Nutrient provision increases signalling and protein synthesis in human skeletal muscle after repeated sprints

The effect of nutrient availability on the acute molecular responses following repeated sprint exercise is unknown. The aim of this study was to determine skeletal muscle cellular and protein synthetic responses following repeated sprint exercise with nutrient provision. Eight healthy young male subjects undertook two sprint cycling sessions (10 × 6 s, 0.75 N m torque kg -1, 54 s recovery) with either pre-exercise nutrient (24 g whey, 4.8 g leucine, 50 g maltodextrin) or non-caloric placebo ingestion. Muscle biopsies were taken from vastus lateralis at rest, and after 15 and 240 min post-exercise recovery to determine muscle cell signalling responses and protein synthesis by primed constant infusion of L-[ring- 13C 6] phenylalanine. Peak and mean power outputs were similar between nutrient and placebo trials. Post-exercise myofibrillar protein synthetic rate was greater with nutrient ingestion compared with placebo ( ? 48%, P<0.05) but the rate of mitochondrial protein synthesis was similar between treatments. The increased myofibrillar protein synthesis following sprints with nutrient ingestion was associated with coordinated increases in Akt-mTOR-S6KrpS6 phosphorylation 15 min post-exercise (?200-600%, P<0.05), while there was no effect on these signalling molecules when exercise was undertaken in the fasted state. For the first time we report a beneficial effect of nutrient provision on anabolic signalling and muscle myofibrillar protein synthesis following repeated sprint exercise. Ingestion of protein/carbohydrate in close proximity to high-intensity sprint exercise provides an environment that increases cell signalling and protein synthesis.

Contraction-induced changes in TNFα and Akt-mediated signalling are associated with increased myofibrillar protein in rat skeletal muscle

Resistance training results in skeletal muscle hypertrophy, but the molecular signalling mechanisms responsible for this altered phenotype are incompletely understood. We used a resistance training (RT) protocol consisting of three sessions [day 1 (d1), day 3 (d3), day 5 (d5)] separated by 48 h recovery (squat exercise, 4 sets × 10 repetitions, 3 min recovery) to determine early signalling responses to RT in rodent skeletal muscle. Six animals per group were killed 3 h after each resistance training session and 24 and 48 h after the last training session (d5). There was a robust increase in TNF? protein expression, and IKKSer180/181 and p38MAPK Thr180/Tyr182 phosphorylation on d1 (P < 0.05), which abated with subsequent RT, returning to control levels by d5 for TNF? and IKK Ser180/181. There was a trend for a decrease in MuRF-1 protein expression, 48 h following d5 of training (P = 0.08). Notably, muscle myofibrillar protein concentration was elevated compared to control 24 and 48 h following RT (P < 0.05). AktSer473 and mTORSer2448 phosphorylation were unchanged throughout RT. Phosphorylation of p70S6k Thr389 increased 3 h post-exercise on d1, d3 and d5 (P < 0.05), whilst phosphorylation of S6Ser235/236 increased on d1 and d3 (P < 0.05). Our results show a rapid attenuation of inflammatory signalling with repeated bouts of resistance exercise, concomitant with summation in translation initiation signalling in skeletal muscle. Indeed, the cumulative effect of these signalling events was associated with myofibrillar protein accretion, which likely contributes to the early adaptations in response to resistance training overload in the skeletal muscle.

Effect of consecutive repeated sprint and resistance exercise bouts on acute adaptive responses in human skeletal muscle

We examined acute molecular responses in skeletal muscle to repeated sprint and resistance exercise bouts. Six men [age, 24.7 ± 6.3 yr; body mass, 81.6 ± 7.3 kg; peak oxygen uptake, 47 ± 9.9 ml·kg -1 ·min -1; one repetition maximum (1-RM) leg extension 92.2 ± 12.5 kg; means ± SD] were randomly assigned to trials consisting of either resistance exercise (8 × 5 leg extension, 80% 1-RM) followed by repeated sprints (10 × 6 s, 0.75 N·m torque·kg -1) or vice-versa. Muscle biopsies from vastus lateralis were obtained at rest, 15 min after each exercise bout, and following 3-h recovery to determine early signaling and mRNA responses. There was divergent exercise order-dependent phosphorylation of p70 S6K (S6K). Specifically, initial resistance exercise increased S6K phosphorylation (?75% P < 0.05), but there was no effect when resistance exercise was undertaken after sprints. Exercise decreased IGF-I mRNA following 3-h recovery (?50%, P = 0.06) independent of order, while muscle RING finger mRNA was elevated with a moderate exercise order effect (P < 0.01). When resistance exercise was followed by repeated sprints PGC-1? mRNA was increased (REX1-SPR2; P = 0.02) with a modest distinction between exercise orders. Repeated sprints may promote acute interference on resistance exercise responses by attenuating translation initiation signaling and exacerbating ubiquitin ligase expression. Indeed, repeated sprints appear to generate the overriding acute exercise-induced response when undertaking concurrent repeated sprint and resistance exercise. Accordingly, we suggest that sprint-activities are isolated from resistance training and that adequate recovery time is considered within periodized training plans that incorporate these divergent exercise modes.

mTOR function in skeletal muscle : a focal point for overnutrition and exercise

The mammalian target of rapamycin (mTOR) is a highly conserved atypical serine-threonine kinase that controls numerous functions essential for cell homeostasis and adaptation in mammalian cells via 2 distinct protein complex formations. Moreover, mTOR is a key regulatory protein in the insulin signalling cascade and has also been characterized as an insulin-independent nutrient sensor that may represent a critical mediator in obesity-related impairments of insulin action in skeletal muscle. Exercise characterizes a remedial modality that enhances mTOR activity and subsequently promotes beneficial metabolic adaptation in skeletal muscle. Thus, the metabolic effects of nutrients and exercise have the capacity to converge at the mTOR protein complexes and subsequently modify mTOR function. Accordingly, the aim of the present review is to highlight the role of mTOR in the regulation of insulin action in response to overnutrition and the capacity for exercise to enhance mTOR activity in skeletal muscle.

Consecutive bouts of diverse contractile activity alter acute responses in human skeletal muscle

We examined acute molecular responses in skeletal muscle to divergent exercise stimuli by combining consecutive bouts of resistance and endurance exercise. Eight men [22.9 ± 6.3 yr, body mass of 73.2 ± 4.5 kg, peak O2 uptake (V?O2peak) of 54.0 ± 5.7 ml·kg-1·min-1] were randomly assigned to complete trials consisting of either resistance exercise (8 x 5 leg extension, 80% 1 repetition maximum) followed by a bout of endurance exercise (30 min cycling, 70% V?O2peak) or vice versa. Muscle biopsies were obtained from the vastus lateralis at rest, 15 min after each exercise bout, and after 3 h of passive recovery to determine early signaling and mRNA responses. Phosphorylation of Akt and Akt1Ser473 were elevated 15 min after resistance exercise compared with cycling, with the greatest increase observed when resistance exercise followed cycling (?55%; P < 0.01). TSC2-mTOR-S6 kinase phosphorylation 15 min after each bout of exercise was similar regardless of the exercise mode. The cumulative effect of combined exercise resulted in disparate mRNA responses. IGF-I mRNA content was reduced when cycling preceded resistance exercise (-42%), whereas muscle ring finger mRNA was elevated when cycling was undertaken after resistance exercise (?52%; P < 0.05). The hexokinase II mRNA level was higher after resistance cycling (?45%; P < 0.05) than after cycling-resistance exercise, whereas modest increases in peroxisome proliferator-activated receptor gamma coactivator-1? mRNA did not reveal an order effect. We conclude that acute responses to diverse bouts of contractile activity are modified by the exercise order. Moreover, undertaking divergent exercise in close proximity influences the acute molecular profile and likely exacerbates acute "interference".

Global gene expression in skeletal muscle from well-trained strength and endurance athletes

PURPOSE: We used gene microarray analysis to compare the global expression profile of genes involved in adaptation to training in skeletal muscle from chronically strength-trained (ST), endurance-trained (ET), and untrained control subjects (Con). METHODS: Resting skeletal muscle samples were obtained from the vastus lateralis of 20 subjects (Con n = 7, ET n = 7, ST n = 6; trained [TR] groups >8 yr specific training). Total RNA was extracted from tissue for two color microarray analysis and quantative (Q)-PCR. Trained subjects were characterized by performance measures of peak oxygen uptake V?O 2peak) on a cycle ergometer and maximal concentric and eccentric leg strength on an isokinetic dynamometer. RESULTS: Two hundred and sixty-three genes were differentially expressed in trained subjects (ET + ST) compared with Con (P < 0.05), whereas 21 genes were different between ST and ET (P < 0.05). These results were validated by reverse transcriptase polymerase chain reaction for six differentially regulated genes (EIFSJ, LDHB, LMO4, MDH1, SLC16A7, and UTRN. Manual cluster analyses revealed significant regulation of genes involved in muscle structure and development in TR subjects compared with Con (P < 0.05) and expression correlated with measures of performance (P < 0.05). ET had increased whereas ST had decreased expression of gene clusters related to mitochondrial/oxidative capacity (P ?‰Currency sign 0.05). These mitochondrial gene clusters correlated with V?O2peak (P < 0.05). V?O2peak also correlated with expression of gene clusters that regulate fat and carbohydrate oxidation (P < 0.05). CONCLUSION: We demonstrate that chronic training subtly coregulates numerous genes from important functional groups that may be part of the long-term adaptive process to adapt to repeated training stimuli.

High rates of muscle glycogen resynthesis after exhaustive exercise when carbohydrate is coingested with caffeine

We determined the effect of coingestion of caffeine (Caff) with carbohydrate (CHO) on rates of muscle glycogen resynthesis during recovery from exhaustive exercise in seven trained subjects who completed two experimental trials in a randomized, double-blind crossover design. The evening before an experiment subjects performed intermittent exhaustive cycling and then consumed a low-CHO meal. The next morning subjects rode until volitional fatigue. On completion of this ride subjects consumed either CHO [4 g/kg body mass (BM)] or the same amount of CHO + Caff (8 mg/kg BM) during 4 h of passive recovery. Muscle biopsies and blood samples were taken at regular intervals throughout recovery. Muscle glycogen levels were similar at exhaustion [?75 mmol/kg dry wt (dw)] and increased by a similar amount (?80%) after 1 h of recovery (133 ± 37.8 vs. 149 ± 48 mmol/kg dw for CHO and Caff, respectively). After 4 h of recovery Caff resulted in higher glycogen accumulation (313 ± 69 vs. 234 ± 50 mmol/kg dw, P < 0.001). Accordingly, the overall rate of resynthesis for the 4-h recovery period was 66% higher in Caff compared with CHO (57.7 ± 18.5 vs. 38.0 ± 7.7 mmol·kg dw-1·h-1, P < 0.05). After 1 h of recovery plasma Caff levels had increased to 31 ± 11 ?M (P < 0.001) and at the end of the recovery reached 77 ± 11 ?M (P < 0.001) with Caff. Phosphorylation of CaMKThr286 was similar after exercise and after 1 h of recovery, but after 4 h CaMKThr286 phosphorylation was higher in Caff than CHO (P < 0.05). Phosphorylation of AMP-activated protein kinase (AMPK)Thr172 and AktSer473 was similar for both treatments at all time points. We provide the first evidence that in trained subjects coingestion of large amounts of Caff (8 mg/kg BM) with CHO has an additive effect on rates of postexercise muscle glycogen accumulation compared with consumption of CHO alone.

Effect of high-frequency resistance exercise on adaptive responses in skeletal muscle

PURPOSE: Regulation of skeletal muscle mass is highly dependent on contractile loading. The purpose of this study was to examine changes in growth factor and inflammatory pathways following high-frequency resistance training. METHODS: Using a novel design in which male Sprague-Dawley rats undertook a "stacked" resistance training protocol designed to generate a summation of transient exercise-induced signaling responses (four bouts of three sets × 10 repetitions of squat exercise, separated by 3 h of recovery), we determined the effects of high training frequency on signaling pathways and transcriptional activity regulating muscle mass. RESULTS: The stacked training regimen resulted in acute suppression of insulin-like growth factor 1 mRNA abundance (P < 0.05) and Akt phosphorylation (P < 0.05), an effect that persisted 48 h after the final training bout. Conversely, stacked training elicited a coordinated increase in the expression of tumor necrosis factor alpha, inhibitor kappa B kinase alpha/beta activity (P < 0.05), and p38 mitogen-activated protein kinase phosphorylation (P < 0.05) at 3 h after each training bout. In addition, the stacked series of resistance exercise bouts induced an increase in p70 S6 kinase phosphorylation 3 h after bouts ×3 and ×4, independent of the phosphorylation state of Akt. CONCLUSIONS: Our results indicate that high resistance training frequency extends the transient activation of inflammatory signaling cascades, concomitant with persistent suppression of key mediators of anabolic responses. We provide novel insights into the effects of the timing of exercise-induced overload and recovery on signal transduction pathways and transcriptional activity regulating skeletal muscle mass in vivo.

Exercise-induced phosphorylation of the novel Akt substrates AS160 and filamin A in human skeletal muscle

Skeletal muscle contraction stimulates multiple signaling cascades that govern a variety of metabolic and transcriptional events. Akt/protein kinase B regulates metabolism and growth/muscle hypertrophy, but contraction effects on this target and its substrates are varied and may depend on the mode of the contractile stimulus. Accordingly, we determined the effects of endurance or resistance exercise on phosphorylation of Akt and downstream substrates in six trained cyclists who performed a single bout of endurance or resistance exercise separated by ?7 days. Muscle biopsies were taken from the vastus lateralis at rest and immediately after exercise. Akt Ser 473 phosphorylation was increased (1.8-fold; P = 0.011) after endurance but was unchanged after resistance exercise. Conversely, Akt Thr 308 phosphorylation was unaltered after either bout of exercise. Several exercise-responsive phosphoproteins were detected by immunoblot analysis with a phospho-Akt substrate antibody. pp160 and pp300 were identified as AS160 and filamin A, respectively, with increased phosphorylation (2.0- and 4.9-fold, respectively; P < 0.05) after endurance but not resistance exercise. In conclusion, AS160 and filamin A may provide an important link to mediate endurance exercise-induced bioeffects in skeletal muscle.

Failure to repeatedly supercompensate muscle glycogen stores in highly trained men

Purpose: It is not known whether it is possible to repeatedly supercompensate muscle glycogen stores after exhaustive exercise bouts undertaken within several days. Methods: We evaluated the effect of repeated exercise-diet manipulation on muscle glycogen and triacylglycerol (IMTG) metabolism and exercise capacity in six well-trained subjects who completed an intermittent, exhaustive cycling protocol (EX) on three occasions separated by 48 h (i.e., days 1, 3, and 5) in a 5-d period. Twenty-four hours before day 1, subjects consumed a moderate (6 g·kg-1)-carbohydrate (CHO) diet, followed by 5 d of a high (12 g·kg-1·d -1)-CHO diet. Muscle biopsies were taken at rest, immediately post-EX on days 1, 3, and 5, and after 3 h of recovery on days 1 and 3. Results: Compared with day 1, resting muscle [glycogen] was elevated on day 3 but not day 5 (435 ± 57 vs 713 ± 60 vs 409 ± 40 mmol·kg -1, P < 0.001). [IMTG] was reduced by 28% (P < 0.05) after EX on day 1, but post-EX levels on days 3 and 5 were similar to rest. EX was enhanced on days 3 and 5 compared with day 1 (31.9 ± 2.5 and 35.4 ± 3.8 vs 24.1 ± 1.4 kJ·kg-1, P < 0.05). Glycogen synthase activity at rest and immediately post-EX was similar between trials. Additionally, the rates of muscle glycogen accumulation were similar during the 3-h recovery period on days 1 and 3. Conclusion: We show that well-trained men cannot repeatedly supercompensate muscle [glycogen] after glycogen-depleting exercise and 2 d of a high-CHO diet, suggesting that the mechanisms responsible for glycogen accumulation are attenuated as a consequence of successive days of glycogen-depleting exercise.

Platinum-based chemotherapy in metastatic breast cancer : the Leicester (UK) experience

Aims: After failure of anthracycline- and taxane-based chemotherapy in metastatic breast cancer, treatment options until recently were limited. Until the introduction of capecitabine and vinorelbine, no standard regimen was available. We conducted a retrospective study to determine the efficacy and toxicity of platinum-based chemotherapy in metastatic breast cancer. Materials and methods: Forty-two women with metastatic breast cancer previously treated with anthracyclines (93%) and/or taxanes (36%) received mitomycin-vinblastine-cisplatin (MVP) (n = 23), or cisplatin-etoposide (PE) (n = 19), as first-, second- and third-line treatment at a tertiary referral centre between 1997 and 2002. Chemotherapy was given every 3 weeks as follows: mitomycin-C (8 mg/m 2) (cycles 1, 2, 4, 6), vinblastine (6 mg/m 2), and cisplatin (50 mg/m 2) all on day 1; and cisplatin (75 mg/m 2) and etoposide (100 mg/m 2) on day 1 and (100 mg/m 2) orally twice a day on days 2-3. Results: The response rate for 40 evaluable patients (MVP: n = 23; PE: n = 17) was 18% (95% confidence interval [CI]: 9-32%). The response rate to MVP was 13% (95% CI: 5-32%, one complete and two partial responses) and to PE 24% (10-47%, four partial responses). Disease stabilised in 43% (26-63%) and 47% (26-69%) of women treated with MVP and PE, respectively. After a median follow-up of 18 months, 37 women (MVP: n = 19; PE: n = 18) died from their disease. Median (range) progression-free survival and overall survival were 6 months (0.4-18.7) and 9.9 months (1.3-40.8), respectively. Median progression-free survival for the MVP and PE groups was 5.5 and 6.2 months (Log-rank, P = 0.82), and median overall survival was 10.2 and 9.4 months (Log-rank, P = 0.46), respectively. The main toxicity was myelosuppression. Grades 3-4 neutropenia was more common in women treated with PE than in women treated with MVP (74% vs 30%; P = 0.012), but the incidence of neutropenic sepsis, relative to the number of chemotherapy cycles, was low (7% overall). The toxicity-related hospitalisation rate was 1.2 admissions per six cycles of chemotherapy. No treatment-related deaths occurred. MVP and PE chemotherapy have modest activity and are safe in women with metastatic breast cancer. © 2005 The Royal College of Radiologists. Published by Elsevier Ltd. All rights reserved.

Epidural analgesia is associated with an increased incidence of postoperative complications in patients requiring an abdominal hysterectomy for early stage endometrial cancer

Objective Analgesia and early quality of recovery may be improved by epidural analgesia. We aimed to assess the effect of receiving epidural analgesia on surgical adverse events and quality of life after laparotomy for endometrial cancer. Methods Patients were enrolled in an international, multicentre, prospective randomised trial of outcomes for laparoscopic versus open surgical treatment for the management of apparent stage I endometrial cancer (LACE trial). The current analysis focussed on patients who received an open abdominal hysterectomy via vertical midline incision only (n = 257), examining outcomes in patients who did (n = 108) and did not (n = 149) receive epidural analgesia. Results Baseline characteristics were comparable between patients with or without epidural analgesia. More patients without epidural (34%) ceased opioid analgesia 3–5 days after surgery compared to patients who had an epidural (7%; p < 0.01). Postoperative complications (any grade) occurred in 86% of patients with and in 66% of patients without an epidural (p < 0.01) but there was no difference in serious adverse events (p = 0.19). Epidural analgesia was associated with increased length of stay (up to 48 days compared to up to 34 days in the non-epidural group). There was no difference in postoperative quality of life up to six months after surgery. Conclusions Epidural analgesia was associated with an increase in any, but not serious, postoperative complications and length of stay after abdominal hysterectomy. Randomised controlled trials are needed to examine the effect of epidural analgesia on surgical adverse events, especially as the present data do not support a quality of life benefit with epidural analgesia. Keywords Endometrial cancer; Hysterectomy; Epidural; Adverse events

Time course-dependent changes in the transcriptome of human skeletal muscle during recovery from endurance exercise: From inflammation to adaptive remodeling

Re-programming of gene expression is fundamental for skeletal muscle adaptations in response to endurance exercise. This study investigated the time-course dependent changes in the muscular transcriptome following an endurance exercise trial consisting of 1 h of intense cycling immediately followed by 1 h of intense running. Skeletal muscle samples were taken at baseline, 3 h, 48 h, and 96 h post-exercise from eight healthy, endurance-trained, male individuals. RNA was extracted from muscle. Differential gene expression was evaluated using Illumina microarrays and validated with qPCR. Gene set enrichment analysis identified enriched molecular signatures chosen from the Molecular Signatures Database. Three h post-exercise, 102 gene sets were up-regulated [family wise error rate (FWER), P < 0.05]; including groups of genes related with leukocyte migration, immune and chaperone activation, and cyclic AMP responsive element binding protein (CREB) 1-signaling. Forty-eight h post-exercise, among 19 enriched gene sets (FWER, P < 0.05), two gene sets related to actin cytoskeleton remodeling were up-regulated. Ninety-six h post-exercise, 83 gene sets were enriched (FWER, P < 0.05), 80 of which were up-regulated; including gene groups related to chemokine signaling, cell stress management, and extracellular matrix remodeling. These data provide comprehensive insights into the molecular pathways involved in acute stress, recovery, and adaptive muscular responses to endurance exercise. The novel 96 h post-exercise transcriptome indicates substantial transcriptional activity, potentially associated with the prolonged presence of leukocytes in the muscles. This suggests that muscular recovery, from a transcriptional perspective, is incomplete 96 h after endurance exercise involving muscle damage.

Carbonic anhydrase IX expression and outcome after radiotherapy for muscle-invasive bladder cancer

Aims: Carbonic anhydrase IX (CA IX) expression has been described as an endogenous marker of hypoxia in solid neoplasms. Furthermore, CA IX expression has been associated with an aggressive phenotype and resistance to radiotherapy. We assessed the prognostic significance of CA IX expression in patients with muscle-invasive bladder cancer treated with radiotherapy. Materials and methods: A standard immunohistochemistry technique was used to show CA IX expression in 110 muscle-invasive bladder tumours treated with radiotherapy. Clinicopathological data were obtained from medical case notes. Results: CA IX immunostaining was detected in 89 (∼81%) patients. Staining was predominantly membranous, with areas of concurrent cytoplasmic and nuclear staining and was abundant in luminal and perinecrotic areas. No significant correlation was shown between the overall CA IX status and the initial response to radiotherapy, 5-year bladder cancer-specific survival or the time to local recurrence. Conclusions: The distribution of CA IX expression in paraffin-embedded tissue sections seen in this series is consistent with previous studies in bladder cancer, but does not provide significant prognostic information with respect to the response to radiotherapy at 3 months and disease-specific survival after radical radiotherapy. © 2007 The Royal College of Radiologists.

Biomechanical characteristics of peripheral diabetic neuropathy : a systematic review and meta-analysis of findings from the gait cycle, muscle activity and dynamic barefoot plantar pressure

Background: Diabetic peripheral neuropathy is an important cause of foot ulceration and limb loss. This systematic review and meta-analysis investigated the effect of diabetic peripheral neuropathy on gait, dynamic electromyography and dynamic plantar pressures. Methods: Electronic databases were searched systematically for articles reporting the effect of diabetic peripheral neuropathy on gait, dynamic electromyography and plantar pressures. Searches were restricted to articles published between January 2000 and April 2012. Outcome measures assessed included spatiotemporal parameters, lower limb kinematics, kinetics, muscle activation and plantar pressure. Meta-analyses were carried out on all outcome measures reported by ≥3 studies. Findings: Sixteen studies were included consisting of 382 neuropathy participants, 216 diabetes controls without neuropathy and 207 healthy controls. Meta-analysis was performed on 11 gait variables. A high level of heterogeneity was noted between studies. Meta-analysis results suggested a longer stance time and moderately higher plantar pressures in diabetic peripheral neuropathy patients at the rearfoot, midfoot and forefoot compared to controls. Systematic review of studies suggested potential differences in the biomechanical characteristics (kinematics, kinetics, EMG) of diabetic neuropathy patients. However these findings were inconsistent and limited by small sample sizes.; Interpretation: Current evidence suggests that patients with diabetic peripheral neuropathy have elevated plantar pressures and occupy a longer duration of time in the stance-phase during gait. Firm conclusions are hampered by the heterogeneity and small sample sizes of available studies. Interpretation: Current evidence suggests that patients with diabetic peripheral neuropathy have elevated plantar pressures and occupy a longer duration of time in the stance-phase during gait. Firm conclusions are hampered by the heterogeneity and small sample sizes of available studies.