical activity for preventing (or treating) a large range of disorders might also rely on ROS-mediated signaling. Within a contracting muscle, ROS signaling may control exosomes and myokines secretion. In remote tissues, exercise generates regular and synchronized ROS waves, creating a transient pro-oxidative environment in many cells. These new concepts integrate exercise, ROS-mediated signaling, and the widespread health benefits of exercise.

Divergent Roles of Inflammation in Skeletal Muscle Recovery From Injury.

A transient increase in local pro-inflammatory cytokine expression following skeletal muscle injury mediates the repair and regeneration of damaged myofibers through myogenesis. Regenerative capacity is diminished and muscle wasting occurs, however, when intramuscular inflammatory signaling is exceedingly high or persists chronically. An excessive and persistent inflammatory response to muscle injury may therefore impair recovery by limiting the repair of damaged tissue and triggering muscle atrophy. The concentration-dependent activation of different downstream signaling pathways by several pro-inflammatory cytokines in cell and animal models support these opposing roles of post-injury inflammation. Understanding these molecular pathways is essential in developing therapeutic strategies to attenuate excessive inflammation and accelerate functional recovery and muscle mass accretion following muscle damage. This is especially relevant given the observation that basal levels of intramuscular inflammation and the inflammatory response to muscle damage are not uniform across all populations, suggesting certain individuals may be more susceptible to an excessive inflammatory response to injury that limits recovery. This narrative review explores the opposing roles of intramuscular inflammation in muscle regeneration and muscle protein turnover. Factors contributing to an exceedingly high inflammatory response to damage and age-related impairments in regenerative capacity are also considered.

The Effect of ProHydrolase® on the Amino Acid and Intramuscular Anabolic Signaling Response to Resistance Exercise in Trained Males

This double-blind study examined effects of a protease enzyme blend (Prohydrolase®) added to whey protein on post-resistance exercise aminoacidemia and intramuscular anabolic signaling were investigated in ten resistance-trained males. Participants completed 4 sets of 8–10 repetitions in the leg press and leg extension exercises at 75% of 1-repetition maximum. Participants then consumed either 250 mg of Prohydrolase® + 26 g of whey protein (PW), 26 g whey alone (W), or non-nutritive control (CON) in counterbalanced order. Blood samples were obtained prior to exercise (baseline) and then immediately-post (IP), 30-, 60-, 90-, 120-, and 180-min post-exercise. Muscle biopsies were taken at baseline, 1-h (1H), and 3-h (3H) post-exercise. Phosphorylation of AKTSer437 was decreased (3H only: p < 0.001), mTORSer2448 was increased (1H: p = 0.025; 3H: p = 0.009), and p70S6KThr412 remained unchanged similarly for each condition. Plasma leucine, branch-chained amino acids, and essential amino acid concentrations for PW were significantly higher than CON (p < 0.05) at 30 min and similar to W. Compared to IP, PW was the only treatment with elevated plasma leucine levels at 30 min (p = 0.007; ∆ = 57.8 mmol/L, 95% Confidence Interval (CI): 20.0, 95.6) and EAA levels at 180 min (p = 0.003; ∆ = 179.1 mmol/L, 95% CI: 77.5, 280.7). Area under the curve amino acid analysis revealed no differences between PW and W. While no different than W, these data indicate that PW was the only group to produce elevated amino acid concentrations 30-min and 180-min post-ingestion.

Sex-specific differences in rat soleus muscle signaling pathway responses to a bout of horizontal and downhill running

Males and females of many species, including humans, exhibit different muscle responses and adaptations to exercise stress; however, the molecular mechanisms that underlie these changes are poorly understood. Therefore, the present study assessed sex-related differences in intracellular signaling pathway responses to bouts of horizontal or downhill running in rat soleus muscles. Age-matched male and female Wistar rats (10 weeks old, n = 18/group) were either rested (control group) or subjected to an either a bout of horizontal (22 m/min, 20 min, 0° incline) or downhill (16 m/min, 10 min, - 16% incline) treadmill running. Soleus muscle samples were collected both prior to and immediately after exercise (n = 6/group). Intramuscular signaling responses to each type of exercise were determined via real-time (RT) PCR and western blot analyses. Although mTOR signaling (mTOR/S6K1/S6) responses to both horizontal and downhill exercise were found to be similar in both sexes, ERK phosphorylation levels were found to be significantly higher in male than in female rats after downhill exercise. Similarly, heat shock protein (Hsp) 72 and myostatin protein expression levels were both found to be significantly altered after downhill exercise: Hsp levels increased in male and decreased in female rats, whereas myostatin increased in female but decreased in male rats. Thus, the results of the present study suggest that downhill exercise may elicit sex-specific differential changes to Hsp72 expression, ERK phosphorylation, and myostatin-signaling activation in female compared with those in male rat soleus muscles. Further study is required to confirm these findings and to determine the way in which they impact sex-specific differences in exercise-induced muscle adaptations.

The Effect of ProHydrolase® on the Amino Acid, Intramuscular Anabolic Signaling, and Endocrine Response to Resistance Exercise in Trained Males

The Effect of ProHydrolase® on the Amino Acid, Intramuscular Anabolic Signaling, and Endocrine Response to Resistance Exercise in Trained Males

Comparable Rates of Integrated Myofibrillar Protein Synthesis Between Endurance-Trained Master Athletes and Untrained Older Individuals.

BackgroundAn impaired muscle anabolic response to exercise and protein nutrition is thought to underpin age-related muscle loss, which may be exacerbated by aspects of biological aging that may not be present in older individuals who have undertaken long-term high-level exercise training, or master athletes (MA). The aim of this study was to compare rested-state and exercise-induced rates of integrated myofibrillar protein synthesis (iMyoPS) and intracellular signaling in endurance trained MA and healthy age-matched untrained individuals (Older Controls).MethodsIn a parallel study design, iMyoPS rates were determined over 48 h in the rested-state and following a bout of unaccustomed resistance exercise (RE) in OC (n = 8 males; 73.5 ± 3.3 years) and endurance-trained MA (n = 7 males; 68.9 ± 5.7 years). Intramuscular anabolic signaling was also determined. During the iMyoPS measurement period, physical activity was monitored via accelerometry and dietary intake was controlled.ResultsAnthropometrics, habitual activity, and dietary intake were similar between groups. There was no difference in rested-state rates of iMyoPS between OC (1.47 ± 0.06%⋅day–1) and MA (1.46 ± 0.08%⋅day–1). RE significantly increased iMyoPS above rest in both OC (1.60 ± 0.08%⋅day–1, P < 0.01) and MA (1.61 ± 0.08%⋅day–1, P < 0.01), with no difference between groups. AktThr308 phosphorylation increased at 1 h post-RE in OC (P < 0.05), but not MA. No other between-group differences in intramuscular signaling were apparent at any time-point.ConclusionWhile our sample size is limited, these data suggest that rested-state and RE-induced iMyoPS are indistinguishable between MA and OC. Importantly, the OC retain a capacity for RE-induced stimulation of skeletal muscle remodeling.

Dataset for 'Pre-Exercise Breakfast Ingestion versus Extended Overnight Fasting Increases Postprandial Glucose Flux after Exercise in Healthy Men: Pre-exercise feeding and postprandial glucose flux'

The aim of this study was to characterise postprandial glucose flux after exercise in the fed versus overnight fasted-state and to investigate potential underlying mechanisms. In a randomized order, twelve men underwent breakfast-rest (BR; 3 h semi-recumbent), breakfast-exercise (BE; 2 h semi-recumbent before 60-min of cycling (50% peak power output) and overnight fasted-exercise (FE; as per BE omitting breakfast) trials. An oral glucose tolerance test (OGTT) was completed post-exercise (post-rest on BR). Dual stable isotope tracers ([U-13C] glucose ingestion and [6,6-2H2] glucose infusion) and muscle biopsies were combined to assess postprandial plasma glucose kinetics and intramuscular signaling, respectively. Plasma intestinal fatty acid binding (I-FABP) concentrations were determined as a marker of intestinal damage. The results from this study showed that consuming breakfast before exercise increases post-exercise postprandial plasma glucose disposal, which is offset (primarily) by increased appearance rates of orally-ingested glucose. Therefore, metabolic responses to fed-state exercise cannot be readily inferred from studies conducted in a fasted state.