Muscle Adenosine Triphosphate Research Articles

Early manifestation of hypophosphatemic rickets in goslings: a potential role of insufficient muscular adenosine triphosphate in motility impairment of early P-deficient geese

We aimed to determine the onset time of hypophosphatemic rickets and investigate the mechanism of motility impairment through adenosine triphosphate (ATP) production in goslings. Two hundred and sixteen 1-day-old male Jiangnan white geese were randomly divided into 3 groups, with 6 replicates and 12 geese per replicate. Birds were fed on 3 diets: a control diet (nonphytic phosphorus, NPP, 0.38%), a P-deficient diet (PD; NPP, 0.08%), and a high P diet (HP; NPP, 0.80%) for 14 d. Subsequently, all birds were shifted to the control diet for an additional 14 d. The cumulative incidence of lameness increased significantly (P < 0.01) starting on d 4, reaching over 80% on d 7 and 100% on d 12 in the PD group. Drinking and eating frequency decreased from d 4 and d 5, respectively, in the PD group compared to the other groups (most P < 0.01). The PD group exhibited shorter and narrower beaks, higher (worse) curvature scores of the beak and costochondral junctions, swelling caput costae, and dirtier feathers since d 4, in contrast to the control and HP groups (most P < 0.01). The HP had bigger (P < 0.05) beak and sternum sizes than the control groups on d 4 to 11. Leg muscle ATP levels were lower (P < 0.01 or 0.05) on d 4 to 11; in contrast, adenosine diphosphate (d 7-11) was higher in PD compared to the control (P < 0.05). Leg muscle ATP level had positive linear (R2 > 0.40) correlations (r > 0.60) with eating and drinking frequencies on d 7 and 11 (P < 0.01). Bone stiffness, feather cleanliness, and ATP levels recovered (P > 0.05) to the control level, whereas bone size did not recover (P < 0.05) in PD and HP after eating the control diet for 2 wk. The onset time of hypophosphatemic rickets was around 4 d in goslings, and insufficient leg muscle ATP was related to the impaired motility observed in early P-deficient geese.

The effects of creatine supplementation on cognitive performance—a randomised controlled study

BackgroundCreatine is an organic compound that facilitates the recycling of energy-providing adenosine triphosphate (ATP) in muscle and brain tissue. It is a safe, well-studied supplement for strength training. Previous studies have shown that supplementation increases brain creatine levels, which might increase cognitive performance. The results of studies that have tested cognitive performance differ greatly, possibly due to different populations, supplementation regimens, and cognitive tasks. This is the largest study on the effect of creatine supplementation on cognitive performance to date.MethodsOur trial was preregistered, cross-over, double-blind, placebo-controlled, and randomised, with daily supplementation of 5 g for 6 weeks each. We tested participants on Raven’s Advanced Progressive Matrices (RAPM) and on the Backward Digit Span (BDS). In addition, we included eight exploratory cognitive tests. About half of our 123 participants were vegetarians and half were omnivores.ResultsBayesian evidence supported a small beneficial effect of creatine. The creatine effect bordered significance for BDS (p = 0.064, η2P = 0.029) but not RAPM (p = 0.327, η2P = 0.008). There was no indication that creatine improved the performance of our exploratory cognitive tasks. Side effects were reported significantly more often for creatine than for placebo supplementation (p = 0.002, RR = 4.25). Vegetarians did not benefit more from creatine than omnivores.ConclusionsOur study, in combination with the literature, implies that creatine might have a small beneficial effect. Larger studies are needed to confirm or rule out this effect. Given the safety and broad availability of creatine, this is well worth investigating; a small effect could have large benefits when scaled over time and over many people.Trial registrationThe trial was prospectively registered (drks.de identifier: DRKS00017250, https://osf.io/xpwkc/).

Remote ischaemic conditioning for fatigue after stroke (RICFAST): A pilot randomised controlled trial

BackgroundPost stroke fatigue (PSF) affects 50 % of stroke survivors, and can be disabling. Remote ischaemic conditioning (RIC), can preserve mitochondrial function, improve tissue perfusion and may mitigate PSF. This pilot randomised controlled trial evaluates the safety and feasibility of using RIC for PSF and evaluated measures of cellular bioenergetics. Methods24 people with debilitating PSF (7 item Fatigue Severity Score, FSS-7 > 4) were randomised (1:1) in this single-centre phase 2 study to RIC (blood pressure cuff inflation around the upper arm 200 mmHg for 5 min followed by 5 min of deflation), or sham (inflation pressure 20 mmHg), repeated 4 cycles, 3 times per week for 6 weeks. Primary outcomes were safety, acceptability, and compliance. Secondary outcomes included FSS-7, 6 min walking test (6MWT), peak oxygen consumption (V̇O2peak), ventilatory anaerobic threshold (VAT), and muscle adenosine triphosphate (ATP) content measured using 31-phosphorous magnetic resonance spectroscopy of tibialis anterior. ResultsRIC was safe (no serious adverse events, adverse events mild) and adherence excellent (91 % sessions completed). Exploratory analysis revealed lower FSS-7 scores in the RIC group compared to sham at 6 weeks (between group difference FSS-7 -0.7, 95 %CI -2.0 to 0.6), 3 months (-1.0, 95 %CI -2.2 to 0.2) and 6 months (-0.9, 95 %CI -2.0 to 0.2). There were trends towards increased VAT, increased muscle ATP content and improved 6MWT in the RIC group. DiscussionRIC is safe and acceptable for people with PSF and may result in clinically meaningful improvements in fatigue and muscle bioenergetics that require further investigation in larger studies.

Myostatin Knockout Affects Mitochondrial Function by Inhibiting the AMPK/SIRT1/PGC1α Pathway in Skeletal Muscle.

Myostatin (Mstn) is a major negative regulator of skeletal muscle mass and initiates multiple metabolic changes. The deletion of the Mstn gene in mice leads to reduced mitochondrial functions. However, the underlying regulatory mechanisms remain unclear. In this study, we used CRISPR/Cas9 to generate myostatin-knockout (Mstn-KO) mice via pronuclear microinjection. Mstn-KO mice exhibited significantly larger skeletal muscles. Meanwhile, Mstn knockout regulated the organ weights of mice. Moreover, we found that Mstn knockout reduced the basal metabolic rate, muscle adenosine triphosphate (ATP) synthesis, activities of mitochondrial respiration chain complexes, tricarboxylic acid cycle (TCA) cycle, and thermogenesis. Mechanistically, expressions of silent information regulator 1 (SIRT1) and phosphorylated adenosine monophosphate-activated protein kinase (pAMPK) were down-regulated, while peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) acetylation modification increased in the Mstn-KO mice. Skeletal muscle cells from Mstn-KO and WT were treated with AMPK activator 5-aminoimidazole-4-carboxamide riboside (AICAR), and the AMPK inhibitor Compound C, respectively. Compared with the wild-type (WT) group, Compound C treatment further down-regulated the expression or activity of pAMPK, SIRT1, citrate synthase (CS), isocitrate dehydrogenase (ICDHm), and α-ketoglutarate acid dehydrogenase (α-KGDH) in Mstn-KO mice, while Mstn knockout inhibited the AICAR activation effect. Therefore, Mstn knockout affects mitochondrial function by inhibiting the AMPK/SIRT1/PGC1α signaling pathway. The present study reveals a new mechanism for Mstn knockout in regulating energy homeostasis.

Acipimox in Mitochondrial Myopathy (AIMM): study protocol for a randomised, double-blinded, placebo-controlled, adaptive design trial of the efficacy of acipimox in adult patients with mitochondrial myopathy

BackgroundMitochondrial disease is a heterogenous group of rare, complex neurometabolic disorders. Despite their individual rarity, collectively mitochondrial diseases represent the most common cause of inherited metabolic disorders in the UK; they affect 1 in every 4300 individuals, up to 15,000 adults (and a similar number of children) in the UK. Mitochondrial disease manifests multisystem and isolated organ involvement, commonly affecting those tissues with high energy demands, such as skeletal muscle. Myopathy manifesting as fatigue, muscle weakness and exercise intolerance is common and debilitating in patients with mitochondrial disease. Currently, there are no effective licensed treatments and consequently, there is an urgent clinical need to find an effective drug therapy.AimTo investigate the efficacy of 12-week treatment with acipimox on the adenosine triphosphate (ATP) content of skeletal muscle in patients with mitochondrial disease and myopathy.MethodsAIMM is a single-centre, double blind, placebo-controlled, adaptive designed trial, evaluating the efficacy of 12 weeks’ administration of acipimox on skeletal muscle ATP content in patients with mitochondrial myopathy. Eligible patients will receive the trial investigational medicinal product (IMP), either acipimox or matched placebo. Participants will also be prescribed low dose aspirin as a non-investigational medical product (nIMP) in order to protect the blinding of the treatment assignment.Eighty to 120 participants will be recruited as required, with an interim analysis for sample size re-estimation and futility assessment being undertaken once the primary outcome for 50 participants has been obtained. Randomisation will be on a 1:1 basis, stratified by Fatigue Impact Scale (FIS) (dichotomised as < 40, ≥ 40). Participants will take part in the trial for up to 20 weeks, from screening visits through to follow-up at 16 weeks post randomisation.The primary outcome of change in ATP content in skeletal muscle and secondary outcomes relating to quality of life, perceived fatigue, disease burden, limb function, balance and walking, skeletal muscle analysis and symptom-limited cardiopulmonary fitness (optional) will be assessed between baseline and 12 weeks.DiscussionThe AIMM trial will investigate the effect of acipimox on modulating muscle ATP content and whether it can be repurposed as a new treatment for mitochondrial disease with myopathy.Trial registrationEudraCT2018-002721-29. Registered on 24 December 2018,ISRCTN 12895613. Registered on 03 January 2019, https://www.isrctn.com/search?q=aimm

A CASE OF ACCELERATED RIGOR MORTIS

Introduction. Rigor mortis is the tension of skeletal and smooth muscles that occurs after death and fixes the body in a certain position. It is one of the signs of biological death and usually develops in 1.5 - 3 hours, starting from the lower jaw. The full development of rigor mortis is observed in 12 - 24 hours after death. But in rare cases, its development can be significantly accelerated. Clinical case. A 34-year-old man was in the department of anesthesiology and intensive care for 4 days with a diagnosis of explosive trauma, neck injury with damage to the right carotid artery, hemispheric ischemic stroke. In the setting of multiple organ failure, moderate coma, central hyperthermia (40.3 °C), resistant to antipyretics, he went into a cardiac arrest. Resuscitation measures (including triple defibrillation) for 50 minutes were without effect. During the ascertainment of biological death, the presence of rigor mortis was noted in the lower jaw, neck and extremities, which was absent during the first 30 minutes of resuscitation and at the beginning of the asystolic rhythm. Discussion. The occurrence of rigor mortis is explained by the release of calcium ions from myocytes and the depletion of muscle adenosine triphosphate, which leads to the formation of a stable bond between actin and myosin. Instant or accelerated rigor mortis is rare. According to the literature, high body temperature, strenuous exercise before death, electric shock, convulsions and muscular dystrophy contribute to the acceleration of rigor mortis. Conclusions. In our case, the patient had severe hyperthermia (40.3 ° C), and defibrillation was performed during resuscitation, ie the body was exposed to electric current. Probably, these factors caused the accelerated development of rigor mortis.

Effects of dietary fishmeal levels on adenosine triphosphate-related compounds and freshness of raw and cooked muscle in large yellow croaker Larimichthys crocea

A comparative study on the adenosine triphosphate (ATP)-related compounds and freshness of raw and cooked muscle in wild and farmed large yellow croaker (Larimichthys crocea) was performed. The two groups of farmed fish (189.87 ± 0.89 g) were fed two diets containing 44% (CF) and 25% (LF) of fish meal (FM) for 82 days, respectively. Results showed that the contents of ATP, adenosine diphosphate (ADP), adenosine monophosphate (AMP) and inosine 5′-monophosphate (IMP) were highest in raw and cooked muscle of wild fish, while these values were lowest in raw and cooked muscle of fish fed LF. Conversely, wild fish had the lowest inosine (Ino) and hypoxanthine (Hx) contents in raw and cooked flesh, while the LF group had the highest levels of Ino and Hx in raw and cooked flesh. Fish fed CF had significantly higher amounts of ATP, ADP and IMP in raw muscle, ATP and AMP in cooked muscle than those in the LF group (P < 0.05). The above results allowed wild fish to have the lowest K and Ki values, closely followed by fish fed CF, and the LF group have the highest values in raw and cooked muscle (P < 0.05). Meanwhile, cooking significantly decreased ATP, ADP and IMP contents, while increased AMP and Ino levels, inducing significantly higher K and Ki values in cooked muscle of all the treatments (P < 0.05). In conclusion, lower dietary FM level could decrease the contents of IMP and its precursors, and increase the degradation products of IMP in muscle, leading to the declines in umami and freshness. The stronger umami of wild large yellow croaker could be related to the higher precursors and lower degradation products of IMP in fillets.

Dietary guanidineacetic acid supplementation ameliorated meat quality and regulated muscle metabolism of broilers subjected to pre-slaughter transport stress by metabolomics analysis

Pre-slaughter transport stress could induce multiple comprehensive variations in physiological and metabolic parameters of broilers. However, the entire metabolomics of pre-slaughter transport stress and supplementation of exogenous energy regulatory substances on broilers is still poorly understood. The metabolome characteristics of broilers subjected to 3 h pre-slaughter transport stress combined with 1,200 mg/kg guanidinoacetic acid (GAA1,200) supplementation were analyzed using gas chromatography-mass spectrometry (GC−MS) in this study. The results showed that, compared to the control group (no transport), 3 h pre-slaughter transport stress (T3h) decreased creatine (Cr), phosphocreatine (PCr) and adenosine triphosphate (ATP), and increased adenosine diphosphate (ADP), adenosine monophosphate (AMP) and the ratio of AMP to ATP in pectoralis muscle (PM) of broilers by high performance liquid chromatography (HPLC) analysis. However, GAA1,200 supplementation reversed the negative effects induced by 3 h pre-slaughter transport stress. Besides, GAA1,200 supplementation elevated mRNA expression of creatine transporter in PM. Our metabolomics approaches demonstrated that 38 and 48 significant metabolites were separately identified between the control group and T3h group, and T3h group and 3 h pre-slaughter transport stress combined with GAA1,200 supplementation group using the standard of variable importance in the projection values >1 and P < 0.05. Among these, the metabolites involved in amino acid metabolism (alanine, glycine, serine, threonine, cysteine , methionine, phenylalanine, tyrosine, and tryptophan), oxidative stress (3-methylhistidine, 1-methylhistidine and glutathione), non-protein amino acid (citrulline) metabolism, and energy metabolism (Cr, PCr, sarcosine, and glycocyamine) were confirmed through pathway enrichment analysis, which could be chosen as suitable candidate targets for further analysis of the effects of exogenous energy substances on broilers subjected to transport stress.

Targeting interleukin-1 for reversing fat browning and muscle wasting in infantile nephropathic cystinosis.

Background Ctns −/− mice, a mouse model of infantile nephropathic cystinosis, exhibit hypermetabolism with adipose tissue browning and profound muscle wasting. Inflammatory cytokines such as interleukin (IL)‐1 trigger inflammatory cascades and may be an important cause for cachexia. We employed genetic and pharmacological approaches to investigate the effects of IL‐1 blockade in Ctns −/− mice.MethodsWe generated Ctns −/− Il1β −/− mice, and we treated Ctns −/− and wild‐type control mice with IL‐1 receptor antagonist, anakinra (2.5 mg/kg/day, IP) or saline as vehicle for 6 weeks. In each of these mouse lines, we characterized the cachexia phenotype consisting of anorexia, loss of weight, fat mass and lean mass, elevation of metabolic rate, and reduced in vivo muscle function (rotarod activity and grip strength). We quantitated energy homeostasis by measuring the protein content of uncoupling proteins (UCPs) and adenosine triphosphate in adipose tissue and skeletal muscle. We measured skeletal muscle fiber area and intramuscular fatty infiltration. We also studied expression of molecules regulating adipose tissue browning and muscle mass metabolism. Finally, we evaluated the impact of anakinra on the muscle transcriptome in Ctns −/− mice.ResultsSkeletal muscle expression of IL‐1β was significantly elevated in Ctns −/− mice relative to wild‐type control mice. Cachexia was completely normalized in Ctns −/− Il1β −/− mice relative to Ctns −/− mice. We showed that anakinra attenuated the cachexia phenotype in Ctns −/− mice. Anakinra normalized UCPs and adenosine triphosphate content of adipose tissue and muscle in Ctns −/− mice. Anakinra attenuated aberrant expression of beige adipose cell biomarkers (UCP‐1, CD137, Tmem26, and Tbx1) and molecules implicated in adipocyte tissue browning (Cox2/Pgf2α, Tlr2, Myd88, and Traf6) in inguinal white adipose tissue in Ctns −/− mice. Moreover, anakinra normalized gastrocnemius weight and fiber size and attenuated muscle fat infiltration in Ctns −/− mice. This was accompanied by correction of the increased muscle wasting signalling pathways (increased protein content of ERK1/2, JNK, p38 MAPK, and nuclear factor‐κB p65 and mRNA expression of Atrogin‐1 and Myostatin) and the decreased myogenesis process (decreased mRNA expression of MyoD and Myogenin) in the gastrocnemius muscle of Ctns −/− mice. Previously, we identified the top 20 differentially expressed skeletal muscle genes in Ctns −/− mice by RNAseq. Aberrant expression of these 20 genes have been implicated in muscle wasting, increased energy expenditure, and lipolysis. We showed that anakinra attenuated 12 of those top 20 differentially expressed muscle genes in Ctns −/− mice.ConclusionsAnakinra may provide a targeted novel therapy for patients with infantile nephropathic cystinosis.

Muscle atrophy induced by overexpression of ALAS2 is related to muscle mitochondrial dysfunction

BackgroundALAS2 (delta-aminolevulinate synthase 2) is one of the two isoenzymes catalyzing the synthesis of delta-aminolevulinic acid (ALA), which is the first precursor of heme synthesis. ALAS2-overexpressing transgenic mice (Tg mice) showed syndrome of porphyria, a series of diseases related to the heme anabolism deficiency. Tg mice showed an obvious decrease in muscle size. Muscle atrophy results from a decrease in protein synthesis and an increase in protein degradation, which ultimately leads to a decrease in myofiber size due to loss of contractile proteins, organelles, nuclei, and cytoplasm.MethodsThe forelimb muscle grip strength of age-matched ALAS-2 transgenic mice (Tg mice) and wild-type mice (WT mice) were measured with an automated grip strength meter. The activities of serum LDH and CK-MB were measured by Modular DPP. The histology of skeletal muscle (quadriceps femoris and gastrocnemius) was observed by hematoxylin and eosin (HE) staining, immunohistochemistry, and transmission electron microscope. Real-time PCR was used to detect mtDNA content and UCP3 mRNA expression. Evans blue dye staining was used to detect the membrane damage of the muscle fiber. Single skeletal muscle fiber diameter was measured by single-fiber analyses. Muscle adenosine triphosphate (ATP) levels were detected by a luminometric assay with an ATP assay kit.ResultsCompared with WT mice, the strength of forelimb muscle and mass of gastrocnemius were decreased in Tg mice. The activities of serum CK-MB and LDH, the number of central nuclei fibers, and Evans blue positive fibers were more than those in WT mice, while the diameter of single fibers was smaller, which were associated with suppressed expression levels of MHC, myoD1, dystrophin, atrogin1, and MuRF1. Re-expression of eMyHC was only showed in the quadriceps of Tg mice, but not in WT mice. Muscle mitochondria in Tg mice showed dysfunction with descented ATP production and mtDNA content, downregulated UCP3 mRNA expression, and swelling of mitochondria.ConclusionALAS2 overexpressing-transgenic mice (Tg mice) showed muscle dystrophy, which was associated with decreased atrogin-1 and MuRF-1, and closely related to mitochondrial dysfunction.

Reduced expression of carbonic anhydrase III in skeletal muscles could be linked to muscle fatigue: A rat muscle fatigue model

BackgroundCarbonic anhydrase III (CAIII) is expressed abundantly in slow skeletal muscles, adipocytes, and the liver. It plays a critical role in maintaining intracellular pH, antioxidation, and energy metabolism, which are further involved in fatigue. However, its function and mechanism in maintaining the physiological function of muscles or antifatigue are still ambiguous. We hypothesized that changes of CAIII in skeletal muscles might be related to the occurrence of muscle fatigue. MethodAfter establishing a rat soleus muscle fatigue model, we measured the protein expression of the CAIII in muscles. And the muscle intracellular biochemical indices [malondialdehyde (MDA), adenosine triphosphate (ATP), and lactic acid] were also measured using assay kits. After transfected by CAIII-overexpressing and knockdown lentiviral vectors, the rat soleus muscles were induced to fatigue to investigate the effects and possible molecular mechanisms of CAIII in antifatigue. ResultsThe expression of CAIII in fatigued soleus muscles was significantly decreased compared with that of the control group (P ​< ​0.001). Moreover, the ATP level in the fatigued muscle also significantly decreased, whereas lactic acid and MDA levels were significantly increased (P ​< ​0.001). After posttransfection for 21 days, CAIII levels in muscles were significantly reduced in the CAIII-interfering lentivirus group, but increased in the CAIII-overexpressed lentivirus group (P ​< ​0.001). In addition, CAIII knockdown muscles showed more reduction of the maximal muscle force and ATP levels ​and more increase of MDA and lactic acid levels during the fatigue test than the control group, (P ​< ​0.05). On the other hand, CAIII-overexpressed muscles showed less reduction of the maximal muscle force and ATP levels and less increase of MDA and lactic acid levels during muscle fatigue than the control group (P ​< ​0.05). ConclusionsOur study showed that soleus muscle fatigue induced by electrical stimulation could result in downregulation of CAIII and ATP levels ​and accumulation of lactic acid and MDA. Further study showed that CAIII knockdown led to more reduction of the maximal muscle force, whereas CAIII overexpression showed less reduction of the maximal muscle force, which suggested that CAIII levels in muscles might be related to the occurrence of muscle fatigue. Translational potentialCAIII plays an important role in muscle fatigue. Up-regulating the expression of CAIII might contribute to dissipating fatigue, which would provide a new method to solve the difficulties in eliminating muscular fatigue.

Modular 31 P wideband inversion transfer for integrative analysis of adenosine triphosphate metabolism, T1 relaxation and molecular dynamics in skeletal muscle at 7T.

For efficient and integrative analysis of de novo adenosine triphosphate (ATP) synthesis, creatine-kinase-mediated ATP synthesis, T1 relaxation time, and ATP molecular motion dynamics in human skeletal muscle at rest. Four inversion-transfer modules differing in center inversion frequency were combined to generate amplified magnetization transfer (MT) effects in targeted MT pathways, including Pi ↔ γ-ATP, PCr ↔ γ-ATP, and 31 Pγ(α)ATP ↔ 31 PβATP . MT effects from both forward and reverse exchange kinetic pathways were acquired to reduce potential bias and confounding factors in integrated data analysis. Kinetic data collected using 4 wideband inversion modules (8 minutes each) yielded the forward exchange rate constants, kPCr→γATP = 0.31 ± 0.05 s-1 and kPi→γATP = 0.064 ± 0.012 s-1 , and the reverse exchange rate constants, kγATP→Pi = 0.034 ± 0.006 s-1 and kγATP→PCr = 1.37 ± 0.22 s-1 , respectively. The cross-relaxation rate constant, σγ(α) ↔ βATP was -0.20 ± 0.03 s-1 , corresponding to ATP rotational correlation time τc of 0.8 ± 0.1 × 10-7 seconds. The intrinsic T1 relaxation times were Pi (9.2 ± 1.4 seconds), PCr (6.2 ± 0.4 seconds), γ-ATP (1.8 ± 0.1 seconds), α-ATP (1.4 ± 0.1 seconds), and β-ATP (1.1 ± 0.1 seconds). Muscle ATP T1 values were found to be significantly longer than those previously measured in the brain using a similar method. A combination of multiple inversion transfer modules provides a comprehensive and integrated analysis of ATP metabolism and molecular motion dynamics. This relatively fast technique could be potentially useful for studying metabolic disorders in skeletal muscle.

Endurance and Brain Glycogen: A Clue Toward Understanding Central Fatigue.

Brain glycogen stored in astrocytes produces lactate as a neuronal energy source transported by monocarboxylate transporters (MCTs) to maintain neuronal functions, such as hippocampus-regulated memory formation. Although exercise activates brain neurons, the role of astrocytic glycogen in the brain during exercise remains unknown. Since muscle glycogen fuels active muscles during exercise, we hypothesized that astrocytic glycogen plays an energetic role in the brain during exercise to maintain endurance capacity through lactate transport. To explore this hypothesis, we have used a rat model of prolonged exercise, microwave irradiation for the accurate detection of brain glycogen, capillary electrophoresis-mass spectrometry-based metabolomics, and inhibitors of glycogenolysis (1,4-dideoxy-1,4-imino-D-arabinitol; DAB) and lactate transport (α-cyano-4-hydroxycinnamate; 4-CIN). During prolonged exhaustive exercise, muscle glycogen was depleted and brain glycogen decreased when associated with decreased blood glucose levels and increased serotonergic activity known as central fatigue factors, suggesting brain glycogen decrease as an integrative factor for central fatigue. Prolonged exhaustive exercise also increased MCT2 protein in the brain, which takes up lactate in neurons, just as muscle MCTs are increased. Metabolomics revealed that brain but not muscle adenosine triphosphate (ATP) was maintained with lactate and other glycogenolytic and glycolytic sources. Intracerebroventricular (icv) injection of DAB suppressed brain lactate production and decreased hippocampal ATP levels at exhaustion. An icv injection of 4-CIN also decreased hippocampal ATP, resulting in lower endurance capacity. Our findings provide direct evidence that astrocytic glycogen-derived lactate fuels the brain to maintain endurance capacity during exhaustive exercise. Brain ATP levels maintained by glycogen might serve as a possible defense mechanism for neurons in the exhausted state.

Effects of electroacupuncture at "Zusanli" (ST 36) on expression of mitophagy-related proteins in skeletal muscle in rats with spleen deficiency syndrome

To observe the expression change of mitophagy-related proteins in skeletal muscle in rats with spleen deficiency syndrome and to explain the partial action mechanism of acupuncture at Zusanli (ST 36) for spleen deficiency syndrome. Forty male SD rats, after normal feeding, were randomly divided into a normal group, a spleen deficiency group, a Zusanli group and a non-acupoint group, ten rats in each group. Except the normal group, the three factors modeling method was used for 14 days to establish the model of spleen deficiency syndrome on the other 3 groups. The rats in the Zusanli group were treated with EA at bilateral "Zusanli" (ST 36), while the rats in the non-acupoint group were treated with EA at bilateral non acupoint (dense-sparse wave, frequency of 2 Hz/100 Hz, 20 min per treatment, once a day for 10 days). The rats in the normal group and spleen deficiency group were treated with immobilization for 20 min per day, and no EA was given. The HPLC method was applied to measure the content of adenosine triphosphate (ATP) and adenosine monophosphate (AMP) in skeletal muscle. The Western blotting method was applied to measure the expression of adenosine monophosphate activated protein kinase (AMPK), p-AMPK, ULK1, p-ULK1，LC3-Ⅰand LC3-Ⅱ in skeletal muscle. The ATP content in the spleen deficiency group was significantly lower than that in the normal group (P<0.01); the ATP content in the Zusanli group was significantly higher than that in the spleen deficiency group (P<0.05) but lower than that in the normal group (P<0.05), there was no significant difference between the non-acupoint group and the spleen deficiency group (P>0.05). Compared with the normal group, the AMP/ATP in the spleen deficiency group and the Zusanli group were significantly up-regulated (P<0.01, P<0.05). The differences of p-AMPK/AMPK between the spleen deficiency group and the normal group was not significant (P>0.05). Compared with the normal group and spleen deficiency group, the p-AMPK/AMPK in the Zusanli group was significantly up-regulated (both P<0.05). The p-ULK1/ULK1 and LC3-Ⅱ/LC3-Ⅰin the Zusanli group was higher than those in the normal group and spleen deficiency group (all P<0.01). EA at "Zusanli" (ST 36) might activate AMPK and produce stable ULK1/AMPK compound and increase the mitochondrial autophagy, which could regulate spleen-stomach and treat spleen deficiency.

Plasma Amino Acids Stimulate Uncoupled Respiration of Muscle Subsarcolemmal Mitochondria in Lean but Not Obese Humans.

Obesity is associated with mitochondrial dysfunction in skeletal muscle. Increasing the plasma amino acid (AA) concentrations stimulates mitochondrial adenosine triphosphate (ATP) production in lean individuals. To determine whether acute elevation in plasma AAs enhances muscle mitochondrial respiration and ATP production in subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria in obese adults. Assessment of SS and IMF mitochondrial function during saline (i.e., control) and AA infusions. Eligible participants were healthy lean (body mass index, <25 kg/m2; age, 37 ± 3 years; n = 10) and obese (body mass index >30 kg/m2; age 35 ± 3 years; n = 11) subjects. Single trial of saline infusion followed by AA infusion. SS and IMF mitochondria were isolated from muscle biopsies collected at the end of the saline and AA infusions. Mitochondrial respiration and ATP production. AA infusion increased adenosine 5'-diphosphate (ADP)-stimulated respiration and ATP production rates of SS mitochondria in the lean (P < 0.05), but not obese, subjects. Furthermore, AA infusion increased the uncoupled (i.e., non-ADP-stimulated) respiration of SS mitochondria in the lean subjects only (P < 0.05). AA infusion had no effect on any of these parameters in IMF mitochondria in either lean or obese subjects (P > 0.05). Increasing the plasma AA concentrations enhances the capacity for respiration and ATP production of muscle SS, but not IMF, mitochondria in lean individuals, in parallel with increases in uncoupled respiration. However, neither of these parameters increases in muscle SS or IMF mitochondria in obese individuals.

The influence of D-ribose ingestion and fitness level on performance and recovery

BackgroundSkeletal muscle adenosine triphosphate (ATP) levels are severely depleted during and following prolonged high intensity exercise. Recovery from these lower ATP levels can take days, which can affect performance on subsequent days of exercise. Untrained individuals often suffer the stress and consequences of acute, repeated bouts of exercise by not having the ability to perform or recovery sufficiently to exercise on subsequent days. Conversely, trained individuals may be able to recover more quickly due to their enhanced metabolic systems. D-Ribose (DR) has been shown to enhance the recovery in ATP; however, it is not known if recovery and performance can be benefitted with DR ingestion. Therefore, this study was designed to determine what influence DR might have on muscular performance, recovery, and metabolism during and following a multi-day exercise regimen.MethodsThe study was a double blind, crossover study in 26 healthy subjects compared 10 g/day of DR to 10 g/day of dextrose (DEX, control). All subjects completed 2 days of loading with either DR or DEX, followed by 3 additional days of supplementation and during these 3 days of supplementation, each subject underwent 60 min of high intensity interval exercise in separate daily sessions, which involved cycling (8 min of exercise at 60% and 2 min at 80% VO2max), followed by a 2 min power output (PO) test. Subjects were divided into two groups based on peak VO2 results, lower VO2 (LVO2) and higher peak VO2 (HVO2).ResultsMean and peak PO increased significantly from day 1 to day 3 for the DR trial compared to DEX in the LVO2 group. Rate of perceived exertion (RPE) and creatine kinase (CK) were significantly lower for DR than DEX in the LVO2 group. No differences in PO, RPE, heart rate, CK, blood urea nitrogen, or glucose were found between either supplement for the HVO2 group.ConclusionDR supplementation in the lower VO2 max group resulted in maintenance in exercise performance, as well as lower levels of RPE and CK. Unlike no observed benefits with DEX supplementation.

Effect of DNase I treatment and neutrophil depletion on acute limb ischemia-reperfusion injury in mice

Extracellular traps (ETs) consisting of DNA-protein complexes formed after tissue injury contribute to the inflammatory and thrombosis cascades, thereby exacerbating injury. Exogenous DNase I has been suggested as a therapeutic strategy to limit injury in the brain and myocardium. These studies were designed to evaluate the effects of exogenous DNase I treatment on skeletal muscle injury after acute hindlimb ischemia-reperfusion (IR) injury in mice and to determine whether neutrophils are a major source of ETs in postischemic muscle tissue. C57BL6 mice were subjected to 1.5hours of tourniquet ischemia and 24hours of reperfusion with and without human recombinant DNase I treatment. A separate set of mice was subjected to neutrophil depletion (ND), followed by the same intervals of IR. Laser Doppler imaging and tissue harvesting were done at 24hours for assessment of limb perfusion, muscle fiber injury, adenosine triphosphate (ATP) level, markers of inflammation, thrombosis, and formation of ETs. DNase I treatment significantly reduced detection of ETs in postischemic muscle but did not alter skeletal muscle fiber injury, levels of proinflammatory molecules, or ATP level. DNase I treatment did enhance postischemic hindlimb perfusion, decreased infiltrating inflammatory cells, and reduced the expression of thrombin-antithrombin III. ND resulted in a significant yet small reduction in ETs in the postischemic muscle. ND did not alter skeletal muscle fiber injury, hindlimb perfusion, or ATP levels. These data suggest that neither DNase I treatment nor ND was protective against IR injury, even though both decreased detection of ETs in skeletal muscle after IR. Neutrophils are not the only source of ETs after IR.

The Influence Of Ribose Ingestion On Recovery And Performance In Healthy Individuals.

PURPOSE: Skeletal muscle adenosine triphosphate (ATP) levels are depleted during and following high intensity exercise. Previous studies have shown that recovery of these lower ATP levels can take days, which ultimately can affect performance. Ribose has been shown to enhance the recovery in ATP; however, how is performance affected with this metabolic recovery? Therefore, we investigated the influence of ingesting 10 g/day of D-ribose (DR) on muscular recovery, performance, and metabolism during and following a multi-day exercise regimen. METHODS: A double blind, crossover study in 18 healthy subjects compared 10 g/day of DR to 10 g/day of dextrose (DEX, control). All subjects completed 2 days of loading with either DR or DEX, followed by 3 days of additional supplemental treatment, as well as undergoing high intensity interval exercise. Exercise assessment protocol consisted of cycling for 60 min (8 min of exercise at 60% and 2 min at 80% VO2max), followed by a 2 min power test evaluation (PO). RESULTS: Mean and peak PO increased from day 1 to day 3 by 2% (p = 0.04) and 6% (p = 0.03), respectively, for DR, but was only maintained with DEX. Rating of Perceived Exertion (RPE) was significantly lower for DR than DEX. Subjects were then further assessed between the low and high VO2max values. The lower VO2max subjects had a significant increase in CK (by 57%), as well as a 4% greater increase in HR, and greater RPE with DEX as compared to DR. Further, in the lower VO2max DR subjects, there was a significantly lower exercising HR and RPE (13.1 +/- 1.7 vs. 13.7 +/- 1.5), and an improvement in PO. No differences in HR, CK, BUN, GLUC, or lactate were found between either supplement. However, there was a 40% increase in the main effect of time for CK elevation regardless of treatment. CONCLUSIONS: DR supplementation led to greater performance changes than DEX during and following high intensity interval cycling exercise. Furthermore, upon sub group analysis between VO2max differences revealed additional benefits with DR. DR supplementation within this lower VO2max group resulted in maintenance in exercise performance, as well as potentially lessening muscular cell damage which can greatly influence cellular recovery and subsequent performance.

Effect of limb demand ischemia on autophagy and morphology in mice

BackgroundObesity is a major risk factor for diabetes and peripheral arterial disease, which frequently leads to lower limb demand ischemia. Skeletal muscle autophagy and mitochondrial biogenesis are important processes for proper oxidative capacity and energy metabolism, which are compromised in diabetes. This study compares autophagy, mitochondrial biogenesis, energy metabolism, and morphology in the hind limbs of obese diabetic mice subjected to demand or sedentary ischemia. Materials and methodsUnilateral hind limb demand ischemia was created in a group of diet-induced obese mice after femoral artery ligation and 4 wk of daily exercise. A parallel group of mice underwent femoral artery ligation but remained sedentary for 4 wk. Hind limb muscles were analyzed for markers of autophagy, mitochondrial biogenesis, adenosine triphosphate, and muscle tissue morphology. ResultsAt the end of the 4-wk exercise period, demand ischemia increased the autophagy mediator Beclin-1, but it did not alter the autophagy indicator, LC3B-II/I ratio, or markers of mitochondrial biogenesis, optic atrophy/dynamin-related protein. In contrast, exercise significantly increased the level of mitochondrial protein-succinate dehydrogenase subunit-A and reduced adipocyte accumulation and the percentage of centrally nucleated myofibers in the demand ischemia limb. In addition, demand ischemia resulted in decreased uncoupling protein-3 levels without altering muscle adenosine triphosphate or pS473-Akt levels. ConclusionsLimb demand ischemia markedly decreased adipocyte accumulation and enhanced muscle regeneration in obese mice, but it did not appear to enhance autophagy, mitochondrial biogenesis, energy metabolism, or insulin sensitivity. Future studies aimed at evaluating novel therapies that enhance autophagy and mitochondrial biogenesis in diabetes with peripheral arterial disease are warranted.

Time response of increases in ATP and muscle resistance to fatigue after low-level laser (light) therapy (LLLT) in mice.

Recently, low-level laser (light) therapy has been used to increase muscle performance in intense exercises. However, there is a lack of understanding of the time response of muscles to light therapy. The first purpose of this study was to determine the time response for light-emitting diode therapy (LEDT)-mediated increase in adenosine triphosphate (ATP) in the soleus and gastrocnemius muscles in mice. Second purpose was to test whether LEDT can increase the resistance of muscles to fatigue during intense exercise. Fifty male Balb/c mice were randomly allocated into two equal groups: LEDT-ATP and LEDT-fatigue. Both groups were subdivided into five equal subgroups: LEDT-sham, LEDT-5 min, LEDT-3 h, LEDT-6 h, and LEDT-24 h. Each subgroup was analyzed for muscle ATP content or fatigue at specified time after LEDT. The fatigue test was performed by mice repeatedly climbing an inclined ladder bearing a load of 150 % of body weight until exhaustion. LEDT used a cluster of LEDs with 20 red (630 ± 10 nm, 25 mW) and 20 infrared (850 ± 20 nm, 50 mW) delivering 80 mW/cm(2) for 90 s (7.2 J/cm(2)) applied to legs, gluteus, and lower back muscles. LEDT-6 h was the subgroup with the highest ATP content in soleus and gastrocnemius compared to all subgroups (P < 0.001). In addition, mice in LEDT-6 h group performed more repetitions in the fatigue test (P < 0.001) compared to all subgroups: LEDT-sham and LEDT-5 min (~600 %), LEDT-3 h (~200 %), and LEDT-24 h (~300 %). A high correlation between the fatigue test repetitions and the ATP content in soleus (r = 0.84) and gastrocnemius (r = 0.94) muscles was observed. LEDT increased ATP content in muscles and fatigue resistance in mice with a peak at 6 h. Although the time response in mice and humans is not the same, athletes might consider applying LEDT at 6 h before competition.