Sildenafil increases muscle protein synthesis and reduces muscle fatigue.
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ABSTRACT:
SUBMITTER: Sheffield-Moore M
PROVIDER: S-EPMC4076819 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The aim of this study was to investigate the effects of ankle and hip muscle fatigue on motor adjustments (experiment 1) and symmetry (experiment 2) of postural control during a quiet standing task. Twenty-three young adults performed a bipedal postural task on separate force platforms, before and after a bilateral ankle and hip muscle fatigue protocol (randomized). Ankle and hip muscles were fatigued separately using a standing calf raise protocol (ankle fatigue) on a step and flexion and extension of the hip (hip fatigue) sitting on a chair, at a controlled movement frequency (0.5Hz), respectively. In both experiments, force, center of pressure, and electromyography parameters were measured. The symmetry index was used in experiment 2 to analyze the postural asymmetry in the parameters. Our main findings showed that muscle fatigue impaired postural stability, regardless of the fatigued muscle region (i.e., ankle or hip). In addition, young adults used an ankle motor strategy (experiment 1) before and after both the ankle and hip muscle fatigue protocols. Moreover, we found increased asymmetry between the lower limbs (experiment 2) during the quiet standing task after muscle fatigue. Thus, we can conclude that the postural motor strategy is not muscle fatigue joint-dependent and a fatigue task increases postural asymmetry, regardless of the fatigued region (hip or ankle). These findings could be applied in sports training and rehabilitation programs with the objective of reducing the fatigue effects on asymmetry and improving balance.
| S-EPMC7906473 | biostudies-literature
Project description:Alcohol consumption affects many organs and tissues, including skeletal muscle. However, the molecular mechanism of ethanol action on skeletal muscle remains unclear. Here, using molecular dynamics simulations and single channel recordings, we show that ethanol interacts with a negatively charged amino acid within an extracellular region of the neuromuscular nicotinic acetylcholine receptor (nAChR), thereby altering its global conformation and reducing the single channel current amplitude. Charge reversal of the negatively charged amino acid abolishes the nAChR-ethanol interaction. Moreover, using transgenic animals harboring the charge-reversal mutation, ex vivo measurements of muscle force production show that ethanol counters fatigue in wild type but not homozygous αE83K mutant animals. In accord, in vivo studies of motor coordination following ethanol administration reveal an approximately twofold improvement for wild type compared to homozygous mutant animals. Together, the converging results from molecular to animal studies suggest that ethanol counters muscle fatigue through its interaction with neuromuscular nAChRs.
| S-EPMC6170420 | biostudies-literature
Project description:BackgroundA loss of muscle mass occurs as a consequence of a range of chronic and acute diseases as well as in older age. This wasting results from an imbalance of protein synthesis and degradation with a reduction in synthesis and resistance to anabolic stimulation often reported features. Ribosomes are required for protein synthesis, so changes in the control of ribosome synthesis are potential contributors to muscle wasting. MicroRNAs (miRNAs) are known regulators of muscle phenotype and have been shown to modulate components of the protein synthetic pathway. One miRNA that is predicted to target a number of components of protein synthetic pathway is miR-424-5p, which is elevated in the quadriceps of patients with chronic obstructive pulmonary disease (COPD).MethodsTargets of miR-424-5p were identified by Argonaute2 pull down, and the effects of the miRNA on RNA and protein expression were determined by quantitative polymerase chain reaction and western blotting in muscle cells in vitro. Protein synthesis was determined by puromycin incorporation in vitro. The miRNA was over-expressed in the tibialis anterior muscle of mice by electroporation and the effects quantified. Finally, quadriceps expression of the miRNA was determined by quantitative polymerase chain reaction in patients with COPD and intensive care unit (ICU)-acquired weakness and in patients undergoing aortic surgery as well as in individuals from the Hertfordshire Sarcopenia Study.ResultsPull-down assays showed that miR-424-5p bound to messenger RNAs encoding proteins associated with muscle protein synthesis. The most highly enriched messenger RNAs encoded proteins required for the Pol I RNA pre-initiation complex required for ribosomal RNA (rRNA) transcription, (PolR1A and upstream binding transcription factor). In vitro, miR-424-5p reduced the expression of these RNAs, reduced rRNA levels, and inhibited protein synthesis. In mice, over-expression of miR-322 (rodent miR-424 orthologue) caused fibre atrophy and reduced upstream binding transcription factor expression and rRNA levels. In humans, elevated miR-424-5p associated with markers of disease severity in COPD (FEV1 %), in patients undergoing aortic surgery (LVEF%), and in patients with ICU-acquired weakness (days in ICU). In patients undergoing aortic surgery, preoperative miR-424-5p expression in skeletal muscle was associated with muscle loss over the following 7 days.ConclusionsThese data suggest that miR-424-5p regulates rRNA synthesis by inhibiting Pol I pre-initiation complex formation. Increased miR-424-5p expression in patients with conditions associated with muscle wasting is likely to contribute to the inhibition of protein synthesis and loss of muscle mass.
| S-EPMC5879973 | biostudies-literature
Project description:Duchenne muscular dystrophy (DMD) is the most common form of muscular dystrophy caused by mutations in the dystrophin gene. Loss of dystrophin initiates a progressive decline in skeletal muscle integrity and contractile capacity which weakens respiratory muscles including the diaphragm, culminating in respiratory failure, the leading cause of morbidity and mortality in DMD patients. At present, corticosteroid treatment is the primary pharmacological intervention in DMD, but has limited efficacy and adverse side effects. Thus, there is an urgent need for new safe, cost-effective, and rapidly implementable treatments that slow disease progression. One promising new approach is the amplification of nitric oxide-cyclic guanosine monophosphate (NO-cGMP) signalling pathways with phosphodiesterase 5 (PDE5) inhibitors. PDE5 inhibitors serve to amplify NO signalling that is attenuated in many neuromuscular diseases including DMD. We report here that a 14-week treatment of the mdx mouse model of DMD with the PDE5 inhibitor sildenafil (Viagra(®), Revatio(®)) significantly reduced mdx diaphragm muscle weakness without impacting fatigue resistance. In addition to enhancing respiratory muscle contractility, sildenafil also promoted normal extracellular matrix organization. PDE5 inhibition slowed the establishment of mdx diaphragm fibrosis and reduced matrix metalloproteinase-13 (MMP-13) expression. Sildenafil also normalized the expression of the pro-fibrotic (and pro-inflammatory) cytokine tumour necrosis factor ? (TNF?). Sildenafil-treated mdx diaphragms accumulated significantly less Evans Blue tracer dye than untreated controls, which is also indicative of improved diaphragm muscle health. We conclude that sildenafil-mediated PDE5 inhibition significantly reduces diaphragm respiratory muscle dysfunction and pathology in the mdx mouse model of Duchenne muscular dystrophy. This study provides new insights into the therapeutic utility of targeting defects in NO-cGMP signalling with PDE5 inhibitors in dystrophin-deficient muscle.
| S-EPMC4067455 | biostudies-literature
Project description:BackgroundThe efficacy of Phosphodiesterase 5 (PDE5) inhibitors to re-establish endothelial function is reduced in diabetic patients. Recent evidences suggest that therapy with PDE5 inhibitors, i.e. sildenafil, may increase the expression of nitric oxide synthase (NOS) proteins in the heart and cardiomyocytes. In this study we analyzed the effect of sildenafil on endothelial cells in insulin resistance conditions in vitro.Methodology/principal findingsHuman umbilical vein endothelial cells (HUVECs) were treated with insulin in presence of glucose 30 mM (HG) and glucosamine 10 mM (Gluc-N) with or without sildenafil. Insulin increased the expression of PDE5 and eNOS mRNA assayed by Real time-PCR. Cytofluorimetric analysis showed that sildenafil significantly increased NO production in basal condition. This effect was partially inhibited by the PI3K inhibitor LY 294002 and completely inhibited by the NOS inhibitor L-NAME. Akt-1 and eNOS activation was reduced in conditions mimicking insulin resistance and completely restored by sildenafil treatment. Conversely sildenafil treatment can counteract this noxious effect by increasing NO production through eNOS activation and reducing oxidative stress induced by hyperglycaemia and glucosamine.Conclusions/significanceThese data indicate that sildenafil might improve NOS activity of endothelial cells in insulin resistance conditions and suggest the potential therapeutic use of sildenafil for improving vascular function in diabetic patients.
| S-EPMC3030559 | biostudies-literature
Project description:BackgroundAnimal studies and clinical data support the interest of citrulline as a promising therapeutic for sarcopenia. Citrulline is known to stimulate muscle protein synthesis, but how it affects energy metabolism to support the highly energy-dependent protein synthesis machinery is poorly understood.MethodsHere, we used myotubes derived from primary culture of mouse myoblasts to study the effect of citrulline on both energy metabolism and protein synthesis under different limiting conditions.ResultsWhen serum/amino acid deficiency or energy stress (mild uncoupling) were applied, citrulline stimulated muscle protein synthesis by +22% and +11%, respectively. Importantly, this increase was not associated with enhanced energy status (ATP/ADP ratio) or mitochondrial respiration. We further analysed the share of mitochondrial respiration and thus of generated ATP allocated to different metabolic pathways by using specific inhibitors. Our results indicate that addition of citrulline allocated an increased share of mitochondrially generated ATP to the protein synthesis machinery under conditions of both serum/amino acid deficiency (+28%) and energy stress (+21%). This reallocation was not because of reduced ATP supply to DNA synthesis or activities of sodium and calcium cycling ion pumps.ConclusionsUnder certain stress conditions, citrulline increases muscle protein synthesis by specifically reallocating mitochondrial fuel to the protein synthesis machinery. Because ATP/ADP ratios and thus Gibbs free energy of ATP hydrolysis remained globally constant, this reallocation may be linked to decreased activation energies of one or several ATP (and GTP)-consuming reactions involved in muscle protein synthesis.
| S-EPMC6711414 | biostudies-literature
Project description:Cancer patients frequently suffer from fatigue, a complex syndrome associated with loss of muscle mass, weakness, and depressed mood. Cancer-related fatigue (CRF) can be present at the time of diagnosis, during treatment, and persists for years after treatment. CRF negatively influences quality of life, limits functional independence, and is associated with decreased survival in patients with incurable disease. Currently there are no effective treatments to reduce CRF. The aim of this study was to use a mouse model of tumor growth and discriminate between two main components of fatigue: loss of muscle mass/function and altered mood/motivation. Here we show that tumor growth increased fatigue- and depressive-like behaviors, and reduced body and muscle mass. Decreased voluntary wheel running activity (VWRA) and increased depressive-like behavior in the forced swim and sucrose preference tests were evident in tumor-bearing mice within the first two weeks of tumor growth and preceded the loss of body and muscle mass. At three weeks, tumor-bearing mice had reduced grip strength but this was not associated with altered expression of myosin isoforms or impaired contractile properties of muscles. These increases in fatigue and depressive-like behaviors were paralleled by increased expression of IL-1? mRNA in the cortex and hippocampus. Minocycline administration reduced tumor-induced expression of IL-1? in the brain, reduced depressive-like behavior, and improved grip strength without altering muscle mass. Taken together, these results indicate that neuroinflammation and depressed mood, rather than muscle wasting, contribute to decreased voluntary activity and precede major changes in muscle contractile properties with tumor growth.
| S-EPMC4258420 | biostudies-literature
Project description:Factors underpinning the time-course of resistance-type exercise training (RET) adaptations are not fully understood. This study hypothesized that consuming a twice-daily protein-polyphenol beverage (PPB; n = 15; age, 24 ± 1 yr; BMI, 22.3 ± 0.7 kg·m-2) previously shown to accelerate recovery from muscle damage and increase daily myofibrillar protein synthesis (MyoPS) rates would accelerate early (10 sessions) improvements in muscle function and potentiate quadriceps volume and muscle fiber cross-sectional area (fCSA) following 30 unilateral RET sessions in healthy, recreationally active, adults. Versus isocaloric placebo (PLA; n = 14; age, 25 ± 2 yr; BMI, 23.9 ± 1.0 kg·m-2), PPB increased 48 h MyoPS rates after the first RET session measured using deuterated water (2.01 ± 0.15 vs. 1.51 ± 0.16%·day-1, respectively; P < 0.05). In addition, PPB increased isokinetic muscle function over 10 sessions of training relative to the untrained control leg (%U) from 99.9 ± 1.8 pretraining to 107.2 ± 2.4%U at session 10 (vs. 102.6 ± 3.9 to 100.8 ± 2.4%U at session 10 in PLA; interaction P < 0.05). Pre to posttraining, PPB increased type II fCSA (PLA: 120.8 ± 8.2 to 109.5 ± 8.6%U; PPB: 92.8 ± 6.2 to 108.4 ± 9.7%U; interaction P < 0.05), but the gain in quadriceps muscle volume was similar between groups. Similarly, PPB did not further increase peak isometric torque, muscle function, or MyoPS measured posttraining. This suggests that although PPB increases MyoPS and early adaptation, it may not influence longer term adaptations to unilateral RET.NEW & NOTEWORTHY Using a unilateral model of resistance training, we show for the first time that a protein-polyphenol beverage increases initial rates of myofibrillar protein synthesis and promotes early functional improvements. Following a prolonged period of training, this strategy also increases type II fiber hypertrophy and causes large individual variation in gains in quadricep muscle cross-sectional area.
| S-EPMC8897029 | biostudies-literature
Project description:BackgroundThe interactions between the insulin signaling pathway (ISP) and juvenile hormone (JH) controlling reproductive trade-offs are well documented in insects. JH and insulin regulate reproductive output in mosquitoes; both hormones are involved in a complex regulatory network, in which they influence each other and in which the mosquito's nutritional status is a crucial determinant of the network's output. Previous studies reported that the insulin-TOR (target of rapamacyn) signaling pathway is involved in the nutritional regulation of JH synthesis in female mosquitoes. The present studies further investigate the regulatory circuitry that controls both JH synthesis and reproductive output in response to nutrient availability.MethodsWe used a combination of diet restriction, RNA interference (RNAi) and insulin treatments to modify insulin signaling and study the cross-talk between insulin and JH in response to starvation. JH synthesis was analyzed using a newly developed assay utilizing fluorescent tags.ConclusionsOur results reveal that starvation decreased JH synthesis via a decrease in insulin signaling in the corpora allata (CA). Paradoxically, starvation-induced up regulation of insulin receptor transcripts and therefore "primed" the gland to respond rapidly to increases in insulin levels. During this response to starvation the synthetic potential of the CA remained unaffected, and the gland rapidly and efficiently responded to insulin stimulation by increasing JH synthesis to rates similar to those of CA from non-starved females.
| S-EPMC3906049 | biostudies-literature
Project description:Sildenafil is known to reduce cardiac hypertrophy through cGMP-dependent protein kinase (cGK) activation. Studies have demonstrated that cGK has a central switching role in modulating vascular smooth muscle cell (VSMC) phenotype in response to vascular injury. Here, we aimed to examine the effects of cGK activation by sildenafil on neointimal formation and platelet aggregation. After vascular injury, neointimal hyperplasia in rat carotid arteries was significantly reduced in the sildenafil-treated group. This effect of sildenafil was accompanied by the reduction of viability and migration of VSMCs. Further experiments showed that the increased cGK activity by sildenafil inhibited platelet-derived growth factor-induced phenotype change of VSMCs from a contractile form to a synthetic one. Conversely, the use of cGK inhibitor or gene transfer of dominant-negative cGK reversed the effects of sildenafil, increasing viability of VSMCs and neointimal formation. Interestingly, sildenafil significantly inhibited platelet aggregation induced by ADP or thrombin. This effect was reversed by cGK inhibitor, suggesting that sildenafil inhibits platelet aggregation via cGK pathway. This study demonstrated that sildenafil inhibited neointimal formation and platelet aggregation via cGK pathway. These results suggest that sildenafil could be a promising candidate for drug-eluting stents for the prevention of both restenosis and stent thrombosis.
| S-EPMC6533301 | biostudies-literature